Investigation of Microstrip Applications for Varactor-Tuned UHF Tuners

The use of microstrip with varactor diodes to construct a UHF tuner for commercial television receivers is a marked departure from previous exploitations of microstrip. Usually, it has been used for network elements in broadband applications with fixed center frequency. Such applications are diametrically opposed to the conditions in UHF receivers, where fractional bandwidths less than 5% are required over nearly an octave variation of center frequency. The scope of this paper is a discussion of the most fundamental problems associated with microstrip in varactor-tuned UHF tuners. These problems are as follows: 1. Determination of parametric relationships 2. Delineation of device limitations 3. Formation of an approach to preselection