Research On The Key Technology And Implementation Of Wideband Digital Receiver

EW(Electronic Warfare) receiver is the import part of the electronic detection system for radar signal, so it requires that frequency measurement must be high speed and precise in broad frequency band. Traditional analog receiver not only has low frequency estimation precision, but also bad resolution and processing capability at the multi-signals conditions, which is insufficient for practical requirements for frequency estimation. With the rapid development of digital signal processing theory, method and large scale integrated circuit technique, wideband digital receiver has become an inevitable trend of the development of electronic detection system. Digital receiver is capable to convert the input analog signal to digital signal, store the data in memories and adopt many excellent and agile digital signal processing methods, sequentially get more information from output digitized data. Therefore, the digital receiver has more advantages including large instantaneous bandwidth, high precision and high resolution. This dissertation focuses on studying the key technology and implementation of wideband digital receiver.Firstly, the theory model of digital receiver is analyzed. To consider the mismatch between the low operating speed of digital signal processor and A/D converter, two methods of converting data are introduced briefly: bandpass sampling and digital down conversion. Furthermore, several feasible digital receiver configurations are discussed: Undersampling multi-channel parallel digital receiver, digital channelized receiver and frequency -guided digital receiver.Secondly, frequency parameter measurement which is one of the key parameters in digital receiver is studied. Some sinusoidal signal frequency estimation methods are introduced. Several important algorithms of frequency measurement are analyzed in detail, and these algorithms can simultaneously process multi-signals, and frequency measurement performance is also simulated. This paper is focused on the research of high resolution spectrum evaluation MUSIC algorithm for frequency estimation based on multi-path delay structure. Because traditional MUSIC algorithm requires eigenvalue decomposition and high computational complexity, a MUSIC frequency estimation algorithm based on the Multi-Stage Wiener Filter (MSWF) is presented. The simulation results also have shown that MSWF-MUSIC algorithm achieve the asymptotic frequency estimation performance of the classical MUSIC method, but the computational complexity is reduced significantly, thereby this method is more suitable to the requirement of real time signal process in modern EW system.Thirdly, according to the characteristic of the digital channelized receiver, which must have the ability of processing the large number of data in real time, an efficient digital parallel analyzing system is studied in this paper, which adopts the polyphase filter technology to implement channelization, and its performance is analyzed, too. Based on coarse frequency measurement of polyphase filter banks, this paper adopts flexible algorithm to measure frequency in narrow band slowly and finely, including phase difference method, instantaneous autocorrelation method, the curve fitting method, the linear fitting method and the zero-crossing detection method. Based on these methods, signal environment and the requirements for the frequency estimation precision, the weighted phase difference algorithm used in further processing of fine measuring frequency in digital channelized receiver is presented, and it can get high measurement precision. Finally, the working processing of the whole receiver is described from mathematics model, then the system is simulated, and the performance is also analyzed deeply. Furthermore, a signal detection method of wavelet thresholding denoising based on simplex-simulated annealing algorithm is presented, it gives a new way for the future research on signal detection, and provides certain theoretical guidance for signal detection.Finally, the algorithms of polyphase filter and instantaneous frequency measurement (IFM) are realized on FPGA, and the prototype of the digital channelized receiver is also designed. Then every component design of the system is discussed in detail. In addition, the hardware testing of the digital channelized receiver is performed, a group of real and reliable experimental data is achieved, and satisfactory results are got. Thus, the digital receiver based on digital channelized IFM method has simple architecture, high real time performance, high frequency estimation precision, and is easy to be implemented by programmable logic device FPGA, which has practical engineering value.