Research On Key Techniques Of The Harmonic Radar

The Nonlinear Junction Detector is a kind of harmonic radar,which detects bugs,pinhole cameras and other devices containing nonlinear devices.Harmonic radar has a more effective ability of inhibiting clutters.It is a device that uses high frequency RF signal to scan a small area.Any nonlinear node near it(for example,the PN knot)receives this signal,and because the knot corresponds to the asymmetry of the electric field,harmonic components are emitted into the space and received by the detector.Almost all semiconductor electronic devices contain PN knots,so detectors can detect almost all unshielded electronic devices.The main contents of this thesis are as follows:The first chapter mainly introduces the harmonic radar technology and the current progress,at the same time we explain the purpose and significance of the design from the background,harmonic radar main mode of operation and so on.The second chapter introduces some important characteristic parameters of harmonic radar,including radar reflection cross section,radar action distance and so on.In addition,the technical index of transceiver component is introduced in detail.The third chapter introduces the design of circular polarized microstrips antenna.The operating frequencies of two antennas are 2.42 GHz and 4.84 GHz.Through simulation and test,we get that the transmitting antenna is a left-turn circular polarized antenna,in the2.35GHz-2.442 GHz frequency band,the S11 is less than-10 dB,and the gain greater than5 dB at 4.8GHz is less than-5dB.The receiving antenna is a left-handed circular polarized antenna,in the 4.667GHz-5.13 GHz frequency band,the S11 is less than-10 dB,the gain is greater than 6dB.The fourth chapter designs the waveguide filter used in harmonic radar.The volume of the filter is reduced by the method of capacitance loading,and the harmonic suppression at the corresponding frequency point is improved by increasing the order of the filter.Simulation and test results show that the 1dB bandwidth of the transmitter filter is2.25GHz-2.61 GHz,the minimum insertion loss in the frequency band is 0.6dB,and the S11 is less than-15 dB,The out-of-band suppression at 4.8GHz is higher than 105 dBc,the1dB bandwidth of the receiver filter is 4.68GHz-5.18 GHz,the minimum insertion loss in the frequency band is 0.6dB,the S11 is less than-15 db,and the Out-of-band suppression at the 2.4GHz is higher than the 105 dBc.The fifth chapter is designed to realize the front end of harmonic radar transceiver,and the target version is tested.The test of things shows that the transceiver components of harmonic radar can run well and have a good recognition for nonlinear targets.The sixth chapter summarizes the work of this paper.The shortcomings of the current work are put forward,and the direction of the improvement of the follow-up work is discussed.