Showing papers on "Digital signal published in 1990"

Analog & digital signal processing

Abstract: The Fourier series in spectral analysis and function approximation the Fourier transformation and generalized signals the Laplace transformation and some of its applications analogue signal processing systems digitization of analogue signals discrete signals and systems design of digital filters the fast fourier transform and its applications stochastic signals and power spectra finite word-length effects in digital signal processors linear estimation and adaptive filtering.

On the detection and classification of quadrature digital modulations in broad-band noise

Abstract: Optimal and suboptimal decision rules for the detection of constant-envelope quadrature digital modulations in broadband noise are derived and analyzed. The effect of various stochastic models for the carrier phase is examined in detail, while no epoch or frequency uncertainty is assumed. The delay-and-multiply type of detector is considered. A new binary/quadrature phase shift keying (BPSK/QPSK) classifier is compared to the more traditional ad hoc techniques of a square-law classifier and a phase-based classifier (weighting on the phase histogram). The new classifier is derived by approximating the likelihood-ratio functionals of phase-modulated digital signals in white Gaussian noise, hence is named the quasi-log-likelihood ratio (qLLR) rule. It is shown analytically that its performance is significantly better than that of intuitively designed phase-based rules or the conventional square-law classifier. >

Method and apparatus for pixel non-uniformity correction

Abstract: An apparatus for reading and correcting an image including: a sensor which receives light and converts it to electrical signals; a digitizing unit to convert the analog image signal to a digital signal; a calibration unit to capture calibration data for each pixel under known illumination conditions and to produce individual correction values for each pixel and a correction unit comprised of a look-up table addressed by both the digital image signal and the correction values which corrects the digital image data.

Method for transmitting a desired digital video or audio signal

Abstract: The present invention is a method for transmitting a desired digital video or audio signal stored on a first memory of a first party to a second memory of a second party. The method comprises the steps of transferring money via a telecommunications line to the first party from the second party. Additionally, the method comprises the step of then connecting electronically via a telecommunications line the first memory with the second memory such that the desired signal can pass therebetween. Next, there is the step of transmitting the desired digital signal from the first memory with a transmitter in control and in possession of the first party to a receiver having the second memory at a location determined by the second party. The receiver is in possession and in control of the second party. There is also the step of then storing the digital signal in the second memory.

System transmitting and receiving digital and analog information for use in locating concealed conductors

Abstract: An improved locator system is provided which transmits digital and analog information over an electromagnetic field that is radiating from an underground source. The locator system includes a transmitter that modulates its output signal by turning its output signal on and off in response to a sequence of digital words. The transmitter also modulates an analog signal onto the transmitted signal. The modulated analog signal can include an audio frequency or voice signal. The improved locator system also includes a receiver that senses and detects the transmitted digital or analog signal impressed on the radiated electromagnetic field. The receiver also demodulates the transmitted audio frequency signal and provides an audio output signal to an operator.

Analog and Digital Signal Processing

Abstract: From the Publisher: Provides well balanced, detailed coverage of the techniques of signal processing in both the analog and digital domains and the ways in which they are linked in practical applications. Topics include spectral analysis of continuous and discrete signals, analysis of continuous and discrete systems and networks using transform methods, design of analog and digital filters, digitization of analog signals, power spectrum estimation of stochastic signals, the fast Fourier transform algorithms, finite word-length effects in digital signal processors and linear estimation and adaptive filtering.

Quadrature amplitude modulation communication system with transparent error correction

Abstract: In a multi-level QAM communication system, Reed-Solomon encoders and Reed-Solomon decoders are employed for error correction purposes. The phase ambiguity of the received signal is eliminated with differential coding. The multi-level QAM communication system utilizing n bits ("n" being an integer) QAM signal having 2 n signal points, comprises: a quadrature differential encoder/decoder unit for differentially encoding/decoding n pieces of input digital signal series to produce n pieces of differentially coded signal series; an error correction unit including a Reed-Solomon encoder and a Reed-Solomon decoder, provided inside the quadrature differential encoder/decoder unit along a signal processing path of the input digital signal series, for error-correcting the n pieces of differentially-coded signal series by utilizing at least one of the digital signal series with employment of a Reed-Solomon code; and, a QAM modulator/demodulator unit for QAM-modulating/demodulating n pieces of error-corrected signal series so as to produce 2 n QAM signals.

Programmable hybrid hearing aid with digital signal processing

Abstract: Programmable hybrid hearing aid with digital signal processing comprising a main section (1) which can be inserted in the meatus (6). The main section (1) comprises an open connection between the ear opening and an inner portion of the meatus (6), providing an acoustic transmission channel with low-pass characteristic and resonant amplification. The main section further comprises an electroacoustic transmission channel based on digital signal processing and a signal processor (DSP) and with possibility for suppressing a possible acoustic signal feedback through the acoustic transmission channel. A variant of the hearing aid is provided with a microphone (M1) and the feedback signal is suppressed by digital filtering. Another variant of the hearing aid employs two microphones (M1.M2). and the feedback signal may then be suppressed by phasing out before the digital signal processing, while the digital signal processing also comprises cancellation of the feedback signal in case of high gain. A number of response functions are stored in a memory (RAM2) in a control unit and is freely chosen by the user in regard of adaption to hearing function and acoustic environment. All the electronics of the electroacoustic channel in the hearing aid is implemented as a monolithic integrated circuit (3) in CMOS technology.

Method and apparatus for digitally processing a high definition television augmentation signal

Abstract: A method and apparatus for digital encoding are described for compressing the augmentation channel signals (chrominance and luminance signals for panel information and high frequency luminance and line difference signal) so that this information can be transmitted in a 3 MHz wide RF channel using a digital transmission scheme such as QPSK. Analog signal components are sampled and converted to digital signals. Each of the signals is fed into a separate coder which reduces the number of bits/pixel required to reconstruct the original signal. Compression is achieved by quantization and removal of redundancy. The compression scheme is based on the use of DCT together with VLC. Each augmentation signal has its own coder, which is adapted to the unique statistics of this signal.

System for locating concealed underground objects using digital filtering

Abstract: A locating system has its performance enhanced by the use of digital filtering. The locating system may include a transmitter for transmitting an electromagnetic signal from a concealed object. The locating system may also use electromagnetic signals from existing electromagnetic sources unrelated to the locator system. A receiver is provided for receiving a selected electromagnetic signal. The signal is subsequently converted from an analog signal into a digital signal and subjected to digital filtering. The resulting digital signal is then processed to provide location information about the concealed object.

Digital audio carrying extra information

Abstract: A new technique is proposed which makes possible the inaudible addition of extra information to an audio signal. Full compatibility with present-day transmission and reproduction systems is guaranteed, as the resulting signal remains in the same format. The extra information can be retrieved by the use of additional signal processing. The technique of adding and retrieving extra information is described, and applications are presented. Special attention is given to the so-called 4-2-4 coding, as the technique presented offers a very promising scheme for such a coding. >

Speech selective automatic gain control

Abstract: An automatic gain control circuit uses a speech recognizer to obtain smooth automatic gain control. An analog audio input signal is converted to a digital signal by an analog-to-digital converter and delayed by a delay circuit. A frame power (or alternatively, rectified peak amplitude) detector determines the power of each frame (or alternatively, the rectified peak amplitude) of the audio input signal, after applied to the A/D converter. A linear-to-log converter converts those values to a logarithmic form (for gain control over a broad range of values). A detected speech smoothing circuit smooths the variation in the values determined by the frame power (or peak amplitude) detector. A summer subtracts the output of the detected speech smoothing means from a fixed reference level, and thus obtains an error signal from the desired reference. A gain smoothing circuit smooths the resulting error signal (which is the logarithmically-shaped gain signal). A logarithm-to-linear converter converts the logarithmic gain signal to a linear form; and a multiplier multiplies the input signal by this smoothed gain. In accordance with the invention, a speech recognizer determines whether the audio input signal represents speech. An output of the speech recognizer is used to enable the detected speech smoothing circuit and the gain smoothing means when the audio input signal represents speech. Thus AGC is not used until it is required (i.e., when speech is present).

Dsp based radio with diminished power requirements

Abstract: A radio (100) having two signal processing paths, one including a digital signal processor (104) that consumes a relatively large amount of power and one including a signal processor (106) that consumes a relatively small amount of power. The low power processor (106) operates to monitor for broadcast signals of interest. Upon detecting such a signal, the low power processor (106) enables the digital signal processor (104) to facilitate proper signal processing.

Digital signal encoding apparatus

Abstract: A digital signal encoding apparatus in which input digital signals are divided into a plurality of frequency bands so that the bandwidth of each frequency band will be greater the higher the frequency band, the allowable noise level is set for each frequency band on the basis of the energy value of each frequency band, and components of each frequency band are quantized with the number of bits consistent with the level difference between the energy of each frequency band and the preset allowable noise level. The output information volume following the quantization is detected and the number of bits of allocation for quantization is corrected in dependence upon the error between the detection output and the target value to render the information volume constant over a predetermined time period to enable bit rate adjustment or bit packing with lesser signal deterioration by a simplified construction.

Subscriber unit for wireless digital subscriber communication system

Abstract: A subscriber unit for wireless communication with a base station in a wireless subscriber communication system includes a FIR chip, a DIF (digital intermediate frequency) chip, a single processor chip and a radio. The processor chip transcodes a digital voice input signal to provide digital input symbols; demodulates an output signal received from the base station to provide digital output symbols; and synthesizes a digital voice output signal from the digital output symbols. The FIR chip FIR filters the digital input symbols and generates timing signals for timing the transcoding and synthesizing operations in the processor chip. The DIF chip digitally synthesizes a digital intermediate frequency signal by direct digital synthesis (DDS) and modulates the digital intermediate frequency signal with the filtered input symbols to provide a modulated intermediate frequency input signal. The radio further processes the modulated input signal for transmission to the base station.

GRAPE: a CASE tool for digital signal parallel processing

Abstract: The use of computer-aided software engineering (CASE) tools for stream-oriented real-time digital signal processing (DSP) applications is discussed. These applications are characterized by a continuous stream of data samples or a continuous stream of blocks of data samples arriving at the processing facility at time instances completely determined by the outside world. An overview of existing development tools for DSP is given. The CASE tool GRAPE (graphical programming environment), which allows for easy programming, compiling, debugging and evaluating of high-frequency real-time DSP systems, is presented. Its main distinctive feature is that the tool spans the whole design process, ranging from analysis over simulation and emulation up to implementation on general-purpose DSP multiprocessors or integration on an application-specific integrated circuit (ASIC). The DSP multiprocessor can be the target hardware or can be used for real-time emulation or accelerated simulation of an ASIC. >

Electroencephalic neurofeedback apparatus and method for bioelectrical frequency inhibition and facilitation

Abstract: An improved method and apparatus for displaying and either inhibiting or promoting selected bioelectrical frequencies emitted by a living organism. The method includes the steps of detecting an analog bioelectrical signal, converting the signal to discrete digital signals representing corresponding frequencies and numerically analyzing the digital signals to determine the different bioelectrical frequencies emitted by the organism. Furthermore, a threshold amplitude associated with a selected digital signal can be established an auditory or visual signal can be sent to the organism to indicate whether the bioelectrical frequency under study is within or outside the threshold amplitude. With this information the organism can be taught to inhibit or facilitate the bioelectrical frequency. The apparatus comprises a pair of electrodes, an analog signal amplifier, an analog to digital converter, a selector to select a frequency of interest, a display monitor, and a computer to distinguish the digital signals as different frequencies, display the frequencies, and determine when the frequency is falling inside or outside a predetermined range. Also, a magnetic medium recording device is used to capture data. Finally, a lighting or sounding circuit is used to tell the organism whether the frequency under study is being inhibited or facilitated.

Burst demodulator for establishing carrier and clock timing from a sequence of alternating symbols

Abstract: OF THE DISCLOSURE In a burst demodulator, an APSK burst signal containing a preamble of alternating "1" and "-1" symbols, followed by a data field is received and quasi-coherently demodulated into a baseband complex signal, which is converted to digital form such that each symbol of the complex signal yields N digital samples, with N being selected such that at least one of the N digital samples is closest to a signal point of the burst signal. A clock recovery circuit is responsive to the arrival of the burst for estimating the symbol timing of the burst signal from digital samples of the preamble. A digital sample is extracted from every N samples of the preamble in response to the estimated symbol timing so that it is most likely to be closest to the signal point. A carrier recovery circuit responds to the estimated symbol timing by estimating the carrier frequency and phase of the burst signal from the extracted digital samples to produce a complex carrier signal, which is multiplied with the extracted digital samples to recover the original signal. Memories are preferably provided to store the received burst signal. By repeatedly reading the preamble from the memories, the same symbols of the preamble can be used for clock timing and carrier phase recovery operations.

Power line carrier controlled lighting system

Abstract: A power line carrier controlled lighting system connected to an AC power line. The system has: at least one motion detector for detecting at least one predetermined parameter in a detection zone of the motion detector, the motion detector outputting at least one detect signal in response to the predetermined parameter; at least one transmitter for transmitting during a first predetermined time period a power line carrier signal on the AC power line indicative of the detect signal; at least one receiver receiving the power line carrier signal on the AC power line and outputting at least one control signal indicative of the power line carrier signal during a second predetermined time period, the receiver having an AGC circuit for providing substantial noise immunity so that the receiver reliably recognizes the power line carrier signal; and at least one light in a predetermined area and having at least two different light intensity levels, the light having a switching circuit for switching between the light intensity levels, the switching circuit being activated by the control signal. The power line carrier signal is a digital signal and the AGC circuit determines a logical one/zero reference level relative to noise on the power line.

Electronic still camera using variable-length data compression for storing still image signals

Abstract: An image pick-up section generates an electronic still image signal. An A/D conversion section converts the electronic still image signal generated by the image pick-up section into a digital signal. A data compressing section causes variable-length encoding data compression to the digital signal obtained by the A/D conversion section so as to obtain compressed image data. A recording section records the image data compressed by the data compressing section in a recording medium having a predetermined recording capacity. A calculating section calculates an estimated count of electronic still images which can be recorded in the recording medium in accordance with quantitative data associated with the image data recorded in the recording medium by the recording section and quantitative data associated with the recording capacity of the recording medium. An indicating section indicates the estimated count of the recordable electronic still images calculated by the calculating section.

Digital transmission system, transmitter and receiver for use in the transmission system, and record carrier obtained by means of the transmitter in the form of a recording device

Abstract: The transmitter (1) in a digital transmission system derives from a wideband digital signal SBB having a sample frequency Fs a second digital signal appearing on its output (7), which signal comprises successive frames, each frame being made up of information packets (IP) each having a length of N bits. The number of information packets (B) in a frame is determined as follows: If P in the formula is an integer, where BR is the bit rate of the second digital signal, ns is the number of samples of the wide-band digital signal, SBB in which the information, after having been converted into the second digital signal, is present in one frame of the second digital signal, the number of information packets B in a frame is equal to P. If P is not an integer, B is equal to P′ for a number of frames, P′ being the next lower integer following P, whereas B for the other frame is equal to P′+1, in such a way that the average frame rate of the second digital signal is substantially equal to Fs/ns. A frame comprises a first frame portion (FD1), a second frame portion (FD2), and a third frame portion (FD3). The first frame portion contains synchronising information and system information. The second frame portion contains allocation information, and the third frame portion contains samples of and, if applicable, scale-factor information for the second digital signal.

Integrated digital signal processor/general purpose CPU with shared internal memory

Abstract: An integrated data processing platform for processing a digital signal that includes a general purpose processor and a digital signal processor (DSP) module. The DSP module recovers digital data from a digital signal utilizing a sequence of DSP operations selected by the general purpose processor. The general purpose processor processes the digital data recovered by the DSP module, but is also available to perform general purpose tasks. A shared internal memory array selectively provides information to the DSP module and to the general purpose processor. The information stored in the internal memory array includes operands utilized in the execution of the DSP algorithm and selected instructions and data utilized by the general purpose CPU either for controlling the execution of the DSP algorithm or for executing its own general purpose tasks. While in many applications the data processing system will include an analog front end that converts a modulated input signal received on an analog transmission channel to a corresponding digital signal for processing by the data processing system, the data processing system may also receive the digital signal directly from a digital source.

Digital receiver for spread-spectrum signals

Abstract: The receiver contains a correlator (TIC) for the correlation of the received signal with a reference code (R(k)) and a digital signal processor for evaluating the results of the correlation. The correlator is constructed as digital, time-integrating, multistage correlator (TIC), the individual stages (Kl to KN) of which are connected on the one hand to a digital delay line (17) fed with the reference code (R(k)) and to which on the other hand a digital signal (S(k)) recovered from the received signal is applied, to length (D) of the delay line (17) being adapted to the maximum expected impulse response to the transmission channel.

Analog-to-digital converting unit with broad dynamic range

Abstract: An analog-to-digital converting unit comprises an analog level varying circuit having a plurality of gains and varying a magnitude of an analog input signal for producing a plurality of analog output signals different in magnitude from one another with the respective gains, a plurality of analog-to-digital converting circuits respectively supplied with the analog output signals and producing a plurality of digital code signals, respectively, a controlling circuit supplied with two of the digital code signals and calculating a difference therebetween for producing a first control signal indicative of varying one of the digital code signals in value so as to be equal in value to the other digital code signal, a calculating circuit responsive to the first control signal and causing one of the digital code signals to be varied in value for producing a candidate of a digital output signal, and an output circuit coupled to one of the analog-to-digital converting circuits and to the calculating circuit and supplying the digital output signal to the output node. Since the value of the input analog signal is retrieved from the digital code signal on the basis of the difference, the analog-to-digital unit is free from any secular changes and any variation of operational ambient.

Method and device in a digital communication network

Abstract: The invention relates to a method and a communications system (150) for local dynamically connectable digital synchronous nous multiplex or non-multiplex or asynchronous service networks used as a common service resource (220) for three or more switching units (200; 210), comprising a wide area service network with at least one central station (10), and one or several peripheral stations (19) within an area/space/region, said common service resource being adaptively shared according to the traffic needs between said switching units. According to the invention information is communicated through said communications system (150) for each connected digital signal (100) to be communicated through said service network, in such a way that said communication of digital signals (100) individually for each time sequence corresponds to a transparent communication, irrespective of each sequence of information of digital signals (100) being communicated through said system or not.

Communication system and apparatus using chip signals

Abstract: There are provided a communication system and an apparatus for modulating a communication signal into a chirp signal and executing the communication. In the system, a signal to be transmitted is input, a predetermined analog pattern signal is added to the input signal and is pulse position modulated, the modulated signal is converted into the chirp signal, and the chirp signal is output onto a transmission path. The converted chirp signal can be also converted into an optical signal and the optical signal can be also output onto the transmission path. After the analog or digital input signal was pulse position modulated, by converting the modulated signal into the chirp signal, the analog signal can be also transmitted and received as a chirp signal. Thus, the communication reliability can be assured without being influenced by disturbance noises or irrespective of a limitation of a transmission electric power of the transmission path.

All digital phase locked loop

Abstract: An all-digital phase-locked loop (PLL) for synchronizing an output clock signal with a reference clock signal. The PLL has a multiple-tap, digital delay chain in its forward path for delaying the output clock signal, which delay chain is controlled by a digital number stored by a counter in its feedback path. A phase detector in the feedback path provides LEAD and LAG signals, the status of which indicates whether the output clock signal leads or lags the reference signal. In response to the LEAD and LAG signals, a digital sequencer in the feedback path generates the digital number and stores it in the counter. The digital sequencer changes the digital number until the state of the LEAD and LAG signals reverses, and then returns the counter back to its state prior to LEAD and LAG reversal, for synchronism. The digital sequencer also causes a phase reversal of the output signal where the number of delay taps needed for synchronism is large. As a result of the all-digital circuitry, use of unstable prior art voltage-controlled oscillators is obviated.

Sound activated device and method

Abstract: A smoke alarm activated device includes a sound receiver and signal converting device for receiving a sound wave analog signal emitted from a smoke alarm in response to the sensed presence of smoke The signal is received and converted into a digital signal containing the informational characteristics contained within the transmitted sound wave The digital signal is detected in a first time period which first time is identical to the time period in which the sound wave is generated The absence of the digital signal in a second time period is detected, which second time period is identical to the time period in which the detected sound wave is absent An output control signal is generated when the presence of the digital signal is detected in the first time period and the absence of the digital signal is detected in the second time period A device is activated in response to the output control signal

Delta-sigma modulation analog to digital converter

Abstract: A delta-sigma modulation analog to digital converter for converting an analog input signal to a digital output signal. The converter includes an input circuit for receiving the analog input signal, a clock generator for generating a very high frequency clock signal with first and second phases, a first switching circuit coupled to the input circuit for modulating the analog input signal with the very high frequency clock signal, an integration circuit coupled to the first switching circuit for integrating the modulated input signal and generating a noise signal, a second switching circuit coupled to the integration circuit both for demodulating the integrated modulated input signal and modulating the noise signal with the very high frequency clock signal, a quantizing circuit coupled to the second switching circuit and responsive to the demodulated input signal and the modulated noise signal for generating the digital output signal including a separable portion corresponding to the modulated noise signal and a feedback circuit coupled between the quantizing circuit and the integration circuit both for generating a feedback signal corresponding to the digital output signal and feeding the feedback signal to the integration circuit.