Low phase noise push-push VCO using microstrip square open loop resonator and tunable negative resistance

In this paper, a novel push-push VCO using the microstrip square open loop resonator and the tunable negative resistance has been presented to reduce the phase noise. To tune the oscillation frequency of push-push VCO using the microstrip square open loop resonator, the varactor diode has been connected on the part of the negative resistance. The tuning range of the proposed push-push VCO has been 5.744 ~ 5.859 GHz by the tunable negative resistance. The phase noise has been -124.67 ~ -122.67 dBc/Hz @ 100 kHz in this tuning range by the microstrip square open loop resonator and push-push structure.