Digital signal

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

A high-performance digital system for electrical capacitance tomography

Abstract: This paper describes a recently developed digital-based data acquisition system for electrical capacitance tomography (ECT). The system consists of high-capacity field-programmable gate arrays (FPGA) and fast data conversion circuits together with a specific signal processing method. In this system, digital phase-sensitive demodulation is implemented. A specific data acquisition scheme is employed to deal with residual charges in each measurement, resulting in a high signal-to-noise ratio (SNR) at high excitation frequency. A high-speed USB interface is employed between the FPGA and a host PC. Software in Visual C++ has been developed to accomplish operational functions. Various tests were performed to evaluate the system, e.g. frame rate, SNR, noise level, linearity, and static and dynamic imaging. The SNR is 60.3 dB at 1542 frames s−1 for a 12-electrode sensor. The mean absolute error between the measured capacitance and the linear fit value is 1.6 fF. The standard deviation of the measurements is in the order of 0.1 fF. The dynamic imaging test demonstrates the advantages of high temporal resolution of the system. The experimental results indicate that the digital signal processing devices can be used to construct a high-performance ECT system.

Blind signal estimation in conjugate signal models with application to I/Q imbalance compensation

Abstract: This letter addresses the blind signal estimation problem in the so-called conjugate signal model, where the observed signal is a linear combination of the desired signal and its complex conjugate. It will be shown that blind signal recovery in this kind of signal model is feasible using only the second-order statistics of the observed signal, under the assumption of circular or proper complex signals. Furthermore, one practical example application in the field of communications receiver signal processing will be given, where the image signal interference caused by amplitude and phase mismatches of the receiver analog branches is digitally attenuated. In addition to the analytical results and practical implementation algorithms, the efficiency of the proposed estimation concepts in the digital image rejection application is evaluated using computer simulations, showing impressive performance results.

Low bit rate speech coding system and compression

Abstract: A speech coder apparatus operates to compress speech signals to a low bit rate. The apparatus includes a continuous speech recognizer (CSR) which has a memory for storing templates. Input speech is processed by the CSR where information in the speech is compared against the templates to provide an output digital signal indicative of recognized words, which signal is transmitted along a first path. There is further included a front end processor which is also responsive to the input speech signal for providing output digitized speech samples during a given frame interval. A side information encoder circuit responds to the output from the front end processor to provide at the output of the encoder a parameter signal indicative of the value of the pitch and word duration for each word as recognized by the CSR unit. The output of the encoder is transmitted as a second signal. There is a receiver which includes a synthesizer responsive to the first and second transmitted signals for providing an output synthesized signal for each recognized word where the pitch, duration and amplitude of the synthesized signal is changed according to the parameter signal to preserve the quality of the synthesized speech.

High level software synthesis for signal processing systems

Abstract: For the design of complex digital signal processing systems, block diagram oriented simulation has become a widely accepted standard Current research is concerned with the coupling of heterogenous simulation engines and the transition from simulation to the implementation of digital signal processing systems Due to the difficulty in mastering complex design spaces high level hardware and software synthesis is becoming increasingly important The authors concentrate on the block diagram oriented software synthesis of digital signal processing systems for programmable processors, such as digital signal processors (DSP) They present the synthesis environment DESCARTES illustrating novel optimization strategies Furthermore they discuss goal directed software synthesis, by which code is interactively or automatically generated, which can be adapted to the application specific needs imposed by constraints on memory space, sampling rate or latency >