Abstract: This paper proposes a programmable digital downconverter (DDC) design method for ASIC implementation. The DDC is embedded in a 4GS/s-12bit ADC and is capable of processing input signals at a frequency of 4GHz and provides extraction factors of 4 Downsampling function for 8, 16, 16 and 32. The designed DDC consists of a numerically controlled oscillator based on the CORDIC algorithm and a decimation filter bank implemented by a full HB-FIR filter. According to the HB-FIR filter coefficient characteristics and spectral response characteristics, a variety of improved structural optimization designs are proposed in hardware implementation, reducing the area by about 50%. Based on the 40nm CMOS process, digital front-end and back-end implementations of the digital downconverter were completed and taped out. The simulation results show that the design can achieve the design goals at a working clock frequency of 500 MHz. The layout area is 1550*650um^2, and the operating voltage is 0.9 V. The power consumption is 180.69 mW. It is verified that the design method is suitable for 2^n down conversion of high-speed and high-precision digital signals.