Signal Processing Chip Research Articles

Extraction of the spectral information of terahertz signals using superconducting Josephson junction

Using YBa2Cu3O7−δ/MgO bicrystal Josephson junction, we have developed a setup for spectrum analyses of terahertz signals, up to 2.5 THz, with a frequency resolution of 3 GHz. The junction works at liquid nitrogen temperature when the signal frequencies are low while for signals at 1.6 THz and 2.5 THz the junction is cooled to 6 K. Digital signal processing (DSP) chips are made use of to build a data acquisition and processing system so that it can be compact, fast, and intelligent. With the completion of the relevant hardwares and softwares, the measurements are now automated.

Integrated GMR angle sensor for electrical commutated motors including features for safety critical applications

An integrated GMR (Giant Magneto Resistance) angle sensor will be presented which is designed to fulfill requirements for electrical commutated motor-drives. These motors use sine-commutation for the coils and need the angle of the motor-shaft in accuracy ranges below 1∘ with update-rates of 50- 100 μs. This integrated GMR Angle sensor solves this problem using integrated GMR Angle-Sensors on top of the silicon signal processing chip. The differential GMR-bridge signals are converted to the digital domain by sigma-delta ADCs and these raw-signals are error-compensated. An additional autocalibration feature is implemented to improve the accuracy during operation. The very fast angle-measurement is performed using parallel analog signal processing, 24 MHz finite state machine with dedicated peripherals and an 8 Mbit/s SPI interface. An additional feature to reduce the time delay is the implemented angle-value prediction. Built-in selftests, switchable voltages for signal-path tests and multiple safety voltage comparators are implemented for safety-critical applications.

A new method for real-time and accurate determi-nation of satellite orbits without transfer

Based on the GPS theory, a new method of real-time and accurate determination is proposed. This method makes use of the advantage of optical fiber transmission system, which has high-precision time and frequency synchronization. Several ground stations which are accurately time compared, transmit signals to the satellite continuously. The satellite could obtain the real-time and precise orbits of its own by the signal receiver and signal processing chip on the satellite. This method can attain the orbit position with less time, without the time for transferring signal back to the ground. Based on the realization of 100 ps-level time synchronization between stations, achieving higher measurement accuracy of satellite orbit is entirely feasible. This new method can also be used in high-precision satellite attitude measurement.

Real Time Implementation of Frost Beamformer for Underwater Communications

In this paper, we investigate the performance of Frost's linearly constrained minimum variance (LCMV) adaptive beamformer via computer simulations for QPSK signals transmitted over Rayleigh and Rician fading channels. Simulation results show that the Frost beamformer can still improve the signal-to-interference-plus-noise ratio, even over fading channels. For real-time underwater communications, a prototype system is implemented, which uses TMS320C40 digital signal processor chip for realization of the Frost beamformer. Through experiments in an acoustic trough the validity of the real-time Frost beamformer prototype system is verified, and the feasibility of its use in underwater communications is assessed.

Voice Processors Based on the Human Hearing System

A voice processor is a dedicated audio signal-processing chip for mobile phones and personal computers that enables high-performance noise reduction and acoustic echo cancellation for highly noisy environments. The algorithms and hardware underlying these chips' performance are based on the sophisticated operation of the human hearing system.

Applied digital signal processing systems for vortex flowmeter with digital signal processing

The spectral analysis is combined with digital filter to process the vortex sensor signal for reducing the effect of disturbance at low frequency from pipe vibrations and increasing the turndown ratio. Using digital signal processing chip, two kinds of digital signal processing systems are developed to implement these algorithms. One is an integrative system, and the other is a separated system. A limiting amplifier is designed in the input analog condition circuit to adapt large amplitude variation of sensor signal. Some technique measures are taken to improve the accuracy of the output pulse, speed up the response time of the meter, and reduce the fluctuation of the output signal. The experimental results demonstrate the validity of the digital signal processing systems.

Design for a Simplified Cochlear Implant System

A simplified cochlear implant (CI) system would be appropriate for widespread use in developing countries. Here, we describe a CI that we have designed to realize such a concept. The system implements 8 channels of processing and stimulation using the continuous interleaved sampling (CIS) strategy. A generic digital signal processing (DSP) chip is used for the processing, and the filtering functions are performed with a fast Fourier transform (FFT) of a microphone or other input. Data derived from the processing are transmitted through an inductive link using pulse width modulation (PWM) encoding and amplitude shift keying (ASK) modulation. The same link is used in the reverse direction for backward telemetry of electrode and system information. A custom receiver-stimulator chip has been developed that demodulates incoming data using pulse counting and produces charge balanced biphasic pulses at 1000 pulses/s/electrode. This chip is encased in a titanium package that is hermetically sealed using a simple but effective method. A low cost metal-silicon hybrid mold has been developed for fabricating an intracochlear electrode array with 16 ball-shaped stimulating contacts

Precise digital control system of a moving mirror’s reciprocating move at even speed

The moving mirror’s speed evenness and distance at even speed determine the spectrogram quality and resolution of the Fourier transform spectrometer (FTS). To improve the performance of FTS, a precise control system is designed to realize the moving mirror (MM)’s reciprocating move at even speed. A laser reference measurement interferometer with phase-shifting through polarization is introduced, which makes the position measurement resolution reach the half wavelength of the laser. At the moment MM changes direction, the configuration of the interference signal is complicated, which induces the measurement count error using a common direction judgment method. In this paper, an improved direction judgment method is proposed based on the analysis of the interfering signal while MM changes direction, and the corresponding logical circuits are designed in Field Programmable Gate Array(FPGA). The MM is driven by a moving coil direct current (DC) linear motor, and the mathematical model is described. According to the analysis of the system characteristics and requirement, a fuzzy-PID control strategy is proposed. The fuzzy-PID control algorithm and its digital realization are studied. In order to reduce the computing quantity, the PID parameters for different inputs are calculated in advance by computer and stored in memory as tables, so the main work of the fuzzy-PID digital control algorithm is the simple look-up of the table, which makes the computing quantity very small and easy to realize in a Digital Signal Processing (DSP) chip. The control system is realized, and the experiment results show that the moving mirror’s speed reaches evenness within 0.1s almost without overshoot after changing direction.

A Hybrid Electrode Array With Built-In Position Sensors for an Implantable MEMS-Based Cochlear Prosthesis

A hybrid electrode array has been developed for use in an implantable MEMS-based cochlear prosthesis intended to restore hearing to the profoundly deaf. The array provides high-density stimulation and embedded position sensing to improve sound perception, minimize insertion damage, and optimize implant placement. Interfacing with a hermetically-packaged microcontroller and a bidirectional wireless interface over an eight-lead polymeric cable, the array integrates custom signal-processing electronics with thin-film lithographically defined IrO electrodes and polysilicon position sensors. The signal-processing chip (2.4 mm times 2.4 mm) operates from plusmn2.5 V, accepts 16-b commands, and performs command validation, stimulus current generation, site/sensor selection, offset compensation, and output-signal conditioning. The array contains nine polysilicon strain gauges to detect array position and tip contact. These strain sensors have gauge factors of 15-20, allowing the array tip position to be determined within 50 mum while providing tip-contact signals of more than 100 mV. The on-chip signal processing allows the use of a standard bus interface, reduces the parasitic capacitance and noise coupling on the connecting cables, allows the array shape to be imaged at a rate up to 10 times per second, and suppresses the output noise down to 3 mV.

Design and fabrication steps for a MEMS-based infrared spectrometer using evanescent wave sensing

This paper presents the design and fabrication steps of a fully integrated spectrometer system based on attenuated total reflection. Operation is in the mid-infrared spectral range ( λ = 1.8–5 μm). The concept allows micromachined integration of all critical components of the system: a thermal IR source, optical filtering, the ATR element, a detector array and a signal-processing chip. Two bulk micromachined silicon dies are used. The source and detector array are fabricated in the bottom die. Polysilicon heaters on thin oxide–nitride bridges are used as the IR emitter and polysilicon thermocouples on thin membranes as IR detectors. The top die holds the bulk silicon ATR element, where at its surface the sample interacts with the evanescent field of the internally reflected IR beam. Other optical components, accurately defining the path of the IR light path, like gratings, mirrors, transmission filters, Fresnel lenses and slits can also be fabricated on the top die.

Cell-bionics: tools for real-time sensor processing

The accurate monitoring of the physiological status of cells, tissues and whole organisms demands a new generation of devices capable of providing accurate data in real time with minimal perturbation of the system being measured. To deliver on the promise of cell-bionics advances over the past decade in miniaturization, analogue signal processing, low-power electronics, materials science and protein engineering need to be brought together. In this paper we summarize recent advances in our research that is moving us in this direction. Two areas in particular are highlighted: the exploitation of the physical properties inherent in semiconductor devices to perform very low power on chip signal processing and the use of gene technology to tailor proteins for sensor applications. In the context of engineered tissues, cell-bionics could offer the ability to monitor the precise physiological state of the construct, both during 'manufacture' and post-implantation. Monitoring during manufacture, particularly by embedded devices, would offer quality assurance of the materials components and the fabrication process. Post-implantation monitoring would reveal changes in the underlying physiology as a result of the tissue construct adapting to its new environment.

Design for a Simplified Cochlear Implant System

A simplified cochlear implant (CI) system would be appropriate for widespread use in developing countries. Here, we describe a CI that we have designed to realize such a concept. The system implements 8 channels of processing and stimulation using the continuous interleaved sampling (CIS) strategy. A generic digital signal processing (DSP) chip is used for the processing, and the filtering functions are performed with a fast Fourier transform (FFT) of a microphone or other input. Data derived from the processing are transmitted through an inductive link using pulse width modulation (PWM) encoding and amplitude shift keying (ASK) modulation. The same link is used in the reverse direction for backward telemetry of electrode and system information. A custom receiver-stimulator chip has been developed that demodulates incoming data using pulse counting and produces charge balanced biphasic pulses at 1000 pulses/s/electrode. This chip is encased in a titanium package that is hermetically sealed using a simple but effective method. A low cost metal-silicon hybrid mold has been developed for fabricating an intracochlear electrode array with 16 ball-shaped stimulating contacts.

Digital hearing aids: A brief history

The journey leading to the development of digital hearing aids began at Bell Laboratories in the mid 1960s when a digital computer was used to simulate an experimental high gain telephone with frequency shaping for people with hearing loss. The simulation was off-line at about 100 times real time. About 20 years later, a digital master hearing aid operating in real time was developed using a high speed array processor. The development of wearable digital hearing aids followed soon after as high speed digital signal processing (DSP) chips were developed. The first wearable digital hearing aid was a body worn instrument and was not a commercial success. At this stage, digitally controlled analog hearing aids could be made small enough to be worn on the ear and these instruments were widely used by the end of the decade. During the 1990s, low-power DSP chips were developed that were small enough to allow for all-digital ear-worn hearing aids to be developed. The challenge today is to tap the tremendous potential of digital signal processing techniques within the power and size constraints of a practical, wearable instrument.

SAW chirp Fourier transform for MB-OFDM UWB receiver

In the conventional multiband orthogonal frequency division multiplexing ultra wideband (MB-OFDM UWB) receiver, the fast Fourier transform (FFT) algorithm is realized by the expensive and power-consuming digital signal processor (DSP) chips. In this article, the lower power, lower cost, and lower complexity real-time analog surface acoustic wave (SAW) chirp Fourier transform devices were used to replace the DSP part. A MB-OFDM UWB receiver based on the M-C-M SAW chirp Fourier transform was presented, and the step of signal transformation from input signals was also depicted. The simulation results show that the proposed receiver provides similar bit error performance compared to the fully digital receiver when used in the channel environments proposed by the IEEE 802.15SG3a.

Transmission of images over general packet radio services using advanced wavelet image codecs and digital signal processor chips

We develop a wavelet-based codec using a low-cost and low-energy-consuming 16-bit fixed-point digital signal processor (DSP). The target application is designed to grab an image from a camera, code the image using a wavelet-based codec, and send a coded file over a wireless global system for mobile communications/general packet radio services (GSM/GPRS) network. Since the channel capacity of the GSM/GPRS network is limited, a DSP with a relatively low computational power is sufficient to implement an image codec. A trade-off is made between the complexity and the efficiency of the wavelet-based image coder. Any implementation issues concerning the wavelet transform and entropy coding are discussed. Lifting schemes for a 9-7 and a 5-3 filter bank are used. The novel ordering of bit-plane bits is presented. The proposed codec is comparable with a JPEG2000 codec in the rate-distortion sense. The experimental results show that the implementation of JPEG 2000 on the presented platform runs 60% slower than the proposed codec. The coded file is transmitted over a wireless network using Internet protocol/user datagram protocol/trivial file transfer protocol (IP/UDP/TFTP).

Utilization of a unitary transform for efficient computation in the matrix pencil method to find the direction of arrival

In this study, we use the matrix pencil (MP) method to compute the direction of arrival (DOA) of the signals using a very efficient computational procedure in which the complexity of the computation can be reduced significantly by using a unitary matrix transformation. This method applies the technique directly to the data without forming a covariance matrix. Simulation results show that the variance of the estimate approaches to the Cramer-Rao lower bound. Using real computations through the unitary transformation for the MP method leads to a very efficient computational methodology for real time implementation on a digital signal processor chip. A unitary transform can convert the complex matrix to a real matrix along with their eigenvectors and thereby reducing the computational cost at least by a factor of four without sacrificing accuracy. This reduction in the number of computations is achieved by using a transformation, which maps centro-hermitian matrices to real matrices. This transformation is based on Lee's work on centro-hermitian matrices.

A resonant accelerometer with two-stage microleverage mechanisms fabricated by SOI-MEMS technology

We present the design, fabrication, and testing of a push-pull differential resonant accelerometer with double-ended-tuning-fork (DETF) as the inertial force sensor. The accelerometer is fabricated with the silicon-on-insulator microelectromechanical systems (MEMS) technology that bridges surface micromachining and bulk micromachining by integrating the 50-/spl mu/m-thick high-aspect ratio MEMS structure with the standard circuit foundry process. Two DETF resonators serve as the force sensor measuring the acceleration through a frequency shift caused by the inertial force acting as axial loading. Two-stage microleverage mechanisms with an amplification factor of 80 are designed for force amplification to increase the overall sensitivity to 160 Hz/g, which is confirmed by the experimental value of 158 Hz/g. Trans-resistance amplifiers are designed and integrated on the same chip for output signal amplification and processing. The 50-/spl mu/m thickness of the high-aspect ratio MEMS structure has no effect on the amplification factor of the mechanism but contributes to a greater capacitance force; therefore, the resonator can be actuated by a much lower ac voltage comparing to the 2-/spl mu/m-thick DETF resonators. The testing results agree with the designed sensitivity for static acceleration.

A 1-V analog CMOS front-end for detecting QRS complexes in a cardiac signal

A low-voltage low-power signal processing chip for electrocardiogram measurements has been designed and manufactured. The circuit includes a continuous time, offset-compensated preamplifier with an amplification of 40 dB, an eighth-order Butterworth switched-opamp switched-capacitor (SO-SC) filter with a passband of 8-30 Hz, a 32-kHz crystal oscillator, an SO-SC postamplifier, and a bias circuit. The whole circuit operates with supply voltages from 1.0 to 1.8 V and the measured average current consumption is only about 3 /spl mu/A. The circuit is therefore very suitable for portable applications such as heart rate detectors.

A DSP-Based Active Disturbance Rejection Control Design for a 1-kW H-Bridge DC–DC Power Converter

This paper presents the design and implementation of an advanced digital controller for a 1-kW H-bridge dc-dc power converter. A new control algorithm based on the active disturbance rejection concept is developed to cope with the highly nonlinear dynamics of the converter and the disturbances. An experimental digital control system is used to implement the new control strategy. It consists of a digital control board based on the TMS320C6711 digital signal processor chip, an analogy I/O board, and a complex programmable logic device pulsewidth-modulation generation board. Using a newly developed bandwidth-parametrization technique, an autotuning method based on noise quantification is also developed and tested. Experimental results show the advantages and flexibilities of the new control method for the H-bridge dc-dc power converter.

Multi channel voltage control for fuel cells

Cell voltage control is a safe method to evaluate the operation of the single cells even though large efforts are being made to stabilise the behaviour of the fuel cells over the whole operating range. For fully developed systems only voltage control of single cells is necessary, whereas in test benches it is necessary to record data of the voltages during operation. Normally, a lot of cells are combined to a stack so that higher total voltages can be reached. Higher voltages make possible a high efficient transformation from direct current of the stack to alternate current of the public network. Sometimes more than 100 cells are connected together whereby the open circuit voltage of a single cell amounts to approximately 1 V. Therefore, the signal processing chips show a high supply maximum rating or the resolution of the values has to be reduced. This paper presents an economically priced multi channel voltage control for single cells of a PEM-fuel cell in combination with a microprocessor control and was developed at the Chair for Electric Power Networks and Renewable Energy Sources. The developed system can transfer the data of up to 32 single cells in serial connection. The resolution amounts to 10 bits per channel. The module has its own microprocessor, which is responsible for the intermediate storage of the collected data and the transfer to the RS-232 interface. Optionally, the module can be equipped with an LCD-display of 20 × 4 letters where different menus of the measured and calculated values can be indicated. The module is designed for a voltage of 1 V per channel and can be supplied with a direct voltage of between 6 and 24 V from the fuel cell stack.