An algorithm for downconverting signals using complex bandpass sampling in SDR system

Bandpass sampling is a useful method for direct digital downconversion without analog mixer. This sampling method is essential for the software defined radio system. Also, bandpass sampling can be extended to accommodation of multiple standards. In this paper, we derived useful equations, which are related to complex bandpass sampling. Also, we proposed algorithms to determine the available sampling range and the theoretical minimum sampling frequency for simultaneously downconverting two filtered signals, that is two different standards.