Narrow-band, fixed-tuned, and tunable bandpass filters with zig-zag hairpin-comb resonators

Hairpin--comb filters have been previously shown to have special properties that are advantageous for the design of compact, narrow-band, and bandpass microstrip filters. Herein, a new "zig-zag" form of hairpin-comb filter is introduced, which is shown to have additional important advantages for designing compact narrow-band filters. Examples with computed responses and the measured results from high-temperature superconductor trial designs are presented. The considerable flexibility available in the design of bandpass filters' of this sort is shown to be helpful in the design of tunable bandpass; filters having nearly constant bandwidth and passband shape as they are tuned. Measured results for tuning over nearly an octave range are presented.