Digital signal

About: Digital signal is a research topic. Over the lifetime, 44213 publications have been published within this topic receiving 345279 citations.

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.

High-efficiency linear power amplifier

Abstract: A transmission signal and a pilot signal are predistorted by a digital predistorter 13 by use of a power-series model, and the predistorted output is converted by a digital-analog converter 14 to an analog signal. The analog signal is up converted by a frequency converter 15 to an RF-band signal, which is transmitted after being power-amplified by a Doherty amplifier 16. The pilot signal is extracted by a pilot signal extractor 17 from the output from the Doherty amplifier, and the extracted pilot signal is down converted by a frequency converter 18 to a baseband signal. The baseband pilot signal is converted by an analog-digital converter 19 to a digital pilot signal. A control part 21 detects an odd-order distortion component from the digital pilot signal, and based on the detected result, controls parameters of the digital predistorter.

Device for the coherent demodulation of time-frequency interlaced digital data, with estimation of the frequency response of the transmission channel and threshold, and corresponding transmitter

Abstract: A coherent demodulation device, for the demodulation of a digital signal of the type constituted by digital elements distributed in the time-frequency space and transmitted in the form of symbols constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of the digital elements and broadcast simultaneously, the digital signal comprising reference elements, having a value and a position, in the time-frequency space, that are known to the demodulation device, comprising means for the estimation, by Fourier transform, of the frequency response of the transmission channel at any instant, carrying out the transformation of the received samples, corresponding to reference elements, from the frequency domain to the temporal domain, the multiplication in the temporal domain of the transformed samples by a rectangular temporal window (f n) and the reverse transformation, after the multiplication, of the obtained samples from the temporal domain into the frequency domain, the estimation means comprising means for the thresholding of the samples in the temporal domain, providing for the systematic elimination of the samples below a certain threshold.

Multi-protocol radio frequency identification transponder tranceiver

Abstract: A transceiver for a RFID reader and a transceiver for a RFID transponder (tag) allow communication between the two devices. The RFID reader utilizes an analog front end and a digital backend. In the receiver portion of the transceiver, the front end of the RFID reader uses a pair of down-conversion mixers to demodulate a received signal into in-phase (I) and quadrature (Q) components and analog-to-digital converters (ADC) digitize the signal. A digital signal processor (DSP) in the back end processes the digital signal and uses a matched filter for data detection. The RFID tag receives an inductively coupled signal from the reader and the receiver portion of the tag uses a pulse/level detector that employs an analog comparator and a sample and hold circuit to detect the received signal. A digital decoder/controller is used to decode the incoming data and to establish a sampling clock for the pulse/level detector. An automatic gain control (AGC) circuit adjusts a receiver gain according to the received signal strength and controls tuning of magnetic coupling circuitry.

Microprocessor-based battery tester system

Abstract: A system for determining the operating characteristics of an energy source. The system comprises controller means for generating and shaping a time-varying voltage signal for application to the energy source; conversion means for receiving from the energy source a time-varying return voltage signal and for converting the time-varying return voltage signal into a digital signal. The amplitude of the time-varying return signal contains information representative of the operating characteristics of the energy source. The time-varying return voltage signal is produced in response to the time-varying voltage signal. The controller means is responsive to the digital signal and determines the operating characteristics of the energy source. The controller means generates display signals, and the display signals are representative of the operating characteristics of the energy source. The system also comprises display means for displaying the display signals.