Design of Digital Down Converter (DDC) for GSM

In this paper the programmable Digital Down Converter (DDC) structure is proposed which can be used in digital receivers that meets GSM specifications in wireless communications systems. The major advantage of the proposed DDC is that it does not have the passband drop which is very often associated with the Cascaded Integrator-Comb (CIC) based DDCs. Another improvement of the proposed DDC structure compared to the existing off-the-shelf DDC products is that, instead of operating at the input (high) sample rate, the multiplications of the quadrature mixing process are performed at a much lower sample rate. MATLAB and Xilinx ISE 12.3 version software is used for simulating each block of DDC at system level testing.