This paper is published in Volume-3, Issue-6, 2017
B. Shubhaker
Jawaharlal Nehru Technological University, Hyderabad, Telangana, India
Pub. Date
25 November, 2017
Paper ID
Matched Filter, Ambiguity Function, Autocorrelation, Peak Sidelobe Level, Polyphase Codes and Weighting Functions.


B. Shubhaker. Phase Coded Radar Signals – Frank Code & P4 Codes, International Journal of Advance Research, Ideas and Innovations in Technology,

B. Shubhaker (2017). Phase Coded Radar Signals – Frank Code & P4 Codes. International Journal of Advance Research, Ideas and Innovations in Technology, 3(6)

B. Shubhaker. "Phase Coded Radar Signals – Frank Code & P4 Codes." International Journal of Advance Research, Ideas and Innovations in Technology 3.6 (2017).


This dissertation presents an overview of phase-coded radar signals based on frank codes and p4 codes used in target detection techniques. For good range detection, high SNR is required. So matched filter is used in the processing of radar signals which maximizes the peak signal power to mean noise ratio. In this analysis, the ambiguity function plays an important role. Using ambiguity diagrams and autocorrelation functions, various waveforms are compared in terms of PSL (peak sidelobe level). Ambiguity diagrams are obtained by using MATLAB code. Primarily simple pulse has been taken but it has some drawbacks like poor range resolution, poor Doppler resolution, so pulse burst waveforms were taken and it has given better Doppler resolution than simple pulse with some range resolution. To improve the range resolution further, LFM (Linear Frequency Modulation) is used. The idea here is to sweep the frequency band B linearly during the pulse duration T. It provides better range Resolution. To reduce the sidelobe levels further Weighting techniques are used for LFM, the presented weighting techniques are Hamming and Hanning. Because of these weighting techniques, PSL is reduced by -14.4 dB but the resultant is range doppler coupling and sidelobes, as it is a drawback, NLFM (non-linear Frequency Modulation) is used which provides lower sidelobes when compared to LFM. In NLFM the method for shaping the spectrum is to deviate from the constant rate of frequency change and to spend more time at frequencies that need to be enhanced. NLFM provides the better sidelobe levels compared to the LFM, and the performance characteristics of the NLFM waveforms for sawtooth frequency coding are studied. NLFM waveforms are sensitive to Doppler frequency shift and are not Doppler tolerant. The major limitations are system complexity, limited development of NLFM generating devices and stringent phase control requirements. With short pulse, short-range target detection is done efficiently but for long range, detection resolution decreases. Hence, the research work proceeded to other waveforms with high duration but the drawback is range resolution. To improve the range resolution, pulse compression technique is used and this can be achieved by frequency coding and phase coding. In this dissertation phase coding is employed for pulse compression of the signals and it is of two types named binary phase codes and polyphase codes. For Barker code of length 7, a sidelobe level of -16.9 dB is obtained, Barker code of length 11, a sidelobe level of -20.82 dB and Barker code of length 13, a sidelobe level of -22.27 dB is obtained. Here the Barker code is limited to 13 and sensitive to Doppler shift. So to reduce the sidelobe level further Frank code has been introduced. Frank code is derived from Barker code and it is a square length sequence. The Frank code is derived from a step approximation to a linear frequency modulation waveform using M frequency steps and M samples per frequency. The Frank code has a length or processing gain of N_c=M^2. For a Frank code of length 16, a sidelobe level of -21.07 dB is obtained but this code is limited up to the maximum length of 139. P4 code belongs to polyphase code. It has no restriction on code elements, and are normally derived from the phase history of frequency modulated pulse generated, which is used for any length of the sequence and it has provided the sidelobe level of -31.4089 dB. It provides a better sidelobe level and Doppler resolution.