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Showing papers on "Pulse-frequency modulation published in 1989"


Journal ArticleDOI
TL;DR: Modulation thresholds were measured for a sinusoidally amplitude-modulated (SAM) broadband noise in the presence of a SAM broadband background noise with a modulation depth of 0.00, 0.25, or 0.50, suggesting that there are channels in the auditory system which are tuned for the detection of modulation frequency, much likethere are channels (critical bands or auditory filters) tuned forThe detection of spectral frequency.
Abstract: Modulation thresholds were measured for a sinusoidally amplitude‐modulated (SAM) broadband noise in the presence of a SAM broadband background noise with a modulation depth (mm) of 0.00, 0.25, or 0.50, where the condition mm=0.00 corresponds to standard (unmasked) modulation detection. The modulation frequency of the masker was 4, 16, or 64 Hz; the modulation frequency of the signal ranged from 2–512 Hz. The greatest amount of modulation masking (masked threshold minus unmasked threshold) typically occurred when the signal frequency was near the masker frequency. The modulation masking patterns (amount of modulation masking versus signal frequency) for the 4‐Hz masker were low pass, whereas the patterns for the 16‐ and 64‐Hz maskers were somewhat bandpass (although not strictly so). In general, the greater the modulation depth of the masker, the greater the amount of modulation masking (although this trend was reversed for the 4‐Hz masker at high signal frequencies). These modulation‐masking data suggest ...

191 citations


Journal ArticleDOI
TL;DR: It is argued that the present results on frequency selectivity in modulation detection underline the perceptual relevance of a spectral decomposition of a signal’s temporal envelope and provide a rationale for the application of modern concepts like the speech‐envelope spectrum or the modulation‐transfer function in relation to speech intelligibility.
Abstract: For a broadband noise carrier, the modulation detection threshold for sinusoidal amplitude modulation (the test modulation) is measured in the presence of an additional modulation (the masker modulation). Two traditional approaches for revealing effects of frequency selectivity in the audiofrequency domain are shown to give comparable results in the modulation‐frequency domain: (1) a typically peaked modulation‐detection threshold pattern when the masker modulation is a fixed narrow band of noise, and (2) an effect of leveling off of the increase of the modulation‐detection threshold when, for a fixed test‐modulation frequency, the masker‐modulation bandwidth is widened beyond a certain ‘‘critical’’ bandwidth. It is argued that the present results on frequency selectivity in modulation detection underline the perceptual relevance of a spectral decomposition of a signal’s temporal envelope and provide a rationale for the application of modern concepts like the speech‐envelope spectrum or the modulation‐transfer function in relation to speech intelligibility.

188 citations


Proceedings ArticleDOI
01 Oct 1989
TL;DR: In this paper, a pulsewidth modulation (PWM) control technique for forced commutated cycloconverters is presented, based on the space vector representation of the voltages in the complex plane.
Abstract: A pulse-width modulation (PWM) control technique for forced commutated cycloconverters is presented. The technique is based on the space vector representation of the voltages in the complex plane. It is shown that with the allowable switching combinations, six output voltage space vectors with varying amplitudes can be obtained, in addition to the zero vector. The variation is compensated by adapting the standard modulation technique. The technique permits space vector synthesis of a three-phase, nonsymmetrical, nonsinusoidal output voltage, even under non-steady-state conditions, which is essential for the control of AC servo drives. A detailed explanation of the modulator principles and the switch control as well as simulation results for the time- and frequency domain analysis is given. The results are compared with the results obtained using the standard modulation technique. A possible microprocessor implementation of the modulator is also proposed. >

131 citations


Proceedings ArticleDOI
15 Oct 1989
TL;DR: A modulation recognizer that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques, and results demonstrate that reasonable average probability of correct classification is achievable at CNR=15 dB and higher.
Abstract: A modulation recognizer that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques. The zero-crossing sampler, as a signal conditioner, has the advantage of providing accurate phase transition information over a wide dynamic frequency range. Signal parameters, such as zero-crossing variance, carrier-to-noise ratio (CNR), and carrier frequency, are estimated. Phase-difference and zero-crossing-interval histograms play the roles of features for modulation recognition. The classifier performance is given in the form of a confusion matrix. The obtained simulation results demonstrate that reasonable average probability of correct classification is achievable at CNR=15 dB and higher. >

98 citations


Patent
14 Jul 1989
TL;DR: A balanced transformer-less pulse width modulation amplifier circuit has two filter coils wound on the same core with the same polarity relative to the output as discussed by the authors, which reduces the possibility of magnetic saturation of the core and permits the cutoff frequency to be within the audio range.
Abstract: A balanced transformer-less pulse width modulation amplifier circuit has two filter coils wound on the same core with the same polarity relative to the output. The arrangement reduces the possibility of magnetic saturation of the core and permits the cutoff frequency to be within the audio range.

82 citations


Journal ArticleDOI
TL;DR: The spectral responses of cat single primary auditory nerve fibers to sinusoidal frequency-modulated acoustic signals applied to the ear are examined and it is indicated that a demodulation process is occurring, which may be significant for speech recognition.

50 citations


Proceedings ArticleDOI
13 Mar 1989
TL;DR: In this article, a modified circuit based on parallel operation of MOS-based inverter sets using interphase reactors as harmonic reducing elements is investigated as a means to economically and efficiently reduce the harmonic contents in the output waveform.
Abstract: A technique is presented for harmonic reduction in inverters using sinusoidal pulse-width modulation (PWM). A modified circuit based on parallel operation of MOS-based inverter sets using interphase reactors as harmonic reducing elements and making use of a specific phase shift between the modulating and carrier waveforms is investigated as a means to economically and efficiently reduce the harmonic contents in the output waveform. The output waveform of a single-phase PWM inverter is investigated both theoretically and experimentally. Detailed analysis shows that the harmonics lower than the 15th are all less than 1% of the fundamental component when the frequency ratio is relatively low, i.e. about nine and similarly for the 29th harmonic when the ratio is about 15. This is done without noticeable reduction in the fundamental component. The results show the feasibility of obtaining practically sinusoidal output waveforms. >

22 citations


Patent
26 Jun 1989
TL;DR: In this article, a radio frequency excited carbon dioxide laser (50) is stabilized by sensing a variation in output power to generate a feedback signal (68,78 ) that is employed to vary amplitude of the radio frequency exciting signal from a power source.
Abstract: A radio frequency excited carbon dioxide laser (50) is stabilized by sensing (66) variation in output power to generate a feedback signal (68,78 ) that is employed to vary amplitude of the radio frequency exciting signal from a power source (62). Frequency modulation of the laser output is achieved by varying the amplitude of the radio frequency signal from a power source (62) in response to a frequency modulating control signal from a modulation source (74). Both stabilization and frequency modulation are accomplished by combining the sensed power feedback signal with the frequency modulation control signal in a summing circuit (70) and employing the combined signal to vary magnitude of the radio frequency exciting signal.

22 citations


Proceedings ArticleDOI
06 Nov 1989
TL;DR: In this paper, a forward pulsewidth modulated zero-current switching quasi-resonant converter (F-PWM-ZCS-QRC) is proposed to provide output voltage and power control at a constant operating frequency.
Abstract: The authors propose a forward pulse-width modulated zero-current switching quasi-resonant converter (F-PWM-ZCS-QRC), which, in contrast to the conventional forward frequency-modulated zero-current switching quasi-resonant converter (F-FM-ZCS-QRC), provides output voltage and power control at a constant operating frequency. The topology is generated by inserting an additional current-bidirectional switch in the conventional F-FM-ZCS-QRC. The operation principle and design-oriented analysis are presented, with normalized design curves, design procedure, numerical examples, simulations, and experimental results. Theoretical analysis was verified experimentally with a prototype rated at 100 W, operating at the resonant frequency of 1.56 MHz and a switching frequency of 500 kHz. It has been experimentally demonstrated that the proposed converter operates from full load down to 2% of full load, with a constant switching frequency of 500 kHz. >

17 citations


Patent
Michael F. Gard1
13 Sep 1989
TL;DR: In this article, a modulator (14) and a demodulator (30) cooperate in a system (10) to communicate data at a high data rate using a PFM.
Abstract: A modulator (14) and a demodulator (30) cooperate in a system (10) to communicate data at a high data rate using a pulse frequency modulation scheme (PFM). The modulator (14) receives data symbols in a FIFO memory (72) and applies the data symbols, after an adjustable delay, to a variable frequency oscillator (74) to control the frequency of a carrier waveform (16) generated by the oscillator (74). Circuits (76, 78, 98) monitor the carrier waveform (16) and couple to the FIFO memory (72) to control the advancing of data to the oscillator (74). Consequently, the carrir waveform (16) is capable of changing frequency at each half-cycle of the carrier waveform (16), and such changes occur only at zero-crossings of the carrier waveform (16). The carrier waveform (16) is applied through a transmission channel (22) to the demodulator (30). The demodulator (30) includes a comparison circuit (36-42) which produces bipolar signals describing positive and negative half-cycles of the carrier waveform (16). These bipolar signals are de-glitched (96, 98) and applied to start and stop control inputs (52, 54) in respective positive and negative counter circuits (44p, 44n). Each of the counter circuits (44) includes a counter (58) which counts a high speed clock signal supplied by a clock generator (46) during one of the half-cycles to produce a period count that describes the duration of the half-cycle. During a subsequent half-cycle, a translation circuit (60) converts the period count into a amplitude value that describes the data symbol modulated onto the carrier waveform (16), and a resetting circuit (64-68) presets the counter (58) to an initial value.

17 citations


Patent
06 Mar 1989
TL;DR: In this paper, a continuous phase shift modulation (SPM) system is proposed, where, for each of the in-phase and quadrature components, adjacent half-cosine pulses of the same polarity are joined by a continuous transition modulation signal which maintains continuity of the waveform and at least its first derivative.
Abstract: A continuous phase shift modulation system wherein, for each of the in-phase and quadrature components, adjacent half-cosine pulses of the same polarity are joined by a continuous transition modulation signal which maintains continuity of the waveform and at least its first derivative When this occurs, the other component signal is adjusted to maintain constant the vector sum of the component signals

Patent
08 Sep 1989
TL;DR: In this paper, a two-wire line is used for digitizing and transmitting one or more analog signals simultaneously over a twowire line, where the analog signals are transmitted as the quiescent current of each analog coder module and its associated transducers connected to it.
Abstract: A method and apparatus for digitizing and transmitting one or more analog signals simultaneously over a two-wire line. The two-wire line not only provides the power required for the digitizing circuit and sensor, but is used also to transmit the analog information in a digital pulse train encoded with the power supply current. All data pulses are transmitted as the quiescent current of each analog coder module and its associated transducers connected to it. These data pulses start and end by transmission of a digital sync current pulse which separates transmission of each analog data pulse. The width of each data pulse conveys the desired information. A circuit for generating the pulse train having only two amplitudes but pulses having a variable width includes an SR flip-flop coupled to the output stage. The timing of the SR flip-flop being set and reset is determined by the analog data, thus providing an output pulse train having one of two amplitudes and a variable width, the width being proportional to the data conveyed within the pulse train. An analog zero voltage level width pulse and an analog high voltage level width pulse are transmitted in the same pulse train as the analog data to eliminate any temperature or component drifts in sensitive analog-sensing circuits. A formula is given to implement an auto calibration technique.

Patent
25 Jul 1989
TL;DR: In this paper, the intermodulation products of two low frequency signals superimposed upon the modulation signal are used to produce detected products which are separated into appropriate components and utilized to control the amplitude of modulation signal such that its logic 0 level occurs at a given optimum point.
Abstract: Control of the amplitude of data modulation applied to a laser diode is critical to prevent excessive wavelength shift and resultant dispersion of the signal in the waveguide at high data rates. The present invention utilizes the intermodulation products of two low frequency signals superimposed upon the modulation signal to produce detected products which are separated into appropriate components and utilized to control the amplitude of the modulation signal such that its logic 0 level occurs at a given optimum point. A further complementary and interacting control loop is utilized to control the bias point or center point for this data modulation signal.

Patent
15 Feb 1989
TL;DR: In this paper, a temperature controller utilizes a square wave signal whose pulse width is incrementally stepped in variable increments by a variable count in a register to determine the temperature being read by a sensor.
Abstract: A temperature controller utilizes a square wave signal whose pulse width is incrementally stepped in variable increments by a variable count in a register to determine the temperature being read by a sensor. The square wave signal is integrated to provide an analog signal that is compared to an analog signal provided by the sensor. When the amplitude of the integrated analog signal approaches the amplitude of the signal from the sensor, the count in the register is noted and the temperature is determined from the count by a piecewise linear equation. The temperature thus obtained is compared to a user selected temperature to control the temperature in the sensed area. The controller also includes a monitoring system that monitors the status of switching devices that are controlled by the controller to assure that the status of the switching devices corresponds to the status selected by the controller.

Patent
Mori Kunitaka1
31 Oct 1989
TL;DR: In this article, a decision circuit is provided for detecting when the pulses generated by the oscillator during an interval between pulses of the input pulse signal are equal to at least N to give an indication that a phase alignment is established between the input and output pulse signals.
Abstract: In a sync detection circuit, an input pulse signal at frequency f 0 is compared with an output pulse signal from a frequency divider to produce a control signal representative of a difference in frequency or phase between the input and output pulse signals. A voltage-controlled oscillator generates pulses at a frequency f 0 ×N (where N≧2) when the control signal indicates that the frequency or phase difference is zero or pulses at a variable frequency when the control signal indicates that the frequency or phase difference is non-zero. The frequency divider divides the frequency of the pulses from the oscillator by a factor N to generate the output pulse signal. A decision circuit is provided for detecting when the pulses generated by the oscillator during an interval between pulses of the input pulse signal are equal to at least N to give an indication that a phase alignment is established between the input and output pulse signals. If N is equal to or greater than 4, the decision circuit may comprise a frequency divider for dividing the frequency of the input pulse signal by a factor M (where M≧2) to define the count interval between successive pulses from the second frequency divider, so that phase alignment occurs when MN pulses of the input pulse signal exist between the counte interval.

Proceedings ArticleDOI
03 Apr 1989
TL;DR: In this article, an average model of the PWM controlled system, derived by an infinte sampling frequency assumption, is obtained by replacing the discontinuous FWM controller by a memoryless nonlinear controller completely specified by the feedback duty ratio function.
Abstract: In this article a design method is proposed for the specification of a variety of Pulse-Width-Modulation (PWM) feedback controllers acting on plants described by Nonlinear Dynamical Systems. It is shown that an average model of the PWM controlled system, derived by an infinte sampling frequency assumption, is simply obtained by replacing the discontinuous FWM controller by a memoryless nonlineariy completely specified by the feedback duty ratio function. The average model captures the essential qualitative stability properties of the controlled system and, thus, can be used to considerably simplify the PWM controller design task. The case of PWM regulators for linear plants can be systematically treated by traditional input-output design methods. Some examples are provided.

Proceedings Article
16 Oct 1989
TL;DR: The implementation uses pulse frequency modulation to achieve analogue input and output capability, and uses a pulse width modulation method to realise the synaptic multiplication component, which greatly reduces the silicon area required for the architecture.
Abstract: Neural networks that use digital or partly digital processing units have a restricted set of applications, and also are constrained by the set of learning rules that can be used with them. Analogue networks have a greater flexibility in their learning algorithms and a larger domain of problems which they can solve. The flexibility of an analogue output capability can also be used to give an idea of the certainty or accuracy of results. The design was fabricated using a 2 mu m CMOS fabrication process. This provides a relatively low cost, easily available medium for research and would allow easy fabrication of any products arriving from this research on industrial processes. The implementation uses pulse frequency modulation to achieve analogue input and output capability, and uses a pulse width modulation method to realise the synaptic multiplication component. This pulse coding technique reduces the size and complexity of the synaptic multiplier which has to be repeated for each neural connection in the network. This greatly reduces the silicon area required for the architecture.

Journal ArticleDOI
TL;DR: Ability of observers to discriminate whether the envelope of two amplitude-modulated sinusoids are in phase or out of phase is reported, which was relatively constant for modulation rates below 100 Hz and deteriorates for higher modulation rates.
Abstract: Measurements are reported on the ability of observers to discriminate whether the envelope of two amplitude‐modulated sinusoids are in phase or out of phase. Spacing between the two carriers was either 2/3 or 4/3 octave, and the depth of modulation was varied to determine threshold. Discrimination performance improved as the level of the carriers increases up to about 60 dB SPL. The frequency locus of the two carriers (geometric mean of the two frequencies), which varied from 500 to 8000 Hz in different experiments, had little effect on discrimination accuracy. Discrimination performance was relatively constant for modulation rates below 100 Hz and deteriorates for higher modulation rates. These results are compared with data obtained from comodulation masking release experiments.

18 Dec 1989
TL;DR: Recent theoretical developments relating specifically to the transmission of video signals of PWM are discussed in this paper along with a range of practical results and measurements.
Abstract: Pulse time modulation (PTM) techniques offer attractive performance trade-offs for the transmission of analogue data over optical fibre networks In particular, pulse width modulation (PWM) emerges as a bandwidth-efficient technique capable of supporting multiple video channels inexpensively Recent theoretical developments relating specifically to the transmission of video signals of PWM are discussed in this paper along with a range of practical results and measurements >


Patent
11 May 1989
TL;DR: In this paper, the input of a low pass filter is switched at high frequency between positive and negative supply voltages, and the switching is controlled by a comparator which is responsive to a composite of signals which include contributions from a sine wave control signal at the same frequency desired for the output and a square wave controller signal at a frequency substantially higher than the desired output frequency.
Abstract: In the sine wave inverter disclosed herein the input of a low pass filter is switched at high frequency between positive and negative supply voltages. The switching is controlled by a comparator which is responsive to a composite of signals which include contributions from a sine wave control signal at the same frequency desired for the output and a square wave control signal which is at a frequency substantially higher than the desired output frequency. The filter input voltage is attenuated and phase adjusted to generate a feedback signal having a high frequency component which is substantially in phase with the high frequency control signal. This feedback signal is combined with the sine wave and high frequency square wave control signals to generate the composite of signals which controls the comparator. Accordingly, the duty cycle of the filter input voltage is varied in correspondence with both the sine wave control signal and the loading of the inverter output.

Patent
12 Apr 1989
TL;DR: In this article, an improved circuit for controlling the output power level of a radio frequency (RF) amplifier is disclosed, which samples the output of an RF amplifier at a preselected modulation frequency and is passed to a detector.
Abstract: An improved circuit for controlling the output power level of a radio frequency (RF) amplifier is disclosed. The circuit samples the output of an RF amplifier. The sample is amplitude modulated at a preselected modulation frequency and is passed to a detector. In repsonse to the amplitude modulated signal, the detector produces a signal whose amplitude is indicative of the RF amplifier's output power and whose frequency is the modulation frequency. The amplitude of the signal produced by the detector is then compared to a reference amplitude and the difference (error signal) is used to control the gain of the RF amplifier.

Patent
15 Apr 1989
TL;DR: In this article, a modified quadrature amplitude modulation (QAM) method was proposed for phase modulation of a carrier with data signals, which is based on a modified QAM method which is composed of an amplitude modulation of the carrier and a double sideband modulation (DSB) rotated by 90 DEG.
Abstract: The invention relates to a method for digitally phase-modulating a carrier with data signals, which is based on a modified quadrature amplitude modulation method which is composed of an amplitude modulation (AM) of the carrier and a double-sideband modulation (DSB) rotated by 90 DEG . In this arrangement, the AM and the DSB are controlled in such a manner that the resultant indicator of the phase modulation maintains a constant length and the variation with time of the oscillation accurately corresponds with the modulating signal. The time functions of the AM and DSB signals are stored as reference values in EPROMs. The EPROMs are read out in dependence on the data to be transmitted in such a manner that a 90 DEG -rotation of the DSB signal compared with the AM signal is obtained. The data are shaped and band-limited by suitable selection of the reference values in the EPROM. The modulation occurs in each case in Ex-OR switched-mode modulators which are followed by a latching element and a digital/analog converter. The outputs of the two digital/analog converters are added to the desired phase modulation signal. Interference components are removed from the signal in a subsequent band-pass filter.

PatentDOI
TL;DR: In this paper, a difference signal is developed as a function of a difference between the current fundamental frequency and a known in-tune frequency associated with the selected string being tuned, which can then be used to visually display the difference whereby the selected one of the strings can be tuned to minimize the difference.
Abstract: An electronic tuner generates a pulse train signal from an analog signal transduced from vibrations on a selected one of several strings of a musical instrument. The pulse train signal has a plurality of successive pulses, each of the pulses having a pulse width which may vary between successive pulses. Two of the pulses have a longest pulse width of all pulses in the pulse string are identified. The tuner then computes a current fundamental frequency on the selected string as a function of a ratio between a numerical count of the pulses occurring between these two pulses, the count including one of these pulses, and a sum of the pulse width of each of the pulses included in the count. The two of the pulses have a longest pulse width of all pulses in the pulse string. A difference signal is developed as a function of a difference between the current fundamental frequency and a known in-tune frequency associated with the selected string being tuned. The difference signal may then be used to visually display the difference whereby the selected one of the strings can be tuned to minimize the difference.

Patent
28 Mar 1989
TL;DR: In this article, a first output signal is produced when a particular frequency component in one of the frequency bands is detected and a second output signal when a different frequency component, approximately equal to the difference between twice a predetermined frequency included in the other frequency bands and the particular frequency in the one frequency band, is detected.
Abstract: To detect whether an input FM signal, such as a reproduced video signal, which includes particular frequency components representing predetermined information, was recorded in a first or second mode, with the modes having different frequency bands, a first output signal is produced when a particular frequency component in one of the frequency bands is detected (23, 25) and a second output signal is produced when a different frequency component, approximately equal to the difference between twice a predetermined frequency included in the other of the frequency bands and the particular frequency in the one frequency band, is detected (24, 26). A mode identifying signal indicative of the frequency band occupied by the FM signal is produced (27) in response to the first and second output signals.

Proceedings ArticleDOI
01 Oct 1989
TL;DR: In this article, slope modulation is used as a means of voltage control in inverter circuits, where the mark and space intervals of the pulse-width modulation (PWM) waveform are generated by controlling the slopes of a triangular carrier waveform.
Abstract: Slope modulation is discussed as a means of voltage control in inverter circuits. The mark and space intervals of the pulse-width modulation (PWM) waveform are generated by controlling the slopes of a triangular carrier waveform. This slope modulation scheme, when implemented with a square-wave reference waveform and a constant volts/hertz ratio, produces a linear relationship between the fundamental frequency and the frequency ratio. The constant volts/hertz ratio is useful in such applications as variable-speed motor drives. The adopted three-phase PWM technique results in a constant current harmonic distortion at all frequencies. >

Patent
31 Oct 1989
TL;DR: A frequency response stabilized amplitude modulation circuit includes a variable gain amplitude modulator producing an output signal having an amplitude proportional to a product of amplitudes of input carrier, modulating and gain control signals as mentioned in this paper.
Abstract: A frequency response stabilized amplitude modulation circuit includes a variable gain amplitude modulator producing an output signal having an amplitude proportional to a product of amplitudes of input carrier, modulating and gain control signals An envelope detector generates a signal having an amplitude responsive to the modulation envelope of the output signal A first difference amplifier produces the modulating signal input to the amplitude modulator in proportion to a difference between amplitudes of the envelope detection signal and an audio input signal The modulating signal incorporates negative feedback to ensure the envelope amplitude of the modulated output signal tracks the audio input A second difference amplifier provides the gain control signal input for the amplitude modulator in accordance with a difference between amplitudes of the modulating signal, scaled by a constant factor, and the envelope detection signal The second difference amplifier minimizes influence of carrier signal frequency on modulation frequency response by accordingly adjusting the gain of the modulation circuit

Patent
24 Jan 1989
TL;DR: In this paper, the luminance signal of the widest frequency band out of component image signals at the pulse interval of a sampling value and alternately pulse-width modulating the color-difference signal of a half or below the illumination signal at the half period was used to attain an efficient transmission with one pulse string.
Abstract: PURPOSE:To attain an efficient transmission with one pulse string by loading the luminance signal of the widest frequency band out of component image signals at the pulse interval of a sampling value and alternately pulse-width- modulating the color-difference signal of the frequency band of a half or below the luminance signal at the half period. CONSTITUTION:By utilizing that respective color-difference signals of component image signals Y, CW and a half or below the frequency band of the luminance signal, the luminance signal out of the component image signals Y, CW and CN executes a pulse frequency modulation (PFM), and pulse-width-modulates (PWM) the pulse of this modulated PFM signal at a half period successively with the CW signal and CN signal. Thus, a high speed process is not required like a PCM multiplexed transmission and a pulse optical transmission can be executed with one emission element, further with the information of one pulse string irrespective of a linearity.

Patent
16 Mar 1989
TL;DR: In this article, the authors proposed to obtain large S/N while keeping a low distortion characteristic by combin ing a PFM modulation circuit applying pre-modulation by a small modulation and a pf modulation with a large modulation.
Abstract: PURPOSE:To obtain large S/N while keeping a low distortion characteristic by combin ing a PFM modulation circuit applying pre-modulation by a small modulation and a PFM modulation circuit applying pre-modulation with a large modulation. CONSTITUTION:An input signal 12 is converted into a pulse frequency modulation wave 13 by a 1st PFM modulation circuit 2. The modulation circuit 2 emphasizes a low distortion characteristic to apply pre-modulation by a small modulation. A pulse modulation wave 13 is converted into a pulse frequency modulation wave 14 by a 2nd PFM modulation circuit 3. The modulation circuit 3 emphasizes the S/N characteristic to apply pre-modulation by a large modulation. The modulation wave 14 is converted into an optical signal and sent to the optical fiber 6. On the other hand, the optical signal from the optical fiber 6 is converted into an electric signal at the reception side and its output 15 is modulated by the 2nd PFM demodulation circuit 9 corresponding to the 2nd PFM modulation circuit 3 and the signal is demodulated into the original signal by the 1st PFM demodulation circuit corresponding to the 1st PFM modulation circuit 2. Moreover, the 2nd PFM modulation circuit and the PFM demodulation circuit are replaced into FSK modulation and demodulation circuits.

Patent
04 Jan 1989
TL;DR: In this paper, a high frequency modulation circuit consisting of a first switching means, a modulation means and a second switching means is presented. And the present invention is capable of switching the modulation system in accordance with the television system of the receiver.
Abstract: A high frequency modulation circuit comprising a first switching means, a modulation means and a second switching means. The first switching means is composed of transistors for switching the modulation system in accordance with the television system, while the modulation circuit mixes said modulated wave and video signal and modulates the carrier and the second switching means is also composed of transistors for switching the modulation system of said modulation circuit in accordance with the television system. Accordingly the present invention is capable of switching the modulation system in accordance with the television system of the receiver.