Showing papers on "Relaxation oscillator published in 1993"

Rapid synchronization through fast threshold modulation

Abstract: Synchronization properties of locally coupled neural oscillators were investigated analytically and by computer simulation. When coupled in a manner that mimics excitatory chemical synapses, oscillators having more than one time scale (relaxation oscillators) are shown to approach synchrony using mechanisms very different from that of oscillators with a more sinusoidal waveform. The relaxation oscillators make critical use of fast modulations of their thresholds, leading to a rate of synchronization relatively independent of coupling strength within some basin of attraction; this rate is faster for oscillators that have conductance-based features than for neural caricatures such as the FitzHugh-Nagumo equations that lack such features. Computer simulations of one-dimensional arrays show that oscillators in the relaxation regime synchronize much more rapidly than oscillators with the same equations whose parameters have been modulated to yield a more sinusoidal waveform. We present a heuristic explanation of this effect based on properties of the coupling mechanisms that can affect the way the synchronization scales with array length. These results suggest that the emergent synchronization behavior of oscillating neural networks can be dramatically influenced by the intrinsic properties of the network components. Possible implications for perceptual feature binding and attention are discussed.

Phase-shifterless beam-scanning using coupled-oscillators: Theory and experiment

Abstract: The unusual nonlinear dynamics of systems of mutually synchronized, loosely coupled oscillators has been exploited for electronic beam-scanning. Using a simple theory based on coupled Van der Pol equations, it is shown that a constant phase progression, /spl Delta//spl phi/, can be established over the range -90/spl deg/ >

Frequency-stabilised RC oscillator for clock generator circuit

Abstract: The oscillator has an ohmic load (R11) and at least one capacitor (C1) determining the oscillation frequency, with a current sink (1) providing a constant current (Ik) in dependence on the ohmic load and a reference voltage (Uref), controlling the charging current circuit (2) for the capacitor. At least one comparator (3, 5) compares the capacitor voltage with the reference voltage, to control a discharge circuit (4) for the capacitor. Pref. the charging current circuit delivers a constant charging current to 2 capacitors (C1, C2) each capacitor voltage compared with the reference voltage by a respective comparator, with corresponding control of the capacitor charging and discharging cycles, one capacitor charged as the other is discharged.

Fully-differential relaxation-type voltage controlled oscillator and method therefor

Abstract: A fully-differential relaxation-type voltage controlled oscillator (VCO) (30) includes an operational transconductance amplifier (OTA) (31) for receiving a differential input voltage. The OTA (31) provides a charging current to a capacitor (33) proportional to the differential input voltage during a first phase of an output signal, and provides a discharging current to the capacitor (33) proportional to the differential input voltage during a secon d phase of the output signal. A comparator having hysteresis (34) detects the charge on the capacitor. A latching portion (35) latches the output of the comparator (34) to provide non-overlapping clock signals.

Charge-status indicator

Abstract: A circuit arrangement for indicating the charge status of a batter in an electrical appliance includes a voltage comparator with hysteresis which detects the battery voltage, an oscillator driven by the voltage comparator, and an indicating device. The oscillator oscillates when the voltage is above a first threshold voltage and switches the indicating device to an active condition. The oscillator is blocked when the voltage is below a second threshold voltage and switches the indicated device to a passive condition.

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 secure communication links. 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.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Voltage controlled saw oscillator

Abstract: A voltage controlled surface acoustic wave oscillator includes an integrated circuit and a two port resonator connected as a feedback element around the integrated circuit. The integrated circuit includes a phase shifting network and an amplifier directly connected to the phase shifting network.

Self-calibration timing circuit

Abstract: A method and apparatus for a "self-calibration timing circuit" is utilized to dynamically compensate for inherent performance differences between individual semiconductor dice, and for a wide range of different operating temperature and voltage parameters. The present invention accomplishes this by utilizing circuits which are deposed on the semiconductor die. These circuits consist of a relaxation oscillator running at the natural frequency of the silicon die, a gated counter counting the number of cycles of the relaxation oscillator frequency during a reference clock period to produce a ratio thereof, and a decision circuit that utilizes this ratio to optimize a system clock frequency for best system operation.

Periodic pulling in a driven relaxation oscillator

Abstract: Periodic pulling, the incomplete entrainment of a driven, nonlinear oscillator, is observed experimentally in a relaxation oscillator for the first time. A neon-bulb relaxation oscillator is driven by a chopped, neon-resonant, laser beam. For driving frequencies just outside the range for entrainment, the signatures of periodic pulling are verified. The experimental results are qualitatively reproduced in numerical solutions of the driven van der Pol equation.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Designer's casebook-multivibrator runs at approximately= 1.5 V

Abstract: The design of an emitter-coupled astable multivibrator that operates with a low supply voltage is presented. >

Low frequency oscillator using capacitive charging/discharging

Abstract: A low-frequency oscillator whose duty ratio can be simply controlled includes a charging and discharging circuit for charging a capacitor via a constant current source and then discharging the capacitor according to a discharge control signal. A voltage comparator compares the voltage across the capacitor with a reference voltage. A monostable multivibrator, triggered by the output of the voltage comparator, generates the discharge control signal. The duration of the discharge is determined according to the RC time constant of the monostable multivibrator, to thereby generate a rectangular waveform having an accurately controlled duty ratio.

Self-sustained acoustoelectric and photoelectric oscillations in systems with relaxation

Abstract: New acoustoelectric and photoelectric self-sustained oscillation and self-modulation phenomena in systems with relaxation have been investigated. Layered metal-semiconductor-dielectric or piezoelectric structures with external feedback have been studied theoretically and experimentally. The theory presented explains the experimental results and gives a criterion for existence of the phenomena. A quasi-harmonic regime of the self-sustained oscillations is described by the Van-der-Pol equation, which can be very useful for practical applications because it expresses the relaxation properties of the structure in terms of the oscillation frequency. Possible applications of the self-sustained oscillations to new physical and chemical sensors and methods for investigating semiconductors are suggested. Dynamic characteristics of the self-sustained oscillations under different external conditions of as temperature and illumination are discussed. >

Synchronization of a forced relaxation oscillator

Abstract: The paper presents a method of synchronizing a relaxation oscillator to an external signal. The synchronization mechanism is linear and a detailed analysis is given. Very fast acquisition is shown to be possible. The oscillator synchronizes to the frequency of the forcing input or to a sub- or superharmonic. Possible applications include high-speed timing recovery systems where high acquisition speed is required

Collective phenomena in large populations of globally coupled relaxation oscillators.

Abstract: We present a study of a large pool of globally coupled relaxation oscillators. The reaction of the pool to the presence of a modulating external field is discussed. The coupling is assumed homogeneous and linear. Randomly distributed internal frequencies introduce a disordering element that, due to the coupling, can result in oscillator quiescence. Self-synchronization is shown to be absent in this system. However, this is entirely due to the linear coupling. For identical oscillators the basic state is incoherent and marginally stable in an extended region of parameter space. With modulation on the levels, the average rotation number as function of the external frequency lies on a devil's staircase, as for a single oscillator. However, the locked regions shrink with increasing coupling

Temperature stable square wave oscillator

Abstract: An oscillator circuit with enhanced frequency characteristics is provided. This oscillator circuit includes a buffer (102) to amplify the output signal and provide a positive feedback, an inverter (106) to provide negative feedback to cause oscillation, a capacitive divider circuit (110, 112) for charge storage, a resistor (116) to provide controlled discharge, and a diode circuit (114) for providing frequency stability. Since frequency stability is included within the oscillator circuit, there may be no need to perform resistor trimming at the time of manufacture. Further, the capacitive divider circuit eliminates parasitic charge injection.

Collective phenomena in large populations of globally coupled relaxation oscillators

Abstract: We present a study of a large pool of globally coupled relaxation oscillators. The reaction of the pool to the presence of a modulating external field is discussed. The coupling is assumed homogeneous and linear. Randomly distributed internal frequencies introduce a disordering element that, due to the coupling, can result in oscillator quiescence. Self-synchronization is shown to be absent in this system. However, this is entirely due to the linear coupling. For identical oscillators the basic state is incoherent and marginally stable in an extended region of parameter space. With modulation on the levels, the average rotation number as function of the external frequency lies on a devil's staircase, as for a single oscillator. However, the locked regions shrink with increasing coupling

Resonant-Tunneling Transmission-Line Relaxation Oscillator

Abstract: A new type of resonant-tunneling oscillator is analyzed that does not require dc bias stability in the negative-differential-resistance region. The oscillator consists of a resonant-tunneling diode coupled to a transmission line in such a way that repetitive switching of the diode occurs across the negativeresistance region. The output waveform consists of a sequence of pulses having a repetition rate determined by the electrical delay of the transmission line and a pulse width determined by the switching time of the diode. When the electrical delay is comparable to the switching time, the output is quasisinusoidal. Numerical simulations with a prototype resonant-tunneling diode yield a maximum repetition rate of 192 GHz and a pulse width of 2 ps.

High voltage measuring device

Abstract: PURPOSE:To obtain a low power consumption type device by dispensing with a high voltage service power supply by setting a relaxation oscillation circuit utilizing a programmable unijunction transistor (PUT) to a principal constitutional element. CONSTITUTION:The primary resistance of high voltage equipment to be measured is subjected to resistance-type potential division and the voltage proportional to the primary voltage is inputted to a transmission part. An impulse current is applied to an infrared LED at the interval corresponding to input voltage in the transmission part to allow the LED to emit infrared rays. The infrared rays are sent to a receiving part 4, for example, through an optical cable 3. The interval of infrared rays is observed in the receiving part 4 and the presence of voltage or a voltage value is displayed. The transmission part 2 is constituted as a constant current type circuit keeping a current Id constant using a PUT as an active element to be allowed to function as a relaxation oscillator requiring no service power supply oscillated in the frequency proportional to input voltage Vcc and the output thereof is supplied to the LED to send out a light pulse.

On a relaxation oscillator with periodic threshold

Abstract: The authors analyze a relaxation oscillator which includes a hysteresis element with periodic thresholds. The fundamental interests are in recognition and classification of various nonlinear phenomena. As the period of thresholds varies, the system exhibits various interesting periodic responses. Birfurcation diagrams are shown. The response includes hysteresis characteristics and has some universality. In some parameter region, the system exhibits quasi-periodic oscillation. A sufficient condition is derived for this oscillation. Some of the theoretical results were confirmed by laboratory measurements. >

Microprocessor Based Magnetic Fluxmeter using Unijunction Transistor Probe

Abstract: A simple design of magnetic fluxmeter using 8085 microprocessor has been described. The circuit accurately measures the strength of magnetic field using the magnetic field dependent properties of a unijunction transistor. The transistor forms part of relaxation oscillator circuit whose frequency is affected by the presence of magnetic field. The magnetosensitivity of the proposed circuit is 40 counts Tesla−1. One of the salient features of the present design is that the microprocessor controls the ON-OFF action of electromagnet.

Circuit for low-noise amplitude HF oscillator - has bipolar transistor with high boundary frequency, operated in base circuit at low currents

Abstract: The HF oscillator circuit contains a low-noise bipolar, oscillator transistor (1) with high boundary frequency, operated in base circuit at very low currents. An oscillation circuit of a coil (L1), an equalising capacitor (C4) and capacitors, (C2,3) are coupled to the collector of a low capacitance (C1). The LF voltage, decoupled from the oscillation circuit, is amplified in a separating amplifier consisting of a transistor (T2), a base voltage divider (R2,3), an emitter resistor (R4), a collector transformer (L3) and an emitter blocking capacitor (C13). After rectifying by diodes (D1,2), it delivers a base current (IB) for a transistor (T3), parallel to resistor (R9) of the base voltage divider (R8,R9) of the oscillator transistor. USE/ADVANTAGE - For low-noise, amplitude controlled HF oscillator, with wide band transistors.

Coupled relaxation oscillators for frequency multiplication

Abstract: Relaxation oscillators with microbridges as hysteretic elements are investigated in a frequency range of up to 1 GHz. The signal form of the voltage pulses and the resulting frequency versus bias current dependence are calculated, as well as the frequency spectrum of the harmonics. To demonstrate the possibility of a frequency multiplication, several relaxation oscillators are coupled in a serial or ring configuration. Superconducting delay lines are used to synchronize the oscillators to each other with the proper phase shift. As our measurements show, a frequency multiplication, or at least an enhancement in the power of the desired harmonic is possible in this way.