Study Of Stabilization Technique Of Active Filter In The Measurement System Of Laser Radar Cross Section

The Light Detection and Range(LIDAR)combines laser technology and radar technology. It has high resolution, strong anti-interference capability, and the ability of three-dimensional imaging. It is usually used for ranging, angle measurement, precision tracking, sensing fuses,the spacecraft navigation, meteorological measurements and so on. It is of great value in both civilian and military applications.Firstly, the physical meanings of laser radar cross section are analyzed and the principles and methods for its calculation and measurement are presented. Based on the theoretical definition of laser radar cross section, the general laser measurement equation in which the target is characterized with its laser radar cross section is derived. To obtain the measured data of laser radar cross section more accurately, spatial filtering is utilized to improve the SNR of receiving system and to exclude the interference of background and noise.In the second, the content of this dissertation is how to design a biquadratic active band pass filter for the measurement of laser radar cross section. The basic theory of biquadratic active filter is also analyzed in this thesis, with the focus on the design method of the biquadratic active band filter. Then, the the sensitivity of the performance of the filter on the RC component values and integrated operational amplifier’s gain is discusses in the biquadratic active band pass circuit. According to the parameters obtained, the biquadratic active band filter is simulated.Finally, we propose the strategy and principle for what the center frequency drift occurs when the temperature changes, and introduces its control method comparatively including junction field effect transistor, analog switch, resistor network and digital potentiometer, emphatically introduces the programmable gain system based on digital potentiometer AD8400. The band pass filter with programmable gain amplifier is designed and its performance and main parameters are examined through numerical simulation and experiment. The results of the test showed that the bandwidth of filter is 22 Hz and the center frequency of the filter can be changed automatically in real time, the demand of practice is satisfied.