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Showing papers on "Modulation published in 1970"


Patent
23 Oct 1970
TL;DR: In this paper, a communication system for providing effective multipath transmission without intermodulation or other distortion effects normally arising from the transmission through a dispersive medium, such as multipath troposcatter communication links, is described.
Abstract: A communication system for providing effective multipath transmission without intermodulation or other distortion effects normally arising from the transmission through a dispersive medium, such as multipath troposcatter communication links. In the invention the analog information is used to phase or amplitude modulate a transmitter signal and digital information is used to frequency and phase modulate such signal in a hybrid modulation process which is readily adapted to permit alternate analog and digital modulation, simultaneous analog and digital modulation, or sole analog or sole digital modulation over periodically occurring frame intervals of time. At the receiver the multipath signal is appropriately gated to select only those portions of the received signal which are the least affected by time delays introduced by the multipath transmission, such selected portions being demodulated to reconstruct the analog and digital information which has been transmitted.

77 citations


Journal ArticleDOI
TL;DR: Lower bounds on the average distortion produced by noise for a class of distortion functions are derived and relate the "smoothness" of modulation techniques to the minimum error that can be achieved with them.
Abstract: We consider the problem of transmission of analog data over a noisy channel. It is assumed that the channel input is of the form \surd S f(t, X) , where X is an n -dimensional source vector, and S is the allowable transmitted power. The performance of any given modulation scheme f(t, \cdot ) as a function of the transmitted power S is studied. Lower bounds on the average distortion produced by noise for a class of distortion functions are derived. These bounds relate the "smoothness" of modulation techniques to the minimum error that can be achieved with them. It is shown that when the analog source emits a sequence of mutually independent real random variables at a rate of R per second, the mean-square error that is associated with any practical modulation scheme f(t, \cdot) decays no faster than S^{-2} as the signal power S \rightarrow \infty . It follows that in the case of a band-limited additive white Gaussian channel no single modulation scheme f(t, \cdot ) can achieve the ideal rate-distortion bound on the mean-square error for all values of S , if the channel bandwidth is larger than the source rate R .

73 citations


Journal ArticleDOI
K. Kurokawa1, W.O. Schlosser
01 Jan 1970
TL;DR: In this paper, a quality factor of switching diodes for digital modulation is proposed, which is defined by Q^= √(r 1 - r 2 )2+ (x 1 - x 2 ) 2/√r 1 r 2 where r 1 + jx 1 and r 2+ jx 2 represent the diode impedances in the two switching states.
Abstract: A quality factor of switching diodes for digital modulation is proposed. It is defined by Q^= √(r 1 - r 2 )2+ (x 1 - x 2 )2/√r 1 r 2 where r 1 + jx 1 and r 2 + jx 2 represent the diode impedances in the two switching states. It is invariant to lossless transformations and permits direct computation of the loss produced by the diode in a given switching circuit.

50 citations


Journal ArticleDOI
TL;DR: In this paper, the Van der Pol equation was used to explain the suppression and synchronization of electron oscillations in a beam-plasma system with self-oscillator models.
Abstract: Standing waves of longitudinal electron oscillation were observed in a beam-plasma system. By applying a density modulation to the beam, the amplitude of oscillation decreased to zero when the modulation frequency was near to those of the spontaneous oscillation. The modulation depth necessary for the oscillation to vanish was nearly proportional to the difference between the oscillation frequency and the modulation one. When the oscillation was suppressed, the oscillation having the same frequency as the modulation one was excited. These suppression and synchronization can be well explained by the assumption that the oscillation of electron density is described by the Van der Pol equation. Under this self-oscillator model the linear growth rate is evaluated and compared with the value calculated from the dispersion equation of the two-stream instability.

45 citations


Journal ArticleDOI
TL;DR: An algorithm for adjusting the tap gains of a tapped delay line (TDL) equalizer which converges for all channels to the setting, which minimizes the mean-square error at the filter output due to both noise and intersymbol interference is described.
Abstract: Results are reported which are of interest in the automatic adaptive equalization of telephone lines or other narrowbandwidth channels where data transmission is limited primarily by intersymbol interference. We describe an algorithm for adjusting the tap gains of a tapped delay line (TDL) equalizer which converges for all channels to the setting, which minimizes the mean-square error (rose) at the filter output due to both noise and intersymbol interference. This algorithm has been implemented using digital microcircuits and metal-oxide semiconductor (MOS) shift registers to construct a 63 tap all-digital TDL filter covering 19.7 ms. The modulation system used is vestigal sideband with bandwidth 1.6 kHz. The data rate is 3200 pulses/s, or 9600 bit/s with 8 data levels. A description of the hardware realization and performance data over various telephone lines is given.

45 citations


Book
01 Jan 1970
TL;DR: Information transmission, modulation, and noise: a unified approach to communication systems, Information transmission, Modulation, and Noise: a unification of communication systems.
Abstract: Information transmission, modulation, and noise: a unified approach to communication systems , Information transmission, modulation, and noise: a unified approach to communication systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

40 citations


Patent
Bertram J. Goldstone1
05 Oct 1970
TL;DR: In this paper, a pulse compression radar system was proposed, where a coding signal indicative of the modulation to be impressed on a transmitted signal is read out of a read only memory and converted to: (a) an analog modulation signal on a radio frequency carrier; and (b) the complex conjugate of the discrete Fourier transform of the coding signal stored in a memory.
Abstract: A pulse compression radar system wherein a coding signal indicative of the modulation to be impressed on a transmitted signal is read out of a read only memory and converted to: (a) an analog modulation signal impressed on a radio frequency carrier; and (b) the complex conjugate of the discrete Fourier transform of the coding signal stored in a memory. Each echo signal resulting from illumination of a different target by the modulated transmitted signal is converted to a corresponding digital form indicative of the modulation on each such echo signal, transformed in a discrete Fourier transform and correlated with the stored complex conjugate of the coding signal for the transmitted signal. The resulting correlation signal is weighted and then converted back to a time varying signal in an inverse discrete Fourier transform for utilization.

31 citations


Journal ArticleDOI
TL;DR: The power spectral density of a modulated Poisson point process is derived, the results showing that modulation of the rate of the process introduces power only at those frequencies contained in the modulation, unlike the case of very “regular” carriers.
Abstract: The power spectral density of a modulated Poisson point process is derived, the results showing that modulation of the rate of the process introduces power only at those frequencies contained in the modulation, unlike the case of very “regular” carriers.

23 citations


Patent
Darrel B1, Weichbrodt B1
30 Oct 1970
TL;DR: In this paper, a distributed defect in one of a pair of meshing gears produces a modulation in amplitude of the component of the vibration signal which has the same repetition rate as the meshing frequency of the gears.
Abstract: A distributed defect in one of a pair of meshing gears produces a modulation in amplitude of the component of the vibration signal which has the same repetition rate as the meshing frequency of the gears. The modulation has a frequency corresponding to the period of rotation of the gear with the distributed effect or a submultiple thereof. Detection of the modulation provides an indication of the existence, character and extent of the defect.

22 citations


Proceedings ArticleDOI
W. J. Clemetson1, N. D. Kenyon, K. Kurokawa, W. O. Schlosser, B. Owen 
01 Jan 1970
TL;DR: In this paper, a PIN diode modulator with approximately 1.2dB insertion loss at 56.4 GHz and 0.7 ns switching time was described for high-speed binary phase shift modulation of a millimeter wave carrier.
Abstract: High-speed binary phase-shift modulation of a millimeter wave carrier can be obtained by path-length switching. A PIN diode modulator with approximately 1.2-dB insertion loss at 56.4 GHz and 0.7 ns switching time will be described.

21 citations


Journal ArticleDOI
01 Oct 1970
TL;DR: In this article, the performance of short-pulse optical communications at high data rates (2 × 108 bit/s) with binary modulation formats was evaluated using a sub-nanosecond internally gated receiver.
Abstract: Experiments in short-pulse optical communications have been performed at high data rates (107bit/s) with M-ary modulation formats and, using a subnanosecond internally gated receiver, at very high data rates (2 × 108bit/s) with binary modulation formats to experimentally verify the potential of short-pulse low-duty-cycle direct-detection formats. High resolution TV pictures and error rate data are given for two M-ary formats, pulse interval modulation and pulse position modulation, and error rate data and gated optical receiver characteristics are given for the 200-Mbit/s pulsed gated binary modulation. Results demonstrate the capability of short-pulse laser-communication systems to discriminate against background light and to efficiently convey information. Subnanosecond gating of the receiver was achieved in the 200-Mbit/s experiments. In the M-ary experiments, as many as 12 bit/pulses were transmitted, using 4095 digitally selected 1 -ns time slots. High-quality TV pictures were transmitted at average detected signal to background ratios of less than 0.01.

Journal ArticleDOI
TL;DR: In this article, a high-energy electron traverses a thin dielectric film guiding a laser beam, it is partially scattered by the electromagnetic field, and the scattered wave function and the probability amplitude then carry optical information as time and spatial modulation.
Abstract: When a high‐energy electron traverses a thin dielectric film guiding a laser beam, it is partially scattered by the electromagnetic field. The scattered wave function and the probability amplitude then carry optical information as time and spatial modulation. This effect, rather than classical bunching of electrons, is proposed as the modulation mechanism in the Schwarz‐Hora experiment.

Patent
09 Jul 1970
TL;DR: In this article, a train of pulses used to control a servo-motor is modulated in accordance with the values of a varying digital input signal, which is divided into two components; a first group of bits representing integer order values; and a second group of bit representing fractional order data.
Abstract: As described herein, a train of pulses used to control a servo-motor is modulated in accordance with the values of a varying digital input signal. To obtain accuracy of control, the digital input signal is divided into two components; a first group of bits representing integer order values; and a second group of bits representing fractional order data. A modulating circuit responds to the integer order bits to width modulate the pulse train in accordance with the magnitude represented by the integer order bits. The fractional order data bits are accumulated until the sum thereof at least equals the value of the least significant bit of the integer order component. At this time, the sum signal is added to the integer order data to add an increment of width modulation to the pulse then being modulated.

Patent
Carl Ferdinand Kurth1
08 Jun 1970
TL;DR: In this article, a frequency division multiplex single-sideband modulation system using a multiplexed digital filter, the passband of which is sequentially shifted from one multiplex-ed channel to another in synchronization with an input time-division multiplex commutator and a frequency multiplexer modulator.
Abstract: A frequency division multiplex single-sideband modulation system uses a multiplexed digital filter, the passband of which is sequentially shifted from one multiplexed channel to another in synchronization with an input time division multiplex commutator and a frequency multiplexer modulator. In other embodiments of the invention selected spectral components are advantageously emphasized by signal processing techniques employing repetitive sampling prior to modulation and filtering.

Journal ArticleDOI
TL;DR: The application of a binary transversal filter as transmitting filter and a digital circuit as modulator makes it possible to construct data transmitters consisting only of transistors and resistors.
Abstract: The application of a binary transversal filter as transmitting filter and a digital circuit as modulator makes it possible to construct data transmitters consisting only of transistors and resistors. The modulation distortion, caused by the keying of a low-frequency square-wave carrier, can be compensated by a modification of the transfer function of the transmitting filter, provided the carder frequency is chosen to be a multiple of half the bit rate. This principle makes it possible to realize the whole data transmitter in one single integrated circuit. The binary transversal filter, provided with an analog-to-digital converter, can also be used to construct the data receiver for the greater part with digital circuitry.

Patent
07 Dec 1970
TL;DR: In this paper, a differential phase shift keying modulating system is described, comprising two balanced modulators, one fed with a carrier frequency and the other fed with the carrier frequency phase shifted by 90 DEG.
Abstract: A differential phase shift keying modulating system is described, comprising two balanced modulators, one fed with a carrier frequency and the other fed with the carrier frequency phase shifted by 90 DEG . Modulating signals, respectively produced by a ring counter driving cosine and sine weighting circuits, are respectively fed to the two balanced modulators. Since the modulator signals have a sine/cosine relationship, the resultant output of the balanced modulators has a constant amplitude and a progressively increasing phase. Data is transmitted by causing the ring counter to count up or down, according to the value of data, so as to alter the direction of phase change of the output vector, and by varying the total number of stepping pulses applied to the counter during a given period, so as to vary the extent of the phase change during that period.

Journal ArticleDOI
G. White1
01 Oct 1970
TL;DR: In this article, an optical communications system is described which is capable of transmission and detection of 1-Gbċs-1pulse-code modulation (PCM) word patterns.
Abstract: An optical communications system is described which is capable of transmission and detection of 1-Gbċs-1pulse-code modulation (PCM) word patterns. Modulation of an argon laser beam is obtained with a lithium tantalate (LiTaO 3 ) modulator rod using a traveling-wave interaction. The high-speed electrical modulation signal is obtained by a multiplexing of four separate information channels.

Journal ArticleDOI
TL;DR: The history, raison d'être, theory, method of measurement, and accuracy and precision of the threshold modulation curve for photographic film are dealt with.
Abstract: This paper describes studies of the threshold modulation curve for photographic film. The threshold modulation curve is an empirically derived relation showing the need at any spatial frequency for modulation in the aerial image of a tribar for resolution to be achieved. The paper deals with the history, raison d'etre, theory, method of measurement, and accuracy and precision of the threshold modulation curve. The statistical aspects of the threshold modulation curve are emphasized, and the influence of factors that cause variations in the curve are examined. Examples are given of current and potential applications of the threshold modulation curve.

Patent
03 Jun 1970
TL;DR: In this article, the authors proposed the use of a bias bias signal with respect to the high frequency band component to compensate for the level variations of the high-frequency band component.
Abstract: A tape recorder has the capability of recording a predetermined band width of signals which is not as wide as a TV band width. To record a TV band, the signals are divided into high and low component band. The high frequency band component is recorded directly on the recording medium, and the low frequency band component is frequency modulated on a carrier wave with an index of modulation which is over unity. The lower frequency limit of the deviated carrier wave is substantially equal to or higher than the highest frequency component of the wide-band signal. The frequency modulated carrier wave is recorded on the recording medium at a level at which it acts as a bias signal with respect to the high frequency band component. The original wide-band signal is reproduced from the recording medium during playback when the component bands are separated, demodulated, and recombined. The high frequency band component played back from the recording medium is controlled by other frequency component played back at the same time so that the level variations of the high frequency band component is corrected.

Patent
04 Jun 1970
TL;DR: In this article, a receiver for the reception of information pulse signals transmitted by means of n-phase modulation was proposed, where the original information pulses coincide with different pulses from a series of equidistant clock pulses, and the receiver including an nphase demodulator which is provided with a plurality of parallel arranged synchronous demodulators which are fed by carriers having mutually different reference phases originating from a local carrier generator which is stabilised in phase on the carrier associated with the received signals.
Abstract: The invention relates to a receiver for the reception of information pulse signals transmitted by means of n-phase modulation wherein the original information pulses coincide with different pulses from a series of equidistant clock pulses, the receiver including an n-phase demodulator which is provided with a plurality of parallel arranged synchronous demodulators which are fed by carriers having mutually different reference phases originating from a local carrier generator which is stabilised in phase on the carrier associated with the received signals, signal channels being connected to the outputs of the n-phase demodulator including sampling circuits controlled by a local clock pulse generator the output signal of which sampling circuits characterizes the phase of the received carrier relative to the relevant reference phase of the local carrier at the instants of the local clock pulses, the receiver furthermore being provided with combination circuits connected to the sampling circuits, which combination circuits characterize each of the n-possible phase sectors of the transmitted signals in a phase diagram by means of a separate combination of the outputs of the signal channels. Such receivers are advantageously used in transmission systems which transmit an optimum quantity of information in the available frequency band. To stabilise the local carrier generator on the carrier at the transmitter end, the carrier frequency is transmitted, for example, in conventional manner from the transmitter to the receiver through a separate transmission path or with the aid of a pilot signal added to the information pulse signals to be transmitted.

Patent
24 Feb 1970
TL;DR: In this paper, a phase synchronization and measurement technique that compensates for the phase shifts introduced from the MSK modulation scheme is proposed. But the phase changes caused by propagation effects are determinable.
Abstract: Apparatus for measuring the phase of an unsynchronized but phase continuous and stabilized Minimum Shift Keyed (MSK) signal by monitoring the data channels of an MDK data communication system. This is accomplished by a phase synchronization and measurement technique that compensates for the phase shifts introduced from the MSK modulation scheme. Thus, time-varying phase changes caused by propagation effects are determinable.

Journal ArticleDOI
TL;DR: The combination of amplitude modulation of the nuclear rf power at a frequency f 1 and 180° modulation of the phase of the resonance microwave signal with respect to the reference microwave signal at frequency f 2, where f 1≫f 2, with successive amplification and phase sensitive detection at the two frequencies, has proved useful in electron nuclear double resonance (ENDOR) of unordered solids as mentioned in this paper.
Abstract: The combination of amplitude modulation of the nuclear rf power at a frequency f1 and 180° modulation of the phase of the resonance microwave signal with respect to the reference microwave signal at a frequency f2, where f1≫f2, with successive amplification and phase sensitive detection at the two frequencies, has proved useful in electron‐nuclear double resonance (ENDOR) of unordered solids. The alternative of amplitude modulation alone often results in poor baseline stability, and the alternative of amplitude modulation plus magnetic field modulation results in the complication of summing in an uncontrolled manner ENDOR contributions from crystallites resonating at different fields and with different orientations with respect to the applied dc magnetic field.


Patent
30 Mar 1970
TL;DR: In this article, a modulated alternating waveform produced by an oscillator is transmitted to a target and a receiver receives reflections of the waveform from the target, which is applied through a voltage controlled phase shifter and squaring amplifier to a synchronous detector coupled to the receiver.
Abstract: A modulated alternating waveform produced by an oscillator is transmitted to a target and a receiver receives reflections of the waveform from the target. The waveform of the modulation also is applied through a voltage controlled phase shifter and squaring amplifier to a synchronous detector coupled to the receiver. In the synchronous detector, the signal and any spurious noise from the receiver is multiplied by the waveform from the squaring amplifier in a manner that cancels out all spurious noise. A DC voltage representative of the phase shift produced in the modulation of the received signal by the distance from transmitter to target to receiver is applied to an integrator. Integrator output is applied to the voltage controlled phase shifter and is representative of the distance traveled by the waveform.

Patent
28 Dec 1970
TL;DR: In this article, a single frequency laser oscillation is realized by including within the laser cavity a resonant etalon, tuned to the desired laser frequency, which has the effect of suppressing all other modes while permitting the laser to oscillate at the desired single frequency.
Abstract: Single frequency laser oscillation is realized by including within the laser cavity a resonant etalon, tuned to the desired laser frequency. This has the effect of suppressing all other modes while permitting the laser to oscillate at the desired single frequency. In addition, the etalon tuning is frequency modulated about the desired frequency, producing an amplitude modulation of the laser signal. The amplitude modulation thus produced is sensed by a phase detector which generates an error signal whenever the laser frequency tends to deviate from the mean, etalon frequency. The error signal is used, in turn, to retune the laser cavity. It is an advantage of the present arrangement that spurious frequency modulation of the laser frequency, introduced by the stabilization system, is substantially less than that produced by comparable prior art stabilization circuits. Furthermore, such modulation can be conveniently reduced, or eliminated, by the addition of a dummy etalon driven in antiphase to the active etalon.


Patent
01 May 1970
TL;DR: In this article, the modulation of a radio signal transmitted from a satellite is correlated with a similar waveform generated by a stable oscillator at the receiver, and a change in phase is used as a measure of the distance travelled by the transmitted signal.
Abstract: The modulation of a radio signal transmitted from a satellite is correlated with a similar waveform generated by a stable oscillator at the receiver. The phase of the latter is varied in a direction to correlate it with the transmitted modulation, and a change in phase is used as a measure of the distance travelled by the transmitted signal. If the transmitted carrier is momentarily not received, the phase of the receiver waveform is not changed until communication is restored, and thereupon phase lock is restored and the phase change determined for the distance measurement.

Patent
04 May 1970
TL;DR: In this paper, a continuous-wave cyanide (HCN) laser has been employed to drive a continuous, traveling-wave lithium niobate (LiNbO3) electrooptic modulator at signal frequencies of 964 gHz.
Abstract: A continuous-wave cyanide (HCN) laser has been employed to drive a continuous, traveling-wave lithium niobate (LiNbO3) electrooptic modulator at signal frequencies of 964 gHz. (311 Mu m.) and at 891 gHz. (337 Mu m.). Part of the power of a visible 0.633- Mu m. carrier beam is converted into two visible sidebands, one of which is favored by the choice of phasematching angle. In a submillimeter communication system and in power metering of submillimeter radiation, angular separation of the beams makes attractive the up-conversion to the visible region, followed by detection. The large frequency separation of the visible carrier and the sidebands facilitates precision spectroscopic and metrological applications.

Patent
30 Dec 1970
TL;DR: In this article, a method and apparatus for the transmission and reception of signals in separate communication channels by imposing modulation upon only that portion of a transmission carrier wave which lies above the average value, or only upon that portion which lies below the average values, or upon both portions independently but simultaneously, and then demodulating the two halves of the resulting signal envelope separately at the receiving end.
Abstract: A method and apparatus for the transmission and reception of signals in separate communication channels by imposing modulation upon only that portion of a transmission carrier wave which lies above the average value, or only upon that portion which lies below the average value, or upon both portions independently but simultaneously, and then demodulating the two halves of the resulting signal envelope separately at the receiving end. The result of this technique is the creation of two channels selectable by polarity only. Transmission of the signal envelope from the transmitter to the receiver is accomplished by induction. Since the signal envelope is polarity modulated, the separate signal pulses may be amplitude and width modulated for transmission of complex information. Additional channels can, of course, be produced by combining the two basic channels.

Journal ArticleDOI
J. Salz1
TL;DR: The efficiency as measured by data rate per unit bandwidth of certain digital modulation systems is compared and the optimum detector is treated, indicating very minor differences m efficiency attained by the two different models analyzed.
Abstract: The efficiency as measured by data rate per unit bandwidth of certain digital modulation systems is compared. The systems considered are frequency modulation (FM), phase modulation (PM), and linear modulation. The achievable bits per cycle in digital PM and amplitude modulation (AM) at a given signal-to-noise ratio and error rate have been known for some time. In digital FM this quantity can be maximized, a fact apparently first realized by J. R. Pierce at Bell Telephone Laboratories. Rigorous optimizations were later carried out by Mazo, Rowe, and the author. In addition to the comparisons made with other systems, additional details related to the optimization problem in frequency-shift keying (FSK) are also furnished. Whereas previous treatments analyzed a frequency discrimination system, this paper treats the optimum detector. The results indicate very minor differences m efficiency attained by the two different models analyzed. Results are exhibited graphically, showing the relationships between the important system parameters.