Wideband Waveform Generation Using MDDS and Phase Compensation for X-Band SAR

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.

A Novel Real-Time Processing Wideband Waveform Generator of Airborne Synthetic Aperture Radar

“…Although waveforms can be synthesized by pre-storing calculated data in ROM or a dedicated flash chip expediently [15], this method is not fit for multi-mode, large TBP SAR systems that consume extensive storage resources. Another commonly used method is direct digital synthesis (DDS), which generates the LFM signal by accumulating frequency information through initial parameters and using it as an address to read signals from memory [16]. When compared with the direct storage of waveforms, the DDS method demands fewer storage resources but is more complicated [17].…”

An 18.8–33.9 GHz, 2.26 mW Current-Reuse Injection-Locked Frequency Divider for Radar Sensor Applications

“…In the doppler radar, a low frequency to millimeter-wave (mm-Wave) must be used to acquire a two-dimensional image through synthetic aperture radar (SAR). Bandwidths of 500 MHz or more are used to obtain high-resolution images [ 1 , 2 ]. In addition, wideband performance is very important in frequency-modulated continuous wave (FMCW) radars because wideband chirp is directly related to the high-resolution distance information [ 3 ].…”