An X‐band push‐push oscillator with parallel feedback configuration designed by microstrip balanced bandpass filter

Abstract

In this article, a push-push oscillator with parallel feedback configuration designed by the microstrip balanced bandpass filter (BPF) is proposed. The push-push oscillator consists of two sub-oscillators with a balanced BPF. The balanced BPF with the open-circuited stubs exhibits the desired differential-mode frequency response and achieves high common-mode suppression simultaneously. Based on the technique of the balanced BPF, the out-of-phase fundamental signals and odd harmonic signals are canceled out while the even harmonic signals are well combined. The prototype of the push-push oscillator is designed and fabricated. Measured results show that the proposed push-push oscillator works at 9.96 GHz of the second harmonic frequency. The actual output power is −8.57 dBm. The rejection of the fundamental signal and third harmonic signal are better than 27 and 42 dBc, respectively. The phase noise of the proposed push-push oscillator is −128.3 dBc/Hz at 1 MHz frequency offset.