Showing papers on "Demodulation published in 2003"

Power supply system

Abstract: A power supply system is provided, having: a primary side coil; a power transmission apparatus having a primary side circuit for feeding a pulse voltage resulted from switching a DC voltage which is obtained by rectifying and smoothing a commercial power supply to the primary side coil; a secondary side coil magnetically coupled to the primary side coil; and power reception equipment having a secondary side circuit for rectifying and smoothing voltage induced across the secondary side coil, wherein there is provided a power adjusting section for adjusting a level of power to be transmitted according to power required by the power reception equipment. The power adjusting section has, in the primary side circuit, a carrier wave oscillation circuit for supplying a carrier wave to the primary side coil, a demodulation circuit for demodulating a modulated signal transmitted from the secondary circuit and received by the primary side coil, and a power change-over section for selecting a level of power to be transmitted according to an information signal from the power reception equipment and demodulated by the demodulation circuit. The power adjusting section has, in the secondary side circuit, a modulation circuit for modulating the carrier wave fed from the carrier wave oscillation circuit and received by the secondary side coil with the information signal from the power reception equipment and transmitting the modulated signal.

Chaos-based digital communication systems

Abstract: Publisher Summary This chapter reviews the common chaos-based digital modulation schemes. It also explains the corresponding coherent and noncoherent demodulation schemes. The two multiple-access schemes, based on the differential chaos-shift-keying (DCSK) or the frequency-modulated DCSK modulation (FM-DCSK), and the one multiple-access scheme based on the chaotic frequency modulation are also discussed. In the chaos-based communication systems, the detection schemes are broadly classified into the coherent and noncoherent types. The coherent systems require an exact replica of the chaotic carrier used to carry the information to be reproduced at the receiver, while the noncoherent systems have no such requirement. The chaos-based digital modulation schemes occupy a much wider bandwidth than is required to transmit a stream of binary symbols. Allowing multiple users to share the same bandwidth ensures an efficient use of the spectrum. When the chaos-shift-keying (CSK) signals are decoded based on the estimation of the bit energy, the threshold of the detector is expected to shift with the noise level. This leads to a large number of errors. The DCSK modulation scheme can be useful in overcoming such a problem.

Optical recording medium

Abstract: PROBLEM TO BE SOLVED: To improve access time without increasing manufacturing costs and without sacrificing a high-precision recording pulse. SOLUTION: A recording clock generation circuit 7 is provided with a PLL circuit provided with an oscillator and generating a recording pulse generation clock (SCLK) for generating a recording clock signal (WCLK) that is a synchronization signal for performing a prescribed modulation processing to recording data to be recorded on an optical disk 1 in synchronization with a wobble signal (WBL). A divider 8 divides the recording pulse generation clock signal to generate the recording clock signal. A synchronization detection circuit 12 and an address decoder 9 detect and demodulate the address signal recorded on the optical disk 1 in synchronization with the wobble signal with the recording clock signal. During seek to the outer circumference of the optical disk 1, the division ratio of the divider 8 is varied so that the frequency of the recording clock signal is lowered than that during seek to the inner circumference. COPYRIGHT: (C)2007,JPO&INPIT

Impulsive noise suppression in OFDM-based communication systems

Abstract: Orthogonal frequency division multiplexing (OFDM) is a technique used for terrestrial digital video broadcasting (DVB-T) and many other modern applications. The longer OFDM symbol duration provides an advantage in a presence of weak impulsive noise, because impulsive noise energy is spread among simultaneously transmitted OFDM sub-carriers. However, it has been recently recognized that this advantage turns into a disadvantage if the impulsive noise energy exceeds certain threshold. In this paper the algorithm for impulsive noise suppression in OFDM receivers is proposed and investigated. Whereas traditional methods for impulsive noise suppression are implemented in a time domain before OFDM demodulation, proposed algorithm compensates impulsive noise in a frequency domain after OFDM demodulation and channel equalization. The method is applied to DVB-T and its performance is studied by means of simulation.

Turbo synchronization: an EM algorithm interpretation

Abstract: This paper is devoted to turbo synchronization, that is to say the use of soft information to estimate parameters like carrier phase, frequency offset or timing within a turbo receiver. It is shown how maximum-likelihood estimation of those synchronization parameters can be implemented by means of the iterative expectation-maximization (EM) algorithm [A.P. Dempster, et al., 1977]. Then we show that the EM algorithm iterations can be combined with those of a turbo receiver. This leads to a general theoretical framework for turbo synchronization. The soft decision-directed ad-hoc algorithm proposed in V. Lottici and M. Luise, [2002] for carrier phase recovery turns out to be a particular instance of this implementation. The proposed mathematical framework is illustrated by simulations reported for the particular case of carrier phase estimation combined with iterative demodulation and decoding [S. ten Brink, et al., 1998].

Multi-pair gigabit ethernet transceiver

Abstract: Various systems and methods providing high speed decoding, enhanced power reduction and clock domain partitioning for a multi-pair gigabit Ethernet transceiver are disclosed. ISI compensation is partitioned into two stages; a first stage compensates ISI components induced by characteristics of a transmitter's partial response pulse shaping filter in a demodulator, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel in a Viterbi decoder. High speed decoding is accomplished by reducing the DFE depth by providing an input signal from a multiple decision feedback equalizer to the Viterbi based on a tail value and a subset of coefficient values received from a unit depth decision-feedback equalizer. Power reduction is accomplished by adaptively truncating active taps in the NEXT, FEXT and echo cancellation filters, or by disabling decoder circuitry portions, as channel response characteristics allow. A receive clock signal is generated such that it is synchronous in frequency with analog sampling clock signals and has a particular phase offset with respect to one of the sampling clock signals. This phase offset is adjusted such that system performance degradation due to coupling of switching noise from the digital sections to the analog sections is substantially minimized.

System and method for interference cancellation in a location calculation, for use in a wireless location system

Abstract: In a Wireless Location System, reception and demodulation of signals is often performed at many sites. A collision may occur, e.g., in a TDMA, AMPS, GSM, GPRS, EDGE, CDMA, CDMA 2000, or WCDMA system, when a signal of interest (a transmission from a mobile transmitter to be located) and an interfering signal are received at the same time and at the same site. In the event such a collision occurs, the interfering signal may have been demodulated by a receiver system, or SCS, at another site, and the demodulated data be known by the TLP. This interferer can be reconstructed and subtracted from the raw data representing the combined signal of interest and interferer at the site where the collision occurred. This technique can provide significant (e.g., approximately 10 - 15 dB) interference rejection, with little degradation to the signal of interest.

Quaternary optical ASK-DPSK and receivers with direct detection

Abstract: We present a novel quaternary optical-modulation scheme based on the combination of amplitude and phase modulation. The modulator has a simple structure and can be realized by using standard components. We present two simple receivers, each one using photodiodes for direct detection. The performance of the modulation scheme is investigated.

Filter structure for iterative signal processing

Abstract: The present invention relates to improved multiple access communications. In one form, the invention relates to an improved signal processing method and apparatus for an iterative method of determining the reception of a signal in a multi user packet based wireless OFDM (Orthogonal Frequency Division Multiplexing) communication system. In other forms the present invention provides recursive filtering for joint iterative decoding in a variety of systems and functions such as linear multiple access channel decoders, iterative equalisation, iterative joint channel estimation and detection/decoding, iterative space-time processing, iterative multi user interference cancellation and iterative demodulation. In one particular form the present invention provides an iterative decoding circuit for a wireless multiuser communications receiver comprising a first signal processing means for receiving at least one received signal, said first signal processing means comprising at least two linear iterative filters such that the first linear iterative filter provides an estimate of a selected received signal to an estimated signal output and a second linear iterative filter provides estimates of at least one other received signal, delayed by one iteration cycle, to an input of said first linear iterative filter, a second signal processing means for receiving the estimated signal output of the first linear iterative filter and providing a further received signal estimate to the input of the first signal processing means in a succeeding iteration cycle of the decoding circuit.

Method and apparatus for reducing coupling between signals

Abstract: A method and an apparatus for separating a composite signal into a plurality of signals is described. A signal processor receives a composite signal and separates a composite signal in to separate output signals. Feedback from one or more of the output signals is provided to a configuration module that configures the signal processor to improve a quality of the output signals. In one embodiment, the signal processor separates the composite signal by applying a first demodulation signal to the composite signal to generate a first output signal. In one embodiment, the signal processor also applies a second demodulation signal to the composite signal to generate a second output signal. In one embodiment, a phase and/or amplitude of the first demodulation signal and a phase and/or amplitude of the second demodulation signal are selected to reduce crosstalk. In one embodiment, the composite signal is obtained from a detector in a system for measuring one or more blood constituents.

Correlation image sensor: two-dimensional matched detection of amplitude-modulated light

Abstract: In this paper, we describe a novel imaging device, the correlation image sensor, whose pixel circuit consists of a photodetector and source-coupled MOS transistors with individual capacitive loads and readout switches. It accepts differential or three-phase reference signals to produce one or two correlation integrals between the incident light intensity and the reference signals. The correlation results stored as charges in the capacitors are read out via MOS scanning circuits. We describe a functional model of the circuit and a quadrature detection method of amplitude-modulated light. We fabricated 64/spl times/64 and 100/spl times/100 pixel devices and obtained a correlation signal-to-noise ratio of 34 dB and a phase accuracy of 0.85/spl deg/ using only two-frame integration. We also describe application methods of this sensor to cross-correlation imagers, amplitude modulation-phase modulation demodulation imagers, and correlation matching imagers.

Single-crystal sapphire fiber-based strain sensor for high-temperature applications

Abstract: Single-crystal sapphire fibers have a very high melting point (up to 2050/spl deg/C), which renders them a very good candidate for sensing applications at a very high temperature. We present in this paper the recent work of developing single-crystal sapphire fiber extrinsic Fabry-Perot interferometric strain sensors based on the white-light interferometric spectrum demodulation technique. Prototype sapphire strain sensors were fabricated and tested at high temperatures up to 1004/spl deg/C. The preliminary experimental results indicate that the sensors are promising to be used under high-temperature environments for making strain measurements with strain measurement resolution of 0.2-/spl mu/ strain.

Demonstration of 42.7-Gb/s DPSK receiver with 45 photons/bit sensitivity

Abstract: A record sensitivity of -36.2 dBm at 1552.5-nm wavelength (45 photons/bit) is reported for an optically preamplified receiver operating at 42.7 Gb/s. The transmission format is return-to-zero differential phase-shift keying. The receiver employs a delay-interferometer demodulator followed by balanced-photodiode detection and electronic demultiplexing to 10.7 Gb/s.

Self-booting software defined radio module

Abstract: The invention in the simplest form is a self-booting software defined radio (SDR) module which may be embodied as a PCMCIA, Compact Flash, or other plug in form factor module. The performance characteristics of the module, may include the radio frequency (RF) carrier frequency, instantaneous RF bandwidth, carrier modulation and demodulation, symbol coding and decoding, security, and network protocol that can be altered and saved by means of computer software transferred to the module from a host device such as a cellular telephone, personal digital assistant, lap top computer or other programming device.

Efficient implementation of sphere demodulation

Abstract: We provide new results on the sphere demodulator (SD) and its new variant, the list sphere demodulator (LSD). A new reduced complexity SD algorithm is presented. We suggest implementing the necessary sorting of constellation symbols through a look up table. In addition, we propose the use of a modified QR algorithm which tries to begin the search in the layers which are "easier to demodulate". These improvements also apply to the recently published soft output LSD, in which we implement the list using the heap structure.

A new class of soft MIMO demodulation algorithms

Abstract: We propose a new class of soft-input soft-output demodulation schemes for multiple-input multiple-output (MIMO) channels, based on the sequential Monte Carlo (SMC) framework under both stochastic and deterministic settings. The stochastic SMC sampler generates MIMO symbol samples based on importance sampling and resampling techniques, whereas the deterministic SMC approach recursively performs exploration and selection steps in a greedy manner. By exploiting the artificial sequential structure of the existing simple Bell-Labs layered space-time (BLAST) detection method based on nulling and cancellation, the proposed algorithms achieve an error probability performance that is orders of magnitude better than the traditional BLAST detection schemes while maintaining a low computational complexity. In fact, the new methods offer performance comparable with that of the sphere decoding algorithm without attendant increase in complexity. More importantly, being soft-input soft-output in nature, both the stochastic and deterministic SMC detectors can be employed as the first-stage demodulator in a turbo receiver in coded MIMO systems. Such a turbo receiver successively improves the receiver performance by iteratively exchanging the so-called extrinsic information between the soft outer channel decoder and the inner soft MIMO demodulator under both known channel state and unknown channel state scenarios. Computer simulation results are provided to demonstrate the performance of the proposed algorithms.

A 1.5-V 45-mW direct-conversion WCDMA receiver IC in 0.13-/spl mu/m CMOS

Abstract: A 2-GHz direct-conversion receiver for wide-band code division multiple access (WCDMA) is presented. It includes two low-noise amplifiers (LNAs), an I/Q demodulator, and two sixth-order baseband channel select filters with programmable gain. Quadrature local oscillator (LO) signals are generated on chip in a frequency divider flip-flop. An external interstage filter between the LNAs rejects transmitter leakage to relax demodulator linearity requirements. A low-voltage demodulator topology improves linearity as well as demodulator output pole accuracy. The active-RC baseband filter uses a programmable servo loop for offset compensation and provides an adjacent channel rejection of 39 dB. Programmable gain over 71-dB range in 1-dB steps is merged with the filter to maximize dynamic range. An automatic on-chip frequency calibration scheme provides better than 1.5% corner frequency accuracy. The receiver is integrated in a 0.13-/spl mu/m CMOS process with metal-insulator-metal (MIM) capacitors. Measured receiver performance includes a 6.5-dB noise figure, IIP2 of +27 dBm, and IIP3 of -8.6 dBm. Power consumption is 45 mW.

A new concept for wireless reconfigurable receivers

Abstract: In this article we present the Self-Adaptive Universal Receiver (SAUR), a novel wireless reconfigurable receiver architecture. This scheme is based on blind recognition of the system in use, operating on a new radio interface comprising two functional phases. The first phase performs a wideband analysis (WBA) on the received signal to determine its standard. The second phase corresponds to demodulation. Here we only focus on the WBA phase, which consists of an iterative process to find the bandwidth compatible with the associated signal processing techniques. The blind standard recognition performed in the last iteration step of this process uses radial basis function neural networks. This allows a strong analogy between our approach and conventional pattern recognition problems. The efficiency of this type of blind recognition is illustrated with the results of extensive simulations performed in our laboratory using true data of received signals.

A 3-V, 0.35-/spl mu/m CMOS Bluetooth receiver IC

Abstract: A fully integrated CMOS low-IF Bluetooth receiver is presented The receiver consists of a radio frequency (RF) front end, a phase-locked loop (PLL), an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, and a frequency offset cancellation circuit The highlights of the receiver include a low-power active complex filter with a nonconventional tuning scheme and a high-performance mixed-mode GFSK demodulator The chip was fabricated on a 625-mm/sup 2/ die using TSMC 035-/spl mu/m standard CMOS process -82 dBm sensitivity at 1e-3 bit error rate, -10 dBm IIP3, and 15 dB noise figure were achieved in the measurements The receiver active current is about 65 mA from a 3-V power supply

Inductively-coupled power and data link for neural prostheses using a class-E oscillator and FSK modulation

Abstract: Despite the success of implantable batteries as commonly used in pacemakers, implantable neural prosthetic devices typically have power requirements that exceed the capability of reasonably-sized implantable batteries. Therefore, transcutaneous magnetic coupling remains the method of choice for powering implanted neural prostheses. Using the same inductive link for transfer of power and bidirectional telemetry is an attractive solution to powering and communicating with implanted devices thus avoiding percutaneous plugs, wires, or conduits. The Class-E power oscillator has been identified as a highly-efficient transmitter circuit for use as a means of transferring power to an implant. Although the high-Q nature of this topology makes rapid modulation difficult, it is feasible to use synchronous frequency-shift-keyed (FSK) modulation of the Class-E circuit thereby combining an efficient power transmitter with a highspeed data link. Using this method, the transmitter can be modulated on a cycle-by-cycle basis with little to no additional power loss. Within an implanted device, demodulation of the FSK transmitted carrier can be accomplished using a novel demodulation circuit.

Method and apparatus for physiological data acquisition via sound input port of computing device

Abstract: A sound input port is ubiquitously present in many types of devices including PCs, PDAs, cell phones, land line phones, and voice recorders thereafter referred to as “computing devices”. A sound port allows data input into a computing device for further computation, visualization and data transmission. Unfortunately most computing devices only allow one channel of data acquisition via the sound port. Further, the acquired data are highpass filtered. A method of extending the signal range to very low frequencies and recording a plurality of data channels via a single sound port is disclosed here. This method uses amplitude modulation of carrier frequencies to create a composite signal. The composite signal is then transmitted into the computing device either via wire or wirelessly. Demodulation occurs in the computing device. In the preferred embodiment the audio signal from an electronic stethoscope and the amplitude modulated EKG are transmitted into a computer via a single microphone port. In an alternative embodiment physiological data from multiple sensors are transmitted into a computer via a single microphone port.

Antenna transmission and reception system

Abstract: A transmitter of a base station includes a data serial-to-parallel converter, M modulators, M beam formers, and transmission antennas. The data serial-to-parallel converter converts transmission data into M sequences. Each modulator modulates the transmission data. Each beam former weights the modulation signal to form directional beams. The transmission antennas narrow the beams and transmit the modulation signals in parallel (MIMO transmission). In a mobile station, a receiver has reception antennas for receiving data transmitted in parallel and an MIMO demodulator for demodulating the data.

On optimal data detection for UWB transmitted reference systems

Abstract: Transmitted reference (TR) modulation schemes, initially proposed for spread-spectrum systems in the 1920's have regained popularity in the context of ultra-wideband (UWB) communications, where accurate channel estimation is a challenging task. In the conventional TR approach, a reference signal (without data modulation) is received and employed in a correlator receiver for data modulated signals. By exploiting the statistics of the received signals, optimal and suboptimal data detection schemes for a single-user UWB communication system employing antipodal modulation with TR are investigated and compared to the conventional TR receiver. The proposed schemes can cope with a variable number of reference and data modulated pulses. By construction, the modulation and demodulation methods work for arbitrary channels. The efficacy of the new methods is investigated via simulations emulating an indoor multipath channel. These simulation results reveal that the proposed detection schemes provide significant performance improvements in terms of bit error rate over the conventional TR receiver structure.

Lattice Decoding for Joint Detection in Direct-Sequence

Abstract: A new joint detection method based on sphere packing lat- tice decoding is presented in this paper. The algorithm is suitable for both synchronous and asynchronous multiple access direct-sequence code-divi- sion multiple-access (DS-CDMA) systems, and it may jointly detect up to 64 users with a reasonable complexity. The detection complexity is indepen- dent of the modulation size and large -PAM or -QAM constellations can be used. Furthermore, a theoretical gain analysis is performed in which the multiple-access system performance is derived from the lattice param- eters. Index Terms—Code-division multiple access (CDMA), lattice decoding, multiuser detection, sphere decoder. In this correspondence, a new low-complexity joint detection algo- rithm for direct sequence (DS) multiple-access systems is proposed. The algorithm is optimal (in the maximum-likelihood (ML) sense) for synchronous code-division multiple-access (CDMA) systems. The re- ceiver models the despreader output as a multidimensional lattice point (sphere packing) corrupted by noise and applies a lattice-decoding al- gorithm to jointly detect all users. In the asynchronous case, the lattice decoder is combined with an interference canceler and its performance remains excellent despite its suboptimality. The paper is organized as follows. In Section II, the synchronous multiple-access transmitter structure and its lattice representation are described. In Section III, the sphere-decoding algorithm, which is a low-complexity ML decoder for lattice constellations, is presented. Then, sphere decoding is applied to ML detection of synchronous direct-sequence spread-spectrum multiple access (DS-SSMA) in Section IV. In Section V, the combination of sphere decoding and interference cancellation for the joint demodulation of asynchronous DS-SSMA is investigated. In Section VI, an analytical approximation for the system gain is derived from the lattice parameters. Simulation results for synchronous and asynchronous systems on additive white Gaussian noise (AWGN) channel are presented in Section VII and compared with those of multistage successive interference cancella- tion (PIC) (13), (14), decision-feedback minimum mean-square error detector (DF-MMSE) (9), and Viterbi-based algorithm (Verdu joint detector (15)). Conclusions are finally drawn in Section VIII.

AC power source light modulation network

Abstract: An AC power source light modulation apparatus is used for broadcasting useful data from a computer system to one or more specialized optical detectors located within any given space illuminated by standard electrical light fixtures all connected downstream from this same power source. The AC power modulation impressed by this system on the power signal, causes imperceptible changes to the light output of electrical lamps being supplied electricity from this common AC power source. This invention may be installed at any AC power source located upstream of one or more standard light fixtures in order to induce changes that may include deltas in amplitude and phase in the luminous output of these light fixtures. Changes in the electrical ambient illumination are produced by this modulated power signal which result in the broadcasting of optical signals that are received, demodulated and decoded by a specialized type of optical data receiver. This optical data broadcasting network includes a new type of optical networking card or optical receiver, capable of demodulation and decoding changes in the characteristics of the light output of the electrical lamps, which are generally imperceptible to the human eye. The AC power source light modulation apparatus and the optical receiver units comprise an optical data broadcasting network that provides a low-cost and single-point installation for applications where the lowest cost and the simplest indoor wireless infrastructure is desirable by users. Including applications such as the automation of prices in retail and supermarkets and for use by other applications that require optical communications for data broadcasting and remote wireless networking systems.

Data detection and demodulation for wireless communication systems

Abstract: Techniques for detecting and demodulating data transmissions in wireless communication systems. In one aspect, a decision-directed detector detects for data transmissions in a received signal by utilizing received data symbols as well as received pilot symbols. The decision-directed detector may be designed to perform differential detection in the frequency domain or coherent detection in the time domain, and may be used with multi-carrier modulation (e.g., OFDM). In another aspect, an adaptive threshold is used to perform detection of received data transmissions. A threshold may be determined for each data transmission hypothesized to have been received. The threshold may be computed, for example, based on the signal plus noise energy of the hypothesized data transmission.

Image-rejection I/Q demodulators

Abstract: In a communications receiver for quadrature demodulation, a feedback technique for reducing the image response of the receiver. The communications receiver includes an I demodulator and a Q demodulator. A local oscillator (LO) signal is provided by a PLL to a quadrature LO generator that provides an LO_I signal to an I demodulator and an LO_Q signal to a Q demodulator. The LO_I and LO_Q signals are amplitude and phase-controlled versions of the LO signal. An image/signal ratio (I/S) detector detects the relative phase difference and the relative amplitude difference between the respective output terminals of the I demodulator and the Q demodulator and applies an amplitude control signal and a phase control signal to corresponding amplitude control and phase control inputs of the quadrature LO generator. The I/S detector calibrates the quadrature LO generator during the interstitial interval between the reception of data packets. The control signals from the I/S detector adjust the relative amplitude and phase of the LO_I and LO_Q signals in a manner that reduces the image response of the communications receiver.

Multi-carrier watermarks using carrier signals modulated with auxiliary messages

Abstract: A watermark embedder encodes auxiliary information, such as a binary message, into a host media signal by modulating message signals with two or more corresponding carrier signals to form a watermark signal and embeds this signal into the host. A compatible watermark decoder uses the carrier signals to demodulate the message signals from the watermarked signal.