425 results about "Frequency space" patented technology

Controls for an optical scanner, such as a single fiber scanning endoscope (SFSE) that includes a resonating optical fiber and a single photodetector to produce large field of view, high-resolution images. A nonlinear control scheme with feedback linearization is employed in one type of control to accurately produce a desired scan. Open loop and closed loops controllers are applied to the nonlinear optical scanner of the SFSE. A closed loop control (no model) uses either phase locked loop and PID controllers, or a dual-phase lock-in amplifier and two PIDs for each axis controlled. Other forms of the control that employ a model use a frequency space tracking control, an error space tracking control, feedback linearizing controls, an adaptive control, and a sliding mode control.

A transmitter for minimizing a PAPR in OFDM communication system. The transmitter includes: a precoder for coding input symbols so that a signal rotation is generated, and generating a complex vector including the coded symbols; an encoder for performing a frequency-space mapping for the symbols generated as the complex vector according to a predetermined scheme; a random mapper for randomly mapping the symbols for which the frequency-space mapping has been performed on a frequency plane through at least one transmit antenna; an Inverse Fast Fourier Transform (IFFT) unit for performing an IFFT for the symbols for which the frequency-space mapping has been performed; and a gradient algorithm unit for receiving IFFTed signals from the IFFT unit and reducing the PAPR.

A method and apparatus for pilot-symbol aided channel estimation in a wireless digital communication system which transmits packets of N OFDM data blocks, each data block comprising a set of K orthogonal carrier frequencies. At the transmitter, pilot symbols are inserted into each data packet at known positions so as to occupy predetermined positions in the time-frequency space. At the receiver, the received signal is subject to a two-dimensional inverse Fourier transform, two-dimensional filtering and a two-dimensional Fourier transform to recover the pilot symbols so as to estimate the channel response.

Space-based wireless radiotelephone communications are provided in a satellite footprint over a satellite radiotelephone frequency band. The satellite footprint is divided into satellite cells in which satellite radiotelephone frequencies of the satellite radiotelephone frequency band are spatially reused. At least one of the satellite radiotelephone frequencies that is assigned to a given satellite cell in the satellite footprint is terrestrially reused outside the given satellite cell. A radiation pattern of at least the given satellite cell is modified to reduce interference with the at least one of the satellite radiotelephone frequencies that is terrestrially reused outside the given satellite cell.

An apparatus includes multiple signal paths for optically converting an optical signal to multiples of the optical signal at different respective carrier frequencies for reducing interference between wireless transmissions of the multiples of the optical signal. Preferably, the converting includes a first modulator for modulating the optical signal into a first optical carrier and an initial first-order sideband signal with a frequency spacing twice that of the first optical carrier and a first interleaver for separating the first optical carrier and the initial first-order sideband signal. The converting also includes a second phase modulator for modulating the first optical carrier into a second optical carrier and a second first-order sideband signal with a frequency spacing twice that of the second optical carrier.

A method is provided for multiple remote units (RU)s to efficiently utilize resources on a shared OFDM high speed data channel without collisions. A collision occurs when two or more RUs transmit on the same frequency at the same time. The method defines two distinct states for accessing the channel. These are the Arbitration state and the Data Transfer state. A base station transmits a flag on the downlink to notify the RUs of which state is in effect. RUs having a data message notify the base station by transmitting a frequency tone, which acts as a request to transmit data, during the arbitration state. The tone frequencies are frequency spaced to be mutually orthogonal, so that the base station can receive all the uplink requests simultaneously. Upon receiving the uplink request signals, the base station establishes the data transfer state and orders the uplink data messages from the remote units is a non-interfering sequence. A system for preventing uplink data message collisions in an OFDM communications system is also provided.

The invention discloses a method for random access of multiple carriers, which is applied to the condition of asymmetrical configuration of uplink and downlink carriers of an advanced long term evolution LTE-A system. The method comprises that: after receiving a leader sequence, a base station acquires a downlink component carrier corresponding to an uplink component carrier sending the leader sequence according to the frequency of the uplink component carrier and default frequency space between the uplink and downlink component carriers, sends random access channel RACH response messages on the downlink component carrier to a terminal, and sends competition resolving messages on the downlink component carrier sending the RACH response messages or the downlink component carrier agreed with the terminal to the terminal. The method can solve the problem of uncertainty of the downlink component carrier sending the RACH response messages and the competition resolving messages, and can maintain backward compatibility with LTE.

A communications system employs the use of both synchronous CDMA and FDMA to provide a variable bandwidth waveform with multiple bonded transmitters and receivers that are agile in both frequency and PN code to permit a variable bandwidth and variable rate multiple access system. In a first aspect the teachings provide the use of both CDMA and FDMA together to enable an improved concentration efficiency by making a larger pool of bandwidth available to each user. In a second aspect these teachings enable channel bonding across both code space and frequency space, thus making the system capable of operating within a variable (not necessarily contiguous) bandwidth and at a finely variable rate.

An Orthogonal Time Frequency Space Modulation (OTFS) modulation scheme that maps data symbols, along with optional pilot symbols, using a symplectic-like transformation such as a 2D Fourier transform and optional scrambling operation, into a complex wave aggregate and be backward compatible with legacy OFDM systems, is described. This wave aggregate may be processed for transmission by selecting portions of the aggregate according to various time and frequency intervals. The output from this process can be used to modulate transmitted waveforms according to various time intervals over a plurality of narrow-band subcarriers, often by using mutually orthogonal subcarrier “tones” or carrier frequencies. The entire wave aggregate may be transmitted over various time intervals. At the receiver, an inverse of this process can be used to both characterize the data channel and to correct the received signals for channel distortions, thus receiving a clear form of the original data symbols.

A near field communication front-end includes an up conversion module, a plurality of coils, and a down conversion module. The up conversion module is coupled to convert an outbound symbol stream into a plurality of outbound signals based on a frequency-space encoding scheme. The plurality of coils is coupled to electromagnetically transmit the plurality of outbound signals and to electromagnetically receive a plurality of inbound signals in accordance with the frequency-space encoding scheme. The down conversion module is coupled to convert the plurality of inbound signals into an inbound symbol stream in accordance with the frequency-space encoding scheme.

A synchronization of a pilot assisted channel estimation orthogonal frequency division multiplexing can be achieved by receiving a signal containing pilot symbols, providing an initial time and frequency synchronization to the signal, phase rotating the signal across time, transforming the signal with a fast Fourier transformation, phase rotating the signal across frequency, extracting the pilot symbols and generating a channel estimator. The phase rotating across time and the phase rotating across frequency are controlled by a phase rotation controller in accordance with the channel estimator. The initial time and frequency synchronization synchronizes the signal such that intercarrier interference effects and intersymbol interference effects are negligible. The signal may include plural carrier frequencies each having an arrival timing offset and a frequency offset. The signal may also include delay spread or Doppler spread. The phase rotation controller measures a phase different between the channel estimator at times k and k+Δk, where k is time and Δk is a symbol period and measures a phase difference between the channel estimator at frequencies n and n+Δn, where n is tone frequency and Δn is a frequency spacing between adjacent tones.

A wireless communication system receiver receives and processes a signal comprising at least two component carriers carrying data scheduled to the receiver and having center frequencies spaced apart by at least one component carrier frequency difference. Each component carrier comprises a number of subcarriers spaced apart by a system subcarrier frequency spacing. A common divisor is obtained for the at least one component carrier frequency difference and the system subcarrier frequency spacing. A symbol is received on the subcarriers of the component carriers and downconverted to baseband to produce a baseband symbol. A block of padding values is inserted in the baseband symbol to produce a padded symbol. The length of the block of padding values is such that intermediate subcarriers are inserted to yield a subcarrier frequency spacing for the padded symbol equal to the common divisor. Finally the padded symbol is Fast Fourier Transform, FFT, processed.

A magnetic resonance imaging apparatus includes an acquisition unit, a calculation unit, a recalculation unit, a correction unit and a generating unit. The acquisition unit acquires data from plural slices in an object by rotating a zonary region in frequency space by every repetition time. The calculation unit calculates correction parameters for motion correction. The recalculation unit recalculates at least a part of the correction parameters based on relationship between values of the correction parameters and at least one of real-spatial positions and times at which the data is acquired. The correction unit corrects the data using correction parameters including recalculated correction parameters. The generating unit generates image data based on corrected data.

A method and apparatus for communicating wirelessly comprising creating a plurality of sub-carrier signals by quadrature amplitude modulating data onto a plurality of sub-carrier frequencies spaced apart by a sub-carrier frequency spacing interval, frequency shifting the sub-carrier signals by one half of the sub-carrier frequency spacing interval, and modulating the sub-carrier signals onto a radio frequency carrier wave for wireless transmission.

A migration method using hybrid one-way and full-way (HOF) wave equation propagation. The HOF method extrapolates seismic wavefields in less complex media with a one-way wave equation propagator and extrapolates seismic wavefields in extremely complex media with a full-way wave equation propagator. For prestack depth migration, the HOF extrapolates source-side and receiver-side wavefields independently. Frequency-space domain and time-space domain imaging conditions are applied to the one-way and the full-way extrapolated wavefields, respectively. A suitable amplitude matching factor is introduced to combine the one-way and full-way images. The HOF method is a cost-effective migration that produces superior image quality with less noises and less computational resources.

A technique for optically converting wavelengths in a multi-wavelength system is disclosed. In one embodiment, wherein the multi-wavelength system has W wavelength channels, wherein W=2N, the technique is realized by selectively directing a received frequency channel corresponding to a respective wavelength channel based upon a predetermined frequency mapping. Then, the frequency of the selectively directed frequency channel is shifted at least once by an amount defined by ±21DELTAf, wherein DELTAf is the frequency spacing between adjacent frequency channels, and i=0, 1, . . . N-1.

An optical fiber Fourier measurement with switching white light interferometer implements Fourier transforms on white light spectrum output from transducer interferometer, the carrier frequency is Fourier spectrum defined by interferometer optical path difference, two sets of carrier frequency components are separated and symmetrical in the frequency space; one set of components is filtered for anti-Fourier transforms and plural logarithm operation, phase information of the transducer interferometer is set as an imaginary part of signals and separated from the background formed by lighting source spectrum outline and interference fringes contrast; the phase information of the transducer interferometer is limited within (minus Pi, Pi) according to operation procedure, the 2 Pi phases polarize of phase information is phase unwrapped, the measuring range is not limited with the 2 Pi phase; absolute optical path difference of transducer interferometer is calculated from phase information, thus realizing testing. The method of the invention prominently increases accuracy of white light spectrum peak measuring method and Fourier peak value frequency switching method.

An olfaction processor (OLP) (100) that generates RAW data (35) including content data (139d) relating to chemical substances is provided. The OLP (100) includes a generator (130) that generates the RAW data (35). The chemical substances include at least one of compounds, molecules, and elements. The generator (130) includes a conversion unit (131) that converts intensity variations, which show detected chemical substances included in data from at least one sensor that detects an amount that changes due to presence of at least one of the chemical substances, to the content data (139d) by mapping onto a frequency space where a plurality of frequencies have been respectively assigned to a plurality of specified chemical substances.