Showing papers on "Demodulation published in 2004"

Coherent detection method using DSP for demodulation of signal and subsequent equalization of propagation impairments

Abstract: A new approach to coherent detection is demonstrated which achieves the same high sensitivity as homodyne detection but without the need to phase lock the local oscillator laser. In addition, 1470 ps/nm of chromatic dispersion is compensated with zero net penalty by electronic domain equalization, a result which has not been achieved before because zero-penalty equalization is not possible after direct detection. The method proposes the use of high-speed digital signal processing technology, and the experimental results are obtained using burst-mode sampling followed by offline signal processing.

A wideband frequency-shift keying wireless link for inductively powered biomedical implants

Abstract: A high data-rate frequency-shift keying (FSK) modulation protocol, a wideband inductive link, and three demodulator circuits have been developed with a data-rate-to-carrier-frequency ratio of up to 67%. The primary application of this novel FSK modulation/demodulation technique is to send data to inductively powered wireless biomedical implants at data rates in excess of 1 Mbps, using comparable carrier frequencies. This method can also be used in other applications such as radio-frequency identification tags and contactless smartcards by adding a back telemetry link. The inductive link utilizes a series-parallel inductive-capacitance tank combination on the transmitter side to provide more than 5 MHz of bandwidth. The demodulator circuits detect data bits by directly measuring the duration of each received FSK carrier cycle, as well as derive a constant frequency clock, which is used to sample the data bits. One of the demodulator circuits, digital FSK, occupies 0.29 mm/sup 2/ in the AMI 1.5-/spl mu/m, 2M/2P, standard CMOS process, and consumes 0.38 mW at 5 V. This circuit is simulated up to 4 Mbps, and experimentally tested up to 2.5 Mbps with a bit error rate of 10/sup -5/, while receiving a 5/10-MHz FSK carrier signal. It is also used in a wireless implantable neural microstimulation system.

DVB‐S2 modem algorithms design and performance over typical satellite channels

Abstract: SUMMARY In this paper we propose a design of the main modulation and demodulation units of a modem compliant with the new DVB-S2 standard (Int. J. Satellite Commun. 2004; 22:249–268). A typical satellite channel model consistent with the targeted applications of the aforementioned standard is assumed. In particular, non-linear pre-compensation as well as synchronization techniques are described in detail and their performance assessed by means of analysis and computer simulations. The proposed algorithms are shown to provide a good trade-off between complexity and performance and they apply to both the broadcast and the unicast profiles, the latter allowing the exploitation of adaptive coding and modulation (ACM) (Proceedings of the 20th AIAA Satellite Communication Systems Conference, Montreal, AIAA-paper 2002-1863, May 2002). Finally, end-to-end system performances in term of BER versus the signal-to-noise ratio are shown as a result of extensive computer simulations. The whole communication chain is modelled in these simulations, including the BCH and LDPC coder, the modulator with the pre-distortion techniques, the satellite transponder model with its typical impairments, the downlink chain inclusive of the RF-front-end phase noise, the demodulator with the synchronization sub-system units and finally the LDPC and BCH decoders. Copyright # 2004 John Wiley & Sons, Ltd.

Performance analysis and design optimization of LDPC-coded MIMO OFDM systems

Abstract: We consider the performance analysis and design optimization of low-density parity check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems for high data rate wireless transmission. The tools of density evolution with mixture Gaussian approximations are used to optimize irregular LDPC codes and to compute minimum operational signal-to-noise ratios (SNRs) for ergodic MIMO OFDM channels. In particular, the optimization is done for various MIMO OFDM system configurations, which include a different number of antennas, different channel models, and different demodulation schemes; the optimized performance is compared with the corresponding channel capacity. It is shown that along with the optimized irregular LDPC codes, a turbo iterative receiver that consists of a soft maximum a posteriori (MAP) demodulator and a belief-propagation LDPC decoder can perform within 1 dB from the ergodic capacity of the MIMO OFDM systems under consideration. It is also shown that compared with the optimal MAP demodulator-based receivers, the receivers employing a low-complexity linear minimum mean-square-error soft-interference-cancellation (LMMSE-SIC) demodulator have a small performance loss (< 1dB) in spatially uncorrelated MIMO channels but suffer extra performance loss in MIMO channels with spatial correlation. Finally, from the LDPC profiles that already are optimized for ergodic channels, we heuristically construct small block-size irregular LDPC codes for outage MIMO OFDM channels; as shown from simulation results, the irregular LDPC codes constructed here are helpful in expediting the convergence of the iterative receivers.

Method and apparatus to configure an RFID system to be adaptable to a plurality of environmental conditions

Abstract: An RFID integrated circuit includes a demodulator to receive a first signal, the first signal having been generated by an RFID reader responsive to detection of a first environmental condition. The RFID integrated circuit further includes a controller to set, based on the first signal, a modulation format for the RFID integrated circuit and to configure the RFID integrated circuit to modulate a backscatter signal according to the modulation format.

Semiconductor integrated circuit device

Abstract: The semiconductor integrated circuit (RF IC) for a mobile telephone capable of transmitting/receiving the signals of plural bands reduces the DC offsets of the amplifiers located in the following stages of the mixers that demodulate or down-convert the reception signals The invention scrambles the signal lines to transmit the outputs of the plural mixers that demodulate or down-convert the reception signals of different bands, so as to avoid the adjacent signal lines from making the same combination from the starting ends to the finishing ends

Ultrasonic diagnostic apparatus

Abstract: Encoded transmission and reception which reduces time side lobe are realized while suppressing increase of circuit scale. Transmission signals corresponding to a composite modulation code sequence composed from two or more modulation code sequences are outputted as transmission signals. A reception means demodulates reception signals stepwise by two or more demodulators. The demodulator can be thereby divided into two or more stages, and therefore with a circuit scale corresponding to the sum of the operation circuit numbers of two or more demodulators, time side lobe reduction effect can be obtained at a level equivalent to that obtainable with a circuit scale corresponding to the product of the operation circuit numbers of two or more demodulators.

Equalization and decision-directed loops with trellis demodulation in high definition TV

Abstract: Improved decision feedback equalizer and decision directed timing recovery systems and methods suitable for use in connection with a dual mode QAM/VSB receiver system are disclosed. A trellis decoder operates in conjunction with a decision feedback equalizer circuit on trellis coded 8-VSB modulated signals. The trellis decoder includes a 4-state traceback memory circuit outputting a maximum likelihood decision as well as a number of intermediate decisions based upon the maximum likelihood sequence path. Any number of decisions, along the sequence, may be provided as an input signal to timing recovery system loops, with the particular decision along the sequence chosen on the basis of its delay through the trellis decoder. Variable delay circuitry is coupled to the other input of the timing recovery system loops in order to ensure that both input signals bear the same timestamp. Final decisions are output from the trellis decoder to a DFE in order to enhance the DFE's ability to operate in low SNR environments. A decision sequence estimation error signal is also generated and used to drive the tap updates of both the DFE and an FFE portion of the equalizer.

Impact of chromatic and polarization-mode dispersions on DPSK systems using interferometric demodulation and direct detection

Abstract: We study the impact of chromatic dispersion (CD) and first-order polarization-mode dispersion (PMD) on systems using binary differential phase-shift keying (2-DPSK) or quaternary DPSK (4-DPSK) with nonreturn-to-zero (NRZ) or return-to-zero (RZ) formats. These signals are received using optical preamplification, interferometric demodulation, and direct detection. We consider the linear propagation regime and compute optical power penalties at fixed bit-error ratio (BER). In order to evaluate the BER precisely taking account amplifier noise, arbitrary pulse shapes, arbitrary optical and electrical filtering, CD, and PMD, we introduce a novel model for DPSK systems and compute the BER using a method recently proposed by Forestieri for on-off keying (OOK) systems. We show that when properly applied, the method yields highly accurate results for DPSK systems. We have found that when either the NRZ or RZ format is used, 2-DPSK exhibits lower power penalties than OOK in the presence of CD and first-order PMD. RZ-2-DPSK, as compared with NRZ-2-DPSK, incurs smaller penalties due to PMD, but offers no advantage in terms of CD. 4-DPSK, as it has twice the symbol duration of OOK or 2-DPSK for a given bit rate, incurs much lower CD and PMD power penalties than either of these techniques. RZ-4-DPSK is especially promising, as it offers CD and PMD penalties significantly smaller than all other techniques, including NRZ-4-DPSK.

An impulse radio asynchronous transceiver for high data rates

Abstract: The purpose of this paper is to provide an operative way of achieving high data rates for impulse radio (IR) transmission based systems. Since applications targeted for ultra wide band (UWB) are liable to be low-cost, we especially focus on simple transceiver design. To that effect, we present an original demodulation scheme adapted to a multi-band ON-OFF keying modulation. From the receiver point of view, we impose relaxed channel estimation constraints and derive suitable signal processing schemes and simple hardware architectures. Indeed, we only consider the benefit from a limited a priori channel knowledge: approximative delay spread and energy level. The associated optimum demodulation turns out to be a non-trivial energetic threshold comparison whose precise theoretical computation admits an analytical solution proving its feasibility. Numerical results are eventually performed for IEEE 802.15.3a channel models and FCC requirements; they obviously demonstrate the potential of these techniques.

Modulation classification in fading channels using antenna arrays

Abstract: Blind modulation classification (MC) is an intermediate step between signal detection and demodulation, and plays a key role in various civilian and military applications. In this paper, first we provide an overview of decision-theoretic MC approaches. Then we derive the average likelihood ratio (ALR) based classifier for linear and nonlinear modulations, in noisy channels with unknown carrier phase, offset and also in Rayleigh fading channels. Since these ALR-based classifiers are complex to implement, we then develop a quasi hybrid likelihood ratio (QHLR) based classifier, where the unknown parameters are estimated using low-complexity techniques. This QHLR-based classifier is much simpler to implement and is also applicable to any fading distribution, including Rayleigh and Rice. Afterwards, we propose a generic multi-antenna classifier for linear and nonlinear modulations, using an antenna array at the receiver. This classifier has the potential to improve the performance of traditional single-antenna classifiers, including the proposed QHLR-based algorithm, via spatial diversity. Simulation results are provided to show the performance enhancement offered by the new QHLR-based multi-antenna classifier, in a variety of channel and fading conditions.

Constant envelope OFDM phase modulation: spectral containment, signal space properties and performance

Abstract: A class of constant envelope OFDM phase modulated (OFDM-PM) signals is studied. The motivation behind OFDM-PM is to alleviate the high peak-to-average power ratio of conventional OFDM systems. Power density spectrum plots and fractional out-of-band power curves are given. For small modulation indices, the OFDM-PM signals are shown to be more spectrally contained than conventional OFDM. The signal space is studied by considering the correlation properties of the OFDM-PM signals. A performance bound on the optimum OFDM-PM receiver is compared to simulation results. Also, a sub-optimum phase demodulator receiver is analyzed and an AWGN performance approximation is compared to simulation results. It is shown that for a small modulation index and high signal-to-noise ratio, the sub-optimum receiver performs close to the optimum receiver.

An efficient MMSE-based demodulator for MIMO bit-interleaved coded modulation

Abstract: In bit-interleaved coded modulation (BICM) systems employing maximum-likelihood decoding, a demodulator (demapper) calculates a log-likelihood ratio (LLR) for each coded bit, which is then used as a bit metric for Viterbi decoding. In the MIMO case, the computational complexity of LLR calculation tends to be excessively high, even if the log-sum approximation is used. Thus, there is a strong demand for efficient suboptimum MIMO-BICM demodulation algorithms with near-optimum performance. We propose an efficient MIMO-BICM demodulator that is derived by means of a Gaussian approximation for the post-detection interference. Our derivation results in an MMSE equalizer followed by per-layer LLR calculation (i.e., LLRs are calculated separately for each layer). The novel demodulator can be interpreted as an MMSE analogue of a recently proposed ZF-equalization based demodulator, as well as an extension of ZF-equalization based demodulation to correlated post-detection interference. Because it performs per-layer LLR calculation, it has the same (low) computational complexity as the ZF-equalization based demodulator. Simulation results demonstrate that the performance of our demodulator is close to that of LLR calculation using all layers jointly, and significantly better than that of the ZF-equalization based demodulator.

Cooperative diversity for wireless fading channels without channel state information

Abstract: Relaying and cooperative diversity allow multiple wireless radios to effectively share their antennas and create a virtual antenna array, thereby leveraging the spatial diversity benefits of multiple-input, multiple-output (MIMO) antenna systems. This paper examines the benefits of cooperative diversity for scenarios in which the receivers cannot exploit accurate channel state information (CSI). In particular, noncoherent demodulation is explored for two classes of relay processing, namely, detect-and-forward and amplify-and-forward. A complete maximum likelihood (ML) framework for noncoherent demodulation is developed for detect-and-forward, and is shown to naturally extend the corresponding framework for coherent demodulation. By contrast, the intractability of ML demodulation for noncoherent amplify-and-forward is demonstrated, suggesting a disconnect from the well-developed framework for coherent demodulation. Simulation results exhibit the diversity benefits of the detect-and-forward algorithms.

Wide-band QAM-over-fiber using phase modulation and interferometric demodulation

Abstract: Transmission of microwave quadrature amplitude modulation over an all-Raman 105-km fiber-optic link is demonstrated. The link employs optical phase modulation and single-port interferometric demodulation to deliver up to 6 Gb/s in a single channel.

On power allocation strategies for maximum signal to noise and interference ratio in an OFDM-MIMO system

Abstract: Orthogonal frequency division multiplexing (OFDM) has been recently established for several systems such as HiperLAN/2 and Digital video/audio broadcasting, due the easy implementation of the modulator/demodulator and the equalizer. Moreover, also increasing interest is currently being put on multiple-input multiple-output (MIMO) channels, based on the use of antenna arrays at both the transmitter and the receiver. Here, we propose two joint beamforming strategies of low computational load for systems combining OFDM and MIMO. The ultimate objective is the maximization of the signal-to-noise and interference ratio (SNIR) over the carriers subject to a total transmit power constraint. Specifically, the maximization of the harmonic SNIR mean and the minimum SNIR over the subcarriers are proposed. The asymptotic behavior of the proposed methods is analyzed to provide a complete comparative and general view of the most relevant and already known transmit power allocation strategies. Finally, a theoretical analysis of the performance degradation of these techniques is carried out for the case in which the channel state information (CSI) is not perfect. Monte Carlo simulation results for the system bit-error rate and performance degradation with imperfect CSI are provided.

Adaptive receivers for bit rate agile (BRA) and modulation demodulation (modem) format selectable (MFS) signals

Abstract: Systems, apparatus, and methods for new generations of wireless systems, including multiple standard, interoperable Third-Generation (3G) and Second-Generation (2G), Spread Spectrum CDMA, WCDMA, GSM, Enhanced GSM systems and CSMA, TDMA and OFDM. Bit Rate Agile (BRA), Modulation and Code Selectable processing techniques of Gaussian Minimum Shift Keying (GMSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and of Mis-Matched demodulator filters in which the demodulator filter set is mismatched to the filter set of the signal modulator.

Steering of directional sound beams

Abstract: Apparatus is disclosed for steering a directional audio beam that is self-demodulated from an ultrasound carrier The apparatus includes means for modulating a carrier signal with an audio signal and means for adjusting the amplitude and phase of at least one of the audio signal and/or the carrier signal to steer the audio beam to a desired direction The apparatus also includes means for generating an ultrasound beam in the desired direction driven by the modulated carrier signal The apparatus may include means for weighting the audio and/or carrier signal by a zeroth order Bessel function to synthesize a Bessel distribution source A corresponding method for steering a directional audio beam is also disclosed A harmonic generator may be used to generate harmonics of low frequencies in the audio signal The harmonics may provide (upon demodulation) a psycho-acoustic impression of improved perception of low frequencies Further, a modulated ultrasonic signal or an unmodulated audio signal may be band-passed into two or more different band-limited signals The band-limited signals may be amplified and transmitted by ultrasonic transducers having mechanical resonance frequencies substantially equal to a characteristic frequency of the band-limited signals Ultrasonic processing of the audio signal may include square root methods without generating large numbers of harmonics

An orthogonal space-time coded CPM system with fast decoding for two transmit antennas

Abstract: Trellis-coded space-time (TC-ST) coding for continuous-phase modulation (TC-ST-CPM) was recently proposed by Zhang and Fitz. In this paper, we propose an orthogonal space-time coding for CPM (OST-CPM) systems and two transmit antennas. In the proposed OST-CPM, signals from two transmit antennas at any time t are orthogonal while both of them have continuous phases. Similar to Alamouti's OST coding for phase-shift keying (PSK) and quadrature amplitude modulation (QAM) systems, the newly proposed OST-CPM has a fast decoding algorithm.

Direct sampled I/Q beamforming for compact and very low-cost ultrasound imaging

Abstract: A wide variety of beamforming approaches are applied in modern ultrasound scanners, ranging from optimal time domain beamforming strategies at one end to rudimentary narrowband schemes at the other. Although significant research has been devoted to improving image quality, usually at the expense of beamformer complexity, we are interested in investigating strategies that sacrifice some image quality in exchange for reduced cost and ease in implementation. This paper describes the direct sampled in-phase/quadrature (DSIQ) beamformer, which is one such low-cost, extremely simple, and compact approach. DSIQ beamforming relies on phase rotation of I/Q data to implement focusing. The I/Q data are generated by directly sampling the received radio frequency (RF) signal, rather than through conventional demodulation. We describe an efficient hardware implementation of the beam-former, which results in significant reductions in beam-former size and cost. We present the results of simulations and experiments that compare the DSIQ beamformer to more conventional approaches, namely, time delay beamforming and traditional complex demodulated I/Q beam-forming. Results that show the effect of an error in the direct sampling process, as well as dependence on signal bandwidth and system f number (f#) are also presented. These results indicate that the image quality and robustness of the DSIQ beamformer are adequate for low end scanners. We also describe implementation of the DSIQ beamformer in an inexpensive hand-held ultrasound system being developed in our laboratory.

Digital signal demodulation of an OFDM signal with error correction

Abstract: A digital signal demodulator digitizes an OFDM signal at a sampling frequency from a sampling oscillator to produce a digital OFDM signal. The digital OFDM signal is converted into I and Q components using a carrier frequency from a carrier oscillator. The IQ components are transformed into digital complex symbols, and pilot signals are extracted from the complex symbols. A processor calculates an inter-symbol difference of phase differences between pilot signals to control the sampling oscillator to correct the sampling frequency; calculates an inter-symbol difference for one of the pilot signals to control the carrier oscillator to correct the carrier frequency; and calculates a phase angle for one of the subcarriers at a frequency in the middle of the plurality of subcarriers for the OFDM signal to control the carrier oscillator to correct the carrier frequency phase.

Contemporary communication systems using MATLAB and Simulink

Abstract: 1. SIGNALS AND LINEAR SYSTEMS. Preview. Fourier Series. Fourier Transforms. Power and Energy. Lowpass Equivalent of Bandpass Signals. 2. RANDOM PROCESSES. Preview. Generation of Random Variables. Gaussian and Gauss-Markov Processes. Power Spectrum of Random Processes and White Processes. Linear Filtering of Random Processes. Lowpass and Bandpass Processes. 3. ANALOG MODULATION. Preview. Amplitude Modulation (AM). Demodulation of AM Signals. Angle Modulation. 4. ANALOG-TO-DIGITAL CONVERSION. Preview. Measure of Information. Quantization. Pulse-Code Modulation. 5. BASEBAND DIGITAL TRANSMISSION. Preview. Binary Signal Transmission. Multiamplitude Signal Transmission. Multidimensional Signals. 6. DIGITAL TRANSMISSION THROUGH BANDLIMITED CHANNELS. Preview. The Power Spectrum of a Digital PAM Signal. Characterization of Bandlimited Channels and Channel Distortion. Characterization of Intersymbol Interference. Communication System Design for Bandlimited Channels. Linear Equalizers. Nonlinear Equalizers. 7. DIGITAL TRANSMISSION VIA CARRIER MODULATION. Preview. Carrier-Amplitude Modulation. Carrier-Phase Modulation. Quadrature Amplitude Modulation. Carrier-Frequency Modulation. Synchronization in Communication Systems. 8. CHANNEL CAPACITY AND CODING. Preview. Channel Model and Channel Capacity. Channel Coding. 9. SPREAD SPECTRUM COMMUNICATION SYSTEMS. Preview. Direct-Sequence Spread Spectrum Systems. Generation of PN Sequences. Frequency-Hopped Spread Spectrum.

Capacity analysis and system optimization for the forward link of multi‐beam satellite broadband systems exploiting adaptive coding and modulation

Abstract: This paper deals with the system capacity analysis and assessment of the potential advantages provided by the introduction of Adaptive Coding and Modulation (ACM) in the reverse link of multi-beam broadband satellite systems. ACM is intended to increase the system throughput for a given terminal EIRP power by optimizing the individual links physical layer to the current channel conditions. The physical layer adaptation will be driven by the inbound demodulator signal over noise plus interference ratio (SNIR) estimation. A general methodology for ACM physical layer optimization based on the system capacity maximization is also illustrated. A theoretical analysis of ACM systems capacity is performed for both time division multiple access (TDMA) and code division multiple access (CDMA) schemes. As the exact analytical capacity computation results to be very complex while Monte Carlo approach leads to very time consuming simulations, a simplified semi-analytic approach is devised. Numerical results showing the huge improvement in terms of capacity by the ACM adoption are obtained for both the semi-analytic and the Monte Carlo approaches in a realistic study case corresponding to a Ka-band multibeam satellite system. A good match between the two approaches is also demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.

An energy adaptive demodulation for high data rates with impulse radio

Abstract: The purpose of This work is to provide an operative way of achieving high data rates for impulse radio (IR) transmission based systems Because applications targeted for ultra wide band (UWB) are low-cost, we especially focus on simple transceiver design To that effect, we present an original demodulation scheme adapted to a multi-band on-off keying (OOK) modulation The receiver's novelty consists of considering only the benefit from approximative delay spread and energy level to relax channel estimation constraints The optimum demodulation turns out to be a non-trivial energetic threshold comparison whose precise theoretical computation admits an original analytical solution proving its feasibility The knowledge of the available energy as well as the noise level required to set the threshold is easily obtained by appropriate estimators Finally, in addition to simple hardware architectures, numerical results show the efficiency of these techniques

Demodulator for a multi-pair gigabit transceiver

Abstract: A feedforward equalizer for equalizing a sequence of signal samples received by a receiver from a remote transmitter. The feedforward equalizer has a gain and is included in the receiver which includes a timing recovery module for setting a sampling phase and a decoder. The feedforward equalizer comprises a non-adaptive filter and a gain stage. The non-adaptive filter receives the signal samples and produces a filtered signal. The gain stage adjusts the gain of the feedforward equalizer by adjusting the amplitude of the filtered signal. The amplitude of the filtered signal is adjusted so that it fits in the operational range of the decoder. The feedforward equalizer does not affect the sampling phase setting of the timing recovery module of the receiver.

Wide-band RF receiver using the "five-port" technology

Abstract: Many experiments have been proposed in order to demonstrate that the "five-port" system performs a homodyne demodulation . The large bandwith of a five-port circuit is its main advantage. However, this kind of system must be calibrated for each frequency in order to carry out the inphase and quadrature demodulation. The subject of this paper is to show a new calibration method. This technique uses the training sequence received at each received burst of data to calibrate the five-port system. A method to synchronize the receiver with the training sequence of each burst is presented. We also study the effect of adjacent channels and cochannel interferer on the calibration. Results on quaternary phase-shift keying demodulation are presented.

Autocorrelation demodulation technique for fiber Bragg grating sensor

Abstract: In this letter, we describe a very accurate and simple demodulation technique for fiber Bragg grating sensors. The technique is suitable for both single and twin Bragg gratings. A twin grating is composed of two identical gratings located at different positions in the same single-mode fiber. Our demodulation technique evaluates the wavelength position of the reflection spectrum with respect to the spectrum of an undisturbed sensor. To calculate the spectrum shift, it computes the autocorrelation product between the two reflection spectra. The demodulation method, which is very fast, has been tested experimentally with temperature sensors. It gives absolute measurements and provides high accuracy compared to a conventional temperature probe.

OFDM channel estimation and tracking for multiple transmit antennas

Abstract: Multiple Transmit Multiple Receive Orthogonal Frequency Division Multiplexing ('OFDM') comprising generating bit streams and corresponding sets of N frequency domain carrier amplitudes (see (I)), 0≤j ≤N -1) modulated as OFDM symbols subsequently to be transm itted from a transmitter, where k is the OFDM symbol number and j indicates the corresponding OFDM carrier number. Affix information is inserted at the transmitter Into guard intervals between consecutive time domain OFDM symbols and are used at the receiver to estimate the Channel Impulse Response (Hlm) of the transmission channels, the estimated Channel Impulse Response (see (II)) being used to demodulate the bit streams In the signals received at the receiver. The affix information is known to the receiver as well as to the transmitter, and is mathematically equivalent to a vector (cD) that is common to the time domain OFDM symbols multiplied by at least first weighting factors (ak) that are different for one time domain OFDM symbol (ak) than for another and second weighting factors (wi(k)) that enable one of the transmit antenna means (i) to be distinguished from another.

Performance of demodulation-based frequency measurement algorithms used in typical PMUs

Abstract: This paper presents a method for evaluating the performance of demodulation-based frequency measurement algorithms in the presence of additive interfering sinusoids. Determination of the performance of amplitude measurement schemes under such conditions is straightforward once the frequency responses of the filters involved in the process are known, since the error induced by a single interfering tone is easily computed using the cascade algorithm's frequency response magnitude. This paper presents a similar method for predicting the worst error of frequency measurement schemes with respect to sinusoidal interference. Once acquainted with the proposed error prediction formula, the only difficulty in designing effective frequency measurement algorithms is the appropriate selection of output filters to achieve the specified performance. The method has been used successfully in designing frequency measurement algorithms currently used in Hydro-Que/spl acute/bec's special protection schemes.

OFDM receiver, semiconductor integrated circuit and OFDM method for receiving a signal

Abstract: An OFDM receiver includes a converter configured to generate a transform signal by Fourier transform of a received signal. A first interpolator is configured to detect a pilot signal from the transform signal, and to provide time interpolation to the pilot signal. An interference detector is configured to provide arithmetic processing to the time interpolated pilot signal, and to detect interference by comparing a result of the arithmetic processing with a threshold. A second interpolator is configured to provide frequency interference interpolation with respect to the interference detected pilot signal, and to provide frequency interpolation to the pilot signal after the interference interpolation. A demodulator is configured to perform demodulation based on the transform signal and the frequency interpolated pilot signal.