In this paper, a novel X-band push-push oscillator employing dual-feedback sub-oscillators and a half-wavelength microstrip line resonator is presented. The dual-feedback sub-oscillator consists of a series feedback commonly used in conventional oscillators due to its good phase noise performance and a parallel feedback circuit which improves both the output power and stability. The resonator and power combiner form a single circuit allowing compact size. Measured results show that an excellent output power of +13.3 dBm was obtained at the second harmonic frequency of 9.81 GHz. Moreover, superior phase noise of -105.0 dBc/Hz and -123.5 dBc/Hz were achieved at 100-kHz and 1-MHz offset frequencies, respectively. The suppression of undesired harmonic signals, namely fundamental and third harmonic signals, are 27.9 dB and 55.7 dB, respectively. With a simple design structure and compact size the proposed push-push oscillator achieved very good performance.
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