| The Radar waveform generation system is one of the key components of Rader. With the development of modern digital technology, digital technology have been widely using in the radar waveform generation system, while in practical applications, typically been used to generate wideband radar signals, it need supplemented by some spread spectrum methods. On the other hand, considering each of the circuits of the system and the electrical elements are not ideal, no matter what kind of methods the system takes,just depend on the hardware we cannot get the high-performance radar signals directly. Therefore, in order to generate high-performance radar signals, researching the process of distortion correction of the Radar waveform generation system is significant.Taking LFM signal as a model in this paper, and the waveform generation system is based on the direct digital waveform synthesis method, combining with the analogue quadrature modulating method and frequency multiplication method for widening frequency band. Based on the analysis on the system of amplitude and phase errors, study the method of extracting amplitude and phase distortion in the case of noise effects, and proposes the digital correction method of amplitude and phase distortion error.The main works of this paper are:1. At first, the paper analysis the errors sources about the direct digital waveform synthesis(DDWS), quadrature modulator and frequency multiplier chain. How the various kinds of error factors affect the quality of the generated linear frequency modulation signal and the performance of the LFM signal pulse compression by modeling and simulated on the computer.2. Digital compensation methods for distortions of the radar waveform generation system are analyzed sytematically. Based on the linear system theory,the principle and the feasibility of the digital compensation for waveform systems are analyzed. Considering that the extraction of system’s distoritions is the foundation to realize the correction of the errors, two methods to extraction are researched,and the two methos are directly spectrum comparison method and the related windowing method. Through the simulation comparison, considering the effect of noise and other nonsystematic errors,select the relevant window as the optimized extraction method.3. Based on the extracted waveform system characteristics on amplitude and phase distortion, design FIR filter for correction of the system’s amplitude and phase distortion. As the transfer function of the system distortion does not have the character of conjugate symmetry, the problem transforms to designing of complex coefficient FIR filters according to the specific amplitude and phase characteristics. Therefore discuss the method of design complex coefficients FIR filters using the generalized Remez technology. Finally, using the correction filter realizes the compensation and the simulation experiment can be viewed that the amplitude and phase distortion is improved. |
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