Research On Monopulse Antenna Of Planar Structure

In a single pulse cycle, Monopulse antenna can receive the azimuth angle, elevation angle and distance information. It has the advantage of fast obtaining error signal, strong anti-interference ability and so on. The traditional monopulse antenna is large and heavy. It is not convenient to be integrated with forward components of missile or airplane which has limited volume. So the research of planar monopulse antenna is of great significance.Substrate integrated waveguide(SIW) is a novel waveguide structure which has good propagation characteristics and takes the advantages of low profile, easy to fabricate and low cost. In this article, The main purpose is to use SIW to realize the planar monopulse antenna at Ka band. The main work is as follows:1. The basic theory of the monopulse antenna, the design method of SIW monopulse antenna feed system is introduced. The radiation characteristics of single SIW slot is studied. Then, we discussed the design method of SIW resonant slot antenna array.2. Combing the theory analysis and 3D electromagnetic simulation software, we designed the 16 units SIW slot antenna with one dimensional Taylor distribution. Then the planar monopulse antenna is composed of this SIW antennas. To make the H sidelobe level reduce to below-25 dB, the slot array parameters are amended. The T-junction and Y-junction power divider are presented and optimized. Using this two strcture we achieved a compact SIW four-way power divider.3. In order to facilitate the integration of radiation antenna, we designed a planar sum and difference network which is composed of four 3dB directional coupler and four 90° phase shifter. Simulation results indicate that the reflection coefficient of each port is less than-15 dB from 34 GHz to 36 GHz, the power difference between the four outout ports is less than ? 0.4dB and the phase difference is less than ? 5°.4. The design of the overall structure of planar monopulse antenna feed system. To reduce the size, the whole system is integtated in two layers which is 140×107mm and the thickness is 1.2mm. The weight is only 80 g. Compared with the original waveguide sum and difference network(volume 160x160x35 mm, weight 1300g), its volume and weight is greatly reduced.5. To meet the need of project, a monopulse sum and difference network composed of four waveguide step-shaped magic tee is proposed at Ka band. The test results indicate that the reflection coefficient of each port is less than-12 dB from 34 GHz to 36 GHz, the output port of the transmission coefficient is above-7.5dB, the power difference between the four outout ports is less than ? 0.5dB and the phase difference is less than ? 4°.