Showing papers on "Sampling (signal processing) published in 1976"

Television picture size altering apparatus

Abstract: The size of a color television picture field is changed without changing the size of the raster. This is achieved in an apparatus that includes means responsive to a field of television video signals for sampling same and providing a predetermined number of samples of television video signals per line and a predetermined number of lines per field and means responsive to the predetermined number of samples per line and lines per field for providing a full field of television video signals. Size reduction is accomplished by causing the first mentioned means to skip samples provided at the output thereof in groups of N, where N is the number of samples in a color subcarrier cycle, and to skip line pairs of the field.

Method and apparatus for PCM-encoding NTSC color television at sub-Nyquist rate

Abstract: A sub-Nyquist sampled PCM NTSC color television signal is obtained directly from a PCM encoded color television signal sampled at four times the color subcarrier frequency by selecting every other sample in each line of the 4F sc sampled television signal and introducing a one 4F sc sample displacement every two sequential television lines A sub-Nyquist sampled signal may also be obtained from an NTSC color television signal having a color subcarrier frequency F sc by generating a sampling signal having a frequency of 2F sc , the sampling phase of which shifts by 180° every alternate time sequential television line, and sampling the NTSC color television signal in response to the sampling signal Whichever of these two techniques is used to obtain the sub-Nyquist samples, the 4F sc samples can be reconstructed when comb filters are used to remove alias components The process of converting 4F sc encoded signals to sub-Nyquist and back to 4F sc can be repeated without impairing picture quality beyond that introduced during the first conversion-reconversion process

Quadrature correlation pulse detector

Abstract: Digital apparatus and a method are disclosed for detecting a tone pulse of known carrier frequency in a signal in which random noise is present by correlating a clipped version of the input signal with a square wave reference signal having a repetition rate equal to the carrier frequency. Correlation is accomplished by multiplying the clipped input signal with each of quadrature components of the square wave reference signal and sampling the product signals to provide binary sample trains which are supplied to a pair of shift register accumulators. Reversible counters and associated logic determine the differences in the numbers of samples of noncorresponding binary values in each of the shift registers, and provide counts which are added to produce a moving correlation signal which indicates presence of a tone pulse when it exceeds a predetermined correlation threshold.

Cross-correlator circuit

Abstract: In a system for measuring the time delay existing between two pattern related random signals of similar but not identical modulated characteristics, utilizing the techniques of cross correlation, two analogue input signals are digitally quantized into binary form according to signal polarity. The first or leading quantized signal is delayed by a series of sequential time intervals or sampling periods to provide a time controlled sequence of delayed leading-signals at equal intervals. These delayed leading-signals are compared by a multiplication technique with the quantized second or lagging-signal, the occurrence when the signals correspond being summed in a series of overflow counters. The rate of filling of the responsive counters is proportional to the respective degree of correspondence and leads to one counter overflowing first, being indicative of the most probable time delay between the two signals. A variable frequency oscillator is used to control the sampling period so that overflow takes place most often in a selected one of the series of counters. To improve the time delay resolution, and to utilize higher frequency components of the signals, once a definite indication of cross correlation is achieved, the sampling period is reduced to a chosen fraction, such as one fifth, and increasing the number of time delay intervals imposed on the leading signal by the corresponding integral multiple, namely five to maintain the overflow in the same selected counter. The two mode operation described permits enhanced precision of time delay determination with economy of components. The readout for the system is derived from the oscillator frequency. The system is suitable for use with an ultrasonic velocity meter for measuring liquid flow in a pipe.

Interpreting laser and hot-film anemometer signals in a separating boundary layer

Abstract: • RECENTLY an experimental study of a separating in-I^compressible turbulent boundary layer produced by an adverse pressure gradient was completed. A directionally sensitive fringe-type laser anemometer with a Bragg cell was used to measure the mean streamwise velocity £7, the meansquare fluctuation w, and the fraction of time the flow was moving in the downstream direction yp. In addition, a constant-temperature single-sensor cylindrical hot-film probe (Thermo-Systems, Inc., model 1274-10) was used to compare the behavior of this directionally insensitive sensor with the laser anemometer results. The purpose of the Note is to discuss the interpretation of signals from these two instruments in a separation region, i.e., when yp < 1. Sampling spectrum analysis of the laser anemometer signals was used because of the high-signal dropout level encountered in this flow with a relative low-particle seeding level and the high-signal frequencies produced by frequency shifting one incident beam. Most frequency trackers cannot handle either of these signal conditions. The signal from the photomultiplier tube or detector is input to a swept filter spectrum analyzer (HP 8558B). For each sweep of the analyzer when a particle (about 1 in size) is in the focal volume, a vertical voltage distribution proportional to the filter output is displayed. The simultaneous horizontal sweeping voltage is proportional to the signal frequency. The peak of the vertical voltage distribution marks the frequency of the passing particle signal and can be used as a gating signal to allow the instantaneous value of the horizontal sweep voltage to be sampled. This instantaneous voltage value is related to the instantaneous velocity £7 of the particle through the equation

Data slicing apparatus and method

Abstract: A data slicer including detector means connected to a signal input for detecting the presence of data clock pulses on an incoming signal. Generator means are connected to the detector means for generating a sampling pulse during the time that the presence of the data clock pulses is detected. Filter or delay means are connected to the signal input for establishing the mean level of the incoming clock pulses. Sampler means are connected to the filter or delay means for sampling the mean incoming signal level when established by the filter or delay means during the sampling pulse interval and for storing the sampled signal. Comparator means having a first input are connected to the signal input and a second input connected to the sampler means for receiving and comparing the incoming signal with the sampled signal stored in the sampler means to effect slicing of the data from the incoming signal. As any distortion present on the incoming signal will affect the clock pulses and data equally, by selecting a slicing level determined from the clock pulses, the optimum level for slicing the subsequent data is established.

Closed-loop mixture control system for an internal combustion engine using sample-and-hold circuits

Abstract: A closed-loop mixture control system for an internal combustion engine comprises an exhaust composition sensor, a comparator for comparing the signal derived from the sensor with a reference point to determine whether the air-fuel ratio of the mixture is above or below a desired value, and a sample-and-hold circuit for sampling the comparator output at intervals equal to or longer than the transport delay time of the engine and holding the sampled signals until the next sampling occurs. The output from the sample-and-hold circuit is connected to a controller for proportional amplification to vary the fuel quantity proportionally to the input signal applied thereto. Preferably, the system includes an analog shift register into which is serially clocked the output from the sample-and-hold circuit synchronously with the sampling frequency and then clocked out in parallel form to a weighting network before amplification by the controller.

Quadrature correlation phase determining apparatus

Abstract: Digital apparatus and a method are disclosed for determining the phase angle of a tone signal of known frequency by correlating a clipped version of the tone signal with a reference signal having a repetition rate equal to the tone frequency. Correlation is accomplished by multiplying the clipped tone signal with each of quadrature components of the reference signal and sampling the product signals to provide binary sample trains which are supplied to a pair of shift register accumulators which effectively frame a moving phase measurement window. Reversible counters and associated logic determine the magnitudes and signs of differences in numbers of samples of noncorresponding binary values in each of the accumulators, and provide counts representative of in-phase and quadrature components of the product of the tone signal and the reference signal. The counts are utilized in a digital processor to compute the phase angle of the tone signal relative to the reference signal.

Transversal type automatic phase and amplitude equalizer

Abstract: A transversal type automatic equalizer includes circuits for differentiating the equalized signal, sampling the equalized signal under the control of a timing signal, and generating an error signal from the sampled signal. The differentiated and error signals are multiplied together and a variable phase shifter phase shifts the timing signal in response to their product to provide optimum equalization.

Method and device for synchronizing the receiver clock in a data transmission system

Abstract: A clock setting circuit is provided at a receiving modem for adjusting the phase of a timing signal defining the signal sampling instants. The received signal is filtered in two filters to derive a first signal having a phase φ 1 and a frequency f 1 equal to f c - 1/2T, f c being the carrier frequency and 1/T being the transmission baud rate, and a second signal having a phase φ 2 and a frequency f 2 equal to f c + 1/2T. The first and second derived signals are combined to derive an error signal indicative of the phase difference φ 2 - φ 1 which difference is used for adjusting the phase of a phase locked oscillator which provides the timing signal.

Living body function measuring apparatus

Abstract: A heart/lung function measuring apparatus comprises a source for permitting a constant slight current of a high frequency wave of predetermined frequency to flow through a to-be-measured portion of a living body, a voltage detection section detecting a voltage loop based on the impedance of the living body area, a sample-hold circuit for sampling a predetermined level of an output signal of the voltage detection section and holding the sampled value, a peak detector for generating a detector output according to a peak voltage of the output of the detection section, a pulse generator for generating a pulse signal which is applied as a trigger signal to the sample-hold circuit according to the output of the peak detector, and a subtractor for obtaining a difference output between the output of the voltage detection section and the output of the sample-hold circuit.

Piecewise linear predictive coding system

Abstract: Improved fidelity and reduced computational requirements are achieved in a linear predictive coding (LPC) system that utilizes multichannel signal processing and reduced sampling rates. The input analog signal is divided by filters into multiple, contiguous, substantially equal bandwidth signal components and each component is digitized and processed by a separate standard LPC transmit-receive system. Each transmit-receive system operates at a sampling rate that is equal to the normal sampling rate for the signal being processed divided by the number of channels or signal components used. The received signal components are filtered, converted to analog, and summed.

Acoustic holography apparatus

Abstract: Apparatus and method for forming acoustic hologram patterns, comprising a receiver transducer for detecting acoustic waves scattered by an object, a scanning system for moving the receiver relative to the object, a sampling system for taking samples of a signal derived from the receiver transducer at selected instants relative to the phase of the acoustic signals at the transmitter, the selected instants being determined according to the phase of a chosen notional reference wave at the position of the receiver transducer relative to the phase of the chosen notional reference wave at a datum point, and a system for plotting the samples versus the displacement of the receiver transducer so as to form a graphical diagram representing an acoustic hologram of the object. The receiver signals are preferably applied to a phase-locked frequency-multiplier circuit and the samples taken from the output of this circuit. The sampling system may include a switch circuit arranged to apply a series of predetermined voltages in sequence to a comparator controlling a sampling gate.

System for coding and/or decoding color television signal including luminance and chrominance information

Abstract: A system for coding a composite color television signal and a system for decoding the received coded composite color television signal are disclosed. Coding is achieved by the use of a sampling frequency lower than the Nyquist sampling frequency to provide a direct-coding system in which the composite television signal is sampled at a timing where the subcarriers stand at phases about 180° away from each other in each scanning line and at a timing where the subcarriers stand at phases about 90° away from each other between adjacent scanning lines. In the decoding system, an interspatial signal component lying at a midpoint between every two sampling points is produced from the sampled signals. A composite television signal is produced from the sample signal and the interspatial signal.

Transient analog signal capture and transmission system

Abstract: A system for monitoring a physical phenomenon manifested by a change in displacement, including means for sampling, digitizing and recording a transient analog electrical signal associated therewith having a component of interest at a given frequency not exceeding approximately 100 KHz., and means for transmitting said digitized analog signal samples over a low grade communication link having an upper frequency limit substantially less than the high frequency component of interest in the transient signal.

Signal delay means using bucket brigade and sample-and-hold circuits

Abstract: OF THE DISCLOSURE The present invention relates to an improved signal delay circuit. In both the transmit and receive circuits of FM communications systems, it is often necessary to delay a particular signal in order to improve the performance of the system. Prior art delay circuits are undesirable because of the high cost of elaborate generators, filters and phase linearity compensators required to eliminate their associated noise and resulting signal degradation. The present invention provides an improved delay circuit having low insertion loss and low phase distortion charac-teristics. This is accomplished by a bucket brigade device for sampling the signal and time delaying the samples, a sample-and-hold device for sampling and sorting the voltage levels of the individual delayed samples in succession, and a clock for developing timing signals for controlling the delay line and the sample-and-hold device.

Peak detecting demodulator

Abstract: A demodulator wherein the typical low-pass filter is replaced with a samplend hold circuit. By sampling the peak information of the input a-c signal and storing until the next peak sample, an output of extremely low ripple is accomplished.

Radio direction finder with array element signal processing

Abstract: A radio navigational device for determining the angle of a mobile craft by analyzing the signals arriving at each element of a linear array of n equally spaced elements. A series of received R.F. pulses emanating from the mobile craft by transmission or reflection provide contemporaneous signals at the antenna elements with a phase difference ψ between successive elements in accordance with the angle of arrival of the R.F. pulses. Using "zero" IF techniques, each signal of the series is processed to provide signal outputs in I and Q form. Sequential or parallel sampling of these I and Q signals provides a synthesized scanning beam signal from which ψ is determined.

Phase control system

Abstract: A television signal is encoded by the use of a sampling pulse synchronized with a color subcarrier frequency included in an input television signal, the encoded signal is compressed and recorded in a memory for later reproduction of a desired compressed picture image having a desired size and center position, the recorded signal is reproduced under the control of a clock pulse signal produced in synchronism with a sync signal obtained in a studio, for example, and the reproduced signal is corrected by inverting the polarity of the chroma component according to frame information at the time of recording of said reproduced signal. Thus, it is possible to freely obtain phase coupling of different synchronizing signals; for instance, it is possible to bring the phase of a different television signal of a different synchronization system into coincidence with the phase of a central synchronization signal and it is possible to reproduce an object image optionally compressed on a TV display screen.

Digital acquisition and interactive processing of ultrasonic echoes

Abstract: The requirements for an interactive digital signal processing system for ultrasonic pulse-echo signals are discussed. A system based on an Interdata Model 80 mini-computer and micro-processor interface is described. The system is capable of acquiring ultrasonic data at a sampling rate of 6 MHz. Ultrasonic B-mode data may be acquired in Line Mode, when echo waveform data and transducer position and orientation are stored, or in Section Mode when the data is converted directly into picture form in memory in the same way that a standard echogram is formed on the screen of an oscilloscope. In each case the data for single complete high resolution echogram may be acquired in less than 15 sec. It is shown that the 6 MHz sampling rate is sufficient to faithfully preserve the echo waveshape of a 2 MHz system independently of the relation to the phase of the sampling. Also shown is a cross-sectional echogram of the pregnant uterus, and its digital representation with a raster density of 80 × 100 and 160 × 200 picture elements. The computer is programmed with an interactive program to allow ultrasonic signals to be acquired, stored, processed and examined with the convenience of a desk calculator. Sample operations are illustrated including data interpolation, spectrum analysis, filtering and complex signal deconvolution. The ability of deconvolution techniques to resolve targets separated by less than one wavelength in depth is demonstrated. Possibilities of further processing techniques are outlined.

Properties of Low Precision Analog-to-Digital Converters

Abstract: The problem of quantization and saturation noise introduced by the process of analog-to-digital conversion is addressed. Analog-to-digital converters (ADC) with even versus odd numbers of output states are compared. Expressions are derived and evaluated which yield the signal-to-noise ratio and the gain versus signal level input when the input signal has an assumed Gaussian probability density. The results presented should have application in all fields in which digital signal processing is performed.

Pulse code modulated, time division multiplex switching network

Abstract: A pulse code modulation, time division multiplex (PCM/TDM) switching network is used in tandem exchanges for connecting receive and transmit trunks and for allocating receive time slots to time slots to be used on the transmit trunks is described. A storage is assigned to each pair of associated receive and transmit trunks. The storage includes storage areas which are selectively connectable to the associated pairs of trunks. A storage location used for a call is seized sequentially during each sampling pulse frame with data coming in over the receive trunk as well as with data outgoing over the transmit trunk. Inputs and outputs of the storage areas not connectable to the trunks are combined with coordinated inputs or outputs of the storage areas of other similar storages. Information output and input likewise takes place selectively over the combined inputs or outputs.

Switching-mode absolute-value amplifier and its applications

Abstract: Proposes methods of absolute-value and variable-phase operations using switching techniques. These methods show high efficiency and characteristics suitable for use in very-low-frequency regions due to its sampling effects. This paper introduces the basic principle, theoretical analysis, and characteristics of the switching-mode absolute-value amplifier and presents the realization of a variable-phase ultra-low-frequency signal generator by means of the switching-mode operations.

Multi-channel implicit ratio computer for sequential signals

Abstract: A multi-channel electrical signal ratioing circuit for a source delivering an electric analog pulse signal sequence having a broadened choice of ratio denominator terms provided by parallel-connected DC-coupled individual signal ratioing circuits each incorporating its own associated gated integrator, variable gain amplifier and at least one sampling circuit to form the several ratios needed. The basic ratioing circuit includes means for compensating against the effects of background influences, such as amplifier signal offsets, line voltage variations and changes in electrical system gains or other anomalies affecting ratio determination accuracy.

Switching arrangement for transmitting data in time division multiplex systems

Abstract: A switching arrangement is described for transmitting data in time division multiplex (TDM) systems on a character frame basis. The system includes a polarity reversal recognition circuit producing a polarity reversal signal and signaling polarity reversals of a data signal. A blocking circuit arrangement produces a stop signal thereby blocking the polarity reversal recognition circuit throughout the duration of a predetermined number of m bits of the data signal. A clock generator produces a clock signal which facilitates the sampling of the data signal. A shift register is provided which contains no fewer than m+2 cells and has a set of parallel input terminals for the parallel coupling of binary digits to the shift register. Serial input terminals to the shift register provide for the serial application of binary digits to the shift register. A clock pulse input terminal to the shift register receives shift register clock pulses. A gate is provided for receiving the polarity reversal signal and the output signal of the last cell of the shift register. The output from the foregoing gate yields a phase position signal which is utilized to determine the phase position of the clock signal which is applied to the aforementioned clock pulse input terminal of the shift register. The output signal of the second to last cell of the shift register is applied as a stop signal to the polarity reversal recognition circuit. The phase position signal is coupled to two or more parallel input terminals of the shift register. The serial input terminals of the shift register receive binary digits differing from the binary digits of the phase position signal that are applied to the parallel input terminals of the shift register.

Skip field recorder with audio multiplexer

Abstract: In the recording section of a system for recording and reproducing a television signal containing a video signal component and a sound signal component the length of recording time is increased for a given amount of recording medium by periodically sampling the video signal component, for example, for alternate frame periods, and the sound signal component and a delayed sound signal component obtained by means of an one-frame delay device are alternately sampled for the first half and the second half of each line period during the sampled frame period in order to be recorded on a recording medium and be reproduced from the recording medium. In the reproducing section, each recorded frame of the video signal component is reproduced twice in succession along with the sound signal component, and the reproduced sound signal component is sampled for the first half of each line period during the first reproduction of the recorded frame and for the second half of each line period during the second reproduction of the same frame.

Turbine-generator protection system with electronic sampling filter

Abstract: A system for protecting a turbine-generator power plant governed by signals representative of turbine mechanical power and generator electrical power to reduce at times the turbine mechanical power, with an electronic filter included therein for the purposes of filtering a periodic time varying component of the electrical power signal having a response time within adequate protective limits, is disclosed. More specifically, the electronic filter generates a train of fixed time durations wherein during each fixed time duration the maximum and minimum amplitudes of the electrical power signal are selected. A signal is sampled at the end of each fixed time duration and held constant for each next fixed time duration, said signal being representative of the average of the maximum and minimum amplitudes selected during each fixed time duration. In employing these sampled filter techniques, the electronic filer can respond to electrical power signal disturbances with a response time approximately equal to one fixed time duration while generating a sampled average signal of the electrical power signal free of the time varying component.

Method and apparatus for measuring the bit error frequency in a cable caused by crosstalk between line pairs during transmission of a 3-level coded pcm signal

Abstract: A method and an apparatus for measuring the bit error frequency in a cable caused by crosstalk from at least one disturbing pair to a disturbed pair at transmission of a 3-level coded PCM signal utilizes the fact that a PCM signal transferred on a pair and the disturbances superimposed on this signal by crosstalk from other pairs are mathematically uncorrelated. The amplitudes of the disturbances measured on the disturbed pair are sampled after equalization in a regenerator with a sampling frequency which equals the bit time frequency of the PCM signal intended for transmission on the pair. The number of detected sampling values whose magnitude exceeds a certain threshold value is a function of the estimated bit error frequency.

Speech synthesizing apparatus

Abstract: Speech synthesizing apparatus is provided using digital coded values specifying parameters of a sound to be reproduced. The apparatus has a voiced sound generator using digital values specified by input parameters to represent three formant waveforms respectively which are sampled at substantially constant intervals, the parameters each expressing in relation to the sampling interval the frequency of the formant concerned. At each sampling, the input parameters are arranged to derive for each formant waveform respectively a value representative of the instantaneous amplitude of that waveform in relation to the others, the three values obtained then being combined to produce a resultant value representing an instantaneous amplitude output of a voiced sound component waveform. This output waveform is subjected to modification by attenuation and the addition, if required, of an unvoiced sound component before being passed through an analogue converter to a sound reproducing transducer. The sampling rate is chosen to produce a succession of outputs at sufficiently short intervals to approximate continuous speech after being subjected to a low pass filtering operation. The apparatus has provision for the interlaced sampling of a number of channels.

Narrow band television system

Abstract: PURPOSE:A narrow band television system, that varies scanning time for one field by sampling output signal of the first dimension light sensor or verying rotation velocity of photo-apparatus, and/or performing both at the same time.