High-Frequency Crystal Filter Design Techniques and Applications

High-frequency crystal filters which operate to 40 mc are now being commercially produced. These filters, with bandwidths ranging from one cycle to several hundred kilocycles per second, have been made possible by new design techniques and simplified circuitry. Eliminating the need for multiple frequency conversion, the small rugged flters are already beginning to find wide use in many AM, SSB, and fm receivers as well as single-sideband generators. Crystal filters are normally composed of from two to eight quartz resonators in a lattice or bridge network. The filter components are characterized by high Q and stability under extreme environmental conditions. Normal values of Q for crystal filter components in the 1 to 40 mc range are from 50,000 to 200,000; in certain filters, element Q´s exceed 1,000,000.