Showing papers on "Demodulation published in 2010"

Beyond Nyquist: Efficient Sampling of Sparse Bandlimited Signals

Abstract: Wideband analog signals push contemporary analog-to-digital conversion (ADC) systems to their performance limits. In many applications, however, sampling at the Nyquist rate is inefficient because the signals of interest contain only a small number of significant frequencies relative to the band limit, although the locations of the frequencies may not be known a priori. For this type of sparse signal, other sampling strategies are possible. This paper describes a new type of data acquisition system, called a random demodulator, that is constructed from robust, readily available components. Let K denote the total number of frequencies in the signal, and let W denote its band limit in hertz. Simulations suggest that the random demodulator requires just O(K log(W/K)) samples per second to stably reconstruct the signal. This sampling rate is exponentially lower than the Nyquist rate of W hertz. In contrast to Nyquist sampling, one must use nonlinear methods, such as convex programming, to recover the signal from the samples taken by the random demodulator. This paper provides a detailed theoretical analysis of the system's performance that supports the empirical observations.

Instrument-Based Noncontact Doppler Radar Vital Sign Detection System Using Heterodyne Digital Quadrature Demodulation Architecture

Abstract: In this paper, we present a fast solution to build a Doppler radar system for noncontact vital sign detection (VSD) using instruments that are generally equipped in radio-frequency and communication laboratories. This paper demonstrates the feasibility of conducting research on VSD in ordinary radio-frequency laboratories. The system is designed with a heterodyne digital quadrature demodulation architecture that helps mitigate quadrature channel imbalance and eliminate the complicated dc offset calibration required for arctangent demodulation. Moreover, its tunable carrier frequency helps select different optimal frequencies for different human objects. Two sets of extensive experiments have been carried out in the laboratory environment with a self-designed 2.4-GHz patch antenna array and a 1-18-GHz broadband antenna. The test results are satisfactory: for a 0-dBm transmit power, the detection range can be extended to 2.5 m with accuracy higher than 80%. The system is also capable of detecting vital signs in the presence of different obstructions between the subject and the antenna.

An Improved Feed-Forward Carrier Recovery Algorithm for Coherent Receivers With $M$ -QAM Modulation Format

Abstract: An improved feed-forward carrier phase recovery method is proposed for coherent receivers using M-ary quadrature amplitude modulation-based modulation formats. It is shown that by introducing multiple cascaded feed-forward carrier recovery stages, the required compute power can be significantly reduced compared to the prior art using the single-stage-based blind phase search method.

Equalizer Design and Complexity for Digital Coherent Receivers

Abstract: Digital signal processing has completely changed the way optical communication systems work during recent years. In combination with coherent demodulation, it enables compensation of optical distortions that seemed impossible only a few years ago. However, at high bit rates, this comes at the price of complex processing circuits and high power consumption. In order to translate theoretic concepts into economically viable products, careful design of the digital signal processing algorithms is needed. In this paper, we give an overview of digital equalization algorithms for coherent receivers and derive expressions for their complexity. We compare single-carrier and multicarrier approaches, and investigate blind equalizer adaptation as well as training-symbol-based algorithms. We examine tradeoffs between parameters like sampling rate and tracking speed that are important for algorithm design and practical implementation.

Method and apparatus for transmitting reference signal in wireless communication system

Abstract: A method and apparatus of transmitting a reference signal in a wireless communication system is provided. Demodulation Reference Signals (DMRSs) for a plurality of respective antennas is generated. The DMRSs are mapped to a resource region, and transmitted through the respective corresponding antennas. The DMRSs are multiplexed using at least one of frequency division multiplexing (FDM), code division multiplexing (CDM), and time division multiplexing (TDM) methods and mapped in the resource region. Also, a position of an orthogonal frequency division multiplexing (OFDM) symbol to which the DMRSs are mapped in the resource region is an OFDM symbol to which a physical downlink control channel (PDCCH) and a legacy cell-specific reference signal (CRS) are not mapped.

Digital and FM demodulation of a doubly-clamped single wall carbon nanotube oscillator: towards a nanotube cell phone

Abstract: Electromechanical resonators are a key element in radio-frequency telecommunications devices and thus new resonator concepts from nanotechnology can readily find important industrial opportunities. In this paper, we report the successful experimental realization of AM, FM and digital demodulation with suspended single wall carbon nanotube resonators in the field effect transistor configuration. The crucial role played by the mechanical resonance in demodulation is clearly demonstrated. The FM technique is shown to lead to the suppression of unwanted background signals and the reduction of noise for a better detection of the mechanical motion of nanotubes. The digital data transfer rate of standard cell phone technology is within the reach of our devices.

Digital and FM Demodulation of a Doubly Clamped Single‐Walled Carbon‐Nanotube Oscillator: Towards a Nanotube Cell Phone

Abstract: Electromechanical resonators are a key element in radio-frequency telecommunication devices and thus new resonator concepts from nanotechnology can readily find important industrial opportunities. Here, the successful experimental realization of AM, FM, and digital demodulation with suspended single-walled carbon-nanotube resonators in a field-effect transistor configuration is reported. The crucial role played by the electromechanical resonance in demodulation is clearly demonstrated. The FM technique is shown to lead to the suppression of unwanted background signals and the reduction of noise for a better detection of the mechanical motion of nanotubes. The digital data-transfer rate of standard cell-phone technology is within the reach of these devices.

A millimeter-wave intra-connect solution

Abstract: A novel millimeter-wave Intra-Connect solution for short range, high speed, internal I/O connections in low-power logic 40 nm CMOS process is demonstrated. The system consists of a transmitter and a receiver that uses binary amplitude shift keying (ASK) modulation for a compact and power efficient design. The receiver realizes coherent demodulation using injection locking without a PLL or an external reference clock utilizing a path to inject the received signal into the VCO. The demonstrator achieves 11 Gb/s ASK data transmission over 14 mm using bond-wire antennas with a bit error rate (BER) of less than 10-11. The active footprint of the transmitter is 0.06 mm2 and the power consumption is 29 mW with an energy usage of 6.4 pj/bit per channel. The receiver occupies the active footprint of 0.07 mm2 and consumes 41 mW. The work shows the feasibility of the millimeter-wave Intra-Connect for high speed internal I/O connections.

Software-Defined Radio Equipped With Rapid Modulation Recognition

Abstract: Automatic modulation recognition (AMR)-based software-defined radio (SDR) is a research challenge in developing third-generation (3G) and fourth-generation (4G) wireless communications with adaptive modulation capability. However, the existing AMR technology does not satisfy the seamless demodulation requirement of the SDR. A novel design of the AMR method with reduced computational complexity and fast processing speed is needed. This paper describes a discrete likelihood-ratio test (DLRT)-based rapid-estimation approach to identifying the modulation schemes blindly for uninterrupted data demodulation in real time. The statistical performance of the fast AMR associated with its implementation using the SDR is presented.

A Phase-Modulation I/Q-Demodulation Microwave-to-Digital Photonic Link

Abstract: We present theory and experiments for a microwave-to-digital photonic link capitalizing on the linearity of optical phase modulation and coherent optical I/Q demodulation to achieve unprecedented gain and dynamic range performance. We demonstrate, with an optical amplifier noise limited system, direct demodulation spur-free dynamic range (SFDR), gain, and noise figure of 126.8 dB-Hz2/3 (86.8 dB in 1 MHz noise bandwidth), 8 dB, and 18.6 dB, respectively for inputs up to 1 GHz. Additionally we demonstrate complimentary all-photonic downconversion allowing the extension of input operating bandwidth to a modulator limited 40 GHz. Demonstrated microwave to intermediate frequency conversion loss ranges from <; 4 dB @ 4 GHz to <; 13 dB @ 40 GHz. Linear all-photonic downconversion and demodulation is demonstrated at 3 and 10 GHz with optical amplifier noise limited SFDR better than 107 dB-Hz2/3 (67 dB in 1 MHz noise bandwidth). System design issues are discussed including critical parametric sensitivities and optical-electrical-digital sub-system dynamic range matching and technology capability for downconverting microwave-to-digital SFDR performance in excess of 125 dB-Hz2/3 (85 dB in 1 MHz) with current technology.

Novel Power Efficient Optical OFDM Based on Hartley Transform for Intensity-Modulated Direct-Detection Systems

Abstract: We present a novel optical orthogonal frequency division multiplexing (O-OFDM) scheme, suitable for intensity-modulated direct-detection systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform algorithm. Due to the properties of the discrete Hartley transform (DHT), the conventional transmission scheme can be streamlined. We demonstrate that asymmetrically clipping (AC) technique can also be applied to DHT-based OFDM; the signal can be transmitted without the need of a DC bias, resulting in a power-efficient system, not affected by clipping noise. Hermitian symmetry is not required for the input signal. Therefore, this technique supports the double of input symbols compared to both AC and DC-biased O-OFDM, based on standard Fourier processing. The analysis in an additive white Gaussian noise channel shows that the same performance can be achieved by replacing 4, 16, and 64 QAM (quadrature-amplitude modulation) AC optical-OFDM with a simpler system based on DHT, using binary phase-shift keying (BPSK), 4 and 8 PAM (pulse-amplitude modulation), respectively.

A Novel Vital-Sign Sensor Based on a Self-Injection-Locked Oscillator

Abstract: A novel vital-sign sensor with a self-injection-locked oscillator and a frequency demodulator to reduce system complexity and improve sensitivity is proposed. The theory provides a delta-sigma model to account for the excellent signal-to-noise spectral density ratio in a parametric study of the sensitivity performance. Then, the experiments verify the sensing principle and the predicted performance. Accordingly, a prototype sensor with high sensitivity is realized for noncontact cardiopulmonary monitoring, achieving a long sensing distance without the need for a low-noise amplifier. The sensing distance can grow four times longer by doubling the operating frequency. Furthermore, the sensor using a swept frequency can eliminate the null detection points and the external radio interference. As an experimental result, the sensor, which is placed 4 m away from the subject, can reliably detect the heartbeat signal an the operating frequency of 3.6 GHz and an output power level of 0 dBm.

Low power wake-up receiver for wireless sensor nodes

Abstract: Duty cycling is a common method to reduce the energy consumption in wireless sensor nodes. Since all the nodes turn on their radio in a time slot, but only few of them actually exchange messages, energy is wasted. This can be avoided by using a separate wake-up radio. We present a new approach for a wake-up receiver that consumes 2.78 µA of current and integrates a 16 bit address coding for a selective wake-up. We use a low frequency wake-up signal that is modulated on a high frequency carrier in the main radio of the transmitting node. In the receiving node a passive demodulation circuit regains the low frequency signal and feds it to a low power low frequency wakeup IC. Four sample boards were manufactured and measured that operate at 868 MHz in the European ISM band. By using coils with high Q factors in the demodulation circuit we reached a sensitivity of −52 dBm which resulted in a wake-up distance of up to 40 meters at an output power level of +10 dBm in the transmitter. Compared to van der Doorn et. al, “A prototype low-cost wakeup radio for the 868 MHz band” Int. J. Sensor Networks, Vol.5, No.1, 2009, we achieved a 20 times farther wakeup range and a 100 times lower current consumption.

QAM backscatter for passive UHF RFID tags

Abstract: Traditional passive UHF RFID tags employ either ASK or PSK backscatter modulation to communicate data from memory or sensors on the tag to a remotely-located reader These simple modulation schemes transfer data at a rate of one bit per symbol period, which for an integrated CMOS tag IC requires an on-chip oscillator with a frequency at least equal to the bit rate Motivated by the fact that most modern UHF RFID readers already employ I/Q demodulation of the backscattered signal to account for backscatter phase rotation as the tag moves with respect to the reader, we propose a QAM backscatter method using no on-chip inductors that is compatible with a single-chip CMOS tag implementationWith QAM backscatter, tags transmit more than one data bit per symbol period, permitting tag designers to employ a lower power on-chip oscillator operating at a frequency equal to the (lower) symbol rate while maintaining the same data throughput as ASK or PSK, or alternatively to send data at a higher rate for a given on-chip oscillator frequency We present the fundamental design equations required for arbitrary QAM backscatter modulators and present simulated bit error rate (BER) and error vector magnitude (EVM) curves for the operation of an inductor-free 4-QAM and 8-QAM modulator centered at 915MHz and evaluated over the 860MHz–950MHz worldwide UHF band

Cyclostationarity-Based Modulation Classification of Linear Digital Modulations in Flat Fading Channels

Abstract: Modulation classification is an intermediate step between signal detection and demodulation, and plays a key role in various civilian and military applications. In this correspondence, higher-order cyclic cumulants (CCs) are explored to discriminate linear digital modulations in flat fading channels. Single- and multi-antenna CC-based classifiers are investigated. These benefit from the robustness of the CC-based features to unknown phase and timing offset. Furthermore, the latter provides significant performance improvement due to spatial diversity used to combat the fading effect. Classifier performances are investigated under a variety of channel conditions. In addition, analytical closed-form expressions for the cyclic cumulant polyspectra of linearly digitally modulated signals affected by fading, carrier frequency and timing offsets, and additive Gaussian noise are derived, along with a condition for the oversampling factor to avoid aliasing in the cycle and spectral frequency domains.

An Ultra-Low-Power interference-robust IR-UWB transceiver chipset using self-synchronizing OOK modulation

Abstract: Impulse Radio-UWB (IR-UWB) is actively being researched as a low cost wireless technology for Ultra Low Power (ULP), low data-rate, short-range wireless links in tagging [1], sensing and medical applications. In current solutions efficient timing acquisition as well as Narrow-Band Interference (NBI) rejection requires complex or large analog and digital circuits [2–4]. In this work, we introduce an IR-UWB architecture with very high NBI rejection and present a low complexity and low power timing synchronization and demodulation technique while achieving excellent link performance.

A/D Conversion Using Asynchronous Delta-Sigma Modulation and Time-to-Digital Conversion

Abstract: An analog-to-digital conversion (ADC) scheme based on asynchronous ΔΣ modulation and time-to-digital conversion is presented. An asynchronous ΔΣ modulator translates the analog input to an asynchronous duty-cycle modulated signal. Next, the edge locations are digitally measured using a time-to-digital converter (TDC). This information is then digitally processed into a conventional digital signal. The performance of this novel ADC scheme is theoretically analyzed and verified with simulations. With the proposed digital demodulation algorithm, 11-bit resolution can be obtained with an overcycling ratio (OCR) of only four, which is suitable for high bandwidth applications such as very high bit-rate digital subscriber line (VDSL). When a higher OCR can be tolerated, a gated ring-oscillator (GRO) TDC with an inherent first-order noise shaping property is suggested in combination with a digital continuous-time moving-average (CTMA) filter. This allows for resolutions in excess of 13 bits, which is suitable for ADSL2+. The proposed technique shifts the complexity toward the digital domain, leading to more compact ADC and reduced power consumption, and is, therefore, particularly suited for ADC in ultralow-voltage nanometer technologies that are used for high-speed data communication applications.

Apparatus and method for transmitting channel state information in a mobile communication system

Abstract: A apparatus and method for transmitting channel state information is disclosed If an LTE-A system transmits a reference signal per subframe to support eight transmitting antennas, a problem occurs in that overhead is great In order to solve this problem, a reference signal for channel measurement is transmitted per subband at different periods, or a user equipment scheduled for channel measurement uses a demodulation reference signal The user equipment can notify a base station of channel measurement result using the demodulation reference signal in accordance with implicit or explicit signaling from the base station

Discrete-Time Mixing Receiver Architecture for RF-Sampling Software-Defined Radio

Abstract: A discrete-time (DT) mixing architecture for RF-sampling receivers is presented. This architecture makes RF sampling more suitable for software-defined radio (SDR) as it achieves wideband quadrature demodulation and wideband harmonic rejection. The paper consists of two parts. In the first part, different downconversion techniques are classified and compared, leading to the definition of a DT mixing concept. The suitability of CT-mixing and RF-sampling receivers to SDR is also discussed. In the second part, we elaborate the DT-mixing architecture, which can be realized by de-multiplexing. Simulation shows a wideband 90° phase shift between I and Q outputs without systematic channel bandwidth limitation. Oversampling and harmonic rejection relaxes RF pre-filtering and reduces noise and interference folding. A proof-of-concept DT-mixing downconverter has been built in 65 nm CMOS, for 0.2 to 0.9 GHz RF band employing 8-times oversampling. It can reject 2nd to 6th harmonics by 40 dB typically and without systematic channel bandwidth limitation. Without an LNA, it achieves a gain of -0.5 to 2.5 dB, a DSB noise figure of 18 to 20 dB, an IIP3 = +10 dBm, and an IIP2 = +53 dBm, while consuming less than 19 mW including multiphase clock generation.

Position sensorless control of PMSM by synchronous injection and demodulation of alternating carrier voltage

Abstract: Synchronous machines with surface mounted permanent magnets (SMPMSMs) are very popular in industry due to their high efficiency and simple design and are therefore of special interest for position sensorless control. These types of machines typically have small inherent saliencies resulting in a low signal to noise ratio when measuring the rotor position using injected high frequency test signals. It is therefore necessary to avoid any interference between the current controller and the injected signal to achieve the highest possible performance under sensorless control. This paper proposes a novel method for integrating an alternating carrier injection scheme into a current control loop without requiring the commonly used band-pass filter. It uses a strictly synchronous injection and demodulation approach. This allows the high frequency components of the stator current to become completely invisible to the current controller and additionally to eliminate the dead time in the current control loop. Furthermore the demodulated alternating carrier will be unaffected by the fundamental component even during transient conditions. Moreover the proposed decoupling method does not require any motor parameter adjustment.

Distributed consensus-based demodulation: algorithms and error analysis

Abstract: This paper deals with distributed demodulation of space-time transmissions of a common message from a multi-antenna access point (AP) to a wireless sensor network. Based on local message exchanges with single-hop neighboring sensors, two algorithms are developed for distributed demodulation. In the first algorithm, sensors consent on the estimated symbols. By relaxing the finite-alphabet constraints on the symbols, the demodulation task is formulated as a distributed convex optimization problem that is solved iteratively using the method of multipliers. Distributed versions of the centralized zero-forcing (ZF) and minimum mean-square error (MMSE) demodulators follow as special cases. In the second algorithm, sensors iteratively reach consensus on the average (cross-) covariances of locally available per-sensor data vectors with the corresponding AP-to-sensor channel matrices, which constitute sufficient statistics for maximum likelihood demodulation. Distributed versions of the sphere decoding algorithm and the ZF/MMSE demodulators are also developed. These algorithms offer distinct merits in terms of error performance and resilience to non-ideal inter-sensor links. In both cases, the per-iteration error performance is analyzed, and the approximate number of iterations needed to attain a prescribed error rate are quantified. Simulated tests verify the analytical claims. Interestingly, only a few consensus iterations (roughly as many as the number of sensors), suffice for the distributed demodulators to approach the performance of their centralized counterparts.

Methods and apparatus for synchronization in multiple-channel communication systems

Abstract: Methods and apparatus for processing multichannel signals in a multichannel receiver are described. In one implementation, a plurality of demodulator circuits may provide a plurality of outputs to a processing module, with the processing module then simultaneously estimating noise characteristics based on the plurality of outputs and generating a common noise estimate based on the plurality of outputs. This common noise estimate may then be provided back the demodulators and used to adjust the demodulation of signals in the plurality of demodulators to improve phase noise performance.

Audio data receiving apparatus, audio data receiving method, and audio data transmission and receiving system

Abstract: An audio data receiving apparatus includes a receiving unit configured to receive audio data sampled in accordance with a first clock signal; a synchronization unit configured to generate a second clock signal that is synchronized with the first clock signal by extracting clock components contained in the audio data; a demodulator configured to demodulate the audio data in accordance with the second clock signal; an oversampling unit configured to oversample the audio data demodulated by the demodulator by using a frequency higher than a frequency of the second clock signal; a clock generator configured to generate a third clock signal having a frequency nearly equal to the first clock signal; and a data output unit configured to output the audio data oversampled by the oversampling unit in accordance with the third clock signal generated by the clock generator.

Sonic communication system and method

Abstract: A method, apparatus and computer program product is provided for wirelessly transmitting and receiving data through sonic communication. A method and system is provided for devices to exchange data over the air using a sonic carrier signal. The transmit device has at least one sonic transducer that transmits a sonic carrier signal through the air in accordance with aspects of the present invention. A digital representation of the data is modulated consistent with a modulation protocol using one or more sonic transmission frequencies in accordance with present invention. The sonic transducer transmits the one or more sonic carrier signals carrying the modulated data over the air. Each sonic carrier signal has sufficient gain to carry the signal to a receiver device where the data from the one or more sonic carrier signals is demodulated. Aspects of the present invention receive modulated data through the air using at least one sonic transducer of a receive device. Prior to demodulation, the receive device may be configured to perform the demodulation of the data at one or more sonic transmission frequencies. Sonic carrier signals at these sonic transmission frequencies are demodulated in accordance with a sonic modulation protocol providing a binary representation of the data. Ambient noise captured by the receiver device is processed along with the data transmitted over the sonic carrier signals.

Method and apparatus for providing downlink reference signal transmission power information in a wireless communication system that supports multiple antennas

Abstract: The present invention relates to a wireless communication system, and more particularly, discloses a method and an apparatus for providing downlink reference signal transmission power information in a wireless communication system that supports multiple antennas. A method for providing demodulation reference signal transmission power information according to one embodiment of the present invention comprises: a step of mapping a main synchronous signal onto a predetermined OFDM symbol of a downlink pilot time slot (DwPTS) subframe; a step of mapping, in a code division multiplexing manner, a demodulation reference signal over two or more OFDM symbols containing said predetermined OFDM symbol in the DwPTS subframe; a step of transmitting the DwPTS subframe to which the main synchronous signal and the demodulation reference signal are mapped; and a step of transmitting information on the transmission power for transmitting the demodulation reference signal mapped onto said predetermined OFDM symbol.

Microwave Human Vocal Vibration Signal Detection Based on Doppler Radar Technology

Abstract: A speech radar system is presented for extracting speech information from the vocal vibration signal of a human subject. Due to the tiny glottis motion of several millimeters, a coherent homodyne demodulator with high sensitivity is developed to detect reflected radio signal, phase modulated by the vibrating vocal cords. The signal detection quality and system circuit design are described. Measurements of vowels and words, both with the speech radar system and the conventional acoustic microphone system, were conducted and compared. The essential speech information can be reliably obtained from the proposed speech radar, making it more appealing for speech applications in high background acoustic noise environment.

Kalman filter carrier and polarization-state tracking.

Abstract: Application of Kalman filtering with a novel nearest-symbol constraint enables dynamic tracking of carrier phase and polarization state. Thereby, the proposed Kalman filter accomplishes demodulation of optical polarization-multiplexed complex modulation format signals.

Multi-pair gigabit Ethernet transceiver having adaptive disabling of circuit elements

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.