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

In this article, a differential oscillator with electromagnetic interference (EMI) noise suppression and low phase noise performance is presented. 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. 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, a radio frequency (RF) downconverter 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.