The Design Of DDC And Research Of Fast Estimation Frequency Of Communication Reconnaissance Receiver

The continuous developments of modern communication technology and the more complicated electromagnetic environment have made it crucial to design wideband, digital, multifunctional software electronic reconnaissance equipment. The digital signal processing has drawn wide attentions in the engineering area and provides an idea development mode for electronic reconnaissance system, which is different frm the communication system in its wide-band processing. At present, the mismatch between the high-speed data flow of the wideband A/D converter and processing capability of the general DSP hinders the digitization of the electronic reconnaissance system most. On the other hand, the fast developments of micro-electronic technology and the wide applications of FPGA made digital circuit design more effective and afford an available method to resolve the mismatch between high-speed A/D converters and DSP chips.In this paper ,the structure of Polyphase filter is applied to the circuit of the wide-band Intermediate Frequency(IF) Digital Down Conventer(DDC) of ECM receivers,the emulation circuit of IF digital processor of full-probability ECM receiver is designed with FPGA. The simulation result proves the emulation circuit is feasible.In this paper some fast frequency estimation methods for single sinusoidal signal and two sinusoidal signals are analysed .A fast estimation frequency method basing on instantaneous correlation function for single sinusoidal signal is put forward in this paper,and the simulation is finished.As a result, the method has much quantity of operation speed. This paper focuses on the estimation frequency method of multisignal in order to satisfy the demand of reconnaissance multisignal in ECM,and gives the simulation result.This paper analyses the frequency estimation methods for Direct Sequence Spread System(DS) signals for respondence to the extensive ues of DS in communication.A method for estimation frequency of DS signals is brought forward because of it's sharp self correlation ant mutual correlation.The main idea of this method is to add the self correlation function and to eliminate the effects of noise.The simulation result proves the method is feasible.