Despite their simplicity, analysis and design of superregenerative oscillators is often still based on approximations which provide limited insight into its behavior. In this paper we investigate the superregenerative oscillator in the linear and logarithmic operation modes without any approximations. A frequency-domain formulation allows us to efficiently compute the relevant waveforms both in the time and in the frequency domains. One of the main results is the ability to efficiently predict the exact envelope and the instantaneous phase and frequency of the generated waveforms for sinusoidal input signals. The formulation allows taking into account different amplitude-limiting nonlinearities that are responsible for the logarithmic response. We analyze different superregenerative oscillator designs under various operating conditions. We also provide a comparison of the results with those obtained with other techniques.

Abstract-In this paper we present a description and experimental verification of a superregenerative receiver (SR) for QPSK signals. Exploiting the fact that a conventional SR generates pulses which preserve the input phase information, we take N 1-bit samples of each generated pulse. A suitable choice of the sampling frequency gives as a result a bit vector containing a sub-sampled version of each PSK pulse. Extremely simple digital processing of the vectors from two consecutive pulses allows symbol decision, together with information on signal quality and frequency displacements. Although presented for the QPSK case, the principle may be applied to the M-PSK case with obvious changes. Experimental results on a 20 kbit/s proof-of concept receiver in the 27 MHz band, achieving a sensitivity of −103 dBm, with an FPGA-based implementation of the digital part, validate the proposed approach.

In this paper we investigate the possibilities of narrowband FSK detection using a superregenerative (SR) receiver. Previous SR FM demodulation techniques rely on detecting the amplitude variations caused by the different frequencies involved in FSK modulation. However, this requires relatively high frequency deviations because the frequency response of SR receivers is not very selective. In this paper we take a different approach, exploiting the distinct phase trajectories of FSK modulations resulting from the transmitted data. The well-known fact that the SR oscillator response preserves the phase information of the received signal is successfully exploited to allow the detection of several FSK modulations. These include the special case of MSK, opening the way to applying the SR principle to several communication standards, such as IEEE 802.15.4. The key ideas for symbol synchronization are also presented. Experimental results on a 10 kbit/s proof-of-concept MSK receiver, achieving a sensitivity better than 114 dBm in the HF band, validate the proposed approach.

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This paper presents a method to quantify noise in superregenerative oscillators. A frequency domain technique, originally intended to determine the signal response, can also be used to determine the noise response. This paper focuses on the procedure required to achieve this. Signal and noise spectra are obtained and their shape is compared. Finally, signal-to-noise ratio is computed for different quench signals.