The Intermediate Freguency Digital Receiver Baseband Design And Implementation

In modern aerospace measurement and control tasks, as a cooperative control target of the answering machine, with the ground station in the spacecraft control answering machine technology the research to have the important meaning. Along with the development of the Large Scale Integration and digital signal processing technology, the software radio technology is also applied to the satellite TT&C, it’s characteristic such as digital and scale are helpful to reduce the bulk, weight and power of satellite. The software radio technology has become an important direction of the development of communication system. The spread spectrum replier will be more miniature and more integration, the software radio technology will play an important role in the aerospace TT&C equipments. Therefore, the research of the IF digital processing module which is adopted in TT&C system will have important significance.The main content of this paper is IF digital receiver’s baseband module. It describes that the basic operation principle and the key techniques, including digital down conversion (DDC), sampling rate alteration and spread spectrum signal demodulation technique. Combining with the characteristics of aerospace TT&C system, we design a general hardware platform for intermediate frequency signal processing based on FPGA. This platform is mainly composed of A/D, FPGA minimal system, interface circuit and power supply conversion circuit and so on. The main function of the hardware circuits mainly adjusts the power of the IF analog signals and then does the digital processing to send the digital signal to FPGA for demodulation and finally output the demodulation data. The main functions of this platform are implemented on FPGA through software program, the main achievement features include DDC、decimation filter、 carrier acquisition and tracking、BPSK subcarrier demodulation and spread spectrum demodulation.The paper does a detail description for design principles、module interface and simulation results in detail.Compared with traditional analog communication equipments, the newly designed circuit has perfect performance through testing. The new circuit has the advantage of fast acquisition under low SNR, high-resolution, high-reliability, high anti-interference ability and flexibility, and overcome the shortcomings of temperature excursion and gain instability. Through optimizing and upgrading the software, it may implement the requirements of multifarious TT&C task, it has a comprehensive application future.