Abstract: A bandpass filter having three waveguide cavities probelessly coupled in a tri-section for producing an asymmetric response about a passband. In another aspect, the bandpass filter also includes first and second waveguide tri-sections coupled in series via a common waveguide cavity, providing a bandpass waveguide filter having transmission zeros on only one side a filter passband.

Abstract: A microwave bandpass filter for frequencies in the range of 30-3000 MHz comprises a substrate formed from dielectric ceramic sheets fused together and stacked according to a dielectric constant required of the filter capacitors, the plates of which are formed on the substrate. Discrete air core coils, to provide greater frequency selectivity in this particular frequency range, are attached into the circuit on a top surface of the substrate, and a drawn metal can covers the circuitry on the top surface and is soldered to a metallized coating extending over substantially all of the rest of the substrate except for surface mounting lead portions and associated conductive paths. Thus, EMI and RFI shielding is provided by the combination of the metal can and the ground plane of the circuit.