Based On Software Radio Technology Radar Digital If Design

In this paper, we analysed intermediate frequency receiver of the xxx radar produced by xxx factory. With the imports SDR (Software Defined Radio) technique, we provided a improved design of the digital intermediate frequency receiver for the system performance. Also, we analyzed the signal processing system and information processing system afrer the intermediate frequency receiver。The xxx Radar is a full coherent radar. The echo of the radar is amplifiedand filtered in the high frequency channels. After that, the echo will be transferred into intermediate frequency. After the 30MHz signal be amplified in intermediate frequency and compressed by pulse,it will be inputted in orthogonal channels and produced 2-ways orthogonal analog video signals. Then be transferred into signal processing system and data processing system. SDR is current in modern communication technology. It is good to make system flexible and open via signal sampling quantization and software processing. In the first several chapters, how to design the whole system framework and how to choose A/D converter for exerting the advantage of the digital signal processing compared with analog signal processing and restraining the disadvantage of the system if provided. In order to augment the linear dynamic range of the system and avoid the over loading, based on intrinsic clutter image of the analog system, it designed DAGC (Digital Automatic Gain Control) System. In this system, we can change the gain of IFA (Intermediate Frequency Amplifier) on time and restrain the over loading via extracting the digital sequence exported in A/D converter and the information in signal processing system. At the same time, it designs the digital orthogonal channels for digital mixing and filtering. We can choose right SF (Sampling Frequency) to keep 2-ways digital benchmark signals orthogonal and amplitude consistent absolutely. In the seventh chapter, the method about how to process digital signal,estimate the target existing or not and extract information of the target (i.e distance, orientation, altitude and velocity) if provided.For example, how to detect dynamic target and filter low rate clutter; how to avoid blind speed; how to set threshold in noise and clutter environment to keep constant false alarm; how to do the digital range finding for determinate target; how to save and track the targe which detected by system, etc. In the eighth chapter, it describs something about improving system and basing on xxx radar system to design software radar.