Design of a new waveguide slotted antenna array

Teng Li, and Wenbin Dou

State Key Laboratory of Millimeter Waves

Southeast University

Nanjing 210096, China

liteng.nj@gmail.com, njdouwb@163.com

Abstract—In this paper, a new waveguide slotted antenna array, in which T-shaped cross section

waveguide is used as the radiating waveguide, is proposed and simulated. The T shaped radiating

waveguide can reduce the waveguide profile height. The radiating slots are etched and inclined alternately

on the top [1, 2, 3]. The metal fences are introduced between slots to repress the sidelobe level of E-plane [4].

A bend structure is invented to feed the T-shaped radiating waveguide [3, 5]. A 2 6 antenna array working

at Ka-band is designed and the obtained simulated results demonstrate this novel structure.

Keywords—antenna array; slot; T-shape; waveguide

References

[1] X.W. Zhao, Y. Zhang, T.K. Sarkar, S.W. Ting, and C.H. liang, “Analysis of a traveling-wave waveguide array with narrow-wall slots using higher order basis functions in method of moments,” IEEE Antennas Wireless Propag. Lett., vol. 8, pp. 1390-1393, 2009.

[2] S. Silver, “Linear array antennas and feeds” in Microwave Antenna Theory and Design, 1st ed., New York: McGraw-Hill, 1949, pp. 291-303.

[3] T. Li, H.F. Meng, and W.B. Dou, “Design and implementation of dual-frequency dual-polarization slotted waveguide antenna array for Ka-band aplication,” IEEE Antennas Wireless Propag. Lett., vol. 13, 2014, pp. 1317-1320.

[4] T. Li, H.F. Meng, and W.B. Dou, “The analysis of broadband slotted antenna array,” 2nd Asia-Pacific Conference on Antennas and Propagtion, August 5-7, 2013, pp. 15-16.

[5] Y.F. Fang and X.Q. Yan, “A rectangle waveguide four-way divider for wideband and miniaturization application,” IEEE 5th Internation Sym. MAPE, 2013, pp.315-318.

Forum for Electromagnetic Research Methods and Application Technologies (FERMAT)

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SOUTHEAST

UNIVERSITY

毫米波国家重点实验室State Key Lab. Of Millimeter Waves

中国·南京Nanjing·China

Design of a New Waveguide Slotted Antenna Array

Teng�Li�and�Wenbin Dou2015-03

liteng_nj@163.com; njdouwb@163.com

State Key Laboratory of Millimeter Waves, Southeast University

Contents

Introduction1

T-shaped Waveguide2

1×6 Linear Array3

Conclusions6

Metal Fences4

2×6 Antenna Array5

Introduction

Southeast University State Key Lab. Of Millimeter Waves

Slotted waveguide antenna array is a good candidate for using in radar systems and communication systems due to its low power loss, low profile, low cross-polarization levels, high efficiency, high power capacity, and accurate control of amplitude and phase distributions. The radiating slots are commonly etched on the wide-wall or narrow-wall of waveguide. The slots etched on the narrow-wall must cut into the broadside for resonance, furthermore, the height of profile is increased compared with the other one. In this paper, a T-shaped waveguide is proposed and a 2 6 antenna array with metal fences working at 35 GHz is designed based on this new waveguide. The radiating slots etched on the top of waveguide without cutting into the broadside and the height of profile is decreased.

T-shaped Waveguide

Southeast University State Key Lab. Of Millimeter Waves

Waveguide Type Dominant Mode Higher Modes Surface Current Distribution

Actually, the T-shaped waveguide can be seen as a half of double ridge waveguide which owns wider bandwidth. For the same guide wavelength, the new waveguide has a lower profile.

λg=16.00mm

h

h1+h2=1.5mm+2.47mm=3.97mmh=5.07mm>

For the dominant mode, the port field of T-shaped is in the horizontal direction as the rectangular one. For the higher modes, the electromagnetic wave can not propagate at the center frequency. Therefore, only the dominant mode is excited. Due to the surface current distribution of T-shaped waveguide is similar to the rectangular waveguide, the inclined slot can be used to cut the electric current and radiate the power. The top wall of waveguide is broadened, therefore, the slot can be resonant without cutting into the other waveguide wall.

1×6 Linear Array

Southeast University State Key Lab. Of Millimeter Waves

Although the new waveguide slotted antenna array has better performance than the conventional one, the SLL is still high around 90 degree which is mainly caused by the surface wave on the edge of the end of waveguide.

x y

zWider BandwidthHigher GainLower SLL

Metal Fences

Southeast University State Key Lab. Of Millimeter Waves

In order to suppress the surface wave , the metal fences are added in the end of the linear array.

Metal fences

fence_h

fence_w

Due to the mutual coupling between slots and the end-fed in the waveguide, the radiation pattern is asymmetric. Therefore, the metal fences can also be used between slots to reduce the mutual coupling.

fence_w=1.00mm

Compare with array A, the array B can suppress the surface wave and mutual coupling between slots more effectively.

When the height of fence larger than 1.5 mm, the sidelobe around 90 degree can be well suppressed. Around fence_h=λ/4, the mutual coupling between radiating slots can be reduced.

The cross polarization level is very high, but it can be suppressed in the planar array antenna by using the slot pair which includes two counter-rotating slots.

A

B

2×6 Antenna Array

Southeast University State Key Lab. Of Millimeter Waves

f0 = 35 GHz

Bandwidth (S11 < −20 dB): 845 MHz

Gain: 18 dB

SLL in E-plane: 14 dB

Cross polarization levels: −33.87 dB

Bend Structure: save space Y-junction Power Divider

Out-of-phase feeding network

Slot pair

Conclusions

Southeast University State Key Lab. Of Millimeter Waves

The proposed T-shaped waveguide is analyzed and a new slotted antenna working at 35 GHz is designed based on this novel structure. The simulated results indicate the effectiveness of the proposed structure including the T-shaped structure and metal fence. Due to no slots cutting into the broadside of waveguide, this novel antenna can easily interlaced with a ridged waveguide slotted antenna working at the other frequency band to realize dual frequency and dual polarization performance. In summary, the proposed is an attractive candidate for radar and communication systems.