19results about "Heterodyning/beat-frequency comparison" patented technology

The invention relates to the field of signal frequency detection in microwave photonics, and discloses a broadband instantaneous frequency measurement receiving system based on Brillouin spectrum compression, which utilizes a dual-tone pump optical carrier signal carried on an intensity modulator and an optical filter to generate a single Brillouin pump source regulated and controlled by unknown radio frequency. A stimulated Brillouin structure narrowed by an optical fiber ring cavity and a single-pumping reference source subjected to phase shift beat frequency, a signal in a 45GHz range can be compressed to a bandwidth of 2.5 MHz, and meanwhile, an original signal can be subjected to optical domain down-conversion processing by a reference source signal, so that a low-frequency signal easy to process electronically is obtained; besides, a double-fiber annular cavity design is adopted, the line width of the Brillouin resonant laser is further compressed through mode matching of interference of light waves in the cavity, test precision reduction caused by frequency spectrum compression is made up, the resolution ratio can reach + / -2.2 MHz, and finally the Brillouin broadband instantaneous frequency measurement receiving technology is achieved.

By using a detector and voltmeter that do not require high-speed trigger operation, the present invention provides a phase characteristic measurement device that avoids the need for large-scale equipment used for phase measurement and enables relatively inexpensive phase measurement. [Solution] The system includes a first detector 11 that receives and detects three patterns of three-tone signals: a first three-tone signal obtained by combining three waves with angular frequencies ω1, ω2, and ω3 (where ω2-ω1=ω3-ω2=Δω), a second three-tone signal in which each tone has a phase offset, and a third three-tone signal having a different phase offset from the second three-tone signal; a BPF 12 that passes only the beat component of the signal output from the first detector, where the angular frequency difference Δω is between adjacent waves of the three-tone signals; a second detector 13 that detects the power of the beat component that has passed through the BPF 12; a voltmeter 14 that measures the voltage of the signal output from the second detector; and a phase calculator 15 that calculates the phase based on the measured voltage values ​​of the three patterns.

Disclosed is a photon technology-based flexible-tunable microwave signal frequency measurement device and method thereof; a sweeping local oscillator is modulated onto a first optical comb line of an optical frequency comb to obtain a scanning optical sideband; meanwhile, a tunable optical filter is used to select a specific optical comb line from other optical comb lines of the optical frequency comb, and a phase modulator is used to modulate a to-be-measured signal onto the selected optical comb line to obtain a to-be-measured signal optical sideband; after the scanning optical sideband and the to-be-measured signal optical sideband are balanced and detected, an electrical signal output by the balanced detection is filtered by a low-pass filter; and a signal acquisition and processing unit performs frequency-time mapping on the filtered electrical signal to obtain frequency information of the to-be-measured signal. The device and method thereof can realize flexible-tunable microwave signal frequency measurement, and can support flexible use of various frequency measurement tactics.

This application discloses a signal detection system, comprising: a frequency estimation device and a signal detection device; the output terminal of the frequency estimation device is connected to the input terminal of the signal detection device. The system can generate a chaotic photoelectric oscillator radio frequency signal by estimating the frequency of the incident signal and the optical carrier signal based on environmental conditions. Then, the chaotic photoelectric oscillator radio frequency signal is used to detect the target signal (i.e., a weak microwave photon signal). Therefore, the system can achieve the reception of weak signals within a large dynamic bandwidth, overcoming the shortcomings of traditional signal detection methods, such as narrow operating bandwidth and low detection sensitivity.

The present application relates to the technical fields of optoelectronic device measurement and microwave photonics, and discloses a method and device for measuring the frequency response of a photodetector based on an optical LFM signal, comprising an optical linear frequency modulation (LFM) signal generation module, an optical coupler, a time-domain signal acquisition module and a low-frequency detection module; the optical LFM signal generation module is used to generate an optical LFM signal; the optical coupler is used to divide the optical LFM signal into two paths, i.e., an upper path and a lower path; the time-domain signal acquisition module is used to extract beat frequency information of a carrier and a swept first-order sideband input into a photodetector to be measured; and the low-frequency detection module is used to extract low-frequency information generated by the beat frequency of the original first-order sideband and the first-order sideband after time delay. The method and device for measuring the frequency response of a photodetector based on an optical LFM signal realize one shot detection by using an optical LFM signal, so the measurement speed is extremely fast, and the measurement efficiency can be greatly improved; the present application has a simple structure, can be built by using existing shelf products, and has a low implementation cost.

A first detector that receives and detects 3-tone signals of three patterns of a first 3-tone signal obtained by combining three waves of angular frequencies ω1, ω2, and ω3 (here, ω2−ω1=ω3−ω2=Δω is established), a second 3-tone signal in which each tone has a phase offset, and a third 3-tone signal having a phase offset different from the phase offset of the second 3-tone signal, a BPF that allows only a beat component of an angular frequency difference Δω between adjacent waves of the 3-tone signals among signals output from the first detector to pass, a second detector that detects power of the beat component that has passed through the BPF, a voltmeter that measures a voltage of a signal output from the second detector, and a phase calculator that calculates a phase based on the measured voltage values of the three patterns.

The present application relates to a primary frequency modulation adaptive analysis test system for a coal-fired unit, characterized in that it is built based on a DCS system and includes: an on / off control module, an acquisition module, a logic operation module and a visual monitoring module, wherein the on / off control module is used to collect parameter information of the coal-fired unit; the logic operation module is used to identify the operation mode of the coal-fired unit according to the parameter information, and to perform a primary frequency modulation adaptive analysis test, and automatically generate frequency modulation performance evaluation indicators; the visual monitoring module is used to display the frequency modulation performance evaluation indicators under each operation mode in a visual interface. Through the present application, the problems of low efficiency, high human resource consumption and great interference to the safe operation of the unit in the existing primary frequency modulation test method are solved, the degree of automation of the test is improved, the test time is reduced, and the safe and stable operation of the unit during the test is guaranteed.

The accessory device has a test port, an instrument port connected to a measuring instrument having an operating bandwidth, and one or more configurable signal paths connectable between the test port and the instrument port for converting signals from the test port having a first frequency range to signals having a second frequency range different from the first frequency range. The test and measurement system includes a test and measurement instrument having an operating bandwidth and an accessory device. The accessory device has a first instrument port for connecting the accessory device to the test and measurement instrument, a test port for connecting the accessory device to a device under test, and one or more configurable signal paths connectable between the test port and the instrument port for downconverting signals from the test port having the first frequency range to signals having a second frequency range lower than the first frequency range.

This invention provides a frequency following sampling and dual-frequency calibration method and system for synchronization inspection devices, relating to the field of power system signal processing technology. The method includes: calculating the frequency of the rising edge of the system-side voltage signal and the rising edge of the voltage signal to be paralleled on the target side to generate a stable frequency on the system side and a stable frequency on the target side; determining the validity and balance of the stable frequencies on the system side and the target side, using a frequency following strategy to determine the effective following frequency and outputting the frequency balance result; dynamically selecting the signal sampling mode by calling a timer reconfiguration function, synchronously sampling the system-side voltage signal and the voltage signal to be paralleled on the target side, and performing a Fourier transform based on the frequency balance result to generate the voltage amplitude on the system side and the voltage amplitude on the target side; and calibrating and correcting the voltage amplitude on the system side and the voltage amplitude on the target side using a linear interpolation algorithm to generate a standard voltage amplitude on the system side and the standard voltage amplitude on the target side, thereby eliminating spectral leakage and improving the measurement accuracy of the voltage amplitude.

The invention discloses a method and device for constructing a 425nm wavelength reference based on induced fluorescence effect, which relates to the field of transition frequency measurement. The device includes a continuously tunable laser, an atomic furnace, a chromium atomic beam, an optical frequency comb, a frequency doubling optical path, a polarization-maintaining optical fiber beam splitter, a polarization-maintaining optical fiber beam combiner, a beat frequency detection optical path, a photoelectric receiver and a frequency counter; the output end of the continuously tunable laser is connected to the input end of the polarization-maintaining optical fiber beam splitter; the output end of the optical frequency comb is connected to the frequency doubling optical path; the frequency doubling optical path and the first output end of the polarization-maintaining optical fiber beam splitter are respectively connected to the input end of the optical fiber beam combiner; the chromium atomic beam is ejected through the atomic furnace and acts on the second output end of the polarization-maintaining optical fiber beam splitter; the output end of the polarization-maintaining optical fiber beam combiner is connected to the input end of the beat frequency detection optical path; the output end of the beat frequency detection optical path is connected to the input end of the frequency counter through a photoelectric receiver. This method fills the gap in the wavelength reference of the blue-violet light band.

The invention provides an instantaneous frequency measurement system and method based on a phase modulator, and the system is connected with a vector network analyzer, and comprises a light source module which is used for providing an optical carrier; the modulation module is used for modulating the fed radio frequency microwave signal onto an optical carrier to obtain an optical modulation signal; the wavelength division multiplexing module is used for separating positive and negative first-order sidebands of the optical modulation signal into a first optical modulation signal and a second optical modulation signal; the detection module is used for respectively converting the first light modulation signal and the second light modulation signal into a first electric signal and a second electric signal; the coupling module is used for combining the first electric signal and the second electric signal to form an output electric signal; wherein the vector network analyzer is respectively connected with the modulation module and the coupling module, and the vector network analyzer receives the output electric signal, obtains a power spectrum of the output electric signal and reversely deduces instantaneous frequency information of the radio frequency microwave signal. The system is high in integration level and strong in anti-electromagnetic interference capability, and is suitable for various scenes.

The present application relates to a frequency stability measurement method and system in the field of electronic technology. The method includes: respectively performing isolation amplification and frequency division processing on the acquired reference frequency signal and the frequency signal to be measured; doubling the frequency division signal of the reference frequency signal as the DDS clock source, generating a DDS frequency control word by roughly measuring the frequency of the frequency signal to be measured, thereby generating two orthogonal DDS signals, taking the frequency division result of the frequency signal to be measured and the two orthogonal DDS signals as the inputs of quadrature double mixing for quadrature double mixing processing, performing low-pass filtering, AD sampling, phase detection, phase unwrapping processing, and filtering on the double mixing processing result, and then calculating the phase difference between the measured frequency signal and the new reference frequency signal, and calculating the frequency stability according to the phase difference. This method can achieve the measurement of the frequency stability of the reference frequency signal and the frequency signal to be measured for both homologous and non-homologous cases, and at the same time, the measurement of the frequency stability of heterogenous frequency signals is also relatively accurate.

The present invention provides a terahertz wave heterodyne detector with ultra-high sensitivity. A heavy metal electrode pair grown on a beat frequency laser absorption layer absorbs the energy of the beat frequency laser, while an antiferromagnetic layer absorbs the resonant terahertz wave, and the spin-to-charge current conversion in the heavy metal electrode pair is realized by the spin-orbit coupling effect, so that mixing occurs in the heavy metal electrode pair, and the frequency conversion of the terahertz wave frequency to the frequency of a conventional electronics radio frequency band that is easy to measure is realized. Finally, the heterodyne signal is obtained through analysis by devices such as a spectrum analyzer. This terahertz wave heterodyne detector with ultra-high sensitivity utilizes the property of the antiferromagnetic oscillator frequency in the terahertz band and combines the heterodyne method, having advantages such as good frequency selectivity and high sensitivity.

A non-contact method is presented for measuring vibration on a surface of an object. The method includes: projecting light from one or more light sources towards an area of interest on a surface of an object; detecting the light diffusely reflected by the surface of the object using one or more detectors; determining a change in position of the reflected light detected by the detector over time; for the at least one point on the surface of the object, calculating a series of measurements of vertical displacement of the surface over a period of time from the change in position of the reflected light and using triangulation; and determining frequency of a disturbance of the surface at the at least one point on the surface and an amplitude of the disturbance using the series of measurements of vertical displacement.

The present invention discloses a method, module and device for measuring the source difference of a frequency signal. The method includes that after the frequency signal to be measured and a reference signal are mixed, a difference frequency signal of the frequency difference between the two signals is obtained and then input into a phase-locked loop, and the phase-locked loop performs phase locking on the difference frequency signal; the phase-locked loop provides a master clock based on the reference signal, and after the phase locking, an apparent frequency difference value is obtained, and then the corresponding apparent source difference is obtained through calculation, and the sum of the apparent source difference and the actual source difference of the reference signal is the actual source difference of the frequency signal to be measured obtained by measurement. The present invention can provide a general measurement means for signals in different frequency bands, and can ensure high accuracy of the source difference measurement result, and has the advantage of realizing low cost.

The invention provides a device response measurement system and method. According to the device response measurement system and method, outputs of pulse light sources with two different repetition frequencies are input into a photoelectric conversion device and an electro-optical frequency mixing device respectively, and electric signals generated by the photoelectric conversion device are transmitted through a radio frequency channel and then are loaded to the electro-optical frequency mixing device. Through multi-heterodyne beat frequency sampling, the sampling difficulty of a broadband signal is obviously reduced, so that response measurement of a broadband device is realized. The method does not need a complex microwave up-down conversion system, and has the advantages of low system complexity, low cost and wide coverage frequency range.

The invention belongs to the technical field of microwave information measurement, and discloses a microwave multi-information measurement device based on multi-local oscillator microwaves, which comprises a detection laser module, a coupling laser module, a signal detection module, a local oscillator signal generation module and a signal processing module, the detection laser module is used for outputting first detection light, second detection light, first reference light and second reference light to the detection unit; the coupling laser module is used for outputting coupling light to the detection unit; the local oscillation signal generation module is used for outputting a plurality of local oscillation microwave signals with the same phase and a propagation path perpendicular to a light beam path in the detection unit to the detection unit; the first detection light and the first reference light are received by the first balance detector, the second detection light and the second reference light are received by the second balance detector, and microwave information to be detected is obtained through calculation of the signal processing module.

According to various embodiments, a circuit for determining the frequency of a signal is described, comprising an input configured to receive an analog input signal, an analog to digital converter configured to convert the analog input signal to a digital input signal, a digital mixer configured to generate a mixing result signal by mixing the digital input signal with a single bit binary signal having a reference frequency, a low pass filter configured to generate a filtered signal by filtering the mixing result signal, a measuring circuit configured to measure the period of the filtered signal and an output configured to output a value differing from the frequency of the single bit binary signal by the inverse of the measured period as the frequency to be determined.

The invention proposes a non-contact method for measuring vibrations on a surface of an object. The method includes projecting light from one or more light sources to a region of interest on a surface of an object; detecting light diffusely reflected by the object surface using one or more detectors; determining the position change of the reflected light detected by the detector along with time; calculating, for at least one point on the surface of the object, a series of measurements of the vertical displacement of the surface over a period of time as a function of the change in position of the reflected light and using triangulation; and determining a frequency of a disturbance of the surface at the at least one point and an amplitude of the disturbance using the series of measurements of the vertical displacement.