Reseach And Design Of Frequency-conversion Channels Of S-band Converter Based On CPCI Bus

In many fields, such as, wireless communication system and microwave measuring systems, converter is becoming widely used nowadays. The converter directly impact on the dynamic performance of the wireless communication system. With the level of China’s aerospace technology increasing so rapidly, the demand for low cost, miniaturization and high performance converter is becoming much larger. How to design a durable miniaturization converter quickly and accurately is becoming a worthy study.This paper focuses on designing a downconverter based on CPCI bus. It provides a good converter structure for microwave communication systems. In engineering, downconverter based on CPCI bus occupies the following advantages: durability, shock resistance, ventilation and portability. In this paper, at first the structures of downconverter are specifically introduced. Then the advantages, disadvantages and their problems of the existing downconverter were analyzed. Indexes of each device used in the downconverter were analyzed, and finally the super-heterodyne structure of high sensitivity, selectivity and dynamic range was chosen. 900 MHz is selected as the intermediate IF frequency through analysing and simulating so that the the image frequency is far away from the useful signal’s. The maximum attenuation of an attenuator is 30 dB, so two attenuators are added to achieve the gain ripple no more than 1.0dB with 50 dB overall gain. What’s more, one of the attenuators must be the first stage of the system so that the signal between-70 dBm and 0dBm will not be saturated.Downconverter is mainly composed of RF amplifier, filter, mixer, IF amplifier, attenuator, low-pass filter and band-pass filter. After that, feasible devices were selected to form each module. Then indexes of the converter were calculated to examine whether the device meets performance requirements or not. The simulation and experimental results prove the outcomes besides spurious signals out of the band are met the requirements for the design of S-band downconverter based on CPCI bus.