Loss cancelling resonator and filters

Claim 1

A frequency synthesizer comprising an oscillator having an output, a comb generator having an input and a transmission line output and adapted to generate a plurality of frequencies on said transmission line output, a switchable notch filter bank having an input and output and a plurality of control inputs, said oscillator output connected to said comb generator input, said comb generator transmission line output connected to said switchable notch filter bank input, said notch filter bank comprising a transmission line coupling said notch filter bank input to said notch filter bank output, a reference potential terminal and a plurality of resonators, said resonators connected in parallel with each other between said transmission line and said reference potential terminal, each of said resonators including a capacitance and an active inductive filter element, said active inductive filter element having first and second terminals and including a first inductance, a second inductance and a transistor having base emitter and collector electrodes, base circuit means connecting said base electrode to said first terminal, collector circuit means connecting said collector electrode to said first terminal, emitter circuit means connecting said emitter electrode through said first inductance to said second terminal, and said second inductance connected between said emitter electrode and said collector electrode, said plurality of notch filter bank control inputs respectively coupled to the transistors in said plurality of resonators and adapted to selectively apply biasing thereto for inserting particular ones of said plurality of resonators to filter from said notch filter bank output selected frequencies in the spectrum generated by said comb generator.