Research On Polarization Scattering Matrix Measurement And Pulse Encoding Technique In Radar

The polarization scattering matrix measurement is a fundamental part of polarimetric radar.Time-polarization measurement system needs at least two observation period,in which polarization scattering matrix has changed for some target. Instantaneous polarization scattering matrix measurements just need an observation period to give the target polarization scattering matrix. Accordingly, instantaneous polarization measurement method gradually developed and perfected. On the other hand, adding polarization information to radar signal can enhance the ability to suppress interference and detect signals. The research of the combination radar signal with polarization information is a trend in radar waveform design,such as polarization encoding-LFM signal, polarization encoding-phase encoding signal and polarization encoding-frequency agility signal.In the aspect of instantaneous polarization measurements, the papper firstly gives the instantaneous polarization scattering matrix estimation algorithm based on DTFT for the dual-band pulse signal, analyzes the characteristics of echo signals in the frequency domain under various circumstances of polarization scattering matrix and gives the measured step. This method is the complementary of DTFT estimation algorithm proposed by Wang Xuesong. The latter only analyzes when the main polarization component is greater than the cross-polarization component. Different kinds of polarization scattering scattering matrix are measured and the curves which measurement error varies with the change of SNR and pulse width are simulated by computer. Then we use polarization encoding-phase encoding signal and polarization and frequency agility signal to measure the transient target polarization scattering matrix by the method based on inverse transformation of instantaneous polarization ambiguity function matrix(IP-AFM). Comparing with the traditional polarization measurements proposed by D Giuli, this method’s stability is better and the measurement error is smaller in different signal bandwidth and pulse width.In the aspect of polarization and frequency agility signals, mathematical expressions and time-domain waveform of some polarization and frequency agility signals are given. Ambiguity function is used to analyze their delay and frequency resolution. Then we use polarization matching and pulse accumulation to process echo signal and find when the differences of polarization state between target and interference are larger, both signal to interference ratio and signal to noise ratio can be greatly improved, otherwise only the signal to noise ratio is improved and the signal to interference ratio isn’t improved.Finally the papper gives influence of target polarization characteristics to detect target by polarization encoding-phase encoding signal and polarization and frequency agility sinal. Then we use the target polarization scattering matrix measured by the previously mentioned methods to compensate target echo signal, thus the ability to detect target decreased by polarization scattering characteristics is increased.