Compact Hairpin Filter

Using Sonnet Software I was able to synthesize a 5 section band pass filter (BPF) built on a 20 mil thick Rogers RO4350B material – starting with a normalized low pass prototype of a Tchebyscheff topology (0.1dB ripple), transforming to a BPF, and converting the elements to mutual coupling coefficients. Once the coupling coefficients are known Sonnet is used to solve for the spacing of each resonator and the loaded Q of the end resonators.

Sonnet Software Simulation of a 5 section BPF

Below is the PCB test cards.

Compact Hairpin Filter PCB

Testing matches very close to simulation.

Measured Results