The Research Of The Downconverter Of The Intermediate Frequency(if) Digital Receiver

The idea of the so-called Software-radio is to locate the A/D interface of the wireless receiver as close as possible toward the antenna. The ideal position for sampling is just at the back-end of the antenna. However, it is still impossible to digitalize the signal at the radio frequency, due to the limitation of the hardware. Therefore, one of the possible solutions is to work at the intermediate frequency. Regarding to the digital receiver which working at the intermediate frequency, the Digital Down Converter (DDC) is one of the kernel techniques.The DDC down-converts the digitalized intermediate-frequency signal with higher speed into low-speed base-band signal. Then it is sent to the DSP system to process at real time, reducing the demand for DSP calculation time.This paper describes the details of Programmable Digital Down Converter (PDC) HSP50216, which is one of the serial products of the commercial DDC with four channels by INTERSIL. The main functions, internal structure and characterization of sampling filter have been explained in particular. In association with the application of HSP50216 in digital intermediate-frequency receiver, the design idea and important points about the key technique of realizing digital down converter using HSP50216,are presented .At the end, two examples on design are given.