Use Of Digital Signal Processors Research Articles

Matched Filtering for MIMO Coherent Optical Communications with Mode-Dependent Loss Channels.

The use of digital signal processors (DSP) to equalize coherent optical communication systems based on spatial division multiplexing (SDM) techniques is widespread in current optical receivers. However, most of DSP implementation approaches found in the literature assume a negligible mode-dependent loss (MDL). This paper is focused on the linear multiple-input multiple-output (MIMO) receiver designed to optimize the minimum mean square error (MMSE) for a coherent SDM optical communication system, without previous assumptions on receiver oversampling or analog front-end realizations. The influence of the roll-off factor of a generic pulse-amplitude modulation (PAM) transmitter on system performance is studied as well. As a main result of the proposed approach, the ability of a simple match filter (MF) based MIMO receiver to completely eliminate inter-symbol interference (ISI) and crosstalk for SDM systems under the assumption of negligible MDL is demonstrated. The performance of the linear MIMO fractionally-spaced equalizer (FSE) receiver for an SDM system with a MDL-impaired channel is then evaluated by numerical simulations using novel system performance indicators, in the form of signal to noise and distortion ratio (SNDR) loss, with respect to the case without MDL. System performance improvements by increasing the transmitter roll-off factor are also quantified.

Efficient Computing in Image Processing and DSPs with ASIP Based Multiplier

Background: With the growing demand of image processing and the use of Digital Signal Processors (DSP), the efficiency of the Multipliers and Accumulators has become a bottleneck to get through. We revised a few patents on an Application Specific Instruction Set Processor (ASIP), where the design considerations are proposed for application-specific computing in an efficient way to enhance the throughput. Objective: The study aims to develop and analyze a computationally efficient method to optimize the speed performance of MAC. Methods: The work presented here proposes the design of an Application Specific Instruction Set Processor, exploiting a Multiplier Accumulator integrated as the dedicated hardware. This MAC is optimized for high-speed performance and is the application-specific part of the processor; here it can be the DSP block of an image processor while a 16-bit Reduced Instruction Set Computer (RISC) processor core gives the flexibility to the design for any computing. The design was emulated on a Xilinx Field Programmable Gate Array (FPGA) and tested for various real-time computing. Results: The synthesis of the hardware logic on FPGA tools gave the operating frequencies of the legacy methods and the proposed method, the simulation of the logic verified the functionality. Conclusion: With the proposed method, a significant improvement of 16% increase in throughput has been observed for 256 steps iterations of multiplier and accumulators on an 8-bit sample data. Such an improvement can help in reducing the computation time in many digital signal processing applications where multiplication and addition are done iteratively.

Nuevo algoritmo de compensación térmica para sensores de presión piezorresistivos basado en la aproximación lineal por segmentos

The piezoresistive pressure sensors are widely used in monitoring and control applications within the industrial sector. These sensors have problems of temperature dependence, and non-linearities that affect the measurement accuracy. For this reason, it is necessary to use signal conditioning circuits for to obtain high accuracy outputs. One of the most common techniques currently used to conditioning the signals from the sensors is based on the use of digital signal processors and compensation algorithms.This paper proposes a new calibration and compensation algorithm for piezoresistive pressure sensors based on the linear segment approximation with thermal compensation. The algorithm was simulated using the mathematical software MathCAD and using data from a piezoresistive pressure dummy sensor. The algorithm has been validated experimentally implementing it into two digital signal processors using vented piezoresistives pressure sensors of 10bar in the range of temperatures from 0°C to 80°C. The result was that the maximum error in the sensor output due to the temperature dependence of the offset was 0,081% of full scale output. The maximum error obtained at the output caused by the temperature dependence of the sensitivity was 0,106% of full scale output. The effectiveness of the algorithm is demonstrated in the thermal compensation of piezoresistive pressure sensors. This algorithm can be applied to other types of sensors having thermal dependencies and incorporating a microprocessor or digital signal processor.

The use of digital signal processors (DSPs) in real-time processing of multi-parametric bioelectronic signals

In many cases of bioanalytical measurement, calculation of large amounts of data, analysis of complex signal waveforms or signal speed can overwhelm the performance of microcontrollers, analog electronic circuits or even PCs. One method to obtain results in real time is to apply a digital signal processor (DSP) for the analysis or processing of measurement data. In this paper we show how DSP-supported multiplying and accumulating (MAC) operations, such as time/frequency transformation, pattern recognition by correlation, convolution or filter algorithms, can optimize the processing of bioanalytical data. Discrete integral calculations are applied to the acquisition of impedance values as part of multi-parametric sensor chips, to pH monitoring using light-addressable potentiometric sensors (LAPS) and to the analysis of rapidly changing signal shapes, such as action potentials of cultured neuronal networks, as examples of DSP capability.

A Fast Continuous Magnetic Field Measurement System Based on Digital Signal Processors

In order to study dynamic effects in accelerator magnets, such as the decay of the magnetic field during the dwell at injection and the rapid so-called "snapback" during the first few seconds of the resumption of the energy ramp, a fast continuous harmonics measurement system was required. A new magnetic field measurement system, based on the use of digital signal processors (DSP) and Analog to Digital (A/D) converters, was developed and prototyped at Fermilab. This system uses Pentek 6102 16 bit A/D converters and the Pentek 4288 DSP board with the SHARC ADSP-2106 family digital signal processor. It was designed to acquire multiple channels of data with a wide dynamic range of input signals, which are typically generated by a rotating coil probe. Data acquisition is performed under a RTOS, whereas processing and visualization are performed under a host computer. Firmware code was developed for the DSP to perform fast continuous readout of the A/D FIFO memory and integration over specified intervals, synchronized to the probe's rotation in the magnetic field. C, C++ and Java code was written to control the data acquisition devices and to process a continuous stream of data. The paper summarizes the characteristics of the system and presents the results of initial tests and measurements

A DSP-Based Reconfigurable SDR Platform for 3G Systems

As the code division multiple access (CDMA) based third generation cellular infrastructure requires high performance signal processing in a baseband modem, an application-specific integrated circuit or a field-programmable gate array has commonly been used for chip rate processing. In this paper, the use of digital signal processors (DSP) is explored for a cdma2000 and a wideband CDMA channel modem with the goal of increasing flexibility. The design concepts of the prototype software-defined radio platform we implemented to estimate the potential and feasibility of commercial SDR platforms are presented. We discuss the hardware and software architecture of the platform, considerations for reconfigurability, and the test results. We also address practical issues for real-time chip rate processing and optimization schemes of DSP software, and provide detailed measurement results of DSP performance.

Energy aware compilation for DSPs with SIMD instructions

The growing use of digital signal processors (DSPs) in embedded systems necessitates the use of optimizing compilers supporting special hardware features. In this paper we present compiler optimizations with the aim of minimizing energy consumption of embedded applications: This comprises loop optimizations for exploitation of SIMD instructions and zero overhead hardware loops in order to increase performance and decrease the energy consumption. In addition, we use a phase coupled code generator based on a genetic algorithm (GCG) which is capable of performing energy aware instruction selection and scheduling. Energy aware compilation is done with respect to an instruction level energy cost model which is integrated into our code generator and simulator. Experimental results for several benchmarks show the effectiveness of our approach.

PuMa, a digital Pulsar Machine

We have designed and constructed PuMa, a pulsar machine that has both a baseband recording and a digital lterbank mode. Its design is based on the use of digital signal processors (DSPs). Their operation is controlled by software, which makes PuMa recongurable, flexible and easy to operate. The maximum number of channels in the digital lterbank mode is 32 768 over a bandwidth of 80 MHz. This makes PuMa suitable for pulsar observations at low sky frequencies. The maximum bandwidth in baseband recording mode is two times 10 MHz. The machine was installed at the Westerbork Synthesis Radio Telescope in The Netherlands in 1998. We discuss in some detail PuMa's technical properties and capabilities. Recent observations, a sample of which are presented here, demonstrate its capabilities and that it is performing up to its specications.

PuMa, the new Dutch PulsarMachine

AbstractPuMa is a fully digital PulsarMachine the operation at the Westerbork Synthesis Radio Telescope (WSRT). Its design is based on the use of Digital Signal Processors. It has two modes of operation: a baseband recording mode and a digital filterbank mode.

Design and implementation of novel quasi-linear DSP-based control for power converters

A quasi-linear control strategy for regulating DC/DC converters under wide parameter variation is implemented using a digital signal processor. The design of this DSP-based controller is presented. Since the control method allows realtime modification of control parameters according to the changing environment, the resulting control shows significant improvement in performance over conventional methods. The proposed controller, being a programmable digital circuit, is highly reliable and flexible. The paper demonstrates the use of digital signal processors in controlling power converters.

Low stress switching for efficiency

Power modules that turn on or off "softly," at near zero voltage or current, promise marked gains in performance by cutting switching losses and allowing faster controls-to the likely benefit of power converters. Medium power inverters have undergone significant changes. One improvement stems from new power transistors such as insulated-gate bipolar transistors (IGBTs) with their increasing voltage- and current-carrying capabilities and increasing switching frequencies. Others derive from the use of digital signal processors and such modern control techniques as fuzzy logic and neural networks, as well as from advances in the applications of power converters that employ soft switching of the power devices. Soft-switching technologies promise marked gains in performance-lower losses and higher switching frequencies than those in the prevailing hard-switching technology. The idea is to switch a device only when the voltage across it, or the current through it, is zero. Representative soft switching converters include DC-to-DC converters rated at up to several hundred watts, as well as inductive chargers for electric vehicle batteries rated at up to 120 kW. Technologically speaking, advances in soft-switching inverters have arisen chiefly from enhancements to semiconductor power devices. Today, IGBTs lead the market for medium-power applications.

Analysis and Simulation of Road Profiles

The power spectral density (PSD) estimate is a parameter commonly used to characterize the acceleration of vehicles and, in conjunction with closed-loop random vibration controllers, to simulate the transport environment. The vertical acceleration experienced by the loading tray of road transport vehicles is mainly a function of the type of suspension, load, vehicle speed, and road surface characteristics. While the first three parameters may vary considerably between and during journeys, the statistical parameters used to describe road surface profiles are much less susceptible to change with respect to time. This paper presents a brief analysis and discussion of the spectral and statistical characteristics of actual road surface elevation records. The deviation of the road profile distribution from the Gaussian distribution is revealed, and it is shown that roads of different roughness seem to retain their spectral shape. In addition, a range of statistical parameters are introduced and recommended for use in the classification of road profiles. A technique in which a random vibration controller is used to simulate road profile spectra by controlling the displacement instead of the acceleration of a shaker table is demonstrated. The technique uses a physical model of a vehicle suspension to account for the dynamic characteristics of the vehicle. Finally, the use of digital signal processors (DSP) together with a time domain adaptive filter control technique for the accurate reproduction of synthesized demand signals is presented.

A digital coherent receiver suitable for land-mobile satellite communications

Describes an advanced coherent demodulation technique suitable for land-mobile satellite communications. The proposed technique features a combined narrow/wide band dual open loop (DOL) carrier phase estimator, which effectively enables the coherent receiver to track fast phase fluctuations caused by fading, without degradation in phase slip characteristics. Additionally, an open loop phase estimator has inherent quick recovery performance. Its bit error rate (BER) performance is shown to be superior to that for existing detection schemes, achieving a 10/sup -2/ BER at 6.3 dB E/sub b//N/sub 0/ (0.9 dB greater than the theoretical E/sub b//N/sub 0/ condition for perfect carrier phase tracking) for QPSK over a Rician fading channel with the 10 dB Rician factor and the 1/16 baud rate fading pitch. The paper also describes a quick bit timing recovery scheme, with interpolation, featuring an open loop structure. Further, it presents an experimental digital modem developed through the use of digital signal processors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Introducing Undergraduate Students to The Use of Digital Signal Processors

Introducing undergraduate students to the use of digital signal processors This article describes a procedure for teaching undergraduate students the implementation of digital signal processing algorithms (using the TMS320C25). Material used, description of the processor, examples and working assembly codes are presented.

Embedding spectral analysis in equipment

The use of digital signal processors (DSPs) that enable continuous estimates of signal frequency components to be incorporated into a broad range of real-time systems is considered. Classical spectral estimation methods are reviewed. Real-time implementation of the methods, all of which use some form of fast Fourier transform method, on DSP chips is discussed. Some applications of these chips are examined. >

Convolutional encoding and Viterbi decoding using the DSP56001

Digital signal processors began their life like the laser — an invention in search of applications. Of course, digital signal processors were originally designed for applications such as low-pass filtering which could not be accomplished by conventional microprocessors. As DSP has become more widespread, the range of applications has increased. This application note describes the use of digital signal processors in convolutional encoding and decoding. Convolutional encoding provides an improved way of transmitting data at high speeds over noisy channels. Its use has been limited by the need to carry out the high-speed realtime operations required by convolutional encoders/decoders. The new digital signal processors now make it possible to implement systems that require very large numbers of simple (e.g. shifting and adding, exclusive or, etc.) high-speed computations. This application note looks at both the theory of the Viterbi (or trellis) convolutional encoder/decoder and its implementation.

Real-time digital filtering, event triggering, and tomographic reconstruction of JET soft x-ray data (abstract)

Based upon the experience gained with the present soft x-ray data acquisition system, new techniques are being developed which make extensive use of digital signal processors (DSPs). Digital filters make 13 further frequencies available in real time from the input sampling frequency of 200 kHz. In parallel, various algorithms running on further DSPs generate triggers in response to a range of events in the plasma. The sawtooth crash can be detected, for example, with a delay of only 50 μs from the onset of the collapse. The trigger processor interacts with the digital filter boards to ensure data of the appropriate frequency is recorded throughout a plasma discharge. An independent link is used to pass 780 and 24 Hz filtered data to a network of transputers. A full tomographic inversion and display of the 24 Hz data is carried out in real time using this 15 transputer array. The 780 Hz data are stored for immediate detailed playback following the pulse. Such a system could considerably improve the quality of present plasma diagnostic data which is, in general, sampled at one fixed frequency throughout a discharge. Further, it should provide valuable information towards designing diagnostic data acquisition systems for future long pulse operation machines when a high degree of real-time processing will be required, while retaining the ability to detect, record, and analyze events of interest within such long plasma discharges.

The Use of Digital Signal Processors in Computer Graphics

AbstractThe geometric processing stage in a computer graphic system is generally realised in VLSI or dedicated hardware, this paper describes the use of a Digital Signal Processor (DSP). By using a programmable DSP the hardware design effort is displaced into software. Using a single DSP in a co‐processor configuration the speed of the vertex processing stage within the geometric processor is increased by a factor of five compared to a high performance microprocessor. The use of DSPs in a multi‐processor system is also discussed.