A 377-416 GHz Push-Push Frequency Doubler with Driving Stage and Transformer-Based Mode Separation in SiGe BiCMOS

This paper presents a WR2.2 push-push frequency doubler with two driving stages using Infineon's advanced 90nm SiGe BiCMOS technology, providing HBTs with an f(t)/f(max) of 300 GHz/500 GHz, respectively. Compared to conventional push-push frequency doublers, we use a design that utilizes transformer-based mode separation. The architecture of the doubler is essentially that of a differential cascode amplifier with a transformer as the load. However, the center tap of the secondary side of the transformer is connected to the MMIC output, causing the second harmonic to be the largest component of the output signal. Measurements exhibit a 3 dB bandwidth of 39 GHz, covering the frequency range from 377 GHz to 416 GHz. The maximum conversion gain is 2.9 dB and the maximum measured output power equals -5.4dBm at 390 GHz.