Mitigation of sidelobe clutter discrete using sidelobe blanking technique in airborne radars

Narasimhan, RS and Vengadarajan, A and Ramakrishnan, KR (2018) Mitigation of sidelobe clutter discrete using sidelobe blanking technique in airborne radars. In: 2018 IEEE Aerospace Conference, AERO 2018, 3 - 10 March 2018, Big Sky, pp. 1-12.

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Abstract

In this paper we propose a clutter suppression technique to blank antenna sidelobe clutter impulses in an airborne pulsed Doppler radar. In such radars the clutter leaks from strong scatterers on ground entering through antenna sidelobes will have different Doppler from mainlobe clutter Doppler due to platform motion. These returns will leak as target detections and adversely impact radar performance. These returns could be identified and blanked by sidelobe blanking (SLB) technique. In this paper a novel approach for SLB to eliminate clutter detections due to antenna sidelobes has been developed and evaluated. In airborne radar low inter-cardinal sidelobe level is essential to obtain noise limited detection in Doppler regions where the returns from antenna sidelobes lie. The conventional SLB technique using single element guard antenna does not work as the sensitivity loss in the guard channel is high (approx. 15dB) compared to main channel due to guard antennas high intercardinal sidelobe level. Thus many sidelobe detections from cardinal sidelobes of main antenna get undetected in guard channel and blanking cannot take place. In this paper we discuss a novel approach to sidelobe blanking which offsets the above difficulty to a large extent. The approach utilizes sub-arrays as guard channel for blanking sidelobe detections from sum channel. Generally the main antenna is divided into four quadrants to enable monopulse processing. Further the amplitude tapering is applied in receive to control antenna sidelobes of sum pattern which is the sum of four quadrants. Here we exploit the feature of quadrant antenna pattern which has less gain than sum pattern by at least 6dB in the mainlobe region, but has sidelobe levels marginally higher than sum in other regions. The sidelobes of quadrant pattern is slightly higher because of incomplete amplitude taper (half window taper). Thus quadrant pattern presents a tight upper bound to the sum pattern even in inter-cardinal region unlike single element guard which is loose upper bound. Due to this the sensitivity loss in quadrant channels is quite low (approx. 2dB). The approach harnesses the already available front end electronics. Simulation studies show that the proposed approach effectively blanks the detections from antenna sidelobes compared to conventional SLB, especially for clutter leaks from main antenna's cardinal sidelobe region. Through Simulations we establish the robustness of the approach in presence of residual errors in antenna collimation.

Item Type:	Conference Paper
Publication:	IEEE Aerospace Conference Proceedings
Publisher:	IEEE Computer Society
Additional Information:	The copyright for this article belongs to the IEEE Computer Society.
Keywords:	Clutter (information theory); Doppler radar; Echo suppression; Radar antennas; Radar clutter; Tracking radar, Amplitude tapering; Clutter suppression; Front end electronics; Monopulse processing; Radar performance; Side-lobe blanking; Side-lobe clutters; Simulation studies, Antenna lobes
Department/Centre:	Division of Electrical Sciences > Electrical Engineering
Date Deposited:	10 Aug 2022 09:56
Last Modified:	10 Aug 2022 09:56
URI:	https://eprints.iisc.ac.in/id/eprint/75506

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