Design of Wide-Band DDS Signal Generator by Using FPGA-based Direct Digital Waveform Storage Method
Xiangkun Zhang · Ceshi jishu xuebao · 2013
This article proposes a design method for high-speed wideband radar chirp signal generator based on the principle of using the direct digital waveform storage(DDWS) to perform the direct digital synthesis(DDS),and gives out the system hardware and software design modules.The design employs a single-chip high-speed FPGA as the control core and double single-channel DAC for digital-to-analog conversion.It can generate any LFM signal that satisfies the conditions: clock frequency with 400 MHz,pulse width less than 16us,bandwidth within 320 MHz.Meanwhile,spurious frequencies,flatness in band,pulse compression result,the linearity of the chirp rate and I/Q phase orthogonality are analyzed and compared.The results show that,the spurious frequencies can be filtered out through low-pass filter,the flatness in band is less than 0.452 dB,the maximum side lobe level of the pulse compression results lower than-12.8 dB,the orthogonal circle diagram and the time-frequency analysis agree with the ideal condition.This method is easy to be realized and suitable for engineering application.