Relaxation oscillator

About: Relaxation oscillator is a research topic. Over the lifetime, 1952 publications have been published within this topic receiving 22326 citations.

Frequency comparator with hysteresis between locked and unlocked conditions

Abstract: A frequency comparator apparatus used with a reference clock, a voltage controlled oscillator circuit and a phase locked loop circuit includes a reference loop circuit wherein the reference loop circuit is activated when the frequency difference between the reference clock and the voltage controlled oscillator circuit is greater than about a first threshold. Also included is a data loop circuit wherein the data loop circuit is activated when the frequency difference between the reference clock and the voltage controlled oscillator circuit is less than about a second threshold.

Communications Using Chaotic Frequency Modulation

Abstract: Chaotic Frequency Modulation (CFM) provides the basis for a nonlinear communications system with (1) good noise suppression and (2) analogue signal encryption for private and secure communications links. CFM is a generalization of conventional Wideband Frequency Modulation (WFM) where the information about modulation samples mk are contained in the lengths of the periods pk for the kth cycle of the WFM waveform. A WFM modulator produces waveform periods described by an invertible function of the form pk=F(mk). Chaotic FM uses a map of the pulse periods to produce a noise-like pulse train even with a constant signal. The basis for CFM is a function pk=F(mk; pk−1, pk−2, …, pk−i), where i is the dimensionality of the map. A practical realization for a CFM transmitter employs an autonomous chaotic relaxation oscillator (ACRO) circuit for use as a chaotic voltage-controlled oscillator (CVCO). The ACRO is simple to construct, consisting of only two capacitors, one inductor, a bistable nonlinear element, and a modulated current source. The CVCO period (pk) is a nonlinear function of the current (mk) and the two previous pulse periods. Demodulation requires the use of at least three successive waveform-periods. Experimental and theoretical studies of the CVCO circuit have shown that (1) the ACRO return maps of pulse periods are embedded in three dimensions, (2) chaotic outputs are difficult to decode without prior knowledge of the circuit parameters, and (3) demodulation may be accomplished with a digital signal processor.

Phase-Noise Reduction in Oscillators via Small-Signal Injection

Abstract: This paper provides an original investigation around the phenomenon of phase-noise reduction in oscillators due to small-signal injection. The analysis employs phase-domain macromodeling techniques and fundamental results from the theory of stochastic processes. The proposed analysis also applies to strongly nonlinear circuits such as ring or relaxation oscillators, and relies on quantities which are easily measurable or derivable by designers.

The Van der Pol's mathematical model of the voltage-controlled oscillator based on a transistor structure with negative resistance

Abstract: The results of the mathematical modelling for the voltage-controlled oscillator based on a transistor structure with negative resistance are presented in this article. The generated oscillations with and without noise were described with the Van der Pol's model. The research was carried out for relaxation and oscillator modes of the generator.

Analysis and control of harmonic radiation from active integrated oscillator antennas

Abstract: Harmonic radiation from microstrip patch oscillators is examined experimentally and theoretically using both a single and dual parallel-tuned circuit Van der Pol oscillator model. Closed-form expressions are obtained for the fundamental and first harmonic voltage amplitudes, and results show reasonably good agreement with a commercial circuit simulator. Such expressions will be useful for designers of active integrated antennas, giving them greater physical insight into their operation. Experimental results are presented for three configurations of a patch oscillator, i.e., rectangular patch, circular-sector patch, and quarter-wave shorted patch. The latter two configurations present very low resistance at the first harmonic frequency and this leads to improved harmonic suppression performance. This is in qualitative agreement with theoretical predictions.