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RLC Electronics has developed a new line of high frequency surface-mount cavity filters for small scale, low profile system integration. Cavity filters are desirable for their low insertion loss, tight frequency selectivity and broad spectrum rejection. On the other hand, cavity filters can be difficult to integrate with planar topologies such as microstrip and coplanar waveguide. Critical space is often consumed with coaxial connectors and cables, leading to higher losses and mismatches. The surface-mount cavity filter design from RLC eliminates coaxial connectors and utilizes RF pins or PC boards, saves space, cost and weight and improves electrical performance.

Various mounting methods can be used, determined by the available space and configuration of the subassembly. Where the filters need to be integrated onto multi-level circuit boards, the part must be attached directly onto the top layer (“drop-on”). Metallized pads or RF pins on the filter can be directly attached by solder reflow or by applying epoxy to the launch traces on the circuit board. Wire or ribbon bonding may also be used. The filter body itself is also attached using the same processes, which provides grounding and isolation. Optionally, the complete filter may be installed by pick-and-place. In cases where a pocket can be made in the circuit board and housing of the subassembly, the filter is mounted into the pocket (“drop-in”), and the body is attached with mounting screws.

Using full 3D electromagnetic modeling software, the challenging task of transitioning from common planar topologies into cavity structures is optimized. Designs are created and constructed using proprietary techniques that result in rugged, stable performance over a full range of environmental stresses.

High Q cavity filter performance is available through X-, Ku- and Ka-Bands with profile height as low as 200 mils. Typically, designs achieve up to 60 dBc rejection out to 3× the center frequency while maintaining good passband matching (e.g., 14 dB return loss).

RLC Electronics Inc.
Mt. Kisco, N.Y.