Ceramic filter for use with a beacon receiver

摘要

An exemplary embodiment of the invention is a ceramic filter for use as a front-end filter feeding directly into an A-D portion of a digital signal processor to form a radio-beacon DGPS receiver. The filter includes a plurality of piezo-electric resonant stacks in a multi-stage topology to emulate a discrete component ladder network, representing a Butterworth filter modified to exhibit the roll-off characteristics of an Elliptical band-pass filter. This embodiment has a pass-band center frequency at about 304 kHz±1.5 kHz. The ceramic filter uses square and circular shaped ceramic piezo-electric resonant elements to provide enhanced performance and reduced size. The square and circular piezo-electric resonant elements, sandwiched between spring-plates, are arranged in horizontal layers with said spring-plates at filter section boundaries being joined by tabs at the respective layers.