Octave tunable lumped-element notch filter with resonator-Q-independent zero reflection coefficient

A bandstop filter architecture with small form factor and very large attenuation over an octave frequency tuning range is demonstrated. The architecture provides a benefit of resonator-Q-independent zero reflection coefficient at the center frequency, and is demonstrated with a tuning range of 55.04 to 133.34 MHz varactor-tuned two-resonator notch filter with minimum notch attenuation of 64 dB, 3-dB fractional bandwidth (FBW) of 10.86% to 3.22% over the tunable frequency range and passband up to 356.5 MHz, resulting in a 6.48-to-1 upper passband, in a footprint of 2.27×1.65 cm². The unloaded quality factor (Q-factor) was extracted to be 62 at 133.34 MHz.