38results about How to "Fast Fourier Transform" patented technology

The invention discloses a digital processing method of an altimeter of a linear frequency modulation continuous wave radar, which belongs to the field of the radio altimeters. The digital processing method comprises the following steps: step 1, obtaining beating signals from an orthogonal mixer arranged at the front end of the altimeter of the radar, and carrying out A/D (analog-to-digital) sampling to obtain a digital signal sequence; step 2, performing Fourier transform on the digital signal sequence, and calculating the amplitude of a spectral line; step 3, judging according to the amplitude of the spectral line of an amplitude spectrum, and measuring the beating frequency of the digital signal sequence; step 4, refining the frequency spectrum, calculating the slope correction of saw-tooth wave, and correcting the slope of the voltage signals of the saw-tooth wave; and step 5, calculating the high value of the current altimeter according to the slope of the voltage signals of the saw-tooth wave. The FFT-CZT method adopted by the invention is insensitive to noises and can perfectly work at lower signal-to-noise ratio, but the measurement precision is reduced. Because of having no limit on the properties of the targets, the digital processing method can be applied to the measurement and the analysis of point targets or surface targets.

The invention discloses a foreign body detection system for an airfield runway. The system consists of a radar transmission and receiving antenna, a radar transceiver front-end, a cantilever, a rotating mechanism, a signal processor and a display control terminal, wherein the radar transmission and receiving antenna is connected with the radar transceiver front-end through a waveguide; the radar transceiver front-end is connected with the signal processor through the rotating mechanism; and the signal processor is connected with the display control terminal. For a linear frequency modulation continuous wave system, a high range resolution is obtained by wideband linear frequency modulation, and a synthetic aperture is constructed by the rotation of the antenna along a semicircular trajectory, so that a high azimuth resolution is obtained, the area of a ground clutter unit is reduced, and a small fragment target on the runway can be detected.

The present invention discloses an F-P and FBG fiber sensor demodulation system, and aims to provide an F-P/FBG demodulation system which is high in wavelength resolution, and enables the demodulation precision to be improved. The F-P/FBG fiber sensor demodulation system of the present invention is realized by the following technical scheme that under the control of an operation control unit, a tunable laser emits out a beam of C-wave band laser of a constant wavelength, by an optical amplifier SOA and/or an optical isolator, and by being divided equally via a beam splitter, the incident light respectively irradiates to n F-P/FBG sensors in one-to-one correspondence, the light reflected by the F-P/FBG sensors is coupled to n phototriodes in one-to-one correspondence by n optical couplers, the optical power is converted into an optical current, the optical current is converted into an optical voltage entering an analog-digital converter by a logarithmic amplifier, the wavelength-reflection optical voltage digital quantity acquired in a time-sharing manner is stored in a memorizer of the operation control unit, the operation control unit carries out the fast Fourier transform on a sampled spectrum, the types of the F-P/FBG sensors are distinguished, and a peak searching demodulation algorithm is carried out to obtain a gradient value containing the cavity length information.

The invention provides a turbulent boundary layer flow field velocity measurement method based on boundary tracing and belongs to the field of fluid computing. The method is used for acquiring velocity vector distribution of turbulent boundary layer fluid with hydrogen bubbles being tracing particles under a single-phase condition. The method comprises the steps that a hydrogen bubble image is acquired through a special experimental facility, the obtained experimental image is subjected to image input processing, processing through a histogram equalization algorithm, image feature extraction processing, FCM cluster partitioning processing, boundary recognition and tracking processing, local velocity distribution processing, velocity maximum value extraction processing, setting of an optimal detection window of a fast Fourier transformation cross-correlation algorithm, processing through the fast Fourier transformation cross-correlation algorithm, velocity vector distribution processingand other processing processes in sequence, and finally the velocity vector distribution is obtained. The method is simple, easy to implement, high in application value, high in operability and convenient to realize; and quantitative analysis is performed on a large-scale structure existing in a turbulent boundary layer, and the blank of quantitative research about a turbulent boundary layer quasi-order structure with the hydrogen bubbles being the tracing particles is filled up.

The invention discloses a signal processing method for a borborygmus signal monitoring system. According to the method, after borborygmus data are quantized into digital signals with sampling rate of Fs by a microphone, the digital signals are treated based on the self-adaptive filtering algorithm and sectioned according to window length, the signal frequency spectrum of each signal section is solved by means of the fast Fourier transform algorithm, the signal frequency spectra are firstly applied to intensity detection, then subjected to correlation-based detection and analysis with a median frequency spectrum model within the frequency band to be tested, and finally sent to a comparator to be compared with a reference value, only the signals with correlation coefficients high enough can be shown in a data window as borborygmus signals and presented by the output result 1, and 0 is output otherwise. On this basis, RIM, IMF and AMT are also provided to be used for evaluating the intestinal tract activity condition of a testee. The method is used for the wearable human body borborygmus signal monitoring system and can be implanted in equipment hardware or a monitoring server in hospital, and the position of a borborygmus of the testee can be marked according to borborygmus signals input into the system, so that technical support is provided for a doctor to offer reasonable postoperative rehabilitation nursing to abdominal surgery patients.

The invention discloses a 5G fire rescue method and a fire rescue helmet. With the 5G fire rescue method, the position and vital sign condition of trapped persons can be determined, the toxic and harmful gas of a disaster scene can be timely discovered, meanwhile, fire rescue information is provided for individual fire rescue workers wearing the fire rescue helmets through communication with a fire rescue command center, so that individual rescue of the fire rescue workers is avoided, then the safety of the workers is better protected, and the fire extinguishing and rescue efficiency is improved. With the fire rescue helmet, the vital sign data information of the trapped persons, disaster scene video information, smoke concentration information, temperature information and humidity information can be collected, the physical positions of the fire rescue workers can be located through GPS positioning chips, the information then is sent to the fire rescue command center, rescue auxiliaryinformation sent by the fire rescue command center can be projected to protective masks, so that the surrounding environment can be fully known, and therefore, while the rescue success rate is increased, the safety of the rescue workers can be better guaranteed.

The invention relates to a nondestructive testing method and device for basin type insulator curing degree of high-voltage switch equipment, wherein the nondestructive testing method comprises the following steps: transmitting an ultrasonic pulse to an insulator to be tested; obtaining an ultrasonic reflection signal at the lower bottom surface of the insulator to be tested; carrying out fast Fourier transform on the ultrasonic reflection signal, and calculating a power spectrum of the ultrasonic reflection signal; comparing the peak value of the power spectrum with a relational data base, thus obtaining the curing degree of the insulator to be tested; the relational data base is a corresponding relation of insulator curing degrees obtained by carrying out ultrasonic tests on insulator samples with different curing degrees and the power spectrum of the ultrasonic reflection signal at the lower bottom surface of the insulator. The method disclosed by the invention can effectively realize nondestructive testing on the overall curing degree of the basin type insulator.

The invention provides a method of identifying a faulted component (700) in an automotive system (100) including an internal combustion engine (110) managed by an Electronic Control Unit (450). The internal combustion engine (110) is operated according to a predefined detection routine (680). A noise signal (640) emitted by the activated internal combustion engine (110) is recorded in a data carrier (460) or memory system. The recorded noise signal (640) is analyzed by a signal treatment algorithm (650) to determine a plurality of vibration modes (660) of the automotive system (100) from the noise signal (640); the amplitude of the noise signal (640) is compared at each vibration mode (660) with an acceptable amplitude threshold (670). A faulted component (700) of the automotive system (100) is determined if the amplitude of the correspondent vibration mode is greater than the acceptable amplitude threshold.

The invention discloses a cutting chatter online monitoring method and a monitoring system. The monitoring method comprises the following steps: a, reading sensor data, computing a main axis passing rate fs=m/60; b, if the sensor data size is greater than or equal to N, performing Fourier transform and cleaning data, and returning to step a if the data size is less than N; c, when the chatter occurs, enabling the vibration energy to deviated from the integer multiple frequency of the main axis passing rate fs; d, computing a formula as shown in description; e, comparing the f0 with f; f, whenthe f0 is less than f, returning to step b, and ending; g, when the f0 is not less than f, sending a PLC signal to control a machine tool to halt; and h, ending. The monitoring system comprises the vibration sensor, a vibration signal collection card, a computer, an industrial bus interface and a numerical control system PLC. The Fourier transform is performed on a vibration signal so as to transform the vibration signal to a frequency domain, whether the chatter occurs is judged according to the deviation degree between the frequency located by the main vibration energy and the integral multiple frequency of the main axis passing rate, and the monitoring is performed at the same time.

Embodiments of the present invention disclose a heart rate acquiring method, device and system and a medium. The heart rate acquiring method includes: preprocessing pulse wave signals and accelerationsignals in all time periods; performing fast Fourier transform on the pulse wave signal in the current time period and the pulse wave signal preprocessed in the previous time period to obtain a pulsewave frequency domain set; performing fast Fourier transform on the acceleration signal in the current time period and the acceleration signal preprocessed in the previous time period to obtain an acceleration frequency domain set; and adjusting each frequency domain weight coefficient contained in a frequency domain weight coefficient set in the current time period in a preset LMS iteration wayaccording to the pulse wave frequency domain set, the acceleration frequency domain set, the frequency domain weight coefficient set in the current time period, a frequency domain weight coefficient set in the previous time period and an input power set in the previous time period to obtain a target frequency domain weight coefficient set, and performing fast Fourier transform on the target frequency domain weight coefficient set and the acceleration frequency domain set to obtain a heart rate signal without motion disturbances.

A wireless audio compression and decompression method based on time domain aliasing elimination comprises the steps of audio compression and audio decompression, wherein the audio compression step comprises windowed filtering, MDCT, quantification factor calculation, acoustic masking curve calculation, bit distribution, quantification calculation and bit stream generation which are carried out on input audio PCM data; the audio decompression step comprises code stream analysis, quantification factor analysis, acoustic masking curve calculation, bit distribution, inverse quantization, IMDCT, kayser window filtering and time domain aliasing. Wireless audio compression and decompression equipment further comprises an audio coder and an audio decoder.

The invention relates to a radar signal real-time detection method. The method is characterized by comparing an average amplitude of N sampling points before a certain moment with the amplitude of thesampling point at the moment, and if the amplitudes of the plurality of sampling points after starting of the certain moment are continuously a certain value higher than the average amplitude in a previous certain period of time, considering that a signal rising edge exists at the moment; otherwise, if the amplitudes of the plurality of continuous sampling points after a certain moment is startedare a certain value lower than the previous average amplitude, considering that a falling edge exists at the moment; and when both the falling edge and the rising edge exist, intercepting a signal part existing in data immediately. Whether a signal exists is detected in a mode of judging the rising edge and the falling edge in a time domain, and an effect of detecting the signal in real time under a passive condition can be achieved by setting reasonable parameters and thresholds.

The invention discloses a non-invasive blood pressure extraction method and system. The method comprises the steps of taking a single-cycle PPG signal formed by combining a plurality of cycle PPG signals as a research object, and carrying out the frequency decomposition of the single-cycle PPG signal through the fast Fourier transform extracted according to a time axis. The problem of researching the relationship between different PPG signals and blood pressure is converted into the problem of researching the relationship between the frequency spectrum amplitude and phase of PPG signal waveforms and the blood pressure, and the time interval between an ECG signal peak value and a point with the maximum gradient of a PPG signal rising edge is defined as the pulse wave arrival time PAT. The pulse wave arrival time PAT and the PPG signal frequency spectrum amplitude and phase can completely represent the body characteristics of a testee, the pulse wave arrival time PAT and the PPG signal frequency spectrum amplitude and phase serve as the input of a Stacking model to train the Stacking model, then the trained Stacking model is used for blood pressure prediction, accurate judgment of the blood pressure can be achieved, and the technical problems that an existing non-invasive blood pressure extraction method is large in error and low in accuracy are solved.

The invention discloses an in-vehicle network intrusion detection method and device based on fast Fourier transform, equipment and a storage medium. The method comprises the following steps: setting an alarm frequency threshold value and a maximum tolerance value; collecting kernel operation load data and bus load rate data in a unit time period; performing fast Fourier transform on the operation load data and the bus load rate data to obtain frequency domain features; the calculation result is compared with an alarm frequency threshold value, whether the calculation result is within the range of the alarm frequency threshold value or not is judged, and if yes, the step S20 is executed again; if not, recording the event as a suspicious event, and executing the next step; accumulating the occurrence time of the suspicious event, judging whether the occurrence time exceeds the maximum tolerance value, and if so, returning to execute the next step; if not, returning to execute S20; and the system gives an alarm and starts safety protection measures. According to the invention, intrusion detection can be carried out on the vehicle-mounted network, the health degree of the system is macroscopically identified, and intrusion detection with a low false alarm rate is realized.

The invention relates to the field of circuits, and discloses a three-phase current detection method, and the method comprises the following steps: acquiring bus voltage in a load starting process inreal time; performing fast Fourier transform on the bus voltage, and extracting a plurality of actual signal components with preset frequencies; and judging whether the three-phase current is open-phase or not according to the actual signal component. The invention also discloses a three-phase current detection circuit. The three-phase current detection method and the three-phase current detectioncircuit provided by the embodiment of the invention have the advantages of detecting whether the input power supply is open-phase before the load is started and preventing the load from running underthe open-phase power supply.