Research On The Signal Waveform Of Low Probability Of Interception Radar

On the modern battlefield, radar faces electronic attacks and threats from anti-radiationmissiles increasingly severely, so stealth of radar signals is essential for radar. There aremany ways to achieve characteristics of low probability of intercept radar in whichwaveform design of the radar signal plays a key role.In this paper, the definition of low probability of interception radar is proposed. Thetheoretical formulas of radar intercept factor is derived in detail to analyze the factorsaffecting the performance of low probability of interception radar, in order to come up withthe characteristics for reaching LPI radar waveform. The main tool of radar waveformdesign is introduced and an overview of the characteristics of ambiguity function has beenpresented. Then numerical algorithm of ambiguity function is put forward.Firstly, for typical single-modulated signal waveform research, the time and frequencydomain characteristics, time-bandwidth product and ambiguity functions of LFM and two-phase encoded signals, etc., are analyzed. The Doppler effect of LFM signal and two-phaseencoded signals are analyzed and the impact of the Doppler shift on pulse output of chirpsignal and two-phase encoded signal after pulse compression is verified by simulation.The conclusion is drawn that chirp and two-phase encoded signal waveform has its ownadvantages and disadvantages. The coding format of multiphase encoding Frank, P1, P2, P3and P4and phase characteristics of poly-phase encoded signals are described, and it isverified by computer simulation. Focusing on the characteristics the low probability ofintercept radar waveform of Frank and P4poly-phase coded modulation, the ambiguityfunction formulas is deduced in detail and having better low interception performance canbe drawn by simulation waveform diagram here when compared to the two-phase encodedsignals. But it is sensitive to Doppler shift, characteristics improvement of signal waveformis analyzed after Doppler compensation. Costas frequency coding signal is also analyzed,including the coding structure way of the signal waveform, time and frequency domaincharacteristics and ambiguity function of the signal. The signal waveform can obtain morestrong performance of low interception.Secondly, signals of low probability of interception radar from low single modulationcan easily be intercepted by the enemy interception receivers. Starting from the signalwaveform, the low intercept radar signal waveform of LFM and7bits barker code (LFM-BC) simultaneously modulated is studied. Through theoretical derivation and numerical simulation, analysis of the radar signal is discussed mainly in the time and frequencydomain signal form, characteristics of the matching process, the ambiguity function, timeand frequency shift joint parameter estimation and low interception characteristics.Finally, two new combination waveform of complex modulation waveform is proposedthrough a combination of phase-coded waveform and frequency encoding waveform.Researching target resolution, distance and velocity ambiguity function on these two radarsignal waveform shows that the new radar waveform has larger and wider bandwidth radarsignal than a single modulated signal waveform, which has better low interceptioncharacteristics. The existing surveillance methods of reconnaissance plane are analyzed, thespecific process of dechirp and cyclic spectrum to intercept and capture is given, stealthcharacteristics of the LPI waveforms is studied in the paper by corresponding comparison,and stealth characteristics of waveform can be achieved with the complex modulationsignals.