172 results about "Digital transmitter" patented technology

The invention is an audio-video communication and answering system, where system's properties make it particularly suitable as a Digital Video Messaging System for, amongst other things, answering the door. The elements of the system are a DVMS outside module that is a wireless pocket PC with a proximity sensing, a video camera, a microphone, a speaker, a digital transmitter, a digital receiver, and a keypad; a computerized controller that is a personal computer with components for plaving and recording video and audio media; a DVMS inside module having a screen, a microphone, a speaker, a digital transmitter, a digital receiver, and a keypad; a wireless mode; and a DVMS database application with a graphic user interface. The computerized controller is in communication with a public switching telephone network enabling communication with remote peripheral devices, such as a cell phone, PDA, or computer. The system is based on the Microsoft Windows® Mobile 802.11b to coordinate communication between elements. The database application coordinates responses to prompts and events. The proximity sensor activates the system when the sensor detects the visitor's presence. This then starts a series of prompts and interaction prescribed by the application. The system includes an electrically actuated lock that can be actuated through a code entry or remotely. The system enables a visitor to communicate with an occupant either offsite or onsite, where the visitor never knows the occupant's location, unless the occupant discloses his location.

Digital transmitters having improved characteristics are described. In one design of a digital transmitter, a first circuit block receives inphase and quadrature signals, performs conversion from Cartesian to polar coordinates, and generates magnitude and phase signals. A second circuit block (which may include a delta-sigma modulator or a digital filter) generates an envelope signal based on the magnitude signal. A third circuit block generates a phase modulated signal based on the phase signal. The third circuit block may include a phase modulating phase locked loop (PLL), a voltage controlled oscillator (VCO), a saturating buffer, and so on. A fourth circuit block (which may include one or more exclusive-OR gates or an amplifier with multiple gain states) generates a digitally modulated signal based on the envelope signal and the phase modulated signal. A fifth circuit block (which may include a class D amplifier and/or a power amplifier) amplifies the digitally modulated signal and generates an RF output signal.

The present invention relates to a serial interface transmission system with more than one data line, in which the transmitted data has in-band and out-of-band characters. More particularly, the present invention relates to methods and systems for sending side channel data over a high-speed digital communications link, e.g., a video link. One embodiment of the invention provides a high-speed digital transmitter capable of sending side channel data. The transmitter includes a channel zero encoder, a multiplexer, data enable out (DE_out) control logic, and a channel one encoder. The channel one encoder receives input from the channel one multiplexer and the channel one DE_out control logic. Another embodiment of the invention provides a high-speed digital receiver capable of receiving side channel data. The receiver includes a channel zero decoder, a channel one decoder, DEI signal and FIFO control signal recovery logic, and a channel one de-multiplexer. The DEI signal and FIFO control signal recovery logic receives input from the channel one decoder. Similarly, the channel one demultiplexer receives input from the channel one decoder.

An equalizer provided in a digital transmitter compensates for attenuation in a signal channel to a digital receiver. The equalizer generates signal levels as a logical function of bit history to emphasize transition signal levels relative to repeated signal levels. The preferred equalizer includes an FIR transition filter using a look-up table. Parallel circuits including FIR filters and digital-to-analog converters provide a high speed equalizer with lower speed circuitry. The equalizer is particularly suited to in-cabinet and local area network transmissions where feedback circuitry facilitates adaptive training of the equalizer.

A method and apparatus for digital predistortion of power amplifiers are disclosed. Successful digital predistortion parameter settings are correlated with the operating conditions that affect the distortion of an amplifier. These operating conditions may include input power level, carrier frequency, temperature, DC supply voltage, or others. The successful predistortion parameter settings along with the corresponding operating conditions are stored in a list that is indexed using multi-dimensional attribute vectors. The elements of the list are generated automatically.

A wireless digital audio system includes a portable audio source with a digital audio transmitter operatively coupled thereto and an audio receiver operatively coupled to a headphone set. The audio receiver is configured for digital wireless communication with the audio transmitter. The digital audio receiver utilizes fuzzy logic to optimize digital signal processing. Each of the digital audio transmitter and receiver is configured for code division multiple access (CDMA) communication. The wireless digital audio system allows private audio enjoyment without interference from other users of independent wireless digital transmitters and receivers sharing the same space.

A transmitter and method is provided for digitally upconverting a baseband digital signal to a modulated intermediate frequency (IF) digital signal and sigma-delta modulating the IF digital signal. The baseband digital signal is split into N phases, as can be accomplished using a polyphase interpolation technique (polyphase filter), and modulated. The modulated N phases are not recombined and each phase is further modulated, as can be accomplished using a digital-to-digital sigma-delta modulator that generates digital output signals at the same rate. A high speed digital multiplexer multiplexes the digital output signals into a single bit stream at a higher rate for subsequent power amplification and RF transmission.

The invention relates to a self-balancing spray boom spraying machine belonging to the field of plant protection spraying machinery. The self-balancing spray boom spraying machine provided by the invention comprises a mechanism part and a control part, wherein the mechanism part is composed of a walking chassis, a spraying machine main body, a moving rack, a spray boom, a static hydraulic cylinder, a movable hydraulic cylinder and the like; the position and orientation adjustment on a spray boom is realized by the moving rack, the static hydraulic cylinder and the movable hydraulic cylinder together; the spray boom is L-shaped in the length direction, the horizontal rigidity of the spray boom is improved greatly while the vertical rigidity of the spray boom is ensured, and simultaneously the L-shaped structure is good for realizing air-curtain type spraying and targeting type spraying; and the control part is composed of a level sensor, a digital transmitter/ an analog transducer, a processor, a proportional controller and a proportional reversing valve. According to the invention, the position and orientation of the spray boom can be detected in real time when the constructed self-balancing spray boom spraying machine operates, the real-time compensation can be carried out, and the elastic deformation and rigid motion of the spray boom can be reduced greatly, thus the spray uniformity can be improved.

An optical access network with centralized digital optical line termination OLT including an optical line termination unit having a digital transmitter and a coherent receiver for downstream signal transmitting and upstream signal receiving, and at least one optical network unit ONU with transceiver functions for communicating with the OLT over an optical path, the ONU including intensity modulation and single photodiode detection, wherein the digital transmitter includes digital signal processing DSP, digital-to-analog conversion DAC and analog-to-digital conversion ADC functions that can be shared by all multiple ones of the ONU in the network, the DSP reducing or removing dispersion and non-linearity effects in the network and the coherent receiver enabling performance of the downstream stream signal transmitting to match that of the upstream signal receiving in the OLT.

A hearing assistance system having a plurality of transmission units, a microphone arrangement and a digital transmitter for transmitting audio signals as audio data packets via a wireless digital audio link; at least one user worn receiver unit; a relay unit with a mixing unit for producing a mixed audio signal from audio signals received and at least one digital transceiver for receiving audio signals from the transmission units via the digital audio link and for transmitting the mixed audio signal via the wireless digital audio link as audio data packets to a digital receiver of the receiver unit(s) for stimulating the hearing of the user(s) according to audio signals supplied from the receiver unit, the relay unit and each transmission unit transmitting each audio data packet in at least one allocated separate slot of a TDMA frame at a different frequency according to a frequency hopping sequence.

A digital transmitter (20) that may be advantageously used in a high-frequency transceiver, such as a wireless telephone handset, is disclosed. The transmitter (20) includes digital upconverter functions (36L, 36Q) that operate in combination with a digital band-pass sigma-delta modulator (40) to generate modulated digital signals at a sample frequency that is a multiple of the transmit frequency. The digital band-pass sigma-delta modulator (40) applies a noise transfer function in a feedback filter (72) in which the center of the pass band corresponds to the transmit frequency, and in which notches in the characteristic can be symmetrically or asymmetrically selected to correspond to specific frequencies, such as the receive band frequency, in which transmit noise is to be minimized. A combined FIR digital filter (42) and MOS power switch array (44) is also disclosed, in which a cascode arrangement of drain-extended MOS power transistors (78) and switching transistors (82) provide the output RF signal, with a coarse gain control (80) applied.

A filter device is for use in a digital communications receiver. The filter device processes an incoming signal from a digital transmitter having a first filter response providing a first spectral pulse shape in frequency space. The filter device has a second filter response having a more rapid cut-off than the first filter response and provides when applied to the first spectral pulse shape an output signal comprising a second spectral pulse shape in frequency space selected to substantially minimize inter-symbol interference. The second spectral shape may also be selected to substantially minimize adjacent-channel noise. A receiver and a communications system incorporating the filter device and a method of filtering in a receiver are also described.

Systems and methods for suppressing transmitter noise in a receive band of a co-located receiver that are suitable for wideband applications are disclosed. In one embodiment, an analog radio frequency transmit signal output by a transmitter includes a desired signal in a transmit band of the transmitter and transmitter noise in a receive band of a main receiver. A secondary receiver obtains a secondary receiver input signal that is representative of at least the transmitter noise in the receive band of the main receiver and outputs a digital feedforward signal. A digital feedforward transmit noise cancellation subsystem generates a digital transmitter noise cancellation signal that is representative of the transmitter noise in the receive band based on the digital feedforward signal and subtracts the digital transmitter noise cancellation signal from a digital receive signal output by the main receiver to thereby provide a compensated digital receive signal.

A system for providing hearing assistance to at least one user, having at least one audio signal source; a transmission unit with a digital transmitter for wirelessly transmitting audio signals as data packets to a frame structure from the audio signal source; at least one ear-worn receiver unit for receiving the transmitted audio signals and a hearing stimulating mechanism, the receiver unit having a digital transceiver adapted to listen, and optionally transmit, during part of each frame and to sleep during the remainder of the frame; wherein the receiver unit has a capacitor for supplying current to the transceiver during listening or transmission operation, and a controlled current source including a control unit for controlling current flowing to the transceiver and the capacitor a manner preventing changes in the current flowing to the transceiver and the capacitor caused by the transceiver switching between sleeping and listening/transmission operation and vice versa.

A method and apparatus for direct conversion of digital data to high power RF signals, known as DDRF. The method and apparatus receive a digital signal, create a digital modulated signal therefrom, and amplify the modulated signal with an H-bridge Power Amplifier for transmission. DDRF uses a multi-level H-bridge amplification circuit to establish a more power efficient digital transmitter.

Systems and methods are provided for calibrating a digital predistorter in an integrated transceiver circuit. A digital transmitter path provides a signal from a digital input. The transmitter path includes a digital predistorter that predistorts the digital input to mitigate nonlinearities associated with a power amplifier. The integrated transceiver circuit further includes a receiver path associated with the digital transmitter path. A coupling element provides the signal from the transmitter path to the receiver path. A signal evaluator determines values for at least one parameter associated with the digital predistorter based on the signal.

A communication system includes digital transmitter circuitry (26) including a CRC (cyclic redundancy check) generator circuit (28) generating a first CRC code based on a message and appending the CRC code to the message a first data packet, and circuitry (26-1,2,3) transforming the first data packet to provide a second data packet and transmitting it. Digital receiver circuitry (120) includes circuitry (12-1,2,3) receiving the second data packet, a CRC verification circuit (14-1) comparing a received digital CRC code portion of the second data packet to a calculated digital CRC code portion including any introduced error to detect the existence of any error in the second data packet. The message is presented for further processing if no error is detected, and a CRC-based FEC (forward error correction) circuit (14-2) receives the message and calculated digital CRC code from the verification circuit if an error is detected, corrects the detected error, and indicates the error is uncorrectable if the correction is unsuccessful.