Study, Based On Labview Software Radio Modem And Signal Recognition Technology

The basic idea in this paper is to realize the non-real-time processing of automatic modulation recognition and modulation-demodulation of communication signals in the way of software (LabVIEW ) based on the software radio.Based on decision theory, the automatic modulation recognition of basic styles (DSB,PM,FM,2ASK,2FSK,2PSK) is studied ,founded on decision recognition tree scheme. A automatic modulation recognition module is established by LabVIEW to accomplish a simple and effective recognition. Two typical software radio fuze signals—PRCPM (pseudo random code phase-modulation of m sequence) and LFM (linear-frequency modulated of saw-tooth-wave modulation) is added to the signal recognition space, considering that the task of this dissertation is derived from a practical research project for some software radio fuze jammer. Then PRCPM and LFM can be identified by the same modulation recognition module via expanding recognition tree and setting signal parameters so as to all the signal referred can be incepted by the fuze jammer. In this paper we study deeply the PRCPM recognition by detecting autocorrelation peaks and LFM recognition by finding the number of peaks of Wigner-Ville(WVD) distribution spectrum over some threshold.The thesis goes deep into the study on the general platform of the analog and digital communication signal modulation and demodulation based on the software radio, and on this foundation we can calculate the modulation and demodulation arithmetic of signals such as DSB,FM,,PM,2ASK,2FSK and 2PSK. We also carry on simulations on the arithmetic by LabVIEW, so we can prove its correctness and feasibility. The modulation and demodulation of PRCPM and LFM are given a special discuss, especially for LFM. LFM can be demodulated by the same arithmetic as for FM, and the demodulated signal takes on the shape of saw-tooth-wave and the period of LFM can be estimated while modulation slope can't because of arctan operation. Via autocorrelation, the periods of LFM and PRCPM can be estimated and when SNR is bigger than OdB, for single component LFM, by estimating peaks of WVD distribution we can obtain LFM instantaneous frequency as to estimate the center frequency and also its modulation slope .