Research On High Performance Probe Antenna For Antenna Measurement

In the antenna measurement system,the probe antenna is indispensable as a transceiver device.According to different measurement systems,commonly used probe antennas include horn antennas and open-ended waveguide antennas.Although they are mature in design theories and easy to manufacture,there are some disadvantages such as narrow operating bandwidth,single polarization and insufficient pattern performance.Therefore,in order to improve the accuracy and efficiency of the measurement system,it is urgent to develop high-performance probe antennas.This thesis designs high-performance probe antennas that can be used for far-field measurement or near-field measurement by studying three aspects of broadband,dual polarization and wide beam.Compared with existing horn probes and open-ended waveguide probes,measurement errors and time costs can be effectively reduced.The main research contents of this thesis are as follows:1.Considering to broaden the operating bandwidth of the probe antenna,a broadband horn probe is proposed in this thesis.In line with the theory of the ridge waveguide,firstly,the exponential metal dual-ridge structure is loaded in a pyramidal horn antenna.Then,the feeding part structure such as the air reflection cavity is specially designed.The structural dimensions of each part are simulated and optimized.Finally,the operating bandwidth of the horn antenna is broadened and its higher-order modes inside are suppressed.The designed broadband horn probe has a voltage standing wave ratio of less than 1.9 in the frequency range of 2GHz～18GHz,that is,the operating bandwidth of 9 octaves is achieved and covers commonly used frequency bands such as S,C,X and Ku.Its gain is in the range of4.2d Bi～13.0d Bi.In addition,its pattern performance is passable and cross-polarization discrimination is greater than 31 d B.The physical prototype is manufactured and tested.Comparing the test results and simulation results,the high performance of the broadband horn probe is verified.2.Aiming at improving the single-polarized operating characteristic of the probe antenna,a dual-polarized horn probe is proposed in this thesis.Firstly,an ordinary conical horn section is improved into the horn section that opens at speeds gradually increasing in five levels.Secondly,on the basis of the research on broadband,the reversed exponential quad-ridge structure with a linear correction term and cross-shaped metal block are loaded in the horn antenna.Then,based on the principle of differential feeding,two pairs of signals with equalamplitude and anti-phase are generated by a set of broadband differential power dividers that are based on the microstrip line-slot line coupling structure to feed the horn antenna.The designed dual-polarized horn probe has a voltage standing wave ratio of less than 2 in the frequency range of 2GHz～10GHz,that is,the operating bandwidth of 5 octaves is achieved.Its port isolation is greater than 46 d B and gain is in the range of 7.8d Bi～20.0d Bi.Besides,its pattern performance is good and cross-polarization discrimination is greater than 45 d B.The physical prototype is also manufactured and tested.Comparing the test results and simulation results,the high performance of the dual-polarized horn probe is verified.3.So as to improve the pattern performance of the probe antenna,a wide-beam open-ended waveguide probe is proposed in this thesis.It is similar to the design of the dual-polarized horn probe.The Bessel-type reversed quad-ridge structure and cross-shaped metal block are loaded in an open-ended circular waveguide antenna.Two pairs of signals with equalamplitude and anti-phase are generated by differential power dividers to feed the open-ended waveguide antenna.The designed dual-polarized open-ended waveguide probe has a voltage standing wave ratio of less than 1.7 in the frequency range of 6GHz～14GHz.Its port isolation is greater than 42 d B and gain is in the range of 5.7d Bi～10.8d Bi.Moreover,its pattern performance is good and cross-polarization discrimination is greater than 40 d B.On this basis,in the light of the theory of the aperture antenna,methods such as narrowing the aperture of the waveguide,improving the structure of the waveguide and ridge near the aperture are proposed.Simulate it and optimize some of its structural parameters.Finally,the beamwidth of the pattern of the open-ended waveguide probe is broadened to varying degrees.