Showing papers on "Pulse-frequency modulation published in 2001"

Application of empirical mode decomposition to heart rate variability analysis.

Abstract: The analysis of heart rate variability, involving changes in the autonomic modulation conditions, demands specific capabilities not provided by either parametric or non-parametric spectral estimation methods. Moreover, these methods produce time-averaged power estimates over the entire length of the record. Recently, empirical mode decomposition and the associated Hilbert spectra have been proposed for non-linear and non-stationary time series. The application of these techniques to real and simulated short-term heart rate variability data under stationary and non-stationary conditions is presented. The results demonstrate the ability of empirical mode decomposition to isolate the two main components of one chirp series and three signals simulated by the integral pulse frequency modulation model, and consistently to isolate at least four main components localised in the autonomic bands of 14 real signals under controlled breathing manoeuvres. In addition, within the short time-frequency range that is recognised for heart rate variability phenomena, the Hilbert amplitude component ratio and the instantaneous frequency representation are assessed for their suitability and accuracy in time-tracking changes in amplitude and frequency in the presence of non-stationary and non-linear conditions. The frequency tracking error is found to be less than 0.22% for two simulated signals and one chirp series.

Ultrasonic transducer drive unit

Abstract: PROBLEM TO BE SOLVED: To provide an ultrasonic transducer drive unit capable of increasing percent modulation with a simple structure. SOLUTION: A control system is set to that an ultrasonic transducer 3 is driven in its resonance frequency by a driving signal from a driving signal generation means 5 and that the driving signal generation means 5 follows the resonance frequency by feedback signals from a detection circuit 7. Additionally, signals for modulation are sent from a modulating signal generation means 11 to modulate the frequency of the driving signal. As a result, large modulation can be performed by a small signal for modulation by using a frequency characteristic that load impedance changes significantly in the vicinity of the resonance frequency of the ultrasonic transducer 3. COPYRIGHT: (C)2002,JPO

DC/DC converter including control means for controlling multiple outputs using separate switching cycles for each output

Abstract: A DC/DC converter ( 10; 30; 40; 50; 60 ), comprising inductive energy storage means ( 2 ), switching means (S 0 -S 7 ) and control means ( 9; 31; 41; 51; 61 ), wherein said control means ( 9; 31; 41; 51; 61 ) are arranged for selectively operating said switching means (S 0 -S 7 ) for providing electrical energy from said energy storage means ( 2 ) to an output (A; B; C; D) of said DC/DC converter ( 10; 30; 40; 50; 60 ) in both a Pulse Width Modulation (PWM) mode and a Pulse Frequency Modulation (PFM) mode switching cycle. The control means ( 9; 31; 41; 51; 61 ) are arranged for controlling multiple outputs (A; B; C; D) of said DC/DC convertor ( 10; 30; 40; 50; 60 ) by providing a sequence (T) of a number of separate switching cycles for each output (A; B; C; D), and for establishing a main output among said multiple outputs (A; B; C; D) requiring the highest amount of energy, wherein said main output in PWM mode determines the total amount of energy to be supplied in a sequence (T) and the number of switching cycles of an output in PWM mode is determined by part of the total amount of energy to be supplied at said output.

Second-order temporal modulation transfer functions

Abstract: Detection thresholds were measured for a sinusoidal modulation applied to the modulation depth of a sinusoidally amplitude-modulated (SAM) white noise carrier as a function of the frequency of the modulation applied to the modulation depth (referred to as f'm). The SAM noise acted therefore as a "carrier" stimulus of frequency fm, and sinusoidal modulation of the SAM-noise modulation depth generated two additional components in the modulation spectrum: fm-f'm and fm+f'm. The tracking variable was the modulation depth of the sinusoidal variation applied to the "carrier" modulation depth. The resulting "second-order" temporal modulation transfer functions (TMTFs) measured on four listeners for "carrier" modulation frequencies fm of 16, 64, and 256 Hz display a low-pass segment followed by a plateau. This indicates that sensitivity to fluctuations in the strength of amplitude modulation is best for fluctuation rates f'm below about 2-4 Hz when using broadband noise carriers. Measurements of masked modulation detection thresholds for the lower and upper modulation sideband suggest that this capacity is possibly related to the detection of a beat in the sound's temporal envelope. The results appear qualitatively consistent with the predictions of an envelope detector model consisting of a low-pass filtering stage followed by a decision stage. Unlike listeners' performance, a modulation filterbank model using Q values > or = 2 should predict that second-order modulation detection thresholds should decrease at high values of f'm due to the spectral resolution of the modulation sidebands (in the modulation domain). This suggests that, if such modulation filters do exist, their selectivity is poor. In the latter case, the Q value of modulation filters would have to be less than 2. This estimate of modulation filter selectivity is consistent with the results of a previous study using a modulation-masking paradigm [S. D. Ewert and T. Dau, J. Acoust. Soc. Am. 108, 1181-1196 (2000)].

Frequency doubling of phase-modulated, ultrashort laser pulses

Abstract: We have investigated theoretically and experimentally the generation of shaped pulses at 400 nm by frequency-doubling of phase-modulated, ultrashort laser pulses. We present an analytical description of frequency-doubled pulses with a sinusoidal spectral phase modulation. It is shown that such a phase modulation can be transferred completely into a spectral amplitude modulation with a resolution determined only by the phase-modulating device. A criterion for achieving the maximum modulation contrast is given.

Method of and apparatus for performing modulation

Abstract: A modulator and a method of modulating utilizes phase or frequency modulation and amplitude modulation. A delay circuit or synchronization circuit is utilized to coordinate the performance of amplitude modulation and phase modulation. The amplitude modulation can be provided after phase modulation is provided to the signal. The modulation circuit can be utilized in any frequency range including high frequency and low frequency circuits.

Modulation circuit, image display using the same, and modulation method

Abstract: A modulation circuit capable of high resolution pulse width modulation while keeping down the bit length and an image display provided with the modulation circuit. By the A/D converter 4 , the video signal Sv converted into a binary code having a preset bit length is divided into a plurality of binary codes by the controller 3 from the most significant bit to the least significant bit. Corresponding to the thus obtained plurality of divided binary codes, serial data is generated for producing a pulse current of a pulse width and current value according to the value of the binary code and is output to pulse width modulation circuits 1 cascade connected to the controller 3 . The pulse width modulation circuits supply LEDs 3 of the pixels pulse currents of pulse widths and current values corresponding to the serial data.

Ultrasonic nonlinear imaging at fundamental frequencies

Abstract: Nonlinear tissue or contrast agent effects are detected by combining echoes from multiple, differently modulated transmit pulses below the second harmonic band. The received echoes may even overlap the fundamental transmit frequency band. The modulation may be amplitude modulation or phase or polarity modulation, and is preferably both amplitude and phase or modulation. The present invention affords the ability to utilize a majority of the transducer passband for both transmission and reception, and to transmit pulses which are less destructive to microbubble contrast agents.

Fm-cw radar device

Abstract: An FM-CW radar device in which an FM modulated wave outputted from a modulated signal generator has a gradient (modulation gradient) of frequency variation with respect to the time axis. The radar device comprises means for controlling the modulated frequency width or modulation period of a modulation signal to vary the modulation gradient. Further comprised is means for detecting a signal component changing with a change of the modulation gradient to discriminate the signal from a target object from other signals. In the case of an FM-CW radar device in which the transmission, the reception, or the transmission and reception are carried out by a time-division ON-OFF control, there is further comprised means for detecting the signal which changes with a change, if made, of the frequency for the ON-OFF control, thereby to discriminate the signal the target object from other signals.

A system and method for determining the frequency of longitudinal mode required for color mixing in a discharge lamp

Abstract: In a power source system, a method for providing color mixing in a high intensity discharge (HID) lamp comprises the steps of providing a swept frequency signal having a sweeping frequency ranging between a first lower frequency value and a second higher frequency value, within a specified period. An amplitude modulation signal is also provided having an adjustable frequency value and an adjustable modulation index. As a result the sweeping frequency signal is modulated by said amplitude modulation signal. The frequency of the amplitude modulation signal is adjusted until a maximum lamp voltage is detected. Thereafter, the system operates with a modulating frequency that yields the maximum lamp voltage so as to substantially eliminate color segregation in the lamp.

An ac method for the precise measurement of Q-factor and resonance frequency of a microwave cavity

Abstract: We have developed a new and fast method for the determination of the complex frequency shift of a microwave resonant cavity. The method is based on frequency modulation of the microwave source around the cavity resonance and detection of the 2nd and 4th harmonic of the modulation frequency. With this procedure the static measurement of the response amplitude is not necessary and all the data are obtained through a single ac channel. The optimal frequency deviation is shown to be comparable to the cavity resonance width.

Pulse-width optimization in a pulse density modulated high frequency AC-AC converter using genetic algorithms

Abstract: As the size and the cost of power semiconductor switches are decreasing, converter topologies with high device count are starting to draw more attention. One such type of converter is the high frequency AC (HFAC) link converters. A popular control method for these converters is pulse density modulation (PDM). The HFAC link voltage of the converter in this paper is a high frequency, three-step, variable pulse-width (PW) square wave voltage waveform. A genetic algorithm approach is used to determine the PW to optimize the output voltage harmonic content.

Power supply pulse width modulation (PWM) control system

Abstract: A power supply pulse width modulation (PWM) control system uses peak current program mode (CPM) control for large duty ratios with a smooth transition to voltage mode control at small duty ratios down to zero duty ratio. The PWM control system implements the latch function in an analog, circuit in contrast with commonly employed digital solutions, further resulting in low delay times since it does not have logic and set-up delays that are associated with latches.

Impulses and stochastic arithmetic for signal processing

Abstract: Explores the use of Poisson point processes and stochastic arithmetic to perform signal processing, functions. Our work is inspired by the asynchrony and fault tolerance of biological neural systems. The essence of our approach is to code the input signal as the rate parameter of a Poisson point process, perform stochastic computing operations on the signal in the arrival or "pulse" domain, and decode the output signal by estimating the rate of the resulting process. An analysis of the Poisson pulse frequency modulation encoding error is performed. Asynchronous, stochastic computing operations are applied to the impulse stream and analyzed. A special finite impulse response (FIR) filtering scheme is proposed that preserves the Poisson properties and allows filters to be cascaded without compromising the ideal signal statistics.

Improving crest factor of electronic ballast-fed fluorescent lamp current using pulse frequency modulation

Abstract: In case where electronic ballast employing a valley-fill passive power-factor correction (PFC) circuit is used for feeding fluorescent tamps, a new method to reduce crest factor of the lamp current is studied in this paper. It is known that a 50% valley-fill passive PFC provided for high input power factor results in undesirable value of crest factor of the fluorescent lamp current, In order to reduce crest factor to a lower value, a pulse frequency modulation technique based on the waveform of the DC-link voltage which is predetermined by the passive PFC circuit is taken into the switching control action of the electronic ballast. An equation-based analysis between the crest factor of lamp current and the effect of varying the inverter switching frequency is comprehensively performed. Several simulation and experiment results illustrate the Effectiveness of the proposed control scheme.

Current sensor with frequency output

Abstract: A device measures current magnitude in a conductor coupled to an electrical device and generates a signal comprising a series of pulses having a frequency. The frequency of the series of pulses is responsive to the magnitude of current measured. The device comprises a sensor magnetically linked with the conductor connected to the electrical device. The sensor produces an analog signal in response to the presence of a current within the conductor. A signal conditioner is located proximate to the sensor and is electrically coupled to the sensor so as to receive the analog signal. The signal conditioner produces, in response to the analog signal, a first signal representative of a magnitude of the current. A converter receives and converts the first signal into an output signal that comprises a series of pulses having a frequency. The frequency of the series of pulses is responsive to the magnitude of the current. All the sensor, the signal conditioner, and the converter are located in a single unitary package.

System and method for employing pulse width modulation with a bridge frequency sweep to implement color mixing lamp drive scheme

Abstract: A gas discharge lamp is driven by a bridge circuit which produces a pulse voltage signal. The bridge circuit is pulse width modulated at an operational frequency, and has a power input for receiving power from a power source, and a control signal input for receiving a control signal that effects sweeping of the operational frequency and generation of the pulse voltage signal. The system further includes a controller for controlling the bridge circuit, the controller comprising circuitry for (i) generating a signal comprising a frequency swept signal that is amplitude modulated by a fixed frequency signal, the highest frequency of the frequency swept signal being lower than the operational frequency, and the signal generated by the controller being inputted into the control signal input of the bridge circuit, and (ii) periodically sweeping the operational frequency of the bridge circuit. The system further includes a filter circuit for filtering the pulse voltage signal.

A multi-output dc/dc converter in pfm/pwm mode

Abstract: A DC/DC converter (10; 30; 40; 50; 60), comprising inductive energy storage means (2), switching means (S0-S7) and control means (9; 31; 41; 51; 61), wherein said control means (9; 31; 41; 51; 61) are arranged for selectively operating said switching means (S0-S7) for providing electrical energy from said energy storage means (2) to an output (A; B; C; D) of said DC/DC converter (10; 30; 40; 50; 60) in both a Pulse Width Modulation (PWM) mode and a Pulse Frequency Modulation (PFM) mode switching cycle The control means (9; 31; 41; 51; 61) are arranged for controlling multiple outputs (A; B; C; D) of said DC/DC convertor (10; 30; 40; 50; 60) by providing a sequence (T) of a number of separate switching cycles for each output (A; B; C; D), and for establishing a main output among said multiple outputs (A; B; C; D) requiring the highest amount of energy, wherein said main output in PWM mode determines the total amount of energy to be supplied in a sequence (T) and the number of switching cycles of an output in PWM mode is determined by part of the total amount of energy to be supplied at said output

A FMCW laser range-finder based on a delay line technique

Abstract: A laser range-finder has been designed for distances from 1 m to 20 m with diffusing targets The measurement principle using a frequency modulation continuous wave technique is firstly described Triangular and sine frequency modulation types are both analyzed Improvements for short distance measurements and for low noise photoreception are then proposed The designed set-up is also theoretically compared to a phase-shift laser range-finder in order to point up its main advantages

FM-CW radar system

Abstract: In an FM-CW radar system, a frequency modulating said modulating wave output from said modulating signal generator has a frequency variation skew with respect to a time axis (modulation skew), and the radar system includes a means for varying the modulation skew by controlling the modulation frequency amplitude or modulation period of the modulating signal. The radar system further includes a means for discriminating a signal component varying in response to the variation of the modulation skew, thereby discriminating a signal related to a target object from other signals. In the case of an FM-CW radar system that performs transmission and/or reception by time division ON-OFF control the radar system includes a means for discriminating a signal which, when the frequency used to perform the ON OFF control is varied, varies in response to the variation of the frequency, thereby discriminating a signal related to a target object from other signals.

Wireless audio transmission system

Abstract: A wireless audio transmission and reception system includes a pulse width amplifier, an up-converter, a transmitter, a receiver, a down-converter, an integrator, and a power amplifier to transfer an analog signal to a transducer such as a speaker. The pulse width amplifier receives an analog signal and modulates a pulse width of a timing signal with the analog signal. The pulse width of the timing signal is modulated such that the pulse width is proportional to the amplitude of the analog signal, and provides a pulse width modulated signal. The up-converter is in communication with the pulse width amplifier to receive the pulse width modulated signal and convert the pulse width modulated signal to a modulated carrier signal. The transmitter in communication with the up-converter to receive the modulated carrier signal and to transfer the modulated carrier signal wirelessly. The receiver receives the modulated carrier signal and transfers the modulated carrier signal to the down-converter that extracts the pulse width modulated signal from the modulated carrier signal. The down-converter transfers the extracted pulse width modulated signal to the integrator, which then restores the analog signal. The integrator transfers the recovered analog signal to the power amplifier for amplification and transfer to the transducer or speaker.

Generating methods for single and multi-channel wideband optical analog pulse positioned waveforms

Abstract: A method and system for generating single and multi-channel optical analog pulse-position modulation waveforms are disclosed. The system comprises a frequency modulator, a continuous wave optical source, and an optical modulator. The frequency modulator receives the analog signal and converts the analog signal into a frequency modulated signal. The optical modulator modulates the continuous wave optical source with the frequency modulated signal, to produce the optical pulse-position modulated signal. The method comprises converting an analog input signal into a frequency modulated signal amplifying the frequency modulated signal and producing a large signal therein, modulating a continuous wave optical source with the large signal, therein producing the optical pulse-position modulation signal, and compressing the optical pulse-position modulation signal, therein increasing a processing gain.

Distortion properties of the interval spectrum of IPFM generated heartbeats for heart rate variability analysis

Abstract: The integral pulse frequency modulation (IPFM) model converts a continuous-time signal into a modulated series of event times, often represented as a pulse train. The IPFM process is important to the field of heart rate variability (HRV) as a simple model of the sinus modulation of heart rate. Here, the authors discuss the distortion properties associated with employing the interval spectrum for the recovery of the input signal from an IPFM process's output pulse train. The results state, in particular for HRV, how precisely the interval spectrum can be used to infer the modulation signal responsible for a series of heartbeats. The authors have developed a detailed analytical approximation of the interval spectrum of an IPFM process with multiple sinusoids as the input signal. Employing this result, they describe the structure and the distortion of the interval spectrum. The distortion properties of the interval spectrum are investigated systematically for a pair of frequency components. The effects of linear and nonlinear distortion of the fundamentals, the overall contribution of harmonic components to the total power, the relative contribution of "folded back" power due to aliasing and the total distortion of the input spectrum are investigated. The authors also provide detailed comparisons between the interval spectrum and the spectrum of counts (SOC). The spectral distortion is significant enough that caution should be taken when interpreting the interval spectrum, especially for high frequencies or large modulation amplitudes. Nevertheless, the distortion levels are not significantly larger than those of the SOC. Therefore, the spectrum of intervals may be considered a viable technique that suffers more distortion than the SOC.

A system and method for employing pulse width modulation for reducing vertical segregation in a gas discharge lamp

Abstract: In accordance with one embodiment of the present invention a system for driving a gas discharge lamp is comprised of a bridge circuit configured to provide a pulse voltage signal, a controller configured to generate a pulse width modulated signal corresponding to a desired waveform. A filter circuit is also configured to receive and filter the pulse voltage signal provided by the bridge circuit. In one embodiment of the invention the gas discharge lamp is driven by a pulse voltage signal corresponding to a pulse width modulation signal. The pulse width modulated signal is generated corresponding to a desired waveform, wherein the desired waveform includes a sweeping frequency signal and a fixed frequency amplitude modulating signal.

Adaptive modulation radio communication device

Abstract: PROBLEM TO BE SOLVED: To provide an adaptive modulation radio communication device in which a received quality can be improved by taking into account fading fluctuation when using the estimated value of a maximum Doppler frequency SOLUTION: In modulation multilevel number control parts 53 and 63, the estimated value of a maximum Doppler frequency fd is inputted to a comparison part 72 When the value is equal to or lower than a prescribed threshold Th 1 , an adaptive modulation system is adopted according to a first modulation parameter selection chart 83 When the value exceeds the prescribed threshold Th 1 but is equal to or lower than a prescribed threshold Th 2 , an adaptive modulation system according to a third modulation parameter selection chart 83 is adopted In this third modulation parameter selection chart 83, a modulation multilevel number is lowered for one stage in order to improve the transmission quality in comparison with the first modulation parameter selection chart 73 When the estimated value of the maximum Doppler frequency fd exceeds the prescribed threshold Th 2 , a QPSK modulation system having the minimum modulation multilevel number is used COPYRIGHT: (C)2003,JPO

Digital multi-train control with bi-directional data transmission in model railways

Abstract: A method and device which digitally controls moveable and/or stationary electrical consumers in a model railway. The power for the consumers is supplied over the track in the form of a square wave voltage signal which is frequency and/or pulse width modulated according to digital control information for the consumers generated by a central control unit of the model railway. A consumer, after having received a control information addressed to said consumer, applies a return signal to the track, which return signal has a higher frequency than the frequency of the modulated square wave voltage. This return signal is detected by synchronising the detection to the square wave voltage such that the return signal is detected in periods of the square wave voltage signal which are free of signal edges.

Voltage-controlled oscillator with ac coupling to produce highly accurate duty cycle square wave output

Abstract: A voltage-controlled oscillator circuit includes a ring oscillator circuit for generating a signal having a series of pulses. The signal with the series of pulses is ac coupled to a filter circuit which converts the series of pulses into a substantially sinusoidal signal which is substantially symmetrical about the reference potential of the system. The sinusoidal signal is applied to an amplifier which converts the sinusoidal signal into a square wave. Because the square wave is generated as an amplified sine, wave, it exhibits a high degree of symmetry, i.e., it has a highly accurate 50-50 duty cycle, which makes it applicable in demanding settings such as serving as a clock signal in a high-speed microprocessor system in which both rising and falling edges of the clock signal are used to synchronize events.

Digital modulation synthesizer

Abstract: The invention concerns a digital modulation synthesizer for generating an output frequency or phase modulated radiofrequency signal (SOUT), comprising a pre-accentuation filter (18) receiving a frequency modulation digital signal (Fmod) in input to produce a pre-accentuated frequency modulation signal (F'mod), a modulator Σ-Δ (15) having an input receiving the pre-accentuated frequency modulation signal (F'mod), and an output delivering a pre-accentuated and scrambled frequency modulation signal (SC), a phase locked loop (PLL) with variable radio frequency divider (14) in the feedback path, the filtering by the phase locked loop (PLL) enabling to filter the quantizing distortion introduced by the modulator Σ-Δ (15) and the pre-accentuation filter (18) applying a pre-accentuation to the frequency modulation signal (Fmod) enabling to compensate the effect of said filtering on the modulation inside a usful band, means for automatic calibration of the pre-accentuation filter (18) enabling further to adjust the pre-accentuation filter (18) function to that of the PLL.

Voltage-controlled oscillator for frequency modulation

Abstract: A voltage-controlled oscillator for frequency modulation includes an oscillator core with a tunable resonant circuit component which is driven with a control voltage. Furthermore, a modulator component is provided which is driven with a modulation signal for frequency modulation. The modulator component is additionally coupled to the terminal for supplying the control voltage. As a result, a constant modulation deviation can be achieved over the entire tuning range even in the case of oscillators having a large tuning range. The oscillator circuit is particularly suitable for use in transmitting circuits for digital communication.

Phase and amplitude digital modulation circuit and method

Abstract: The invention concerns a method and a circuit for modulating a carrier signal (Se) with a signal (SCj) comprising at least a modulation cell (CMi) by phase shift for receiving two digital control signals (Scji, SCji2) representing at least part of the digital modulation signal (SCj). For at least a value of the digital modulation signal (SCj), the method consists in applying on at least a common modulation cell (CMi), two digital control signals (SCji1, SCji2) of identical value, said modulation cell (CMi) delivering a signal, called modulated elementary signal (Ssi), which is null for said digital modulation signal value (SCj).