A signal processing view of strip-mapping synthetic aperture radar

Munson, D.C., Jr.; Visentin, R.L., "A signal processing view of strip-mapping synthetic aperture radar," Acoustics, Speech and Signal Processing, IEEE Transactions on , vol.37, no.12, pp.2131,2147, Dec 1989. doi: 10.1109/29.45556

Abstract: The authors derive the fundamental strip-mapping SAR (synthetic aperture radar) imaging equations from first principles. They show that the resolution mechanism relies on the geometry of the imaging situation rather than on the Doppler effect. Both the airborne and spaceborne cases are considered. Range processing is discussed by presenting an analysis of pulse compression and formulating a mathematical model of he radar return signal. This formulation is used to obtain the airborne SAR model. The authors study the resolution mechanism and derive the signal processing relations needed to produce a high-resolution image. They introduce spotlight-mode SAR and briefly indicate how polar-format spotlight processing can be used in strip-mapping SAR. They discuss a number of current and future research directions in SAR imaging

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Wide-angle radar imaging using time-frequency distributions

Lanterman, A.D.; Munson, D.C., Jr.; Wu, Y., "Wide-angle radar imaging using time-frequency distributions," Radar, Sonar and Navigation, IEE Proceedings - , vol.150, no.4, pp.203-11,, 1 Aug. 2003. doi: 10.1049/ip-rsn:20030712

Abstract: Low-frequency radar systems provide some attractive advantages in a few niche applications, such as foliage penetration and covert operation. In low-frequency imaging systems, data must be collected over a wide range of angles to obtain cross-range resolution comparable to that obtainable from a competing small-angle high-frequency system. The reflectivity of a target varies with aspect angle; although this variation is usually ignored by traditional radar imaging algorithms, it sometimes cannot be neglected in wide-angle scenarios. To account for aspect dependence of reflectivity, time-frequency transforms have been invoked to generate a series of images corresponding to different look angles; these images may be considered individually or synthesised into a single image. A simple theoretical analysis with a point scatterer illustrates why the angular dependence needs explicit consideration. The potential of time-frequency methods is illustrated via simulations

Reference

Range-Doppler Imaging of Rotating Objects

Walker, Jack L., "Range-Doppler Imaging of Rotating Objects," Aerospace and Electronic Systems, IEEE Transactions on , vol.AES-16, no.1, pp.23,52, Jan. 1980
doi: 10.1109/TAES.1980.308875

Abstract: During the integration time required to obtain fine Dopplerfrequency resolution in a range-Doppler imaging radar, a point on a rotating object may move through several range and Doppler resolution cells and produce a smeared image. This motion can be compensated by storing the appropriately processed return pulse, and the angular coordinates are determined by the angular coordinates of the radar antenna. The resulting stored data represents the three-dimensional Fourier transform of the object reflectivity density, and hence can be processed by an inverse Fourier transformation. Also included is an analysis of the three-dimensional radar/object geometry with separate source and receiver locations. The effects of various system aberrations are investigated and experimental results from a microwave test range which demonstrate the image improvement are presented.

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Signal Synthesis and Receiver Design for MIMO Radar Imaging

Multiple-input–multiple-output (MIMO) radar is an emerging technology that has significant potential for advancing the state-of-the-art of modern radar. When orthogonal waveforms are transmitted, with $M+N$ ($N$ transmit and $M$ receive) antennas, an $MN$-element filled virtual array can be obtained. To successfully utilize such an array for high-resolution MIMO radar imaging, constant-modulus transmit signal synthesis and optimal receive filter design play critical roles. We present in this paper a computationally attractive cyclic optimization algorithm for the synthesis of constant-modulus transmit signals with good auto- and cross-correlation properties. Then we go on to discuss the use of an instrumental variables approach to design receive filters that can be used to minimize the impact of scatterers in nearby range bins on the received signals from the range bin of interest (the so-called range compression problem). Finally, we present a number of numerical examples to demonstrate the effectiveness of the proposed approaches.- Reference