A Programmable Pulse Expander for Airborne Synthetic Aperture Radar Applications

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  • 1 Institut für Hochfrequenztechnik, German Aerospace Research Establishment—DLR—Oberpfaffenhofen, Federal Republic of Germany
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Abstract

Pulse expansion is used in radar systems to achieve a high range resolution with long pulses and, hence, low-peak transmit power. A common solution is to generate linear frequency modulation using surface acoustic wave dispersive delay lines.

This paper discusses a programmable digital pulse expander developed for the DLR airborne experimental synthetic aperture radar (E-SAR). The precalculated waveform is stored in a fast random access memory module. By using an accurate I/Q modulator, bandwidths of up to 90 MHz can be achieved, corresponding to a range resolution of better than 2 m. The waveform with variable bandwidth, pulse length, weighting (e.g., Hamming, Taylor), and chirp characteristic can be designed on a software running on a personal computer. The expander has been verified by imaging a special test site. The design, realization, and performance of the expander are described.

Abstract

Pulse expansion is used in radar systems to achieve a high range resolution with long pulses and, hence, low-peak transmit power. A common solution is to generate linear frequency modulation using surface acoustic wave dispersive delay lines.

This paper discusses a programmable digital pulse expander developed for the DLR airborne experimental synthetic aperture radar (E-SAR). The precalculated waveform is stored in a fast random access memory module. By using an accurate I/Q modulator, bandwidths of up to 90 MHz can be achieved, corresponding to a range resolution of better than 2 m. The waveform with variable bandwidth, pulse length, weighting (e.g., Hamming, Taylor), and chirp characteristic can be designed on a software running on a personal computer. The expander has been verified by imaging a special test site. The design, realization, and performance of the expander are described.

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