Analysis of a SiGe BiCMOS Detector for a Broadband mmW-integrated EPR Spectrometer

We present the analysis of a 130-nm SiGe BiCMOS millimeter-wave (mmW) detector, which will be used in an on-chip transmission-based Electron Paramagnetic Resonance (EPR) spectrometer. The EPR effect on the transmitted RF signal (1 to 40 GHz) is modeled by amplitude modulation (AM) with a single frequency, corresponding to the modulation of the magnetic field, and a small modulation index, corresponding to the absorption of the sample. In contrast to most analyses of mmW detectors, this work focuses on AM demodulation performance of a transistor in common emitter configuration under these conditions. The proportionality between the detected EPR signal and the effective transconductance is shown. We investigate the dependency of the optimum base emitter bias on the input power and the carrier frequency.