The Research Of Feedhorn In High Performance Compact Antenna Test Range

With the wide application of millimeter wave and sub millimeter wave technology in radio astronomy and remote sensing field,it is more and more urgent to test the performance of electrically large millimeter wave and sub millimeter wave antennas.The system performance requirements of traditional near-field scanning test method in high frequency band are very high,testing time is longer,and far-field testing method is not easy to achieve because of the long distance.The system of CATR(Compact Antenna Test Range)testing method can generate plane wave in limited anechoic chamber to test antennas.Therefore,it is the best method to measure electrically large antenna in millimeter and sub millimeter wave band.In CATR system design,feed characteristics have a great influence on the performance of the whole CATR system.This paper focuses on the research of CATR feed characteristics,the main research work includes:1.The tri-reflector CATR antenna measurement system principle was studied,and using the commercial simulation software to simulate the tri-reflector CATR antenna measurement system,which laid the foundation for the following research work.2.The corrugated horn feed general characteristics,design parameters and simulation processes were studied,on this basis,we designed a Tan-profile corrugated horn which was simulated and verified by the commercial simulation software CHAMP.The simulation results showed that the side-lobe level of the feed far-field radiation pattern less than-45dB,the cross-polarization isolation was close to 45dB.The comparison results with the performance of Sin-profile corrugated feed which was designed by our research team showed that the side-lobe level reduced 10dB,the cross polarization isolation reduced 5dB.3.In order to verify the impact of feed performance on CATR system performance,the ideal Gaussian feed,Sin2-profile corrugated horn and Tan-profile corrugated horn were used as feed in the CATR system.The quiet zone simulation results showed that when Tan-profile corrugated horn was used as feed,the amplitude ripple of the system was within 1dB,the phase ripple was below 8°,and the cross polarization level less than-30dB,which meet the requirements of millimeter wave and sub millimeter wave band electrically large antenna measurement.Compared with Sin2-profile corrugated feed,the amplitude variation of system quiet zone decreased 0.1 dB,the phase variation decreased 0.3°,and the cross polarization level decreased 0.8dB which proved that Tanh-profile corrugated horn can improve the performance of CATR system.4.The design of polycyclic feed array were explored and studied.A four-ring feed array was preliminary designed by MATLAB,and the design method and process of feed array was given,while the simulation radiation characteristics of the feed were used as the feed of the offset parabolic reflector,by comparing the quiet zone simulation results of using single feed to further optimize the design of the feed array,so that the size of the quiet zone was improved.