5384results about "Amplitude demodulation" patented technology

A method and an apparatus measure blood oxygenation in a subject. A first signal source applies a first input signal during a first time interval. A second signal source applies a second input signal during a second time interval. A detector detects a first parametric signal responsive to the first input signal passing through a portion of the subject having blood therein. The detector also detects a second parametric signal responsive to the second input signal passing through the portion of the subject. The detector generates a detector output signal responsive to the first and second parametric signals. A signal processor receives the detector output signal and demodulates the detector output signal by applying a first demodulation signal to a signal responsive to the detector output signal to generate a first output signal responsive to the first parametric signal. The signal processor applies a second demodulation signal to the signal responsive to the detector output signal to generate a second output signal responsive to the second parametric signal. The first demodulation signal and the second demodulation signal both include at least a first component having a first frequency and a first amplitude and a second component having a second frequency and a second amplitude. The second frequency is a harmonic of the first frequency. The second amplitude is related to the first amplitude to minimize crosstalk from the first parametric signal to the second output signal and to minimize crosstalk from the second parametric signal to the first output signal.

Carrier Interferometry (CI) provides wideband transmission protocols with frequency-band selectivity to improve interference rejection, reduce multipath fading, and enable operation across non-continuous frequency bands. Direct-sequence protocols, such as DS-CDMA, are provided with CI to greatly improve performance and reduce transceiver complexity. CI introduces families of orthogonal polyphase codes that can be used for channel coding, spreading, and / or multiple access. Unlike conventional DS-CDMA, CI coding is not necessary for energy spreading because a set of CI carriers has an inherently wide aggregate bandwidth. Instead, CI codes are used for channelization, energy smoothing in the frequency domain, and interference suppression. CI-based ultra-wideband protocols are implemented via frequency-domain processing to reduce synchronization problems, transceiver complexity, and poor multipath performance of conventional ultra-wideband systems. CI allows wideband protocols to be implemented with space-frequency processing and other array-processing techniques to provide either or both diversity combining and sub-space processing. CI also enables spatial processing without antenna arrays. Even the bandwidth efficiency of multicarrier protocols is greatly enhanced with CI. CI-based wavelets avoid time and frequency resolution trade-offs associated with conventional wavelet processing. CI-based Fourier transforms eliminate all multiplications, which greatly simplifies multi-frequency processing. The quantum-wave principles of CI improve all types of baseband and radio processing.

Methods and apparatus are provided for communicating data in a multiple antenna communication system having N transmit antennas. According to one aspect of the invention, a header format includes a legacy preamble having at least one legacy long training field and an extended portion having at least N additional long training fields on each of the N transmit antennas. The N additional long training fields may be tone interleaved across the N transmit antennas and are used for MIMO channel estimation. The extended portion may include a short training field for power estimation. The short training field may be tone interleaved across the N transmit antennas and have an extended duration to support beam steering.

Transmitter and receiver units for use in an OFDM communications system and configurable to support multiple types of services. The transmitter unit includes one or more encoders, a symbol mapping element, and a modulator. Each encoder receives and codes a respective channel data stream to generate a corresponding coded data stream. The symbol mapping element receives and maps data from the coded data streams to generate modulation symbol vectors, with each modulation symbol vector including a set of data values used to modulate a set of tones to generate an OFDM symbol. The modulator modulates the modulation symbol vectors to provide a modulated signal suitable for transmission. The data from each coded data stream is mapped to a respective set of one or more “circuits”. Each circuit can be defined to include a number of tones from a number of OFDM symbols, a number of tones from a single OFDM symbol, all tones from one or more OFDM symbols, or some other combination of tones. The circuits can have equal size or different sizes. Different circuits can be used for full rate data (e.g., active speech) and low rate data (e.g., silence periods).

Exemplary received signal processing may be based on maintaining a model of received signal impairment correlations, wherein each term of the model is updated periodically or as needed based on measuring impairments for a received signal of interest. An exemplary model comprises an interference impairment term scaled by a first model fitting parameter, and a noise impairment term scaled by a second model fitting parameters. The model terms may be maintained based on current channel estimates and delay information and may be fitted to measured impairment by adapting the model fitting parameters based on the measured impairment. The modeled received signal impairment correlations may be used to compute RAKE combining weights for received signal processing, or to compute Signal-to-Interference (SIR) estimates. Combined or separate models may be used for multiple received signals. As such, the exemplary modeling is extended to soft handoff, multiple antennas, and other diversity situations.

In a nonvolatile memory system, data is read from a memory array and used to obtain likelihood values, which are then provided to a soft-input soft-output decoder. The soft-input soft-output decoder calculates output likelihood values from input likelihood values and from parity data that was previously added according to an encoding scheme.

A digital broadcast transmitting and receiving system and a signal processing method thereof that improves the receiving performance of the system. A digital broadcast transmitter can include a randomizer to receive and randomize a data stream into a specified position of which stuff bytes are inserted, a stuff-byte exchange unit to generate known data having a predefined pattern and insert the known data into the specified position of the data stream into which the stuff bytes are inserted, an encoder to encode the data stream output from the stuff-byte exchange unit for an error correction, and a modulator and RF converter to modulate the encoded data stream, RF-convert the modulated data stream and transmit the RF-converted data. The digital broadcast receiving performance can be improved even in an inferior multi-path channel by detecting the known data from the received transmission and using the known data for synchronization and equalization in a digital broadcast receiver.

A wireless communication device including a radio frequency (RF) circuit, a ZIF transceiver and a baseband processor. The ZIF transceiver includes an RF mixer circuit that converts the RF signal to a baseband input signal, a summing junction that subtracts a DC offset from the baseband input signal to provide an adjusted baseband input signal, and a baseband amplifier that receives the adjusted baseband input signal and that asserts an amplified input signal based on a gain adjust signal. The baseband processor includes gain control logic, DC control logic and a gain interface. The gain control logic receives the amplified input signal, estimates input signal power and asserts the gain adjust signal in an attempt to keep the input signal power at a target power level. The DC control logic estimates an amount of DC in the amplified input signal and provides the DC offset in an attempt to reduce DC in the amplified input signal. The gain interface converts gain levels between the gain control logic and the DC control logic. The RF signal may include in-phase (I) and quadrature (Q) portions, where the RF mixer circuit splits I and Q baseband input signals from the RF signal. Operation is substantially identical for both I and Q channels. The DC control logic operates to remove or otherwise eliminate DC from the received signal that is provided to decoders in the baseband processor.

The disclosed technology provides a less resource intensive way to decode a parity check code using a modified min-sum algorithm. For a particular parity check constraint that includes n variable nodes, an LDPC decoder can compute soft information for one of the variable nodes based on combinations of soft information from other variable nodes, wherein each combination includes soft information from at most a number d of other variable nodes. In one embodiment, soft information from one of the other variable nodes is used in a combination only if it corresponds to a non-most-likely value for the other variable node.

A transceiver employing a steerable phased-array antenna includes a modem architecture in which signals from each antenna element in the array are independently processed down to the individual baseband channel level, and digital beamforming is performed at baseband. The data rate reduction from IF to baseband permits parallel signal data from multiple antenna elements to be time multiplexed and serially processed at acceptable data rates at baseband with minimal modem hardware requirements. Both for transmit signal modulation and received signal demodulation, the computation of carrier tracking, automatic gain control (AGC) / power-control, and beamforming are shared by the same processing circuitry for all channels when performed at baseband. The resulting baseband circuitry is only incrementally larger than that required for carrier tracking and AGC alone, yet accomplishes independent beamforming for each antenna element on each user channel.

A communication system uses a bus to transmit information, by receiving signals and mapping them to a second set of signals representing codewords of a superposition signaling code, and transmitting the second set of signals. The superposition signaling code can comprise more than one layer. The pin-efficiency can be larger than 1. The system may encode bits into a codeword of a superposition signaling code that is defined by two basis vectors of predetermined size and then have two encoders for permutation modulation codes defined by the basis vectors. The bits of information are divided into a first part representing a predetermined number of bits and a second part representing a predetermined number of bits, with the parts provided to the respective encoding circuits and their outputs combined by a superposition.

Disclosed are an apparatus for Channel State Information-Reference Signal (CSI-RS) allocation and a method for CSI-RS transmission using the same in a wireless communication system. A CSI-RS for each antenna port is allocated to REs or subcarriers on a basis of a symbol or symbol axis in a subframe or Resource Block (RB), and is allocated in such a manner that a distance between neighboring CSI-RS allocation REs or subcarriers may be 3 REs or subcarriers. Accordingly, in the range of following CSI-RS transmission overhead, CSI-RSs are allocated to a time-frequency resource domain in such a manner so as to have perfect orthogonality or quasi-orthogonality according to cells or cell groups. Then, the CSI-RSs, which have been allocated to the time-frequency resource domain, are transmitted.

A receiver system that receives signals and has a demapper device that is responsive to an equalizer output and generates a demapper output including one or more bit metrics. The receiver system also generates equalizer output, and the demapper uses distance measure to calculate bit metrics. The receiver system uses demapper output to generate a processed output. The receiver system further includes a convolutional decoder which is responsive to the processed output, and subsequently generates a decoded bit sequence, as well as uses the processed output to generate one or more path metrics. The convolutional decoder uses bit metrics and path metrics to the decode processed output, to generate a decoded bit sequence. The receiver system uses the distance measure to reduce the size of the bit metrics and the size of the path metrics to improve the performance of said convolutional decoder.

A system and method for determining angular offset of an impulse radio transmitter using an impulse radio receiver coupled to two antennae. The antennae are separated by some known distance, and, in one embodiment, one antennae is coupled to the radio with cable delay. Impulse signals from the antennae are measured to determine the time difference of arrival of one such signal received by one antenna compared to that of the other antenna. Time differential is measured by autocorrelation of the entire impulse radio scan period, by detecting the leading edges of both incoming signals or various combinations of these methods. Using a tracking receiver, the pulses may be continuously tracked thus providing real time position information.

A signal compression method and apparatus for a base transceiver system (BTS) in a wireless communication network provides efficient transfer of compressed signal samples over serial data links in the system. For the uplink, an RF unit of the BTS compresses baseband signal samples resulting from analog to digital conversion of a received analog signal followed by digital downconversion. The compressed signal samples are transferred over the serial data link to the baseband processor then decompressed prior to normal signal processing. For the downlink, the baseband processor compresses baseband signal samples and transfers the compressed signal samples to the RF unit. The RF unit decompresses the compressed samples prior to digital upconversion and digital to analog conversion to form an analog signal for transmission over an antenna. Compression and decompression can be incorporated into operations of conventional base stations and distributed antenna systems, including OBSAI or CPRI compliant systems.

A bit synchronizer for a digital receiver system accounts for loss of bit synchronization due to transmission phenomena. The bit synchronizer includes a DC level estimator for converting a sampled digital signal having a bit rate and a sampling rate into a level-adjusted signal. A delay module generates a first timing signal, a second timing signal, and a third timing signal based on the level-adjusted signal. The timing signals correspond to early, on-time, and late sampling windows. The control module generates an output signal based on the timing signals such that the transmit and receive bit timing are synchronized. In one embodiment, the control module has an absolute value stage, an integration stage, and a signal selector. The signal selector is able to select between the timing signals, adjust the symbol rate to re-center the on-time gate, and memory swap to maintain correct averaging operations.

A radio portion controlling means of a receiver of a mobile station has an average time setting means. A controlling means supervises an average received power. When the average received power approaches a power at which the gain of a gain changing means should be changed, the controlling means causes a received power calculating means to increase the time period for the calculation of the average received power so as to decrease the error of the average received power at which the gain of the gain selecting means is changed.

A novel and useful whitening matched filter (WMF) for use in a communications receiver. The WMF is constructed by cascading a matched filter and a noise-whitening filter. The response of the matched filter is derived from the time reversed complex conjugate of the channel impulse response. The whitening filter is derived by extracting the minimum phase portion of the mixed phase channel impulse response using homomorphic deconvolution. The whitening filter is implemented using either an FIR or IIR filter adapted to process the data received before and after the training sequence using a minimum phase system in a direction in time opposite to that of the direction of corresponding data sample processing performed by the equalizer.

A phase-shift based pre-coding scheme used in a transmitting side and a receiving side that has less complexity than those of a space-time coding scheme, that can support various spatial multiplexing rates while maintaining the advantages of the phase-shift diversity scheme, that has less channel sensitivity than that of the pre-coding scheme, and that only requires a low capacity codebook is provided.

A digital receiver, that may be used to receive VSB / QAM digital television signals, includes an adaptive fine carrier recovery circuit that compensates for deviations in the carrier frequency or phase. The carrier recovery circuit de-rotates a signal including phase errors. Estimations of phase errors are filtered using a filter whose gain and bandwidth are adjusted adaptively. This allows the carrier recovery circuit to track phase / frequency offset without introducing significant jitter. In one embodiment, the receiver includes a DFE, and the adaptive carrier recovery circuit mitigates instability that might be associated with the DFE.

A bandwidth efficient advanced modulation waveform modem using concatenated iterative turbo coding and continuous phase modulation is disclosed. A demodulator in the modem has a turbo decoder and a decision feedback carrier and time tracking algorithm to track a carrier and adjust timing. The decision feedback carrier and time tracking algorithm may use an APP decoder as a decision device to provide symbol decisions at a high error rate and low latency for a coded input data stream. A symbol phase estimator produces a symbol phase error estimate from the symbol decisions. An erasure decision function decides which symbol decisions are correct and which symbol decisions are erasures. A carrier tracking function receives the symbol phase error estimates when the symbol decisions are correct and receives erasure inputs when the symbol decisions are erasures to maintain carrier tracking.

The invention provides a method of operating a communication system. A channel matrix of a gain and phase between each transmit antenna and each receive antenna of the communication system is provided. At least one receive weight vector is computed as a function of the channel matrix and at least one of transmit weight vectors. An updated transmit weight vector is computed as a function of the transmit weight vector, the receive weight vector, the channel matrix.

A method for calibrating an impulse radio distance measuring system comprising an impulse radio transceiver by conducting a pulse through a transmit receive switch to an antenna, receiving return energy which has been discharged across the transmit receive switch, determining a time of arrival of the return energy. The return energy is comprised of two distinct pulses, one of which represents discharge of the transmit switch as the original pulse travels to the antenna, the second represents energy reflected from the antenna and again discharged across the transmit receive switch while the switch is in the transmit position. The timing of the un-reflected energy is determined then the timing of the reflected energy relative to the un-reflected energy is determined through auto-correlation of the time domain scan of the received composite waveforms.

A composite data detector having first and second data detectors. The second detector of the invention starts in a known state and only runs as long as is necessary before being switched off and handing control back over to the smaller detector. Therefore, the composite data detector of the invention consumes less power than the known composite data detector and estimates bits with higher accuracy.

A system and method are provided that can detect any part of a multipath impulse radio signal. More specifically, the method compares a template pulse train and the multipath impulse radio signal to obtain a comparison result. The system performs a threshold check on the comparison result. If the comparison result passes the threshold check, the system locks onto any part of the multipath impulse radio signal including a direct path part and at least one multipath reflection part. The system may also perform a quick check, a sychronization check, and / or a command check of the multipath impulse radio signal.

A resolution enhancement algorithm is trained on sample images to obtain a polynomial model mapping of low resolution image data to high resolution image data. The polynomial model mapping is applied to other low resolution images to obtain corresponding higher resolution images. The mapping provides resolution enhancement which is superior to that of conventional image data interpolation techniques.

A method and device in which only a single symbol is required for synchronization, and which permits the detection of appreciable deviations from the normal receiver oscillator frequency or of a deviation of the transmitter frequency from the given frequency pattern, and the correction of the oscillator frequency. The invention further includes an evaluation method for the signal which contains a multiplicity of modulated carriers. In a decoder, additional sequences are evaluated after demodulation and differential reconversion by means of a correlation.