Brief Analysis of Aliasing in Polar and Keystone Formats for Spotlight Synthetic Aperture Radar

Bauck, Jerald L.

doi:10.31224/osf.io/7dexn

Cited by 2 publications

(7 citation statements)

References 10 publications

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“…If these are transmitted sequentially the waveform is known as a stepped sine [11], [43], [40]. They can also be transmitted simultaneously with similar results under certain conditions assuming that the receiver is matched accordingly [44], although there are many things to consider in choosing a waveform type. The stepped sign signal resembles a discrete sort of chirp signal.…”

Section: F Spotlight Sarmentioning

confidence: 99%

A Rationale for Backprojection in Spotlight Synthetic Aperture Radar Image Formation

Bauck¹

2022

IEEE Aerosp. Electron. Syst. Mag.

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This note on backprojection for spotlight synthetic aperture radar image formation is mainly pedagogic in purpose and is intended to be accessible. The presentation from first principles is elementary and detailed, beginning with the wave equation and melding wave notions with signal processing notions using a compact and consistent notation throughout. A reflection model is developed including a general expression for the receiver signal which does not depend on a particular transmitted waveform. Then the signal is specialized to monochromatic waves to show how waves and the Fourier transform fit together. In the end the signal is once again generalized so that the theory works for any signal type. Backprojection is shown to reconstruct the wave field that was lost by sampling it at only one point, the receiving antenna. After specializing some details to the synthetic aperture radar geometry, the Projection Slice Theorem is introduced late, after an understanding of the underlying principles is obtained. Computational aspects are considered and it is seen that backprojection and direct Fourier inversion, also known as the polar format algorithm, are fundamentally the same, differing only in some implementation details, albeit significant ones, thus overturning the notion that backprojection is not a Fourier process. Those who might benefit from this paper include people who have worked in this field and who seek a somewhat different point of view from the usual presentation, people in other fields who are unfamiliar with some of the engineering concepts involved, and signal processing engineers who appreciate a bit of wave theory.

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Section: F Spotlight Sarmentioning

confidence: 99%

A Rationale for Backprojection in Spotlight Synthetic Aperture Radar Image Formation

Bauck¹

2022

IEEE Aerosp. Electron. Syst. Mag.

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“…There are more adjustments to be made before we can consider this a result suitable for our radar problem. Applying the same backprojection principle to the offset impulse receiver function under monochromatic illumination (19) results in…”

Section: Backprojection and Impulse Reconstructionmentioning

confidence: 99%

“…If these are transmitted sequentially the waveform is known as a stepped sine. They can also be transmitted simultaneously with similar results under certain conditions assuming that the receiver is matched accordingly [19], although there are many things to consider in choosing a waveform type. The stepped sign signal resembles a discrete sort of chirp signal.…”

Section: Spotlight Sarmentioning

confidence: 99%

“…Once again, this under-sampling is done intentionally for illustrative purposes. This particular form of aliasing is analyzed in terms of Hankel transforms and Bessel functions in [19]. Figure 19 shows a reconstruction of four impulses located in the x plane at (0, 0), (40, 10), (−35, 15), and (20, −30), made according to (31) and with a discretization similar to (35).…”

Section: Spotlight Sarmentioning

confidence: 99%

“…There is a way to ease the burden of the two-dimensional interpolation by placing a slight burden on the transmitter. Each pulse can be modified from the preceding pulse by subtly compressing or expanding it in time [23,19] causing an inverse amount of expansion or compression in its spectrum. This can be programmed into the waveform synthesizer of the transmitter.…”

Section: Computational Considerationsmentioning

confidence: 99%

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A Rationale for Backprojection in Spotlight Synthetic Aperture Radar Image Formation

Bauck¹

2019

Preprint

Self Cite

View full text Add to dashboard Cite

This note on backprojection for spotlight synthetic aperture radar image formation is mainly pedagogic in purpose and is intended to be accessible. The presentation is elementary and detailed, beginning with the wave equation and melding wave notions with signal processing notions using a compact and consistent notation throughout. A reflection model is developed including a general expression for the receiver signal which does not depend on a particular transmitted waveform. Then the signal is specialized to monochromatic waves to show how waves and the Fourier transform fit together. In the end the signal is once again generalized so that the theory works for any signal type. Backprojection is shown to reconstruct the wave field that was lost by sampling it at only one point, the receiving antenna. After specializing some details to the synthetic aperture radar geometry, the Projection Slice Theorem is introduced late, after an understanding of the underlying principles is obtained. Computational aspects are considered and it is seen that backprojection and direct Fourier inversion, also known as Polar Format Algorithm, are fundamentally the same, differing only in some implementation details, albeit significant ones, thus overturning the notion that backprojection is not a Fourier process. Those who might benefit from this paper include people who have worked in this field and who seek a somewhat different point of view from the usual presentation, people in other fields who are unfamiliar with some of the engineering concepts involved, and signal processing engineers who appreciate a bit of wave theory.

show abstract

Brief Analysis of Aliasing in Polar and Keystone Formats for Spotlight Synthetic Aperture Radar

Cited by 2 publications

References 10 publications

A Rationale for Backprojection in Spotlight Synthetic Aperture Radar Image Formation

A Rationale for Backprojection in Spotlight Synthetic Aperture Radar Image Formation

A Rationale for Backprojection in Spotlight Synthetic Aperture Radar Image Formation

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