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Showing papers on "Sampling (signal processing) published in 1980"


Journal Article
TL;DR: Effect of insufficient transverse sampling on quantitative positron emission computed tomography was investigated with computer simulation and measurements on parallel bar and line source phantoms.
Abstract: Effect of insufficient transverse sampling on quantitative positron emission computed tomography (ECT) was investigated with computer simulation and measurements on parallel bar and line source phantoms. Aliasing artifacts were observed and were found to be dependent on both the configuratio

469 citations


Journal ArticleDOI
TL;DR: The effects of aliasing (including pseudoaliasing), picket-fence effect, and leakage in the fast Fourier transform (FFT) are presented.
Abstract: The effects of aliasing (including pseudoaliasing), picket-fence effect, and leakage in the fast Fourier transform (FFT) are presented. A computer program was written to perform the FFT analysis of known inputs. The program has the capability of detecting aliasing by calculating an "aliasing coefficient" (Q), and will increase the sampling frequency and the number of points in the input sequence if aliasing occurs. The term "pseudoaliasing" is a phenomenon which is similar to aliasing (or fold-over) but related to the effects of picket fence and leakage. The "leakage coefficient" (ri) is a quantitative measure of the deviation from the fundamental frequency component with respect to the sampling frequency, when the input sequence has only one frequency component.

265 citations


Patent
14 Aug 1980
TL;DR: In this paper, an apparatus for automated diagnosis of automobile engine electrical system waveform patterns is described. Butler et al. employed an addressable random access memory which stores digitized information concerning the waveform and employed a tracking analog-to-digital converter using comparator means which also provided a waveform peak detector.
Abstract: An apparatus which permits the automated diagnosis of automobile engine electrical system waveform patterns is disclosed. Employed in conjunction with an addressable random access memory which stores digitized information concerning the waveform are further means which logarithmically reduce input amplitude values of the waveform and coordinates sampling times for the waveform with engine RPM so that the memory capacity is fully utilized. Input conversion of the waveform is accomplished by a tracking analog-to-digital converter using comparator means which also provides a waveform peak detector. Upon an address command, the memory output is input into a read only memory which provides an anti-log conversion of the logarithmic value stored in the memory, thereby providing an output corresponding to an actual value signal.

85 citations


Patent
13 May 1980
TL;DR: In this paper, a synchronous detector for double-sideband amplitude-modulated wave was proposed, which samples the modulated wave for short periods centered on instants of peaks of the carrier at regularlyoccurring intervals, with a sampling frequency greater than the Nyquist frequency.
Abstract: In receiving apparatus for a double-sideband amplitude-modulated wave, a synchronous detector which samples the modulated wave for short periods centered on instants of peaks of the carrier at regularly-occurring intervals, with a sampling frequency greater than the Nyquist frequency for the modulating wave, equal to the carrier frequency divided by an integer, and reconstructs the modulating wave from the sequence of samples in a reconstruction filter. This detector has a high output signal-to-noise ratio and produces a distortionless output with positive or negative overmodulation, and with reduced or suppressed carrier.

70 citations


Proceedings ArticleDOI
01 Jan 1980
TL;DR: A single-chip digital signal processor utilizing parallel multiplier and 3μ NMOS technology will be presented and can implement 41 second-order digital filter sections for 8kHz sampling of voiceband signals.
Abstract: A single-chip digital signal processor utilizing parallel multiplier and 3μ NMOS technology will be presented. Development can implement 41 second-order digital filter sections for 8kHz sampling of voiceband signals.

62 citations


Patent
21 Mar 1980
TL;DR: In this paper, a multi-channel memory system was proposed for monitoring and indicating changes in a scene from which electromagnetic radiation, such as visible light, emanates in a television system.
Abstract: A television system and method for monitoring and indicating changes in a scene from which electromagnetic radiation, such as visible light, emanates. A television system including a televison camera (10) scans the scene in known raster fashion in a series of image frames, producing an amplitude modulated video signal describing the energy intensity distribution of the scene. Clocking and gating circuitry (42, 44) triggered in synchronism with television camera synchronization signals defines a set of predetermined discrete spaced locations of the raster during each image frame and samples video signal amplitude at each of the defined locations. The same discrete locations a re sampled during each frame. Video selection circuitry (20) during a succession of sampling periods, inputs in real time a representation of each video amplitude sample to one of several storage channels (24, 26, 28) of a multi-channel memory system including a multi-channel counter. The video amplitude samples are allocated among the channels as a function of their amplitude values. The collection of stored amplitude samples in the multi-channel memory system thus constitutes a profile of the amplitude distribution of the video samples made during the frame. This first amplitude profile is then stored. The scanning, allocating and counting operation is repeated. Subsequently, comparison circuitry, (114, 116) in response to the development of a subsequent amplitude distribution profile, corresponding to a selected later frame, actuates an alarm (30) in response to the occurrence of a predetermined threshold difference between (1) the earlier and (2) a succession of later developed amplitude distribution profiles. Circuitry (132) is also provided for modifying characteristics of the threshold difference required to trigger the alarm. It has been found that even a single channel counter, responsive to video count samples in only a single amplitude range, can often provide enough information for a workable and inexpensive surveillance system.

61 citations


Journal ArticleDOI
TL;DR: The sampling of NTSC color signals is studied with the aid of the three-dimensional spectrum and a number of sampling structures which allow a 2fsc horizontal sampling rate are identified and possible reconstruction filters are described.
Abstract: The sampling of NTSC color signals is studied with the aid of the three-dimensional spectrum. The effect of various spatio-temporal sampling patterns on the spectrum is derived and some experimental measurements are given. A number of sampling structures which allow a 2fsc horizontal sampling rate are identified, and possible reconstruction filters are described.

46 citations


Patent
07 Feb 1980
TL;DR: In this article, a phase-encoded data signal demodulator is described for demodulating high speed, phase encoded data signals transmitted over radio channels to mobile and portable stations of a radio communication system.
Abstract: A demodulator is described for demodulating phase-encoded data signals transmitted on a noisy communication channel, such as, for example, radio communication channels of a radio communication system. The demodulator includes a digital phase-locked loop for phase-locking to the mid-bit transitions of the phase-encoded data signal, which, in the preferred embodiment is encoded according to the well known Manchester coding format, and further includes demodulating circuitry for sampling the phase-encoded data signal a predetermind number of times, weighting the samples according to predetermined weighting factors, totalizing the weighted samples for each bit interval and comparing the totalized samples to a predetermined threshold value for ascertaining the logical state of each bit of the phase-encoded data signal. For example, if the magnitude of the totalized samples is greater than or equal to the threshold value, a logical one state may be provided for the decoded data signal, and, if the magnitude of the totalized samples is less than the threshold value, a logical zero state may be provided for the decoded data signal. In preferred embodiments of the present invention, the weighting factors assigned to each sample may be either binary weighted or sine weighted, although any suitable weighting factors may be utilized depending on the characteristics of the phase-encoded data signal. The phase-encoded data signal demodulator embodying the present invention is particularly well adapted for demodulating high speed, phase-encoded data signals transmitted over radio channels to mobile and portable stations of a radio communication system.

42 citations


Patent
02 May 1980
TL;DR: In this article, a calibration/zero control is combined with an electro-optical measurement instrument in a time-multiplex fashion to provide a self-diagnostic in situ measurement system and automatic compensation of the entire electrooptical train without interruption of the measurement process.
Abstract: A calibration/zero control is combined with an electro-optical measurement instrument in a time-multiplex fashion to provide a self-diagnostic in situ measurement system and automatic compensation of the entire electro-optical train without interruption of the measurement process. The electro-optical instrument includes a laser which provides a source of substantially monochromatic electromagnetic radiation (laser beam) and optics for collection and focusing radiation onto a detector. The radiation is directed through a sampling volume where it impinges upon an object whose properties or physical characteristics are to be measured by scattering techniques. The calibration/zero control includes an element rotatably positioned in the path of the electromagnetic radiation, optically upstream of the sampling volume, in having an axis of rotation perpendicular to the optical axis such that the radiation is periodically blocked and sampled. The laser source is synchronously pulsed to fire in accordance with the position of the calibration/zero element. The calibration/zero element is constructed such that in one blocking position, a predetermined fraction of the laser beam is allowed to penetrate and pass through the element to the collection optics and detector. The analog voltage of the detector is time-multiplexed to develop diagnostic information including a calibration signal, a zero radiation signal and a measurement signal. All signals are developed under the control of a timing signal derived from the calibration/zero control.

38 citations


Journal ArticleDOI
TL;DR: A relation between the required oversampling factor N = f' s /f s and the improvement in dynamic range (R = B- B') is derived which indicates that for moderate values of R (3 to 5 bits) the oversamplings factor must range from 6-15, which is quite acceptable.
Abstract: A method is described for improving the dynamic range of A/D and D/A converters. In the case of A/D conversion it consists of an analog preprocessing, an A/D converter of B' bits operating at a high sampling rate f' s , followed by a digital postprocessing. This system effectively operates as an A/D converter with B > B' bits with low sampling rate f s . A relation between the required oversampling factor N = f' s /f s and the improvement in dynamic range (R = B- B') is derived which indicates that for moderate values of R (3 to 5 bits) the oversampling factor must range from 6-15, which is quite acceptable. The method is also applicable to D/A conversion, but then the pre-processing has to be digital and file postprocessing analog.

35 citations


Patent
01 Feb 1980
TL;DR: In this article, a method and an apparatus for controlling the sampling of a composite analog color video signal so that the analog signal is sampled at precise locations relative to the phase of the color subcarrier of the video signal in the absence of modulation is presented.
Abstract: A method and apparatus is disclosed for controlling the sampling of a composite analog color video signal so that the analog signal is sampled at precise locations relative to the phase of the color subcarrier of the color video signal in the absence of modulation. The invention thereby enables a digitized signal having a constant phase relationship relative to the unmodulated subcarrier phase to be provided which can be advantageously used in magnetic recording and reproducing apparatus. Since the constancy of the location of the samples relative to the phase of the color burst is maintained prior to recording, there is no phase error that would pose a problem during reproducing of the signal. The apparatus stores a set of reference samples of a selected number of cycles of the color burst interval of the color video signal and generates an output clock signal that is phase synchronized with the reference samples, subsequently stores sets of comparison samples of color burst cycles from subsequent horizontal video lines using the generated clock signal and detects any error in the phase location thereof. The apparatus adjusts the phase of the generated output clock signal in response to any detected error signal and stores a new set of reference samples in the event that the error detected is beyond predetermined limits.

Patent
17 Dec 1980
TL;DR: In this article, a waveform searching system for a sampling oscilloscope is presented, in which the instantaneous level of a high-speed sawtooth signal generated by a trigger signal synchronized with an input analog signal and the instantaneous levels of a properly attenuated or amplified X-axis sweep wave are compared with each other to generate a pulse in a case of coincidence therebetween, thereby to generate sampling pulses sequentially delayed after the trigger signal by a constant time.
Abstract: A waveform searching system for a sampling oscilloscope, in which the instantaneous level of a high-speed sawtooth signal generated by a trigger signal synchronized with an input analog signal and the instantaneous level of a properly attenuated or amplified X-axis sweep wave are compared with each other to generate a pulse in a case of coincidence therebetween, thereby to generate sampling pulses sequentially delayed after the trigger signal by a constant time; the input analog signal is sampled by the sampling pulses to produce sampled pulses; and the sampled pulses are displayed by the X-axis sweep signal on a CRT. In accordance with the present invention, there are provided detecting means for detecting a predetermined condition where a waveform formed by respective peak values of the sampled pulses cross in a predetermined direction at a predetermined search level by a predetermined number; and control means for sequentially changing a time base range until the detecting means detects the predetermined condition, whereby the sampled pulses having the predetermined condition are automatically displayed on the CRT.

Patent
08 Sep 1980
TL;DR: In this article, the subcarrier digital signals for digital demodulation are derived with the correct frequency from the sampling rate clock pulses CP by an adder and accumulator into which the number 582 is added modulo-2048 to generate an 11-bit number which represents the sub-carrier phase angle at each sampling pulse.
Abstract: If an N.T.S.C. signal is to be demodulated using a line-locked sampling rate such as 800 times the line frequency, the ratio between the sampling period and the subcarrier period has the awkward value of 455/1600. Line-locked sampling is nevertheless desirable, e.g. in digital standards conversion. The subcarrier digital signals for digital demodulation are derived with the correct frequency from the sampling rate clock pulses CP by an adder and accumulator into which the number 582 is added modulo-2048 (the register is an 11-bit register) to generate an 11-bit number which represents the subcarrier phase angle at each sampling pulse and which addresses a ROM providing sin and cos values representing subcarrier samples. 582/2048 is not exactly equal to 455/1600 but 2048 is a desirable denominator as it is a power of 2 and implies a ROM of suitable size. ##EQU1## is exactly equal to 455/1600. Another adder and accumulator counts modulo-40960 by increments of 16384 and when this adder overflows, an extra 1 is added in through the carry-in to the first adder. Modulo 40960 is set up by altering 10256 to 40960 when the overflow occurs. Alternative numerical values are disclosed which apply to a PAL system with sampling rate 816 times line rate. Phase lock to the color burst is established by examination of the V output of the main demodulators during the color burst. V=sine θ where θ is the phase error. This quantity is applied via a negative feedback loop to effect fine adjustment of the numbers 40960 and 16384. Similar provisions for PAL are disclosed as is the generation of a PAL switch signal of the correct phase. The apparatus can also be employed as a modulator.

Patent
12 Aug 1980
TL;DR: In this article, a compensatory amplitude adjustment is made to a sampled signal in accordance with the statistical deviation of the signal from a preselected statistical model, which is made by employing the sampled signal as a write-address for generating a statistical amplitude distribution function.
Abstract: A device for the correction of signal distortion occurring in a signalling channel. Compensatory amplitude adjustment is made to a sampled signal in accordance with the statistical deviation of the signal from a preselected statistical model. Signal sampling means employs the sampled signal as a write-address for generating a statistical amplitude distribution function. Inverse distribution function means, responsive to addressing by the distribution function, provides an output signal of compensatorily modified amplitude.

Patent
28 Jul 1980
TL;DR: In this paper, the analog signal is first converted to a frequency-modulated signal, if not already one, by sampling at a fixed rate, and then the digital words representing the sample values are written in sequence into a buffer memory, at the constant sampling rate.
Abstract: Method and apparatus for secure transmission of analog signals, particularly facsimile signals. The analog signal is first converted to a frequency-modulated signal, if not already one, and is then converted to a sequence of digital words representing the instantaneous frequency thereof, by sampling at a fixed rate. Next the digital words representing the sample values are written in sequence into a buffer memory, at the constant sampling rate. The digital words are then read out of the memory at a different, pseudo-randomly variable rate and converted back to an analog FM signal for transmission. The transmitted signal is, thus, a time-delay-modulated version of the original FM signal. Optionally, the digital word values may be transformed before being converted back to analog frequency form, so that the modulation content of the transmitted signal is scrambled, as well. Further security may be obtained by reading out from the memory in a pattern which differs from the write-in address pattern. The read-out rate from the memory is varied by changing the clocking rate of the read-out operation at pseudo-random times, to select the read-out rate from a plurality of available rates. The available rates include at least one which is faster that the write-in rate and one which is slower than the write-in rate. To avoid underflow or overflow of data at the memory, detection of an incipient underflow or overflow condition causes the read-out rate to be changed, respectively, from a faster-than-write-in rate to a slower-than-write-in rate, and vice versa; when the fast/slow nature of the rate is changed, the selection of the new rate is made pseudo-randomly from among the available choices. Also, the fast/slow nature of the rate may be reversed pseudo-randomly, either at random times or at preselected points.

Patent
16 Oct 1980
TL;DR: In this paper, the color video signal and the respective identifying signal are simultaneously read out of the memory, and a comparison is made between the readout identifying signal and a corresponding reference or read request signal, and at least the phase of the chrominance component of the read-out color video signals is controlled on the basis of such comparison.
Abstract: In apparatus for processing color video information composed of a color video signal having luminance and chrominance components and a respective identifying signal which identifies a phase of the chrominance component, for example, by indicating the frame, field and/or line of which the respective color video signal is a part; the color video signal and respective identifying signal are temporarily stored in a memory and, when the color video signal and the respective identifying signal are simultaneously read out of the memory, a comparison is made between the read-out identifying signal and a corresponding reference or read request signal, and at least the phase of the chrominance component of the read-out color video signal is controlled on the basis of such comparison. In the case where a line of the read-out color video signal is indicated by its respective identifying signal to be of a field which is different from the read request field defined by the then occurring reference or read request signal so that it would be spatially displaced from the corresponding line of the read request field, the value of at least the luminance component in the read-out line is replaced by an interpolated value derived from values of the luminance component in the lines adjacent the read-out line. When a PAL color video signal is being processed, absolute values of color difference signals are derived, for certain sampling points where such color difference signals do not appear, by interpolation of the values for such color difference signals from adjacent sampling points.

Patent
06 Jun 1980
TL;DR: In this article, a linear array of N detector elements having a form spacing of X cm between their centers is oriented parallel to the line scan dimension of a raster so that each element of the array optically scans the entire field of view at a rate of V cm per second.
Abstract: A scanning system wherein a linear array of N detector elements having a form spacing of X cm between their centers is oriented parallel to the line scan dimension of a raster so that each element of the array optically scans the entire field of view at a rate of V cm. per second. The detector elements are sampled every t s seconds where ##EQU1## k being an integer, and each produces, when sampled, an output signal proportional to the integrated energy exposure thereof between samplings. The output signals of the various detector elements are delayed as a function of each element's position within the array and the line scan rate. The delayed imaging signals add to provide an improved signal to noise ratio. The variability of the waveform of the composite output signal for smallsized distant targets is minimized by introducing a progressively increasing phase shift in the relative timing of the sampling signals and initial contact of the image at successive detector elements. The composite output signal of the array then corresponds to an average over all possible relative timings of sampling signals and initial contact of the image at a detector element.

Patent
11 Jun 1980
TL;DR: In this paper, the authors proposed a method to make recording and reproducing possible when a sound sampling frequency is not integer times of the frequency of a video vertical synchronizing signal, by applying time-axis compression to a sample of sound signals and producing and recording dummy samples including the information of the number of sound samples of each field.
Abstract: PURPOSE:To make recording and reproducing possible when a sound sampling frequency is not integer times of the frequency of a video vertical synchronizing signal, by applying time-axis compression to a sample of sound signals and producing and recording dummy samples including the information of the number of sound samples of each field CONSTITUTION:When signals obtained by sampling and quantizing sound signals at 48kHz are recorded on a VTR, the number of samples per field goes to 4,004, since vertical synchronizing signals are 60X1,000/1,001Hz The 4,004 samples are straddled to the 1st-5th fields in the order of 800, 801, 801, 801, and 801 Then time-axis compressed signals are recorded by adding dummy samples of the four- sample quantity to the field of 800 samples and those of the three-sample quantity to the fields of 801 samples At the time of reproduction, error correction is performed by an error correcting signal in accordance with error detecting information and, at the same time, a signal train composed only of sound samples and dummy samples is formed by deinterleaving process (operation completely opposite to interleaving process at the time of recording) and the dummy samples are then removed so as to produce a continuous signal train composed only of sound signals

Journal ArticleDOI
TL;DR: In this article, a comparison between the discrete and continuous implementation of Kalman filtering and optimal control for a stationary process is performed, and the computational effort for the two implementations differs only slightly, and that the discrete version provides more realistic results at low sampling rates.

Journal ArticleDOI
TL;DR: Analysis, simulation, and experimental results are presented validating this all-digital technique for acquisition and coherent tracking of a Doppler-shifted carrier at a low carrier/noise ratio and a large percentage bandwidth.
Abstract: By sampling zero crossings at the Nyquist rate (i.e., the predetection bandwidth) the phase of a narrow-band signal may be extracted directly with respect to an arbitrary, stable reference. Analysis, simulation, and experimental results are presented validating this all-digital technique for acquisition and coherent tracking of a Doppler-shifted carrier at a low carrier/noise ratio and a large percentage bandwidth. The key advantage of this scheme for microcomputer-based implementation is that phase comparison is accomplished by arithmetic subtraction, without the coordinaterotation transformation which is necessary for conventional I , Q sampling. Also, the phase-sampling process is independent of the phase error, which exists only as a numerical representation in the digital tracking algorithm. The technique is applicable to Costas suppressed-carrier tracking and to BPSK bit synchronization and demodulation, by programming the appropriate digital algorithms.

Patent
04 Dec 1980
TL;DR: In this paper, the amplitude of the waveform during a mid-talkspurt freeze-out at the receiver is interpolated as that of the amplitude in the previous period.
Abstract: In reconstructing the analog waveform from a syllabically companded delta modulated digital signal transmitted over a TDMA communication channel operating at near its maximum channel capacity, the noise created in a mid-talkspurt freeze-out is greatly reduced by interpolating the amplitude of the waveform during the freeze-out at the receiver as that of the waveform in the previous period. This makes the quality of voice transmissions in the face of freeze-outs substantially better than prior art techniques which induce background noise during freeze-outs, without the necessity of transmitting a voice activity compression (VAC) mask to control the operation of the interpolation apparatus in the receiver. The interpolation occurs for the first 15 msec sampling period following either a freeze-out or a true VAC operation. The interpolation operation is supplied only once so that if two or more consecutive sampling periods occur at the receiver where no channels are received for a particular voice port, the background noise is injected into the voice port. This prevents the uncontrolled repetition of the interpolation at the end of a talkspurt.

Patent
28 Jul 1980
TL;DR: In this article, a recursive-type digital filter comprising a calculation circuit is arranged to multiply an input signal including at least m-bit signal x n inputted at a predetermined sampling period and an output signal y n-k fed back to the input of the calculation circuit in accordance with the input signal X n after being subjected to a delay of k sampling periods by a k and b k coefficients corresponding to the filter characteristics, respectively.
Abstract: A recursive-type digital filter comprising a calculation circuit. The calculation circuit is arranged to multiply an input signal including at least m-bit signal x n inputted at a predetermined sampling period and an output signal y n-k fed back to the input of the calculation circuit in accordance with the input signal x n after being subjected to a delay of k sampling periods by a k and b k coefficients corresponding to the filter characteristics, respectively, and then the products are added thereby to produce data y n of (m+l) bits satisfying, ##EQU1## and serially deliver the upper m-bit data of the data y n as an output signal corresponding to the input signal x n . The filter further comprises a delay circuit for feeding back to the input of the calculation circuit a part of the round off data including the upper (m+1)th bit of the data y n so that the b k coefficient is multiplied by the fedback data of the upper (m+1)th bit and the product is added to the data y n , thereby to produce an output signal with reduced round off noise.

Patent
27 Oct 1980
TL;DR: In this paper, the phase ambiguity is resolved with a phase sensor coupled to the zero-crossing detector and a chroma inverter responsive to the phase sensor for inverting the delayed chroma relative to the reference subcarrier.
Abstract: In a television time-base corrector or synchronizer using a coherent memory, the input signal is written into predetermined memory addresses in order of their arrival after sampling begins for each horizontal line. The sampling occurs at a rate established by the chroma subcarrier. Sampling begins at a zero crossing of the subcarrier following a fixed interval after the horizontal synchronizing signal. Since the burst does not occur at a predetermined time after the horizontal synchronizing signal, the phase of the burst at a fixed interval after the horizontal synchronizing signal may vary when the source of the television signal changes, and this may result in horizontal displacement of the video on playback. In order to reduce the magnitude of the displacement, the zero-crossing detector operates on either positive or negative-going zero crossings. A phase ambiguity is thereby introduced which may result in color reversal. The ambiguity is resolved with a phase sensor coupled to the zero-crossing detector and a chroma inverter responsive to the phase sensor for inverting the delayed chroma relative to the reference subcarrier.

Patent
21 Jan 1980
TL;DR: In this paper, a 525 line N.T.C. color television signal is achieved by digitizing (40) with a sub-Nyquist sampling frequency f s which has a mean value 2 f sc ± 1/2 f F, or more generally m f L ±(p+1/2) f F (where f sc, f L and f F are the subcarrier, line scan, and field scan frequencies, and m and p are integers).
Abstract: Digital processing of a 525 line N.T.S.C. color television signal is achieved by digitizing (40) with a sub-Nyquist sampling frequency f s which has a mean value 2 f sc ±1/2 f F , or more generally m f L ±(p+1/2) f F (where f sc , f L and f F are the subcarrier, line scan, and field scan frequencies, and m and p are integers). Conveniently the sampling frequency is exactly 2 f sc during each field and suffers a 180° phase shift between fields. After processing, the signal is converted back to analogue form (50) and, to remove alias components, is comb filtered (30) over the frequency range f s -f v to f v (where f v is the maximum video frequency in the original signal) by averaging across a 262 line delay (24'), or more generally a delay of a field minus half a line. Preferably a second comb filter (10) is included before the digitizer (40); the two filters (10, 30) are then so arranged that the overall delay suffered over the whole frequency range is substantially the same. Digital comb filters can be used in which case the filters and converters are reversed in position and the initial sampling is at twice the required frequency f s . Improved diagonal luminance and vertical chrominance resolution is obtained with stationary pictures, and alias components are reduced.

Patent
25 Sep 1980
TL;DR: In this paper, a method and apparatus for correlating first and second signals where sampling values of the signals are multiplied together and discrete values of a correlation function are determined is presented, where the results of the multiplication are separately summed corresponding to equal time displacements between the multiplied sampling values.
Abstract: Disclosed is a method and apparatus for correlating first and second signals where sampling values of the signals are multiplied together and discrete values of the correlation function are determined. In one embodiment, the signals are sampled at different sampling frequencies such that one sampling frequency is a multiple of the other sampling frequency. A number of the respective last sampling values of the more fully sampled signal are stored and each sampling value of the more rapidly sampled signal is multiplied simultaneously by all of the stored sampling values of the more slowly sampled signal. The results of the multiplication are separately summed corresponding to equal time displacements between the multiplied sampling values. In a further preferred embodiment, a microcomputer is programmed for sampling the two signals with sampling frequencies having a ratio 1:k. The more slowly sampled signals are stored in an n stage register. The contents of corresponding register stages are multiplied in n multiplier circuits by the sampling values of the more quickly sampled signal. A summation store having m=k·n storage locations stores the multiplication values and a distributing circuit introduces the multiplication values into the storage locations associated with the respective time displacements for addition to the preceding storage location content.

Patent
06 Nov 1980
TL;DR: In this article, a digital pulse compression processor for reducing the processing loss in rget-echo signals caused by sampling time errors comprising a first processing channel for sampling the echo signal in accordance with pulses from a first clock signal and a second processing channel, with its pulses interlaced, was proposed.
Abstract: A digital pulse compression processor for reducing the processing loss in rget-echo signals caused by sampling time errors comprising a first processing channel for sampling the echo signal in accordance with pulses from a first clock signal and a second processing channel for sampling the echo signal in accordance with pulses from a second clock signal at the same sampling frequency as the first clock signal but with its pulses interlaced, in time, approximately midway between the pulses of the first clock signal to ensure that the largest sampling error will be one-quarter of a sampling period or less. The sampled signals in each channel are then digitized and compressed, and then processed to form the compressed signal envelope. The resultant signal envelopes from each channel are multiplied together to form a low-sidelobe narrow output pulse.

Patent
24 Dec 1980
TL;DR: In this paper, a method and apparatus for converting an input step waveform signal into a smooth output wave form signal is comprised of two sample and hold circuits (11, 12), one for sampling each step of the input signal and the other for synchronously sampling and holding the output waveform, a circuit (17-20) for providing a signal proportonal to the difference between the samples held in the sample-and-hold circuits, and means (21-23) for integrating the difference.
Abstract: A method and apparatus for converting an input step waveform signal into a smooth output waveform signal is comprised of two sample-and-hold circuits (11, 12), one for sampling each step of the input signal and the other for synchronously sampling and holding the output waveform, a circuit (17-20) for providing a signal proportonal to the difference between the samples held in the sample-and-hold circuits, and means (21-23) for integrating the difference. The output of the integrator is connected to the second sample-and-hold circuit while the step waveform to be filtered is connected to the input of the first sample-and-hold circuit. The integrator thus produces an output that is a linear signal during each clock pulse period with a slope equal the sign and amplitude of each step.

Patent
22 Feb 1980
TL;DR: In this paper, a tachometer is used to measure the radial speed of the heads with respect to the discs in a disc-pack data storage system, and a digital to analog converter converts the counted clock pulses to a voltage and amplifier circuitry derives from the voltage a speed signal indicative of radial speed.
Abstract: In a disc pack data storage system that has a plurality of discs and a plurality of heads for coaction with the discs, a tachometer for producing a signal indicative of the radial speed of the heads with respect to the discs. At least one of the disc surfaces is a servo surface and at least one of the heads is a servo head so that in response to radial movement of the servo head a triangular position signal is produced. Sampling pulses indicative of specific radial positions of the head are derived from the position signal so that the time required for the head to move between two positions represented by adjacent sampling pulses is inversely proportional to radial head speed. Control and computing circuitry measures the time between adjacent pulses by providing a clock pulse source and counting the number of clock pulses that occur between adjacent sampling pulses. There is circuitry for controlling the specific sampling pulses employed in accordance with radial head speed and the clock pulse source is frequency controlled to achieve accuracy at all radial speeds. A digital to analog converter converts the counted clock pulses to a voltage and amplifier circuitry derives from the voltage a speed signal indicative of radial speed. Circuitry active at very low speeds serves to combine with the speed signal a signal derived by integrating motor current so that an accurate tachometer signal is produced at all radial speeds.

Patent
26 Mar 1980
TL;DR: In this paper, a digital type distance relay system consisting of a sampling and hold circuit for sampling and holding the current in and voltage on a power transmission system, an A/D converter for receiving the outputs of the sampled and held circuit through a multiplexer and converting the received analog quantities into corresponding digital quantities I and V, and a digital computer.
Abstract: A digital type distance relay system comprises a sampling and hold circuit for sampling and holding the current in and voltage on a power transmission system, an A/D converter for receiving the outputs of the sampling and hold circuit through a multiplexer and converting the received analog quantities into corresponding digital quantities I and V, and a digital computer. The digital computer includes a data memory for memorizing the current I and voltage V and also a digital voltage Vp having a predetermined relation to the voltage V, a setting memory for memorizing a setting value Z0 for setting a range of protection of the power transmission system, a ROM for memorizing a program for executing an arithmetic operation according to the formula |I·Z0 +K1 Vp |-|I·Z0 -V-K2 Vp |≧K0 as well as the constants K1 and K2 and minimum sensitivity value K0, and a CPU. The CPU executes the program dealing with the afore-mentioned arithmetic operation formula and produces a command signal for taking an action of protecting the power transmission system if the arithmetic operation formula is satisfied while producing a command signal for taking no protective action if the formula is not satisfied. The protective action can be provided even in case when the voltage V in the arithmetic operation formula is zero in level.

Patent
07 Oct 1980
TL;DR: In this article, a method for recording a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape includes the steps of sampling the video signal at a frequency which is at least three times the color sub-carrier frequency of the colour video signal, converting the sampled video signal into digital form, and recording respective pluralities of the digitized samples which are arranged in a predetermined sequence sequentially in the plurality.
Abstract: A method for recording a color video signal in a plurality of parallel tracks extending obliquely on a magnetic tape includes the steps of sampling the video signal at a frequency which is at least three times the color sub-carrier frequency of the color video signal, converting the sampled video signal into digital form, and recording respective pluralities of the digitized samples which are arranged in a predetermined sequence sequentially in the plurality of parallel tracks, by either recording respective pluralities of contiguous digitized samples sequentially in the tracks, in which each plurality corresponds to at least one cycle of the color sub-carrier, or by alternately separating contiguous ones of the digitized samples into first and second blocks and recording respective pluralities of successive digitized samples of the first and second blocks sequentially in the tracks with the sampling frequency being equal to four times the color sub-carrier frequency, such that the chrominance component of the digital color video signal can be separated during reproduction so as to correct any error in the phase of the color sub-carrier, and such that with the first embodiment of the last-mentioned step, a digital filter having a chrominance characteristic C=(1-Z.sup. -2)/2 can be used, and with the method according to the second embodiment, a fourth order digital filter having a chrominance characteristic C=(-1=2Z -2 -Z -4 )/2 can be used to reproduce the chrominance component, where Z is a delay transfer characteristic of the respective filters.