A Validity study on Dip & Vacuum Brazing

Method for Ka-band Waveguide Slot Array

Antenna

Chae-Hyun Jung1, Jong-Gyun Baek1, Kook-Joo Lee1, Chang-Hyun Park1 and Jongkuk Park1 1LIG Nex1 Co.,Ltd, 148-1, Mabuk-dong, Giheung-gu, Yongin-City, Gyeonggi-do, Republic of Korea.

Abstract - In this paper, two different fabrication methods,

which are dip-brazing and vacuum-brazing, are applied to Ka-band waveguide slot array antenna for radar system. Dip &

vacuum brazing needs a different jig design and layer composition for manufacture in the same design model. The validity of each method is verified by comparing between the

simulation and the measurement result. According to the result, it is found that both fabrication methods are available for Ka-band waveguide slot array antenna.

Index Terms — Slot array antennas, Dip-brazing, Vacuum-brazing

1. Introduction

The planar waveguide slot array antenna has frequently

been used in radar systems. Especially, it is widely applied to

airborne radars or seeker systems. This kind of system

physically needs light weight and operating in the high

power circumstance. In order to satisfy requirements,

aluminum which is a relatively light metal has usually been

chosen to make a waveguide slot array antenna.

The waveguide slot array antenna consists of multiple

layers and each layer is joined strongly together to block the

electromagnetic wave leaking by using a special fabrication

method, such as dip and vacuum-brazing. As operating

frequency is getting high, the dimension of standard

waveguide becomes small for joining. So, fabrication

method should be considered in the way that is relatively less

sensitive to the manufacturing errors which are the residue

inside waveguide after brazing and the machining error. At

Ka-band it requires much more precision machining and is

also more important to get rid of residue inside waveguide

after brazing. Due to the demand, the vacuum-brazing is

useful at Ka-band because it works in vacuum which means

there is no flux inside waveguide like the dip-brazing to

remove. But it is not easy to find the optimized vacuum

chamber operation condition at a certain design model.

In the following Section 2, by comparing between

designed data and measurement the effectiveness of the dip-

brazing antenna at Ka-band is shown[1]. Then, the vacuum-

brazing antenna is considered as well in Section 3[2]. Finally,

conclusion is given in Section 4.

2. Dip-brazing antenna

The antenna design is following the Elliott’s design

procedure[3]. In order to have above 28 dBi gain,

6.3˚ ±0.5˚ of 3dB beamwidth and below -22dB SLL(Side-

Lobe Level) at Ka-band, taylor weighting distribution in

diameter 11.66λ 0 is used and it has two channels for the

monopulse. Its performance is verified with a commercial

electromagnetic analysis tool(CST). After the design, the

fabricated antenna by the dip-brazing is depicted in Fig. 1.

(a) Front view (b) Back view

Fig. 1. Fabricated dip-brazing antenna

A comparison of the measured and simulated patterns is

given in Fig. 2. Beamwidth and SLL are similar to what

expected and the measured gain is 28.1 dBi at the center

frequency of the design bandwidth.

(a) Azimuth radiation pattern

Sum port

Del port

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

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(b) Elevation radiation pattern

Fig. 2. Radiation pattern of the dip-brazing antenna

3. Vacuum-brazing antenna

Design values in the vacuum-brazing antenna are above 33

dBi gain, 3.5˚ ±0.5˚ of 3dB beamwidth and below -22dB

SLL in diameter 23.33λ 0.Three channels are considered for

using the monopulse technique. The fabricated antenna by

the vacuum-brazing is shown in Fig. 3.

(a) Front view (b) Back view

Fig. 3. Radiation pattern of the vacuum-brazing antenna

Its comparison of the measured and simulated patterns is

given in Fig. 4. The both is similar to the design result at

beamwidth and SLL and the gain, 33.2 dBi, is measured at

the center frequency of the design bandwidth.

(a) Azimuth radiation pattern

(b) Elevation radiation pattern

Fig. 4. Radiation pattern of the vacuum-brazing antenna

4. Conclusion

Two different waveguide slot array antennas are designed

at Ka-band. To manufacture antennas, the dip-brazing and

the vacuum-brazing are applied respectively.

In the dip-brazing the holes are applied to the end of

waveguide in antenna and the customized jig to remove the

residue cleanly. In the vacuum-brazing the optimized

vacuum chamber operation condition such as pressure and

temperature profile is found with the designed jig.

From the electrical result it is realized that both methods

are available to make the complicated structure of Ka-band

waveguide slot array antenna.

References

[1] Chae-Hyun Jung, Jong-Gyun Baek, Kook-Joo Lee, Chang-Hyun Park,

Jun-Beom Kwon, “Waveguide Broad-wall Slot Array Antenna Study for Millimeter-Wave Seeker Using Cross Monopulse Axes“, JIIBC,

pp. 209-215, Oct. 2017. [2] Jong-Gyun Baek, Chae-Hyun Jung, Kook-Joo Lee, Chang-Hyun Park,

“Waveguide Broad-wall Slot Array Monopulse Antenna for

Millimeter-Wave Seeker Using Dip Brazing Method”, KIEES, pp. 1020-1026, Nov. 2015.

[3] R. S. Elliott, Antenna Theory and Design, Prentice-Hall, 1981.

Del Az port

Sum port

Del El port

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

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