A K-band Gilbert-Cell Frequency Doubler with Self-Adjusted 25% LO Duty-Cycle in SiGe BiCMOS Technology

This paper presents a novel frequency doubler that further enhances the superior performance of solutions based on the Gilbert-cell mixer. A novel scheme is proposed to operate the cell with a 25 % LO duty-cycle. This technique boosts the conversion gain by generating a square-wave like output current. Moreover, the use of a quadrature generation block, commonly adopted in mixer-based frequency doublers, is not required, thus improving the operation bandwidth. The duty-cycle is automatically regulated by a low-frequency feedback loop which ensures optimal operation against input power and PVT variations. The performance of a test chip in a SiGe - BiCMOS process is presented. With a low supply voltage of 1.5 V, the chip achieves 6 dB conversion gain, 5.7 dBm peak $\mathrm{P}_{\text{sat}}$ and 17 % power efficiency at 20 G Hz. The doubler delivers $\mathrm{P}_{\text{sat}} > 3\text{dB} \mathrm{m}$ over more than one octave bandwidth. Experimental results compare favorably against previously reported frequency doublers in the same frequency range.