Rf fundamentals

RF Fundamentals
Author
S.Satish Babu
RF& Digital Wireless Systems Engineer
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Course Contents
Module – 1
Learning Basics of RF
RF and Transmission Line Fundamentals
RF and Transmission Line MeasurementsRF and Transmission Line Measurements
Problem Solving Assignments
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Course Contents
Module – 2
RF Communication Systems & Modulation
Techniques
Digital RF MeasurementsDigital RF Measurements
RF System Design Blocks
RF PCB Board Design Guidelines
EMC Shielding
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Course Contents
Module – 3
Wireless Technologies (ISM & Cellular)
Bluetooth
ZigbeeZigbee
WiFi
GSM/GPRS, WiMAX & LTE
Antenna Design Basics
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What is RF?
RF is anything related to “EM signals”.
RF is characterized by Frequency and Amplitude.
RF is synonymous with wireless and high frequency signals.
describing anything from AM radio 535KHz to computer LAN at
2.4GHz and 5.0GHZ – TO – 90GHz.
Electromagnetic Spectrum
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Electromagnetic Spectrum

RF Properties
All radio frequency signals have the following
properties:
Amplitude
FrequencyFrequency
Wavelength
Phase and
Polarization
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Frequency and Amplitude
Frequency: The number of times a signal goes through a complete
“up and down” cycle in one second of time – Measured in Hertz.
Amplitude: The difference between the maximum and minimum
value during one cycle – Measured in Volts. Related with strength or
power of the signal
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Wavelength
Wavelength: The wavelength of an RF signal is a function of the
signal’s frequency and it’s speed through space.
Wavelength: The distance a radio wave will travel
during one cycle is given by:
λ = c/f
λ is the wave length, in metersλ is the wave length, in meters
c is the speed of light, 3x10^8 m/s or 299793
m/s
The value of speed 299793 m/s is in a vacuum
without any kind of external influence, this is also
the speed of RF wave
f is the frequency in Hz @Satish Sura

Frequency
(f)
Wavelength(λ)
Graph Remark
900MHz λ = 299793/900 = 0.33m Long wavelength
Wavelength
2.4GHz
λ = 299793/2.4 =
0.125m
Medium
wavelength
5.0GHz
λ = 299793/5.0 =
0.06m
Short wavelength
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Wavelength
Also λ = V/f or
Where :
λ = Wavelength in meters
V = Velocity of radio wave ( speed of light)
f = Frequency of radio wave in Hertz
EnergyEnergy
E = hC / λ
Where:
E = Energy in Joules
h = Plank’s constant(6.63 x 10^34) joules/sec
C = Speed of Light
λ = wave length in meters
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Assignment -1
Calculate the wavelength for the following frequencies and
draw the graph.
Frequency (f) Wavelength(λ) Graph
433MHz ? ?
700MHz ? ?700MHz ? ?
2.1GHz ? ?
2.3GHz ? ?
3.6GHz ? ?
60GHz ? ?
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Phase
Phase is a method of expressing the relationship between the
amplitudes of two RF signals that have the same frequency. Phase
is measured in degrees .
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Polarization
A radio wave is actually made of up of two fields:
One electric, E – Plane
One magnetic, H – Plane
The sum of these two field is called the
“electromagnetic field”,
When energy is transferred back and forth from
one field to the other it is called “Oscillation”one field to the other it is called “Oscillation”
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RF Fundamentals – Scientific Notations
We use scientific notation that uses the power of ten to
multiply the values
milli (m) 1mV
micro(µ) 1µV
Kilo(k) 1kHz
mega(M) 1MHz
giga(G) 1GHz
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RF Fundamentals –Bandwidth
Bandwidth:It is the difference between
upper and lower frequencies in a
contentious set of frequencies. It is
typically measured in Hertz(Hz).
It is the width of the range of frequencies
that a signal occupies on a giventhat a signal occupies on a given
transmission medium.
Voice Transmission – 3KHz
FM Radio Broadcast – 200KHz
Analog TV broadcast – 6MHz
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The Radio Spectrum
Frequency(f) Wavelength(λ) Band Description
30-300Hz ELF Extremely low frequency
300-3000Hz VF Voice Frequency
3-30kHz 100-10km VLF Very Low Frequency
30-300khz 10-1km LF Low Frequency
0.3-3MHz 1-0.1km MF Medium Frequency
3-30MHz 100-10m HF High Frequency
30-300MHz 10-1m VHF Very High Frequency
300-3000MHz 100-10cm UHF Ultra -high Frequency
3-30GHz 10-1cm SHF Super-high Frequency
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30-300GHz 10-1mm EHF Extremely High Frequency (millimeter wave)

RF – Transmission Line
FundamentalsFundamentals
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RF – Transmission Lines
In RF circuits, RF energy has to be transported:
Over The Air
Cables
Transmission lines
As we transport energy, it gets lost due to
Resistance of the wire – lossy cable
Radiation (the energy radiates out of the wire – the
wire is acting as an antenna
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RF – Transmission Lines – Representation
Transmission lines include (physical construction):
Two parallel wires
Coaxial cable
Micro-strip line
Optical fiberOptical fiber
Waveguide (very high frequencies, very low loss, expensive)
etc.
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Types of Transmission Modes
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Electric Field – E, Magnetic Field – M
& Propagation
Electric and magnetic fields are orthogonal to one another, and
both are orthogonal to direction of propagation
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Example of TEM Mode
Electric field E is radial
Magnetic field H is azimuthal propagation
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Types of PCB Transmission Lines
Many of RF components require controlled impedance
transmission lines that will transport RF power to (or from) IC
pins on the PCB.
These transmission lines can be implemented on
exterior layer (top or bottom), or
Buried in an internal layer.Buried in an internal layer.
Guidelines for these transmission lines include relating to:
Microstrip,
Suspended Stripline,
Coplanar Waveguide (grounded),
Characteristic Impedance
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Microstrip
Microstrip transmission line consists of fixed-width metal routing
(the conductor), along with a solid unbroken ground plane located
directly underneath (on the adjacent layer).
A microstrip on Layer 1 (top metal) requires a solid ground plane
on Layer 2.on Layer 2.
The width of the routing, the thickness of the dielectric layer, and
the type of dielectric determine the characteristic impedance
(typically 50Ω or 75Ω).
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Suspended Stripline
Stripline transmission lines consists of a fixed-width routing on an
inner layer, with solid ground planes above and below the center
conductor.
The conductor can be located midway between the ground
planes.planes.
This is the appropriate method for RF routing on inner layers.
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Coplanar Waveguide (Grounded)
A coplanar waveguide provides for better isolation between
nearby RF lines, as well as other signal lines.
This medium consists of a center conductor with ground planes on
either side and below.
Via "fences" are recommended on both sides of a coplanarVia "fences" are recommended on both sides of a coplanar
waveguide.
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Characteristic Impedance
The outer laminated layers of typical PCBs often contain less glass
content than the core of the board.
For example, FR4 core is generally given as εR = 4.2, whereas the
outer laminate (prepreg) layers are typically εR = 3.8.
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Dielectric Constant of Materials
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RF Attenuation and Wave Propagation
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RF wave travelling in a Substrate
The RF wave travelling in a substrate (dielectric material)
do speed down to the amount of:
is the dielectric constant of substrate
Example: Calculate the speed of an RF wave in a PCBExample: Calculate the speed of an RF wave in a PCB
manufactured according to a basic FR4 spec.
Calculation: For a basic FR4 PCB material the dielectric
constant is 4.6
: 299792458/ 4.6 = 139.78*10^8 m/s
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Example1: Calculate the speed of an RF wave in a metal dielectric
capacitor of Si3N4 , SiO2 which is 2.7-4.2 and 3.5-9 respectively.
Example2: Calculate the speed of an RF wave in a Rogers
RO4003C PCB dielectric material which is 3.55.
Assignment -2
Example3: Calculate the speed of an RF wave in a Isola 370HR
PCB dielectric material which is 4.04.
Example4: What is the wave length transmitted from the
commercial frequency band-33 of 1900MHz in air/FR-4 Isola
370HR?
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RF & Transmission Line
MeasurementsMeasurements
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The logarithmic characteristic of
the dB, makes it very convenient
for expressing RF electrical power
USE OF dB in RF
for expressing RF electrical power
and power ratios.
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In the RF world the common standard is to refer powers to 1 mW
(0.001 Watts). Such power ratio, expressed in decibels, is called dBm.
RF – Power (dBm)
PdBm = 10log10 (PWatts / 1 mW)
RF – Power (dB)
Signal -1 has a power of P1 Watts
Signal-2 has a power of P2 WattsSignal-2 has a power of P2 Watts
PdB = 10log10 (P2 / P1)
Signal-1 with an RMS voltage of V1 across the load
Signal-2 with an RMS voltage of V2 across the load
VdB = 20 log10 (V2 / V1)
RF – Voltage
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Assignment – 3
Power unit: dBm, relative to 1mW
Power in dBm = 10 × log (power in watts/0.001 watts)
Example: 1 W is 10 × log 1000 = 30 dBm
Calculate power for 2W, 10W, 20W, 100mW, 10mW in dBm
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Signal to Noise Ratio—SNR Ratio
Signal to Noise Ratio or SNR is defined as the
ratio of the transmitted power to the noise power.
To calculate the SNR value, we add the Signal Value to the Noise
Value to get the SNR ratio.
A positive value of the SNR ratio is always better.A positive value of the SNR ratio is always better.
For example, say Signal value is -55dBm and Noise value is -95dBm.
The difference of Signal (-55dBm) + Noise (-95dBm) = 40db—This
means SNR is 40.
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RF – Gain & Loss
Gain
Is the term used to describe an increase in an RF signal
amplitude.
Loss
Loss describes a decrease in signal amplitude. Cable
resistance can cause loss of signal, since resistance coverts
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resistance can cause loss of signal, since resistance coverts
electrical signals to heat.

When the decibel figure is positive, the second signal is stronger
than the first one, and the power ratio is called gain.
When the decibel figure is negative, the second signal is weaker
than the first one, and the power ratio is called loss.
In amplifiers the gain, also called the amplification factor, in often
Gain & Loss Blocks of an RF System
In amplifiers the gain, also called the amplification factor, in often
expressed in decibels.
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Reflection Coefficient
A forward travelling wave when transmitted by a travelling media (substrate,
dielectric, wire, etc) and running to the load at the opposite end and at
junctions between two different dielectrics, a part of it gets reflected back to
the source. The quality of reflection caused at junctions of two different
impedances are specified by reflection coefficient.
The distance minimum to maximum of a wavelength is called quarter
wavelength represented by λ/4 and has 90degree phase shift.
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wavelength represented by λ/4 and has 90degree phase shift.

Return Loss
VSWR
VSWR is the voltage measured along the transmission line leading to an
antenna and is the ration of peak amplitude of a standing wave to the
minimum amplitude of standing wave
Decibel is the logarithmic expression of the ratio between the power,
voltage, or current of two signals.
Return Loss
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Some Useful Values
if a signal at the output of an amplifier is 100 times bigger then the
signal at its input, the amplifier has a gain of 100 or, using the definitionsignal at its input, the amplifier has a gain of 100 or, using the definition
of decibel, of 20 dB.
+3 dB means two times bigger
+10 dB means ten times bigger
- 3 dB means one half
-10 dB means one tenth
Rule of thumb:
Double the power = 3 dB increase
Half the power = 3 dB decrease
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RF – Definitions & Equations
dBm – relative to 1 mW
dBc – relative to carrier
dBi – related to Antenna
10mW = 10dBm, 0dBm = 1mW
-110dBm = 1E-11mW = 0.00001nW
For a 50 ohm load : -110dBm is 0.7uV,
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For a 50 ohm load : -110dBm is 0.7uV,
About dBm and W
Voltage Ratio aV = 20 log (P2/P1) [aV] = dB
Power Ratio aP = 10 log (P2/P1) [aP] = dB
Voltage Level V‘ = 20 log (V/1μV) [V‘] = dBμV
Power Level P‘ = 10 log (P/1mW) [P‘] = dBm
e.g. 25mW max. allowed radiated power in the EU SRD band
>> P‘ = 10 log (25mW/1mW) = 10 * 1,39794 dBm >> 14 dBm

RF & Logarithm co-existence
Since RF often deals with very large and very small multiplicative
ratios, we often work in logarithmic units.
Log units are useful because we add multiplicative values
0dBm+20dB-10dB+20dB = 30dBm = 1000mW = 1W
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dBm - Voltage Chat
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Power Budget & Receiver Power
Power Budget:The advantage of using decibels instead of Watts to
express the power of a signal along an RF chain is that, instead of
dividing or multiplying powers to take care of amplifications and
attenuations, we just add or subtract the gains and the losses expressed
in decibels.
Using amplification and attenuation factors and expressing the powers in
Watts, we obtain the value of the power at the receiver’s input in this way:
PReceiver = PTransmitter×1/AttenuationCable1×Amplification×1/ AttenuationCable2
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If we use dB to express the gains and the losses and dBm to
express the powers, the calculation becomes a simple
addition:
PReceiver = PTransmitter + LossCable1 + GainAmplifier + LossCable2
Power Budget & Receiver Power
The procedure of adding gains and losses to obtain the resulting
power for an RF chain is very common and is called Power Budget
Calculation
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Receiver Sensitivity: Minimum detectable input signal level for a given output
SNR (also called noise floor).
Also
Receiver sensitivity is the lowest power level at which the receiver can detect
an RF signal and demodulate data. Sensitivity is purely a receiver specification
and is independent of the transmitter.
Receiver Sensitivity
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The performance of any communication link depends on the quality of
the equipment being used.
Link budget is a way of quantifying the link performance.
The received power in an RF link is determined by three factors:
transmit power, transmitting antenna gain, and receiving antenna gain.
If that power, minus the free space loss of the link path, is greater than
Link Budget
If that power, minus the free space loss of the link path, is greater than
the minimum received signal level of the receiving radio, then a link is
possible.
The difference between the minimum received signal level and the
actual received power is called the link margin.
The link margin must be positive, and should be maximized (should be
at least 10dB or more for reliable links).
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Link Budget
Prx,Ptx – received and transmitted
power (dB)
Grx,Gtx – antenna gain (dBi)
L – path loss
Amisc – miscellaneous attenuation
P rx = P tx + G tx + G rx – L – A misc
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Receiver sensitivity can be got from spec of the device from OEM or from
Telecom standard’s manual ex: 3GPP , IEEE etc
From the fig site-to-site link being created across a distance of 200m with IEEE
802.11 bridge.
Output power of the device 100mW = 20bBm
Link Budget 20dBm – 3dB + 7dBi -83dB+7dBi – 3dB – (-94dBm)
Link Budget = 39dB
Conti…

Radio Range – Free Space Propagation
How much loss can we have between TX and RX?
Friis’ transmission equation for free space propagation:
or
Pt is the transmitted power, Pr is the received power
Gt is the transmitter, Gr is the receiver antenna gain
Lambda is the wavelength
D is the distance between transmitter and receiver
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Assignment – 4
Calculate the link budget for the following figure
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Assignment – 5
Calculate the link budget for the following figure
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Free Space Losses
Signal power getting diminished by geometric spreading of the wavefront,
commonly known as Free Space Loss.
loss in signal strength that occurs when an electromagnetic wave travels
over a line of sight path in free space.
The power of the signal is spread over a wave front, the area of which
increases as the distance from the transmitter increases. Therefore, the power
density diminishes.
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density diminishes.

FSPL, is an essential basic parameter for many RF calculations.
It can often be used as a first approximation for many short range
calculations.
it can be used as a first approximation for a number of areas where
there are few obstructions.
Free Space Path Loss (FSPL)
In a free space, signal decreases in a way that is inversely proportionalIn a free space, signal decreases in a way that is inversely proportional
to the square of the distance from the source of the radio signal and
it is given by
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Free Space Path Loss (FSPL) - Formula
or
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Where:
FSPL is the Free space path loss (meters)
d is the distance of the receiver from the transmitter (meters)
λ is the signal wavelength (meters)
f is the signal frequency (Hertz)
c is the speed of light in a vacuum (meters per second)

As we understand from our previous discussion, the RF comparisons
and measurements are performed in decibels. Accordingly it is very
convenient to express the free space path loss formula, FSPL, in terms
of decibels.
Free Space Path Loss (FSPL) – Logarithmic format
FSPL (dB) = 20 log10 (d) + 20 log10 (f) + K
Where:
d is the distance of the receiver from the transmitter (m)
f is the signal frequency (MHz)
K is Constant has a value of -147.55 for the units used for d
and f
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Assignment – 6
An RF Module operating at 2.480GHz frequency
and has RF-Power of 1mW placed at a distance of
150m. Calculate the FSPL in dB.
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Link Margin
LinkMargin = ReceivedPower - ReceiveSensitivity
FSPL (dB ) = TxPower - TxCableLoss – TxAntennaGain +
Fade Margin
FSPL (dB ) = TxPower - TxCableLoss – TxAntennaGain +
RxAntennaGain – RxCableLoss – RxSensitivity – Fade Margin
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Antennas will have certain amount of gain and this will affect the
overall signal level.
Any antenna gain will reduce the losses.
Effect of Antenna Gain on Path Loss
Where:
Gtx is the gain of the transmitter antenna relative to an isotropic source (dBi)
Grx is the gain of the receiver antenna relative to an isotropic source (dBi)
Path Loss (dB) = 20 log10(d) + 20 log10(f) + K – Gtx - Grx
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Scattering Parameters (S-Parameters)
An RF function is a two-port device with
– Characteristic impedance (Z0):
• Z0 = 50Ω for wireless communications devices
• Z0 = 75Ω for cable TV devices
– Gain and frequency characteristics
S-Parameters of an RF device
– S : input return loss or input reflection coefficient OR Forward– S11 : input return loss or input reflection coefficient OR Forward
Reflection (input match - impedance)
– S22 : output return loss or output reflection coefficient OR Reverse
Reflection (output match - impedance)
– S21 : gain or forward transmission coefficient OR Forward Transmission
(gain or loss)
– S12 : isolation or reverse transmission coefficient
(leakage or isolation)
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Impedance Smith Chart
This is an impedance chart transformed from rectangular Z.
Normalized to 50 ohms, the center = R50+J0 or Zo (perfect match).
For S11 or S22 (two-port), you get the complex impedance.
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Impedance Smith Chart
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Creating Matching Network
Various topologies can be used: L, C, RVarious topologies can be used: L, C, R
Avoid unwanted oscillations (L-C series/parallel)
Yield can be a factor in topology (sensitivity)
Use the fewest components (cost + efficient)
Sweep or tune component values to see S-parameters
Optimization: use to meet S-parameter specs (goals)
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Matching Circuit Definition
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Thank YouThank You
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RF Communication System
&&
Modulation Techniques
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RF Communication Systems
RF Communication systems is classified into three systems
Simplex communication system
Half – Duplex communication system
Full – Duplex communication system
Simplex System
A radio technology that allows only one-way communication fromA radio technology that allows only one-way communication from
a transmitter to a receiver
Example : FM radio, TV
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Half-Duplex System
Operation mode of a radio communication system in which each
end can transmit and receive, but not simultaneously.
The communication is bidirectional over the same frequency, but
unidirectional for the duration of a message.
These are TDD and TDMA systems.
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Full-Duplex System
Radio systems in which each end can transmit and receive
simultaneously
Typically two frequencies are used to set up the communication
channel.
Each frequency is used solely for either transmitting or receiving.
Applies to Frequency Division Duplex (FDD) systems
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Applies to Frequency Division Duplex (FDD) systems

The Modern Wireless Standards
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Trends of Wireless Communication System
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Basic Wireless Communication System
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Modulation and Methods
Modulation: The process of superimposing a low frequency signal
onto a high frequency signal is called Modulation.
Three types of modulation schemes are available.
Amplitude Modulation – The amplitude of the carrier varies
Frequency Modulation – The frequency of the carrier variesFrequency Modulation – The frequency of the carrier varies
Phase Modulation – The phase of the carrier varies
Modulation of Digital Signal is known as Shift Keying
Amplitude Shift Keying
Frequency Shift Keying
Phase Shift Keying
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Amplitude Shift Keying (ASK):
Pros: Simple
Cons: Susceptible to noise
Ex: Many legacy wireless systems, e.g. AMR
Digital Modulation
Frequency Shift Keying (FSK):
Pros: less susceptible to noise
Cons: theoretically requires larger bandwidth/bit than ASKCons: theoretically requires larger bandwidth/bit than ASK
Popular in modern systems
Gaussian FSK (GFSK), e.g. used in Bluetooth, more
bandwidth efficient
Phase Shift Keying (PSK):
Pros: Less susceptible to noise, Bandwidth efficient
Cons: Require synchronization in frequency and phase
complicates receivers and transmitters
Example: IEEE 802.15.4 / ZigBee
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Bluetooth Modulation Techniques, Freq, Carrier & Power
Bluetooth frequencies are all located within the 2.4 GHz ISM band.
The ISM band typically extends from 2400 MHz to 2483.5 MHz (i.e. 2.4000 - 2.4835
GHz).
The Bluetooth channels are spaced 1 MHz apart.
Bluetooth version 1 adopts GFSK - 720Kbps
Bluetooth version 2 adopts Enhanced Data Rate (EDR) of π/4 DQPSK(2Mbps) and
8DPSK(3Mbps) with improved data rates.8DPSK(3Mbps) with improved data rates.
Bluetooth version 3 is not through modulation technique, but by working with an
IEEE 802.11g physical layer data rates of 25Mbps can be achieved.
Bluetooth class 1 is designed for 100m & 20dBm, class 2 for 10m & 6 dBm, class 3
for 10cm and 0dBm. π/4 DQPSK 8DPSKGFSK
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BPSK,QPSK, QAM modulation Scheme
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Spread Spectrum Systems
Data sent using spread spectrum is intentionally spread
over a wide frequency range
Appears as noise, so it is difficult to detect and jam
Resistant to noise and interference thus increasing the
probability that the signal will be received correctly
Unlikely to interfere with other signals even if they are
transmitted on the same frequency
2 types of Spread Spectrum common in ISM bands:
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2 types of Spread Spectrum common in ISM bands:
Direct Sequence Spread Spectrum (DSSS)
Frequency Hopping Spread Spectrum (FHSS)

General Model of a Spread Spectrum System
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Direct Sequence Spread Spectrum(DSSS)
Each bit represented by multiple bits using spreading code
Spreading code spreads signal across wider frequency band
Good resistance against interferers
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Frequency Hopping Spread Spectrum (FHSS)
Signal broadcast over a seemingly random series of frequencies
Receiver hops between frequencies in sync with transmitter
Jamming on one frequency affects only a few bits
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DSSS – BPSK Example
DSSS-BPSK – Example
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DSSS Example

A major disadvantage with fixed modulation (non-adaptive) on channels with
varying signal-to-noise ratio (SNR) is that the bit-error-rate (BER) performance.
Adaptive Modulation(QPSK,QAM)
Most applications require a certain maximum BER.
An adaptive modulation scheme, is designed to have a BER which is constant for
all channel SNRs.
The spectral efficiency of the fixed modulation is constant.
The spectral efficiency will increase with increasing channel SNRs for adaptive
scheme.
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scheme.
Thus, the adaptive link becomes much more efficient for data transmission.
Applications: WiFi, LTE and high data hungry schemes.

802.15.4 – Zigbee Modulation Techniques
802.15.4 was developed with lower data rate, simple connectivity and low power
battery application in mind.
802.15.4 standard specifies communication can occur in the 868-868.8 MHz, the
902-928 MHz or the 2.400-2.4835 GHz Industrial Scientific and Medical (ISM) bands.
The 2.4 GHz band is more popular as it is open in most of the countries worldwide.
The 802.15.4 standard specifies, a maximum over-the-air data rate of 250 kbps.
At 2.4 GHz, 802.15.4 specifies the use of Direct Sequence Spread Spectrum(DSSS)At 2.4 GHz, 802.15.4 specifies the use of Direct Sequence Spread Spectrum(DSSS)
and uses an Offset Quadrature Phase Shift Keying (O-QPSK) with half-sine pulse
shaping to modulate the RF carrier.
802.15.4 standard allows for communication in a point-to-point or a point-to-
multipoint configuration.
IEEE 802.15.4 has 16 channels 11 through 26 between 2.4 GHz and 2.4835 GHz each
with a bandwidth of 2 MHz and an inter channel spacing of 5 MHz
Typical distance of 70m-300m and 30ms network joining time.
Conti….@Satish Sura

802.15.4 – Zigbee Modulation Techniques
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WiFi modulation Scheme
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Cellular LTE Modulation Scheme
LTE takes advantage of OFDMA, a multi-carrier
scheme that allocates radio resources to multiple
users. OFDMA uses Orthogonal Frequency Division
Multiplexing (OFDM).
OFDM splits the carrier frequency bandwidth
into many small subcarriers spaced at 15 kHz, andinto many small subcarriers spaced at 15 kHz, and
then modulates each individual subcarrier using
the QPSK, 16-QAM, or 64 – QAM digital
modulation formats.
OFDMA assigns each user the bandwidth
needed for their transmission.
Unassigned subcarriers are off, thus reducing
power consumption and interference. Conti…. @Satish Sura

OFDMA uses OFDM
OFDMA: The scheduling and assignment of
resources that makes OFDMA distinctive.
In OFDM, the entire bandwidth belongs to a
single user for a period of time.
single user for a period of time.
In OFDMA, multiple users are sharing the
bandwidth at each point in time.
Conti….@Satish Sura

SC-FDMA
In the uplink, LTE uses a pre-coded version of
OFDM called SC-FDMA.
SC-FDMA has a lower PAPR (Peak-to-Average
Power Ratio) than OFDM.
This lower PAPR reduces battery power
consumption, requires a simpler amplifier design
consumption, requires a simpler amplifier design
and improves uplink coverage and cell-edge
performance.
In SC-FDMA, data spreads across multiple
subcarriers, unlike OFDMA where each subcarrier
transports unique data.
The need for a complex receiver makes SC-
FDMA unacceptable for the downlink. Conti…. @Satish Sura

LTE Adaptive Modulation and Coding (AMC)
Adaptive Modulation and Coding refers to the ability of the
network to determine the modulation type and the coding rate
dynamically based on the current RF channel conditions
reported by the UE.
The RF digital modulation used to transport the information
is QPSK, 16-QAM, and 64-QAM.
Each dot represents a possible symbol.
In the QPSK case, there are four possible symbol states andIn the QPSK case, there are four possible symbol states and
each symbol carries two bits (2^1) of information. In 16-QAM,
there are 16 symbol states. Each 16-QAM symbol carries 4 bits
(2^2) . In 64-QAM, there are 64 symbol states. Each 64-QAM
symbol carries 6 bits (2^6) .
Higher-order modulation is more sensitive to poor channel
conditions than the lower-order modulation because the
detector in the receiver must resolve smaller differences as the
constellations become more dense. @Satish Sura

Digital RF Measurements
@Satish Sura

Phase Noise in RF @Satish Sura
In a receiver, the phase noise of the LO can mix with a large
interfering signal from a neighboring channel and swamp out the
signal from the desired channel even though most of the power in
the interfering IF is removed by the IF filter. This process is referred to
as reciprocal mixing.

Phase Noise in RF
Phase noise or phase jitter is of particular
importance, because it reduces the signal quality
and hence increases the error rate of the
communications link.
Phase noise is an important aspect of frequency
synthesizer and signal generator design, and levels
of phase noise must be considered at the earliest
stages of design of these items.
@Satish Sura
stages of design of these items.
In a receive chain, the fact that the LO is
not a perfect delta function means that
there is a continuum of LO’s that can mix
with interfering signals and produce energy
at the same IF. Here we observe an
adjacent channel signal mixing with the
“skirt” of the LO and falling on top of the a
weak IF signal from the desired channel. Phase Noise in Rx Chain

Noise Figure
Where PO is the total output noise
@Satish Sura
Where PO is the total output noise
power, PL is the output noise
power that results from
noise generated by the load at the
output frequency, and PS is the
output noise power that results
from noise generated by the
source at the input frequency.

How good are the transmitters making efficient use of the RF spectrum?
Occupied Band Width (OBW) –Narrow Band
OBW = Occupied Band Width
Occupied Bandwidth (OBW) is a common measurement performed on
radio transmitters. This measurement calculates the bandwidth containing
the total integrated power occupied in a given signal bandwidth.
•% Integrated Power Method: The occupied frequency bandwidth is
calculated as the bandwidth containing the specified percentage of thecalculated as the bandwidth containing the specified percentage of the
transmitted power.
•> dBc Method: The occupied frequency bandwidth is defined as the
bandwidth between the upper and lower frequency points at which the
signal level is a desired number of dB below the peak carrier level.
@Satish Sura

ACP is a measure of the nonlinear characteristics of a device under
test (DUT) and indicates the amount of spectral regrowth occurring in
adjacent channels.
Measured using built-in function of spectrum analyzer
Narrowband Transmitter
Adjacent Channel Power (ACP)
Low phase noise key parameter for low ACP
ETSI: Absolute ACP requirement (dBm), ARIB: Relative (dBc)
@Satish Sura

How good are the receiver at handling interferers at same frequency?
Co-channel rejection
Test method: Modulated Interferer
Wanted signal 3 dB above sensitivity limit
Receiver, Co-channel Rejection
@Satish Sura

Receiver Selectivity
Selectivity is a measure of the performance of a radio receiver to respond
only to the radio signal it is tuned to (such as a radio station) and reject other
signals nearby infrequency, such as another broadcast on an adjacent channel.
Selectivity is usually measured as a ratio in decibels (dBs), comparing
the signal strength received against that of a similar signal on
another frequency. If the signal is at the adjacent channel of the selected
signal, this measurement is also known as adjacent-channel rejection (ACR)signal, this measurement is also known as adjacent-channel rejection (ACR)
or Adjacent-channel Selectivity (ACS) or Adjacent Channel Rejection Ratio
(ACRR)
@Satish Sura

Receiver, Blocking/desensitization
Blocking/desensitization is a measure of how good a receiver is
to reject an interferer “far away” (out of band) from the wanted
signal
Measured the same way as selectivity, but the interfering signalMeasured the same way as selectivity, but the interfering signal
is usually not modulated
Blocking can be further improved with a SAW filter
@Satish Sura

Image Rejection
No image rejection
Image rejection
@Satish Sura

How to achieve good RF sensitivity?
Introduce high gain in front of the
receiver
External LNA needed
Poor linearity (IP3)
Poor blocking/selectivity
“Removes” the losses in the“Removes” the losses in the
SAW filter
Lower noise bandwidth
(narrowband)
Blocking/linearity not
changed
Good selectivity
Good frequency control
needed
@Satish Sura

ERROR VECTOR MAGNITUDE (EVM)
Transmission modulation accuracy is measured using error vector
magnitude (EVM).
The magnitude of the phase difference as a function of time
between an ideal reference signal and the measured transmitted
signal.
EVM is a measure that can beEVM is a measure that can be
used to quantify the
performance of a digital radio
transmitter
@Satish Sura

Adjacent Channel Power Ratio (ACPR)
The adjacent channel power ratio of a wireless
communication system is the integrated power in the carrier
channel relative to the adjacent channel.
@Satish Sura

Bit Error Rate (BER)
Bit error rate is a form of measurement used for digital
systems.
As the signal level falls or the link quality degrades, so
the number of errors in the transmission - bit errors -
increases.increases.
@Satish Sura

RF System Design BlocksRF System Design Blocks
@Satish Sura

Basic Building Blocks of an RF System
RF-IC
Transmitter
Receiver
Transceiver
Baseband Processor
ADC & DAC
SOC
Crystal
Reference frequency for
the LO and the carrier
frequency
Clock & clock buffers
Balun
Balanced to unbalanced
Converts a differential
signal to a single-ended
signal or vice versa
Filter
Used if needed to pass
regulatory requirements /
Antenna
Matching
regulatory requirements /
improve selectivity
Antenna
Basic Transmitter Circuit
Modern transmitters typically use
fractional-N synthesizers.
For angle modulation like FSK, MSK, O-
QPSK, the synthesizer frequency is
adjusted.
For amplitude modulation like OOK and
ASK, the amplifier level is adjusted@Satish Sura

Receiver Architecture
Converts the incoming signal
to an Intermediate Frequency
(IF) signal and performs:
Carrier frequency tuning –
selects desired signal.
Receiver Block Diagram
Super Heterodyne Receiver
selects desired signal.
Filtering – separates signal
from other modulated signals
picked up.
Amplification – compensates
for transmission losses in the
signal path
Super Heterodyne Receiver
@Satish Sura

Image Rejection Receiver Architecture
Image rejection receiver –The image frequency is an undesired
input frequency that is capable of producing the same intermediate
frequency (IF) as the desired input frequency produces. Ex: AGC
using ADC and filters.
@Satish Sura

Transceiver Architecture
Super Heterodyne Transceiver block diagram
The Transceivers are highly integrated, low power, and high performance
IC’s for operation and application specific bands. These are designed with
emphasis on flexibility, robustness, ease of use, and low current
consumption.
The transmitter path of the IC’s are based on a direct closed-loop VCO
modulation scheme using a low noise fractional-N RF frequency synthesizer.
These have the characteristics of reducing spurious emission and pulling
@Satish Sura
These have the characteristics of reducing spurious emission and pulling
effects.

Basic Building Blocks of Transceiver IC
Simple Processor
ADC & DAC
Transmitter
Receiver
Clock Generator(PLL &
REF Clock
Modulator
PAPA
LNA
Filters (BPF)
Amplifiers
Switches
Fractional N Synthesizer
Automatic Gain
Controller(AGC)
@Satish Sura

Understanding the Features of Transceiver IC
@Satish Sura

Balun and Matching Circuit
@Satish Sura

Extending the Operating Range of an RF System
Increase the Output power
Add an external Power Amplifier (PA)
Increase the sensitivity
Add an external Low Noise Amplifier (LNA)
Increase both output power and sensitivity
Add PA and LNA
Use high gain antennas @Satish SuraUse high gain antennas
Regulatory requirements need to be followed
@Satish Sura

Signal from TXRX Switch pin level shifted and buffered
CMOS and GaAs FET switches assures low RX current
Simpler control without external LNA
A TDMA Switch
Adding an External PA to Increase Operating Range
TRX
@Satish Sura

Adding an External PA/LNA to the Operating Range
Along With Duplexer
An FDD Communication System
@Satish Sura

120 dB link budget at 433 MHz gives approximately 2000 meters
Rule of Thumb:
6 dB improvement ~ twice the distance
Double the frequency ~ half the range – 433 MHz longer range than
868 MHz
Factors
RF Range and Important Factors
Factors
Antenna (gain, sensitivity to body effects etc.)
Sensitivity
Output power
Radio pollution (selectivity, blocking, IP3)
Environment (Line of sight, obstructions, reflections, multipath
fading)
@Satish Sura

Bandpass Filters @Satish Sura
A bandpass signal is a signal containing a band of frequencies not adjacent to
zero frequency, such as a signal that comes out of a bandpass filter.
An ideal bandpass filter would have a completely flat passband (e.g. with no
gain/attenuation throughout) and would completely attenuate all frequencies
outside the passband.
In practice, no bandpass filter is ideal.
there is a region just outside the intended passband where frequencies are
attenuated, but not rejected is called filter roll-off.

RF PCB Board Design
GuidelinesGuidelines
@Satish Sura

Transmission Line Bends and Corner Compensation
When transmission lines are required to bend (change direction) due to
routing constraints, use a bend radius that is at least 3 times the center
conductor width.
Bend Radius ≥ 3 × (Line Width)
This will minimize any characteristic impedance changes moving through
the bend.
In cases where a gradually curved bend is not possible, the transmissionIn cases where a gradually curved bend is not possible, the transmission
line can undergo a right-angle bend (noncurved).
The optimum microstrip right-angle miter is given by the formula of
Douville and James:
Where M is the fraction (%) of the miter. and is subject to the constraint
that w/h ≥ 0.25.
@Satish Sura

Transmission Line Bends and Corner Compensation
@Satish Sura

Layer Changes for Transmission Lines
When layout constraints required that a transmission line move to
a different layer, it is recommended that at least two via holes be
used for each transition to minimize the via inductance loading.
A pair of vias will effectively cut the transition inductance by 50%
The largest diameter via should be utilized that is compatible with
the transmission line width.
If space does not permit the use of larger vias, then two or three
small size transition vias.
@Satish Sura

Signal Line Isolation
RF Transmission Lines:
Lines should be kept as far apart as possible to avoid coupling.
Signal lines that will carry high power levels should be kept away
from all other lines whenever possible.
An isolation better than approximately -45dB between RF lines is
recommended.recommended.
High-Speed Digital Signal Lines:
These lines should be routed separately on a different layer than the
RF signal lines, to prevent coupling.
Digital noise (from clocks, PLLs, etc.) can couple onto RF signal lines,
and these can be modulated onto RF carriers.
In some cases digital noise can be up/down-converted.
@Satish Sura

VCC/Power Lines:
These should be routed on a dedicated layer if possible.
Power line isolation from the rest of circuit is mandatory.
Adequate decoupling/bypass capacitors should be provided at the
main VCC distribution node, as well as at VCC branches.
The choice of the bypass capacitances must be made based on the
Signal Line Isolation
The choice of the bypass capacitances must be made based on the
overall frequency response of the RF IC, and the expected frequency
distribution nature of any digital noise from clocks and PLLs.
These lines should be separated from any RF lines that will transmit
large amounts of RF power.
@Satish Sura

Ground Planes
The recommended practice is to use a solid (continuous) ground plane on
Layer 2 assuming Layer 1 is used for the RF components and transmission
lines.
For striplines and offset striplines, ground planes above and below the
center conductor are required.
These planes must not be shared or assigned to signal or power nets, but
must be uniquely allocated to ground.must be uniquely allocated to ground.
Partial ground planes on a layer, sometimes required by design constraints,
must underlie all RF components and transmission lines.
Ground planes must not be broken under transmission line routing.
Ground vias between layers should be added liberally throughout the RF
portion of the PCB. This helps prevent accrual of parasitic ground inductance
due to ground-current return paths.
The vias also help to prevent cross-coupling from RF and other signal lines
across the PCB. @Satish Sura

Consideration on Bias and Ground Layers
While designing PCB stakup, the layers assigned to system bias (DC
supply) and ground must be considered in terms of the return current
for the components.
The general guidance is to not have signals routed on layers
between the bias layer and the ground layer.
IncorrectIncorrect
Layer Assignment
Better
Layer Assignment
@Satish Sura

Power (Bias) Routing and Supply Decoupling
A common practice is to use a "star" configuration for the power-
supply routes, if a component has several supply connections.
A larger decoupling capacitor (tens of µFds) is mounted at the
"root" of the star, and smaller capacitors at each of the star branches.
Choose the value of the capacitors depends on the operating
frequency range of the RF IC.frequency range of the RF IC.
The "star" configuration avoids
long ground return paths that
would result if all the pins
connected to the same bias net
were connected in series.
@Satish Sura

Decoupling or Bypass Capacitors
Real capacitors have limited effective frequency ranges due to their
self-resonant frequency (SRF).
Above the SRF, the capacitor is inductive, and therefore will not
perform the decoupling or bypass function.
When broadband decoupling is required, standard practice is to use
several capacitors of increasing size (capacitance), all connected in
parallel.parallel.
@Satish Sura

Bypass Capacitor Layout Considerations
Since the supply lines must be AC ground, it is important to minimize
the parasitic inductance added to the AC ground return path.
the vias connecting the VCC pad on the top layer to the inner power
plane (layer) potentially impede the AC ground current return, forcing
a longer return path with resulting higher parasitic inductance.
In this alternate configuration, the AC ground return paths are not
blocked by the power-plane vias. Generally this configuration requiresblocked by the power-plane vias. Generally this configuration requires
somewhat more PCB area.
@Satish Sura

Grounding of Shunt-Connected Components
For shunt-connected (grounded) components (such as power-
supply decoupling capacitors), the recommended practice is to use
at least two grounding vias for each component. This reduces the
effect of via parasitic inductance.
@Satish Sura

IC Ground Plane ("Paddle")
Most ICs require a solid ground plane on the component layer (top
or bottom of PCB) directly underneath the component. This ground
plane will carry DC and RF return currents through the PCB to the
assigned ground plane.
"ground paddle" is to provide a thermal heatsink, so the paddle
should include the maximum number of thru vias that are allowed byshould include the maximum number of thru vias that are allowed by
the PCB design rules.
The maximum number of vias that can be accommodated by other
layout considerations should be used.
These vias are ideally thru-vias and must be plated.
the vias should be filled with thermally
conductive paste to enhance the heatsink.
@Satish Sura

PCB Layout – Rule of Thumb for RF
PCB Layout: Rules of thumb for RF Layout
Keep via inductance as low as possible.
Usually means larger holes or multiple parallel
holes)
Keep top ground continuous as possible.
Similarly for bottom ground.
Make the number of return paths equal forMake the number of return paths equal for
both digital and RF
Current flow is always through least
impedance path. Therefore digital signals
should not find a lower impedance path
through the RF sections.
Compact RF paths are better, but observe
good RF isolation between pads and or traces.
@Satish Sura

PCB Layout: Do’s and Don’ts of RF Layout
Keep copper layer continuous for grounds. Keep connections to supply
layers short
Use IC packages which have higher self-resonance and lower
package parasitic components.
Use the chips star point ground return
Avoid ground loops at the component level and or signal trace.
Use vias to move the PCB self resonance higher than signal frequenciesUse vias to move the PCB self resonance higher than signal frequencies
Keep trace and components spacing nothing less than 12 mils
Keep via holes large at least 14.5 mils
Separate high speed signals (e.g. clock signals) from low speed signals,
digital from analog. Placement is critical to keep return paths free of
mixed signals.
Route digital signals traces so antenna field lines are not in parallel to
lines of magnetic fields.
Keep traces length runs under a ¼ wavelength when possible. @Satish Sura

RF Design Guidelines For Meeting Regulatory
Requirements
DC supply lines to the IC should have decoupling capacitors close to the IC.
The printed circuit board (PCB) should have a solid ground plane in the RF
section. Avoid cutouts or slots in this ground layer. Such slots can act as
antennas and generate unwanted emissions.
Study the harmonics specification of the IC and use a low-pass or band-passStudy the harmonics specification of the IC and use a low-pass or band-pass
filter in the transmit path to suppress the harmonics sufficiently. If possible,
chose the transmit frequency such that the harmonics do not fall into
restricted bands.
In most cases shielding may be necessary to reduce spurious emissions. If
that is the case, filter all lines leaving the shielded case with decoupling
capacitors close to the shield inside the shielding case.
Conti ..@Satish Sura

RF Design Guidelines For Meeting
Regulatory Requirements
Chose proper values of decoupling capacitors. A large capacitance
value is not always the best. Good results are achieved with capacitors
which are in series resonance with their parasitic inductance at the RF
frequency that needs to be filtered out.
The loop bandwidth of the PLL oscillator can have an impact on the
range of modulation bandwidth or adjacent channel power of a
transmitter and the adjacent channel rejection of a receiver. Design the
PLL loop filter carefully according to the data rate requirements.
In case of battery driven equipment, use a brownout detector to switch
off the transmitter before the PLL looses lock due to a low battery voltage.
@Satish Sura

EMI, RFI, and Shielding
EMC is the ability of a device, unit of equipment, or system to
function satisfactorily in its electromagnetic environment without
introducing intolerable electromagnetic disturbances to anything in
that environment.
The equipment under design should neither produce spurious
signals, nor should it be vulnerable to out-of-band external signals.signals, nor should it be vulnerable to out-of-band external signals.
EMI/RFI can be fundamentally broken down into
Source
Path
Receiver
@Satish Sura

EMC Shielding
EMI Coupling Paths
Interference due to conduction (common-impedance)
Interference due to capacitive or inductive coupling (near-field
interference)
Electromagnetic radiation (far-field interference)
Noise Coupling Mechanisms
Impedance mismatches and discontinuitiesImpedance mismatches and discontinuities
Common-mode impedance mismatches → Differential Signals
Capacitively Coupled (Electric Field Interference)
dV/dt → Mutual Capacitance → Noise Current
(Example: 1V/ns produces 1mA/pF)
Inductively Coupled (Magnetic Field)
di/dt → Mutual Inductance → Noise Voltage
(Example: 1mA/ns produces 1mV/nH) @Satish Sura

Reducing Common-Impedance Noise
EMC Shielding
Common-impedance noise
Decouple op amp power leads at LF and HF
Reduce common-impedance
Eliminate shared paths
Techniques
Low impedance electrolytic (LF) and local low inductance
(HF) bypasses
Low impedance electrolytic (LF) and local low inductance
(HF) bypasses
Use ground and power planes
Optimize system design
@Satish Sura

EMC Shielding
Noise Induced by Near-Field Interference “Crosstalk”
Reducing Capacitance-Coupled Noise
Reduce Level of High dV/dt Noise Sources
Use Proper Grounding Schemes for Cable Shields
Reduce Stray CapacitanceReduce Stray Capacitance
Equalize Input Lead Lengths
Keep Traces Short
Use Signal-Ground Signal-Routing Schemes
Use Grounded Conductive Faraday Shields to Protect Against Electric
Fields
Conti….
@Satish Sura

EMC Shielding
Noise Induced by Near-Field Interference “Crosstalk”
Reducing Magnetically-Coupled Noise
Careful Routing of Wiring
Use Conductive Screens for HF Magnetic Shields
Use High Permeability Shields for LF Magnetic Fields (mu-Metal)
Reduce Loop Area of ReceiverReduce Loop Area of Receiver
Twisted Pair Wiring
Physical Wire Placement
Orientation of Circuit to Interference
Reduce Noise Sources
Twisted Pair Wiring
Driven Shields
@Satish Sura

Reducing System Susceptibility To EMI
Always Assume That Interference Exists!
Use Conducting Enclosures Against Electric and HF Magnetic
Fields
Use mu-Metal Enclosures Against LF Magnetic Fields
Implement Cable Shields Effectively
Use Feedthrough Capacitors and Packaged PI Filters
EMC Shielding
Use Feedthrough Capacitors and Packaged PI Filters
@Satish Sura

Board level RF Shielding
@Satish Sura

EMI/EMC Design Considerations
Critical circuits (i.e. clock circuits, clock driver, etc.) and functions should
be grouped together, providing the shortest trace lengths between
components.
For conducted noise issues, the use of ferrite chokes and proper signal
line layout can prevent a host of issues.
Basic formula for RF emissions: E = 1.316 AIF2 /(DS)
EMC Shielding
Basic formula for RF emissions: E = 1.316 AIF2 /(DS)
where:
E = microvolts / meter
A = radiating loop area in cm2
I = current in amps
F = frequency in MHz
D = measurement distance in meters
S = shielding effectiveness ratio
@Satish Sura

The most common cause of failures are caused by
excessive loop area.
High current and high frequency circuits should have the
least minimum loop area.
EMC Shielding
EMI/EMC Design Considerations
least minimum loop area.
Proper Isolation between the groups preventing noise
source imposed over the other.
Use of more fine pitch components on a PCB
Thinner solder paste thicknesses to prevent shorts or
bridges @Satish Sura

EMC Shielding
Board Level Shielding
Removable Pickup Bridge Shielding
@Satish Sura

EMC Shielding
Recover with lid removable Board level shielding
@Satish Sura

EMC Shielding
@Satish Sura

RF – Technologies
Bluetooth, ZigBee, WiFiBluetooth, ZigBee, WiFi
& Cellular
Author
S.Satish Babu
RF& Digital Wireless Systems Architect@Satish Sura

Discussion Points
wireless network technology options
Concept of ISM frequency band
Comparison between different wireless technologies
(PHY and MAC layers)
BluetoothBluetooth
ZigBee
WiFi
WiMAX
LTE
@Satish Sura

wireless network technology Trends
Network definition Standard Given Name
Wireless personal area network
(WPAN) IEEE 802.15.1 Bluetooth
Low-rate WPAN (LRWPAN) IEEE 802.15.4 ZigBee
Wireless local area network (WLAN) IEEE 802.11 WiFi
Wireless metropolitan area network
(WMAN) IEEE 802.16 WiMAX
Long Term Evolution (LTE)
IMT- Advanced
/3GPP LTE Advanced
@Satish Sura

ISM frequency bands
ISM (Industrial, Scientific and Medical) frequency bands:
• 900 MHz band (902 … 928 MHz)
• 2.4 GHz band (2.4 … 2.4835 GHz)
• 5.8 GHz band (5.725 … 5.850 GHz)
• 60 GHz band• 60 GHz band
• …
Anyone is allowed to use radio equipment for transmitting in
these bands (provided specific transmission power limits are
not exceeded) without obtaining a license.
@Satish Sura

ISM frequency band at 2.4 GHz
The ISM band at 2.4 GHz can be used by as long as:
Transmitters using FH (Frequency Hopping) technology:
Total transmission power < 100 mW
Power density < 100 mW / 100 kHzPower density < 100 mW / 100 kHz
Transmitters using DSSS technology:
Total transmission power < 100 mW
Power density < 10 mW / 1 MHz
@Satish Sura

Multiplexing / Multiple Access /
Duplexing
Multiplexing / multiple access
Signals to/from different users share a common channel
using time division methods (TDMA), frequency division
methods (FDMA), code division methods (CDMA), or randommethods (FDMA), code division methods (CDMA), or random
access methods (CSMA).
Duplexing:
The signals moving between two elements in opposite
directions can be separated using time division duplexing
(TDD) or frequency division duplexing (FDD). In the case of
CSMA, duplexing is not relevant. @Satish Sura

Wireless Personal Area Network (WPAN) » 10m
ISM band: 2.4 … 2.4835 GHz
Bluetooth Special Interest Group (SIG)
@Satish Sura

Low-rate WPAN (LR-WPAN) » 10m
ISM band: 2.4 … 2.4835 GHz
ZigBee Alliance @Satish Sura

Wireless Fidelity (WiFi) » 100m
The WiFi certification program of the Wireless Ethernet Compatibility
Alliance (WECA) addresses compatibility of IEEE 802.11 equipment
WiFi ensures interoperability of equipment from different
vendors. @Satish Sura

Wireless Metropolitan Area Network
(WMAN) » 5km
Various frequency bands WiMAX, LTE-Advanced
@Satish Sura

Maximum Channel Data Rates
Network Maximum data rate
IEEE 802.15.1 WPAN
(Bluetooth)
1 Mbit/s (Bluetooth v. 1.2)
24 Mbit/s (Bluetooth v. 4.0 for IoT)
IEEE 802.15.4 LRWPAN
(ZigBee)
250 kbit/s (ZigBee)
IEEE 802.11 WLAN 11 Mbit/s (802.11b)
Test
IEEE 802.11 WLAN
(WiFi)
11 Mbit/s (802.11b)
54 Mbit/s (802.11g)
1 Gpbs (802.11ac/n)
IEEE 802.16 WMAN
(WiMAX)
134 Mbps (WiMAX)
LTE-Advanced DL 3 Gbps, UL 1.5 Gbps;
30 bps/Hz spectral efficiency
@Satish Sura

Modulation/Signal Spreading
Test
Network Modulation / spreading method
IEEE 802.15.1 WPAN
(Bluetooth)
Gaussian FSK / FHSS
IEEE 802.15.4 LRWPAN
(ZigBee)
Offset-QPSK / DSSS
IEEE 802.11 WLAN DQPSK / DSSS (802.11b)
Test
IEEE 802.11 WLAN
(WiFi)
DQPSK / DSSS (802.11b)
64-QAM / OFDM (802.11g)
IEEE 802.16 WMAN
(WiMAX)
128-QAM / single carrier
64-QAM / OFDM
LTE-Advanced 64QAM / single carrier
64QAM / OFDM
@Satish Sura

BLUETOOTHBLUETOOTH
@Satish Sura

IEEE definition of WPAN
Wireless personal area networks (WPANs) are used to
convey information over short distances among a private,
intimate group of participant devices.
Unlike a wireless local area network (WLAN), aUnlike a wireless local area network (WLAN), a
connection made through a WPAN involves little or no
infrastructure or direct connectivity to the world outside the
link. This allows small, power-efficient, inexpensive solutions
to be implemented for a wide range of devices.
@Satish Sura

Bluetooth L IEEE 802.15.1
A widely used WPAN technology is known as Bluetooth
(version 1.2 - version 4.0)
The IEEE 802.15.1 standard specifies the architecture
and operation of Bluetooth devices, but only as far asand operation of Bluetooth devices, but only as far as
physical layer and medium access control (MAC) layer
operation is concerned (the core system architecture).
Higher protocol layers and applications defined in usage
profiles are standardised by the Bluetooth SIG.
@Satish Sura

Piconets
Bluetooth enabled electronic
devices connect and
communicate wirelessly
through short-range, ad-hoc
networks known as piconets.
Up to 8 devices
in one piconet
(1 master and 7
slave devices).
Max range 10 m.
networks known as piconets.
Piconets are established dynamically and automatically as
Bluetooth enabled devices enter and leave radio proximity.
ad hoc => no base station
@Satish Sura

Piconet operation
The piconet master is a device in a piconet whose clock
and device address are used to define the piconet physical
channel characteristics. All other devices in the piconet are
called piconet slaves.
At any given time, data can be transferred between theAt any given time, data can be transferred between the
master and one slave. The master switches rapidly from
slave to slave in a round-robin fashion.
Any device may switch the master/slave role at any time.
@Satish Sura

Bluetooth radio and baseband parameters
Topology Up to 7 simultaneous links
Modulation Gaussian filtered FSK
RF bandwidth 220 kHz (-3 dB), 1 MHz (-20 dB)
RF band 2.4 GHz ISM frequency band
RF carriers 79 (23 as reduced option)
Carrier spacing 1 MHz
Access method FHSS-TDD-TDMA
Freq. hop rate 1600 hops/s
@Satish Sura

Frequency hopping in action (1)
Bluetooth technology operates in the 2.4 GHz ISM band,
using a spread spectrum, frequency hopping, full-duplex
signal at a nominal rate of 1600 hops/second.
@Satish Sura

Frequency hopping spread spectrum (2)
The adaptive frequency hopping (AFH) feature (from
Bluetooth version 1.2 onward) is designed to reduce
interference between wireless technologies sharing the 2.4
GHz spectrum.
@Satish Sura

Frequency hopping spread spectrum (3)
In addition to avoiding microwave oven interference, the
adaptive frequency hopping (AFH) feature can also avoid
interference from WLAN networks:
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Frequency hopping in action
The piconet master decides on the frequency hopping
sequence. All slaves must synchronize to this sequence. Then
transmission can take place on a TDD-TDMA basis.
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Link delivery services
Two types of links can be established between the piconet
master and one or more slaves:
Synchronous connection-oriented (SCO) link allocates a fixed
bandwidth for a point-to-point connection involving the
piconet master and a slave. Up to three simultaneous SCOpiconet master and a slave. Up to three simultaneous SCO
links are supported in a piconet.
Asynchronous connectionless or connection-oriented (ACL)
link is a point-to-multipoint link between the master and all
the slaves in the piconet. Only a single ACL link can exist in the
piconet.
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Bluetooth core system architecture
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IEEE 802.15.4 LR-WPAN (ZigBee)
ZigBee technology is simpler (and less expensive) than
Bluetooth.
The main objectives of an LR-WPAN like ZigBee are ease of
installation, reliable data transfer, short-range operation,
extremely low cost, and a reasonable battery life, whileextremely low cost, and a reasonable battery life, while
maintaining a simple and flexible protocol. The raw data rate
will be high enough (maximum of 250 kbit/s) to satisfy a set
of simple needs such as interactive toys, but is also scalable
down to the needs of sensor and automation needs (20 kbit/s
or below) using wireless communications.
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LR-WPAN device types
Two different device types can participate in an LR-WPAN
network:
Full-function devices (FFD) can operate in three modes
serving as a personal area network (PAN) coordinator, a
coordinator, or a device.coordinator, or a device.
Reduced-function devices (RFD) are intended for
applications that are extremely simple.
An FFD can talk to RFDs or other FFDs, while an RFD can talk
only to an FFD.
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Star topology
In a star network, after an FFD is activated for the first time, it
may establish its own network and become the PAN
coordinator. The PAN coordinator can allow other devices to
join its network.
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Peer-To-Peer Topology
In a peer-to-peer network, each FFD is capable of
communicating with any other FFD within its radio sphere of
influence. One FFD will be nominated as the PAN coordinator.
A peer-to-peer network can be ad-hoc, self-organizing and
self-healing, and can combine devices using a mesh
networking topology.
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ZigBee PHY and MAC parameters
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Antenna Design BasicsAntenna Design Basics
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Definition
An antenna is basically a conductor exposed in space. If the
length of the conductor is a certain ratio or multiple of the
wavelength of the signal, it becomes an antenna. This
condition is called “resonance”, as the electrical energy fed to
antenna is radiated into free space.antenna is radiated into free space.
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Dipole Antenna
The conductor has a length
λ /2, where λ is the wave length of the
electric signal. The signal generator
feeds the antenna at its center point by
a transmission line known as “antenna
feed”. At this length, the voltage andfeed”. At this length, the voltage and
current standing waves are formed
across the length of the conductor
The antenna geometry has two most
important considerations:
1. Antenna length
2. Antenna feed
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Quarter-Wave / Monopole Antenna
For a quarter-wave antenna that is used
in most PCBs, the important
considerations are:
1. Antenna length
2. Antenna feed
3. Shape and size of the ground plane
and the return pathand the return path
By having a ground at some distance
below the conductor, an image is created
of the same length (λ /4).
The signal is fed single-ended.
The ground plane acts as the return
path.
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Antenna Wavelength Calculation
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Return Loss
The power ratio of the reflected to the incident wave is
called Return Loss
S11 is the negative of return loss
expressed in decibels
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Bandwidth
Bandwidth indicates the frequency response of an antenna.
Bandwidth signifies how well the antenna is matched to the 50-Ω
transmission line over the entire band of interest.
If the return loss is infinite, the
antenna is said to be perfectly
matchedmatched
As a rule of thumb, a return loss
≥ 10 dB (equivalently, S11 ≤ –10
dB) is considered sufficient.
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Radiation efficiency
A portion of the non-reflected power gets dissipated
as heat or as thermal loss in the antenna. Thermal
loss is due to the dielectric loss in the FR4 substrate
and the conductor loss in the copper trace. This
information is characterized as radiation efficiency.information is characterized as radiation efficiency.
A radiation efficiency of 100 percent indicates that all
non-reflected power is radiated to free space.
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Radiation pattern
Radiation pattern indicates the directional property of
radiation, that is, which directions have more radiation and
which have less
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Antenna Design
An Isotropic Antenna is a theoretical antenna
that radiates a signal equally in all directions.
A Dipole Antenna is commonly used in
wireless systems and can be modeled similarly
to a doughnut
Power measurements are referenced to isotropic antenna in dBi
The Dipole represents a directional antenna
with a further reach in the X&Y Plane (at the
cost of a smaller reach in the Z plane) to the
Isotropic.
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Antenna Design - Types
Single-ended antenna connection
Usually matched to 50 ohm
Requires a balun if the TRx-chip has a differential output
Easy to measure the impedance with a network analyzer
Easy to achieve high performance
Differential antenna connectionDifferential antenna connection
Can be matched directly to the impedance at the RF pins
Can be used to reduce the number of external components
Complicated to make good design, might need to use a simulation
Difficult to measure the impedance
Possible to achieve equivalent performance of single-ended
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Typical Single & Differential
Ended Antennas
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Antenna Design - Types
PCB antennas
No extra cost development
Requires more board area
Size impacts at low frequencies and certain
applications
Good to high range
Requires skilled resources and softwareRequires skilled resources and software
Whip antennas
Cost from (starting~ $1)
Best for matching theoretical range
Size not limiting application
Chip antennas
Less expensive (below $1)
Lower range @Satish Sura

Solution – Antenna Design
Antennas Affect:
TRP (Total Radiated Power) – radiation efficiency and tuning
TIS (Total Isotropic Sensitivity) – radiation efficiency, antenna
placement (noise pickup)
RSIC (Receiver Sensitivity Intermediate Channels) – if passing TIS,
then RSIC failures are spurious emissions problemthen RSIC failures are spurious emissions problem
RSE (Radiated Spurious Emissions) – antenna cable routing, antenna
placement
Conti ..@Satish Sura

Best Practices:
Antennas must be designed into product before mechanical/industrial design is
locked down: space is key
As antenna size decreases, efficiency decreases – allocate space
Nearly everything in today’s small IoT devices is part of the antenna system.
Metal and other materials will detune an antenna, affect pattern, degrade efficiency,
or couple and radiate
Keep antenna away from metal such as PCB, display, cables, enclosureKeep antenna away from metal such as PCB, display, cables, enclosure
Conti..@Satish Sura

Best Practices:
Keep antennas away from noise sources – switching regulators,
microprocessors (causes receiver de-sense)
Keep antenna and RF transmissions away from power nets
Tune antenna in final configuration
Tune antenna to favor transmit frequencies instead of receiveTune antenna to favor transmit frequencies instead of receive
Maintain evaluation board-size ground plane when using ceramic
surface mount antennas.
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Solution – Off the Shelf Antennas
Lower NRE, higher unit cost
Fastest development route
Can perform well with right ground plane and system design
Datasheets only accurate for one very specific ground plane
arrangement
Cabled antennas can create EMI issues – coax shields often pick up
and radiate spurious emissions, harmonics, or broadband noise. Bestand radiate spurious emissions, harmonics, or broadband noise. Best
with clean, straight, cable routings
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Solution – Custom Antennas
Break-even point can start as low as 10ku/yr, depending on OTS
antenna price, antenna complexity
Necessary to achieve performance in some enclosures and systems
Cellular handset and tablet PC antennas are usually custom
Allow for simulation not possible with off-the-shelf antennas,
especially helpful for ECCespecially helpful for ECC
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Lower frequency increases the antenna range
Reducing the frequency by a factor of two doubles the range
Lower frequency requires a larger antenna
λ/4 at 433 MHz is 17.3 cm (6.81 in)
λ/4 at 915 MHz is 8.2 cm (3.23 in)
λ/4 at 2.4 GHz is 3.1 cm (1.22 in)
Frequency vs. Size
λ/4 at 2.4 GHz is 3.1 cm (1.22 in)
A meandered structure can be used to reduce the size
λ/4 at 2.4 GHz
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Solution – Inverted-F Antenna
The F-antenna can be thought of as a tilted whip, where impedance
matching is accomplished by tapping the antenna at the appropriate
impedance point along its width.
This antenna is used extensively because it is reasonably compact.
Fairly Omni-directional radiation pattern, good efficiency, and is very
simplesimple
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The meander antenna or meander pattern, is an antenna with the
wire folded back and forth where resonance is found in a much more
compact structure
Meander Antenna
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Antenna Design: Do’s and Don’ts
Never place ground plane or tracks underneath the antenna
Never place the antenna very close to metallic objects
In the final product, ensure that the wiring and components do not get too
close to the antenna
A monopole antenna will need a reasonable ground plane area to be efficient
Do the final tuning in the end product enclosure, not in open air
Never install a chip antenna in a vastly different layout than the reference
design and expect it to work without tuningdesign and expect it to work without tuning
Do not use a metallic enclosure or metalized plastic for the antenna
Test the plastic casing for high RF losses, preferably before production
Never use low-Q loading components, or change manufacturer without
retesting
Do not use very narrow PCB tracks. The tracks should be relatively wide as
space allows
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Antenna Design Tools
EM Simulation
Momentum Agilent
http://eesof.tm.agilent.com/products/momentum_ma
in.html
HFSS Ansoft http://www.ansoft.com/products/hf/hfss/
IE3D Zeland http://www.zeland.com/
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Rf fundamentals

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Rf fundamentals