1190 results about "Fft fast fourier transform" patented technology

Disclosed is a method, a computer program product and a device that includes a receiver for receiving a downlink signal transmitted into a cell. The receiver is operable to obtain time, carrier frequency and cell-specific preamble synchronization to the received signal and includes a plurality of synchronization units that include a first detector to detect a frame boundary using preamble delay correlation; a second detector to detect the frame boundary with greater precision using a conjugate symmetry property over a region identified by the first detector; a cyclic prefix correlator to resolve symbol boundary repetition; an estimator, using the cyclic prefix, to estimate and correct a fractional carrier frequency offset; an operator to perform a Fast Fourier Transform of an identified preamble symbol and a frequency domain cross-correlator to identify cell-specific preamble sequences and an integer frequency offset in sub-carrier spacing. The transmitted signal may be a downlink signal transmitted into the cell from a base station that is compatible with IEEE 802.16e (WiMAX).

Signal construction, detection and estimation techniques for use in uplink timing synchronization and access control in an orthogonal frequency division multiplexed (OFDM) wireless system or other type of wireless communication system. In accordance with an illustrative embodiment of the invention, timing and access signals to be transmitted in designated timing and access intervals are constructed from orthogonal multitone signals. The multitone signals may be similar to multitone signals used in OFDM data transmission, except that a cyclic prefix associated with reception of the signals in a base station is extended to cover the timing errors of mobile stations not yet synchronized. The invention also provides design techniques which optimize the time resolvability and peak-to-average ratio of the multitone signals, an efficient fast Fourier transform (FFT) based technique for maximum likelihood timing estimation, and a robust linear filtering technique for averaging timing estimates from different synchronizations.

A signal processing system for processing satellite positioning signals is described. The system comprises at least one processor and a signal processor operating under a number of operational modes. The signal processor includes at last one of a signal processing subsystem, a fast Fourier transform (FFT) subsystem, and a memory subsystem that are each dynamically and independently configurable in response to the operational modes. Further, the system includes a controller that couples to control transfer of data among the signal processing subsystem and the FFT subsystem via the memory subsystem. Configurability of the memory subsystem includes configuring the memory subsystem into regions according to the operational modes where each region is accessible in one of a number of manners according to the operational modes.

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 transmitting apparatus, receiving apparatus, communication system, and a signal processing method for each apply a suitable modulation method and transmission path estimation method in accordance with the characteristics of the transmission information and capable of improving the transmission efficiency. At the transmission side, the method of estimation of the transmission path and the modulation method are selected in accordance with an attribute of the data to be transmitted, for example, the size of a packet to be transmitted, the transmission data is mapped by the selected modulation method, the signal is processed in accordance with the transmission path estimation method, and a transmission signal is created by increase fast Fourier transform processing and transmitted. At the reception side, the received signal is fast Fourier transformed, the transmission path is estimated by the transmission path estimation method selected at the transmission side, the received signal is corrected in accordance with the result, and the received data is reproduced in accordance with the modulation method. Therefore, it is possible to always adopt the optimum transmission method in accordance with the attribute of the transmission data etc. and possible to realize an improvement of a transmission efficiency and an enhancement of the quality of communication.

A method and transceiver for wireless multicarrier communications. At the transmitter side, conventional OFDM symbols, after inverse fast Fourier Transform, are scrambled in time domain and then guard-interval (GI) inserted, up-converted at the carrier frequency for transmission. At the receiver side, after GI removal and frequency domain channel equalization, the received signal is transformed into time-domain by inverse fast Fourier Transform. The time-domain equalized signal is descrambled in time domain and then transformed back to the frequency domain before it is rate-matched, demodulated and decoded. This time-domain scrambling and descrambling method can be used in a wireless OFDM system such as WLAN, cellular OFDM, and MC-CDMA.

The invention interferes local reference light with Brillouin diffused light transferred back by a sensing optical fiber, a Brillouin diffused spectrum electrical signal generated completely passes through a broadband low pass wave filter, the sampling is performed by the high speed acquisition and the processing circuit, a quick speed Fourier transformation is performed, a Brillouin diffused spectrum is obtained; then a Lorentz fitting is performed, and a Brillouin frequency shift of each unit on the whole optical fiber is obtained finally; the relation of the Brillouin diffused spectrum, and the strain or the temperature is utilized to realize a full-distribution type measurement of the strain or the temperature. The whole Brillouin diffused spectrum on the whole sensing optical fiber can be obtained in an impulse detecting circle by a processing method of the high speed acquisition, and the processing circuit and the quick speed Fourier transformation adopted by the invention, the measuring speed is improved to an order of magnitude compared with the prior technology on the premise of not decreasing the resolution of a measuring space and the measuring accuracy, thereby improving a speech to noise ratio to more than a plurality of times, the measuring accuracy is improved to a great extent, and the structure of the invention device is simple.

The present invention relates to a novel matrix-valued transform framework to process digital signals. According to one aspect of the invention, matrix-valued methods and apparatus are described to transform a vector-valued discrete-time data sequence from time-domain into frequency-domain. In another aspect, matrix-valued methods and apparatus are described to transform a vector-valued data sequence from frequency-domain into time-domain. Furthermore, the new framework disclosed in this invention also provides a plurality of methods and apparatus for basic signal processing functions and operations of a matrix-valued communication system. These functions and operations include but are not limited to matrix-valued fast Fourier transformation, matrix-valued linear and circular convolution, matrix-valued correlation, matrix-valued multiplexing and de-multiplexing, and matrix-valued data coding and decoding.

Disclosed herein is an apparatus for evaluating the safety of a building. The apparatus includes first and second measurement instruments which measure earthquake accelerations of the top and bottom stories, a fast Fourier transform unit which performs fast Fourier transform on the earthquake accelerations, an integration unit which double-integrates the measured earthquake accelerations and creates drift data of the top story and the bottom story, a maximum inter-story drift ratio calculation unit which calculates a maximum inter-story drift ratio, a natural frequency change rate calculation unit which determines a natural frequency of the building, and compares the natural frequency with an ambient natural frequency of the building so as to calculate a natural frequency change rate, and a building safety evaluation unit which compares the maximum inter-story drift ratio and the frequency change rate with preset evaluation criteria and outputs a result of evaluation in the safety of the building.

A fast position tolerant and economical fingerprint verification algorithm and software implementation is disclosed. The algorithm has very important advantages in comparison to existing fingerprint verification algorithms like minutia extraction or full image analysis based on a series of two dimensional fast Fourier transforms (FFT's) and two dimensional cross correlation in speed, compactness of the biocript and finger positioning for verification. It is based on a small "yardstick" pattern being moved inside the image to be verified, and when a match is found the rest of the verification process is started. The software code implements the algorithm in the most efficient way for utilization on a digital signal processor architecture. A main area of application is in fingerprint identification and verification, but it could be implemented with same success in other image verification systems like iris, eye, face etc., where two images should be compared. The algorithm is adaptive, so various false acceptance and false rejection coefficients could be utilized very easily. It also produces a very compact biocript, which leads to better memory utilization in fingerprint databases.

Apparatus and method for non-contact ultrasonic detection of features on or within the walls of hollow pipes are described. An air-coupled, high-power ultrasonic transducer for generating guided waves in the pipe wall, and a high-sensitivity, air-coupled transducer for detecting these waves, are disposed at a distance apart and at chosen angle with respect to the surface of the pipe, either inside of or outside of the pipe. Measurements may be made in reflection or transmission modes depending on the relative position of the transducers and the pipe. Data are taken by sweeping the frequency of the incident ultrasonic waves, using a tracking narrow-band filter to reduce detected noise, and transforming the frequency domain data into the time domain using fast Fourier transformation, if required.

The invention discloses an SC-OFDMA-based satellite mobile communication system for a forward link, which belongs to the field of satellite mobile communication. The SC-OFDMA-based system for the forward link is characterized in that single carrier signals of a user are mapped to different sub-carriers through DFT (discrete Fourier transform) or FFT (fast Fourier transform) and then subjected to IFFT (inverse fast Fourier transform) to realize orthogonal transmission of each user signal so as to improve the utilization rate of high frequency spectrum resources and reduce the peak-to-average power ratio of the satellite forward link; and in the multi-beam-based satellite mobile communication system, different sub-carrier groups are distributed to the users in a beam overlapped area according to the beams belonging to the users so as to reduce the co-channel interference between the low beams and fulfill the aim of improving the capacity of the system.

Several techniques are disclosed for isolating either heart or breath rate data from a photoplethysmograph, which is a time domain signal such as from a pulse oximeter. The techniques involve the use of filtering in the frequency domain, after a Fast Fourier Transform (FFT) has been conducted on a given photoplethysmograph also references as a given set of discrete time-domain data. The filtering may be applied to an identified fundamental frequency and one or more harmonics for heart related parameters. The filter may be truncated to the frequency data set and further applied multiple times to improve roll off. After filtering, an Inverse FFT (IFFT) is used to reconstruct the time-domain signal, except with undesirable frequency content eliminated or reduced. Calculation or measurement of parameters is then conducted on this reconstructed time-domain signal.

A detection method of double-threshold constant false alarm movement object on double-base synthetic aperture radar includes finalizing distance compression of various pulse-sampling, dividing orientation time to be multiple CPI, carrying out FFT in each CPI to enter orientation frequency domain, comparing data amplitude of frequency channel at external of clutter region with the first threshold and outputting point trace, making coagulation on point trace, making Hough transform in point trace domain and making decision of the second threshold.

Spatial encoding in magnetic resonance imaging (MRI) techniques is achieved by sampling the signal as a function of time in the presence of magnetic field gradients, e.g., X, Y, and Z gradients. The gradient magnets have in the past been assumed to generate a linear gradient, and typical image reconstruction techniques have relied upon this assumption. However, to achieve high speed performance, gradient magnets often sacrifice linearity for speed. This non-linearity, in turn, results in distorted images, the distortion often being sufficiently large to compromise the usefulness of MRI images for stereotaxy or longitudinal studies, where precise volumetric information is required. The disclosure provides practical methods for correcting distorted images resulting from such non-linearity in the gradient fields, as well as distortions resulting from translational, rotational, and/or winding/design errors in the field generating devices. The methods employ spherical harmonic expansions of the gradient fields and fast Fourier transform techniques to provide well-corrected images without undue computational burdens.

Channel estimation values of pilot symbols for channel compensation of data symbols in an OFDM receiver can be used, even in cases where FFT extract position differs for each frame. The OFDM receiver is characterized in having a circuit which calculates the amount of phase rotation that is generated by the difference in timing at which the individual symbols are extract as objects of a fast Fourier transform when the fast Fourier transform processing is performed by a fast Fourier transform circuit, and further a circuit which corrects the amount of phase rotation for the channel estimation value determined by a channel estimating circuit.

A transmitting apparatus, a receiving apparatus and methods of controlling these apparatuses are provided. The transmitting apparatus includes: an input processor configured to process a plurality of input streams to generate a plurality of base band frames; a bit interleaved and coded modulation (BICM) processor configured to perform forward error correction (FEC) coding, constellation mapping, and interleaving on the plurality of baseband frames; a symbol generator configured to add signaling data to the plurality of baseband frames output from the BICM processor to generate an orthogonal frequency division multiplexing (OFDM) symbol; and a transmitter configured to select at least one of a plurality of pilot patterns based on a fast Fourier transform (FFT) size and a guard interval fraction, insert a pilot in the OFDM symbol according to the selected pilot pattern, and transmit a stream including the pilot-inserted OFDM symbol. Thus, a data transmission rate is increased and accurate channel estimation is performed, through inserting different pilots according to different FFT sizes and guard interval fractions.

A method and apparatus for all optical orthogonal frequency division multiplexing (OFDM) employing Inverse Fast Fourier Transform/Fast Fourier Transform by integrated coupler interferometrically.