226 results about "Digital transmission systems" patented technology

This invention relates to a wireless digital transmission system for loudspeakers comprising:compression means for the file representing the digital audio signal of the “compact disc” type, a transmission device comprising means of converting this compressed signal into a series signal moving by packets going to a modulator circuit with phase quadrature and means of transmitting the signals exiting the modulator circuit with phase quadrature to the domestic network for feeding electricity;a receiving device comprising means of connecting to this domestic network and of extracting from the feed electrical signal, by a demodulator with phase quadrature, data packets moving the digital audio signal to convert it into a parallelized digital signal sent to a decompression circuit;means of converting the decompressed digital signals into an analog signal intended to feed a loudspeaker after adequate amplification.

A flexible digital transmission system that improves upon the ATSC A / 53 HDTV signal transmission standard. The system includes a digital signal transmitter for generating a first Advanced Television Systems Committee (ATSC) standard encoded 8-VSB bit stream and, for generating an encoded new robust bit stream for transmitting high priority information bits, wherein symbols of the new bit stream are capable of being transmitted according to a transmission mode including: a 2-VSB mode and a 4-VSB transmission mode. The standard 8-VSB bit stream and new bit stream may be simultaneously transmitted over a terrestrial channel according to a broadcaster defined bit-rate ratio. The transmission system includes a control mechanism for generating information needed for encoding robust packets at a transmitter device. It also includes a mechanism for encoding control parameters and multiplexes the generated information with the standard and robust bit-streams for transmission. A receiver architecture is additionally provided to decode standard and robust bit-streams transmitted by the transmitter device.

The present invention is a method and a system for screening offensive material in a digital transmission. A digital transmission including at least one embedded offensive material code associated with a portion of the digital transmission is received. The digital transmission is monitored for the offensive material code. The digital transmission is modified based on the embedded offensive material code and an offensive-material control input, and the modified digital transmission is played.

A digital Vestigial Sideband (VSB) transmission system and enhanced data multiplexing method are disclosed. When 1 / 2 enhanced data coded at a rate of 1 / 2 and 1 / 4 enhanced data at a rate of 1 / 4 are transmitted, timing jitter in Moving Picture Experts Group (MPEG) of Vestigial Sideband (VSB) receiver can be reduced and the size of input buffer in Moving Picture Experts Group (MPEG) decoder of the Vestigial Sideband (VSB) receiver can be reduced by multiplexing the 1 / 2 enhanced data packet and the 1 / 4 data packet at predetermined intervals. Multiplexing the 1 / 2 enhanced data packet and the 1 / 4 data packet by grouping increases the reception performance of the 1 / 4 enhanced data. Multiplexing the 1 / 2 enhanced data packet and the 1 / 4 data packet alternatively reduces the Moving Picture Experts Group (MPEG) timing jitter in the Vestigial Sideband (VSB) receiver and increases the reception performance of the 1 / 4 enhanced data.

A digital VSB transmission system that is able to send supplemental data along with MPEG image / sound data is enclosed. The system initially encodes the supplemental data symbol to generate a parity bit, and it multiplexes the parity bit with a predefined sequence and transmits the multiplexed data to a receiver. The system is compatible with the existing ATSC 8T-VSB receivers that are already on the market. It can have advantages over the other type of VSB transmission systems that transmit only the predefined sequence. In addition, the system according the to the present invention results a improved robustness against ghost and noise signals in a channel compared to systems using only the ½ rate convolutional encoding.

A method of reducing speech delay and improving speech quality in digital transmission systems by implementing a single coder-decoder (codec) for an entire speech path from a calling party to a called party. The method is applicable to calls between mobile subscribers and between a mobile subscriber and an H.323 client terminal in a data network. After obtaining location information for the called party, an indication of a requested codec is sent from the calling party to the called party utilizing Integrated Services Data Network User Part (ISUP) or Primary Rate Interface (PRI) out-of-band signaling during call setup. If the called party supports the requested codec, a confirmation of the requested codec is sent from the called party to the calling party. A speech path is then established between the parties, and a single codec translation is performed for the entire speech path. If the called party does not support the calling party's codec, but the serving MSCs for both parties support the calling party's codec, the calling party's codec is utilized all the way to the called party's serving MSC. One additional codec translation is then performed in the called party's serving MSC to convert to the codec supported by the called party.

A digital VSB transmission system and enhanced data multiplexing method are disclosed. When ½ enhanced data coded at a rate of ½ and ¼ enhanced data at a rate of ¼ are transmitted, timing jitter in MPEG of VSB receiver can be reduced and the size of input buffer in MPEG decoder of the VSB receiver can be reduced by multiplexing the ½ enhanced data packet and the ¼ data packet at predetermined intervals. Multiplexing the ½ enhanced data packet and the ¼ data packet by grouping increases the reception performance of the ¼ enhanced data. Multiplexing the ½ enhanced data packet and the ¼ data packet alternatively reduces the MPEG timing jitter in the VSB receiver and increases the reception performance of the ¼ enhanced data.

A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

To mitigate the effects of non-linear amplification in a digital transmission system employing a multi-carrier multiplexing communications technique, such as orthogonal frequency division multiplexing or discrete multi-tone, predistortion of an input signal to a power amplifier with a non-linear transfer characteristic is performed in the frequency domain by modifying frequency-domain symbols used to modulate individual sub-carriers. The frequency-domain symbols are modified in a manner that compensates for the amplifier's non-linear transfer characteristic.

A method and system for decision feedback equalization for digital transmission systems is provided. Low-power integrating decision feedback equalization with fast switched-capacitor paths are used, for suppressing intersymbol interference (ISI) due to past data symbols. The decision feedback equalization involves performing current-integrating decision feedback equalization at low-power employing a fast capacitively coupled feed-forward path at the output of a current-integrating buffer and inducing voltage changes by charge redistribution via coupled switching capacitors, and performing a voltage digital-to-analog conversation to determine a feedback coefficient as a coupling voltage. Then switches are reset to a pre-charge coupling voltage in the buffers to eliminate residual ISI caused by signal history, thereby achieving current integrating buffering with switched-capacitor feedback during the integration, and the capacitive switches are triggered by previous symbols.

Disclosed herein are various embodiments of methods, systems, and apparatus for encoding OFDM packets in a digital communication system. In one exemplary method embodiment, LDPC codewords in an IEEE 802.11 wireless transmission are shortened, decreasing the iterations necessary to insure accurate communications. The codewords are shortened by adding known bits in predetermined locations in the last data symbol of a packet.

The invention discloses a magnetic resonance multichannel digital transmission system, including a multipath data multiplexing unit, a data encapsulation unit, a high speed serial transmission unit, a fiber transmission unit, a fiber reception unit, a high speed serial reception unit, a data unpacking unit and a multipath data demultiplexing unit. Multichannel magnetic resonance digital signals after sampling and front-end processing are subjected to multiplexing according to magnetic resonance data word lengths, obtained data of all channels are polled as a frame, and frame synchronization codes required in demultiplexing are inserted at a frame header, and thus the real-time property and the integrity of magnetic resonance data are ensured. Synchronous clock information is inserted in line coding, and thus transmission of magnetic resonance data and clock can be completed using a single channel, and system equipment is simplified. FPGA chip programming realization is used to improve the system integration degree. The invention also provides a magnetic resonance multichannel data transmission method.

Frequency synchronization bursts are detected for a radio communication system such as a GSM cellular telephone network using a two stage correlation process. A first unit performs a first set of correlations to identify receipt of the frequency synchronization burst. A preliminary identification is declared when the moving average of the first set of correlations, normalized for received power, exceeds a threshold value for a number of contiguous samples. After a preliminary identification is made, a second unit performs a second set of correlations to confirm the detection of the frequency synchronization burst. The second correlations are preferably also normalized and confirmation of detection is declared when the normalized moving average of the second stage correlation exceeds a threshold value for a number of contiguous samples.

A method and apparatus for reliably detecting MPEG-2 packet sync-byte positions received via a digital transmission system in the event of a packet stream containing a plurality of null packets or a plurality of packets containing a fixed repeating bit pattern and for reliably synchronizing and delivering the MPEG-2 stream broadcast to the receiver transport layer. A Null-Packet Detector compares the content of the current packet with a fixed (or predetermined) bit pattern to detect a null packet to reliably identify the location of the sync-byte of the null packet. A sync-byte position is identified based upon the position of the predetermined fixed bit pattern in the header portion of a plurality of null-packets in the stream.

A digital transmission system is disclosed. The system includes a transmission signal generation unit which generates a transmission signal in which data to be transmitted is carried by a carrier wave, and an additional data process unit which processes so that a low power signal to represent additional data is carried by the carrier wave. The system is embodied as an orthogonal frequency division multiplexing (OFDM) system such as a digital video broadcast-video (DVB-V), and a single carrier system such as a vestigial sideband modulation (VSB). Accordingly, additional data are efficiently transmitted without degrading transmission quality of main data.

In a method for transmitting data in a digital transmission system given packet-switched service, for purposes of channel coding, a turbo-coding is performed in a turbo-coder at the sender side and a turbo-decoding with soft decision output signals is performed in a turbo-decoder at the receiver side. To trigger an ARQ, the channel quality is estimated by a parameter estimation method; the variances of the soft decision output signals at the turbo-decoder are determined; the correctness or respectively, defectiveness of the transmitted packet is inferred from the channel quality and the variances; and a retransmission of at least a part of defective packet is triggered. In the retransmission of the information of a defective packet, at least part of the information suppressed by the dotting in the precious transmission is sent. This additional information is [. . .] inserted into the already existing information at the receiver side, and this complete information is decoded again.

To mitigate the effects of non-linear amplification in a digital transmission system employing a multi-carrier multiplexing communications technique, such as orthogonal frequency division multiplexing or discrete multi-tone, predistortion of an input signal to a power amplifier with a non-linear transfer characteristic is performed in the frequency domain by modifying frequency-domain symbols used to modulate individual sub-carriers. The frequency-domain symbols are modified in a manner that compensates for the amplifier's non-linear transfer characteristic.

A method and circuit for performing channel equalization in a high speed transmission system comprising a transmitter and receiver. An application specific digital signal processor, ASDSP, performs channel equalization and compensation on digital data received from an analogue-to digital converter of the receiver. The ASDSP is operable to execute an application specific set of op-codes needed for performing channel equalization and compensation. An ASDSP register is coupled between the ASDSP and a system CPU in a feedback loop for performing channel equalization at the receiver. The ASDSP stores equalizer parameters and bit error rate measurements used by the ASDSP for performing channel equalization and compensation. An ASDSP program storage memory, coupled to and accessible by the ASDSP, stores an ASDSP micro-sequence program for controlling the processing steps for channel equalization and dataflow through the ASDSP.

The present invention relates to a kind of Mn-Zn ferrite, belonging to the field of oxide magnetic material technology, its main components are: Fe2O3 49-58 mole%, MnO 21-31 mole % and ZnO 15-26 mole%, and the additive component is added, they can be made into ring magnetic core whose mean grain size is 20-80 micrometer, outer diameter is 25 millimeter, inner diameter is 15 millimeter and height is 5 millimeter. In the frequency range of 1K-150 KHz its magnetic conductivity can be up to high level more than 12000, when it is used for making transformer, the number of turns can be reduced, said transformer can be miniaturized, specially, the transformer with high-frequency characteristics can be obtained in the digital transmission system of ISDN and ADSL, etc. and low volume distribution can be implemented, and the signal can be accurately transmitted.

The invention relates to an alarm threshold value adaptive method for a distributed optical fiber temperature sensor, and belongs to the technical field of optical fiber sensing. The method includes: utilizing a DTS (digital transmission system) mainframe to control a light source to send out periodic light pulse to enter a sensing optical fiber, collecting Stokes signals and anti-Stokes signals of backward Raman scattering, calculating temperature distribution of the sensing optical fiber according to temperature of a reference optical fiber ring inside the mainframe, and calculating an alarm threshold value according to ambient temperature curve function. The alarm threshold value is automatically adjusted according to temperature of external environment, so that problems of false alarm and alarm failure of conventional single threshold value are solved, system adaptability is improved, and system reliability is improved.

A digital signal transmission system using a digital modulation system comprising a digital signal transmitter having a first digital signal processing unit and a digital signal receiver receiving a digital signal from the transmitter, wherein the digital signal receiver comprising a second digital signal processing unit for processing the digital signal from the transmitter and outputting a digital demodulated signal and a correlation value signal, a signal converter coupled with the second digital signal processing unit and supplied the correlation value signal therefrom for generating a waveform indicating a transmission condition including a main wave in response to the correlation value signal, and a display coupled with the signal converter for displaying the waveform indicating a transmission condition in the digital transmission system.

A radio communication device comprises a processor configured to generate a transmission signal on the basis of data to be transmitted. The processor generates the transmission signal by a transmission scheme selected from a digital transmission scheme and an analog transmission scheme. The digital transmission scheme is a transmission scheme by which a bit stream obtained through binary encoding of the data to be transmitted is converted into the transmission signal. The analog transmission scheme is a transmission scheme by which the data to be transmitted directly is converted into the transmission signal without performing binary encoding of the data to be transmitted.

Letting fp be the frequency of a pixel clock, fs be the audio sampling frequency, and fa be the frequency of an audio clock to be reproduced, fa=384 fs=(N / M)fp, where N and M are frequency dividing ratios between the pixel clock and the audio clock of a frequency corresponding to the audio sampling frequency. When fs=48 kHz, M=27000 and N=18432, and when fs=44.1 kHz, M=30000 and N=18816. A VCO control unit detects a change in the audio sampling frequency fs from a control voltage Vctl output from a loop filter or from the frequency fo of an output clock of an oscillating unit, and then selects one of at least two VCOs.

A method for measuring the attenuation in digital transmission lines between a switching center and a subscriber station, with a first pulse of a known frequency spectrum being sent from the switching center to the transmission line. From the multitude of the reflections received by the switching center in the time domain that pulse is selected which was caused by the total reflection at the end of the line of a certain subscriber station. The frequency spectrum of the selected pulse is determined and from the frequency spectra of the outgoing pulse and the selected received pulse, the attenuation of the transmission line is determined, depending on its frequency. To achieve the extremely high dynamics necessary for this and to obtain a pulse which is free of any overshoot, reflection measuring is carried out selectively in the frequency range and the pulse is calculated per Fourier transformation. In order to reduce pulse widening by dispersion, the pulse in the frequency range is shifted to higher frequencies. The method makes it possible to qualify subscriber stations for new services by measuring the attenuation from the switching center.

An apparatus and method for restoring digital pulses within a data transmission system which have degraded due to the attenuation and distortion inherent in a data transmission medium. The apparatus comprises an adaptive equalizer which receives signals from the data transmission medium, while the method by which the digital pulses are restored comprises: storing plural equalizer transfer function control values in a memory, passing the signal through an equalizer having a controllable transfer function, comparing a characteristic of the output signal of the equalizer with a reference signal and producing a difference signal, using the difference signal to select a set of stored transfer function control values from the memory, controlling the equalizer from the selected transfer function control values so as to minimize their difference from the reference signal. This apparatus and method are suitable for high-speed applications such as T1 and E1, requiring minimal configuration by the user.

Digital predistortion circuity is disclosed including digital interface circuitry configured to receive a digital input signal having a signal bandwidth (BW) centered about a frequency f0 and provide a digital transmission signal based on the digital input signal. The digital predistortion circuitry includes circuitry configured to generate a digital correction signal based at least in part on the digital input signal, one or more first signal transmission paths configured to transmit the digital transmission signal, and one or more second signal transmission paths separate from the one or more first signal transmission paths and configured to transmit the correction signal

To achieve a wireless communication apparatus capable of lowering power consumption for a digital signal processing of a transmitter in response to a transmission path condition.A wireless communication system performs communication by digital transmission or analog transmission of a signal processed by a digital signal processing unit in a transmitting section on a transmission side toward a reception side through a line, wherein a transmission path condition of the line is measured on the reception side, the transmission path condition is transmitted to the transmission side using a reverse line with respect to the above described line, and a bit width for signal processing of digital signal processing units such as a modulating unit and a digital / analog converting unit is varied by a bit width selecting unit in response to the transmission path condition of the line notified by the reverse line on the transmission side.

A compact electromagnetic coupler for use with digital transmission system is described. In one embodiment, the apparatus includes a first transmission structure, including a portion having a geometry. A second transmission structure having the geometry and positioned proximate the portion of the first transmission line structure having the geometry to form a compact electromagnetic coupler with the first transmission structure a geometry of the electromagnetic coupler to enable placement within a footprint of a standard card connector. The compact electromagnetic coupler so formed enables reconstruction of the logical state and timing of a signal transmitted along the first transmission structure.