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.