Research On The Key Technology Of Digital Wideband Receiver Based On Cognitive Radio

With the development of modern warfare informatization,the frequency of electromagnetic spectrum in electronic warfare has become increasingly tense.In order to make rational use of spectrum resources,electronic warfare systems need to have strong cognitive abilities in the radio environment.Among them,wideband receivers,as an important device for cognitive reconnaissance rings,face an increasingly harsh electromagnetic environment,and its ability to adapt to the environment becomes the key to performance improvement.Due to the development of digital signal processing technology and large-scale integrated circuits,digital wideband receivers have greatly improved signal processing accuracy,instantaneous bandwidth,and multi-signal processing capabilities compared to conventional analog receivers,becoming the inevitable trend of electronic receiving system development.Therefore,based on the previous research,this dissertation focuses on the key technologies of digital wideband receivers.Combined with engineering practice,this paper designs and implements an efficient FPGA-based wideband receiver architecture.For the wideband receiver system,the time-frequency analysis of frequency-hopping signals is analyzed and discussed.The specific research content includes the following points:1.The theoretical model of wideband digital receiver is studied.Aiming at the contradiction between high speed ADC acquisition speed and low backend data processing speed in the architecture,a data rate conversion method is introduced,namely band pass sampling technology.By analyzing the polyphase filtering technology,the filter bank structure in traditional multi-rate signal processing is improved,the computational complexity is reduced,and the design theory of the best original filter in digital wideband receiver is studied.2.Design and implementation of a digital wideband receiver system based on a polyphase filter structure.To achieve the goal of full-broadband signal reception,the channel division method was studied and analyzed.Combining the advantages of parallel computing in FPGA,the hardware implementation of the module such as high-speed data acquisition,branch extraction,butterfly operation and data buffering in the receiver has been completed,and it has been successfully debugged and verified.3.For the problem of low dynamic range and sensitivity in wideband receivers,the importance of automatic gain control is analyzed.The common AGC structure is compared and analyzed,and a feedforward digital AGC structure suitable for wideband receiver is designed and implemented.The contradiction between the filter performance and the convergence speed of the loop is discussed in detail.The appropriate parameter settings are selected in the engineering verification.This module improves the problem that normal analysis cannot be performed because of weak signal characteristics.4.The problem of time-frequency analysis of frequency-hopping signals under wide-band receiving system is studied.A variety of time-frequency diagram extraction methods are compared,and the advantages and disadvantages of its engineering implementation are analyzed.According to the shortcomings of the existing time-frequency diagram extraction methods,two time-frequency diagram correction methods are proposed,and their noiseresistance performance is improved.Finally,the performance of frequency-hopping signal detection and parameter estimation is verified by the simulation analysis and modification method,which verifies the effectiveness of the method.