Wide Tuning Bandwidth Ku-Band Varactor FET Oscillators

For a varactor tuned FET oscillator, a high ratio between maximum to minimum frequency is much more difficult to obtain as one goes up in frequency. It is shown that well designed multiple varactor type circuits must be used to reach Ku band with octave bandwidth. With non optimized 10 : 1 capacitance ratio varactors, a 2.4 frequency ratio has been reproducedly obtained, which is the best published result for fundamental operation in this frequency band. Linearity is also improved as compared to single varactor oscillators.