8GHz Suspended Low Pass Filter

The two pictures show the substrate and carrier with ground removed to create high impedance suspended lines. The substrate measures 0.3″ X 1.0″ wide and is has been suspended to raise the Q. Design of this filter relied upon electromagnetic simulation (HFSS) and demonstrates what can be achieved with modern design tools.

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8GHz Suspended Low Pass Filter
8GHz Suspended Low Pass Filter - Back
 

HFSS model file used for verification of the above design.

8GHz Suspended LPF - HFSS File - GND Holes
8GHz Suspended LPF - HFSS File
 

Measurements show an 18% stop/start ratio with a low insertion loss. No special or exotic materials are needed and there is no tuning required.

S21 Response
Return Loss