Differential oscillator based on double-sided parallel-strip line

A differential oscillator using double-sided parallel-strip line (DSPSL) with an inserted ground plane is proposed in this paper. The differential-mode operation of the two sub-oscillators leads to the inherent suppression of the second harmonics at the common DSPSL output port, while the fundamental signals are well combined without additional combiner required. The inset length of the ground plane into the DSPSL resonator can be optimized to make further suppression for the second harmonic. The oscillator was also designed into a voltage-controlled oscillator (VCO), which was combined with a 100 ohm DSPSL-fed quasi-Yagi antenna to from a voltage-controlled integrated antenna oscillator (VCIAO). Due to the differential output of the proposed VCO, the cross polarization of the proposed VCIAO is suppressed to a great extent.