Octave tunable lumped-element notch filter

A new lumped-element notch filter architecture with uniform attenuation characteristics over an octave tuning range is described. The approach is demonstrated by a 20 to 55 MHz varactor-tuned two-resonator notch filter with minimum notch attenuation of 40dB, 3dB bandwidths of ∼2.5 MHz, tuning times of less than 3 µs, control voltages below 5V, and passband insertion loss less than 0.2dB from 18 to 60 MHz.