Research On Non-linear Frequency Of Synthetic Aperture Laser Radar Signal

Non-linear frequency of Synthetic Aperture Laser Radar signal is studied in thisdissertation, the main works of this dissertation are as follows:1. From the concept of Synthetic Aperture Laser Radar, the synthetic apertureprinciple is analyzed and the signal models of Synthetic Aperture Laser Radar areestablished in this dissertation. Also the focusing signal processing of SAL is analyzedin detail and the actual SAL azimuth resolution and SNR are derivatized.At the sametime, principles, characteristics and the qualifications of the laser heterodyne detectionsystem are introduced.2. The ideal Linear Frequency Modulation signal (LFM) in the time domain,frequency domain and the corresponding domain’s matched filtering techniques areanalyzed. SAL compression with multiple point targets and various factors affectingSAL imaging resolution are numerical simulated.3. Based on the linearity’s definition of Non-Linear Frequency Modulation signal(NLFM), take Polynomial Non-Linear Frequency Modulation signal (PPS) whichcommonly used in radar imaging for example, the Fourier transform of LFM andNLFM and SAL compression under different linearity are simulated.4. To obtain larger time-bandwidth product, most of the laser using the way ofLinear Wavelength Modulation instead of Linear Frequency Modulation, this can leadto non-linear frequency. Theoretical analysis and numerical simulation of the IF signalfrequency broadening and SAL-echo responses changing after the introduction ofnonlinear frequency are done. SAL image resolution changing at-3dB and-10dB areanalyzed in detail. Also, non-linear Frequency of Synthetic Aperture Laser Radar arecorrected by using matching reference channel technology and non-matching referencechannel technology. Advantages and disadvantages of these two algorithms arecompared. Then the changing of SAL imaging’s resolution before and after correction issimulated in different distance. Form the simulation results; we can see that the imagingresolution improves greatly after the non-linear frequency correcting.