SOME DESIGN CONSIDERATIONS FOR UHF TUNER

Abstract

With the recent availability of UHF channels In India ,UHF tuners have became very Important do enable us to receive these additional channels. Basically a UHF tuner contain a RF amplifier,a Local oscillator and a mixer One of the things in all such type of circuits is the proper matching of terminating impedances. Matching by trough lines or microstrip lines is better suited for UHF frequency ranges. In this dissertation some important design considerations have been presented for design of UHF amplifier ,oscillator and mixer stages. The concept of S-parameters have been used. The tuning and impedance matching have been obtained by using microstrip 1.1 no r3 Concept of stability of active devices has been explained with help of Smith chart..Calculation of suitable source and load impedances of an amplifier ,for a specified noise figure and desired gain are presented in the form of noise circles on the Smith chart Dielectric constant of the PCB board has been measured with the help of Network Analyzer .A computer program is written that can accept y brS-1parameters.It has been checked to calculate following values correctly: Source and Load reflection Coeff. for maximum powewr gain. Stability factor K. Design for a maximum stable oscillator using S-parameters halbeen presented. Design considerations for mixer by bipolar transistor's inherent non-linearity are also given in this dissertation.