An efficient low-cost fixed-point digital down converter with modified filter bank

In radar system, as the most important part of IF radar receiver, digital down converter (DDC) extracts the baseband signal needed from modulated IF signal, and down-samples the signal with decimation factor of 20. This paper proposes an efficient low-cost structure of DDC, including NCO, mixer and a modified filter bank. The modified filter bank adopts a high-efficiency structure, including a 5-stage CIC filter, a 9-tap CFIR filter and a 15-tap HB filter, which reduces the complexity and cost of implementation compared with the traditional filter bank. Then an optimized fixed-point programming is designed in order to implement DDC on fixed-point DSP or FPGA. The simulation results show that the proposed DDC achieves an expectant specification in application of IF radar receiver.