
906 IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, VOL. 6, NO. 6, JUNE 2016
Gap Waveguide PMC Packaging for
Two-Layer PEC Surfaces
Jing Zhang, Student Member, IEEE, Xiupu Zhang, Senior Member, IEEE, and Dongya Shen, Member, IEEE
Abstract—This paper shows the investigation of gap
waveguide (GW) packaging for an irregular perfect electric
conductor (PEC) composed of two layers of metal surfaces. The
stopband for a GW with two-layer PEC surfaces is carefully
studied, considering the top-layer PEC width, pin size, pin
height, columns of pins, as well as dielectric substrate thickness
and permittivity. A strategy of the GW packaging for such an
irregular PEC surface is presented. In addition to the unit cell-
based stopband study, such GW packaging is also demonstrated
for a substrate-integrated waveguide (SIW)–microstrip line struc-
ture, which is typical of the circuit with two-layer PEC surfaces.
A Chebychev bandpass filter built on the SIW and microstrip
line is finally designed and fabricated to provide experimental
verifications. In particular, a dedicated defect of the side air gap
existing in the SIW-based circuits using the GW PMC packaging
is found, and an effective remedy is presented.
Index Terms— Gap waveguide (GW), microwave, packaging,
perfect electric conductor (PEC), perfect magnetic conduc-
tor (PMC).
I. INTRODUCTION
A
S AN important use of gap waveguide (GW), GW-based
perfect magnetic conductor (PMC) packaging technology
has been widely investigated in the past years [1]–[5]. The
basis of this new shielding method is using an artificial
PMC that is built by periodic structures. When a perfect
electric conductor (PEC) is separated from the PMC by
a distance smaller than a quarter wavelength, the propagation
of an electromagnetic field is forbidden between them since
the boundary conditions are not fulfilled. A desired quasi-
transverse electromagnetic propagation mode can be obtained
Manuscript received December 27, 2015; revised March 25, 2016;
accepted May 2, 2016. Date of current version June 9, 2016. This
work was supported in part by the Quebec FQRNT Project in Broad-
band Photonic Devices, in part by the Yunnan High-Tech Top-Talents
Recruitment Project under Grant 2012HA005, in part by the Yunnan
Key Project of International Cooperation under Grant 2009AC010, and in
part by the National Science Foundation of China under Grant 61561051
and Grant 61561052. Recommended for publication by Associate Editor
L.-T. Hwang upon evaluation of reviewers’ comments.
J. Zhang is with iPhotonics Laboratories, Department of Electrical and
Computer Engineering, Concordia University, Montreal, QC H3G1M8,
Canada, and also with iCom Laboratories, School of Information Sci-
ence and Engineering, Yunnan University, Kunming 650091, China (e-mail:
X. Zhang is with iCom Laboratories, School of Information Science
and Engineering, Yunnan University, Kunming 650091, China, and also
with iPhotonics Laboratories, Department of Electrical and Computer Engi-
neering, Concordia University, Montreal, QC H3G1M8, Canada (e-mail:
D. Shen is with iCom Laboratories, School of Information Science
and Engineering, Yunnan University, Kunming 650091, China (e-mail:
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/TCPMT.2016.2564425
by means of a conducting ridge in the PMC surface or a narrow
metal strip above it, but no other propagating modes can
exist [6]–[8].
Various PMC periodic constructions have been proposed for
different frequency ranges and circuits, such as lid of pins [9],
lid of springs [10], lid of printed zigzag wires [11], inverted
pyramid-shaped pins [12], and simplified lid of pins for
substrate-integrated waveguide (SIW)- and grounded coplanar
waveguide (GCPW)-based filters [13]. Recently, the GW PMC
packaging for an irregular PEC surface has attracted research
interests since the creation and performance of the GW stop-
band significantly depend on the air gap between the PMC
and PEC [14]. In [14], an unsmooth PEC surface caused
by metalized vias was studied and it has been proved that
the interference of such an irregular PEC plane with the
GW stopband cannot be ignored. In this paper, another irreg-
ular PEC surface is investigated, in which both the upper
and base metal plates of a printed circuit board (PCB) are
considered. The effect of PCB upper metal plate can be
ignored for a microstrip line circuit with the GW packaging,
because this plate is just a narrow strip (very small width).
For a slotline, it is only necessary to consider the top ground
plane on a substrate rather than the PCB base metal plate due
to the normally narrow slot [14], [15]. However, if the top
metal strip/plate or the slot is large enough, the metal plates
on both sides of the dielectric substrate have to be taken into
account, because there are two different gap heights between
the PMC and PEC, and even an exposed substrate is existing
in the gap. Both the gap height and substrate permittivity (ε
r
)
will affect the created GW stopband characteristics. A typical
example is GW PMC packaging for an SIW combined with
microstrip lines. The microstrip line could be the SIW feed line
or used to realize other desired functions [16]–[20]. Owing to
the PMC shielding covering both SIW and microstrip line as
well as the large top metal plate of the SIW, a synthesis gap
effect must be considered, including the different gap heights
from the PMC to the SIW top and the base ground, as well
as the substrate exposed to PMC shielding.
This paper focuses on the GW PMC packaging for the
above-described two-layer PEC surfaces and the caused
synthesis gap effects. The PMC is built by periodic metal
pins. The impact of pin size, pin height, columns of pins,
and top-layer PEC width, as well as substrate height and
permittivity on the GW stopband performance is studied and
shown in Section II. A guideline is presented for such an
irregular PEC surface using the GW PMC packaging. Further
to the stopband study, in Sections III and IV, the GW PMC
packaging is demonstrated for an SIW–microstrip line
structure and a bandpass filter built on such a structure which
2156-3950 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.
See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.