3F1-1 Proceedings of ISAP2016, Okinawa, Japan
Design of a Double Layer Cavity backed Slot Array
Antenna in Gap Waveguide Technology
Peiye Liu, Ashraf Uz Zaman, Member, IEEE, Per-Simon Kildal, Fellow, IEEE
Dept. of Signals and Systems, Chalmers University of Technology. Gothenburg, Sweden .
Abstract – In this paper a double layer cavity backed slot array excited by a ridge gap waveguide section with a T-section as
antenna at K band is presented. The slot antenna is built using is shown in Fig. 1. During simulat ion, two sets of periodic
ridge gap waveguide feed network and gap waveguide cavity layer.
These antenna blocks are manufactured without the requirements
boundary walls are placed in the external region of the unit
of electrical contact between the metal plates. Th e corporate-feed cell to simulate the mutual coupling in the infinite two -
network is realized by a texture of pins and a guiding ridge in the dimensional slot array. Boundary on top and bottom are open
bottom plate. The 4×4 slot array antenna has been fabricated and and PEC respectively. The cavity is part itioned into four
measu red. The measured reflection coefficient remains below - parts by two sets of metal blocks, and the coupling slot is
11dB with reasonably good radiation pattern s over the band of
interest from 18.2 GHz to 21.2 GHz.
placed at the center of the cavity. Two sets of metal blocks
are placed to suppress unwanted higher modes in the cavity.
Index Terms — slot array antenna, double layer, gap The slot spacing is chosen to be 12mm which is 0.82λ.
waveguide.
1. Introduction
Planar array antennas are suitable for a lot of applicat ions
requiring high to moderate antenna gain. Microstrip antenna
arrays and waveguide slot arrays are the two main planar
antenna technologies, which have been used extensively over
a wide range of frequencies. Microstrip arrays are co mpact,
easy to manufacture, cost-effective and easy to integrate with Fig. 1. Prototype in three separate layers.
active electronics. However, the microstrip feed networks b. Full Corporate Feed Networks
suffer fro m high oh mic and dielectric losses at high The full corporate feed network fo r the 4×4 element array
frequency. Waveguide slot antenna arrays are also popular antenna consist of a transition fro m W R-42, 3-dB power
antenna with their high antenna efficiency and high gain [1- dividers and a T-section to excite the coupling slots of the
2]. Ho wever, the strict requirements of surface to surface cavity layer. Shown in Fig.2 are the frequency characteristics
electrical contact at high frequency make it costly and of the reflection of each part. The simulated S-parameters for
complex to manufacture. the feed network remain within the acceptable limits.
To overcome the above mentioned problems, we introduce
gap waveguide technology which is a co mbination of Perfect
Electric Conductor (PEC) plate and a Perfect Magnetic
Conductor (PMC) p late paralleled with an air gap smaller
than a quarter wavelengths in between. There is no need for
metal contact which solves the problem of good electric
contact between metal layers [3-5]. Till now several antennas
have been designed based on gap waveguide technology [6-
8]. Also gap waveguide has much less loss compared with
normal microstrip lines. Also it is very suitable for RF
packaging [9-10].
In the present paper a 4×4 element array antenna is
presented where a ridge gap waveguide has been used as a Fig.2. Reflection coefficient of each part.
feed network. Shown in Fig.1 is a photo of three parts of the
antenna prototype. c. 4×4 Element Array Antenna
The full structure of the 4×4 element array antenna that
2. Antenna Design combines the 2×2 element subarrays and the full corporate
feed waveguide is redesigned to comp ly with manufacturing.
a. 2×2 Element Subarray All sharp corners in former design are changed into round
The 2×2 element subarray is the unit cell of the proposed ones with radius of 0.5mm. The structure has been optimized
antenna. The subarray contains three metal layers. On the top for good S11 and good radiation characteristics. As shown in
is the slot layer. Below the slot layer is the cavity layer and Fig. 3, the simulated directivity and gain are over 19.5dBi,
this cavity layer has coupling slots. The coupling slots are and simulated aperture efficiency is over 95% for this 4×4
element slot array.
Copyright ©2016 by IEICE 682
Fig. 3. Directivity and Gain simulated.
3. Measured Results
The prototype is manufactured using Aluminum metal.
The reflection coefficient or S11 is measured with vector
network analy zer (VNA ). The measured S11 is shown in
Fig.4 together with simulated one.
Fig. 5. Measured E-plane (top) and H-plane (bottom)
pattern for the proposed antenna.
References
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