Digital signal

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

Linearisation and modulation device

Abstract: The present invention discloses a linearisation and modulation device for a power amplifier The linearisation and modulation device comprises a digital vector modulator (103, 104, 105) for generating a modulated digital signal (IF_MOD) on the basis of digital baseband signals (IIN, QIN) and digital carrier signals (PH_S, PH_C); a correction value generating means (114, 108; 114a, 108a) for generating an amplitude correction value (CV_AMAM) and a phase correction value (CV_AMPM) on the basis of said digital baseband signals (IIN, QIN) and on the basis of a non-linearity distortion generated in said power amplifier (6) arranged in a subsequent stage; an amplitude correction means (106) for generating a corrected digital signal (IF_OUT) on the basis of said modulated digital signal (IF_MOD) and said amplitude correction value (CV_AMAM); a phase correction means (111) for generating a corrected phase control signal on the basis of said phase correction value and an output signal of a phase control signal generation means (110); and a carrier signal generating means (112) for generating said carrier signals (PH_S, PH_C) on the basis of an output of said phase correction means (111) With such a device, a combined modulator and lineariser can be constructed, which leads to a compact system

DC insensitive AGC circuit for optical PRML read channel

Abstract: AGC Circuitry for an optical PRML read channel that is insensitive to low frequency disturbances of an RF input signal. The AGC Circuitry includes a VGA amplifier, a low pass filter, an ADC, a baseline Wander Correction Circuit, a digital gain control circuit, and a DAC. The VGA amplifier amplifies the RF input signal to produce a second RF signal. The low pass filter filters the second RF signal to produce a first analog signal. The ADC converts the first analog signal into a digital AGC output signal suitable for decoding. The baseline Wander Correction Circuit removes from the digital AGC output signal effects of low frequency disturbance of the RF input signal to produce a second digital signal. The digital gain control circuit controls the gain of the VGA amplifier by producing a digital gain control signal in response to the second digital signal. The DAC for converting the digital gain control signal into the analog gain control signal to be applied to the VGA amplifier, the analog gain control signal being substantially free from effects of low frequency disturbance of the RF input signal.

High-precision laser vibrometers based on digital Doppler-signal processing

Abstract: Recent developments in the field of digital signal processing (DSP) hardware and affordable powerful PC platforms enable the realisation of a new generation of laser-Doppler vibrometers, providing outstanding measurement accuracy and resolution. The paper presents both PC based and DSP based solutions for digital Doppler signal processing, utilized within the latest vibrometer models introduced by Polytec GmbH, Waldbroim. It is shown, that heterodyne interferometer technology in combination with high-speed AID conversion and numerical demodulation methods provides superior accuracy and resolution in a wide amplitude and frequency range. Depending on the particular application, either PC based systems or plug-in DSP decoder modules are the preferred solution. Advantages and tradeoffs of both ways are analysed. In addition to digital decoding technology, the presented systems make use of digital signal transmission via a standard S/P-DIF interface, commonly known from digital-audio equipment. This interface allows distortion-free signal recording on digital media and signal acquisition without expensive A/D boards. Based on the described technology, a primary calibration system for accelerometers has been developed in a cooperation project. The aim of this paper is the demonstration of digital signal processing as a powerful alternative to analog technology, that will advance measurement accuracy of future laser-Doppler vibrometers.

Vector electricity meters and associated vector electricity metering methods

Abstract: Line voltage and line current signals are sensed on a power line having at least one conducting path. The sensed line voltages and line currents are converted into a digital signal. A phase-to-neutral voltage signal and phase current signal are computed from the digital signal to thereby define a phase of the power line. An interval of orthogonality is determined from the sensed voltage and current signals, coinciding with passage of an integral number of cycles of a fundamental frequency reference signal which is computed from the computed phase-to-neutral voltage signal. A vector metering quantity is computed for the determined interval of orthogonality from the computed phase-to-neutral voltage signal and the computed phase current signal. The vector metering quantities to be computed may be identified and computed based upon an associated detent. The vector metering quantity is also computed based on an identified circuit topology.

Digital transmitter and method

Abstract: 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.