Showing papers on "Digital signal published in 1986"

Digital radio frequency receiver

Abstract: A digital radio receiver is described. The digital receiver of the present invention contemplates a digital radio receiver which operates on a received analog signal which has been converted to a digital form after preselection at the output of the antenna. The digital receiver of the present invention comprises a preselector, a high-speed analog-to-digital (A/D) converter, a digitally implemented intermediate-frequency (IF) selectivity section having an output signal at substantially baseband frequencies, and digital signal processor (DSP) circuit performing demodulation and audio filtering. The radio architecture of the present invention is programmably adaptable to virtually every known modulation scheme and is particularly suitable for implementation on integrated circuits.

Fast algorithms for digital signal processing

Abstract: This new textbook by R. E. Blahut, which deals with the theory and design of efficient algorithms for digital signal processing, contains perhaps the most comprehensive coverage of fast algorithms todate.Alargecollectionofalgorithmsistreated,withanemphasis on implementing the two canonical signal processing operations of convolution and discrete Fourier transformation. In recent years, there has been much work done on fast algorithms,andBlahutdoesafinejobofblendingmaterialfromdiverse sources to form a coherent and self-contained approach to his subject.The mathematical level of this book is high, reflecting the rather abstract nature of the theoretical underpinnings of fast computational techniques. Although electrical engineers are forthe most part mathematically sophisticated, they tend to lack training in abstract algebra and number theory, both of which are essential to any thorough discussion of fast algorithms. Thus this audience should find the tutorial chapters which the text provides on these topics to be quite helpful. An additional feature of the text, which the nonspecialist should find useful, is that each new algorithm is described through three different formats: a simple example, a flowchart, and a set of matrix equations. This use of repetition assists the reader in grasping subject matter which for the most part is nonintuitive. Operation counts (as measured by the number of multiplications and the number of additions) for each algorithm are tabulated for avarietyof blocklengths (i.e., lengths of data segments), making performance comparisons easy. As the author points out, run-time comparisons may be quite different. Each chapter concludes with a set of problems of varying difficulty. These problems are well integrated with the text and serve to supplement the many examples worked out in the text. The book is devoted to how one rapidly computes various mathematical operators such as transform and convolutions. For a deeper understanding of the meaning of theseoperators,one must consult other sources in which their use is discussed. The text emphasizes algorithms which employ a reduced, or minimum, numberof muItiplications,althoughadditioncountsarealsotaken into consideration. However, an algorithm which is the “fastest” as measured in arithmetic operation counts may not be the fastest in execution time, particularly if dedicated hardware is employed. Indeed in practiceother considerationsfrequentlypropel oneaway from the computationally ”optimal” algorithm. Much work has been done on the theory and application of signal processing algorithms which are “efficient” in terms other than rnultiply/add counts, such as roundoff noise, limit cycles, coefficient quantization, memory access, hardware costs, etc. It is clearly necessary to limit the scope of any treatise, and the exclusion of differing performance measures is certainly appropriate. A description of the contents of the book will now be given, followed by some concluding remarks of a more general nature. Chapter 2 i s a tutorial on abstract algebra. It i s quite readable and is liberally laced with examples. In addition to the standard modern algebra fare (groups, rings, fields, vector spaces, matrices), the ubiquitous Chinese remainder theorem is discussed in detail. Chapters 3 and 4, and their extensions in Chapters 7and 8, form the core of the text. The third chapter addresses fast algorithms for short convolutions. The Cook-Toom convolution algorithm is discussed, followed by the Winograd convolution algorithm. A proof of the optimality of the Winograd algorithm, with respect to multiplications, for performing cyclic convolutions, is presented at the close of the chapter. The fourth chapter addresses fast algorithms for computing the discrete Fourier transform. The CooleyTukey algorithm is considered first. The approach taken is to view this algorithm as a means of mapping a onedimensional Fourier transform into a multidimensional transform. Variations of the algorithm are discussed, including the Rader-Brenner transform. Next, the Good-Thomas algorithm is discussed. This algorithm is again presented as a means of mapping a onedimensional transform into a higher dimensional transform, this time based on the Chinese remainder theorem. Rader’s algorithm for computing primelength Fouriertransforms by useofconvolution ispresented next. Extensions of the algorithm to blocklengths which are the power of an odd prime are considered. The chapter closes with the Winograd-Fourier transform which builds upon the Rader prime algorithm. Certain short blocklengthsareconsidered in detail,and the corresponding algorithms are compiled into an Appendix. Chapter 5 i s a mathematical interlude, tutorially covering items from number theory and algebraic field theory which are needed in later chapters. Topics include the totient function, Euler’s theorem, Fermat’s theorem, minimal polynomials, and cyclotomic polynomials. Chapter 6 is devoted to number theoretic transforms. These transforms proceed by representing the data values themselves in the field of integers modulo a prime. Convolution in integer fields is also covered. Chapters 7and 8 extend the convolution and transform methods of Chapters 3 and 4 to higher dimensions. Multidimensional transforms (convolutions) are used both to efficiently compute onedimensional transforms (convolutions) and to process data which are inherently higher dimensional. Both applications are treated in these chapters. Topics include the Agarwal-Cooley convolution algorithm, polynomial transforms, the family of Johnson-Burrus transforms and the Nussbaumer-Quandalle FFT. Chapter 9 discusses architectures for transforms and digital filters and includes treatmentsof FFT butterfly networks and overlapadd convolution. The remaining three chapters are mostly independent from the rest of the book. Chapter 10 covers fast algorithms based on doubling strategies. Computational tasks for which such fast algorithms are derived include sorting, matrix transposition, matrix multiplication, polynomial division, computation of trigonometric functions, and coordinate rotation. Many of theseoperations arise as steps in the solution of oneor more signal processing problems. Fast algorithms for solving Toeplitz systems is the theme of Chapter 11. There is a variety of fast algorithms discussed, the proper choice of which depends on the specific structure of the Toeplitz system at hand (such as whether or not the system is symmetric and whether or not the right-hand vector is arbitrary). The final chapter addresses fast algorithms for Trellis and tree search and includes the Viterbi, Stack, and Fano algorithms. These

Utility meter and submetering system

Abstract: The utility meter is a microprocessor-based circuit using Hall effect electric current sensors to measure power usage by residential and commercial customers. An analog signal from the Hall effect sensor is converted to a digital signal which is fed to the microprocessor for analysis and storage in random access memory. Using a real time clock, the microprocess or determines time of use information which is also stored in random access memory. The memory may be remotely interrogated via a telephone line or serial communication link. If desired, the meter can receive utility usage inputs from other utility meters, such as water, gas, etc. and to fire and intrusion alarms. To effect a submetering configuration useful in apartment complexes, institutional and manufacturing applications, a mutiplicity of meters are multiplexed to a data collection computer which is in turn networked with other data collection computers to a central billing computer.

Voice and data communication system

Abstract: A telephone communication system for transmitting and receiving both voice signals and digital data signals, with no significant distortion to the voice signals and with substantially higher digital data rates than previously could be obtained in comparable systems. The voice signals are digitized, data compressed, and time-division multiplexed with the digital data signals, to produce a composite digital signal that can be transmitted over conventional telephone lines. The system can be selectively configured in a conventional telephone operating mode, in which the system transmits and receives merely the analog voice signals and all of its various digital circuitry elements are bypassed. The system is automatically configured in this conventional telephone operating mode whenever a significant failure in any of its individual units is detected.

Digital servo control system for a data recording disk file

Abstract: A digital servo control system for a data recording disk file receives as input a digital head position error signal (PES) and a digital signal corresponding to the head actuator input signal, and outputs a digital control signal. The control signal is integrated and amplified to provide the input signal to the actuator. The control signal is calculated from estimated values of absolute head position, head velocity and the equivalent actuator input signal required to compensate for constant or very low frequency bias forces. The estimated values are functions of respective predicted values, which in turn are functions of, among other things, constants representing the digital sampling time and physical parameters of the actuator. The updating of the estimated values from the respective predicted values is made with the use of an error term, which is the error between the measured absolute head position and the predicted absolute head position. The predicted absolute head position is made sufficiently accurate that the error term is always less than a selected number of tracks. This permits the digital servo control system to operate during track seeking without counting track crossings so that the system is operable with servo information recorded either in sectors on a data disk or in continuous tracks on a dedicated servo disk.

Modulation system capable of improving a transmission system

Abstract: In a modulation system responsive to a system input signal for supplying an amplifier having nonlinearities with a modulated analog signal to make the amplifier produce an amplified output signal, the system input signal conveys a baseband signal having a predetermined sampling rate for reproduction and is sampled into a sequence of sampled signals having a specific rate higher than the predetermined sampling rate. The sampled signal sequence is converted by a random access memory into a sequence of predistorted signals which compensate for the nonlinearities and which are modulated into the modulated analog signal. Each predistorted signal is adaptively modified at the specific rate with reference to the sampled signals and an additional input signal derived from the amplified output signal. When the sampled signal sequence is sampled at the predetermined sampling rate, the predistorted signal sequence may be produced by interpolating each of the sampled signals at the specific rate. The baseband signal may be either a digital signal or an analog one.

Audio and video digital recording and playback system

Abstract: A microcomputer system for converting an analog signal, such as an audio or video signal representative of sound or video into a digital form for storing in digital form in a highly condensed code and for reconstructing the analog signal from the coded digital form. The system includes reductive analytic means where the original digital data stream is converted to a sequential series of spectrograms, signal amplitude histrograms and waveform code tables. Approximately 100 times less storage space than previously required for the storage of digitized signals is thereby obtained. Additive synthesis logic interprets the stored codes and recreates an output digital data stream for digital to analog conversion that is nearly identical to the original analog signal.

Wideband digital signal distribution system

Abstract: Wideband digital signals, such as video program signals, are distributed to multiple customer locations by providing the wideband digital signals to all customer line interface units in an intermediate selection terminal which is remote from a central wideband signal distribution office. The individual signals are made available to all line interface circuits by way of nonreflectively terminated transmission lines and high-input-impedance signal tapping circuits. Control signals from customer terminals are used at the corresponding line interface circuit to control digital selection of channels for customer use, any number of customers being able to select simultaneously a common one of said transmission lines. Other control signals from the central office are used to limit customer access to all wideband signals.

Skin-pattern recognition method and device

Abstract: A method of authenticating a person by comparing information from a currently taken skin-pattern with stored information from a previously taken skin-pattern is characterised in that the currently taken skin-pattern is produced on a contact surface, an image of the print of the skin pattern on the contact surface is projected onto a photo-detector device (20), the intensity variations of the print image in at least one region thereof impinging on the photo-detector device is assessed in digital form in a multiplicity of different sub-regions of the or each said region to create (in unit 21) a first digital signal train, a second digital signal train is derived from the stored skin pattern information (in store 23) and the first and second signal trains are compared (in 24) to determine the degree of coincidence therebetween, an assessment of the determined degree being used to decide (on indicator 27) whether the currently-taken and stored skin patterns are sufficiently similar to authenticate the person.

Method of digital process variable transmitter calibration and a process variable transmitter system utilizing the same

Abstract: A method of digital process variable transmitter calibration includes the steps of sensing the process variable (PV) to produce an analog output which is converted to a digital signal representation. The digital signal is corrected by a microprocessor using a characterization equation previously individually developed during a manufacturing testing of the process variable transmitter over a predetermined range of environmental stimuli to ascrtain the coefficients for a polynomial in the form of PV=Ao =A1 P+A2 +. . . Ai Pi. Thus, the digital computer produces a process variable representation as a modified digital output. Subsequently, the digital output from the computer is converted to a conventional 4-20 mA analog signal for use as a process control signal. The process variable transmitter apparatus utilizing the aforesaid method includes means for receiving an output from a process variable sensor, an analog-to-digital converter for converting the received output from the sensor to a digital representation, a digital computer, a non-volatile memory for storing an individualized correction equation determined during the manufacturing testing of the transmitter and a digital-to-analog converter for converting the computer output to an analog control signal.

Apparatus for generating an image from a digital video signal

Abstract: An apparatus for generating a high quality image from a digital video signal includes a system for gamma correcting the digital video signal with a digital look up table and for converting the resultant digital signal to an analog video signal. Another circuit generates a triangular wave reference pattern signal and a comparator compares the analog video signal with the triangular wave reference pattern signal to form a pulse-width-modulated signal. A raster scanning print engine producing, for example, a laser beam, scans over a recording medium in accordance with the pulse-width-modulated signal, thereby forming an image of high quality on the recording medium of a print engine. This apparatus can also be used with an analog video signal by first converting the analog video signal to a digital video signal with an analog to digital converter.

Tdm communication system for efficient spectrum utilization.

Abstract: A time division multiplexed (TDM) communication system, which apportions radio frequency communication channels into at least two time slots Voice signals for transmission on this system are analyzed and vo-coded into a digital signal that is transmitted during one or more of the time slots Received messages are recovered from at least one of these time slots and the voice message synthesized from the vo-coded signal In this manner multiple voice messages may be transceived in a time division multiplexed manner on a single narrowband communication channel

Method for reducing effects of electrical noise in an analog-to-digital converter

Abstract: Method for reducing deleterious effects of electrical noise in an analog-to-digital converter wherein both the analog and digital circuitry of the A/D converter are embodied in the same integrated circuit. The method includes sampling an analog input voltage with a first clock signal, generating a second clock signal that is delayed with respect to the first clock signal, and using the second clock signal as a clock for the digital circuitry. In accordance with another aspect of the invention, the method for reducing effects of noise in an A/D converter wherein such noise is generated by a digital decimation filter includes synchronously pipelining the arithmetic operations of the digital decimation filter.

Signal preconditioning for touch entry device

Abstract: A touch entry system employing arrays of emitter (X1...XN, Y1...YN) and detector (X1ʹ...XNʹ, Y1ʹ...YNʹ) opto devices located around the periphery of the irradiated field (12) detects intrusion of an opaque element (18) such as a stylus within the field. The detector analog output is converted to a digital signal for input into a microprocessor (80). Digital signals input into the microprocessor (80) can vary due to inconsistencies in conventional opto devices (101, 102, 103). A programmable amplifier (40) responsive to the microprocessor (80) preconditions the analog signals prior to analog to digital conversion to bring all digital signals corresponding to the unblocked emitter beam condition within a normalized range before input into the microprocessor.

Digital method and system for reproducing analog data

Abstract: There is disclosed herein a method of and system for reproducing an analog signal using digital techniques. The system includes means for encoding the analog signal in digital form and means for decoding the encoded analog signal. The encoding means includes means for detecting the upper bandwidth limit of the input analog signal during each of a plurality of successive sample intervals. Means coupled to the detecting means are included for sampling the input analog signal at a sampling rate determined in accordance with the detected upper bandwidth limits to derive a series of voltage levels which together define a sampled approximation of the input analog signal. Means are coupled to the sampling means for converting each voltage level and the sampling rate at which such voltage level was derived into digital signals. Also included are means for detecting when the input analog signal is at substantially a zero level, means for developing a digital indication of the length of time the signal is at such level and means for combining the digital indication with the digital signals to develop a digital representation of the input analog signal. The decoding means includes means for sequentially retrieving the digital signals, means coupled to the retrieving means for converting the digital signals into the sampled approximation of the input analog signal and a low-pass filter coupled to the converting means having a cut-off frequency determined in accordance with the encoded sampling rate for filtering the sampled approximation to reproduce the input analog signal.

Digital transmisson including add/drop module

Abstract: In a transmission system, adding and/or dropping any one or more of a plurality of digital signals of one or more digital transmission bit rates is facilitated by employing a un- lque transmission signal in which data words associated with Individual digital signals are arranged in prescribed groups. The transmission signal data word groups are obtained by formatting the individual digital signals to be combined into a unique channel frame format common to all of the digital signals and by employing a unique one-step multiplexing process to insert digital words from the channel frames into the group of data word positions in the transmission signal associated with the particular signal being combined. Consequently, digital signals may be added to the transmission signal by formatting them into the common channel frame format and, then, inserting the digital words therefrom in the one-step multiplexing process into an associated group of data words positions in the transmission signal. Digital signals are dropped from the transmission signal by extracting associated groups of data words from the transmission signal, identifying the corresponding channel frames and deformatting the data bits from channel frames of corresponding digital signals being reconstructed.

Monolithic random digital noise generator

Abstract: A random digital signal generator circuit responsive to a clock signal from a block signal source for outputting a sequential series of logic signals. The circuit comprises a clocked flip-flop that provides a signal at its output terminal that has a value corresponding to the state of its input signal until a subsequent clock signal is received. An array of oscillator signal generators is provided with each oscillator signal generator operating at a different frequency. An EXCLUSIVE-OR network means having an array of input terminals has each input terminal of the EXCLUSIVE-OR network coupled to the output terminal of a corresponding oscillator signal generator. The EXCLUSIVE-OR network provides a random output signal at its output terminal. The EXCLUSIVE-OR network means output terminal is coupled to the flip-flop input terminal. The flip-flop responds to each the clock signal to sample the state of the random output signal from the EXCLUSIVE-OR network. The flip-flop stores and couples the state of the random output signal to the flip-flop output terminal with each successive clock signal.

Method of, and demodulator for, digitally demodulating an ssb signal

Abstract: An SSB signal demodulator comprising an analog bandpass filter for band-limiting such signal, an analog-to-digital converter 20 for digitizing the band-limited signal, and a pair of quadrature related decimating filters (28, 29) for deriving quadrature related decimated signals therefrom which are applied to a Hilbert transform pair (30, 31). The upper or lower sideband signal is obtained by taking the sum or difference of the outputs of the Hilbert transform pair, and the resulting digital signal is reconverted to an analog signal. By using a decimation factor which is an odd numbered integer greater than 1, the periodic transfer function of the demodulator has alternate passbands and stopbands. This relaxes the performance requirements of the analog filter and of the Hilbert transform pair, and greatly enhances the adjacent channel selectivity of the demodulator.

Digital delay generator for sonar and radar beam formers

Abstract: This invention relates to apparatus and a method of controlling the amount of delay or phase-shift which is applied to a signal received at or transmitted from each transducer in a multi-transducer antenna to produce a beam directed at a specific target point. For each transducer a first look-up table is used for storing first digital words representative of the included angle between the lines joining the target to a reference point, and the same reference point to a transducer. A second look-up table is associated with the first look-up table for each transducer, and stores second digital words representing delay or phase-shift control signals corresponding to ranges of the target relative to the reference point for each of said first digital words. Each first look-up table is addressed with an address signal representing the direction of the line from the reference point to the target, to obtain a corresponding first digital word. Each second look-up table is addressed with a corresponding first digital word combined with a signal representing the range of the target to obtain a corresponding second digital word. A signal received or transmitted by the corresponding transducer is delayed or phase-shifted an amount represented by the second digital word.

Wide band, complex microwave waveform receiver and analyzer, using distributed sampling techniques

Abstract: A microwave signal receiving apparatus comprises a delay line for distributing a microwave signal, samplers for sampling the signal spatially along the delay line and producing analog samples, analog-to-digital converters for converting the analog samples to digital samples, and digital memories associated with each converter for storing the digital samples.

Apparatus for automatically inspecting electrical connecting pins

Abstract: An automatic pin inspection 100 apparatus and method inspects a plurality of pins 27 that are arranged in a predetermined configuration such as parallel rows and converts the image of the pins to a digital signal for application to a computer system 11, 17 The digital signal is compared with a known reference stored in a memory within the digital computer system 11, 17 and units 5 that do not meet specified tolerances are rejected A conveyer mechanism 10 ensures the automation of the process A centering technique is implemented and compensates for the jittering due to the movement of pins to ensure proper alignment of the image prior to the comparison being made

Method of digital signal transmission

Abstract: A modulation method capable of high-speed or high-quality digital data transmission under a multipath fading transmission line such as a radio transmission in an urban area is a type of differential coding phase modulation and residues in the fact that the rate of change of phase varies, or the phase is discrete, but does not employ a phase transition waveform of a constant value in a time slot which is a smallest unit for transmitting one symbol of data as in conventional methods Phase transition waveforms in respective time slots which are spaced apart from each other by prescribed time slots are identical varying waveforms or discrete waveforms, and entirely shifted from each other by an amount according to the data transmitted A detecting method employed is a differential detection method using a delay line for delaying a signal for a time corresponding to the prescribed time slots In the presence of multipath propagation, a plurality of kinds of detected outputs are produced according to the multipath propagation, and the detected outputs are combined by a filter after the differential detection, producing a diversity effect for improving bit error rate characteristics This digital signal transmission method is capable of multiphase transmission and can increase spectrum utilization efficiency

Transmitter for transmitting on a two-wire transmitting line

Abstract: A transmitter for repeatedly transmitting a measured value in the form of a digital signal through a two-wire transmission line, includes a receiving unit for receiving a digital command signal from a communicator through the two-wire transmission line, and a processor for sending out a response signal in response to the command signal upon reception thereof. The measured value is sent using a newest measured value after repetitive transmission of the measured value is interrupted. The measured value is transmitted from the transmitter by a change in current supplied to the two-wire transmission line, and reception of the command signal is performed by a change in interline voltage of the two-wire transmission line.

High resolution pipelined digital-to-analog converter

Abstract: A high resolution pipelined digital-to-analog converter is disclosed having at least one switching circuit for conveying charge to at least one conversion capacitor upon receipt of a digital signal during the first half of a clock cycle. Additional switching circuits are provided for transferring the charge from the conversion capacitors to a feedback capacitor during the second half of the clock cycle. Also provided is a circuit for discharging an analog output from, and preventing the charging of, the feedback capacitor during the first half of a succeeding clock cycle. In a preferred embodiment, the pipelined digital-to-analog converter comprises a first plurality of electrical circuits having at least one feedback capacitor and a plurality of conversion capacitors adapted for accepting digital and analog inputs, wherein the ratio of the feedback capacitance to each of the conversion capacitances is substantially independent of the resolution of the converter. A second plurality of electrical circuits is also provided which is operable to delay at least one bit of the digital signal to one of the first plurality of electrical circuits. The digital-to-analog converter is operable to allow the number of n-bit digital words converted by the converter to be independent of the resolution of the converter.

Automatic setup system for controlling color gain, hue and white balance of TV monitor

Abstract: A television monitor control apparatus has a signal processor supplied with a standard television signal, a color cathode ray tube supplied with a processed color signal obtained from the signal processor, a reference signal memory for storing at least a set of reference signals and a signal control circuit connected to the signal processor and the reference signal memory for adjusting the operation of the signal processor on the basis of the standard television signal and a reference signal from the memory.

Digital data recording and reproducing method

Abstract: In a digital data recording and reproducing method, a digital data sequence is divided into every 8-bit digital data, when the divided 8-bit digital data is encoded to 14-bit code, an 8-bit digital data wherein value of DSV is limited in a predetermined range is selected from two codes corresponding to 8-bit digital data, and in an encoding process, the number of bit "0" which is inserted between two bits "1" in the code sequence is restricted to a number of from one to eight, and hence, DC component in the code sequence is eliminated.

Apparatus for reproducing a digital signal

Abstract: In an apparatus for reproducing a recorded digital signal and suitable for use in a data recorder (1), error detecting signals are generated (14) for respective reproduced header portions of a main data area and a sub-data area formed in each track, the error detecting signals are counted (30) for a predetermined period, and the counted value is compared with a predetermined value. A data error condition is determined in accordance with the comparison result, so that it is possible to simplify the circuit arrangement and detect an error condition in the recorded digital data.