A 295-337 GHz 2.5 dBm Psat Cascode-Based Frequency Doubler in SiGe BiCMOS Technology

This paper presents a 295-337GHz high output power, cascode-based frequency doubler, achieving 2.5 dBm saturated power ($\mathrm{P}_{\mathrm{s}\mathrm{a}\mathrm{t}}$) at 312 GHz and 42 GHz $\mathrm{P}_{\mathrm{s}\mathrm{a}\mathrm{t}}$3 dB-bandwidth. Inductive gain enhancement is applied to overcome high interconnect losses and the reduced gain performance above the transit frequency of the available technology. This is achieved by embedding an inductance between the base terminals of the cascode transistors, that provides a strong positive feedback. A peak conversion gain of 15dB is achieved at 312 GHz and remains above 7.5dB for operation at maximum output power. The chip is fabricated using a $130\mathrm{n}\mathrm{m}\mathrm{S}\mathrm{i}\mathrm{G}\mathrm{e}$ BiCMOS technology with $f_{\mathrm{t}}/f_{\max}$ of 250 $\mathrm{G}\mathrm{H}\mathrm{z}/370$ GHz and consumes 535mW from a 3.3V and 3.65V supply, which corresponds to a state-of-the-art drain efficiency of 0.3 %. To the best of the authors knowledge, the power of 2.5 $\mathrm{d}\mathrm{B}\mathrm{m}$ is the highest reported among cascode-based frequency doublers in SiGe HBT technology so far.