Showing papers on "Pulse-frequency modulation published in 1997"

Modeling auditory processing of amplitude modulation I. Detection and masking with narrow-band carriers

Abstract: This paper presents a quantitative model for describing data from modulation-detection and modulation-masking experiments, which extends the model of the ‘‘effective’’ signal processing of the auditory system described in Dau et al. @J. Acoust. Soc. Am. 99, 3615‐3622 ~1996!#. The new element in the present model is a modulation filterbank, which exhibits two domains with different scaling. In the range 0‐10 Hz, the modulation filters have a constant bandwidth of 5 Hz. Between 10 Hz and 1000 Hz a logarithmic scaling with a constant Q value of 2 was assumed. To preclude spectral effects in temporal processing, measurements and corresponding simulations were performed with stochastic narrow-band noise carriers at a high center frequency ~5 kHz!. For conditions in which the modulation rate ( f mod) was smaller than half the bandwidth of the carrier (D f ), the model accounts for the low-pass characteristic in the threshold functions @e.g., Viemeister, J. Acoust. Soc. Am. 66, 1364‐1380 ~1979!#. In conditions with f mod.D f /2, the model can account for the high-pass characteristic in the threshold function. In a further experiment, a classical masking paradigm for investigating frequency selectivity was adopted and translated to the modulation-frequency domain. Masked thresholds for sinusoidal test modulation in the presence of a competing modulation masker were measured and simulated as a function of the test modulation rate. In all cases, the model describes the experimental data to within a few dB. It is proposed that the typical low-pass characteristic of the temporal modulation transfer function observed with wide-band noise carriers is not due to ‘‘sluggishness’’ in the auditory system, but can instead be understood in terms of the interaction between modulation filters and the inherent fluctuations in the carrier. © 1997 Acoustical Society of America.@S0001-4966~97!05611-7#

Digital compensation for wideband modulation of a phase locked loop frequency synthesizer

Abstract: A digital compensation filtering technique is provided that enables indirect phase locked loop modulation with a digital modulation data stream having a bandwidth that exceeds, perhaps by an order of magnitude, the bandwidth characteristic of the phase locked loop. A modulation data receiver is provided for receiving from a modulation source digital input modulation data having a bandwidth that exceeds the cutoff frequency characteristic of the phase locked loop frequency response. A digital processor is coupled to the modulation data receiver for digitally processing the input modulation data to amplify modulation data at frequencies higher than the phase locked loop cutoff frequency. This digital processor is connected to the phase locked loop frequency divider to modulate the divider based on the digitally-processed input modulation data, whereby a voltage controlled oscillator of the phase locked loop is controlled to produce a modulated output carrier signal having a modulation bandwidth that exceeds the phase locked loop cutoff frequency. The digital processing of the modulation data can be implemented by adapting a digital FIR Gaussian transmit filter such that its filter characteristic reflects the intended modulation data amplification as well as enables Gaussian Frequency Shift Keyed modulation. With this implementation, no additional componentry beyond the PLL system is needed to implement the digital modulation data processing provided by the invention.

The relationship between space-vector modulation and regular-sampled PWM

Abstract: The relationship between regular-sampled pulse-width modulation (PWM) and space-vector modulation for inverter drives is defined, and it is shown that, under certain circumstances, the two approaches are equivalent. The various possibilities of adding a zero-sequence component to the regular-sampled sinusoidal modulating wave are explored, and these effects are quantified. It is shown that this leads to "equal-null" pulse times, which extend the linear modulation range and simplify the microprocessor implementation.

A high performance generalized discontinuous PWM algorithm

Abstract: In this paper a generalized discontinuous pulse width modulation (GDPWM) method with superior high modulation operating range performance characteristics is developed. An algorithm which employs the conventional space vector PWM method in the low modulation range, and the GDPWM method in the high modulation range is established. As a result, the current waveform quality, switching losses, voltage linearity range and the overmodulation region voltage gain of a PWM-VSI drive are optimized online as opposed to conventional modulators with fixed characteristics. Due to its compactness, simplicity and superior performance, the algorithm is suitable for most high performance PWM-VSI drive applications. The paper provides a detailed performance analysis of the method and compares it to the other methods. Experimental results verify the superiority or this algorithm to conventional PWM methods.

Real-time heart rate variability extraction using the Kaiser window

Abstract: A new method for real-time heart rate variability (HRV) detection from the R-wave signal, based on the integral pulse frequency modulation (IPFM) model and its similarity to pulse position modulation, is presented. The proposed method exerts lowpass filtering with a Kaiser window. It can also be used for off-line HRV analysis in both the time and frequency domains. Real-time bandpass filtering as a new HRV investigation method and as a by-product of the proposed algorithm is also introduced. Furthermore, the discrete time domain version of the French-Holden algorithm is developed, and it is thoroughly proved that lowpass filtering is an ideal method for detection of HRV.

Method for wireless information transfer

Abstract: A method of wireless information transfer, especially for mobile communication, whereby an input signal (sl, g4) is subjected to a modulation in a transmitter (2-8) and reaches a receiver (11-15) via a transmission channel. The transmitter produces angularly modified pulses having a frequency spectrum and carrying information, in such a way that said pulses can be time compressed in the transmitter by means of a filter (13) with a frequency dependent differential transit time, also called a group transit time, so that pulses with reduced duration and higher amplitude can arise, and at least one part of the information in the transmitter is impressed on the pulses by means of a modulation independent from the angle modulation and/or used to control an angle modulation parameter which can be detected in the receiver.

Transmission system with cross-phase modulation compensation

Abstract: In a WDM transmission system carrying amplitude modulated traffic in which significant cross-phase modulation occurs, each of the individual channels is pre-chirped at the transmitter with replicas, or low-pass filtered replicas of the amplitude modulation applied to each of the other channels. Prechirping of each individual channel with a replica of the amplitude modulation applied to that channel may be added in order additionally to provide compensation for self-phase modulation.

Feed forward amplifiers and methods

Abstract: Feed forward amplifiers and methods particularly suited for power multichannel microwave amplifiers for cellular phone base stations and the like. The input signal is modulated with a small percentage of modulation at a relatively low frequency before being amplified by the main amplifier. At the same time, the input signal is also coupled to provide inphase and quadrature components thereof to be mixed with the amplifier output and lowpass filtered to extract a component of the low frequency responsive to modulation components in the amplifier output due to the low frequency modulation. This signal is then multiplied by the low frequency to provide a DC voltage controlling an adaptive control circuit to adjust the inphase and quadrature components of the intermodulation components and the low frequency modulation of the entire signal so that the result can be combined with the main amplified signal to remove the intermodulation components and the low frequency modulation of the entire signal from the amplifier output.

Spectral distortion properties of the integral pulse frequency modulation model

Abstract: The integral pulse frequency modulation (IPFM) model has been used for the following two purposes. First, it has been utilized to verify the correspondence between the spectral structure of autonomic input and the estimated spectrum of heart rate variability (HRV), relying mainly on the theoretical work of Bayly (1968). Second, the IPFM model provides a framework for evaluating how precisely the proposed method of HRV analysis could estimate the input spectral structure. However, the appropriateness of the IPFM model for both purposes has not been examined sufficiently in realistic situations. Here, the spectral structure of the pulse train generated by the IPFM model is theoretically derived for an input signal containing multiple frequency components. This is a more general condition than the single sinusoidal input signal used earlier. In accordance with the theoretical results, the magnitude of the spectral distortion is computed for a pair of varied frequencies, considering the corresponding coefficient of variation of interpulse intervals. Results show that the distortion could be nonnegligible under practical values of the coefficient of variation. Such distortion may well affect the spectral structure in the wide frequency range. This study suggests that the spectral structure of HRV should be interpreted carefully, taking the above distortion properties into account, even though the IPFM model appears to be established as a mechanism mediating between autonomic input and heart rate variability.

A comparison of detection and discrimination of temporal asymmetry in amplitude modulation

Abstract: Two compound experiments were performed to compare the detection of amplitude modulation with the discrimination of modulator shape when the modulators have strong temporal asymmetry. In experiment 1, an adaptive procedure was used to measure detection and discrimination as a function of modulation frequency from 4 to 400 Hz. In experiment 2, the method of constant stimuli was used to measure psychometric functions for detection and discrimination at one modulation frequency, 8 Hz. The asymmetric modulators were time-reversed pairs. Thus their envelope spectra are identical and models based on the envelope spectrum would predict no effect of asymmetry on detection or discrimination at any modulation depth. The detection results show, as predicted, that the direction of asymmetry does not affect the detectability of modulation in either experiment. In contrast, the discrimination results show that direction of asymmetry is readily discriminable for modulation frequencies less than about 50 Hz, indicating that envelope-spectrum models will require modification if they are to be extended to include discrimination of temporal asymmetry.

Apparatus and method for output signal pulse width error correction in a communications receiver

Abstract: An output signal pulse width error correction circuit and method wherein errors in a data signal conforming to a communications protocol having a prescribed duty cycle are corrected by monitoring a duty cycle of the data signal, comparing the duty cycle to a duty cycle reference voltage corresponding to the prescribed duty cycle, and adjusting a pulse width of the data signal to conform to the prescribed duty cycle of the protocol. An embodiment is shown that low pass filters the input data signal to introduce greater slope to the input data signal which is then compared to a pulse width control voltage in order to generate an output data signal. The pulse width control voltage is produced by integrating the output data signal to obtain an average value corresponding to the duty cycle of the output data signal and comparing the average value to a duty cycle reference voltage corresponding to the prescribed duty cycle for the communications protocol. Another embodiment directed toward an integrated circuit implementation is shown that converts the input data signal into complementary input data current signals, using current mirror circuits, which are used to drive complementary variable delay circuits. The pulse width control voltage is also converted into complementary error current signals which adjust the duty cycle of output data signal by controlling the variable delay circuits.

Variable-frequency complex demodulation technique for extracting amplitude and phase information

Abstract: We present a variable-frequency variant of the complex demodulation technique. Complex demodulation is the digital equivalent of heterodyne detection, in which the input signal is multiplied by a carrier oscillation {exp(−iωmt)} of modulation frequency ωm and then low-pass filtered. The time-dependent amplitude and relative phase can then be computed from the filtered demodulate. This technique fails when the frequency of oscillation differs from the modulation frequency by more than the cutoff frequency of the low-pass filter. We modified the standard technique by computing iteratively a time-dependent modulation frequency {ωm(t)} that tracks the signal frequency to within ±0.1% of the Nyquist frequency. This small difference frequency allows the use of very narrow filter bandwidths for the study of narrow-band oscillations with improved signal-to-noise ratio. We apply this analysis tool to Mirnov oscillations measured by a magnetic probe and show the time variation of the amplitude of the fundamental an...

Demodulator for a pulse width modulated signal and method

Abstract: A demodulator for a pulse width modulated signal comprises a counter arranged to count in one direction when the PWM signal is "high" and in the opposite direction when the PWM signal is "low" to arrive at a count representative of a duty cycle. As a result, a value representative of the duty ratio of the PWM signal can be obtained from the up/down counter. In a further embodiment, the up/down counter is clocked by the output of a frequency multiplier, the output of the frequency multiplier having a frequency determined by the pulse width modulated signal frequency multiplied by a predetermined factor. The value of the duty ratio of the PWM signal can then be found regardless of the frequency of the PWM signal.

Simulation of Switching Properties of Ferroelectrics on the Basis of Dipole Lattice Model

Abstract: A discrete lattice model developed by Ishibashi is used to explain the field, temperature and grain size dependence of the switching responses of ferroelectrics. Partial switching processes have been simulated using both pulse frequency modulation (PFM) and pulse width modulation (PWM). A new interpretation of the differences between the switching and non-switching responses of the ferroelectric has been obtained on the basis of analyzing the temporal dependence of dipoles' orientation, as described by the proposed model.

Phase-change type optical recording and reproducing method

Abstract: When recording data according to the PWM recording system by modulating signals, pulse modulation for pulse modulation for recording for recording a 0 signal or the like having a signal width of nT (T: Clock time) after modulation is a continuous electro-magnetic wave at a power level e, a record signal pulse array for recording a 1 signal or the like having a signal width of nT after modulation comprises a pulse section fp having a time width x and a power level a, a multi-pulse section mp in which a low level pulse at a power level b and a high power pulse at a power level c having a time width T in total alternately appear (n-n') times in all with a duty ratio y, and a pulse section op having a time width z and a power level d, and x, y, z are integers satisfying the conditions of 0.5T ≦x≦2T, 0.4≦y≦0.6 and 0.5T≦z≦1T, and n' is a positive integer which is equal to or smaller than n, and controls are provided so that the condition of (a and c)>e>(b and d) is satisfied.

Pulse width extension with analog command

Abstract: A method of modulating the pulse width of a pulse width signal in response to an analog signal. The steps include changing the analog signal to a digital signal, changing the digital signal to a number of counts, changing the number of counts to a time delay, and then using the logic circuit to combine the time delay with a pulse with modulated input to change the pulse width of an output signal.

Pulse width modulation control system for electric power converter

Abstract: In a pulse width modulation control method and system for an electric power converter, in order to suppress the occurrence of lower order harmonics and fractional order harmonics in a direct current component even in a condition where a carrier frequency is several times as small as the frequency of a command value, pulse width modulation pulses for driving semiconductor elements in the electric converter are calculated by comparing a command signal from a command value generating means with a carrier signal having a continuous triangular-wave and a constant period. For this purpose, there is provided a means for separately calculating a time product of a command value of the command signal from the command value generating means and a time product of the pulse width modulation pulses and for calculating a difference value representing a difference between both time products. The pulse width modulation pulse is then calculated using the calculated difference value to compensate the command signal received from the command value generating means.

Receiver for pulse width modulated transmissions

Abstract: In a receiver, a system and method are disclosed for providing improved detection of data from a transmitted sequence of pulse width modulated (PWM) pulses. The disclosed system includes a pulse detector having an adjustable critical duty cycle for distinguishing between first and second pulses based upon their respective long and short duty cycles at which they are received. The disclosed system further includes an element which determines the duty cycle of the received pulses and an element which adjusts the critical duty cycle based on the duty cycle which is so determined. The duty cycle may be determined by determining the correspondence between information obtained from an initial pulse sequence and reference information at the receiver. In the disclosed method, the duty cycle of pulses in an initial sequence is first determined and then checked against a predetermined limit. If the duty cycle falls outside the limit, the critical duty cycle is adjusted prior to further pulses being detected.

Inverter control method and its equipment

Abstract: PROBLEM TO BE SOLVED: To make it possible to control a motor in wide ranges of speed and load and to improve a torque and speed control capacity, by shortening the duration of other pulse width modulation signal contained in the same subordinate cycle by a certain value, and by compensating the increment defining a measuring interval by the sum of the shortening. SOLUTION: In a pulse width modulation period, if a time interval between the switching of switching means 8, 10 and 12 of one phase and the switching of switching means 9, 11 and 13 corresponding to the subsequent phase becomes smaller than the predetermined threshold value, then the measurement is stopped, a pulse width modulation signal defining a measuring time interval of a sufficient duration is generated and the effect of switching for a line current is made measurable. And, the duration of other pulse width modulation signal contained in the same subordinate cycle is shortened by a certain value, and an increment in the pulse width modulation signal defining the measuring interval is compensated by the sum of the shortening of other pulse width modulation signals. COPYRIGHT: (C)1998,JPO

Analog to pulse width converter for field emission displays

Abstract: A field emission display ("FED") is disclosed having a gray scale range. Input into the FED, initially, is an analog signal input. The FED, by employing an analog to pulse width converter, subsequently converts the analog input to a pulse width output, the width of which directly correlates to the amplitude of the analog input signal. To achieve this design, the analog to pulse width converter comprises a sampler for sampling the analog signal at a predetermined frequency, thereby creating a plurality of samples corresponding to the input voltage. Further, the converter comprises means for holding each of the samples. The output of the holding means is subsequently coupled with a load responsive to the output of the holding means. In one embodiment of the present invention, this load comprises a voltage controlled resistance. The voltage controlled resistance can comprise a convertor for converting each of the samples to a current source and a load for creating a voltage ramp. The voltage ramp is subsequently input to a buffer for comparing the load output with a predetermined threshold. By this design, a pulse width signal is thereby created, the width of which ranges between a minimum and a maximum value, the minimum and the maximum values corresponding to the gray scale range.

Method and apparatus for adjusting modulation accuracy of an orthogonal modulation

Abstract: A method of adjusting modulation accuracy corrects an I modulation signal and a Q modulation signal without using special hardware when an accurate 90° phase difference between the I modulation signal and the Q modulation signal is not present. The method comprises setting I component correction Δi for a plurality of phase differences in advance to an I component corrector in accordance with an I signal, which is converted from digital modulation data in a digital data train by a modulator and an IQ converter of a phase error corrector. The method also comprises setting a Q component correction Δq for a plurality of phase differences in advance to a Q component corrector in accordance with a Q signal, controlling the I component corrector and the Q component corrector by a phase error correction controller, thereby adding the I component correction Δi and the Q component correction Δq to the I signal and the Q signal so as to generate a corrected I signal and a corrected Q signal. Thus the phase difference between an I modulation signal and a Q modulation signal is accurately adjusted to 90°.

Band Limited AM modulator using linear power amplification

Abstract: A band limited Amplitude Shift Keyed (ASK) modulator employing linear modulation and an efficient Class C power amplifier. Band-limited operation is provided by filtering a digital baseband input signal prior to modulation. Closed loop feedback is employed around the amplifier to assure linear modulation over a wide modulation range which preserves the frequency characteristics of the baseband signal on the modulation envelope. Further filtering is accomplished by exploiting the closed loop system response, incorporating it in the filter characteristic as an added filter pole.

Digital to analog converter using pulse width modulation and the controlling method thereof

Abstract: A digital to analog converter using pulse width modulation is disclosed. The digital to analog converter according to the invention comprises a PWM pulse generator and an integrator. First, the PWM pulse generator includes a first data buffer 100 and a second data buffer 200. First data buffer 100 is provided with an input terminal for receiving digital signals having control value D in produced by the system controller, for example, in response to a key input. Second data buffer 200 is provided for storing the previous control value D in-1 . The new input data stored in first data buffer 100 and second data buffer 200 are compared one another in a controller 600. The controller 600 is provided for receiving the output signal of comparator 500 and for supplying control signals with a pulse generator 300 and a time constant selector 400 based on the comparator output signal. The time constant selector 400 may include a number of resistors which can be selected through an electronic switch in response to the control signal fed from the controller 600. The pulse generator produces a pulse signal in which duty ratio of the pulse signal can be varied by the control signal; also the time constant selector selects a resistance value of the time constant of the integrator which converges the input pulse signal from the pulse generator on a DC voltage value proportional to the duty ratio of the pulse signal. According to this invention, the speeding up of the response time of the analog output signal can be possible by reducing the transient period and also the magnitude of ripple can be reduced which result in enhancing the quality of the output signal.

Circuit and method for modulating pulse width

Abstract: Signal C=[C n−1 , C n−2 , . . . , C 1 , C 0 ] generated by a ring counter 1 is converted at a logic circuit 2 to a triangle pulse signal Q in which the carrier frequency of the PWM signal is equal to the frequency of the signal C raised to power of 2. The signal Q is input to the B input of a magnitude comparator 3 . On the other hand, the modulation data D held by a data holding circuit 4 is compared with the converted signal Q in the magnitude comparator 3 , and when the data D is greater than the signal Q, a PWM signal is obtained from the comparison result A>B. This PWM signal has no phase change and high resolution and is a low pulsating component. The resolution of the PWM signal per cycle of the ring counter 1 is held at n bits, and the carrier frequency is equal to the ring counter frequency raised to mth power of 2.

Unified PWM technique for real time power conversion

Abstract: In this paper, a new voltage modulation technique named 'unified PWM (pulse width modulation)' is described for high performance voltage generation in a 3-phase voltage-fed inverter. By considering the operation of the inverter, a simple but useful concept named 'effective time' could be established, and, fully employing this concept, a new voltage modulation technique is presented with detailed explanation and actual test results. The results show that (1) the implementation burden of PWM is conspicuously reduced, (2) change from one modulation scheme to another is also obtained easily and seamlessly, and (3) widely used overmodulation schemes are easily implemented.

Optical frequency control system

Abstract: A control system for controlling the frequency of a laser 1 in an optical transmission system comprises means 34 for applying a frequency modulation to the laser, means 35 for determining an amplitude modulation present in the signal downstream of the laser and attributable to the frequency modulation, and means 36 for discriminating a portion of the amplitude modulation which is substantially in phase quadrature with the applied frequency modulation, and means 37 for controlling the frequency of the laser on the basis of the discriminated quadrature portion. An optical component downstream of the laser may have a response which converts FM to AM. The response and the frequency output of the laser can be locked to one another, without errors caused by unwanted AM in the transmitted signal modulation frequency.

Method of operating a continuous wave sonar system

Abstract: An improved method is provided for operating a continuous wave sonar syst At time of transmission, a plurality of acoustic pulses are transmitted one right after another. Each pulse has a unique frequency and is of a time duration that is approximately one second long. The pulses are characterized by a separation frequency representing a difference in frequency between numerically successive frequencies. However, the pulses are staggered with respect to frequency. In the preferred embodiment, each successively transmitted one of the pulses is separated in frequency from an immediately preceding transmitted one of the pulses by an amount greater than the separation frequency. These multiple pulses seperated in time and in frequency, reduce the effects of frequency speading caused by the medium, resulting in a sonar with enhanced detection performance.

Modulation Characteristics of the Negative Nonlinear Absorption Effect in Erbium-Yttrium Aluminum Garnet

Abstract: Dependence of the negative nonlinear absorption effect on both modulation degree and frequency was investigated in erbium yttrium aluminum garnet crystals. For a modulation frequency of 1 MHz, two peaks, A and B, were observed in the transmitted waveform. With a decreasing modulation degree, peak C which consists of peaks A and B appeared and a reversed-phase waveform was obtained in the transmitted waveform. Peak A decreased as the modulation frequency increased, and peak B was only observed for modulation frequencies above 50 MHz. In the case of a modulation degree under 35%, the transmitted waveform changed to the opposite phase of incident one for modulation frequencies up to 100 MHz. In addition, the negative nonlinear absorption effect was dependent on the product of the composition of erbium and the sample length. It was suggested that the enhanced absorption was due to stimulated emission in three excited states of Er3+.

Transmitting a signal using duty cycle modulation

Abstract: A transmitter is provided for transmitting an analog signal. The transmitter has an input receiving the analog signal within a range of values. The transmitter also includes a duty cycle modulator generating a modulated two state signal having a maximum frequency at an intermediate value of the range. The duty cycle of the modulated signal is monotonically related to the analog signal while the frequency of the signal decreases with increase and decrease of the value of the analog signal from the intermediate value. The transmitter further includes an output for transmitting the modulated signal on a communication channel. A receiver is also provided that includes an input receiving the modulated two state signal from the transmitter, and a circuit for translating the received signals to an output analog signal.

A high performance space vector motor drive controller

Abstract: Pulse width modulation (PWM) techniques are normally used to generate the required voltage or current waveforms to drive an AC motor. Space vector theory can be used to improve both the output crest voltage and the harmonic copper loss. The maximum output voltage based on the space theory is 1.155 times as large as the conventional sinusoidal modulation. It enables the inverter to feed the motor with a higher voltage than the easier suboscillation modulation method. Moreover, this method generates waveform in real-time and high precision when implemented in high performance processors. The new digital signal processor ADMC 330 from Analog Devices has been used for this purpose. Using this processor, an improved modulation technique for PWM voltage source inverter drives has been implemented. This technique also reduces the acoustic noise emitted in some specific working points by the AC machine due to the switching frequency. The acoustic noise is further reduced by using a random modulation strategy without actually raising the carrier frequency. This paper presents some first experimental results on the development of a DSP-based high performance space vector induction motor drive using the newly released XDMC330 DSP chip from Analog Devices. Specifically the implementation of the real-time generation of a three-phase PWM waveform using the space vector modulated scheme and the random modulation method are discussed. (4 pages)