Showing papers on "Pulse-frequency modulation published in 2002"

Method and system for frequency up-conversion

Abstract: A method and system is described wherein a signal with a lower frequency is up-converted to a higher frequency. In one embodiment, the higher frequency signal is used as a stable frequency and phase reference. In another embodiment, the invention is used as a transmitter. The up-conversion is accomplished by controlling a switch with an oscillating signal, the frequency of the oscillating signal being selected as a sub-harmonic of the desired output frequency. When the invention is being used as a frequency or phase reference, the oscillating signal is not modulated, and controls a switch that is connected to a bias signal. When the invention is being used in the frequency modulation (FM) or phase modulation (PM) implementations, the oscillating signal is modulated by an information signal before it causes the switch to gate the bias signal. In the amplitude modulation implementation (AM), the oscillating signal is not modulated, but rather causes the switch to gate a reference signal that is substantially equal to or proportional to the information signal. In the FM and PM implementations, the signal that is output from the switch is modulated substantially the same as the modulated oscillating signal. In the AM implementation, the signal that is output from the switch has an amplitude that is a function of the information signal. In both embodiments, the output of the switch is filtered, and the desired harmonic is output.

Spectro-temporal processing in the envelope-frequency domain

Abstract: The frequency selectivity for amplitude modulation applied to tonal carriers and the role of beats between modulators in modulation masking were studied. Beats between the masker and signal modulation as well as intrinsic envelope fluctuations of narrow-band-noise modulators are characterized by fluctuations in the “second-order” envelope (referred to as the “venelope” in the following). In experiment 1, masked threshold patterns (MTPs), representing signal modulation threshold as a function of masker-modulation frequency, were obtained for signal-modulation frequencies of 4, 16, and 64 Hz in the presence of a narrow-band-noise masker modulation, both applied to the same sinusoidal carrier. Carrier frequencies of 1.4, 2.8, and 5.5 kHz were used. The shape and relative bandwidth of the MTPs were found to be independent of the signal-modulation frequency and the carrier frequency. Experiment 2 investigated the extent to which the detection of beats between signal and masker modulation is involved in tone-in-noise (TN), noise-in-tone (NT), and tone-in-tone (TT) modulation masking, whereby the TN condition was similar to the one used in the first experiment. A signal-modulation frequency of 64 Hz, applied to a 2.8-kHz carrier, was tested. Thresholds in the NT condition were always lower than in the TN condition, analogous to the masking effects known from corresponding experiments in the audio-frequency domain. TT masking conditions generally produced the lowest thresholds and were strongly influenced by the detection of beats between the signal and the masker modulation. In experiment 3, TT masked- threshold patterns were obtained in the presence of an additional sinusoidal masker at the beat frequency. Signal-modulation frequencies of 32, 64, and 128 Hz, applied to a 2.8-kHz carrier, were used. It was found that the presence of an additional modulation at the beat frequency hampered the subject’s ability to detect the envelope beats and raised thresholds up to a level comparable to that found in the TN condition. The results of the current study suggest that (i) venelope fluctuations play a similar role in modulation masking as envelope fluctuations do in spectral masking, and (ii) envelope and venelope fluctuations are processed by a common mechanism. To interpret the empirical findings, a general model structure for the processing of envelope and venelope fluctuations is proposed.

Method and system for frequency up-conversion with a variety of transmitter configurations

Abstract: A method and system is described wherein a signal with a lower frequency is up-converted to a higher frequency. In one embodiment, the higher frequency signal is used as a stable frequency and phase reference. In another embodiment, the invention is used as a transmitter. The up-conversion is accomplished by controlling a switch with an oscillating signal, the frequency of the oscillating signal being selected as a sub-harmonic of the desired output frequency. When the invention is being used as a frequency or phase reference, the oscillating signal is not modulated, and controls a switch that is connected to a bias signal. When the invention is being used in the frequency modulation (FM) or phase modulation (PM) implementations, the oscillating signal is modulated by an information signal before it causes the switch to gate the bias signal. In the amplitude modulation implementation (AM), the oscillating signal is not modulated, but rather causes the switch to gate a reference signal that is substantially equal to or proportional to the information signal. In the FM and PM implementations, the signal that is output from the switch is modulated substantially the same as the modulated oscillating signal. In the AM implementation, the signal that is output from the switch has an amplitude that is a function of the information signal. In both embodiments, the output of the switch is filtered, and the desired harmonic is output.

Proposal of Application of Pulsed Vision Chip for Retinal Prosthesis.

Abstract: A vision chip based on pulse frequency modulation (PFM) is proposed as a retinal prosthesis device for use in subretinal implantation. A pixel circuit of PFM has been fabricated using standard CMOS technology. A dynamic range of 40 dB is demonstrated at a low power supply voltage of 1 V. It is found that the competition between the charge current to the photodiode and the photocurrent affects the output pulse characteristics under the conditionds of low power supply voltage and strong light illumination. For in vitro and in vivo experiments, two methods of improving the PFM circuits are considered. One is controlling the pulse frequency. By adding one transistor to the PFM circuit, the output pulse frequency can be experimentally controlled by a factor of two. The other is using a biphasic output, which is required to keep a charge balance in a living body. By introducing differential circuits, the biphasic output has been confirmed by simulation.

Concise modulation strategies for four-leg voltage source inverters

Abstract: Continuous and discontinuous pulse-width modulation (PWM) schemes and a novel space vector modulation methodology are proposed in this paper for four-leg DC-AC inverters. Using a space vector definition that includes the zero sequence voltage component and partitioning the feasible sixteen modes into two separate sets-one set having zero sequence voltages with positive magnitudes and the other set with the zero sequence voltages with negative magnitudes-the novel space vector implementation technique is determined as also the discontinuous carrier based PWM scheme. For the continuous carrier based PWM scheme, the indeterminate defining output voltage equations expressed in terms of the existence functions of the switching devices are solved using an optimization technique. The modulation schemes determined are shown by experimental results to synthesis any desirable balanced or unbalanced three-phase voltage sets when operating in the linear modulation region.

Delta-sigma modulation apparatus and signal amplification apparatus

Abstract: A signal amplification apparatus in which an input signal is subjected to delta-sigma modulation and the resultant signal S1 is pulse-width modulated to obtain a PWM signal S2, which is amplified to a signal S3 of a predetermined size by an amplifier. The signal amplification apparatus includes a correction circuit (104) for correcting output of quantization unit (103) of a delta-sigma modulation apparatus (10). By arranging the correction circuit (104) on a feedback path to the input from the quantization unit (103) or immediately before a pulse modulation unit (11), distortion generated in the amplifier is corrected. Moreover, the signal amplification apparatus compares PWM signals at the input/output of the amplifier and corrects the output of the quantization unit (103) of the delta-sigma modulation apparatus (10) so as to cancel the distortion amount generated in the amplification unit according to each rise time difference and breaking time difference, thereby correcting the distortion generated in the amplifier.

Transmitting circuit apparatus and method

Abstract: A transmitting circuit apparatus has a frequency modulator that performs frequency modulation of a carrier wave with frequency modulation data and outputs the frequency-modulated carrier wave; a sigma-delta modulator which performs sigma delta modulation of amplitude modulation data; and an amplitude modulator that performs amplitude modulation of the frequency-modulated carrier wave with an output signal of the sigma-delta modulator and outputs the amplitude-modulated carrier wave.

Direct modulation architecture for amplitude and phase modulated signals in multi-mode signal transmission

Abstract: Multiple-mode direct phase/amplitude modulation circuitry ( 20 ) for use in a transceiver ( 17 ) of a device such as a wireless handset ( 10 ) is disclosed. The modulation circuitry ( 20 ) includes a modulation loop ( 36 ) for modulating a phase signal into a Gaussian-Minimum-Shift-Keyed (GMSK) signal for transmission in a first mode. The modulation loop ( 36 ) may include a phase-locked loop ( 45 ) with its frequency controlled by a Σ-Δ demodulation of a compensated version of the phase signal, or alternatively may produce a modulated signal from a direct digital synthesis circuit ( 70; 70′ ). An amplitude signal is converted into an analog signal and applied to a single-sideband mixer ( 43 ) for combination with a frequency multiplied version of the phase-modulated signal (GMSK(t); PH(t)), producing an amplitude and phase modulated signal for transmission in a second mode.

Amplitude- and frequency- or phase-modulated radio frequency signal generator and the transmitter incorporating same

Abstract: An amplitude- and frequency- or phase-modulated radio frequency signal generator that is used for radio emission, generates a phase or frequency control signal and an amplitude control signal from a phase or frequency modulation signal and from an amplitude modulation signal respectively. The generator comprises a phase or frequency modulator and a variable-gain radio frequency power amplifier. The amplitude of the output signal is automatically controlled. In addition, adaptive pre-distortion is carried out in order to pre-distort the phase or frequency control signal in accordance with the amplitude modulation signal during a permanent operating phase. During a learning phase, a pre-distortion module is adapted from the amplitude modulation signal and from the amplitude control signal.

A CMOS imager with PFM/PWM based analog-to-digital converter

Abstract: An on-pixel analog-to-digital converter based on both PFM and PWM schemes is reported. The proposed architecture uses a limited number of transistors that can be implemented in a small silicon area resulting in a 23% fill-factor. The digital sensor can be externally configured in order to operate under either the PFM or PWM scheme. At high light intensities, the PFM scheme is replaced by the PWM scheme which proves to be much more efficient in terms of power consumption and clock frequency requirements. An in-built light adaptation mechanism has also been implemented which allows the sensor to better adapt to low-light intensity or to adjust the sensor saturation level. As a consequence, the sensor features a programmable dynamic range. Image lag is reduced in both schemes since a reset of the photodetector is performed after the conversion period. The pixel based ADC has been designed and fabricated using CMOS 0.25 /spl mu/m technology.

Digital modulation device in a system and method of using the same

Abstract: A wireless digital transmission and receiving method combines phase reversal keying with pulse position modulation. Modulation of a transmitted signal implements pulses that are of extremely short duration to indicate ones and zeros (22). These pulses can be as narrow as one cycle of the carrier frequency (25). The method synthesizes a sideband with no carrier or other sidebands from the carrier of an input signal. This synthesized sideband is represented by a broad sinx/x spectrum with a principal power peak at the modulated frequency and numerous weaker peaks of varying frequencies and peak levels. The result is a strong signal in the form of a synthesized single sideband with all the useful modulation in the brief phase reversal period with a constant signal in the remainder of the bit period that can be used to establish a reference to create uniform time rise and amplitude.

Method and apparatus for suppressing stimulated brillouin scattering in fiber links

Abstract: Method and apparatus for producing a laser output having stimulated Brillouin scattering (SBS) suppression characteristics. An excitation signal is provided to an optical path length adjustment element in an external cavity laser to modulate the optical path length of the cavity. This produces a laser output having a wavelength modulation frequency and line width that are a function of the frequency and amplitude of the excitation signal. Under appropriate modulation frequency and line width combinations, the laser output comprises an optical signal with SBS suppression characteristics, thus enabling a higher power signal to be launched into a fiber link since the SBS suppression characteristics raise the SBS threshold of the link. The optical path length modulation also produces an intensity (amplitude) modulation in the laser output. A detector is employed to produce a feedback signal indicative of the intensity modulation that is used for tuning the laser in accordance with a wavelength locking servo loop.

Pulse modulation signal generation circuit, and semiconductor laser modulation device, optical scanning device and image formation device using the same

Abstract: A clock generating part generates a high-frequency clock signal having a frequency higher than that of a pixel clock frequency; a serial modulation signal generating part generates a serial modulation signal having a serial pulse sequence based on the high-frequency clock signal, and, light emission is modulated according to the serial modulation signal, and, thus, each pixel of an image is formed according at the pixel clock frequency.

Oscillator with a noise reduction function, a writer, and a method of controlling a writer

Abstract: An oscillator 10 with a noise reduction function has a memory 80 that memorizes modulation data DM for performing the spread spectrum modulation input from an output terminal fout, a modulation signal output circuit 60 that generates a modulation signal SM from the modulation data DM memorized in the memory 80, and a mixer 53 that overlays the modulation signal SM on the control voltage VC of a voltage control oscillator (VCO) 54 of a PLL circuit 50, and it becomes possible to output a spread spectrum modulated output signal CLv under a specification desired by a user by memorizing in the memory 80 the modulation data DM that corresponds to the spread spectrum modulation the user tries to set.

Pulse width modulation drive signal for a mems gyroscope

Abstract: A MEMS gyroscope may be coupled to drive electronics that provide a pulse width modulation drive signal to the MEMS gyroscope The pulse width modulation drive signal may be generated by comparing a pickoff signal and/or input signal to a direct current threshold level

Phase locked looped based digital pulse converter

Abstract: A pulsed width generator provides a plurality of pulse width modulated signals based upon a reference frequency generated by a phase locked loop. A comparator watches for certain number of pulses of the reference frequency to generate an output signal which is compiled to a pulse width modulation circuit which provides a pulse width modulated signal. A sequencer may be used to control the start and stop times of each phase independently.

Digital power amplifier and digital/analog converter

Abstract: A digital power amplifier includes a pulse width modulator for converting an input signal into a pulse width modulated signal according to a signal level of the input signal; an output stage, switching thereof being controlled by the pulse width modulated signal generated by the pulse width modulator; a pulse width modulation ratio detector for detecting a pulse width modulation ratio of the pulse width modulated signal generated by the pulse width modulator; and a control unit for disabling the switching operation of the output stage. The control unit disables the switching operation of the output stage when the pulse width modulation ratio detector detects that the pulse width modulation ratio is 50%.

Nonlinear dynamics of a laser diode with optical feedback systems subject to modulation

Abstract: The nonlinear dynamic behavior of a direct frequency-modulated diode laser with strong optical feedback is examined and compared to a laser diode subject to electro-optically modulated, strong optical feedback Direct modulation is achieved by sinusoidal modulation of the diode laser injection current Electro-optic modulation is achieved by applying a sinusoidal voltage to an intracavity phase modulating element The output state (characterized by the output power versus time, the intensity noise spectrum and the optical frequency spectrum) for both types of modulation is dependent on the ratio of the modulation frequency to the external cavity resonant frequency, and the modulation power A number of distinct states are observed: conventional amplitude modulation (with FM spectra); multimode, low-noise amplitude modulation; multimode, high-noise amplitude modulation; periodic limit-cycle operation; quasi-periodicity; chaos; low-frequency fluctuations; and mode-locking There are significant differences between the direct and electro-optic frequency-modulation cases The onset of the dynamic instability is characterized as a noisy period-one oscillation for direct modulation and a low-frequency fluctuation for intracavity electro-optic modulation Phase portraits produced experimentally with the use of a digital phosphor oscilloscope are shown to agree well with those constructed from output power versus time data This represents an experimental method for examining the dynamics phase portraits in real-time

A vision sensor with on-pixel ADC and in-built light adaptation mechanism

Abstract: In this paper we propose an on-pixel Analogue-to-Digital Converter (ADC) based on pulse frequency modulation (PFM) scheme. This PFM based converter presents a viable solution for pixel-level based ADC. It uses a simple and robust circuit that can be implemented in a compact area resulting in a 23% fill-factor for a digital vision sensor in 0.25 μm CMOS technology. An in-built light adaptation mechanism has also been implemented which allows the sensor to better adapt to low-light intensity or to adjust the sensor saturation level. As a consequence, the proposed sensor features a programmable dynamic range. Image lag is eliminated since a reset of the photodetector is performed after the conversion period. A prototype comprising a 32 X 32 pixel array has been implemented in CMOS 0.25 μm technology. Each pixel occupies an area of 45 X 45 μm 2 with an average power consumption of 85 μW per pixel.

Random pulse width modulation method and device

Abstract: A system and method (705) for executing random pulse width modulation in electronic power converters. In accordance with the invention, the sampling period of sampling cycles for pulse width modulation remains constant while the period of switching cycles are varied. The periods of switching cycles (702) are varied using random numbers to calculate delays between the start of coincident sampling and switching cycles.

Compensating method for a pll circuit that functions according to the two-point principle, and pll circuit provided with a compensating device

Abstract: A PLL circuit is tuned to a first frequency by using a first digital modulation signal and subsequently tuned to a second frequency by using a second digital modulation signal. A differential signal, that is a function of the change in voltage of a VCO control signal generated by the modulation signals, is compared with a comparison signal, that is characteristic of the analog modulation amplitude. Based on the comparison the analog modulation amplitude is changed to minimize or substantially eliminate a deviation between the signals.

Light-emission modulation having effective scheme of creating gray scale on image

Abstract: A clock generating part generates a high-frequency clock signal having a frequency higher than that of a pixel clock frequency; a serial modulation signal generating part generates a serial modulation signal having a serial pulse sequence based on the high-frequency clock signal, and, light emission is modulated according to the serial modulation signal, and, thus, each pixel of an image is formed according at the pixel clock frequency.

Pulse-width modulation circuit and power amplifier circuit

Abstract: A pulse-width modulation circuit comprises a comparator having hysteresis characteristics of positive feedback, and an integrator, whose integrated output is compared with an input signal to produce a pulse-width modulation (PWM) signal having an advanced phase characteristic due to differentiation of the input signal. A switching circuit amplifies the pulse-width modulation signal based on the positive and negative source voltages (V PX , V MX ). The amplified pulse-width modulation signal is supplied to a speaker via an LC filter, and it is also negatively fed back to the pulse-width modulation circuit. Since the pulse-width modulation signal whose phase is advanced is transmitted through the LC filter, it is possible to reduce phase revolution in the output of the power amplifier circuit. Thus, it is possible to effect negative feedback on the pulse-width modulation signal in a stable manner.

An integrated digital PFM DC-DC boost converter for a power management application: a RGB backlight LED system driver

Abstract: In this paper is presented a system that has been designed in the frame of a co-operation between the ON Semiconductor Microelectronics Company, at its Toulouse (France) Design Centre and the Electronics Department of the University of Barcelona (SIC Group). The system that has been designed is a high efficiency boost converter to supply and drive multicolour LEDs (light emitting diodes). The paper presents the switching power DC/DC boost converter performances, based on a current peak PFM (pulse frequency modulation) system, with the objective to design this system for in low-voltage portable applications. The DC/DC converter is able to source an output current up to 300 mA, and it presents good performances for very low load conditions (100 /spl mu/A), for an input battery of 3.6 V (nominal value). It needs an external inductor of 10 /spl mu/H. From an external micro-controller the output voltage value can be programmed to either two values of 4 V or 5 V. LED's brightness is controlled by a digital pulse width modulation (PWM) procedure.

Mechanisms of modulation gap detection

Abstract: It has been postulated that the central auditory system contains an array of modulation filters, each responsive to a different range of modulation frequencies present at the outputs of the (peripheral) auditory filters. In the present experiments, we tested what we call the "dip hypothesis," that a gap in modulation is detected using the "dip" in the output of the modulation filter tuned to the modulator frequency. In experiment 1, the task was to detect a gap in the sinusoidal amplitude modulation imposed on a 4-kHz carrier. The modulator preceding the gap ended with a positive-going zero-crossing. There were three conditions, differing in the phase at which the modulator started at the end of the gap; zero-phase, at a positive-going zero-crossing; pi-phase, at a negative-going zero-crossing; and "preserved" phase, at the phase the modulator would have had if it had continued without interruption. Modulation frequencies were 5, 10, 20, and 40 Hz. Psychometric functions for detection of the gap were measured using a two-alternative forced-choice task. For the zero-phase and preserved-phase conditions, the detectability index, d', increased monotonically with increasing gap duration. For the pi-phase condition, performance was good (d' > 1) for small gap durations, and initially worsened with increasing gap duration, before improving again for longer gap durations. This is the pattern of results expected from the dip hypothesis, provided that the modulation filters have Q values of 2 or more. However, it is also possible that a rhythm cue was used to improve performance in the pi-phase condition for short gap durations; the introduction of the gap markedly disrupted the regular rhythm produced by the modulator peaks. In experiment 2, the rhythm cue was disrupted by varying the modulator period randomly around its nominal value, except for the modulator periods immediately before and after the gap. This markedly impaired performance, and resulted in psychometric functions that were very similar for the zero-phase and pi-phase conditions. This pattern of results is inconsistent with the dip hypothesis. For both experiments, modulation gap "thresholds" (d' approximately 1) were roughly constant when expressed as a proportion of the modulator period. Possible mechanisms of modulation gap detection are discussed and evaluated.

Method and apparatus for image forming capable of effectively controlling a light beam with a pulse width modulation

Abstract: An image forming apparatus includes a modulation data storage, a pulse width modulator, and an optical writing mechanism. The modulation data storage stores different gray-scale pulse sets. Each set includes gray-scale pulses having pulse widths different from each other in steps of a predetermined value corresponding to gray-scale information possibly contained in image data to be input. Each gray-scale pulse includes at least two pulses including at least one of left-positioned and right-positioned pulses. The pulse width modulator selects a gray-scale pulse set from among the different gray-scale sets in accordance with gray-scale information and performs a pulse width modulation to control a light beam on and off at a density twice or more than twice a density of the input image data by using the gray-scale pulse set selected. The optical writing mechanism causes the light beam to scan a photosensitive member to form a latent image thereon.

Power linearization technique for controlling the luminance of light emitting display devices

Abstract: A circuit and method for providing a linear power to a load uses pulse modulation technique where the frequency and pulse width of the pulse width modulated waveform driving the load are varied simultaneously. In one aspect of the disclosure, a pulse width modulator circuit is responsive to a command drive signal for producing the pulse width waveform the width of the pulses varying accordingly. In addition, a frequency control circuit that is also responsive to the command drive signal provides a control current to the pulse width modulator circuit wherein the frequency of the waveform is varied as the pulse widths are varied.

Duty cycle correction circuit for use with frequency synthesizer

Abstract: A duty cycle correction circuit is provided for converting a pair of differential analog signals from an oscillator into an output pulse signal with 50% of duty cycle. The pulse signal has the same frequency as that of each of the differential analog signals. The duty cycle correction circuit includes a first differential-to-single-ended buffer circuit, a second differential-to-single-ended buffer circuit, a first frequency divider, a second frequency divider and a symmetrical exclusive OR element. The first and the second differential-to-single-ended buffer circuits are used for processing the pair of differential analog signals into a first and a second digital pulse signals, respectively. The first and the second frequency dividers are employed for frequency-dividing the first and the digital pulse signal into a third and a fourth digital pulse signal, respectively. The symmetrical exclusive OR element is used for performing an exclusive OR operation so as to produce the output pulse signal.