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

The invention relates to the technical field of fiber sensing, and especially to a pre-pumped pulse and Gray code based BOTDA instrument. The BOTDA instrument comprises a narrow-linewidth semiconductor sensor, a coupler, a first erbium doped fiber amplifier, a first polarization controller, a single sideband modulator, a microwave source, an optical isolator, a sensing fiber, an optical annular device, a second erbium doped fiber amplifier, a polarization scrambler, an electro-optical intensity modulator, a second polarization controller, an arbitrary waveform generator, an optical filter, a photoelectric detector and a signal collecting and processing system. On the premise that the high spatial resolution of a BOTDA system is maintained, the BOTDA instrument ensures the sensing distance and the measuring precision of the system, and improves the sensing performance of the system.

The invention discloses an equal-precision frequency testing system and method based on an FPGA. According to the system, frequency demultiplication is carried out on outer standard clock signals, a preset gate signal is obtained, and then an actual gate signal is obtained. The rising edge of an outer signal to be tested and the rising edge of the standard clock signal are counted so that the periodicity of the outer signal to be tested and the standard clock signal in the actual gate signal can be obtained. The frequency of the signal to be tested is obtained according to the obtained periodicity and the frequency of the standard clock signal, and finally the frequency of the signal to be tested is sent to a nixie tube to be displayed. Through the method, high frequency measurement precision can be obtained, and the measurement precision of the frequency is almost equal.

The invention discloses a device and method for realizing Doppler frequency shift (DFS) measurement based on a dual polarization modulator, relating to the fields of microwave technology and optical communication technology, and mainly applied to the measurement of DFS. The device is as shown in attached drawings, and comprises a light source (LD), a transmitted signal source, an echo signal source, a 90-degree phase shifter, a dual polarization modulator (DPol-MZM), an optical amplifier (EDFA), an optical filter (OBPF), a polarization beam splitter (PBS), a photoelectric detector (PD) and a hybrid coupler. According to the method disclosed by the invention, the echo signal is down-converted to a low-frequency electric signal based on the DPol-MZM, and the size and direction of the Doppler frequency shift can be simultaneously estimated in combination with the hybrid coupler; and when the Doppler frequency shift is positive, only the positive port of the hybrid coupler has output signals, and when the Doppler frequency shift is negative, only the negative port of the hybrid coupler has output signals. The method disclosed by the invention has the advantages of wide carrier frequency tuning range, high frequency measuring accuracy and the like.

The invention discloses an apparatus and method for realizing instantaneous microwave frequency measurement by dual polarization modulators. The invention relates to the technical fields of microwave and optical communication, and is mainly used for the measurement of microwave signal frequency. The method, as shown in the drawing, includes a light source, a signal source, the dual polarization modulators, a single-mode fiber, a coupler, a polarization controller, a polarizer, and a photoelectric detector, and the microwave signals of the unknown frequency generated by the signal source are modulated by the dual polarization modulators to obtain polarization multiplexing signals. Through the fiber dispersion, the polarization multiplexing signals are divided into two paths, one is maintained at the same polarization state, the other one is converted into a linear polarization signal through the polarization controller and the polarizer. The photoelectric detector detects the two signals, measures the power values and establishes the power comparison functions. According to the correspondence relation, the measured frequency can be estimated. By changing the polarization state of one signal, the measurement scope can be adjusted, the realization is simple, the resolution is high, and the measurement error is less.

A low-velocity pulse period collecting method based on anti-interference low-pass filtering comprises a collection process and an operation process. At least two counting units are adopted in the collection process. The collection process comprises the steps that collected signals are input until two counting units with the legal ARS continuously appear, T of one counting unit is recorded as T1,T of the other counting unit is recorded as T2, and the measuring frequency F0 of the collected signals is worked out according to T1 and T2; the collection process is repeatedly carried out many times. The operation process comprises the step that the algorithm filtering is carried out on F0 obtained from many times of carrying out collecting processes to obtain the filtering frequency of the collected signals. The invention further discloses a low-velocity pulse period collecting device based on the anti-interference low-pass filtering. By means of the low-velocity pulse period collecting method and device based on the anti-interference low-pass filtering, the interference to a counter from the high-frequency interference pulse is effectively resisted through a low-pass filtering method, and frequency measuring precision is improved.

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 discloses a test circuit of acoustic surface wave resonator type wireless sensor sensing echo frequency. The test circuit of the acoustic surface wave resonator type wireless sensor sensing echo frequency is characterized in that high order frequency doubling is performed on an echo signal after down conversion, and then the sensing echo frequency is detected by using a Fourier transformation digital processing method. The simplest test method of the test circuit of the acoustic surface wave resonator type wireless sensor sensing echo frequency is to achieve the signal high order frequency doubling by using a signal saturation amplification circuit before sampling, distorting a signal and generating high order harmonic. The test circuit of the acoustic surface wave resonator type wireless sensor sensing echo frequency has the advantage of being capable of greatly improving DFT (discrete Fourier transformation) frequency measurement accuracy on the premise of not prolonging duration of signal sampling time.

The invention provides a high-precision instantaneous frequency measurement method and device based on channelization. The method comprises the following steps: carrying out digital channelization processing on an input radar signal: carrying out extraction and filtering on the input radar signal through a multi-phase band-pass filter group, carrying out fast Fourier transform (FFT), and then, outputting sample points of multiple channels to realize digital channelization processing; carrying out instantaneous frequency measurement on the plurality of paths of signals obtained after digital channelization processing through a phase difference method and an interpolation method respectively; and carrying out ambiguity-resolving processing on the frequency obtained through the phase difference method according to the frequency obtained through the interpolation method to enable the original fuzzy frequency to be corrected into the correct frequency. The method and device can still have higher frequency measurement precision when the digital channelization does not have oversampling.

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 invention discloses an accurate frequency measurement method of a high-dynamic weak MPSK signal, and aims to provide an accurate frequency measurement method capable of adapting to a high-dynamicweak signal complex scene. The method is realized through the following technical scheme: a coarse frequency measurement module directly performs fast Fourier transform, incoherent integration, spectrum smoothing and frequency coarse calculation on a received signal to obtain a carrier Doppler frequency shift coarse value; in a fine frequency measurement state, the Doppler pre-compensation moduleperforms Doppler pre-compensation on the received signal by adopting the carrier Doppler frequency shift rough value; the change rate pre-compensation module performs change rate pre-compensation on the sampling data according to the carrier Doppler change rate subdivision value; the multiple frequency measurement processing branches process data output by the grouping average module in parallel,the frequency fine calculation module estimates the overturning position of a modulation symbol in a received signal, the carrier Doppler shift and the carrier Doppler change rate of the received signal at the output moment are obtained through correction, and accurate frequency measurement of the high-dynamic weak MPSK signal is completed.

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.

The invention relates to a rapid high precision frequency measuring realization method by applying an FPGA chip, belonging to the digital signal processing field. According to the method, an FFT module, a Fife module and an ROM module are added into the FPGA chip, an input signal is divided into three signals, wherein, two signals are subjected to frequency shift, the other signal is not subjected to frequency shift, on a basis of Rife, a real part absolute value and an imaginary part absolute value of an FFT operation result are compared to determine a frequency spectrum maximum value, threefrequency measuring results are obtained respectively, and a maximum value is selected as a final frequency measured value. According to the method, frequency measuring precision of a fixed-length receiving signal is raised, a processing speed is accelerated, and a real-time property of a system is raised.

The invention discloses an optimized sweep frequency excitation method for a vibrating wire collector. The optimized sweep frequency excitation method comprises: a first step in which in a pre-sweep frequency excitation stage, a pre-sweep frequency excitation range and an impulse sequence incremental step length are set, then a pre-sweep frequency excitation impulse sequence is sent, and vibrationpickup and frequency measurement are performed, whether a vibrating wire is reliably excited is checked according to frequency measurement data, if so, a sensor resonant frequency is acquired, and asecond step is entered, and if not, error processing is performed; a second step in which in a complex sweep frequency excitation stage, a complex sweep frequency excitation range and the impulse sequence incremental step length are set according to the frequency measurement data of the pre-sweep frequency excitation, vibration pickup and frequency measurement are performed after a complex sweep frequency excitation impulse sequence is sent, whether the vibrating wire is reliably excited is checked according to the frequency measurement data, if so, a vibration measurement frequency is returned, and if not, error processing is performed. The optimized sweep frequency excitation method of the invention is provided based on a feedback strategy, can realize self-adaptive sweep frequency excitation under the condition that working parameters of a sensor are unknown, and is reliable and accurate in result.

The present invention adopts piezoelectric gene diagnosis chip and frequency detection instrument and utilizes multiple PCR technique to make temp. circulation of hydridization-extension-denaturation to amplify, target gene, monitor and obtain the linear relationship of frequency change and target gene concentration, then uses external standard curve to make quantitative analysis. Said apparatus comprises shell body, power supply and its connected circuit, and main body module, analysis, software, sample preparation module, positioning liquid flow module and piezoelectric gene diagnosis chip detection module. Said invention is suitable for clinical diagnosis and molecular mechanism research, monitoring epidemic disease and infections disease spreading and harmful microbial genesis and diffusion.

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 an instantaneous frequency measurement apparatus and measurement method, and belongs to the technical field of instantaneous frequency measurement. The apparatus provided by the invention comprises a radio-frequency processing unit, a sampling and frequency mixing unit, an intermediate frequency processing unit, a digital channel processing unit and an operation unit. The real-time monitoring bandwidth implemented by the instantaneous frequency measurement apparatus and measurement method can be up to 26.5 GHz; real-time spectral analysis and instantaneous frequency demodulation are combined, so an instantaneous frequency test for multiple domains and multiple frequency bands is implemented, the requirements of the instantaneous frequency test on large monitoring bandwidth and high precision can be met, and the application range is wider; the implemented dynamic range and sensitivity are higher; with the intermediate frequency gain adaptive adjustment, the instantaneous frequency measurement requirements of different input power signals can be met, and the frequency measurement precision can also be improved; and the implementation scheme is concise, the circuit composition is simple, the technology is mature and high and the implementation cost is low, so the instantaneous frequency measurement apparatus and measurement method have the advantage of verygood cost performance.

The invention discloses a frequency measuring machine and a method for measuring the frequency of a signal, wherein the frequency measuring machine is used for carrying out frequency division processing on an input radio-frequency signal through an arranged frequency divider; thus, a frequency-divided signal with lower frequency is obtained; therefore, an analog-digital collection module is enabled to be capable of collecting the frequency-divided signal; thus, the frequency measuring machine is enabled to be capable of being applied to the frequency measurement of a radio-frequency signal with higher frequency; in addition, in a frequency calculation module, the further digital detection and shaping filtering treatment is carried out on a complex signal through a digital detection unit; the pulse edge of an obtained detected signal is enabled to be steeper; the recognition and the processing of a sampling unit on each effective pulse are convenient; the frequency measurement precision of the frequency measuring mechanism is increased.

The invention relates to a method for debugging a high-stability crystal oscillator. The method is characterized in that a high-accuracy frequency measuring device formed by connecting a Beidou satellite receiver, a rubydium atomic clock, a frequency counter and a control computer is used for debugging a crystal oscillator; high-accuracy 1PPS signals demodulated by the Beidou satellite receiver are output to a 1PPS IN port of the rubydium atomic clock by virtue of a 1PPS signal port and are used for taming the rubydium atomic clock; 10 MHZ signals output by the 10 MHZ output end of the rubydium atomic clock are transmitted to an external reference signal input port REF IN of the frequency counter; the control computer is connected to a GPIB interface of the frequency counter by virtue of a USB (Universal Serial Bus) GPIB (General Purpose Interface Bus) forwarding wire; the signal output end of the tested oscillator is connected to the frequency counter. By utilizing high-stability frequency reference, the frequency measuring precision is greatly improved; almost an hour of preheating and stabilizing during starting the frequency counter for each time is omitted; the error and data omission caused by artificially estimating and recording data when operators read frequently-flashed digital tubes can be reduced; all the data are recorded in a file for saving.

The present invention relates to a method for accurately measuring the frequency of a pulse signal, and discloses a method and a device for accurately measuring the multi-pulse frequency of a single carrier frequency pulse signal. The method comprises the following steps of: Step 1, orthogonally transforming real-number single carrier frequency pulse string signal samples that are received, and processing the first complex-number pulse signal sample by using a Kay algorithm to obtain a frequency iteration initial value fsp; Step 2, carrying out Fourier transform of each complex-number pulse signal sample to obtain the phase difference of peak points after Fourier transform of each complex-number pulse signal sample; Step 3, calculating the time difference between starting sampling points of Fourier transform of two adjacent complex-number pulse signal samples; Step 4, performing iterative calculation to get f(2), f(3), ..., f(K), wherein f(K) is the accurate measurement value of the multi-pulse frequency of the real-number single carrier frequency pulse string signal samples.

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.

The invention aims to provide a ship gas turbine power turbine rotating speed signal frequency measuring method, which comprises the following steps of: receiving an engine rotating speed measured signal, filtering the signal after the measured signal is input, comparing the filtered signal with a set threshold voltage through a voltage comparator, outputting to obtain a square wave signal with the same frequency, sending the square wave signal to an FPGA through an isolation circuit, and allowing the FPGA to count the input square wave signal in unit time, and with the known unit time, calculating the frequency of the measured signal, wherein the calculation formula is f = D * F / N, D is the known set unit number, F is the clock frequency of the FPGA, and N is the number of sampling signals. The method overcomes the defects of an existing device for measuring the rotating speed signal frequency of the power turbine of the ship gas turbine, and is high in frequency measurement precision and wide in frequency measurement range.

The invention discloses a digital reconfigurable channelized single-bit receiver and an implementation method. The receiver is composed of a 38.4 GHz sampling ultra-wideband single-bit receiver and a reconfigurable digital channelized system. The 38.4 GHz sampling ultra-wideband single-bit receiver comprises a 38.4 GHz ultra high speed single-bit ADC and an FPGA chip; the reconfigurable digital channelization system is embedded in an FPGA chip and comprises a system state machine, a rough frequency measurement module and an accurate frequency measurement module, the rough frequency measurement module and the accurate frequency measurement module multiplex a frequency measurement algorithm module, and the accurate frequency measurement module further comprises a single-bit digital frequency mixing module and a single-bit digital filtering module. Through the reconfigurable digital channelization technology, the single-bit receiver has the advantages of high frequency measurement precision, high pulse width detection precision and the like, and is easy to realize by an FPGA and high in universality.

The invention provides a real-time and high-precision coherent pulse signal frequency measurement method, and belongs to the technical field of detection and reconnaissance. Single pulse frequency measurement is performed on a single pulse signal by utilizing a discrete frequency spectrum phase difference correction method firstly, and if frequency measurement precision reaches a certain range, fine correction is performed step by step by fully utilizing multiple pieces of coherent pulse information so that frequency measurement precision is enhanced; and if frequency does not reach the preset range, single pulse frequency measurement is performed on multiple single pulses respectively, frequency measurement results are accumulated and averaged and frequency is enabled to reach the preset range, and then fine correction is performed step by step by utilizing multiple pieces of coherent pulse information. Compared with existing methods, the method has advantages of high frequency measurement precision, high anti-noise capability, moderate computation amount and multi-carrier frequency signal frequency measurement capability.

The invention discloses a high-precision measurement system for a DS / FH spread spectrum signal carrier frequency. The measurement system comprises a spreading and hopping pattern module, a de-spreading and de-hopping module, a sampling cache module, a two-dimensional slotting module, a compensation correction module, an integral accumulation module, a peak value search module and a frequency resolving module. The de-spreading and de-hopping module carries out pseudo code de-spreading and frequency de-hopping on the received signal according to the real-time direct spread pseudo code and the frequency hopping frequency; the two-dimensional slotting module divides the movement speed and the acceleration into a plurality of two-dimensional search sub-slots according to the carrier Doppler frequency shift and the carrier Doppler change rate range in the captured information; the compensation and correction module is used for carrying out carrier frequency compensation and correction on the sampling data read by the sampling cache module in an inverted sequence according to the hopping frequency output by the spread hopping pattern module and the sub-slot information output by the two-dimensional slotting module; and the frequency resolving module is used for resolving the carrier Doppler frequency shift and the carrier Doppler change rate of the received signal at the output moment by adopting a time correction technology according to the integral peak value sub-slot information.