Research On Some Techniques For The Digital Receiver And The Corresponding System Implementation

Due to worse electromagnetic environments where modern electronic receiving devices often work , analog receiving systems with worse anti-jamming abilities and agility unable to adjust. After 1980's, in order to utilize fully the digital processing techniques with higher reliability, better anti-jamming ability and agility , analog receiving systems are digitized gradually. And at the beginning of 1990's, the software radio is proposed. However, it is a tradeoff project to develop digitized receivers because of the limitations of analog-to-digital converter(ADC), digital signal processing(DSP), etc. Therefore, it's significant to develop highly effective wideband digital receivers, which can be used to digitize the wideband communication receiving systems, improve the performance of the communication receiving systems such as Radar, Telemetry, etc, and implement the desired receiving systems based on software radio.,At present, many key techniques including extending dynamic range of the receivers, highly effective wideband digital downconversion (DDC), real-time highly effective digital coherent demodulation, etc, are needed to be developed in the digital receivers. Research, in this dissertation, concentrates mainly on the digital automatic gain control (AGC) technique, the highly effective digital wideband receiver structure with high-speed, high-resolution, the real-time digital frequency demodulation technique, the opened-loop frequency trace technique used in FM demodulation, and the design and implementation of PCM/FM Telemetry IF Digitized Receiver and wideband Radar digital receiver, etc.The main creative points in this dissertation are as follows:1) The digital AGC technique is described in the dissertation, and an highly effective digital envelope demodulation method , which is carried out by absolute value operation, instead of multiplication, and Cascaded Integrator-Comb (CIC) or slip maximum without any multipliers, is proposed .The digital AGC based on this technique is highly effective, which is significant to wideband digital receivers with high-speed. No paper, with regard to detailed analysis of two highly effective digital envelope demodulation methods in this AGC loop, has been found available on known publication.2) The highly effective digital receiver structure is discussed, and an highly effective structure of polyphase decimation filter is presented, as well as an highly effective wideband digital receiver structure with high-speed and high-resolution by combination of polyphase filtering structure and muti-ADC (analog-to-digital converter) parallel acquisition structure with high-resolution, and then a measure for improving performance is analyzed in detail. This structure is very useful to break through some recent bottlenecks of digital processing technique, and implement faster and more highly effective digital receivers.3) During the research on highly effective and real-time digital frequency demodulation technique, a highly effective digital frequency demodulation method, based on Coordinate Rotation Digital Computer(CORDIC) algorithm and first-order difference, has been given, which makes a large number of ROM fill avoided by real-time computing phase with respect to I and Q through pipe-line structure. This method, with advantages of high-resolution, high-speed, simple structure, etc, only needs simple adders and shifters, so which can be used in the many fields.4) During the research on the opened-loop frequency trace technique used in FM demodulation, a new technique to remove doppler frequency and carrier frequency bias in PCM/FM telemetry system is put forward by breaking up the closed-loop phase-locked structure, which simplifys the design of PCM/FM telemetry IF digitized receiver and shortens response time. No paper, with regard to detailed analysis of the opened-loop frequency trace technique based on DPLL, has been found available on known publication.5) A PCM/FM...