High Gain 130GHz Frequency Doubler with Colpitts Output Buffer Delivering Pout up to 8dBm with 6% PAE in 55nm SiGe BiCMOS

A mmWave frequency doubler in a SiGe BiCMOS technology is presented. The core of the circuit comprises a push-push pair, for second-harmonic generation, and a stacked common-collector Colpitts oscillator which works as a common-base injection-locked amplifier to boost the conversion gain and output power. The class-C operation of the transistor in the Colpitts buffer leads to a pulsed current shape with enhanced second-harmonic content. As a result, the power conversion gain of the frequency doubler is increased by up to 10dB, compared to the push-push pair alone. Moreover, the common-collector configuration keeps separate the oscillator tank from the load, allowing independent optimization of the harmonic conversion efficiency and the load impedance for maximum power delivery. Realized in a SiGe BiCMOS technology with 330GHz fmax, the proposed frequency doubler delivers Pout up to 8dBm at 130GHz with 13dB conversion gain and 6.3% Power Added Efficiency. A Figure of Merit is proposed to benchmark frequency doublers and the presented chip shows up to 3 times improvement compared to previously reported designs in the same frequency range.