Novel frequency doubler using feedforward for fundamental frequency component suppression

Feedforward techniques are applied to a microwave frequency doubler for the first time. The feedforward branch is composed of 2 couplers and 1 phase shifter to adjust the phase and cancel the fundamental signal at the output of a single-ended doubler. This technique is experimentally demonstrated in the 1-to-2 GHz frequency. Compared to the single-ended doubler, the experimental results show more than 50 dBc fundamental signal suppression with only a small drop in conversion gain.