Estimation of Modulation Parameters of LPI Radar Using Cyclostationary Method
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Estimation of Modulation Parameters of LPI Radar Using Cyclostationary Method Raja Kumari Chilukuri1,2 · Hari Kishore Kakarla1 · K. Subbarao3 Received: 29 May 2020 / Revised: 24 August 2020 / Accepted: 23 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Low Probability of intercept (LPI) radars work on the principle of low peak-power and wide bandwidth. To achieve this, the LPI radars use special type of modulated waveforms which are difficult to intercept. The main tasks of intercept receivers are to detect, estimate and classify LPI signals even in the presence of high noise. Accurate estimation of the modulation parameters also provides information about threat to radar so that necessary counter measures could be initiated against the enemy radars. In the present work, Cyclo-stationary (CS) method is used to estimate the parameters of Polytime coded LPI signals. CS method is efficient for the analysis of periodic waveforms like LPI signals and finds applications in many fields such as array signal processing, estimation of direction of arrival, signal detection. Cyclic auto correlation function and the spectral correlation density function (SCD) which are the basis for CS analysis are computed for all the four types of polytime codes. Generation of all the four types of Polytime codes and computation of SCD coefficients are carried out using MATLAB. From the contour plot of SCD function, the parameters carrier frequency, bandwidth and code rate are measured. It is assumed that the received signal is not corrupted with any noise. The simulation results are compared with the values available in the literature. The maximum error of estimation is well within ± 6% for all the codes in the proposed method whereas the maximum error reported in the literature is 25.7%. Hence the proposed method is better. Since CS method is sensitive to sampling frequency, the analysis is repeated for three different sampling frequencies and in all cases, the estimation error is less than 6%. Keywords LPI radar · Polytime codes · Cyclo-stationary (CS) · Cyclic auto correlation function (CACF) · Spectral correlation density (SCD) · Auto-correlation function (ACF) · Fourier transform (FT) and code rate (Rc)
* Raja Kumari Chilukuri [email protected] Extended author information available on the last page of the article
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Sensing and Imaging
(2020) 21:51
1 Introduction A low probability of identification (LPID) and a low probability of intercept (LPI) are two important tactical requirements of any radar. The property of LPI radar is that, due to its low power, wide data transfer capacity, frequency fluctuation, or other design aspects, makes it hard for it to be distinguished utilizing a passive intercept receiver. A LPI radar uses a special emitted waveform intended to prevent a non-cooperative intercept receiver from intercepting and detecting its emission. It transmits a low power intra-pulse tweaked waveform so that the identified object i
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