An Fmcw Radar Range / Doppler Processing And Beam Forming Technology

With the development of detecting technology of radar, there are more and deeper demands of radar performance for the valid distance and the resolution. Linear frequency modulated continuous wave(LFMCW) signal is usually used by HF radar such as skywave Over-The-Horizon radar(OTHR),surface wave OTHR, and so on. The radar used LFMCW signal can detect the information of range and Doppler frequency of target. The adaptive digital beamforming(ADBF) is a good method for control external interference and noise. It can adaptive adjust weights to array antenna according to the distribution of interference and make the received power of interference and noise from antenna least.This paper analyzes the LFMCW signal used in HF radar and bring forward two methods of measure range, which are method of removing slope and method of digital pulse compression. For the former method, the paper deduces the expression of beat frequency and the formula for range/Doppler processing using two-dimensional fast Fourier transform(FFT) technique. For the latter method, the paper provides analysis of match filter and digital pulse compression. The technique that the range/Doppler processing and the adaptive digital beamforming(ADBF) combined to extract the information of target echoes while control the effect of interrupt and noise is the emphases in this paper. That is done as following: getting the information of target azimuth through the antenna composed beam scan; controlling the power of interference through adjusting the weights; obtainning range parameter through processing the time delay of target echo; acquiring Doppler information by coherently processing some number of frequency sweeps. Either one-dimensional or two-dimensional DFT's have been used to carry out this processing. In addition, the window functions are applied both in range and in Doppler for sidelobe control. Increasing coherent integration time (CIT) can improvement the frequency resolution. The computer simulation results in deferent situation are provided in this paper. The last chapter of this paper gives considerable attension to the part of the radar simulation system design, which is Design of PCI-based Data Transmission Card.This card used as computer adapter between PC and signal processing card and is suitable for high-speed continuous data transmission. This part introduces the design method and structure of PCI, the logic in CPLD, and the development of PCI based device driver.