The paper introduced the features,and structure of AD6655 which was 14-bit analog-to-digital converter,and specially introduced the function and capability analysis of digital down converter(DDC) integrated in AD6655.The design of a digital repeater based on AD6655 was provided.The scheme based on IF?鄄sampling was employed to fit for different digital repeaters in mobile communication system. The test showed that the EVM could satisfy all requirements.