Showing papers on "Pulse-frequency modulation published in 1983"

Digital frequency modulation system and method

Abstract: There is disclosed a new and improved frequency modulation system and method for providing a frequency modulated signal which varies in frequency from a center frequency in response to the amplitude of an analog modulating signal. The system and method utilizes a frequency shift synthesizer to provide the frequency modulated signal and digital techniques for quantizing the amplitude modulating signal and providing dividing factors to the frequency shift synthesizer responsive to the amplitude quantization.

Modulation Methods Related to Sine-Wave Crossings

Abstract: A bounded band-limited signal may be represented by its sine-wave crossings, i.e., by a set of points on the time axis at which it crosses a reference sinusoid. If, at these points, pulses of a standard shape are generated, we obtain a position modulated pulse train. This pulse train is analyzed in detail. Two other modulation methods related to sine-wave crossings are also discussed, namely, edge position modulation of a square wave and bipolar pulse duration modulation. In all cases, the modulated waves may be expressed as sums of an infinite number of sinusuidal carriers amplitude modulated by Chebyshev polynomials of modulating signals.

Modulation detuning characteristics of actively mode-locked diode lasers

Abstract: Existing frequency domain models for the active mode locking of diode lasers are appropriate for antireflection- (AR-) coated devices This paper presents the first frequency domain model for non-AR-coated devices The use of uncoated devices permits the independent measurement of all of the important laser parameters required for the model, so that no adjustable parameters are needed An additional novel feature of this model is that the effect of gain saturation on the exact shape of the gain waveform is allowed for in a completely self-consistent fashion Experimental studies were carried out on uncoated undegraded commerical laser diodes Threshold reductions of 25-30 percent were achieved for external cavity operation The mode-locking studies reported in this paper were carried out above the external threshold current, with a sinusoidal modulation near 1 GHz at a modulation index of 4 percent The results of these studies showed good agreement with the predictions of the model presented here, in contrast with the predictions of the existing models Specifically, the modulation frequency corresponding to the shortest most intense mode-locked pulses was found to occur at a fraction of 1 percent below the frequency matched to the external cavity roundtrip time As well, the predicted effects of gain saturation were observed in the detailed structure of the mode-locked pulses, and in their detuning characteristics

Light frequency change detecting method and apparatus

Abstract: LIGHT FREQUENCY CHANGE DETECTING METHOD AND APPARATUS Abstract of the Disclosure: A method and apparatus for detecting a frequency change of a light of the invention modulates the scattered light from the object of measurement using an acousto-optic modulator or the like, heterodyne-detects the scattered light after modulation to provide an electrical signal having a frequency (fd - fm) which is the difference between the Doppler frequency fd and the modulation fre-quency fm, passes this electrical signal to a filter while changing the modulation frequency fm, and obtains the modulation frequency fm at which the signal voltage is the largest or the smallest, that is, the Doppler frequency fd.

Enhanced frequency modulation in cleaved‐coupled‐cavity semiconductor lasers with reduced spurious intensity modulation

Abstract: We have observed enhanced analog frequency modulation in a cleaved‐coupled‐cavity (C3) laser. One diode is dc biased above threshold to produce the desired output power and the other diode, the modulator, is biased below threshold with a dc current and a small modulating current superimposed to achieve analog frequency modulation of the output beam. Comparing with direct analog frequency modulation of a conventional semiconductor laser, the C3 laser has allowed us to obtain significantly larger frequency deviation with negligible spurious intensity modulation. Further, the present frequency modulation response is also much more uniform with respect to modulation frequency. In addition, this scheme is applicable to C3 lasers formed from all laser structures.

Pulse-width modulation circuit with carrier signal frequency control

Abstract: A pulse-width modulation circuit detects a signal level or amplitude of an audio signal by means of an absolute value detecting circuit. The detected level is applied to a control terminal of a voltage-controlled oscillator. The output of the voltage-controlled oscillator is used as a carrier signal of the pulse-width modulation circuit, and the frequency thereof is controlled in such a manner that the carrier frequency is lowered as the audio signal level increases. Higher order harmonics of the pulse-width-modulated output signal both at high and low modulation factors are made substantially the same in amount. Thus, a band width required for the circuit is remarkedly narrowed, and improvement in distortion factor can be attained regardless of a low cost to manufacture.

Effect of Amplitude Modulation on Selective Excitation in NMR Imaging

Abstract: If NMR imaging uses selective excitation, then it has to do it correctly as it affects the image resolution. We have related the properties of the selected slice, such as its width, its rate of attenuation, and its side lobes to the amplitude modulation of the radio frequency pulse. An interesting observation was that multiplying sinc(t) function by a triangle can give better results than multiplying it with a Gauss function. We have used computer simulation and tried to emphasize the qualitative relationship between the properties. We conclude with some practical requirements and show the need of a numerical design procedure if the slice properties have to be optimized.

Spectro-temporal modulation transfer function (STMTF) for various types of temporal modulation and a peak distance of 200 Hz.

Abstract: For noise which is spectrally modulated (ripple noise) as well as temporally modulated (the ripples move), the Spectro‐Temporal Modulation Transfer Function (STMTF) is defined as the curve relating modulation threshold to temporal modulation frequency with ripple spacing as a parameter. A white noise stimulus was spectro‐temporally modulated in the 0.2‐ to 1.0‐kHz region with a spectral modulation frequency (peak distance) of 0.2 kHz. Three types of temporal modulation were applied: the ripples rolled upward, downward, or the peaks and troughs interchanged periodically. It is shown that the STMTFs for these types are equal. So, for a ripple spacing of 0.2 kHz the spectro‐temporal modulation thresholds are independent of the type of temporal modulation. These STMTFs appeared to be low‐pass functions, no minimum was found. Their plateaus were at the same modulation depth as the modulation thresholds found by previous investigators who employed stationary ripple noise.

A communication system having improved differential phase shift keying modulation.

Abstract: A communication system (10) which generates an output signal of a selected primary frequency having digital data bits serially modulated thereon by utilizing a hybrid differential phase shift keyed (DPSK) modulation. The improved DPSK modulation is frequency modulation of a phase encoded signal. A controller (12) controls frequency generator means (14 and 16) which frequency shift the output signal between primary and secondary frequencies. The controller (12) and frequency generator means (14 and 16) provide a modulated output signal which is D.C. balanced bit by bit and has substantially reduced harmonic energy.

Pulse width modulation circuit and integration circuit of analog product using said modulation circuit

Abstract: A pulse width modulation circuit which can cancel the mean error of pulse width modulation with respect to time due to the offset voltage of a triangular wave signal and to the offset voltage of a comparator, by adding simple circuits to an existing pulse width modulation circuit. The invention relates also to an integration circuit of the product of two analog signals using the pulse width modulation circuit described above. The principle of the present invention combines a circuit for cancelling the offset of a triangular wave signal by inverting either the triangular wave signal with respect to an input signal or the input signal with respect to the triangular wave signal, in every predetermined period, with a circuit for eliminating the offset of a comparator by inverting the output of the comparator and replacing the input terminals of the comparator if the input signal is not inverted, or connecting the input terminal of the comparator as such if the input signal is inverted.

High-frequency power amplifier with a modulation circuit

Abstract: 1. High-frequency power amplifier with a modulating facility (5, 8, 10, 15, 16) for generating pulse signals wherein the pre-emphasized analog modulating signal is derived from a plurality of digital amplitude values which are stored in a memory (6) and whose envelope is the pre-emphasized modulation signal, wherein, for the purpose of determining the necessary pre-emphasis, a portion of the analog modulated amplifier output signal is extracted (14) and compared with a reference signal and wherein, depending on the result of the comparison, the stored digital amplitude values are altered to provide such a pre-emphasis for the analog modulation signal that the amplifier output signal has the desired shape, characterized in that the extracted signal, which is the actual signal, is digitalized (10) so as to be described by a plurality of actual amplitude values, that the reference signal consists of a plurality of digital reference amplitude values stored in a memory (3), that the differences (D) between the actual amplitude values and the reference amplitude values are formed (3, 4) and that, at least during the adjustment time, the value by which a stored amplitude value is corrected is determined by the difference found for this amplitude value minus an amplifier-specific value (K1) which depends on the slope of the amplifier characteristic at the amplitude value to be corrected plus the least of those differences (K2) between the actual and reference amplitude values which chronologically follow the amplitude value to be corrected.

The Selection of Modulation Rates for Frequency Modulated Sound Field Stimuli

Abstract: Frequency modulated (FM) tones are used in sound field audiometry in order to avoid problems caused by standing waves. The FM stimuli to be used must be specified in terms of bandwidth (twice the frequency deviation), modulation rate and modulation waveform. This paper deals with selection of the modulation rate. Improved field uniformity obtained with FM tones relies upon the ear averaging the sound intensity as the frequency sweeps. The modulation rate must be less than about 1/3 of the frequency deviation in order to provide sufficient spectral components to ensure reasonable averaging across the frequency band. If the rate is too low threshold will be determined by the peak intensity during the sweep. For normal listeners a modulation rate of 5 Hz is just satisfactory but in the hearing impaired a higher rate is required because of their altered temporal integration characteristics. A suitable value for the modulation rate can be inferred from the literature on temporal integration and the acoustic ch...

Low q body dithered laser gyro assembly

Abstract: A low Q ring laser gyro-dither motor assembly which is responsive to a wide range of frequency components of a drive signal having a randomly varying frequency such that the dither imparted to the gyro is frequency modulated by the drive. The frequency modulated dither varies the lock-in rate of the gyro as a function of the random drive signal to eliminate errors in the gyro output due to lock-in. The drive signal may be random in frequency only or random in both frequency and amplitude to provide the frequency modulation. Fixed frequency modulation may also be employed. The low Q assembly need not be driven at the natural frequency thereof so that a common drive circuit may be employed for a plurality of low Q gyro-dither motor assemblies forming an instrument cluster.

A method in the signal processing of a received train of pulses, and a receiver for carrying out the process

Abstract: A method in signal processing of a train of pulses with a stable, high repetition frequency f,, in particular in connection with dispersion measurements of optical fibers, comprises sampling (1) of the received signal at a sampling frequency f., where (n is an integer and Δf is several magnitudes smaller than f,). When the sampling frequency is generated by a pulse generator (2), which, through a phase-detecting circuit (4), depends on partly a reference signal (from the oscillator 6) and partly a low frequency signal derived (via 5) from the signal received and sampled at the frequency f s , a stable sampling frequency is obtained even though the signal/noise ratio on the input of the receiver is significantly smaller than was permissible in the past. When the method is to be carried out within a relatively narrow repetition frequency range, the oscillator (6) is preferably replaced by a frequency dividing circuit designed to generate a reference signal by division of the sampling frequency.

Modulation circuit of a digital-to-analog converter

Abstract: A modulation circuit of a D/A converter comprises a pulse number modulation circuit for modulating some bits of digital data and for dispersing a pulse or pulses in one or more resultant pulses, a pulse width modulation circuit for modulating the remain bits of the digital data and for dividing pulses in a resultant pulse train and a combination circuit for combining and positioning at least one pulse in the pulse train adjacent the pulse or pulses in the one or more resultant pulses formed by the pulse number modulation circuit.

Influence of modulation frequency in rubidium cell frequency standards

Abstract: The error signal which is used to control the frequency of the quartz crystal oscillator of a passive rubidium cell frequency standard is considered. The value of the slope of this signal, for an interrogation frequency close to the atomic transition frequency is calculated and measured for various phase (or frequency) modulation waveforms, and for several values of the modulation frequency. A theoretical analysis is made using a model which applies to a system in which the optical pumping rate, the relaxation rates and the RF field are homogeneous. Results are given for sine-wave phase modulation, square-wave frequency modulation and square-wave phase modulation. The influence of the modulation frequency on the slope of the error signal is specified. It is shown that the modulation frequency can be chosen as large as twice the non-saturated full-width at half-maximum without a drastic loss of the sensitivity to an offset of the interrogation frequency from center line, provided that the power saturation factor and the amplitude of modulation are properly adjusted.

Signal-to-noise performance of the pulse-interval and width-modulation system

Abstract: A simple formula for the signal-to-noise ratio at the output of the pulse-interval and width-modulation (PIWM) system is derived. The predicted performance is compared with measured data obtained from a hardware model of the system. Simulation results are in good agreement with predictions.

A pulse width modulation circuit and an analog product forming integration circuit using such modulation circuit

Abstract: A pulse width modulation circuit is capable of cancelling the mean error of pulse width modulation with respect to time due to the offset voltage of a triangular wave signal and to the offset voltage of a comparator, by adding simple circuits (FF3, L1, L2) to an existing pulse width modulation circuit (10, CP3). Such pulse width modulation circuit is used preferably in an integration circuit forming the product of two analog signals. The offset of the triangular wave signal (VA) is cancelled by inverting either the triangular wave signal with respect to the input signal or the input signal with respect to the triangular wave signal, in every predetermined period. To this end, the circuit eliminates the offset of a comparator (CP3) by inverting the output of the comparator and replacing the input terminals of the comparator if the input signal is not inverted, or connecting the input terminal of the comparator as such if the input signal is inverted.

Frequency to voltage converter for a predetermined frequency range

Abstract: An electronic circuit receives an input of voltage pulses whose frequency of a predetermined range represents a variable to be manifested. The first train of pulses of varying frequency is applied to a one-shot monostable multivibrator which produces a second train of pulses, each of which has a duration representative of the maximum frequency of the predetermined range. The output of the one-shot controls a gate through which passes a third train of pulses of constant frequency and shape between the pulses of the second train. Counting, latch, and analog circuits respond to the third train of pulses to manifest the frequency of the first pulse train within its predetermined range.

Transfer Mode Inverter Consisting of Uniform Pulses

Abstract: Most DC-AC inverters are apoted to control gate circuit of pulse with modulation technique, but the circuit which consists of un-uniform pulse is more complicated than this paper. This paper describes theory and more simple of circuit which is controlled by uniform pulse width modulation technique (UPWM).

A Resonant Type Constant Current Converter with Feedback

Abstract: A constant current converter of resonant type is presented. It is composed of the PWM control inverter, the main resonant circuit and the integrator for the feedback. The inverter being driven at high frequency, the size of the whole device can be minimized. By making use of the PWM controller and the integrator for the feedback, the output current is regulated precisely against the change of the input voltage and the loading.

Detection device for car traveling condition

Abstract: PURPOSE:To realize detection of traveling condition reasonably by means of a simple structure by converting a speed signal into frequency modulated pulse signals and comparing those two outputs by means of a comparator after giving them different time constants in a time constant circuit CONSTITUTION:A pulse signal Sp of the definite breadth and inverted output -Sp, both frequency modulated from the signals corresponding to speed through a pulse frequency modulation circuit A, is respectively inputted to frequency/ voltage conversion circuits Ba, Bb and outputs respectively voltage outputs -Sv, Sv Further, after being furnished with different time constants through resistances 21, 22 and condensers 22, 29, they are respectively inputted to comparators 18, 19 The first comparator 18 discriminates accelerated traveling condition from other conditions, while the second comparator 19 discriminates decelerated traveling condition from other conditions, and three conditions of acceleration, constant speed and deceleration are obtained from various forms of combination of two outputs Soa, Sob through a logical circuit Thus, traveling condition detection signals can be obtained simply and logically