FPGA implementation of digital local oscillator for digital stretch processing

The stretch processing is widely used for linear frequency modulation(LFM) signals in wideband phased array radars. Conventional phased array radar cannot support wideband signals because of the frequency dispersion effects. To avoid the problem, time delay beam-steering is utilized. But it raises the cost and complexity of the system. The digital stretch processing is proposed and particularly well suited to compensate the bandwidth dispersion in digital domain. However, one of the difficulties to realize digital stretch processing is to generate the high-frequency, wideband local oscillator signals. The method of multichannel parallel digital direct chirp synthesizer (DDCS) implemented in field-programmable gate array(FPGA) is discussed in the paper. The paper describes the details of multichannel echo processing, including multi-channel mixing and low-pass filtering. The design is successfully realized via Xilinx Integrated Software Environment (ISE) in Virtex6 FPGA and the simulation in Mentor Graphics ModelSim is presented to prove the validation of the design.