Research Of OFDM Cognitive Signal Design Based On Spectrum Constrained

OFDM signal is widely used in communication systems because of its high transmission rate,excellent anti-interference ability and easy implementation.Because of high spectrum utilization,it is also generally studied in cognitive radios.At the same time,OFDM signal also has good performances in radar detection filed.The shared signal based OFDM can obtain good results both in radar and communication performance.However,in the increasingly crowded electromagnetic spectrum,the spectrum of electromagnetic waves cannot be fully utilized,and the interference between different electromagnetic devices becomes stronger and stronger.In order to solve this problem and adapt to the actual situation of modern electronic warfare preferably,the problem can be modeled by using spectral constrained conditions.The free spectrum can be dynamically selected according to the characteristics of the external electromagnetic environment to avoid the problems of interference and spectrum resources sharing.Therefore,this paper studies the method of OFDM cognitive signal design based on spectrum constraint,aiming to avoid the interference while achieving the sharing of radar and communication.The main work of this thesis is as follows:1.The first part researches the basic principles of OFDM signals and the framework of an integrated system of radar and communication.Based on this,the principle of communication and detection of the signal is analyzed.Through the simulation analysis of multiple algorithms,it is further verified that the above algorithms are effective in suppressing PMEPR.2.In terms of the spectrum compatibility and interference among different users,an OFDM shared waveform design method based on spectrum nulling modulation is put forward.The communication modulation is realized by spectrum constraint.The Peak Side-lobe Level Ratio(PSLR)is optimized through the optimization problem,and the joint optimization problem considering PSLR and PMEPR is further proposed.In demodulation part,a minimizing sub-band energy method is proposed,which can effectively realize radar detection and communication data transmission functions.3.In order to solve the problem of higher peak envelope of OFDM and ensure its effective transmission rate,the OFDM shared waveform design based on partial carrier modulation is proposed.In addition,this paper researches a waveform design method aiming at PMEPR optimization,and on this basis,a mismatch filter is designed to ensure a low PSLR of the signal at the receiving end.This algorithm can not only suppresses the high side-lobes,but also smooth the signal envelope effectively.