scispace - formally typeset
Search or ask a question

Showing papers on "Pulse-frequency modulation published in 1985"


Journal ArticleDOI
TL;DR: It is concluded that in general the spectral properties of the input signal cannot be recovered fully from the interval spectrum, nor from the spectrum of counts, the more so as physiological series of events will seldom be generated by an ideal IPFM model.
Abstract: The paper deals with the relationship between the spectra of the input signal and the output signal of the integral pulse frequency modulation (IPFM) model. The IPFM model is a physiologically attractive device for the conversion of a continuous input signal into an output signal, consisting of a series of events (e.g. nerve spikes, heart beats). Two different spectra are used in the analysis of a series of events; the interval spectrum and the spectrum of counts. The latter spectrum is known analytically for the event series belonging to a sinusoidal input signal. An approximation to the interval spectrum of this series is presented. Using data from a simulated IPFM model, it is shown that, for an input signal consisting of the sum of two sinusoids, terms at sum and difference frequencies appear in the interval spectrum but not in the spectrum of counts. However, the spectrum of counts is contaminated by sidebands of the mean repetition frequency. It is concluded that in general the spectral properties of the input signal cannot be recovered fully from the interval spectrum, nor from the spectrum of counts, the more so as physiological series of events will seldom be generated by an ideal IPFM model.

91 citations


Patent
06 Dec 1985
TL;DR: In this article, an integrated circuit contains the gate drivers and the control components for constructing a DC power supply in any of the most popular converter topologies, including half-bridges.
Abstract: An integrated circuit contains the gate drivers and the control components for constructing a DC power supply in any of the most popular converter topologies. Multi-function elements in the control circuit minimize the area of the chip. The integrated circuit drives both the upper and lower switches of a half-bridge converter and separately regulates two power supply output voltages, one by pulse width modulation and the other by frequency modulation.

87 citations


Proceedings ArticleDOI
26 Apr 1985
TL;DR: Equations of R for four modulation types, as a function of the carrier to noise ratio, are derived and used to set up a classification scheme and confirm the effectiveness of the identification scheme.
Abstract: It is possible to recognize the modulation type of an unknown signal in noise by its envelope characteristics. A quantity found to be distinctive to a given modulation type is the ratio (R) of the variance of the envelope to the square of the mean of the envelope. Equations of R for four modulation types, as a function of the carrier to noise ratio, are derived and used to set up a classification scheme. The R of a received signal is first computed. Then its modulation type is determined according to the range R falls in. Simulation experiments have confirmed some of the theoretical development as well as the effectiveness of the identification scheme.

63 citations


Journal ArticleDOI
TL;DR: In this paper, a negative frequency feedback control was used to reduce frequency modulation (FM) noise linewidth in semiconductor lasers, which is based on the direct frequency modulation capability of a semiconductor laser and an error signal was extracted through optical heterodyne frequency discrimination detection using a stable master laser.
Abstract: Electrical negative frequency feedback control has been shown to reduce frequency modulation (FM) noise linewidth in semiconductor lasers. The method is based on the direct frequency modulation capability of a semiconductor laser. An error signal is extracted through optical heterodyne frequency discrimination detection using a stable master laser. FM noise is reduced by more than 20 dB and linewidth is reduced by one order of magnitude.

55 citations


Journal ArticleDOI
TL;DR: Video transmission experiments demonstrate the advantages of the SWFM, including degree of simplicity in modulation/demodulation circuits as well as in optical transmitter and receiver circuits, tolerance to nonlinearities in the system, and insensitivity to the fiber baseband frequency-phase characteristics.
Abstract: Investigations are carried out on the performance of video transmission systems employing square wave frequency modulation (SWFM). A simple formula for the signal-to-noise ratio (SNR) in the SWFM video transmission systems is derived. The SNR performance is compared to that of frequency modulation (FM) and pulse frequency modulation (PFM). SWFM is shown to display the greatest receiver sensitivity when the fiber 6 dB bandwidth is less than 100 MHz. Video transmission experiments demonstrate the advantages of the SWFM, including 1) degree of simplicity in modulation/demodulation circuits as well as in optical transmitter and receiver circuits, 2) tolerance to nonlinearities in the system, and 3) insensitivity to the fiber baseband frequency-phase characteristics. Both the theoretical and experimental results have made clear the superiority of SWFM optical video transmission systems in application to CATV distribution systems and subscriber loop systems.

45 citations


Journal ArticleDOI
Govind P. Agrawal1
TL;DR: In this article, the time-averaged power spectrum of a single-mode semiconductor laser under direct current modulation is calculated using the small-signal analysis of the stochastic rate equations.
Abstract: The time-averaged power spectrum of a single-mode semiconductor laser under direct current modulation is calculated using the small-signal analysis of the stochastic rate equations. The general formalism includes the effect of frequency chirping owing to current modulation as well as the effect of phase diffusion related to spontaneous emission. Chirp-induced dynamic line broadening is shown to result from a superposition of the additional unresolved sidebands generated at multiples of the modulation frequency on both sides of the optical line. The effect of intensity modulation is to introduce an asymmetry such that the low-frequency sideband has a relatively higher amplitude. The theory explains reasonably well the reported experimental observations. At the same time it provides physical insight into the dynamic process of frequency chirping and its relation to the frequency modulation. In particular, the frequency and the decay rate of transient relaxation oscillations govern the interplay between simultaneously occurring intensity and frequency modulations.

38 citations


Patent
10 Jun 1985
TL;DR: In this article, a sub-center type switched-star CATV system network is considered, where a number of transmission signals are transmitted from a central source to a many of sub-centers over a set of sets of optical fibers, and each signal is converted into a frequency modulation signal by first frequency dividing the signal and then passing the divided signal through a band-pass filter which eliminates all signal components except the fundamental frequency.
Abstract: A sub-center type switched-star CATV system network in which a number of transmission signals are transmitted from a central source to a number of sub-centers over a number of sets of optical fibers. In view of the long distances involved, the transmission signals are transmitted in pulse frequency modulation form, one pulse frequency modulation signal being applied to each optical fiber. At each sub-center, each pulse frequency modulation signal is converted into a frequency modulation signal by first frequency dividing the pulse frequency modulation signal and then passing the divided signal through a band-pass filter which eliminates all signal components except the fundamental frequency. The pulse frequency modulated signals may pass through a switch to select the number of transmission signals which ultimately reach the subscribers. The frequency modulated signals are then frequency multiplexed to produce a multiplexed signal and the multiplexed signal is sent to a number of subscribers. A single optical fiber connects a sub-center with each associated subscriber, respectively. At each subscriber, the multiplexed signal is converted back into the selected number of transmission signals.

35 citations


Journal ArticleDOI
J. E. Bowers1, Won-Tien Tsang1, Thomas L. Koch1, N. A. Olsson1, R. A. Logan1 
TL;DR: In this paper, the intensity and frequency modulation response of heteroepitaxial-ridge-overgrown distributed feedback lasers are characterized as a function of modulation frequency from 0.2 to as high as 17 GHz.
Abstract: The intensity and frequency modulation response of heteroepitaxial‐ridge‐overgrown distributed feedback lasers are characterized as a function of modulation frequency from 0.2 to as high as 17 GHz. Small‐signal intensity modulation measurements show a −3 dB frequency of 7.1 GHz. Efficient frequency modulation (>0.1 GHz/mA) is demonstrated for modulation frequencies up to 13 GHz. A new standard for comparing semiconductor lasers, the chirp to modulated power ratio, is suggested as a means of comparing semiconductor lasers and as an aid to understanding the interaction of FM and IM in a semiconductor laser.

34 citations


Patent
14 Jan 1985
TL;DR: A hysteresis circuit is provided within the pulse generating means to guarantee that once the pulse generation has stopped it will not increase again as a result of the aforementioned motor voltage rise.
Abstract: Motor control apparatus for controlling the speed of a motor as a function of a variable frequency square wave and chopping pulses. The chopping pulses are cut off at some value greater than zero pulse width which causes motor voltage to increase in a step manner thus causing a feed forward voltage signal which is related to a DC rectified voltage which cooperates with the square wave production system to increase accordingly. A hysteresis circuit is provided within the pulse generating means to guarantee that once the pulse generation has stopped it will not increase again as a result of the aforementioned motor voltage rise.

21 citations


Patent
08 Jul 1985
TL;DR: In this paper, the attenuation of an optical waveguide is measured by comparing the light power input into the waveguide with light power output from a light receiver, where the input power is encoded on the light signal by pulse frequency modulation.
Abstract: The attenuation of an optical waveguide is measured by comparing the light power input into the waveguide with the light power output from the waveguide. The input power is encoded on the light signal by pulse frequency modulation. The output power is measured by a light receiver.

20 citations


Patent
20 May 1985
TL;DR: In this paper, a microcomputer is programmed to respond to the zero crossings of an AC power source to trigger a uniform pulse pattern of an integral number of AC cycles as the AC excitation to a heater element to maintain the temperature of the heater element essentially constant.
Abstract: A microcomputer is programmed to respond to the zero crossings of an AC power source to trigger a uniform pulse pattern of an integral number of AC cycles as the AC excitation to a heater element to maintain the temperature of the heater element essentially constant.

Patent
John R. Sonnenberg1
29 Mar 1985
TL;DR: In this paper, a method for flattening the modulation response in a frequency synthesizer is presented. But the method is not suitable for the use of a single-input single-output (SISO) mode.
Abstract: In accordance with the present invention, there is provided a method of substantially flattening the modulation response in a frequency synthesizer. The method includes the steps of generating a synthesized frequency in response to a filtered control signal; scaling the synthesized frequency with a scalar; generating a control signal, having a response substantially the reciprocal of the frequency generation response, and indicative of the phase relationship between a reference frequency and the scaled, synthesized frequency; and filtering the control signal, whereby the interaction of the phase relationship control signal response and the frequency generation response approximates a flat modulation response.

Patent
Randy L. Dahl1
29 Jul 1985
TL;DR: In this article, a modulation circuit is designed to provide an LED with a more analog type signal, which in turn causes the LED to emit a signal that is peaked rather than a constant square wave providing a better conversion frequency to the fundamental frequency.
Abstract: The present invention consists of a modulation circuit used in a digital application The modulation circuit is designed to provide an LED with a more analog type signal This in turn causes the LED to emit a signal that is peaked rather than a constant square wave providing a better conversion frequency to the fundamental frequency

Patent
16 Oct 1985
TL;DR: In this paper, the authors describe the process of converting a BINARY TRAIN in a FIELD SIGNAL to an ANALOGUE MODULE, which is then converted to a PREDETERMINED FREQUENCY STATIONARY SIGNAL.
Abstract: MODEM COMPRISING A MODULATION SECTION FOR CONVERTING A BINARY TRAIN IN A FIELD SIGNAL AND A DEMODULATION SECTION FOR CONVERTING A FIELD SIGNAL OF A CONVERTIBLE PHASE MODULE IN BINARY TRAIN FROM WHICH THIS IF SIGNAL HAS BEEN CONVERTED. IN THE BINARY TRAIN, EACH NUMBER GIVES SUCCESSIVE BITS DEFINING A SYMBOL. IN THE MODULATION SECTION, EACH SYMBOL IS MODULE IN PHASE BY MDDP CONVERSION (PHASE DIFFERENTIAL DISPLACEMENT MODULATION). THE SYMBOLS ARE DIGITALLY FILTERED BY A RIF FILTER 13 TO PROVIDE A FILTER SIGNAL THAT, CONVERTED IN AN ANALOGUE SIGNAL, PROVIDES A MODULATION SIGNAL HAVING A MODULATION FREQUENCY CENTERED ON A PREDETERMINED FREQUENCY AND WHICH DISTANCES ACCORDING TO THE VALUE OF THE SYMBOL. THE FILTER SIGNAL IS CONVERTED TO AN ANALOGUE SIGNAL AND MIXES TO A PREDETERMINED FREQUENCY STATIONARY SIGNAL TO PROVIDE A PHASE MODULE IF SIGNAL, THAT IS, A FM FREQUENCY MODULE SIGNAL HAVING FI FREQUENCY THAT IS A MODULATION PRODUCT OF FREQUENCY OF MODULATION AND PREDETERMINED FREQUENCY. IN THE RECEPTION SECTION, A RIF DIGITAL FILTER HAS A MICROPROCESSOR 17 FOR FILTERING THE RECEIVED DIGITAL SIGNAL, AND THE MOISTROGRAMMER INCLUDES A MEMORY FOR STORING THE COEFFICIENTS OF THE RIF FILTER.

Patent
Hoen Pieter Johannes 't1
28 Oct 1985
TL;DR: A zero crossing detection circuit and method for estimating the ultrasonic attenuation in a region of interest (210) in the body (200) from an A-line signal A(t) which is representative of pulses of ultrasound energy reflected from said region is presented in this paper.
Abstract: A zero crossing detection circuit and method for estimating the ultrasonic attenuation in a region of interest (210) in the body (200) from an A-line signal A(t) which is representative of pulses of ultrasound energy reflected from said region. The A-line signal A(t) is converted into a square pulse train signal Vu(t) which has a value of zero when the instantaneous voltage of the A-line signal is at or below zero and which has a value of Vref whenever the instantaneous voltage of the A-line signal is greater than zero. The ultrasound attenuation is estimated from the center frequency fz of the return energy which is calculated from the formula: as measured at various depths in the body, n being the number of pulses in the pulse train signal.

Journal ArticleDOI
TL;DR: Measurements of the modulation detectability threshold of a frequency-modulated tone, which had a modulation waveform spectrum consisting of three components: one component at the modulation rate and two sidebands which could be set to different frequency positions on either side of it, revealed that when the two side bands were located within a limited bandwidth around the central component they contributed to the detection of the modification.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a system employing a wavelength-division multiplexed star network which is satisfactory for the transmission of video signals in addition to digital data, and reports the evaluation results of the video transmission characteristics of the system employing 32 port-pair passive star coupler.
Abstract: In local area networks (LAN's), it is desirable to transmit not only digital data but also moving video signals. This paper proposes a system employing a wavelength-division multiplexed star network which is satisfactory for the transmission of video signals in addition to digital data, and reports the evaluation results of the video transmission characteristics of the system employing a 32 port-pair star coupler. Video transmission was realized by the pulsed analogue transmission scheme. Pulse frequency modulation (PFM) and pulsed frequency modulation (pulsed-FM) were studied, and it was found that the SNR fluctuation due to modal noise was less by the pulsed-FM than by the PFM. It was also found that the difference in the modal noise was due to the differences in the demodulation characteristics of PFM and pulsed-FM. A 32 port-pair passive star coupler was used and a maximum of a 5-km network was experimented. The results showed that a good video SNR was obtainable in the experimental star network using laser diodes. Thus the feasibility of the broad-band network, employing a multiport-pair passive star coupler by the wavelength division multiplexing scheme, was proven.

Journal ArticleDOI
TL;DR: In this paper, a numerical method is described for predicting the detection probability of a frequency compressive pulse receiver, i.e., input pulse envelope shapes, pulse offset frequencies, and filter magnitude responses are arbitrary.
Abstract: A numerical method is described for predicting the detection probability of a frequency compressive pulse receiver. The approach is general; i.e., input pulse envelope shapes, pulse offset frequencies, and filter magnitude responses are arbitrary. The performance of the frequency compressive receiver is analyzed and compared to that of a crystal video receiver for a specific case.

Journal ArticleDOI
TL;DR: In this paper, the relationship between the laser segment versus modulator segment current at constant output power and residual amplitude modulation of the output power when operating in the FM mode is determined.
Abstract: Cleaved coupled-cavity (C3) lasers are analyzed. Results are developed for longitudinal mode tuning and enhanced frequency modulation (FM) caused by amplitude modulation of the rear section. In addition, curves of laser segment versus modulator segment current at constant output power are calculated and residual amplitude modulation of the output power when operating in the FM mode is also determined. Both long-long and long-short C3devices are studied for strong, intermediate, and weak coupling between the segments. Because of the strong sensitivity to gap spacing, results are presented for many configurations which differ only by one-eighth wavelength in that dimension. This distance corresponds to a quarter wavelength in two passes. Analytic results are compared with previously published experimental observations.

Journal ArticleDOI
TL;DR: In this paper, a PbSnTe diode laser around 10.6 μm was stabilized under very small frequency modulation to one of the absorption lines of C 2 H 4 in the ν 7 band.
Abstract: The frequency of a PbSnTe diode laser around 10.6 μm was stabilized under very small frequency modulation to one of the absorption lines of C 2 H 4 in the ν 7 band. The frequency control and modulation were performed by the injection current. The minimum modulation width in this experiment was analytically determined to be 1.1 MHz. From analysis of a linear approximate model for the experimental system, the frequency fluctuation, which represents peak-to-peak width during 5 min, including the modulation width, was estimated to be 3.8 \times 10^{-8} . This value was about two orders larger than the value obtained by the ordinary method, which is a simple conversion of the control error signal.

Journal ArticleDOI
TL;DR: In this paper, a four-quadrant time-division analogue multiplier based on a pulse-interval amplitude-modulation (PIAM) technique is proposed, which does not require an external triangular-wave generator for its operation.
Abstract: A four-quadrant time-division analogue multiplier based on a pulse-interval amplitude-modulation (PIAM) technique is proposed. This multiplier is self-triggered and thus does not require an external triangular-wave generator for its operation, unlike other time-division multipliers. A practical circuit has been designed and tested. Experimental results agree closely with theory.

Journal ArticleDOI
A. Drukarev1
TL;DR: In this correspondence, it is shown that in systems with signal-independent white noise, the SNR threshold is approximately 20 dB, and a more general expression describing noise performance of PFM, both above and below theSNR threshold, is derived.
Abstract: Pulse frequency modulation (PFM) has been considered by several authors for transmitting wide-band signals. However, the noise performance of PFM has been analyzed only above the SNR threshold. In this correspondence the results on the noise performance of PFM available in the literature are summarized, and a more general expression describing noise performance of PFM, both above and below the SNR threshold, is derived. This expression can be used to evaluate the SNR threshold for channels with both signal-independent noise (e.g., metallic facilities) and signal-dependent noise (e.g., fiber optic facilities). In particular, it is shown that in systems with signal-independent white noise, the SNR threshold is approximately 20 dB.

Journal ArticleDOI
TL;DR: In this article, a monopulse to twin-pulse conversion in pulse frequency modulation optical transmission was used to reduce the modal noise in the optical transmission of a single-input single-output (SISO) system.
Abstract: Modal noise was reduced fairly by monopulse to twin-pulse conversion in pulse frequency modulation optical transmission. The pulsewidth was chosen to be less than the time in which dynamic spectral broadening was maintained. The technique is the most promising for modal noise elimination.

Journal ArticleDOI
TL;DR: In this article, an expression for the frequency spectrum of PIM was derived using the pseudo-static approach, which predicts the presence of modulating frequency harmonics caused by higher values of modulation depth.
Abstract: An expression for the frequency spectrum of pulse-interval modulation (PIM) is derived using the pseudo-static approach. The theoretical results predict the presence of modulating frequency harmonics caused by higher values of modulation depth. Experimental results obtained from a hardware model confirm the validity of the proposed method of analysis.

Patent
30 Jul 1985
TL;DR: In this article, the authors proposed a scheme to attain the monitoring of a normal signal in the constitution not using a switch while decreasing the shape and a drive current by applying the method where a high speed pulse signal passes through a switch after the signal is demodulated into a base band signal.
Abstract: PURPOSE:To attain the monitoring of a normal signal in the constitution not using a switch while decreasing the shape and a drive current by applying the method where a high speed pulse signal passes through a switch after the signal is demodulated into a base band signal and the method where the high speed pulse signal passes directly through a logical switch. CONSTITUTION:Modulation circuits 1, 11 apply the modulation including a base band component of a modulation signal to a modulation output such as pulse frequency modulation (PFM), pulse phase modulation (PPM), pulse width modulation (PWM) and pulse amplitude modulation (PAM). From an output of amplifier circuits 6 and 16, a signal similar to signal input terminals S1, S2 is demodulated to obtain a pulse modulation signal with less deterioration of waveform. Since the operation of a transmission section of a transmitter is supervised at all times at monitor terminals Ms1, Ms2, a faulty position generated in the transmission system at directions from an input terminal Si1 to an output terminal So1 and from the input terminal Si2 to an output terminal So2 is sectioned to the transmission section including the light source and other parts.


Journal ArticleDOI
D.J.T. Heatley1
TL;DR: In this article, the authors compared the performance of the dual-pulse demodulation approach with the traditional one pulse per PFM signal period approach and found that the dual pulse approach gave an SNR advantage of up to 7 dB for the same input conditions, but the two methods give SNRs which converge when used to demodulate FM.
Abstract: PFM demodulation which relies on the generation of one pulse per PFM signal period is compared with demodulation which generates two pulses per period. The dual pulse approach is shown to give an SNR advantage of up to 7 dB for the same input conditions, but the two methods give SNRs which converge when used to demodulate FM.

Journal ArticleDOI
TL;DR: In this article, an 835 nm superluminescent diode with a spectral width of 8 nm was used to reduce SNR fluctuations due to modal noise significantly in PFM optical video transmission.
Abstract: An 835 nm superluminescent diode with a spectral width of 8 nm is shown to reduce SNR fluctuations due to modal noise significantly in PFM optical video transmission. An SNR of 56 dB and DG/DP of 06%/0.3° are achieved over 5 km with a frequency deviation of only 400 kHz. The SNR fluctuation is less than 0.05 dB.

Patent
12 Nov 1985
TL;DR: In this paper, a method for the transmission of digital data, characterized by differential frequency shift keying about a center modulation frequency Fo, was proposed, which is characterized in that it consists: - when transmitting, in an encoding by differential Frequency Shift keying, while associating with each symbol consisting of k bits to be transmitted a frequency shift DF, selected from a table containing 2**k possible frequency shifts respectively associated with 2 *k possible symbols of K bits, in adding respectively substracting this shift to respectively from the frequency associated with the preceding symbol according to whether the
Abstract: 1. A method for the transmission of digital data, characterized in that it consists : - when transmitting, in an encoding by differential frequency shift keying about a center modulation frequency Fo , while associating with each symbol consisting of k bits to be transmitted a frequency shift DF, selected from a table containing 2**k possible frequency shifts respectively associated with 2**k possible symbols of k bits, in adding respectively substracting this shift to respectively from the frequency associated with the preceding symbol according to whether the preceding frequency is lower or higher than the modulation center frequency, and in transmitting the corresponding frequency during the period of the symbol, the modulation signal resulting from the encoding being passed on for the purpose of transmission, - when receiving, in the decoding of the associated modulation by way of estimating for the interval of the symbols contained in a signal segment, the latter being defined by means of a synchronization signal having the modulation frequency and synchronized with the received modulated signal, an assessment of the frequencies successively received, and in deriving therefrom the corresponding frequency shifts and thus the received symbols.

Journal ArticleDOI
TL;DR: In this paper, the authors derived analytically for purely dispersive optical bistability in the bad cavity case, where the modulation can be applied to the holding beam, to the refraction index or to the detuning with similar results for the output field intensity.