Noise Analysis of Phase-Demodulating Receivers Employing Super-Regenerative Amplification

Growing interest in ultralow-power radio frequency receivers has reinvigorated research in super-regenerative amplifier (SRA) architectures, in part due to their ability to achieve enormous gain at very low power. Conventionally, SRAs have been paired with envelop detectors that demodulate amplitude-modulated signals (e.g., ON-OFF keying); mathematical models have been developed to predict the performance of such systems. Since modern communication applications require more spectrally efficiency modulation schemes, this paper develops a mathematical model that predicts the stochastic behavior of SRAs when used in phase-demodulating receivers. This stochastic model is then used to predict the sensitivity of a phase-demodulating receiver employing a Colpitts-based SRA. Results from the developed model are validated with measurements of a discrete prototype, illustrating that SRAs can be used with I/Q mixing to demodulate quadrature phase-shift keying signals with -88-dBm sensitivity when the SRA consumes 1.2 mA at 1.5 V at 45 MHz.