A Parallel-Strip Line Differential Oscillator with High Suppression of Second Harmonics

Abstract

In this paper, a differential oscillator using parallel-strip line (PSL) with an inserted ground plane is proposed. Its two identical sub-oscillators on the opposite sides of a dielectric substrate, sharing a common PSL resonator and common ground plane in the middle of the substrate, generate anti-phase fundamental signals and in-phase second harmonics. At the common PSL output, the second harmonics are inherently cancelled out while the fundamental signals are well combined. The combination circuits, as required by the conventional differential circuits, are no longer needed. To further enhance the suppression of the second harmonics, the inset length of the ground plane into the PSL resonator is optimized to make the second harmonics be suppressed inside each sub-oscillator.