Precise LC Comb Filters, Packaged for Reliability

The engineering, packaging, and testing controls necessary to produce reliable, precise LC comb filters which are critical components in today's advanced military electronics systems, are often completely overlooked or inadequately stressed. It is common practice for engineers to consider the filter as a "black box" to be accepted as soon as the electrical requirements have been met. Then, there usually follows a crash program of makeshift "fixes" in order that the unit in final form may reliably meet the rigid environments encountered in Military Systems. This paper describes the design of a 60-filter comb, which is the critical front end of Doppler radar systems, and presents solutions to packaging problems encountered in its design, and the test controls devised to produce 60 precise LC filters with critical interrelated electrical specifications. The mechanical evolution of the design will be described. In summation, LC comb filters can be designed stressing repairability, good shop practice, and precision electrical characteristics, as well as environmental reliability.