Push-Push VCO using Tunable Differential Bandpass Filter based on SIW Technology

In this paper, a novel push-push voltage-controlled oscillator (VCO) using the tunable differential bandpass filter (BPF) based on substrate integrated waveguide (SIW) technology is proposed. Firstly, the tunable differential BPF with a high Q factor value, improved stopband suppression and differential configuration is used as the parallel feedback component to provide differential outputs in the design of the push-push VCO which can reduce the phase noise of the VCO. In addition, the fundamental signal suppression and second harmonic enhancement can be obtained simultaneously. Furthermore, with the suppression of the common mode (CM), the push-push VCO can operate at a phase difference of 180° mode without using any phase shifter which can prevent the deterioration of the phase noise. To demonstrate the hypothesis, we designed a push-push VCO based on differential SIW BPF and simulated it. The proposed push-push VCO has the phase noise of −138.8 ~ −150.7 dBc/Hz at the frequency offset of 1 MHz within the two tuning range of 23.76 ~ 23 98 GHz and 24.1~24.32 GHz.