Lumped element filters consist of discrete capacitors and inductors soldered to a substrate in various schematic configurations. These compact designs are particularly suitable for applications where size is critical. This topology is suitable for lowpass, highpass, bandpass, bandstop and multiplexing applications.
Numerous types of transfer functions are achievable using lumped element designs. The most efficient solution is selected for each application. By varying the capacitive and inductive coupling between sections,
Freedom Microwave can produce symmetric or asymmetric all-pole responses. Pole-placement in linear phase/group delay equalized responses is also realizable. The achievable unloaded Q's for these structures can be as high as 400. The Q for a particular design depends upon the inductor size, core material, and frequency of operation. Broad stopband performance can be achieved by suppressing parasitic resonances via careful component selection and through the use of proprietary design practices.
For high power application, large air wound inductors and high voltage capacitors are used. Proprietary design techniques and careful component selection ensure minimal temperature drift, and in many cases temperature coefficients are less than 5 ppm/deg. C are achievable. Both miniature and standard designs are available with either coaxial connectors or axial/radial feedthrough for direct circuit board installation. Several surface finishes, including silver, nickel, and gold are available depending upon the specific customer requirements.
In many instances, especially in broad passband or non-contiguous multiplexing applications, the lumped element topology can be easily integrated with other topologies to maximize performance in the smallest possible package volume.
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