Waveguide Slot Filtering Antenna with Metamaterial Surface · 2018. 10. 19. · waveguide divider for broadenning the bandwidth of a waveguide slot antenna array [4]-[5] offers a

Waveguide Slot Filtering Antenna with

Metamaterial Surface

Wei Wang, Zhi Zheng, Hong-tao Zhang, Mou-ping Jin, Ying Liu East China Research Institute of Electronic Engineering, Hefei, P. R. China

East China Research Institute of Electronic Engineering, Hefei, P. R. China

East China Research Institute of Electronic Engineering, Hefei, P. R. China

East China Research Institute of Electronic Engineering, Hefei, P. R. China

Science and Technology on Antenna and Microwave Laboratory, Xidian University, Xi’an, P. R. China

Abstract - Novel metamaterial waveguide slot antenna with

filtering performance is presented. The antenna is composed

of a rectangular waveguide, longitudinal slots cut in its upper broadwall and a metamaterial surface instead of the bottom broadwall. The antenna performs excellent filtering ability

using the matematerial surface, in the specified interfering band. And two kinds of the surface are described in this work. One is in the form of metal bed of nails while the other is

made up by periodic mushroom-type cell.

Index Terms — Filtering antenna, Waveguide slot antenna Metamaterial surface.

1. Introduction

With the eruptible development of the wireless

communication, electromagnetic compatibility (EMC)

problems are increasingly serious, which promotes the

development of anti-interference technology and has

attracted abundant research efforts [1]. Filtering antennas

[2]-[3], which have radiating and filtering functions

simultaneously, can effectively improve the anti-

interference performance of electronic systems so cater

for the demand. And compared with the traditional

design of cascading the filter right after the antenna,

filtering antennas have more compact structure, lighter

weight and lower cost.

Many kinds of design approaches of filtering antennas

have been reported. In [2], a bandpass filtering performance

was achieved by placing a parasitic loop at the top of a

printed antenna. Based on multilayer low-temperature

cofired ceramic (LTCC) technology, a quasi-elliptic filter

was integrated into a microstrip line to feed a series-fed

antenna array in V-band [3]. In our previous work, the

waveguide divider for broadenning the bandwidth of a

waveguide slot antenna array [4]-[5] offers a proper

structure to insert filters in the array, obtainning a filtering

antenna array [6]. Recently, a synthesis process for

filtering antenna design has been presented. In these

designs, the antenna not only radiates, but also serves as the

last resonator or the load impedance of the filter [7]-[8].

Nevertheless, in some designs, the filtering structure needs

extra circuit area, leading to large size. While in the others,

due to the lack of the exact extraction of the antenna’s

equivalent circuit, the filtering performance is limited.

In this paper, a waveguide slot filtering antenna using

metamaterial surface is proposed. The proposed filtering

antenna consists of a waveguide slot antenna and a

metamaterial surface embedded at the bottom of the

waveguide cavity. Different from the previous design

process, additional filter circuit is not necessary in our

approach. The rejection function at the interference

frequencies is achieved using the inherent bandgap of the

metamaterial surface.

2. Geometry of the filtering antenna

The geometry of the proposed waveguide slot filtering

antenna array is shown in Fig.1. The configuration is

similar to the conventional waveguide slot antenna, except

that the smooth metal plane in the bottom of the rectangular

waveguide is replaced by a metamaterial surface.

(a) with bed of nails

(b) with mushroom-type substrate

Fig. 1. Structure of the proposed filtering antennas

2018 International Symposium on Antennas and Propagation (ISAP 2018)October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea

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The metamaterial surface can be achieved using many

kinds of periodic structure, such as bed of nails, as shown

in Fig. 1(a) and mushroom-type substrate, as shown in

Fig.1 (b).

At the operating frequencies, the metamaterial surface

performs as a perfect electric conductor (PEC), so the

antenna radiates just like the traditional waveguide slot

antenna. While in the interference band, the surface

performs as a perfect magnetic conductor (PMC), with the

height of the waveguide cavity less than 4S ( S is the

smallest wavelength of interference band), it can stop the

propagation of electromagnetic wave in the waveguide

cavity, so the interference signal is rejected and a filter

function is achieved.

3. Simulation results

Due to the limit of the extent and the similarity between

the antennas shown in Fig. 1(a) and Fig. 1(b), only the

simulated results for Fig. 1(b) will be shown here.

Firstly, the simulated transmission coefficient of the

metamaterial waveguide is plotted in Fig. 2. The

metamaterial waveguide is composed of a rectangular

waveguide and a mushroom-type surface replacing the

smooth metal plane at the bottom of the waveguide cavity.

As seen in Fig. 2, in the working band, it has a nearby-0dB

performance. While in the interference band, its value is

below -60dB, means the wave is strongly rejected. The

rejection function arrives because there is a bandgap for the

mushroom-type surface at the same frequency band.

Fig. 2. Simulated S21 of the filtering waveguide

Then, the filtering antenna is arrived cutting radiating

slots in the upper broadwall. Four slots are adopted in this

work. The offset and length of the slots are carefully

adjusted to meet good impedance matching and radiation

property. The received energy when illuminated by an

ultra-wide band horn is plotted in Fig. 3. Compared with

the value of -23dB in the working band, it is always below

-65dB in the interference band (over 7.90~8.75GHz), this

means a suppression level stronger than 40dB is achieved.

Fig. 3. Simulated received energy illuminated by an ultra-

wide band horn

4. Conclusion

A novel design approach of waveguide slot filtering

antenna is presented. The filtering function is obtained

using the bandgap property of the metamaterial surface,

which is embedded at the bottom wall of the waveguide

cavity. A 4-slot antenna is designed and the excellent

simulated results have verified the innovative method

Acknowledgment

This work was supported by the National Natural Science

Foundation of China under Grant 61671416.

References

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2018 International Symposium on Antennas and Propagation (ISAP 2018)October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea

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