A STAP overview

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I. INTRODUCTION Moving target indication (MTI) is a common radar mission involving the detection of airborne or surface moving targets. The signal-to-noise ratio (SNR)–a characterization of the noise-limited performance of the radar against a target with radar cross section (RCS) ¾T at range r–is approximated as ! Ã ¶ μ Ae Gsp Pt Gt (Á, μ) ³ ¾T ´ SNR(Á, μ) = 4¼r2 4¼r2 Nin Fn Lrf

A STAP Overview WILLIAM L. MELVIN, Senior Member, IEEE

(1)

This tutorial provides a brief overview of space-time adaptive processing (STAP) for radar applications. We discuss space-time signal diversity and various forms of the adaptive processor, including reduced-dimension and reduced-rank STAP approaches. Additionally, we describe the space-time properties of ground clutter and noise-jamming, as well as essential STAP performance metrics. We conclude this tutorial with an overview of some current STAP topics: space-based radar, bistatic STAP, knowledge-aided STAP, multi-channel synthetic aperture radar and non-sidelooking array configurations.

where Pt is peak transmit power, Gt (Á, μ) is antenna gain for direction (Á, μ), Ae is the effective receive aperture area, Gsp represents processing gains, Nin is the input noise power, Fn is the receiver noise figure and Lrf represents radio frequency (RF) system losses [1]. Assuming the noise is uncorrelated (white) and Gaussian, the probability of detection (PD ) is a one-to-one, monotonic function of both SNR and the probability of false alarm (PFA ). By maximizing SNR, the processor maximizes the probability of detection for a fixed probability of false alarm. In light of (1), the radar designer ensures detection of targets with diminishing radar cross section at farther range by increasing power-aperture Pt Ae . System constraints and cost limit the deployable power-aperture product. Radar mounted on aerospace platforms must also mitigate the otherwise deleterious impact of ground clutter returns and jamming on moving target detection. We collectively refer to clutter and jamming as interference. Assuming Gaussian-distributed interference, PD depends on both signal-to-interference-plus-noise ratio (SINR) and the specified value of PFA in a manner analogous to the white noise detection scenario. Since SINR · SNR, interference always degrades detection performance in comparison with the noise-limited case. Fig. 1

Manuscript received March 17, 2003; revised June 23, 2003. Refereeing of this contribution was handled by P. K. Willett. Author’s address: Georgia Tech Research Institute, Sensors & Electromagnetic Applications Laboratory, 7220 Richardson Rd., Smyrna, GA 30080, E-mail: (bill.melvin@gtri.gatech.edu).

c 2004 IEEE 0018-9251/04/$17.00 ° IEEE A&E SYSTEMS MAGAZINE VOL. 19, NO. 1

Fig. 1. Receiver operating characteristics for non-fluctuating and fluctuating targets.

shows the receiver operating characteristic (ROC) for non-fluctuating and Swerling 1 targets; the abscissa corresponds to output SINR. This figure clarifies the

JANUARY 2004

PART 2: TUTORIALS–MELVIN

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