Showing papers on "Relaxation oscillator published in 2003"

A canard mechanism for localization in systems of globally coupled oscillators

Abstract: Localization in a discrete system of oscillators refers to the partition of the population into a subset that oscillates at high amplitudes and anotherthat oscillates at much loweramplitudes. Motivated by experimental results on the Belousov-Zhabotinsky reaction, which oscillates in the relaxation regime, we study a mechanism of localization in a discrete system of relaxation oscillators globally coupled via inhibition. The mechanism is based on the canard phenomenon for a single relaxation oscillator: a rapid explosion in the amplitude of the limit cycle as a parameter governing the relative position of the nullclines is varied. Starting from a parameter regime in which each uncoupled oscillatorhas a lar ge amplitude and no otherper iodic orotherstable solutions, we show that the canard phenomenon can be induced by increasing a global negative feedback parameter γ, with the network then partitioned into low and high amplitude oscillators. For the case in which the oscillators are synchronous within each of the two such populations, we can assign a canard-inducing critical value of γ separately to each of the two clusters; localization occurs when the value for the system is between the critical values of the two clusters. We show that the larger the cluster size, the smaller is the corresponding critical value of γ, implying that it is the smallerclusterthat oscillates at large amplitude. The theory shows that the above results come from a kind of self-inhibition of each cluster induced by the local feedback. In the full system, there are also effects of interactions between the clusters, and we present simulations showing that these nonlocal interactions do not destroy the localization created by the self-inhibition.

Quadrature voltage controlled oscillator utilizing common-mode inductive coupling

Abstract: A voltage controlled oscillator including a first oscillator circuit portion with at least one first inductor, and a second oscillator circuit portion with at least one second inductor, wherein the at least one first inductor and the at least one second inductor are electromagnetically coupled to each other.

Adaptive CFL control circuit

Abstract: An electronic ballast provides fault detection and safety features for overcurrent protection and hard switching at a half bridge. A voltage controlled oscillator supplies a switching frequency that is modifiable based on operational feedback parameters. A feedback circuit senses load current and output voltage to determiner fault conditions and to provide control information for adaptively adjusting the frequency of the voltage controlled oscillator. By appropriately controlling the voltage controlled oscillator output, the electronic ballast maintains a zero volt switching with minimum current switching to achieve an efficient and robust electronic ballast control. The entire control is integrated on a single integrated circuit.

Capture range control mechanism for voltage controlled oscillators

Abstract: A voltage controlled oscillator generates an output signal whose frequency varies as a first function of a control voltage applied to a control terminal. The voltage controlled oscillator has a wide range of frequency of operation. A gain adjust circuit adjusts the gain of the voltage controlled oscillator such that the first function varies as a second function of the gain. In a preferred embodiment the gain adjust circuit includes a variable impedance that may be external or integrated onto a common chip with the oscillator core.

A temperature compensated fully trimmable on-chip IC oscillator

Abstract: The design of an IC on-chip oscillator, including temperature compensation circuitry, a robust spread reduction technique and digital trimming is described. The IC oscillator provides a 12.8 MHz clock signal with a frequency spread of /spl plusmn/25% before the 8 bit digital trimming. After centering the oscillator at the target frequency, a temperature compensated voltage and current reference circuit allows for less than /spl plusmn/5 % frequency variation when operating from 3 to 5 V power supply and from -40 to 125 /spl deg/C of temperature range. The oscillator is implemented in a 0.5 /spl mu/m CMOS technology, occupies an area of 420/spl times/440 /spl mu/m/sup 2/ and dissipates less than 400 /spl mu/W at 3 V supply without requiring any external reference or components.

Integrated relaxation oscillator with improved sensitivity to component variation due to process-shift

Abstract: A system and method for designing an integrated relaxation oscillator that exhibits reduced change in the frequency of oscillation caused by process variation. Improved sensitivity to component variation due to process shift is achieved through using more than one structure type when implementing the resistors affecting the RC time constant and threshold (trip point) voltages of the oscillator. Structure types are related to the fabrication process and for a CMOS process include, but are not limited to n-diffusion, p-diffusion, n-well, p-well, pinched n-well, pinched p-well, poly-silicon and metal. Each structure type exhibits statistically independent process variations, allowing for application of Lyapunov's extension of the Central Limit Theorem for statistically uncorrelated events to desensitize the effect from different possible causes. Thus, improvement in the performance of the oscillator may be achieved with a reduced trim requirement and without using external precision resistors.

Monolithic SOI-MEMS capacitive pressure sensor with standard bulk CMOS readout circuit

Abstract: We report an integrated monolithic micromechanical capacitive pressure sensor circuit based on novel method for fabricating pressure detecting vacuum cavities into buried oxide of SOI-wafer. The method allows fabricating the readout circuit with standard bulk CMOS process. The readout circuit of the pressure sensor is a low-power CMOS relaxation oscillator.

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.

Oscillator circuit having reduced layout area and lower power supply transients

Abstract: An oscillator circuit (60) has a comparator circuit (68) and a monitor and control circuit (80). The comparator (68) provides a periodic output signal. The monitor and control circuit (80) controls the voltage swing of the periodic output voltage in response to monitoring a periodic input voltage. A capacitor (90) is coupled between the output terminal of the monitor and control circuit (80) and input terminal of the comparator (68) and is sized to set the oscillation frequency. The monitor and control circuit (80) functions to limit the input voltage excursions without using an attenuation capacitor. Eliminating the attenuation capacitor provides a smaller oscillator circuit having reduced power supply current spikes and which is easier to implement.

Oscillator with temperature control

Abstract: An oscillator circuit includes a capacitor device, a current source for supplying a current to the capacitor device, a reference voltage, and a control circuit. The reference voltage is a first input to a comparator. An output of the capacitor device and an output of the current source are a second input to the comparator. The control circuit resets the oscillator circuit when the first and second inputs to the comparator are equal.

Relaxation oscillations and dynamical enhancement of the breakdown hysteresis in quantum Hall systems with Corbino geometry

Abstract: Using the bistability of quantum Hall systems in the hysteresis region of the breakdown, we realized a simple relaxation oscillator based on a quantum Hall device with Corbino geometry. Investigations of the performance of such an oscillator revealed the increase of the hysteresis of the current-voltage curve of the device in comparison with the value of hysteresis at dc voltages. By direct measurements of the hysteresis of the current-voltage curve at different frequencies, we have found that a dramatic increase of the breakdown hysteresis happens already at low (Hz-range) frequencies. We explain the observed dynamical enhancement of the breakdown hysteresis using an electron heating model and the assumption of a decreasing background (delocalization-related) component of the conductivity with increasing frequency.

Method and apparatus for an improved nonlinear oscillator

Abstract: A nonlinear oscillator method and apparatus. According to one embodiment, a nonlinear oscillator is closed. The nonlinear oscillator includes a first linear amplifier, a second linear amplifier and nonlinear amplifier having a substantially similar design that includes an adjustable linear transconductance region width. The input/output characteristics of the nonlinear oscillator can be represented by van der Pol equations. In another embodiment, a method for providing nonlinear oscillations is disclosed.

System and method for tuning an oscillator

Abstract: A voltage-controlled oscillator includes a resonator circuit and a voltage source. The resonator circuit includes a capacitive circuit that has a plurality of analog voltage controlled capacitive elements coupled to one another. The voltage source is coupled to the resonator circuit and provides a voltage to the plurality of analog voltage controlled capacitive elements. Each of the plurality of analog voltage controlled capacitive elements is activated as a function of the voltage thereby increasing linearity of a frequency tuning voltage parameter of the resonator.

Dual slope dual range oscillator

Abstract: A dual range oscillator provides two different ranges of oscillator frequency output based on switched current sources charging a capacitor. As several current sources are combined to charge capacitor, the interval for charging the capacitor decreases and changes the oscillator frequency output accordingly. A reference voltage supplied to a comparator checks the voltage on the capacitor to determine when to combine current sources to charge the capacitor and modify the timing interval and the corresponding oscillator frequency output. The different current sources are switched to the capacitor to provide modified charging slopes. The dual slope, dual range oscillator permits frequency switching operation in a variety of environments and applications with a simplified control and integration into a single chip.

Lumped, inductorless oscillators: how far can they go?

Abstract: The fundamental question of how much we can ultimately reduce the phase noise of a lumped, inductorless oscillator through careful design is addressed and it is shown that the fluctuation dissipation theorem of thermodynamics imposes a 1,ower limit on the phase noise. An analytical formulation of this limit is presented and it is shown that the phase noise of ring oscillators with long-channel MOS devices is closer to this limit compared to that of the relaxation oscillators or ring oscillators with short channel MOS devices.

Function principle of a relaxation oscillator based on a bistable quantum Hall device

Abstract: We present a simple relaxation oscillator based on a quantum Hall device with Corbino geometry near the breakdown of the quantum Hall effect. In the hysteresis region of the breakdown, the quantum Hall device exhibits bistable behavior. If a resistance is connected in series and a capacitor in parallel to the quantum Hall device, the bistable switching leads to subsequent charging and discharging of the capacitor, detectable as relaxation oscillations. We explain the observed oscillations by solving Kirchhoff’s equations and obtain a good quantitative description of the experiment. From this, we deduce some dynamical parameters of the Corbino device and discuss the performance limits of the oscillator.

Relaxation oscillator with propogation delay compensation for improving linearity and maximum frequency

Abstract: The present invention uses a variable reference voltage to compensate for propagation delay in a tunable oscillator caused by delays in the electronic components. The reference voltage is decreased as the control current increases and is varied in frequency to match the phase of the oscillator.

A square-rooting current-to-frequency converter

Abstract: A square-rooting current-to-frequency converter is presented in this paper. It has been designed by using one relaxation oscillator where a current-controlled resistor in CMOS technology with bisection of the input voltage is used instead of the ordinary resistor. In this way, the time constant of the relaxation oscillator is current-controlled. There is no need for a high stable voltage or current references in the proposed circuit. By appropriate setting of the process parameters of the MOSFETs used, the temperature variations of the output frequency can be made smaller than 7.6/spl times/10/sup -3/%/K. Experimental results confirm that the behavior of the proposed square-rooting CFC is in good agreement with the predictions of the analysis performed. According to these results, relative errors are less than 1% for the input current range from 35 /spl mu/A to 15 mA, and for the output frequency range from 1.45 kHz to 9.80 kHz.

A 100 MHz DDS with synchronous oscillator-based phase interpolator

Abstract: A synchronous oscillator-based phase interpolator is used to lower spurious tones of a 100 MHz 16 b DDS. The synchronous oscillator locked-loop produces an eight-phase clock with coarse phase interpolation, while eight identical oscillators coupled with a DAC provide accurate phase adjustment. Spurious tone reduction obtained with the accurate phase interpolation is about 20 dB.

A quadrature relaxation oscillator-mixer in CMOS

Abstract: This paper describes the design of a quadrature cross-coupled oscillator circuit integrated which also realizes the mixer function in a phase lock loop (PLL) This should be able to provide a very accurate phase relation (<1/spl deg/) This combined oscillator/mixer is first evaluated using a high-level model, in up and downconverter configurations A circuit implementation is then carried out, in which all the variables are kept independent at circuit level, ensuring a practical implementation close to that of the high-level model The circuit is designed in a standard 035 /spl mu/m CMOS technology with an oscillation frequency of 900 MHz, it has an overall area of 521 /spl times/ 515 /spl mu/m/sup 2/ (157 /spl times/ 119 /spl mu/m/sup 2/ for the IQ oscillator/mixer circuit) and a power consumption of 70 mW with a 3 V power supply The circuit performance is evaluated by simulation

Identification of systems with limit cycles

Abstract: Limit cycle oscillations occur in a wide range of electrical, mechanical, and aerospace applications. In this paper we present a method for constructing system models that are able to reproduce a periodic signal as a limiting trajectory. Our approach is based on continuous-time modeling of a scalar nth-order system whose dynamics are represented as a map of integrals and derivatives of the available signal. The method is demonstrated on the classical Van der Pol oscillator and a nonlinear oscillator with piecewise linear damping.

A 5.8-GHz Quadrature Cross-Coupled Oscillator

Abstract: This paper describes the implementation of a quadrature cross-coupled relaxation oscillator to be used in an OFDM RF front-end transceiver. A prototype of the oscillator was realized in a SiGe BiCMOS technology, and an oscillation frequency of 5.8 GHz was obtained which is 1/6 of the maximum fT of the bipolar transistors. The circuit performance is evaluated by simulation and by experiment.

Lumped, inductorless oscillators: how far can they go? [phase noise reduction limit]

Abstract: The fundamental question of how much we can ultimately reduce the phase noise of a lumped, inductorless oscillator through careful design is addressed and it is shown that the fluctuation dissipation theorem of thermodynamics imposes a lower limit on the phase noise. An analytical formulation of this limit is presented and it is shown that the phase noise of ring oscillators with long-channel MOS devices is closer to this limit compared to that of the relaxation oscillators or ring oscillators with short channel MOS devices.

Fifth order low-pass transitional Gm-C filter with relaxation oscillator frequency tuning circuit

Abstract: The design and implementation of gm-C filter with on-chip automatic tuning circuit is described Transitional Bessel-Chebyshev filter is implemented to compromise between high attenuation and low group-delay variation The circuit is fabricated with 018 /spl mu/m CMOS process with 6-metal single poly The filter operates at a cutoff frequency of 10 MHz with a single 13 V supply voltage The measurement results shows an attenuation of 70 dB at stop-band can be achieved, while keeping a low group-delay variation of less than 7 nSec up-to 15 times of cutoff frequency The cutoff frequency can be linearly tuned from 4 MHz to 10 MHz through the tuning loop By employing relaxation oscillator, accurate and robust frequency tuning scheme is implemented Measured with sufficient samples, the frequency tuning circuit shows an cutoff frequency tuning error of less than 70% over wide range of supply voltages (13 V to 21 V) and operating temperatures (-40/spl deg/C to +85/spl deg/C) in the whole tuning range

Low noise relaxation type oscillator

Abstract: This invention discloses a low noise relaxation oscillator to generate reference current and voltage by an outward resistor, to filter noise of the reference voltage by a filter circuit to get stablegrid voltage as the control voltage of the current mirror circuit to get stable two oscillation currents by mirroring the reference current to be inputted into the oscillation circuit together with the grid voltage. The said two oscillation currents flow through two oscillation capacitors respectively and the two oscillation capacitors and the grid voltage compare the voltage with two comparatorsto generate interactive signal to output, so as to effectively improve flutter and operation period efficiency of the clock pulse.

Capacitive Angular-Position Sensor

Abstract: This paper describes the design, realization and experimental characterization of a capacitive angular position sensor The sensor is composed of two parts, namely the sensing element and the dedicated signal conditioning electronic circuit The sensor is based on a low-cost Printed Circuit Board technology for the electrodes, and the use of a thick conductive rotor that is electrically floating and does not require any electrical contact to the electronic circuit The electronic circuit is based on a relaxation oscillator and the output is a DC voltage proportional to the angular position of the rotor The sensor and the electronic circuit are electrically equivalent to a voltage-excited resistive potentiometer The fabricated device provides redundancy by including two identical and independent sensors and electronic circuits in the same housing that work as separate measuring sections using the same rotor Measurement results on the prototype over a measurement range of ±11o gave a best-fit line nonlinearity within ±1% of voltage supply

To the theory of feedback in generators with virtual cathode

Abstract: The self-consistent nonstationary model of beam feedback in devices with virtual cathode (VC), which uses the flow instability in the cathode-anode gap and nonlinear particle interaction with VC oscillations is presented. Nonlinear process involving both areas is featured as an interaction between coupled Van der Pol-Duffing oscillators.

Active matrix display

Abstract: In an active matrix local tunable oscillators (11) are provided as the respective driving means at each picture element (8), e.g. in displays with frequency dependent (optical) properties or effects (dielectrophoresis, dielectric anisotropy). Other applications are sound and vision systems like the singing display which has an acoustic transducer means. Different kinds of oscillators (relaxation oscillators, ring oscillators) may be chosen in which the tuning of frequencies is based on e.g. the variation of a current supplied to a capacitor.

A voltage-controlled oscillator for IEEE 802.11a and HiperLAN2 application

Abstract: This paper presents an integrated voltage-controlled oscillator with a frequency doubler, intended for 5-to-6 GHz applications. The oscillator adopts a common-collector Colpitts topology driving a series-connected off-chip tank. This circuit demonstrates a 44% tuning range and a harmonic rejection better than 40 dB, dissipating 28mA from a 2.3V voltage supply. The phase noise at 1 MHz offset from the carrier is better than -120 dBc/Hz over the entire tuning range.

Dynamic operation of photonic crystal planar waveguide DFB and F-P lasers

Abstract: In this paper, for the first time we present an analysis of the dynamic operation of the F-P and DFB lasers based on photonic crystal structure. In our theoretical model, we take into account the gain saturation effect, transverse and longitudinal field distribution. With the help of time dependent laser rate equations, we obtain an approximate formula relating the damping rate and frequency of relaxation oscillations and modulation bandwidth to the output power and laser parameters such as parasitic losses in the active medium and photonic crystal cell geometry. With the help of this relation, laser characteristic showing an optimal reflection for F-P laser and optimal coupling strength for DFB laser, which provide maximal power efficiency for a given laser structure, are obtained. We shown that relaxation oscillations parameters and 3 dB modulation bandwidth strongly depend on values of photonic crystal parameters. We believe that our model of dynamic operation can be useful tool for modeling such laser structures.