67results about How to "Improve frequency measurement accuracy" patented technology

The invention provides a method for improving the FID signal frequency measurement precision based on a quantized time delay method. The frequency measurement method uses the equal-precision frequency measurement principle and adopts a precision measurement method with 'rough measurement+fine measurement', the 'fine measurement' makes time compensation for the nonsynchronization of the standard clock edge and the measured signal edge by means of the quantized time delay method. The quantized time delay method adopts the method of digital time interpolation and overcomes the defect of complex hardware of a simulation interpolator, subsystems in a frequency measurement module are integrated in an FPGA, so that the circuit is easy realize and high in reliability, the frequency measurement resolution depends on the time-delay amount of a unit time-delay unit, the frequency measurement precision of a magnetometer is greatly improved to a large extent, and a corresponding device can be selected on the set object basis, and the improvement cost is reduced. The invention further includes a circuit for improving the FID signal frequency measurement precision based on the quantized time delay method.

The invention provides a two-stage-FFT-based digital broadband high-precision frequency measuring method and system. Zero-intermediate-frequency AD sampling is carried out on a signal or after sampling, down-conversion is carried out to form a zero-intermediate frequency signal and the processed signal is sent to a signal processing module; the signal processing module receives an original signal,the signal is divided into two paths, and one path of signal is used as original data for storage; the other part of data are used for FFT; modulo calculation is carried out on the result after FFT and over-threshold detection is carried out to detect an over-threshold signal; digital down conversion is carried out on the stored original signal by using the signal obtained by over-threshold detection as guidance, so that the processed signal is transformed to be at a zero-intermediate frequency position; filter extraction is carried out on the signal after frequency conversion; baseband dataafter filter extraction are sent to an upper computer; and the upper computer carries out large-point-number FFT on the baseband data to obtain a high-precision frequency result. Therefore, the high frequency measurement accuracy is kept at a high sampling rate under the circumstance of limited hardware resources.

The characteristics of the invention are as follows. The homotactic treatment is carried out for the signal fx to be measured and the standard frequency signal fo. The pulse sense signal with f phases being accord with each other is generated by the phase comparison circuit to control the staring and closing the strobe of the counter x and fo. The Nx and No multiple periodic quantity of fx and foare recorded in the opening time of the strobe of the counter x. Further, the fx canbe calculated from the formula fx=(Nx / No)fo. Based no the said method, the frequency meter designed is composed of the ordered circuit, the phase comparison circuit, the conditioning circuit, and the single chip etc. The invention possesses the features of good consistency of the phase coincidence signal, suitablefor wide frequency range and high resolution of the frequency to be measured.

A method of manufacturing a piezoelectric resonator includes forming first electrodes larger than vibrating electrodes in an area D1 including the vibrating electrodes on obverse and reverse surfaces of a piezoelectric substrate, and measuring the resonant frequency fr1 of a resonator including the first electrodes. The thickness of a metallic thin film required for frequency adjustment is determined based on the measured resonant frequency. Then, second electrodes formed of the metallic thin film having the determined thickness are formed in an area D2 including at least the vibrating electrodes of the piezoelectric substrate. By removing unnecessary portions of the first and second electrodes, a pattern of the resulting vibrating electrodes is formed. Thus, high-accuracy frequency adjustment can be achieved without the need for complicated positioning.

The invention discloses a multi-channel undersampling frequency measurement method for wide bandwidth frequency hopping narrow band signals. A multi-channel cooperative frequency measurement method isadopted, and measurement on the frequency of the wide bandwidth frequency hopping narrow band signals under an undersampling condition can be realized. The multi-channel undersampling frequency measurement method comprises steps: firstly, multiple signal channels with frequency bands mutually overlapped and capable of meeting a signal frequency hopping range and frequency ambiguity resolution condition are built; signals in each channel are then subjected to over threshold detection, and channels with over threshold are subjected to signal frequency measurement; and finally, an over thresholddetection result and a frequency measurement result are analyzed integrally, frequency ambiguity resolution processing under the undersampling condition is completed, and the signal frequency is obtained. Multiple channels are used for frequency measurement at the same time, measurement on the frequency of the wide bandwidth frequency hopping narrow band signals under the undersampling conditioncan be realized,and in comparison with a frequency measurement method at a Nyquist sampling rate, the data rate is reduced.

The invention discloses a WIFI-based wireless vibrating wire strain collecting device and an implementation method thereof that are applied to data acquisition of a bridge monitoring system. The WIFI-based wireless vibrating wire strain collecting device is composed of a controller, a power supply module, a high-voltage boosting circuit, a high voltage switch, a signal conditioning circuit, and aWIFI wireless module. The controller receives a data acquisition instruction from an upper computer through the WIFI wireless module and outputs a PWM signal to control the high-voltage boosting circuit to generate a high voltage; the high-voltage boosting circuit loads high voltage excitation to a string wire sensor by the high voltage switch; the string wire sensor carries out vibration under the high voltage excitation and a the frequency signal related with the string wire tension is outputted to the signal conditioning circuit for adjustment; and then the controller carries out capturingcounting on the adjusted frequency wave to obtain a frequency value. Therefore, the frequency measurement accuracy of the strain of the bridge structure is improved effectively; and the strain condition of the bridge structure can be monitored in real time.

The invention discloses an instantaneous frequency measurement method based on an FPGA and a digital receiver thereof. The method comprises the following steps of: delaying the original data stream byb clock cycles, forming two real sequences with the current data stream, wherein the two real sequences are respectively used as a real part and an imaginary part to obtain complex original data stream signals; inputting the plurality of original data stream signals into an FFT (Fast Fourier Transform) operation module according to the bit width, performing butterfly operation for the output of the FFT module operation module, and inputting the output into a decomposition circuit to obtain frequency spectrums corresponding to two real sequences respectively; calculating a noise threshold according to the two complex frequency spectrums; according to the noise threshold and a set signal-to-noise ratio margin, performing searching by adopting an extreme value to obtain a coarse frequency measurement signal; demodulating and outputting the pulse synchronous signal according to the noise threshold, the signal-to-noise ratio margin and the coarse frequency measurement signal; obtaining a real part value and an imaginary part value corresponding to the coarse frequency measurement signal according to the coarse frequency measurement signal and the complex frequency spectrums; measuringthe frequency by adopting a phase difference method; and finally, fusing data to output a frequency measurement result. The digital receiver includes the FPGA implementation that integrates the above-described method.

The invention relates to a frequency measuring method and a measuring system thereof; the frequency measuring method comprises the steps that N clock signals are acquired, and test signals are sampledat the same time, wherein the frequency of the N clock signals is the same, and the phases are different; N counting values are obtained according to the test signals which are obtained through sampling and the N clock signals; and the frequency of the test signals is obtained according to the frequency of the N clock signals and the N counting values. According to the frequency measuring method,the tested signals are sampled at the same time by adopting a set of clock signals with the same frequency and different phases, so that the sampling time is shortened, the sampling precision is improved, and the measurement precision of the frequency is improved.

Disclosed is a power system frequency measuring method and device. The method includes the steps of measuring frequency of an input signal to obtain a reference frequency; subjecting the input signal to scaled operation and integral operation to obtain a scaled operation output signal and an integral operation output signal; subjecting the scaled operation output signal to amplitude detection to obtain a first amplitude detection signal, subjecting the integral operation output signal to amplitude detection to obtain a second amplitude detection signal; determining a ratio of the first amplitude detection signal to the second amplitude detection signal, and acquiring a frequency measured value of the input signal according to a product of the ratio and the reference frequency. The power system frequency measuring method and device has the advantages that low frequencies can be measured highly precisely, noise resistance in low frequency measurement is good, and the method and the device have important uses and reference value in power scientific research, measurement of power system frequency and calibration and development of power instruments.

An excitation method of a vibrating wire sensor mainly comprises the following operating steps: performing single excitation for exciting coils of the vibrating wire sensor by an intermittent excitation mode to obtain a resonant frequency measured value f1 with low precision; calculating statistical characteristics of vibration signals during various periods, and inspecting the statistical characteristics; exciting the exciting coils of the vibrating wire sensor by adopting a signal with the frequency being f1 and stopping excitation after vibrating wire resonance, or performing frequency-sweep excitation at the position of a narrower bandwidth near the frequency f1; and finally processing signals from vibration pickup coils, and measuring the signal frequency to obtain a measured value f2as an exact value of vibrating wire resonance frequency. The excitation method of the vibrating wire sensor has the advantages of fast starting of vibration, large amplitude, shortened detection time, improved working efficiency, improved excitation reliability and improved measuring precision. The excitation method of the vibrating wire sensor is applicable to observation on stress strain, deformation, seepage, liquid level, temperature and the like of the projects such as reservoir dams, bridges, foundation pits and the like.