234 results about "Frequency encoding" patented technology

A method for the detection of analytes using resonant mass sensors or sensor arrays comprises frequency encoding each sensor element, acquiring a time-domain resonance signal from the sensor or sensor array as it is exposed to analyte, detecting change in the frequency or resonant properties of each sensor element using a Fourier transform or other spectral analysis method, and classifying, identifying, and / or quantifying analyte using an appropriate data analysis procedure. Frequency encoded sensors or sensor arrays comprise sensor elements with frequency domain resonance signals that can be uniquely identified under a defined range of operating conditions. Frequency encoding can be realized either by fabricating individual sensor elements with unique resonant frequencies or by tuning or modifying identical resonant devices to unique frequencies by adding or removing mass from individual sensor elements. The array of sensor elements comprises multiple resonant structures that may have identical or unique sensing layers. The sensing layers influence the sensor elements' response to analyte. Time-domain signal is acquired, typically in a single data acquisition channel, and typically using either (1) a pulsed excitation followed by acquisition of the free oscillatory decay of the entire array or (2) a rapid scan acquisition of signal from the entire array in a direct or heterodyne configuration. Spectrum analysis of the time domain data is typically accomplished with Fourier transform analysis. The methods and sensor arrays of the invention enable rapid and sensitive analyte detection, classification and / or identification of complex mixtures and unknown compounds, and quantification of known analytes, using sensor element design and signal detection hardware that are robust, simple and low cost.

A system and method are disclosed using continuous table motion while acquiring data to reconstruct MR images across a large FOV without significant slab-boundary artifacts that reduces acquisition time. At each table position, full z-encoding data are acquired for a subset of the transverse k-space data. The table is moved through a number of positions over the desired FOV and MR data are acquired over the plurality of table positions. Since full z-data are acquired for each slab, the data can be Fourier transformed in z, interpolated, sorted, and aligned to match anatomic z locations. The fully sampled and aligned data is then Fourier transformed in remaining dimension(s) to reconstruct the final image that is free of slab-boundary artifacts.

Methods and systems in a parallel magnetic resonance imaging (MRI) system utilize sensitivity-encoded MRI data acquired from multiple receiver coils together with spatially dependent receiver coil sensitivities to generate MRI images. The acquired MRI data forms a reduced MRI data set that is undersampled in at least a phase-encoding direction in a frequency domain. The acquired MRI data and auto-calibration signal data are used to determine reconstruction coefficients for each receiver coil using a weighted or a robust least squares method. The reconstruction coefficients vary spatially with respect to at least the spatial coordinate that is orthogonal to the undersampled, phase-encoding direction(s) (e.g., a frequency encoding direction). Values for unacquired MRI data are determined by linearly combining the reconstruction coefficients with the acquired MRI data within neighborhoods in the frequency domain that depend on imaging geometry, coil sensitivity characteristics, and the undersampling factor of the acquired MRI data. An MRI image is determined from the reconstructed unacquired data and the acquired MRI data.

The invention discloses a partial echo compressed sensing-based quick magnetic resonance imaging (MRI) method. The conventional imaging method has low speed and high hardware cost. The method comprises the following steps of: acquiring echo data of a random variable density part, namely intensively acquiring data in a central area of a k-space and acquiring the data around the k-space randomly and sparsely to generate a two-dimensional random mask, adding the two-dimensional random mask into every data point which needs to be acquired on a frequency coding shaft to form a three-dimensional random mask, and acquiring the data of the k-space according to the generated three-dimensional random mask; re-establishing by projection onto convex sets based on a wavelet domain which is de-noised by soft thresholding; and nonlinearly re-establishing a minimum L1 normal number based on finite difference transformation, namely sparsely transforming an image space signal x, determining an optimization objective and solving the optimization objective. By the method of the invention, partial echo technology and compressed sensing technology are combined and applied to data acquisition of MRI, sothat echo time is shortened, and data acquisition time is shortened at the same time.

Hierarchical audio coding and decoding method and system and hierarchical audio coding and decoding method for transient signals are provided. In the present invention, by introducing a processing method for transient signal frames in the hierarchical audio coding and decoding methods, a segmented time-frequency transform is performed on the transient signal frames, and then the frequency-domain coefficients obtained by transformation are rearranged respectively within the core layer and within the extended layer, so as to perform the same subsequent coding processes, such as bit allocation, frequency-domain coefficient coding, etc., as those on the steady-state signal frames, thus enhancing the coding efficiency of the transient signal frames and improving the quality of the hierarchical audio coding and decoding.

A system and method are disclosed using continuous table motion while acquiring data to reconstruct MR images across a large FOV without significant slab-boundary artifacts that reduces acquisition time. At each table position, full z-encoding data are acquired for a subset of the transverse k-space data. The table is moved through a number of positions over the desired FOV and MR data are acquired over the plurality of table positions. Since full z-data are acquired for each slab, the data can be Fourier transformed in z, interpolated, sorted, and aligned to match anatomic z locations. The fully sampled and aligned data is then Fourier transformed in remaining dimension(s) to reconstruct the final image that is free of slab-boundary artifacts.

In a method and magnetic resonance tomography apparatus for spatially resolved measurement of the magnetic high frequency field distribution in the apparatus, a double echo high frequency pulse sequence with a first excitation pulse following by at least two refocusing pulses are emitted for generation of a first echo and a following second echo. At least the excitation pulse is slice selective. In an excitation layer defined by the slice selective excitation pulse a first echo image and second echo image are spatially resolved by using suitable gradient pulses for phase or frequency encoding Using the relationships of the amplitudes of the first and second echo image in the various locations the flip angles representing the field strength at the relevant locations in the relevant slice are determined.

A method for generating a magnetic resonance image of a moving subject comprises tracking the position and orientation of a target volume and modifying acquisition parameters for each line of k-space data using current position and orientation information. By approximating the target volume as a rigid object, the current position and orientation is translated into an offset vector and a rotation which are used to modify the acquisition of each k-space line individually. The offset along a slice direction is compensated for by changing the transmit frequency. The offset along the frequency-encoding direction is compensated for by changing the frequency of a reference demodulation signal. The offset along the phase direction is compensated for by changing the phase of a reference demodulation signal, or by adding a phase into the line of k-space data after acquisition. The rotation is applied directly to the logical axes to change the angles between the logical axes and the physical axes of a magnetic resonance imaging system.

Methods and systems in a parallel magnetic resonance imaging (MRI) system utilize sensitivity-encoded MRI data acquired from multiple receiver coils together with spatially dependent receiver coil sensitivities to generate MRI images. The acquired MRI data forms a reduced MRI data set that is undersampled in at least a phase-encoding direction in a frequency domain. The acquired MRI data and auto-calibration signal data are used to determine reconstruction coefficients for each receiver coil using a weighted or a robust least squares method. The reconstruction coefficients vary spatially with respect to at least the spatial coordinate that is orthogonal to the undersampled, phase-encoding direction(s) (e.g., a frequency encoding direction). Values for unacquired MRI data are determined by linearly combining the reconstruction coefficients with the acquired MRI data within neighborhoods in the frequency domain that depend on imaging geometry, coil sensitivity characteristics, and the undersampling factor of the acquired MRI data. An MRI image is determined from the reconstructed unacquired data and the acquired MRI data.

The invention discloses a rock heterogeneous quantitative evaluation method based on magnetic resonance imaging. Three-dimensional space orientation of rock can be realized by layer selection pulse, phase coded pulse and frequency coded pulse. An imaging signal can be obtained by applying a spin-echo sequence, and optimization selection of imaging experimental parameters can be carried out through experimental scale. On the basis, a nuclear magnetic imaging signal obtained by experimental measurement is subjected to digital image processing so as to generate a pseudo color graph. By means of the relationship between the porosity and nuclear magnetic imaging signal intensity of a stand sample, the total porosity and porosity and distribution spectrum of a single layer can be obtained. Multi-layer imaging results are compared and a porosity heterogeneous coefficient is defined, so that the longitudinal porosity distribution characteristic and heterogeneity of rock can be obtained. In addition, by applying a first-order spherical variation function model and a grid search method, characteristic parameters of a variation function can be obtained. Heterogeneous coefficients and relative heterogeneous coefficients can be defined to realize longitudinal and horizontal heterogeneous quantitative characterization of rock.

A backscatter passive wireless control system and method employs frequency coding using frequency components generated from an interrogating field using a passive nonlinear element such as a diode in a passive transponder tag. In particular, InterModulation Distortion (IMD) frequency components may be generated which are shifted in frequency from the interrogating signal to assist in backscatter detection at a receiver but are still in band, e.g., in an ISM band. The shifted frequency components may be swept or stepped over a range and passive elements in the tag encode a tag ID by selecting specific frequencies to be backscattered. A manually operated switch may couple an antenna to the transponder to allow battery free control.

A method of filtering frequency encoded imaging signals includes receiving the frequency encoded imaging signals in the time domain and demodulating the frequency encoded imaging signals. The method further includes upsampling the frequency encoded imaging signals by an integer upsampling factor, reducing the bandwidth of the frequency encoded imaging signals, and downsampling the frequency encoded imaging signals by an integer downsampling factor. The frequency encoded imaging signals are resampled by a resampling factor substantially equal to the integer upsampling factor divided by the integer downsampling factor.

The invention discloses a radar pulse compression filter optimization design method applied to random signal waveforms. The method mainly solves the problem of pulse compression filter optimization design under constraint conditions of a main lobe width, processing gain loss and a sidelobe level. The radar pulse compression filter optimization design method includes the steps that firstly, new signal vectors are designed for radar transmitting signal waveforms and the filter length, and a signal matrix is established on the basis of the new signal vectors and is adjusted according to the pulse compression main lobe width at the same time; secondly, the allowable maximum processing gain loss is processed combined with pulse compression to form a constrained optimization equation; finally, the optimal filter coefficient under the constraint conditions is solved and obtained through a convex optimization tool. The optimal sidelobe level can be obtained under the conditions of the given pulse compression filter length, the main lobe width and the processing gain loss, meanwhile the method has the advantage of being irrelevant to signal modes, and the method is applied to signal pulse compression filter design of linear frequency modulation, phase encoding, frequency encoding and the like.

The invention discloses a magnetic resonance frequency and phase position double-encoding sampling method and an image reconstruction method. The sampling method comprises the following steps of (a) setting an acquisition sequence and acquiring k-space data; (b) performing N-time over-sampling to the frequency encoding gradient direction according to the acquisition sequence during acquisition and simultaneously adding frequency encoding gradient and phase position encoding gradient to control data acquisition tracks; (c) filling the data acquired in the step (b) into a k-space through an analog to digital converter (ADC) to form the k-space with an inclination factor N, wherein data points of the k-space are distributed along the frequency encoding gradient direction and the phase position encoding gradient direction in an inclined N*m rows*n columns mode, and (N-1) blank data points are filled between every two adjacent actually acquired data points in the frequency encoding direction and the phase position encoding direction, the N is an integer larger than 1, and the m and the n are positive integers. The magnetic resonance frequency and phase position double-encoding sampling method enables phase positions and frequency to be encoded simultaneously so as to control the k-space sampling tracks, enables acquisition times to be less than the acquisition s times of a traditional acquisition s mode, shortens the total acquisition time and enables reconstructed images not to have image artifacts basically.

Methods and systems for coding SAW OFC devices to mitigate code collisions in a wireless multi-tag system. Each device producing plural stepped frequencies as an OFC signal with a chip offset delay to increase code diversity. A method for assigning a different OCF to each device includes using a matrix based on the number of OFCs needed and the number chips per code, populating each matrix cell with OFC chip, and assigning the codes from the matrix to the devices. The asynchronous passive multi-tag system includes plural surface acoustic wave devices each producing a different OFC signal having the same number of chips and including a chip offset time delay, an algorithm for assigning OFCs to each device, and a transceiver to transmit an interrogation signal and receive OFC signals in response with minimal code collisions during transmission.

The invention provides a K space reconstruction method comprising exciting echo planar imaging (EPI) sequence for many times and collecting K space data in parallel, wherein the collected data comprises at least two data groups, a certain angle in the frequency encoding direction is formed between every two data groups and overlap portions are formed between data groups; further dividing phase encoding lines in each data group into a first group and a second group according to the difference of collection directions, the phase encoding lines in the first group being opposite to the phase encoding lines in the second group in collection direction; adding each group to the K space for fixing, wherein a position, most associated with other groups already added to the K space, is found for fixing when each group is added; and carrying out undersampled data filling by utilizing optimized K space data to realize K space reconstruction. According to the K space reconstruction method and device, EPI artifact correction can be realized without collecting calibration data additionally, thereby saving collection time and improving imaging speed.

The invention discloses a steady-state procession gradient multi-echo water and grease separation imaging method. The steady-state procession gradient multi-echo water and grease separation imaging method comprises the following steps of on the basis of a steady-state procession imaging sequence for conventional scanning on a magnetic resonance imaging system, repeatedly exciting the imaging area by a radio frequency pulse at the interval of 10ms magnitude or smaller short cycle TR; setting a pulse flip angle into +alpha / 2 in a first sequence repetition cycle, and eliminating the sampling period; alternatively setting the pulse flip angle into +alpha and -alpha in the subsequent sequence repetition cycle; using the layer selection gradient, phase encoding gradient and frequency encoding gradient to perform three-dimensional encoding, wherein the sum of integral areas of gradients in each bearing is zero, and the proton magnetizing vector procession is approximate to the steady state; enabling the magnetizing vectors to form three or two gradient echoes under the action of three or two positive and negative alternating frequency encoding gradients in each TR period, wherein the integral area of gradients in the frequency encoding direction is zero; performing direct phase encoding on the three or two echoes according to echo peak interval and water and grease chemical displacement difference value.

The present invention belongs to the field of radar communication technique, especially relates to method for design MIMO radar orthogonal discrete frequency code. The present invention employs linearity frequency modulation disperse frequency code (DFCW_LFM) and location relation of grating lobe and zero point of autocorrelation function of DFCW_LFM (shown in formula A) to determine relation of parameter N of DFCW_LFM signal with lower autocorrelation function and B / delta f to fall ASP. After gaining lower ASP, produce randomly K group original frequency code serial with lower autocorrelation, namely original group S0, and searching by improved genetic algorithm (MGA) provided by present invention, and the optimizing orthogonal discrete DFCW_LFM code which has lower autocorrelation and mutual-correlation compared to present DFCW_FF code. The orthogonal discrete DFCW_LFM code of present invention makes the MIMO radar has better detecting capability.

A method of and system for parallel imaging using a Magnetic Resonance Imaging (MRI) system is provided. The method comprises acquiring a plurality of magnetic resonance (MR) signals from a receiver coil array placed about a subject in the MRI system, where the receiver coil array has a plurality of receiver elements arranged in rows and, during application of a readout gradient in a frequency encoding direction, shifting receiver frequencies by a selectable amount for each row of the array in order to shift a limited field of view (FOV) in the frequency encoding direction.

The invention discloses a pilot frequency inserting method for a space-frequency encoding cascade cyclic delay diversity, which is applied to a multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system. After a data stream to be sent is encoded by an SFBC in a frequency domain, pilot frequencies are respectively inserted into each path of data stream on the basis of the number of the encoded data stream in the frequency domain. The invention further discloses a method for transmitting the diversity of the space-frequency encoding cascade cyclic delay diversity, which includes the steps that the data stream to be sent is encoded by the SFBC in the frequency domain and then pilot frequencies are respectively inserted into each path of data stream on the basis ofthe number of the encoded data stream in the frequency domain; the data stream inserted with the pilot frequencies is transformed to a time domain by Fourier transformation. After CDD is encoded, thedata is respectively sent to a transmitting antenna. The method of the invention overcomes the defect that the transmission performance of an SFBC plus CDD diversity mode is interfered due to unreasonable pilot insertion in the existing diversity transmitting method of the MIMO-OFDM system, thus improving the reliability of the whole communication system.

The invention discloses a single-scanning magnetic resonance quantitative T2 imaging reconstruction method based on a residual network and relates to magnetic resonance imaging methods. According to the method, four small-angle excitation pulses with the same deflection angle are utilized, and a period of evolution time is available after each excitation pulse, so that transverse relaxation time T2 of each echo signal is different; a shift gradient of a frequency coding dimension and a phase coding dimension is added after each excitation pulse, so that the positions of the signals generated by different excitation pulses in a k space are different; multiple echo signals with different transverse relaxation time are obtained in one time of sampling; then the sampling signals are input intothe trained residual network after being subjected to normalization, zero-setting and fast Fourier transformation for reconstruction to obtain a quantitative T2 image; training data of the residual network comes from simulation data; and a template is randomly generated first, then an input image of the network is obtained by simulating experiment environment sampling, the template is used as a tag, and a mapping relation between the input image and an output image is obtained through training.

Disclosed in the invention is a high-precision three-dimensional chemical shift imaging method. A water image and a fat image that are separated from each other and in-phase graphs and anti-phase graphs of the water image and the fat image can be obtained by scanning once by using a three-dimensional single excited long echo string collection way, a radio frequency refocusing pulse string or frequency coding gradient technology, a pre scanning scheme having an echo amplitude and phase error precision correction feature, and a data post processing method. The method has the low requirements on magnetic field uniformity and gradient system performances; and the image quality and the diagnosis value can be improved obviously.

A magnetic resonance imaging (MRI) method is provided in which a sample is subjected to a gradient echo imaging sequence having a plurality of basic sequence elements each of which includes a radiofrequency (RF) pulse, at least one frequency encoding gradient moment kx for generating a magnetic resonance (MR) signal, at least one first phase encoding gradient moment ky for phase encoding the MR signal and a data acquisition period during which k-space data reflecting the MR signal are acquired. The frequency encoding gradient moment kx and the first phase encoding gradient moment ky are applied such during the data acquisition period of each basic sequence element, that the k-space data are acquired in a radial direction and asymmetrically with respect to the center of k-space in the direction from the periphery towards the center of k-space.

A method for generating a magnetic resonance image of a moving subject comprises tracking the position and orientation of a target volume and modifying acquisition parameters for each line of k-space data using current position and orientation information. By approximating the target volume as a rigid object, the current position and orientation is translated into an offset vector and a rotation which are used to modify the acquisition of each k-space line individually. The offset along a slice direction is compensated for by changing the transmit frequency. The offset along the frequency-encoding direction is compensated for by changing the frequency of a reference demodulation signal. The offset along the phase direction is compensated for by changing the phase of a reference demodulation signal, or by adding a phase into the line of k-space data after acquisition. The rotation is applied directly to the logical axes to change the angles between the logical axes and the physical axes of a magnetic resonance imaging system.

The invention discloses a magnetic resonance parallel imaging method of a multi-constrain sliding window. The method sequentially comprises the following steps; (1) a multi-channel coil is utilized for conducting full sampling on a middle region of K space, and forward-direction, backward-direction and self reconstruction constraint weights are respectively obtained in a fitting mode; (2) the sliding window is selected from an accelerating sampling region, the sliding window moves respectively in the direction of frequency coding and the direction of phase coding, the collected data are utilized by the sliding window at each position for reconstructing data which are not collected, and initial estimation values, corresponding to each position, in the sliding window are obtained; (3) a linear weighted average method is adopted to gain K space output values which are not collected according to the initial estimation values, corresponding to each position, in the sliding window; (4), two dimensional Fourier transform is utilized for converting K space data which are not collected into images, and all coil images are united to obtain the final output image. Image artifacts and noise of the reconstructed image are obviously reduced.

The invention discloses a radar orthogonal waveform design method based on frequency modulation and phase modulation of a chaotic sequence, comprising the following steps: S1, using a chaotic system to generate a chaotic sequence of which the length is N*P, and cutting the chaotic sequence into P sequence sections (the length of each sequence section is N), selecting one sequence section, and letting the sequence section be {x(0), x(1), x(2),...,x(N)}; S2, encoding a chaotic joint frequency modulation and phase modulation signal, dividing a pulse into a series of equal sub pulses, and carrying out frequency modulation differently on different sub pulses, and then, using the sequence section obtained in S1 to carry out phase encoding on each cycle of a waveform in each frequency encoding sub pulse, and obtaining a phase-frequency joint modulation chaotic radar signal through use of a randomly-generated initial phase; and S3, calculating a complex envelope signal of the phase-frequency joint modulation chaotic radar signal obtained in S2. The signal frequency and phase change as a chaotic signal changes, the orthogonality of signals is improved, and the interception probability is reduced.

The correction of the light frequency of a light source may not be needed, a transmission belt is not increased, but a plurality codes are used. The light frequency width of the light source is set to be FSR and the code length of all codes are set to be FSR and is enabled to be provided with the orthogonality. Each light intensity frequency characteristic of an nth optical coded signal is set to be Cn(f)=[1+cos(2pion sf / FSR+r pion / 2) / 2(s is an integer of 1-the maximum code / 2, r=0or1)], the orthogonality is given between the optical encoding signal, or continuous light frequency code chips are distributed to the arrangement of code chips which form the optical encoding signal in turn, the light frequency of each code chip '1'is output, and codes such as a Hadamard code word (0101) and (0011) of a repeated second order and a filter with optical filter characteristics of a connecting code which connects the Hadamard code word are used to enable light source light to obtain the optical optical encoding signal. A coding light frequency region (31) and a decoding light frequency region (32) are covered on a drifting region of light source frequency. Delta F1and Delta F2 in the graph 13 are drifts of the light source frequency.