Showing papers on "Relaxation oscillator published in 2005"

Minimum achievable phase noise of RC oscillators

Abstract: To make RC oscillators suitable for RF applications, their typically poor phase-noise characteristics must be improved. We show that, for a given power consumption, this improvement is fundamentally limited by the fluctuation-dissipation theorem of thermodynamics. We also present the analytical formulation of this limit for relaxation (including ring) oscillators using a time-domain phase-noise analysis method which is introduced in this paper. Measurement shows the maximum possible improvement is generally less than 6dB for ring oscillators, while it can be as high as 21dB for other relaxation oscillators. The suboptimal performance of relaxation oscillators is attributed to the continuous current flow in these oscillator topologies. These results provide useful insight for feasibility studies of oscillator design.

Capacitance sensor using relaxation oscillators

Abstract: An apparatus that may be used to sense capacitance, as well as other functions. The apparatus includes a comparator circuit with hysteresis, a capacitor, and a current driver. The comparator circuit with hysteresis includes a first input and an output. The capacitor is coupled to the first input of the comparator circuit with hysteresis. The current driver is coupled to the output of the comparator circuit with hysteresis and to the capacitor. The current driver reciprocally sources and sinks a drive current through a terminal of the capacitor to oscillate a voltage potential at the terminal of the capacitor between a low reference potential and a high reference potential. The current driver is responsive to the output of the comparator circuit with hysteresis.

Low-frequency phase locking in high-inductance superconducting nanowires

Abstract: Niobium nitride nanowires show considerable promise as high-speed single-photon detectors. We report the observation of an anomalous low-frequency (∼10MHz) response in long, superconducting NbN nanowires (100nm wide, 4nm thick, and 500μm long). This behavior, although strikingly reminiscent of the ac Josephson effect, can be explained by a relaxation oscillation resulting from the high kinetic inductance of the type II nanowire. We simulate all of the observed effects using a simple resistive-hotspot/series-inductor model. The voltage pulses observed are indistinguishable from the pulses induced by visible photons, and our observations suggest noise-induced relaxation oscillations are one mechanism for the dark counts in photon detectors.

Surface-tension-driven nanoelectromechanical relaxation oscillator

Abstract: Because of its linear dependence on length scale, surface tension can be a dominant force for small systems. Properly harnessed, this force is uniquely suited for nanomechanical applications. We have developed a nanoelectromechanical relaxation oscillator with a surface-tension-driven power stroke. The oscillator consists of two liquid metal droplets exchanging mass, and its frequency is directly controlled with a low-level dc electrical voltage.

A current conveyor-based relaxation oscillator as a versatile electronic interface for capacitive and resistive sensors

Abstract: A new electronic interface circuit is presented. The circuit is built around a single plus-type second-generation current conveyor (CCII+) and can be used with resistive, capacitive and resistive-capacitive sensors. Experimental results are provided.

The noise performance of a high-speed capacitive-sensor interface based on a relaxation oscillator and a fast counter

Abstract: This paper presents the analysis and experimental results on the noise performances of a capacitive-sensor interface. The interface is able to measure low capacitance values in the order of picofarads and is implemented with a simple relaxation oscillator, a fast counter, and a microcontroller. The goal is to find the criteria to implement a low-noise system, so that, even with a short measuring time, low noise can be obtained. Experimental results are performed in order to prove the validity of the theoretical analysis. The achieved resolution, with a measuring time of 20 ms, was better than 14.2 /spl times/ 10/sup -7/ for the measurement of a capacitance value of 2.2 pF.

A low-cost and accurate interface for four-electrode conductivity sensors

Abstract: This paper presents a low-cost and accurate interface for four-electrode conductivity sensors. The interface mainly consists of an analog front-end, a multiplexer, and a voltage-to-time converter. The analog front-end is used to provide a controlled excitation voltage for the sensor and to convert the sensor signal (conductance) into a voltage signal. The voltage-to-time period converter acts as an asynchronous converter for the sensor signals (voltage), which employs a relaxation oscillator and outputs a period-modulated signal. Experimental results over a conductance range of 0.1 /spl mu/S to 20 mS show a random error of 1.6/spl times/10/sup -5/ and a systematic error of 6.6/spl times/10/sup -5/ for a measurement time of 110 ms.

Control circuit having frequency modulation to reduce EMI of power converters

Abstract: A control circuit having frequency modulation is used for reducing the EMI of a power converter. A switching circuit is couple to a feedback circuit to generate a switching signal for regulating an output of the power converter. A first oscillator is equipped to determine a switching frequency of the switching signal. A second oscillator is coupled to the first oscillator to modulate the switching frequency of the switching signal for reduce the EMI of the power converter. A programmable resistor is designed to attenuate the feedback signal of the feedback circuit. The resistance of the programmable resistor is controlled by the output of the second oscillator. Therefore, the output power and the output voltage can be kept constant when the switching frequency is modulated.

Frequency hopping control circuit for reducing EMI of power supplies

Abstract: A control circuit having frequency hopping capability is used for reducing the EMI of a power supply. A switching circuit is coupled to a feedback circuit to generate a switching signal for regulating an output of the power supply. A first oscillator determines the switching frequency of the switching signal. A second oscillator is coupled to the first oscillator to modulate the switching frequency of the switching signal for reducing the EMI of the power supply. An output of the second oscillator controls the attenuation rate of the feedback signal of the feedback circuit. Therefore, even if the switching frequency is hopped, the output power and the output voltage can still be kept constant.

An integrated interface for grounded capacitive sensors

Abstract: An interface circuit for grounded capacitive sensors has been designed. The circuit is designed using a simple relaxation-oscillator topology and has been implemented in a 0.7-mum CMOS process. The output signal is a period-modulated square-wave signal, which can directly be processed with a microcontroller. The period time of the output signal is proportional to the measured capacitance. By using the "three-signal" autocalibration methodology, obvious disadvantages from simple relaxation oscillators, such as offset, long-term drift, etc., have been overcome. The paper shows even with a very simple circuit a rather good performance for the measurement of grounded capacitances can be achieved. An active-guard amplifier has been applied to reduce the influence of parasitic capacitances. For the active-guard amplifier, an opamp as well as an operational transconductance amplifier (OTA) have been used. Their performances, regarding to their high-frequency stability and accuracy for large capacitive loads at the working frequency, have been compared. For the measurement range of 100 pF up to 2 muF the nonlinearity is found to be better than 0.5% and the standard deviation less than 20 ppm for a measurement time of 100 ms

A micropower 2 MHz CMOS frequency reference for capacitive sensor applications

Abstract: In this paper, we describe the design of a 2 MHz CMOS frequency reference circuit based on a relaxation oscillator The circuit provides the clock signal for a read-out circuit of a capacitive sensor The frequency reference circuit is always active, thus low power consumption is an essential requirement Supply independent biasing was used to allow supply voltages of 18-25 V without re-calibration Simulations showed that the circuit consumes 30 /spl mu/W with 18 V supply voltage and stays within /spl plusmn/10% of the nominal oscillation frequency in the operating voltage range and at temperatures from -40 to 85/spl deg/C A jitter approximation of /spl Delta/t/sub max/ /spl ap/ 5 ns and phase noise performance were obtained The relative importance of different noise sources on phase noise are highlighted on the basis of phase transfer simulations The circuit is being fabricated in a 013 /spl mu/m CMOS process

Dual-band voltage controlled oscillator utilizing switched feedback technology

Abstract: The present invention is related with a dual-band LC voltage controlled oscillator, which utilizes a substantial amount of feedback loop paths in the circuit. The circuit is a core of a substantial amount of communication ICs. The voltage controlled oscillator can provide wide-band or dual-band radio frequency generation, and it utilizes a switch controlled circuit to select one of the feedback loops in order to choose the assigned frequency band output. Generic wide-band or dual-band LC voltage controlled oscillations are obtained by switching parallel-connected capacitors or switching inductor array, in contrast, the present invention is used for switching several parallel connected feedback loops, each of which associated with an LC tank forms an oscillation frequency output. Utilizing the switch to control the feedback loop and integrating different band oscillator circuit is capable of saving chip's size and power consumption.

Turbo-charged relaxation oscillator method and apparatus

Abstract: A method for producing an oscillating signal comprises: generating an oscillating signal by discharging after charging to a high trigger level and charging after discharging to a low trigger level; and turbo-charging at the initial of a change-over from charging to discharging while resuming a normal charging/discharging thereafter, and vice versa. The present invention makes use of the turbo-charging/discharging for a linear compensation, such that the produced oscillating signal has the features of concurrently eliminating phase noises and jitters as well as maintaining the modulation linearity.

Pattern formation in stiff oscillatory media with nonlocal coupling: a numerical study of the hydrogen oxidation reaction on Pt electrodes in the presence of poisons.

Abstract: The impact of the strength of negative (desynchronizing) global coupling (NGC) on the spatiotemporal dynamics of an electrochemical relaxation oscillator is studied numerically with a prototypical model, the electro-oxidation of hydrogen in the presence of poisons. The results are compared with recent experiments. The NGC has a destabilizing effect on the homogeneous oscillations. Both, in theory and in experiments, the basic patterns found with increasing global coupling strength are modulated oscillations, target patterns (including an asymmetric variant), and modulated pulses, the average spatial inhomogeneity during an oscillation increasing with the intensity of the NGC. It is suggested that this scenario is typical for strong relaxation oscillations, and a comparison with an electrochemical oscillator exhibiting harmonic oscillations points to the fact that the critical coupling strength, upon which the complete synchronization is destroyed, is larger for relaxation oscillations than for harmonic oscillations. In addition, the numerical simulations predicted two- and three-phase cluster patterns at high coupling strength. Also in experiments cluster patterns were observed, however only in parameter regions of the local dynamics which were different from the one investigated in this study.

Apparatus and method for a spread-spectrum oscillator for magnetic switched power converters

Abstract: A method and apparatus for a spread-spectrum oscillator for a switched power converter is provided. The spread-spectrum oscillator includes a current waveform generation circuit, a capacitor, a switch, and a comparator. The capacitor is arranged to receive an oscillator current to provide a ramp voltage. The comparator is arranged to compare the ramp voltage with a reference voltage to provide an oscillator voltage. Further, the switch is arranged to discharge the capacitor when the oscillator voltage is asserted. The current waveform generation is arranged to, if enabled, provide at least a portion of the oscillator current as a triangle wave, or other type of modulating waveform suitable for spread-spectrum. Accordingly, the oscillator voltage is a spread-spectrum signal.

A novel signal conditioning circuit for push-pull-type resistive transducers

Abstract: A novel signal conditioning circuit suitable for push–pull-type resistive transducers is proposed. The circuit developed is capable of providing a linear output over a wide range of values of the measurand. Even when the transducer has an inverse relationship with the measurand, the circuit provides a linear output. The push–pull-type resistive transducer becomes an integral part of a relaxation oscillator, the duty cycle ratio of the output of which becomes proportional to the measurand. Since the output depends only on the relative sensitivity of the transducer and a pair of dc excitation voltages, it is possible to obtain very low errors. The various sources of error in the circuit are analysed and quantitative expressions to estimate such errors are derived. The circuit was set up in the laboratory and the results obtained from the prototype are presented. The prototype possessed an error of ±0.02% of the reading. It is seen that this circuit is not only simple but also produces errors which are much less than those from circuits currently mentioned in the literature.

Circuits for voltage-controlled ring oscillators and method of generating a periodic signal

Abstract: Circuits and methods and for generating oscillator outputs using standard integrated circuit components. The basic circuit generally includes two inverters and a variable capacitor to configure a delay of the circuit input and/or output. The oscillator circuit generally includes a plurality of inverter circuits, at least one of which uses a variable capacitor to adjust a delay between stages, and thereby adjust a frequency of oscillation. Thus, the oscillator outputs may be tuned using a single control voltage. The method generally includes the steps of (1) applying an operating voltage to a ring oscillator comprising a plurality of stages; and (2) applying a control voltage to a variable capacitor coupled to a node between at least two of those stages. The circuits have particular advantage in quadrature oscillators, and may be easily implemented using widely available CMOS technology.

Switching DC-DC converter with improved stabilization

Abstract: The switching DC-DC converter comprises an inductor, a control circuit with an oscillator and an output stage, the output stage being coupled to the inductor, a diode coupled to the inductor, and a feedback loop for generating a stabilized output voltage. An output voltage of the output stage is coupled with an oscillator input of the control circuit, for example via an impedance, for synchronizing an oscillation cycle of the oscillator with a current pulse of the output stage.

Surface-tension-driven nanoelectromechanical relaxation oscillator

Abstract: Because of its linear dependence on length scale, surface tension can be a dominant force for small systems. Properly harnessed, this force is uniquely suited for nanomechanical applications. We have developed a nanoelectromechanical relaxation oscillator with a surface-tension-driven power stroke. The oscillator consists of two liquid metal droplets exchanging mass, and its frequency is directly controlled with a low-level dc electrical voltage. © 2005 American Institute of Physics. fDOI: 10.1063/1.1887827g

Steady-state analysis of voltage and current controlled oscillators

Abstract: This paper introduces the problem of finding the steady-state and the numerical value of the controlling voltage or current for oscillators where the frequency of oscillation is known beforehand. These situations are very common when the oscillator is part of a phase-locked loop (PLL). In PLLs, the reference frequency as well as the divide ratios are known at the time of design. Therefore the desired frequency of the voltage (current) controlled oscillator is known but not the controlling voltage (current). We formulate this problem as the solution of an appropriate nonlinear equation. We present robust and efficient numerical techniques for solving this nonlinear equation both in time and frequency domain. We demonstrate using experimental results that this technique is at par with classical methods of calculating oscillator steady-state and period of oscillation for a given control voltage. We show that compared to a search-based approach to calculating the desired control voltage or current, our direct method is a order of magnitude faster for the same accuracy.

An X-Band Carbon-Doped InGaP/GaAs Heterojunction Bipolar Transistor MMIC Oscillator

Abstract: This paper addresses a fully-integrated low phase noise X-band oscillator fabricated using a carbon-doped InGaP heterojunction bipolar transistor (HBT) GaAs process with a cutoff frequency of 53.2 GHz and maximum oscillation frequency of 70 GHz. The oscillator circuit consists of a negative resistance generating circuit with a base inductor, a resonating emitter circuit with a microstrip line, and a buffering resistive collector circuit with a tuning diode. The oscillator exhibits 4.33 dBm output power and achieves -127.8 dBc/Hz phase noise at 100 kHz away from a 1039 GHz oscillating frequency, which benchmarks the lowest reported phase noise achieved for a monolithic X-band oscillator. The oscillator draws a 36 mA current from a 6.19 V supply with 47.1 MHz of frequency tuning range using a 4 V change. It occupies a 0.8 mm × 0.8 mm die area.

ANEXO F - ARTIGO PARA O CONGRESSO IMOC2005 Analysis of Reverse Feedback Distributed Oscillators with m-derived Artificial Transmission Lines

Abstract: This paper presents a linear analysis of the reverse feedback distributed oscillator, which is a wideband voltage controlled oscillator proposed by Skvor, et al. (1) based on the distributed amplifier. The theoretical analysis presented in (1) was generalized for a distributed oscillator employing m-derived artificial transmission lines. The resulting equations allow predicting the circuit oscillation frequency behavior and the corresponding required minimum transistor transconductances. A design example is described for a three-octave oscillator. Index Terms — Distributed amplifier, microwave integrated circuits, microwave FET oscillators, MMIC oscillators, tunable oscillators.

Voltage to frequency converter for DAC test

Abstract: In this paper a modified relaxation oscillator is proposed as the core of an analog to digital modulator for on chip signal extraction for test. The architecture uses digital current source generation and digital switching in place of active circuitry. The resulting design allows for high input sensitivity, robustness to component variation while occupying little silicon area. This paper provides solutions on the main challenges in implementing this modulator and how it may be integrated with a digital based tester.

Relaxation oscillator and relative operation method.

Abstract: The present invention describes an oscillator comprising at least one capacitor (C), at least one comparator (1) and at least one device (2) suitable for charging or discharging said at least one capacitor (C). The capacitor is coupled with the comparator (1) and the latter is suitable for comparing the voltage on the capacitor (C) with a reference voltage (Vref) and is suitable for activating the device (2) for commanding the charging or the discharging of the capacitor (C). The oscillator comprises means (3) for the application of a preset voltage value (Voff) in input to the comparator (1) when said device (2) commands the charging of said capacitor (C); the comparator (1) is suitable for comparing the reference voltage (Vref) diminished by the preset voltage value (Voff) with the voltage on the capacitor or the voltage on the capacitor added to the preset voltage value (Voff) with the reference voltage (Vref).

Two wire oscillator system for determining body impedance

Abstract: An apparatus for determining body impedance comprising: first and second electrodes suitable for being electrically coupled to the body; and a variable frequency relaxation oscillator coupled to the electrodes; wherein, the period of oscillation is indicative of the body impedance.

Automatic gain control circuit and method and super-regenerative RF receiver

Abstract: An automatic gain control (AGC) circuit is applied to control a margin voltage of an oscillator The margin voltage is the voltage difference between a high-level output and a low-level output of the oscillator The AGC circuit of the present invention includes a comparator and a processing unit Wherein, the comparator compares the margin voltage of the oscillator and a reference voltage Based on the output of the comparator, the processing unit outputs a ripple code to determine the value of a driving current output from a current generator The oscillator generates an oscillation output to the comparator based on the driving current

Semiconductor Integrated Circuit Device and Mobile Device Using Same

Abstract: An IC includes an internal circuit that switches between on-state and off-state in response to an external signal and also includes an oscillator circuit that is externally synchronized. The IC further includes a state holding circuit that, when pulses for synchronizing the oscillator circuit are inputted to a standby pulse input terminal, applies, to the internal and the oscillator circuits, as an operation signal, a voltage obtained by rectifying pulses outputted from a comparator, and, when a constant voltage for non-operation is applied to the standby pulse input terminal for a given time period, applies, to the internal and oscillator circuits, as a non-operation signal, a constant voltage outputted from the comparator.

Spontaneous generation of giant pulses in a diode-pumped Nd:YVO4 laser.

Abstract: Spontaneous generation of giant pulses was observed from a diode-pumped Nd:YVO4 laser with a plane-concave resonator by adjusting the cavity length near the hemispherical resonator configuration and misaligning the cavity axis with respect to the pump beam. Self-pulsation occurs because of the beating among near degenerate modes being tuned to resonate with the relaxation oscillation of laser modes. By using a concave mirror of 10-mm radius of curvature, giant pulses were obtained at approximately 10 kHz with pulse widths as short as 2.4 ns corresponding to an increase in the peak power of more than 4×104 times over the cw level.

Injection locking phenomena of Van der Pol oscillator

Abstract: Van der Pol oscillator can be used to model microwave negative oscillator, and injection locked oscillator can be looked as forced Van der Pol oscillator. The article studies the amplitude and phase dynamics of the forced Van der Pol oscillator, and gets conditions under which injection locking phenomena can occur. Injection locked Van der Pol oscillator is also realized with a simple modern semiconductor circuit in the article. At last OrCAD PSpice is used to simulate the circuit and testify the conclusions got by theory analyzing.