Research on Generation and Pre-distortion of high-frequency and wide-band signal based on FPGA/DA

Abstract

In practical radar systems, amplitude and phase distortion exists in antenna channels, which has a bad effect on subsequent signal processing. So waveform generator is needed to launch signals covering radar waveband to make a channel test. Ensuring accuracy and bandwidth of the waveform generator is a fundamental requirement. Accordingly, this paper proposed a full flow of wideband waveform generation, including hardware design, parameter selection and pre-distortion correction. Direct digital waveform synthesize (DDWS) is done in the first, second, or third Nyquist region without analog frequency conversion, ensuring the quality of the waveform and pre-distortion measures are taken to correct the waveform reconstruction error. This paper presents an advanced generation method of wide-band LFM signal based on waveform storage method and introduces the theory of pre-distortion. Using only one high speed FPGA/DA as the control-unit to replace the way of using DSP+FPGA makes the system structure much easier. It can generate any kind of LFM signal, which has wide band. By using the pre-distortion technique, the phase and amplitude error of the LFM signal is less than 1 degree and its flatness is less than 0.5dB.