Showing papers on "Sampling (signal processing) published in 1974"

Broadcast signal identification system

Abstract: A process for automatic electronic recognition and identification of programs and commercial advertisements broadcast on television and radio wherein a digitally sampled reference signal segment derived from either the audio or video portion of the original program content to be identified is compared with successive digitally sampled segments of the corresonding audio or video portion of a broadcast signal in a correlation process to produce a correlation function signal. The sampling rates and the time duration of the reference signal segment and the broadcast signal segments are the same. When the signal segments which are compared are the same, the correlation function signal is relatively large and a recognition thereof is achieved when such correlation function signal exceeds a selected threshold level. The compared signal segments may also be obtained as low frequency signals derived from the original reference and broadcast signals by non-linear and envelope formation processing techniques.

Statistical Properties of Timing Jitter in a PAM Timing Recovery Scheme

Abstract: A new technique is presented for evaluating the performance of a popular type of timing recovery circuit for baseband synchronous pulse amplitude modulation (PAM) data signals. The timing circuit consists of a square-law device followed by a narrowband filter tuned to the pulse repetition frequency along with provision for reshaping the pulses entering the timing path (prefiltering). The output of the timing circuit is a nearly sinusoidal timing wave whose zero crossings indicate the appropriate sampling instants for demodulation of the PAM signal. For a random data sequence, the timing wave exhibits phase fluctuations which are strongly dependent on the pulse shapes entering the timing path and the passband shape of the narrow-band filter. Expressions for rms phase fluctuation in the timing wave as a function of the prefiltering and postfiltering characteristics of the filters preceding and following the square-law device are presented. These expressions have a form which is especially suitable for studying the case where the baseband PAM signal is band-limited to frequencies less than the pulse repetition frequency. A condition on prefiltering and postfiltering which gives error-free timing recovery is presented. Results obtained from some specific examples serve to illustrate several aspects of the timing recovery problem.

Discrete Time Analyses of Nonuniform Sampling First- and Second-Order Digital Phase Lock Loops

Abstract: The present paper considers discrete time analyses of firstand second-order digital phase lock loops. These loops are characterized by the fact that they track the zero crossings of the incoming signal; consequently, the sampling intervals are nonuniform. The firstorder loop is analyzed for phase step and frequency step inputs; mean time to skip cycle is also considered. For phase step input, approximate expressions are obtained for the steady-state phase error probability density and phase error variance, the second of which leads directly to a theoretical prediction of threshold. The second-order loop is analyzed for frequency step input. Approximate expressions for the steady-state phase error probability density, phase error variance, and a theoretical prediction of threshold are obtained. The analyses are confirmed by numerical results and simulation.

The optimum comb method of pitch period analysis of continuous digitized speech

Abstract: A new method of tracking the fundamental frequency of voiced speech is described. The method is shown to be of similar accuracy as the Cepstrum technique. Since the method involves only additions, no multiplication, it is shown to be faster than the SIFT algorithm. The basis of the method is searching for a minimum in the magnitude of the difference between a speech segment and a delayed speech segment. This is shown to be equivalent to selecting the comb filter which best annihilates the input signal.

Predicting coherent sidelobe canceller

Abstract: A system for instrumenting time sampled predicting interference suppression, particularly in a side-lobe canceller system. Main and auxiliary channel signals are supplied to a canceller loop where correlating weights are sampled just prior to a radar pulse transmission on command of a radar pretrigger pulse. A sampling circuit stores both current and past weights and combines the current weight with the integral of the difference between the current and past weight to form predicting weights over each pulse repetition period. The predicting weights are used to form a translating signal for operating on the auxiliary channel interference signal so that it will cancel the interference in the main channel. By sampling just prior to radar pulse transmission and forming the predicting weights, cross modulation of clutter and antenna scan error can be reduced in order that a side-lobe canceller may be used compatibly with Moving Target Indicators.

Nickel-cadmium battery monitor

Abstract: The nickel-cadmium battery monitor is provided with sensors for measuring the battery temperature, the battery voltage and the magnitude of the current being charged to the battery, each of the sensors generating a sensor signal voltage that varies directly with the magnitude of the parameter being measured. The sensor signal voltages from the temperature sensor and the voltage sensor are conditioned and then converted to an analog signal voltage increment the magnitude of which corresponds approximately to the actual magnitude of the battery temperature and battery voltage as measured. The analog signal voltage increments thus obtained cause an analog visual display means to indicate visually the approximate magnitude of the battery temperature and battery voltage as measured. The conditioned analog signal voltages from the temperature sensor and the voltage sensor are also converted to a multibit digital signal which causes a digital visual display means to display in numeric form the actual magnitude of the battery temperature or battery voltage as measured. Charge rate sampling means continuously measures the magnitude of successive samples of the charge current and transmits an alarm signal to a flash alarm means when the rate of increase in the charge current exceeds a predetermined value. The flash alarm means transmits flash alarm signal to the digital visual display means when the temperature of the battery exceeds a predetermined value or when the voltage of the battery falls below or exceeds a predetermined value or when the charge rate sampling means transmits an alarm signal to the flash alarm means.

Adaptive Delta Modulation with Delayed Decision

Abstract: A class of adaptive schemes for delta modulation is considered whereby the decision about step size is a function of the present and the last k symbols. Such schemes are studied by computer simulations using speech-like signals through evaluation of SNR. Occasional large overshoots appear in the reconstructed signal after the integrater, and to avoid such events it is proposed to store a few signal samples and decide on the proper bit stream taking into account the adaptive logic. Two quadratic criteria have been tried, and improvements of a few decibels have been established with six stored signal samples and a sampling rate of 48 and 24 kHz. Results indicate that other criteria functions may achieve still higher values of SNR.

Signal processing and reproducing method and apparatus for single video frame reproduction with associated audio

Abstract: A method and system for processing low rate signals, such as audio frequency signals, wherein the low rate signals are converted to high rate signals by sampling at a predetermined rate sufficient to retain the intelligence in the low rate signals and recording the sample signals at predetermined locations on a track of a high rate recording media by repeated passes over the track for a predetermined number of cycles. Reproduction is effected by sampling the track at the predetermined locations at the predetermined rate and demodulating to obtain the original intelligence. High frequency signals, such as video frequency signals, may also be recorded on the recording media in correlation with the low frequency signals.

Protective relaying system

Abstract: Protection of an electric power system is attained under control of a digital computer. Voltage and current of the electric power system to be protected are subjected to sampling at a predetermined sampling frequency and are applied to the computer after being converted into digital signals. The computer computes the product of these two digital signal inputs. The signal thus obtained is added to a preceding signal representing the product of voltage and current taken at time before a predetermined period of time so that unnecessary frequency components included in these signals can be removed. Then, the level of the resultant signal (which is free from the unnecessary frequency components) is compared with the level of a reference signal. When the former is greater than the latter, there is a fault in the electric power system, and necessary protective measures are taken to protect the electric power system.

Statistical Properties of Timing Jitter in a PAM Timing Recovery Scheme

Abstract: A new technique is presented for evaluating the per- formince of a popular type of timing recovery circuit for baseband synchronous pulse amplitude modulation (PAM) data signals. The timing circuit consists of a square-law device followed by a narrow- band filter tuned to the pulse repetition frequency along with pro- vision for reshaping the pulses entering the timing path @refiltering). The output of the timing, circuit is a nearly sinusoidal timing wave whose zero crossings indicate the appropriate sampling instants for demodulation of the PAM signal. For a random data sequence, the timing wave exhibits phase fluctiations which are strongly de- pendent on the pulse shapes entering the timing path and the pass- band shape of the narrow-band filter. Expressions for rms phase fluctuation in the timing wave as a function of the prefiltering and postfiltering characteristics of the filters preceding and following the square-law device are presented. These expressions have a form which is, especially .-. suitable for studying the case where the-kas+d , tion frequency., A condition on prefiltering and postfiltering which gives error-free timing recovery is, presented. Results obtained from some specific examples serve to illustrate several aspects of the timing recovery problem. -_-_- PAM signal is band-limited to freciuencics l&stliah tliepulse repeti- . 4- -

Coupled design of test signals, sampling intervals, and filters for system identification

Abstract: This paper discusses the problem of optimal design of experimental conditions for linear system identification. It is demonstrated that, in general, to achieve maximal return from an experiment, coupled design of all the experimental conditions, namely the test signal, sampling intervals and filters, should be carried out simultaneously. For the case of uniform sampling it is shown that joint design of the presampling filter, sampling rate and input can be carded out in the frequency domain. For the case of nonuniform sampling a sequential design procedure is developed which optimizes the information increment between samples.

MTI compatible coherent sidelobe canceller

Abstract: A system for instrumenting time sampled interference suppression, particuly in a side-lobe canceller system. Interference signals are sampled just before a radar transmits on command of a sample gate or radar pulse, with main and auxiliary channel signals being delayed by the time between two successive samples. The two samples are then combined to allow interpolation such that weighting functions can be formed to adjust the delayed auxiliary signal so that interference in the delayed main channel signal can be suppressed at all times. By sampling just prior to radar transmission and interpolating between samples, cross modulation of clutter, and antenna scan error can be reduced in order that a side-lobe canceller system may be used compatibly with Moving Target Indicators (MTI).

Apparatus for digitally encoding a television signal

Abstract: An apparatus and method for digitally encoding an NTSC color television signal in a manner that facilitates comb filtering of the digitally encoded signal. In accordance with the invention there is provided a means for generating a first sampling signal having a characteristic frequency of three times the NTSC color subcarrier signal. Another means is provided for generating a second sampling signal having the same characteristic frequency, this second sampling signal having its sampling reference points interspersed equally in time between the sampling reference points of the first sampling signal. Enabling means, responsive to the NTSC color television signal, are provided for alternately enabling the first and second sampling signals during successive horizontal scanlines of the television signal. Further provided is a means, responsive to the enabled sampling signal, for sampling the television signal. Finally, means are provided for converting the sampled television signal into digital form. In a preferred embodiment of the invention, the first and second sampling signals are opposite phases of a square wave at 10.74 MHz.

Multiple parameter monitoring and readout system with sampling of parameters of higher priority than the highest parameter which is out of tolerance

Abstract: Apparatus for monitoring and indicating parameter conditions within a system. Signals are generated by sensors which monitor parameter state. The signals are sensed via a multiplexing scheme, each signal being compared to an individually programmed reference. Should a parameter signal exceed the reference, a corresponding indicator is activated. Each parameter is prioritized such that a parameter signal which exceeds its reference will cause the multiplex network to sequentially sense only that parameter and all other parameters of a higher priority. Further refinements allow the readout of the value of a parameter signal if the parameter exceeds its reference or if such readout is manually selected.

Synchronization method for the recovery of binary signals

Abstract: A synchronization method for the recovery, at the receiver side of an information transmission equipment, of bit timing information during the transmission of a binary signal which at the transmitter side of the equipment is converted into a multilever signal with correlative properties. From such multilevel signal, a binary signal conforming with the original binary signal is reconstructed at the receiver side. Bit timing information for sampling purposes at the receiver side is obtained by detection of the times at which the multilevel signal reaches and/or leaves at least one specific level.

On statistics of time‐to‐amplitude converter systems in photon counting devices

Abstract: Applying methods of statistics to photon counting in measuring a simple exponential decay with a time‐to‐amplitude converter and multichannel analyzer device shows that the histogram obtained is distorted due to the process of signal sampling. The distortion depends on count rate and life time. The distortion is biggest in the initial part of the histogram, whereas at times much greater than the decay time the histogram shows the real decay curve.

Apparatus and method for synchronizing a digital modem using a random multilevel data signal

Abstract: An automatic digital modem receiving an input analog signal samples the input signal to provide a random multilevel data signal. This multilevel signal is equalized and phase corrected so that the characteristics of the modem are substantially synchronized with the characteristics of the input analog signal. A system error signal which is responsive to the random multilevel data signal is averaged to provide a synchronization quality signal. When the synchronization quality signal degrades to a predetermined magnitude, a restart signal adjusts the sampling, the equalization, and the phase correction of the modem to reduce the magnitude of the synchronization quality signal. The associated method includes the steps of adjusting only the phase correction of the modem for a particular interval of time and then jumping the sampling of the modem if the synchronization quality signal has not been reduced below the first predetermined magnitude.

Aircraft altitude control system

Abstract: System for sampling and holding an analog signal corresponding to the altitude of an aircraft and providing a control signal for maintaining the aircraft at the altitude where sampling occurs. A binary converter stores a count corresponding to the level of the sampled signal, and a digital-to-analog counter provides an output analog signal corresponding to the count registered by the counter. The altitude signal is compared with the output signal to provide an altitude correction signal in the event that the altitude signal deviates from the level corresponding to the stored count.

Design of a Digital Controller for Spinning Flexible Spacecraft

Abstract: An approach to digital control system design is applied to the analysis and design of a practical onboard digital attitude control system for a class of spinning vehicles characterized by a rigid body and two connected flexible appendages. The approach used is to design a continuous-data control system that will provide a satisfactory system response. Then, using the digital redesign method, a digital controller with onboard digital computer is designed to provide a digital control system whose states are similar to those of the continuous system at sampling instants. The simplicity of application of this approach is indicated by example. The example, using spinning Skylab parameters, is used to substantiate the conclusions.

Yarn runner-length controller for knitting machines

Abstract: A yarn runner-length controller for warp beam knitting machines utilizes information of the yarn unwinding rate from a warp beam section and continuously compares this information to a signal related to the desired runner-length of the yarn This continuous comparison yields an error signal with a magnitude proportional to the difference between the desired runner-length and the actual runner-length The error signal is sampled and this sampled error signal activates a control device operating on the angular velocity of the warp beam section so as to adjust this velocity in the direction that reduces the difference between the actual runner-length and the desired runner-length The magnitude of the sampled error signal is reduced to zero before the next sampled error signal is received by means of a signal from the control device related to the amount of adjustment made to the beam section's angular velocity When the sampled error signal is reduced to zero, the control device maintains the beam section's angular velocity to the last adjusted value The continued sampling of the error signal thus maintains the actual runner-length to within close tolerances of the desired runner-length throughout the duration of the knitting process An error display panel indicates any deviation between the actual and desired runner-lengths A fail-safe module shuts down the knitting machine if the deviation between the actual and desired runner-lengths is greater than a predetermined amount In addition, data acquisition means are included which can monitor such conditions as actual and desired runner-lengths, error between actual and desired runner-lengths, number of knitting interruptions, and duration of knitting interruptions

A linear delta modulator integrated circuit with 17-Mbit/s sampling rate

Abstract: Delta modulation (DM) is an attractive method of analog-to-digital (A/D) conversion in applications where simple and economical designs must be realized without sacrificing conversion quality. This paper describes a new single-chip, bipolar integrated circuit delta modulator that maintains a high conversion resolution over a wide range of sampling frequencies and ambient conditions. Its high-speed operation (maximum sampling rates greater than 15 Mbit/s) is achieved with lower power requirements than with comparable discrete realizations. Low sensitivities to power supply and ambient temperature variations, achieved with a novel logic design, make this circuit useful in a telephone switching office environment and as a building block for other linear and companded analog-to-PCM converters.

Digital time measurement system

Abstract: This invention relates to the digital measurement of times and time intervals. An object is to provide time measurement data in a form suitable for input to a digital computing system. In a particular form of the invention, a number of oscillators or signal sources are synchronized so that their output frequencies are related exactly as successive powers of two, and their output signals are maintained in a predetermined phase relationship. For example, a set of oscillators may be arranged to generate signals of 1 MHz, 2 MHz, 4 MHz, 8 MHz, etc. Sample-and-hold circuits are used to sample and hold the oscillator signal values at the time of a pulse signal whose time is to be measured. Binary (twostate) signals are generated whose values correspond to the polarities of the sampled oscillator signal values. These binary signals are connected to simple logical circuits which resolve any ambiguities and generate the desired digital number in a normal binary or other desired form. This generated number is a digital measure of the time of occurrence of the pulse which initiated the sampling operation. Time intervals may be measured by two such sampling operations and a subtraction of the two resulting digital values.

Sampling modulation system for an electronic musical instrument

Abstract: A sampling modulation system for an electronic musical instrument has an audio frequency signal source, a sampling circuit, a memory circuit for memorizing the sampled signals, an output circuit for reading out the signals from the memory circuit, a control circuit which generates a sampling pulse train and a reading pulse train, and a modulating signal source. At least either the sampling pulse train or the reading pulse train has the frequency modulated by the modulating signal generated from the modulating signal source so as to provide a periodical difference between the sampling frequency and the reading frequency and accordingly to produce a phase modulation.

Unified theory of digital modulation

Abstract: A theory of signal quantisation is developed from first principles that describes quantisation using analogue-modulation techniques. The nonlinearities, which are fundamental to digital source encoding, are expressed by two sampling processes, which directly lead to solutions in terms of amplitude and phase modulation. The analysis derives a related set of mathematical models that deter mini stically describe the input/output transfer characteristics of uniform and nonuniform p.c.m., uniform delta modulation (d.m.) and uniform d.p.c.m.

Apparatus for electrically converting an analog signal into a digital representation

Abstract: A method is described for electrically converting an analog signal into a digital representation in a manner that maximizes noise rejection. The digital representation is formed from a preselected number of discrete points corresponding to sampled approximations of the analog signal. In establishing the magnitudes of the respective points, digital samples of the analog signal are taken at a predetermined number of discrete coordinates along the analog signal on either side of the respective discrete points. The predetermined number of coordinates are averaged and employed as corresponding approximations for the respective discrete points in the digital representative reproduction of the analog signal. The effects of harmonics of power line frequencies associated with processing electrical equipment are minimized by sampling the discrete coordinates for a particular point over an integral number of cycles of the power line frequency. In addition, noise having a high frequency, low duty cycle can be minimized by sampling a relatively large number of discrete coordinates over a period substantially greater than the occurrence of the noise.

Linear agc circuit with controlled duty cycle sampling means

Abstract: An intermodulation distortion analyzer generates two pairs of sinusoidal test tones to serve as a test signal for the channel under test. The two pairs of tones simulate two respective noise band test signals but eliminate the long time averaging required for measurements when noise bands are used. A highly linear AGC circuit employs sampling at an output-controlled duty cycle to maintain a constant reference level for the analyzer. This reference level permits automatic distortion measurements to be read out directly in db below the test signal. An RMS detector circuit for second order intermodulation products employs feedback control to maintain the input signal to a squaring circuit constant. Squaring of the constant level sinusoids produces RMS DC components which can be separated for direct measurement. A distortion circuit provides known levels of second and third order intermodulation in the test signal to permit accurate check out of the analyzer.

Rotary body control apparatus

Abstract: A rotary body control apparatus for controlling both speed and phase of the rotary body such as d.c. motor in a single circuit. Speed control is accomplished on the basis of a reference signal without provision of independent control system and, a phase comparison unit serving as means for detecting speed is provided to control phase. A number of stabilized regions is provided so as to effect locking-in with the reference signal in a suitable stabilized region with a reduction in time. The apparatus consists of speed signal generating means, reference signal introducing means, output signal forming means, output signal sampling means, and oscillating means.

Linear Delta Modulator Integrated Circuit with 17-Mbit/s Sampling Rate

Abstract: Delta modulation (DM) is an attractive method of analog-to-digital (A/D) conversion in applications where simple and economical designs must be realized without sacrificing conversion quality. This paper describes a new single-chip, bipolar integrated circuit delta modulator that maintains a high conversion resolution over a wide range of sampling frequencies and ambient conditions. Its high-speed operation (maximum sampling rates greater than 15 Mbit/s) is achieved with lower power requirements than with comparable discrete realizations. Low sensitivities to power supply and ambient temperature variations, achieved with a novel logic design, make this circuit useful in a telephone switching office environment and as a buildlng block for other linear and companded analog-to-PCM converters.

Quantizing and Sampling Considerations in Digital Phased-Locked Loops

Abstract: Quantization and sampling effects on the digital phasedlocked loop (DPLL) structures obtained for demodulation of anglemodulated signals using extended Kalman filter algorithms are investigated for the high signal-to-noise ratio (SNR) case in this paper First, the problem of quantization is considered The validity of the uniform white sequence model for quantizer error in the DPLL is established independent of the sampling rate Simulation results are presented for several quantizer word lengths Also, an effective SNR is defined which allows prediction of quantized performance from unquantized results Secondly, minimum sampling requirements for the DPLL are considered The effect of sampling rate variation upon the predicted phase error covariance is examined Again, simulation results are presented and compared to the predicted phase error covariance values This results in an analytical method for determining minimum sampling rates for the DPLL Minimum sampling rates for quantized DPLL have also been determined using the effective SNR previously defined