Custom Filter Design

By Microwave Packaging Technology, Inc.

MPT has developed several microwave hybrid products. This white paper documents some of the custom filter design work done by MPT. First, this paper discusses the frequency limits of lumped elements for realizing microwave filters. A specific example is given to illustrate the bandwidth limitation of lumped elements and a lumped element filter result is shown. Second, results on a 3GHz interdigital band pass filter are shown. Third, a X-band coupled line filter is presented. These filters were used in hybrid microwave products developed by MPT.

Introduction: Filters are used in communication and radar systems to reject undesired signals and pass desired signals. This characteristic of filters allows them to be used at many different points in a system. For instance, filters are used at the RF input to a receiver to "pre-select" the desired frequency bands. They are also used after non-linear components such as mixers to reject unwanted frequency components.