Abstract
This study investigated wideband waveform generation using a field programmable gate array (FPGA) for X-band high-resolution synthetic aperture radar (SAR). Due to the range resolution determined by the bandwidth, we focused on wide bandwidth generation while preserving spectrum quality. The proposed method can generate wide bandwidth using a relatively low system clock. The new approach was designed in Simulink and implemented by very-high-speed-integrated-circuits hardware description language (VHDL). We also proposed a hardware structure in accordance with the proposed method. Signal connections of FPGA and digital analog converter (DAC) are described in the design of the proposed hardware structure. The developed X-band waveform generator using the proposed method output the desired pulse waveform. For the reduction of phase error and improvement of spectrum quality at the X-band, phase error compensation and pre-distortion were applied to the waveform generator. The results of the simulation and the hardware output demonstrate that the variation and standard deviation of the phase error were improved within the frequency spectrum. Accordingly, the proposed method and the developed waveform generator have the potential to produce a high-resolution image of the area of interest.
Highlights
Synthetic aperture radar (SAR) transmits and receives microwaves during mission operation
We propose an additional block diagram to compensate for the phase error caused by MDDS generation
We propose a Simulink block structure for phase compensation because the phase error is larger than tens of clocks and randomly appears during radio frequency (RF) modulation
Summary
Synthetic aperture radar (SAR) transmits and receives microwaves during mission operation. The research fields of SAR are divided into SAR system development, SAR observations by onboard satellites, unmanned aerial vehicles (UAV) or cars, image processing, and image applications for enemy surveillance or natural disaster monitoring. One system that has been developed was completed in a project led by the national institute, i.e., Korea aerospace research institute (KARI) and the defense industry, because of the enormous money and time requirements. Even though these organizations developed independently, they use commercial, off-the-shelf equipment or design their own test equipment [5,6,7,8]. Instead of a direct digital synthesizer (DDS) chip and arbitrary waveform generator (AWG), we designed and developed a system for generating the waveform
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