Differential Oscillator With Electromagnetic Interference Noise Suppression Characteristics Based on Balanced Common-Mode Reflectionless Filter

A differential oscillator with electromagnetic interference (EMI) noise suppression and low phase noise performance is presented in this paper. The proposed balanced common-mode reflectionless dielectric resonator filter achieves the high group delay at the center frequency and the differential oscillator realizes the common-mode EMI absorptive performance, which improves the ability of the differential oscillator's electromagnetic compatibility (EMC). A differential oscillator's prototype with a center frequency of 3.49 GHz is designed and manufactured for validation. According to the measured results of the prototype, the phase noise of the proposed differential oscillator is −112.85 dBc/Hz @ 100 kHz and −132.62 dBc/Hz @ 1 MHz, respectively. The output power is 9.69 dBm and the second harmonic suppression is 61.62 dBc. The proposed differential oscillator achieves low phase noise, high output power, and high second harmonic suppression performances. To verify the improvement of the proposed differential oscillator's EMC ability, an RF down-converter circuit is established and modeled. Based on the experimental results of the intermediate frequency time-domain analysis under common-mode EMI noise conditions, the RF circuit with the differential oscillator using the balanced common-mode reflectionless filter possesses a uniform waveform signal output, which verifies the proposed design method.