scholarly journals A variable chirp rate stepped frequency linear frequency modulation waveform designed to approximate wideband non-linear radar waveforms

2021 ◽  
Vol 109 ◽  
pp. 102884
Author(s):  
Mahdi Saleh ◽  
Samir-Mohamad Omar ◽  
Eric Grivel ◽  
Pierrick Legrand
2020 ◽  
Vol 8 (6) ◽  
pp. 2753-2760

Since the advantage of pulse compression radar, the pseudo random codes and poly time codes and non linear frequency modulation has been mostly widely used low probability intercept (LPI) radar waveforms. By changing frequencies time to time in frequency modulation known as non-linear frequency modulation (frequency hopping (FH)), peak to side lobe ratio (PSLR) can be achieved to make less severe the covering effect of nearby targets and to improve the useful dynamic range. Adding an appropriate binary encoded ternary phase shift signal (PSK) as form as Binary encoded Hybrid-PSK/FSK (BEH PSK/FSK), the peak side lobe ratios are obtained very low values (e.g., PSLR<-70dB), similar to the antenna side lobes. In advanced microwave power amplifier technology, now a day’s using low peak to average power modules requires them to be amalgamated at the radio frequency (RF) stage in that way to obtain the required emitted radiated power. The deterministic waveforms are represents Noise waveform radar technology is a valid alternative. The pseudorandom waveform-realization of a noise process, the higher its bandwidth-time (or BT) product, the lower the (numerical) peak side lobe ratio. With practical Bandwidth-time values, the achievable peak side lobe using pure random is not sufficient the generated pseudorandom waveforms undergoes optimized genetic algorithm Hamming Scan (HS) to achieve optimized pseudo random (OBC), in order to achieve the desired side lobe level. This manuscript proposes a general analysis of the two modes of radar waveforms, i.e., Ternary and Binary alphabetic waveforms of coincidence detection.


2018 ◽  
Vol 18 (1) ◽  
pp. 27 ◽  
Author(s):  
Muhamad Ridwan Widyantara ◽  
Sugihartono ◽  
Fiky Y. Suratman ◽  
Slamet Widodo ◽  
Pamungkas Daud

Non Linear Frequency Modulation (NLFM) method can suppress the peak sidelobe level without additional windowing function. NLFM doesn’t require any weighting function because it has inbuilt one. NLFM has a variable frequency deviation function due to the relation between frequency and time of the signal which is not linear so that it is possible to suppress of peak sidelobe level. This paper studies the characteristic of various NLFM waveform, such as NLFM Tri Stage Piece Wise (TSPW), NLFM S, and NLFM Taylor. The study of Pulse Compression of NLFM waveform consists of three aspects. First, analysis of pulse compression performance. Second, analysis of background noise. Last, analysis of Doppler effects. The simulation is done using Matlab software. The lowest  value Peak Sidelobe Level (PSL)of NLFM TSPW is about -20 dB while NLFM S and NLFM Taylor are about -32 dB and -39 dB. Additive White Gaussian Noise (AWGN) and Doppler Effect influenced the value of PSL for each NLFM waveform. NLFM Taylor has the best NLFM waveform when the Doppler Effect and AWGN cause the value of PSL become high. Comparison between NLFM Taylor and Linear Frequency Modulation(LFM) is done in radar surveillance applications to analyze the detectability performance where the condition of Radar Cross Section (RCS) for each target has different significant value. The three targets are commercial airplanes, helicopter and fighter. For detectability performance, NLFM Taylor can detect more clearly than LFM conventional.


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