Broadband Receiver The Electromechanical Tune Preselection Filter And The Rf Front-end Research And Implementation

The subject derives from the project of "0.1M~3000MHz universal receiver", which is collaborated with Ministry of Science and Technology of PRC and Chengdu Sine Science and Technology Ltd. undertake the RF front end in this project. The RF front end is divided into two separate parts, the 0.1~30MHz & the 30M~3GHz RF front end. R&D on the later one is the my subject. By means of using the electronically tuned preselector and multiple conversion technology, a wide band receiver with wide dynamic range is basically achieved. The scheme is innovative and original not only in the scheme itself but also in the technology of some sub-circuits. The electronically tuned filter notably improves the selectivity.This paper describes the fundamental characteristics and the design procedures for varactor tuned combline microwave bandpass filter .It also developes a conclusion about the value of combline length for minimizing the bandwidth variation or optimum return loss independent of tuned frequency. In addition, it gives and analyses a kind of approximate model of the coupling suspend stripline. Finally, the design and experimental performance of varactor tuned filter are presented. Its performance is in close agreement with theoretical expectations.The paper begins with the deep analysis of high performance receiver parameters. Subsequently, the design methods are introduced about receiver high dynamic range. Then ,the system scheme analysis, implementation of each functional unit, some questions paid more attention in system design and debug are discussed in detail. The ultimate testing results of this subject are represented at last.