Push-push oscillator design based on a substrate integrated waveguide (SIW) resonator

A substrate integrated waveguide resonator (SIW) is used to design a push-push oscillator. The SIW resonator presents a resonant mode at approximately half the output signal frequency. Due to the symmetry of the circuit architecture both an in-phase and an out of phase mode may exist, with the out of phase mode being the desired one, as the fundamental frequency components cancel at the output node while the second harmonic components combine. Harmonic balance analysis is used together with continuation methods in order to trace the solution curves of the two modes versus a selected circuit parameter. This provides a design methodology as it allows one to identify parameter ranges where the in-phase mode does not exist. The results are demonstrated on a 29.5 GHz oscillator.