79 results about "Modulation spectrum" patented technology

A system and method is disclosed for reconstructing high frequency components of a digital audio signal using a harmonic enhancer in a baseband integrated circuit of a receiver handset. The original spectrum of the digital audio signal is upsampled in a times two (2) upsample unit to double the size of the bandwidth. A low pass filter then removes a high frequency alias of the original spectrum. The spectrum is then modulated with a first carrier frequency and sent to a first filter bank where a low pass filter and a high pass filter shape the modulated harmonic spectrum. After gain adjustment, the modulated harmonic spectrum is added to a delayed version of the original spectrum. Additional harmonic spectra are similarly created at other carrier frequencies and added to the audio output spectra to reconstruct high frequency components of the audio signal.

The invention relates to a method and a device for detecting gas, in particular to a modulation spectrum gas detection method based on quasi-continuous diode laser, and a device thereof. The invention adopts a technical proposal that a quasi-continuous diode laser spectrum modulation method for gas detection comprises the following steps: a modulation signal generator outputs a modulation signal and a reference signal; the modulation signal is supplied to a laser driver for controlling the injection current of a quasi-continuous diode laser; the reference signal is supplied to a lock-in amplifier and used as the reference signal; laser emitted by the quasi-continuous diode laser passes through to-be-detected gas and then is received by a photodetector; the output of the photodetector is transmitted to a preamplifier, amplified and then sent into the lock-in amplifier; and output signals of the lock-in amplifier are sent into a computer via an AD converter, processed and analyzed, so as to obtain the species and concentration data of the detected gas. The method is mainly applied to occasions needing trace gas detection with high sensitivity and high resolution.

The invention discloses a music similarity detection method based on mixed characteristics and a Gaussian mixed model. According to the basic thought, the method comprises the steps of using a gamma-tone cepstrum coefficient for conducting similarity detection, and using weighting similarities of various characteristics as a final detection result; providing a modulation spectrum characteristic based on a frame shaft, using the characteristic for representing a music long-time characteristic, and using the combination of the long-time characteristic and a short-time characteristic as the input of modeling in the next step; using the Gaussian mixed model for conducting modeling on the music characteristics, firstly, utilizing a dynamic K mean value method for conducting initialization on the model, then, using an expectation-maximization algorithm for conducting model training, obtaining accurate model parameters, and finally using a log-likelihood ratio algorithm for obtaining the similarities between the pieces of music. According to the music similarity detection method, the obtaining of the music characteristics is more sufficient and thorough, the accuracy degree of music recommendation is improved, the characteristic vector dimensionality can be reduced, the information memory content of a music database is reduced, and the accuracy degree of the music recommendation is improved.

The invention discloses an underwater acoustic target radiation noise modulation spectrum reconstruction method based on the group sparse structure. The method comprises the following steps that step1, a continuous spectral component R<c> (t) and a linear spectral component R<l> (t) of underwater acoustic target radiation noise are simulated to form underwater acoustic target radiation noise R (t); step 2, the R (t) is subjected to amplitude modulation to obtain a modulating signal x (t); step 3, the x (t) is subjected to normalization, and a band-pass filter is used for obtaining noise modulation signals y<l> (t) of L frequency bands; step 4, amplitude modulation data of the y<l> (t) on each sub-band are estimated, wherein the formula (please see the specification for the formula); step5, a formula (please see the specification for the formula) are subjected to discrete sampling and are represented by a sparse frequency coefficient, wherein the formula (please see the specificationfor the formula), and through designing of prior distribution of a formula (please see the specification for the formula), a high resolution modulation spectrum generation model based on the group sparse structure is constructed; step 6, posteriori distribution of a formula (please see the specification for the formula) is derived based on the expectation maximization method; and step 7, a parameter estimation formula is used for an iterative solution of a formula (please see the specification for the formula) to estimate a high resolution sparse modulation spectrum. Correlation of modulationspectrum positions of sub-bands of underwater acoustic target radiation noise is used for achieving high resolution reconstruction of the underwater acoustic target radiation noise modulation spectrum.

A device for recognizing bearing damage of a bearing (3), on which an object (4) which rotates at a rotational frequency is mounted, having at least one oscillation sensor (2) for converting an oscillation signal output by the bearing (3) into an electrical signal and having a calculation unit (8) for performing a first frequency transformation for multiple time windows of the oscillation signal to generate multiple time window spectra associated with the particular time windows and for performing a second frequency transformation for multiple frequency bands of the time window spectrograms to generate a multiband modulation spectrum, which, for modulation frequencies which are a function of the rotational frequency of the rotating object (4) because of bearing damage of the bearing (3), have signal amplitudes, the level thereof disclosing an extent of the bearing damage.

A voice signal dynamic feature extraction method based on MUSIC (multiple signal classification) and modulation spectrum filter mainly comprises voice signal preprocessing, MUSIC spectrum estimating, modulation spectrum filter, spectrum energy modulating and calculating, log energy calculating and discrete cosine transformation (DCT). The modulation spectrum filter can not only fully reflect dynamic features among voices but has low sensitivity of voice environment owing to the modulation spectrum filter has a time-frequency clustering, so that according to different reflections of interference signals and voice signals on the modulation information, the modulation spectrum filter uses spectrum estimating technology based on multiple signal classification, modulates the spectrum filter of obtained MUSIC spectrum and extracts cepstrum coefficients of the MUSIC spectrum as feature parameters. Compared with the prior art, the voice signal dynamic feature extraction method based on MUSIC and modulation spectrum filter has good robustness and not only significantly improves the recognition rate of a voice recognition system but has played a good foreshadowing role for follow-up studies of voice signals.

A microangiography method and system based on full-space modulation spectrum splitting and angle compounding is disclosed. Label-free three-dimensional optical coherence tomography angiography is realized by combining the three-dimensional space resolution capability of an optical coherence tomography and the motion recognition capability of a dynamic scattering technology. Probe light of different incident angles is encoded with a transverse scanning modulation spectrum in a spatial frequency domain, incident angle-resolved sub-angiograms which are independent of one another are obtained by splitting the modulation spectrum, and an angiogram with multiple space angles compounded is realized. Conjugate mirror images are removed from a depth (z) domain, a complex-valued OCT interference spectra are reconstructed, the full-space modulation spectrum is obtained in the spatial frequency domain, and the overlap of the modulation spectrum conjugate mirror images is avoided. And the absolute flow velocity of blood flow can be measured through a multi angle-resolved probing technology.

The invention discloses a modulation spectrum characteristic fidelity enhancement method for ship propeller cavitation noise based on the adaptive window length. The method comprises the steps of first, carrying out broadband square demodulation on ship propeller cavitation noise signals; second, pre-estimating a demodulation spectrum, detecting the line spectrum position of the demodulation spectrum, and giving the frequency domain signal-to-noise ratio of each line spectrum; third, determining the harmonic frequency of each line spectrum frequency relative to a pre-estimated value of the propeller shaft frequency; fourth, carrying out weighted fusion on the line spectrum frequencies, and estimating the propeller shaft frequency; and fifth, adaptively adjusting the analysis window lengthof the demodulation spectrum according to the estimated propeller shaft frequency, and carrying out secondary estimation on the demodulation spectrum. The modulation spectrum characteristic fidelity enhancement method adaptively adjusts the analysis window length of the demodulation spectrum according to the estimated propeller shaft frequency by using the inherent integer multiple relationship between each demodulation spectrum line spectrum frequency and the propeller shaft frequency, carries out secondary estimation on the demodulation spectrum, and obtains the demodulation spectrum with fidelity enhancement of modulation spectrum characteristics.

The invention relates to a propeller shaft frequency searching method based on improved noise envelope signal recognition. The method includes: enveloping an original hydrophone signal, and performingHilbert-Yellow transform on each wavelet packet signal to obtain a wavelet envelope signal; performing wavelet reconstruction to obtain an improved noise envelope signal; calculating a time correlation spectrum, take a line spectrum protruding at the peak of the low frequency band as the suspected shaft frequency; setting a step size smaller than the frequency resolution according to the demand;forming a suspected shaft frequency set with the suspected shaft frequency as the center; performing cyclic correlation calculation on a time correlation spectral signal on each suspected shaft frequency to obtain the frequency statistical amount of a cyclic modulation spectrum; and finally searching the shaft frequency of a target according to the frequency statistical amount. The method of the invention corrects axial frequency offset errors generated by the conventional cyclic modulation spectrum methods in the spectrum calculation process, improves the accuracy of the shaft frequency detection, greatly reduces the calculation amount of the loop iteration, and is convenient to implement in engineering application.

The device includes digital modulation in base band, digital up-conversion quadraphase modulator, and D/A converter in high speed. The digital modulation part includes generation module of switching control signal, diverter switch of modulation output, two pieces of diverter switch of modulation input, GMSK and 8PSK modulation modules in base band. The generation module of switching control signal generates one route of output switching control signal and two routes of input switching control signal. The two routes are anti phase. There is only one time slot cycle between output switching control signal and one of input switching control signal. Two pieces of diverter switch of modulation input are connected to data to be modulated and fixed bit 1 respectively. Digital up-conversion quadraphase modulator includes CIC filter and low pass FIR filter. Advantages are: switching modulation modes smoothly, better wireless indexes including modulation spectrum and switch spectrum.

The invention discloses a complex analytic optimal wavelet demodulation method which is characterized by comprising the following steps of: obtaining a vibration signal spectrogram, and capturing an effective frequency band centralized region; setting a shape factor sigma of a Morlet wavelet and an initial value of the initial frequency omega 0, thereby obtaining the wavelet factor Cs(b, a); obtaining continuous wavelet amplitude value spectrum information measure SH; improving the wavelet kurtosis; calculating the smooth index; calculating the optimal wavelet envelope spectrum; and detailing a modulation spectrum, and locating the fault of a detected target. According to the invention, not only are analysis wavelet parameters optimized and selected, but also the conventional wavelet kurtosis calculation method is improved, and the accuracy of screening the wavelet coefficients is improved; meanwhile, in order to solve the problem that the wavelet coefficient features decomposed by fault signals at the early stage are not obvious, the smooth index is additionally set, which plays better positioning and screening effects on the wavelet coefficients for the fault frequency band. The method not only can disclose weak fault features in complex signals in the multi-component signals accurately and effectively, and has high practical value.

The present invention relates to a method and equipment for analyzing noise source, especially noise of vehicle. The method for analyzing the noise of the noise source comprises the following steps: determining a plurality of modulation spectra Pm (n, m) by Fourier transform using a signal characteristic of a signal of a function with measuring time as structural sound and/or airborne sound, calculating paramter characteristics of noise to be analyzed from the modulation spectra, and real time executing the calculation of the paramter characteristics from operation of the noise source. Improved calibration of the pulse type noise phenomenon can be realized by using the present invention.

The invention discloses an angle composite speckle denoising method and system for full-channel modulation encoding. Generally, low-coherence detection is adopted during optical coherence tomography (OCT) imaging, and images obtained through the technology are likely to be influenced by speckle noise. A conjugated structural mirror image is deleted in a depth domain, a complex-value OCT interference spectrum is reconstructed, and a wide transverse scanning modulation spectrum without the conjugated structural mirror image is obtained in a full-channel space frequency domain; by means of the modulation spectrum, modulation encoding of detection light in different incident angles is achieved, and mutually independent incident angle resolution structural subgraphs are obtained by segmenting the modulation spectrum; the obtained structural subgraphs are subjected to composite average to obtain a final OCT structural image. The OCT structural image is obtained through the angle composite technology, speckle noise is reduced, the signal-to-noise ratio is increased, and structure details are clearer. Besides, the full-channel transverse scanning modulation spectrum is used for angle encoding and compositing so that speckle noise can be reduced and image quality can be improved to the maximum extent.

Utility data modulation is superimposed on a payload data modulator optical signal by exploiting spread spectrum techniques by virtue of one embodiment of the present invention. Utility data transmission rates of e.g., 200 Kbps, can be achieved without impairment to payload data transmission. The utility data modulated signal spectrum overlaps or is entirely within the payload data modulation spectrum, therefore, overcoming problems with optical amplifier gain control and pink noise.

The invention provides a method for electric brain stimulator. In the beginning, obtaining a brain functional amplitude modulation spectrum, wherein the brain functional amplitude modulation spectrum is a relationship between carrier frequency and amplitude-frequency on different brain sites. Then selecting a first alternating current frequency, wherein the first alternating current frequency is determined by the amplitude-frequency in which the brain functional amplitude modulation spectrum display a maximum power relation value, or a maximum correlation value with any behavior index of behavior and cognitive functions. And selecting a second alternating current frequency, wherein the second alternating current frequency is determined by the carrier frequency in which the brain functional amplitude modulation spectrum display a maximum power relation value, or a maximum correlation value with any behavior index of behavior and cognitive functions. In the end, outputting an alternating current signal, the alternating current signal is generated based on a first cosine function of the first alternating current frequency, a second cosine function of the second alternating current frequency, or a combination of the first cosine function and the second cosine function.

The invention discloses a pressure-modulation-spectrum-technology-based noninvasive glucose detection system comprising a light source, a power supply, a pressure modulator, a plurality of detectors, and a computer. The light source is controlled by the power supply to generate light with a needed waveband and the generated light reaches a human tissue; the pressure regulator presses the human tissue periodically; the light is reflected from the human tissue and then is transmitted to the detectors, wherein a certain distance is formed between the light incident position and the detector detection position; the detectors send collected data to the computer to carry out processing, thereby extracting spectrum information and concentration information of glucose. According to the invention, with the system, the absorption signal of the glucose can be substantially enhanced, so that the glucose detection becomes reliable; and repeated measurement can be carried out.