Showing papers on "Relaxation oscillator published in 2004"

Synchrony in a Population of Hysteresis-Based Genetic Oscillators

Abstract: Oscillatory behavior has been found in different specialized genetic networks. Pre- vious work has demonstrated nonsynchronous, erratic single-cell oscillations in a genetic network composed of nonspecialized regulatory components and based entirely on negative feedback. Here, we present the construction of a more robust, hysteresis-based genetic relaxation oscillator and pro- vide a theoretical analysis of the conditions necessary for single-cell and population synchronized oscillations. The oscillator is constructed by coupling two subsystems that have previously been im- plemented experimentally. The first subsystem is the toggle switch, which consists of two mutually repressive genes and can display robust switching between bistable expression states and hysteresis. The second subsystem is an intercell communication system involved in quorum-sensing. This sub- system drives the toggle switch through a hysteresis loop in single cells and acts as a coupling between individual cellular oscillators in a cell population. We demonstrate the possibility of both population synchronization and suppression of oscillations (cluster formation), depending on diffusion strength and other parameters of the system. We also propose the optimal choice of the parameters and small variations in the architecture of the gene regulatory network that substantially expand the oscillatory region and improve the likelihood of observing oscillations experimentally.

Modeling cardiac pacemakers with relaxation oscillators

Abstract: A modified van der Pol oscillator model was designed in order to reproduce the time series of the action potential generated by a natural pacemaker of the heart (i.e., the SA or the AV node). The main motivation was that the models published up to now were not altogether adequate for research on the heart. Based on either the classical van der Pol oscillator or other nonlinear oscillators, these models were interesting rather because of the physical phenomena that could be obtained (chaos and synchronization). However, they were unable to simulate many important physiological features of true physiological action potentials. We based our research on the experience of other groups which modeled neuronal oscillators. There complex nonlinear oscillators were used whose most important feature was a certain topology of the phase space. In our case, we modified the phase space of the classical van der Pol oscillator by adding two fixed points: a saddle and a node. In addition, a damping term asymmetric with respect to the voltage was introduced. Introduction of these new features into the van der Pol oscillator allowed to change the firing frequency of the pacemaker node without changing the length of the refractory period – an important physiological detail. We also show different ways of changing the pacemaker rhythm. A comparison of the properties of the signal obtained from our model with the features of the action potentials measured by other groups is made.

Dynamics of the fractional-order Van der Pol oscillator

Abstract: In this paper we propose a modified version of the classical unforced Van der Pol oscillator that occurs when introducing a fractional-order time derivative in the state space equations that describes its dynamics. The resulting fractional-order Van der Pol oscillator is analyzed in the time and frequency domains, for several values of order's fractional derivative and, consequently, of the total system order. It is shown that the system can exhibit different output behavior depending on the total system order. Several numerical simulations and performance indices illustrate the fractional dynamics

Laser range finding apparatus

Abstract: The laser range finding apparatus includes an optical relaxation oscillator assembly, outcoupling optics, a photodetector and a controller. The optical relaxation oscillator assembly produces relaxation oscillations. The relaxation oscillations are a series of optical pulses having a controllable repetition rate. The outcoupling optics receives the series of optical pulses and redirects a minor portion of the energy of the series of optical pulses. A major portion of the energy of the series of optical pulses is adjusted in accordance with first desired beam propagation parameters. A photodetector receives the minor portion and converts the minor portion to an electrical signal representative of the series of optical pulses. A controller receives the electrical signal and determines the repetition period between the optical pulses. The controller provides a controller output to the optical relaxation oscillator assembly for adjusting the controllable repetition rate of the series of optical pulses produced by the optical relaxation oscillator assembly. During operation, the major portion of the energy of the series of optical pulses is directed to a reflecting target, reflected therefrom, collected by the outcoupling optics, and directed back to the optical relaxation oscillator assembly to stimulate subsequent relaxation oscillations, thus locking the period of the relaxations oscillations to the time of flight of the roundtrip path between the laser finding apparatus and the reflecting target.

Synchronization rates in classes of relaxation oscillators

Abstract: Relaxation oscillators arise frequently in physics, electronics, mathematics, and biology. Their mathematical definitions possess a high degree of flexibility in the sense that through appropriate parameter choices relaxation oscillators can be made to exhibit qualitatively different kinds of oscillations. We study numerically four different classes of relaxation oscillators through their synchronization rates in one-dimensional chains with a Heaviside step function interaction and obtain the following results. Relaxation oscillators in the sinusoidal and relaxation regime both exhibit an average time to synchrony, /spl sim/n, where n is the chain length. Relaxation oscillators in the singular limit exhibit /spl sim/n/sup p/, where p is a numerically obtained value less than 0.5. Relaxation oscillators in the singular limit with parameters modified so that they resemble spike oscillations exhibit /spl sim/log(n) in chains and /spl sim/log(L) in two-dimensional square networks of length L. Finally, using a sigmoid interaction results in /spl sim/n/sup 2/, for relaxation oscillators in the sinusoidal and relaxation regimes, indicating that the form of the coupling is a controlling factor in the synchronization rate.

Precision relaxation oscillator without comparator delay errors

Abstract: A relaxation oscillator for generating an oscillator output signal having a predetermined frequency. The relaxation oscillator includes an interleaved charge pump for providing a restoring charge to an integrator in response to at least one charge pump control signal. The relaxation oscillator further includes an integrator having an integrator input connected to the current summing node. The integrator is adapted to produce an integrator output signal having the predetermined frequency at an integrator output. A comparator having an input connected to the integrator output is adapted to generate the oscillator output signal having the predetermined frequency in response to the integrator output signal.

Voltage controlled oscillator amplitude control circuit

Abstract: A voltage controlled oscillator amplitude control circuit has a voltage controlled oscillator circuit to output an oscillating signal having a controlled amplitude. It also has a control circuit to control the amplitude of the oscillating signal by providing a dominant pole, a filtering function, rectification, and a gain at a single node of the circuit.

Weakly nonlinear oscillations: A perturbative approach

Abstract: The perturbative analysis of a one-dimensional harmonic oscillator subject to a small nonlinear perturbation is developed within the framework of two popular methods: normal forms and multiple time scales. The systems analyzed are the Duffing oscillator, an energy conserving oscillatory system, the cubically damped oscillator, a system that exhibits damped oscillations, and the Van der Pol oscillator, which represents limit-cycle systems. Special emphasis is given to the exploitation of the freedom inherent in the calculation of the higher-order terms in the expansion and to the comparison of the application of the two methods to the three systems.

User-definable thermal drift voltage control oscillator

Abstract: A voltage controlled oscillator (200) that includes a slot-cut-printed-board coupling network (230) between a resonator (240), a tuning diode network (234) and an active device (210) and being operable to act as a common-coupling capacitor between the resonator (240), the tuning diode network (234) and the active device (210).

Voltage controlled oscillator with automatic band selector

Abstract: A method and circuit for selecting the band of a multi-band voltage controlled oscillator in a phase locked loop is described. In one implementation, the circuit comprises a voltage controlled oscillator, a selection circuit for selecting a band for the voltage controlled oscillator from a plurality of predetermined bands, a decision circuit for determining if the selection circuit should select a new band from the plurality of predetermined bands, and a charging circuit for adjusting the input voltage into the voltage controlled oscillator.

Oscillator circuit for eeprom high voltage generator

Abstract: A semiconductor oscillator circuit for an EEPROM high voltage charge pump utilizes a current generating means to charge a first and a second capacitor alternatively. The charging current produced by the current generating means is inversely proportional to the ambient temperature. The charging current is proportional to the supply voltage and consequently, the oscillator frequency output remains constant over a variable voltage supply. Such a constant frequency characteristic makes a low voltage operation possible, but slows down the oscillator frequency as temperature increases. The slowing of oscillator frequency limits the charge pump output voltage and enhances the lifespan of the EEPROM cells.

Voltage controlled oscillator and PLL circuit

Abstract: A voltage comparing circuit activates a first voltage comparison signal when a control voltage is lower than a first reference voltage and a second voltage comparison signal when the control voltage is higher than a second reference voltage. In synchronization with a count clock, a counter decrements a counter value during activation of the first voltage comparison signal and increments the counter value during activation of the second voltage comparison signal. An oscillating circuit selects one of oscillation frequency bands by the counter value and regulates an oscillation frequency according to the control voltage within the selected oscillation frequency band to output an output clock. This makes it possible to secure a wide oscillation frequency range in response to variance in operating conditions or a reduction in a range of the control voltage and to regulate the oscillation frequency of the voltage controlled oscillator by the control voltage alone.

50 GHz resonant tunneling diode relaxation oscillator

Abstract: InAlAs/AlAs based RTDs with a peak current density over 500 kA/cm/sup 2/ have been designed and fabricated. Relaxation oscillator circuits for 20 and 50 GHz were designed using these 0.6 /spl mu/m/sup 2/ RTDs. They consist of an RTD and a 5 /spl Omega/ resistor placed in a coplanar waveguide (CPW). The measured spectrum of the 20 GHz and 50 GHz oscillators showed only odd harmonics. The measured results of the relaxation oscillators show that they have very low phase noise (low jitter), below -110 dBc/Hz at 1 MHz offset in locked-mode, and can easily be phase locked. RTD based relaxation oscillation can be readily used as clocks in high-speed signal processing applications.

Synchronization and Window Map from Pulse-Coupled Relaxation Oscillators

Abstract: SUMMARY We present mutually pulse-coupled two relaxation oscillators having refractoriness. The system can be implemented by a simple electrical circuit, and various periodic synchronization phenomena can be observed experimentally. The phenomena are characterized by a ratio of phase locking. Using a return map having a trapping window, the ratio can be analyzed in a parameter subspace rigorously. We then clarify effects of the refractoriness on the pulse coding ability of the system.

A New Microstimulator with Pulse Width Modulation

Abstract: A novel implantable microstimulator has been designed, fabricated, and characterized. The pulse width modulation (PWM) has been used to control the output current source for changing the duration of output waveform. The frequency of output stimulus current can be controlled by a Schmitt trigger based relaxation oscillator. Finally, the intensity of output stimulus current can be programmed by a 5-bit digital code. This circuitry can operate in only 2.5V low voltage to improve the disadvantage of conventional microstimulator that is not suitable in low voltage. In the architecture of circuitry, it reduces the circuit complexity formed by typical microstimulators adopting mircoprocessors as the control unit. The measured results of the proposed microstimulator chip show that this system is quite feasible for different stimulus modes including regular, random and burst modes. This circuitry has been simulated with HSPICE and fabricated in a 0.35μm 2P4M CMOS process.

Experimental evidence for amplitude death induced by dynamic coupling: van der Pol oscillators

Abstract: Amplitude death is a coupling induced stabilization of a fixed point in nonlinear oscillators. This phenomenon cannot be observed in two identical nonlinear oscillators coupled by a diffusive connection. However, it has been analytically confirmed that a diffusive dynamic coupling can induce death. This study derives a necessary and sufficient condition for amplitude death in van der Pol oscillators coupled by a diffusive dynamic coupling. The well-known RC line (T-type) is used to implement the dynamic coupling.

Digital light ballast oscillator

Abstract: An oscillator for a power converter control outputs a pulse train based on a charging time of a capacitor linked to a variable current source. A digital to analog converter (DAC) controls the variable current source in conjunction with a switch to determine the charging time of the capacitor. By varying the digital DAC input, the charging time of the capacitor is modified, thereby modifying the frequency of the pulse train. A comparator compares the capacitor voltage to a toggled threshold, which switches depending on whether the capacitor is charging or discharging. The comparator output supplies the pulse train that can be used in a half bridge switching arrangement for the power converter, which can also serve as an electronic ballast for a lamp.

Design of 2 GHz quasi-lumped element oscillator

Abstract: This paper discusses the design of a quasi-lumped element PHEMT oscillator, operating at 2 GHz The quasi-lumped element resonator, fabricated on an FR4 printed circuit board, which consists of an interdigital capacitor in parallel with a straight line inductor, was used as a stabilizing element in the feedback type oscillator configuration The quasi-lumped element oscillator operated at 2056 GHz and the output power was 9 dBm The phase noise at 10 kHz offset frequency was measured as approximately -82 dBc/Hz

Fiber laser relaxation oscillation noise suppression through the use of self-biased intracavity loss modulator

Abstract: We demonstrate a technique for suppressing the intensity noise of erbium doped fiber lasers. We show that by introducing negative feedback into the system through the use of a self-biased intracavity loss modulator, the relaxation oscillation noise of the fiber laser could be suppressed by as much as 20dB. To explain the observed noise reduction phenomenon, a simple theory based on the linearized rate equation has been developed and is supported by experimental measurements. We also derive a formula for estimating the maximum achievable intensity noise suppression ratio.

A low noise current-controlled oscillator with high control linearity

Abstract: The noise performance of a current-controlled oscillator is presented in this paper. The relationship between the noise of the comparator reference voltage and the oscillator timing jitter is discussed. The R-S trigger in the oscillator is used to store the circuit state but limits the speed of the circuit and increases the timing jitter. The current source keeps charging the timing capacitor when the capacitor is discharged, which increases the circuit power dissipation. Several improvements on the oscillator have been suggested to overcome these problems. The new oscillator can operate in high speed with low timing jitter and good control linearity.

Relaxation oscillations in a bistable quantum Hall system

Abstract: Quantum Hall systems can show a bistability in the hysteresis of the breakdown. We realized a relaxation oscillator based on a quantum-Hall device with Corbino geometry. Investigations of the performance of such an oscillator revealed an increase of the hysteresis of the current–voltage curve of the device in comparison with the width of hysteresis at dc voltages. By direct measurements of the hysteresis of the current–voltage curve at different frequencies, we found a marked increase of the breakdown hysteresis at low frequencies of some Hz. We explain the observed dynamical enhancement of the breakdown hysteresis applying an electron heating model with a background (delocalization-related) component of conductivity, which decreases with increasing frequency, indicating a more effective localization already at low frequencies.

Voltage-controlled oscillator with differential output

Abstract: A voltage-controlled oscillator for generating differential output is disclosed. The voltage-controlled oscillator comprises a Colpitts oscillator having a first inductor and a capacitive divider having at least two capacitors connected in series. A varactor is connected in series with the capacitive divider and to a reference voltage, and a second inductor is mutually coupled to the first inductor for providing the differential output. A second inductor is substantially centrally tapped and connected to the reference voltage for providing a substantially balanced output. The operating frequency of the voltage-controlled oscillator is dependent on an applicable potential difference across the varactor.

CMOS interface of a flow sensor for urodynamic monitoring

Abstract: A signal conditioning CMOS integrated circuit is proposed for use with a micro-machined resistive flow sensor, adopted in order to non-invasively monitor urinary dysfunctions in male patients. The circuit is based on a relaxation oscillator with duty-cycle modulation and relative A/D conversion at chip level. The implemented resistive bridge-to-duty-cycle converter produces an output signal with duty-cycle highly linear in the change in resistance of the flow sensor's elements. The range of variability of the sensor resistors is a few hundreds of ohms in typical applications in the field of urology. Experimental tests with 1% precision resistors carried on the sensor interface evidenced a maximum non-linearity below 0.9% and a resolution of almost 7 bits, with a minimum measurable change in resistance less than 2 /spl Omega/ over the tested range. The proposed circuit, provided with digital output, also allows simple signal interfacing to any standard PC for data transfer and storage.

Two low-voltage high-speed CMOS frequency-insensitive PWM signal generators based on relaxation oscillator

Abstract: In this paper, two new simple PWM (Pulse Width Modulation) signal generators based on a modified CMOS relaxation oscillator are introduced. Translinear current dividers are proposed to improve the circuit performance such that it is frequency insensitive to the magnitude of an input signal. In addition, the precise PWM signal can be easily achieved under low voltage consumption and the output frequency can be ranged up to several megahertz. Furthermore, both voltage and current modulating signals can be applied. Based on the features and the simplicity of the circuits, it is very suitable for developing into Integrated Circuit (IC) form in communication applications. The simulation results through PSPICE show a good agreement with theoretical anticipation.

Uniform and user-definable thermal drift voltage control oscillator

Abstract: A voltage controlled oscillator that includes a slot-cut-microstrip-line coupled between a resonator, a tuning diode network and an active device and being operable to act as a common-coupling capacitor between the resonator, the tuning diode network and the active device.

Design and analysis of relaxation oscillators based on voltage-driven NICs

Abstract: This paper investigates the design and analysis of relaxation oscillators based on voltage-driven negative impedance converters. Results of Pspice simulations for submicron technologies are shown. In comparison to oscillators based on current-driven NICs, oscillators presented here have much higher operating frequencies.

Integrated circuit oscillator with improved frequency stability

Abstract: A method and apparatus providing a simple low cost integrated circuit oscillator with improved frequency stability over a range of selected frequencies by reducing the impact of process and temperature variations on a base current of bipolar transistor of the integrated circuit oscillator. A voltage follower circuit (105) included in an integrated circuit oscillator is injected with a base current provided by a current mirror (303) instead of a capacitor such that variations in the base current of the bipolar transistor over the range of operating temperature do not substantially alter the charge in the capacitor to change the frequency of the oscillator.

A Low-Voltage Fully Differential MOSFET-C Relaxation Voltage-Controlled Oscillator for Frequency Tuning

Abstract: A low-voltage, fully differential MOSFET-C relaxation voltage-controlled oscillator for the frequency tuning of filters is proposed. The oscillator is capable of self-startup and provides well-controlled amplitude. The performance of this circuit is demonstrated by simulation results.

Oscillator with controlled current source

Abstract: A circuit and a method are given, to realize and implement an oscillator circuit with a Smart Current Controlled (SCC) Resonator Driver. A newly introduced controlled current source for a crystal oscillator's amplifier element produces a controlled driving current for the resonator element during operation in both phases of the oscillation cycle to reach for low phase noise and reduced power consumption of the circuit. Said circuit and method are designed in order to be implemented with a very economic number of components, capable to be realized with modern integrated circuit technologies.