A loss model for interdigital filters

Interdigital filters are widely used in the various cellular telephone systems. These filters are a convenient size in the cellular frequency bands and lend themselves to a fairly straightforward and economical realization. They are useful as both transmit and receive filters, and can be made to handle the RF power loads and to meet most of the loss requirements of a cellular cell site. Because the design constraints are often quite rigorous, it is very useful to be able to accurately predict the expected losses in the passband of these filters. A fairly simple model is presented which has been found quite useful in predicting these losses. The model is specifically designed for use with analysis programs such as PSpice. With the ability to accurately predict the expected losses in the filter, it is often possible to eliminate one iteration in the design process