Design and implementation of digital down converter system based on optimized mixer

Aiming at the shortcomings of digital down-conversion ( DDC) module such as low precision, expensive logic resources and difficult to process the digital intermediate frequency (IF) signals in real-time when using spectrum analyzer to monitor spectrum, this paper optimizes the mixer module of the traditional digital down conversion system and proposes an efficient one. Firstly, the sampling rate of the analog-to-digital converter (ADC) is set to 4 times the carrier center frequency, while the sampling conversion ratio and the number of sub-ADCs is set to a positive integer multiple of 4, now the mixer can be completely merged into the multiphase Cascaded Integrator Comb (CIC) decimation filter. Then, a set of DDC system is constructed based on the optimized mixer, where each node is reasonably allocated to the system down sampling rate. Finally, CIC compensation filters are added so as to improve the accuracy of data transmission. Experimental results show that compared with the traditional DDC, resource consumption is reduced and the data accuracy error is reduced from 1.7% to 0.8% in optimized DDC. It can satisfy the requirements of small power consumption, high accuracy and stable operation.