10204results about "Amplitude-modulated carrier systems" 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.

A system, method and program are disclosed for achieving rapid bit synchronization in low power medical device systems. Messages are transmitted via telemetry between a medical device and a communication device. The synchronization scheme uses a portion of a unique preamble bit pattern to identify the communication device allowing for economical communications with a minimum expenditure of energy. A special set of preamble bit patterns are utilized for their unique synchronization properties making them particularly suited for rapid bit synchronization. These unique preamble bit patterns further provide simplification to the preamble error detection logic.

A waveform adaptive transmitter that conditions and/or modulates the phase, frequency, bandwidth, amplitude and/or attenuation of ultra-wideband (UWB) pulses. The transmitter confines or band-limits UWB signals within spectral limits for use in communication, positioning, and/or radar applications. One embodiment comprises a low-level UWB source (e.g., an impulse generator or time-gated oscillator (fixed or voltage-controlled)), a waveform adapter (e.g., digital or analog filter, pulse shaper, and/or voltage variable attenuator), a power amplifier, and an antenna to radiate a band-limited and/or modulated UWB or wideband signals. In a special case where the oscillator has zero frequency and outputs a DC bias, a low-level impulse generator impulse-excites a bandpass filter to produce an UWB signal having an adjustable center frequency and desired bandwidth based on a characteristic of the filter. In another embodiment, a low-level impulse signal is approximated by a time-gated continuous-wave oscillator to produce an extremely wide bandwidth pulse with deterministic center frequency and bandwidth characteristics. The UWB signal may be modulated to carry multi-megabit per second digital data, or may be used in object detection or for ranging applications. Activation of the power amplifier may be time-gated in cadence with the UWB source thereby to reduce inter-pulse power consumption. The UWB transmitter is capable of extremely high pulse repetition frequencies (PRFs) and data rates in the hundreds of megabits per second or more, frequency agility on a pulse-to-pulse basis allowing frequency hopping if desired, and extensibility from below HF to millimeter wave frequencies.

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.

Closed loop wireless communication of signals using an adaptive transmit antenna array (3), in which a plurality of copies of signals to be transmitted by the transmit antenna array (3) are produced with delays and weights (w_n^j) that are functions of the multi-path transmission channel characteristics (H) from the transmit antenna array (3) to a receive antenna array (4) of a receiver (2) and are combined before transmission by the transmit antenna array. The delays and weights (w_n^j) of the transmit copies for each transmit antenna element are functions of the respective multi-path transmission channel characteristics $\left(h_{n,m=1}^{l=1},\dots ,h_{n,m=M}^{l=L}\right)$

from that transmit antenna element to the receive antenna array (4) ssuch that the multi-path signal components propagated to each receiver element are received with distinguishable delays according to the propagation path. The receiver (2) combines the received signal components from each receive antenna element with delays and weights (u) that are respective functions of the multi-path transmission channels.

Preferably, the receiver comprises a multi-finger RAKE receiver (6) that copies the received signals from the receive antenna array with delays and weights (u) that are respective functions of the multi-path transmission channels and combines the copied received signals.

The present invention provides an FM Orthogonal Frequency Division Multiplexing (OFDM) modulation process that enable high-speed data communications over any transmission media and networks. The process is implemented with a modem device modulator and demodulator that provides communication with several other modem devices along any communication media that uses an FM OFDM modulation technique, a physical transmission medium such as power lines, or wireless (air), or cable, or twisted pairs communication media.

Embodiments are directed to transmitting L1 pre-signaling information with predetermined modulation and code rate such that L1 pre-signaling information can be received without preliminary knowledge on the network. L1 pre-signaling information makes it possible to receive the L1 signaling information, data link layer information, and notification data that may have configurable code rates and modulation. Therefore, L1 pre-signaling information can be thought of as signaling metadata (i.e., information about other signaling information). L1 signaling is divided into pre-signaling and signaling parts. The pre-signaling part includes parameters used for receiving the L1 signaling information. L1 pre-signaling signaling enables the receiver to receive the signaling itself (L1 signaling and data link layer information) by informing the receiver about the type of modulation, coding, and the like, used to transmit the L1 signaling, data link layer, and notification information.

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.

Provided is a transmission circuit which allows smooth switching of the operation mode when switching the operation mode of the transmission circuit. A power amplifier 14 includes: a first input terminal to which a direct-current voltage or a voltage in accordance with an amplitude signal M is supplied; a second input terminal to which an output signal from a first variable gain amplifier 171 or an output signal from a second variable gain amplifier 172 is inputted; and a third input terminal to which an output signal from a first bias circuit 15 or an output signal from a second bias circuit 16 is inputted. A control section 11 switches the operation mode of the transmission circuit so that at least one of the first input terminal, the second input terminal, and the third input terminal of the power amplifier is prevented from being in a no input state.

Methods, systems, and apparatuses for down-converting an electromagnetic (EM) signal by aliasing the EM signal are described herein. Briefly stated, such methods, systems, and apparatuses operate by receiving an EM signal and an aliasing signal having an aliasing rate. The EM signal is aliased according to the aliasing signal to down-convert the EM signal. The term aliasing, as used herein, refers to both down-converting an EM signal by under-sampling the EM signal at an aliasing rate, and down-converting an EM signal by transferring energy from the EM signal at the aliasing rate. In an embodiment, the EM signal is down-converted to an intermediate frequency (IF) signal. In another embodiment, the EM signal is down-converted to a demodulated baseband information signal. In another embodiment, the EM signal is a frequency modulated (FM) signal, which is down-converted to a non-FM signal, such as a phase modulated (PM) signal or an amplitude modulated (AM) signal.

The present invention relates to a communication system and communication method which enable various types of near field communication, and a data processing apparatus. NFC communication apparatuses 1 to 3 have two features in that each can perform communication in two communication modes and that each can perform data transmission at a plurality of transfer rates. The two communication modes consist of a passive mode and an active mode. In the passive mode, between the NFC communication apparatuses 1 and 2, for example, the NFC communication apparatus 1 transmits data to the NFC communication apparatus 2 by modulating electromagnetic waves generated by itself, while the NFC communication apparatus 2 transmits data to the NFC communication apparatus 1 by performing load modulation on the electromagnetic waves generated by the NFC communication apparatus 1. Alternatively, in the active mode, either of the NFC communication apparatuses 1 and 2 transmits data by modulating electromagnetic waves generated by itself. The present invention can be applied to, for example, an IC card system, etc.

Communication is performed for a first communication device having a set of antenna elements. A quality-indication signal is received from a second communication device (e.g., a basestation). A complex weighting is calculated based on the quality-indication signal. A pre-transmission signal is modified based on the complex transmit diversity weighting to produce a set of modified-pre-transmission signals, wherein the modifications are symmetric by making approximately half the magnitude of the transmit diversity modification to one signal in a first direction, and approximately half the magnitude of the transmit diversity modification to the other signal in a second direction, opposite the first direction. Each modified pre-transmission signal from the set of modified-pre-transmission signals is uniquely associated with an antenna element from the set of antenna elements. The set of modified-pre-transmission signals is sent from the set of antenna elements to produce a transmitted signal.

An enhanced 8-VSB reception system and E8-VSB data demultiplexing method, by which an E8-VSB signal can be stably received as well as a previous ATSC 8VSB signal, is disclosed. Herein, the enhanced data are coded at ½ code rate and ¼ code rate in the new E8-VSB transmission system compatible with the conventional ATSC 8VSB system, respectively. The ½ and ¼ enhanced data are multiplexed by 164-byte packet unit according to the previously determined multiplexing format and further pre-processed to output as the format of the MPEG transport packet. And, the pre-processed enhanced data and the main data are multiplexed again by 188-byte packet unit according to the previously determined multiplexing format. The E8-VSB map information, which was inserted in the field sync section in the E8-VSB transmission system to be transmitted, is extracted to generate the information indicating the attributes of the respective E8-VSB data. The normal data, ½ enhanced data, and ½ enhanced data are separated from each other to be decoded in the channel decoder.

Systems, methods, apparatus are provided for providing to a receiver a time diverse digital signal corresponding to a service including receiving a digital signal containing a service content and receiving a digital signal containing a non-deterministic content. The service content is inserted into a first predetermined number of data packets in a first predetermined number of data frames deterministically. In addition, a first portion of the non-deterministic content is inserted into a second predetermined number of data packets in the first predetermined number of data frames. A copy of the first predetermined number of data packets is generated. The first predetermined number of data frames is broadcast over a distribution network. The copy of the first predetermined number of data packets is inserted into a second predetermined number of data frames and a second portion of the non-deterministic content is inserted into the second predetermined number of data frames. The second predetermined number of data frames is broadcast after a predetermined time.

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 method of encoding data for transmission from a source to a destination over a communications channel is provided. A plurality of redundant symbols are generated from an ordered set of input symbols to be transmitted. A plurality of output symbols are generated from a combined set of symbols including the input symbols and the redundant symbols, wherein the number of possible output symbols is much larger than the number of symbols in the combined set of symbols, wherein at least one output symbol is generated from more than one symbol in the combined set of symbols and from less than all of the symbols in the combined set of symbols, and such that the ordered set of input symbols can be regenerated to a desired degree of accuracy from any predetermined number, N, of the output symbols.

The invention relates to a method and an arrangement for transmitting a digital signal consisting of symbols, which arrangement comprises a coder (308) for coding complex symbols to channel symbols in blocks having the length of a given K, means (312) for transmitting the channel symbols via several different channels and two or more antennas (314 to 318). The coder (308) is arranged to code the symbols using a code matrix, which can be expressed as a sum of 2K elements, in which each element is a product of a symbol or symbol complex conjugate to be transmitted and a N×N representation matrix of a complexified anti-commutator algebra, extended by a unit element, and in which each matrix is used at most once in the formation of the code matrix. A code matrix is also provided which is formed by matrices of a portion of the symbols placed on the diagonal of the code matrix and by matrices of a second portion of symbols along the anti-diagonal of the code matrix.

A method includes broadcasting, at a transmitter, messages comprising antenna configuration, antenna spacing and a number of antenna of the transmitter and reference signals; generating, at a receiver, a codebook comprising a plurality of antenna beams based on the broadcasted messages; receiving, at the receiver, the broadcasted reference signals; selecting, at the receiver, an antenna beam among the plurality of antenna beams within the codebook in dependence upon a predetermined performance criteria of a data communication system and in dependence upon the broadcasted reference signals; feedbacking to the transmitter, at the receiver, information comprising the antenna beam selected by the receiver; optimizing, at the transmitter, a beamforming process by utilizing the feedback information from the receiver; transmitting, at the transmitter, data signals by utilizing the optimized beamforming process; and receiving and processing, at the receiver, the data signals in dependence upon the selected antenna beams within the codebook.

A reduction in a peak-to-mean envelope power ratio of a multicarrier signal, represented as a time domain signal, is achieved by applying (76) an offset, indicative of a difference (74) between a mean signal level and a midpoint level of the time domain signal, to the time domain signal. Alternatively, constellation values of positive and negative frequency components are modified by differing functions to produce a modified data set. Preferably, the negative frequency components are set to a predetermined value (namely zero (124)) to provide an alternate coding scheme Once the multicarrier signal has been converted into a time domain representation, real and imaginary parts (126-128) of the modified data set that consequently only contain positive frequency components and zeros are compared with one another to identify (130) which of the real and imaginary parts has a lower peak-to-average signal ratio (134) for the time domain representation. Then, based upon which of the peak-to-average signal ratios is lowest (136), either the real and imaginary part of the time domain signal is selected for subsequent transmission (138).

A method and an apparatus for data transmission in a mobile telecommunication system supporting an enhanced uplink service are provided. A Transport Format Combination (TFC) selector determines TF information for data to be transmitted through a first data channel not supporting Hybrid Automatic Repeat reQuest (HARQ) and a second data channel supporting HARQ, and determines gain factors for the first and second data channel, and first and second control channel carrying control information for the first and second data channel. The gain factors are input to a physical channel transmission controller, and the physical channel transmission controller reduces the gain factor for the second channel if total transmit power required for transmission of the channels exceeds the predetermined maximum allowed power. A gain scaler adjusts transmit powers of the channels using the scaled gain factor and gain factors for the first data channel, the first control channel and the second control channel.