1542 results about "Local oscillator" patented technology

The invention provides a simultaneous multiband superheterodyne receiver based on Rydberg atoms, and relates to the technical field of microwave electric field measurement, probe light provided by a probe light laser and coupling light provided by a coupling light laser oppositely enter an alkali metal atom gas chamber; the microwave signal sources of the multiple wave bands generate two paths of signals, one path of microwave signal is emitted to the space through the local oscillator microwave electric field emission horns of the wave bands, and the microwave electric field receiving horns of the wave bands receive corresponding echo signals. After frequency mixing of each wave band, the microwave electric field emission horn irradiates the alkali metal atom gas chamber at the same time, microwave fields of multiple wave bands are sequentially coupled with multiple pairs of continuous adjacent Rydberg states, and superheterodyne receiving is carried out on microwaves of multiple wave bands at the same time; and superheterodyne and high-sensitivity detection of microwave signals of multiple wave bands can be realized.

A laser distance ranging method includes splitting two combs of dual comb radiation into a signal radiation portion and a local oscillator radiation portion. The signal radiation portions are, after separation, combined into a combined signal radiation and directed onto an object, the distance to which is to be measured. The signal thrown back from the object is split into a first and second signal portions. The first signal portion is superimposed with the second local oscillator radiation portion to generate a first measurement signal, and the second signal portion is superimposed with the first local oscillator radiation portion to generate a second measurement signal. The distance to the object is determined from the first and second measurement signals, and from reference signals obtained by the partial reflection, wherein the Vernier effect can be used to extend ambiguity by comparison of the first and second measurement signals.

This invention provides an electromagnetic field detector, a system comprising the electromagnetic field detector, and a method of operating an electromagnetic field detector, the electromagnetic field detector comprising a first optical signal interface configured to receive, from one or more remote optical sources, a first optical signal; an electromagnetic field transmitter configured to transmit a local oscillator electromagnetic field generated from the first optical signal, the electromagnetic field transmitter comprising: a photocurrent generator configured to generate a photocurrent from the first optical signal; and an antenna interface configured to supply the photocurrent to an antenna to transmit the local oscillator electromagnetic field; a second optical signal interface configured to receive, from the one or more remote optical sources, a probe optical signal and a coupling optical signal; and a transmission medium configured to be excited by the probe optical signal and further excited by the coupling optical signal, wherein the probe optical

This disclosure describes an auto-calibration of mixers in a quantum orchestration platform. Predistortion is computed according to an RF signal that is downconverted with a local oscillator tone that is offset from an upconverter tone. Three tones present in the original RF signal are distinguished and used to construct a cost function. The minimization of the cost function is used to cancel an unwanted LO leakage and an image tone. Because the quantum orchestration platform generates both the unconverted IQ signals and the cost function for their optimization, the optimization can be performed in real time inside a single device without the need to communicate with external devices. This allows for the optimization of single sideband upconverted signals in a fraction of the time it typically takes using distributed systems employing separate waveform generators and spectrum analyzers.

The invention discloses an optical frequency comb repetition frequency locking device and method based on automatic power control, and relates to the technical field of optical frequency combs, the device comprises an optical frequency comb optical system, an optical fiber length automatic control system and an automatic power control system, the optical frequency comb optical system is used for generating optical frequency comb repetition frequency, the optical fiber length automatic control system locks the optical frequency comb repetition frequency output by the optical frequency comb optical system, and the automatic power control system is used for adaptively adjusting the signal power in a corresponding link when the optical frequency comb optical power or the reference source power changes. The input power of the mixer local oscillator and the radio frequency port is maintained at the preset power; according to the technical scheme of the invention, the stability and accuracy of the input power of the radio frequency and local oscillation port of the mixer are improved, the suppression of noise in a link is enhanced, a phase-locked loop of an optical fiber length automatic control system can be maintained in an optimal working state for a long time, and the practicability of an optical frequency comb product is improved.

The invention discloses a method for estimating the transmittance of a time-varying channel based on a frequency division multiplexing pilot frequency, and aims to solve the problem that the existing method for estimating the transmittance by adopting average transmittance does not have the capabilities of timely feedback and dynamic adjustment. The method comprises the following steps of: measuring a regular position component and a regular momentum component of a received signal by receiving a quantum signal and a pilot signal of frequency division multiplexing in a local local oscillator continuous variable quantum key distribution system generated by a transmitting end in real time; compensating phase noise caused by frequency offset and channel jitter due to different center frequencies of two independent lasers at a receiving end and a transmitting end by using a frequency offset compensation and phase recovery algorithm, and performing band-pass filtering to obtain a recovered pilot signal; and calculating the power ratio of the obtained pilot signal to the pre-calibrated pilot signal at each moment to obtain the time-varying free space transmittance. The performance change of the system in different time periods can be accurately reflected, the communication performance of the CVQKD system can be optimized, the success rate of key transmission can be improved, and the adaptability and robustness of the system can be improved.

The invention relates to a high-sensitivity anti-interference satellite navigation signal receiving system and method based on Rydberg atoms, and the system comprises a signal detection unit which is used for receiving a satellite navigation direct signal and outputting an electric signal; the data receiving unit is used for processing the electric signal output by the signal detection unit and outputting a navigation message; the power distribution unit is used for providing power for the signal detection unit and the data receiving unit; the signal detection unit comprises an atomic antenna which comprises four miniature atomic air chambers and is used for receiving satellite navigation direct signals from different directions; the light path system is used for providing detection laser and coupling laser for the miniature atomic gas chamber so as to excite atoms in the miniature atomic gas chamber from a first low-energy-level state to a high-energy-level state; and the patch antenna is arranged on one side of the miniature atomic gas chamber and is used for providing a local oscillation microwave signal for the miniature atomic gas chamber so as to realize superheterodyne high-sensitivity microwave signal receiving.

The invention provides a quantum communication system, method and device, and is applied to the technical field of quantum communication. The quantum communication system comprises a first device and a second device which are connected through an optical fiber link, the first device generates an initial optical signal and a local oscillation optical signal, sends the initial optical signal to the second device, receives a quantum optical signal from the second device, and sends the quantum optical signal to the second device. Performing coherent detection and demodulation based on the local oscillator optical signal and the quantum optical signal to generate a quantum key, monitoring a preset parameter in the coherent detection and demodulation process, and adjusting the local oscillator optical signal to enable the preset parameter to reach a preset value; and the second equipment receives the initial optical signal, performs quantum state modulation on the initial optical signal to form a quantum optical signal, and sends the quantum optical signal to the first equipment. According to the embodiment of the invention, the deployment cost of the quantum communication system can be reduced, and the optimization of equipment power consumption and detection efficiency in the key distribution process is realized.

The invention relates to the technical field of semiconductor lasers, in particular to a DFB laser based on a top metal grating, and the DFB laser comprises a gain chip, the left end face of the gain chip is plated with a high-reflection HR film, and the right end face of the gain chip is plated with an anti-reflection AR film; the upper end face of the gain chip is provided with a ridge optical waveguide, and the upper end face of the ridge optical waveguide is provided with a metal Bragg reflection grating layer. A self-heterodyne interference method (the line width of a local oscillator is smaller than 500 Hz) is adopted, and the measured value of the 3dB line width is 50 Hz (the measured value of a traditional DFB is 125 kHz). The mode purity degree is verified through a Lorenzian fitting broadening factor 1.15; the wavelength drift is less than 0.05 pm / DEG C within the range of-40 DEG C to 85 DEG C after compensation of the temperature compensation circuit. The temperature tuning coefficient is 0.08 pm / DEG C, the current tuning coefficient is 0.05 pm / mA, and the tuning coverage range is 1530-1545 nm.

A displacement-sensing Doppler radar with ultra-low noise and high sensing resolution is provided. The radar includes N two frequency synthesizers to respectively generate, at different frequencies, a transmitted signal that is radiated toward a target object, and a local oscillator (LO) signal. The radar further includes a mixer and a rectifier to: (1) receive a returned signal from the target object carrying phase delays corresponding to detected displacements of the target object; (2) mix the returned signal and the LO signal to generate a down-converted sine-wave intermediate frequency (IF) signal; and (3) rectify the sine-wave IF signal to a square-wave IF signal, which also carries the displacement-induced phase delays. The radar also includes a phase demodulation module to convert the displacement-induced phase delays into a pulse-modulated signal. The radar further includes a low-pass filter to convert the modulated pulse signal into an output voltage signal indicative of the detected displacements.

The invention discloses a multi-channel transceiving integrated system based on an RFSOC (Radio Frequency System On Chip) and a radio frequency SIP (Session Initiation Protocol). The multi-channel transceiving integrated system comprises an RFSOC system, a multi-channel clock synchronization module, a radio frequency SIP system and a power supply network, the RFSOC system comprises a control sampling module, a storage module and an optical fiber module, the control sampling module comprises a plurality of RFSOC chips, a CPLD (Complex Programmable Logic Device) chip and a main control chip, and the RFSOC chips are used for processing intermediate frequency signals and realizing data interaction with the optical fiber module; the CPLD chip is used for enabling a power supply network; the main control chip is used for performing control coordination among the plurality of RFSOC chips; the storage module is used for realizing program solidification of the RFSOC system; the optical fiber module is used for realizing high-speed transmission of broadband receiving data; the multi-channel clock synchronization module is used for providing a clock reference of the whole system; the radio frequency SIP system comprises a radio frequency SIP module, a Balun network and a local oscillator power division amplification module. The radio frequency SIP module realizes receiving, transmitting and processing of multi-channel radio frequency signals. According to the invention, a multi-channel transmit-receive integrated system with high integration, large bandwidth and miniaturization can be realized.

The invention discloses a differential signal synthesis circuit of a double-IQ mixer, which belongs to the technical field of radio frequency microwave testing and comprises two single-ended IQ mixing modules, a 180-degree phase shift module and an in-phase combination module or a power division module. The single-ended IQ frequency mixing module is used for up-converting the single-ended IQ baseband signal to radio frequency or down-converting the radio frequency signal to the single-ended IQ baseband signal; the 180-degree phase shift module is used for converting an input signal into two paths of signals with a phase difference of 180 degrees; and the power division module is used for converting the radio frequency input signal into two paths of signals with the phase difference of 0 degree. According to the invention, the IQ mixer with a differential structure is constructed, so that the microwave band of the IQ mixer is comprehensively improved in the index aspects of local oscillator leakage, even-order component suppression, common-mode interference suppression, signal-to-noise ratio and the like; according to the invention, single-ended IQ mixers with various types and complete frequency bands can be constructed into a differential structure form, and signal indexes in numerous application scenes are improved.

This invention provides an electromagnetic field detector, a system comprising the electromagnetic field detector, and a method of operating an electromagnetic field detector, the electromagnetic field detector comprising a first optical signal interface configured to receive, from one or more remote optical sources, a first optical signal; an electromagnetic field transmitter configured to transmit a local oscillator electromagnetic field generated from the first optical signal, the electromagnetic field transmitter comprising: a photocurrent generator configured to generate a photocurrent from the first optical signal; and an antenna interface configured to supply the photocurrent to an antenna to transmit the local oscillator electromagnetic field; a second optical signal interface configured to receive, from the one or more remote optical sources, a probe optical signal and a coupling optical signal; and a transmission medium configured to be excited by the probe optical signal and further excited by the coupling optical signal, wherein the probe optical signal has a probe frequency set to excite electrons of the transmission medium to a first excited state and the coupling optical signal has a coupling frequency set to excite electrons of the transmission medium to a predetermined Rydberg state so as to induce an Electromagnetic Induced Transparency, EIT, effect, wherein the transmission medium is further configured to receive a phase-modulated electromagnetic field from a remote transmitter and the local oscillator electromagnetic field such that the combination of the phase-modulated electromagnetic field and the local oscillator electromagnetic field causes a change in the probe optical signal from which a phase state of the phase-modulated electromagnetic field can be detected.

The invention provides a microwave superheterodyne frequency sweep measurement system based on Rydberg atoms, and belongs to the technical field of microwave frequency measurement. The laser module excites detection light of 780 nm and coupling light of 480 nm, and the two beams of light are reversely input into the atomic gas chamber through the dichroscope; signal microwaves are generated by a radio frequency signal source and are radiated to the position of the atomic gas chamber through the horn antenna; local oscillation microwaves are generated by the microwave module and are also radiated to the position of the atomic gas chamber through the horn antenna; the atomic gas chamber serves as a mixer to form a difference frequency signal; the spectrum analyzer is used for monitoring low-frequency difference frequency signals generated in the frequency mixing process in real time and recording signal intensity in real time. According to the invention, high-precision and wide-band microwave frequency measurement is realized, continuous and smooth frequency sweeping response can be provided in a frequency range, and absolute frequency detection of microwave signals is realized under the condition that a complex frequency comb technology is not introduced. The hardware architecture is simplified, the automation degree is improved, and integration, popularization and application are facilitated.

The invention provides a signal receiving device, a signal transmitting device and an optical fiber sensing device, relates to the technical field of optical fiber sensing, and is used for solving the problems that the requirement for equipment is high when an existing optical fiber sensing device detects Rayleigh scattering and Brillouin scattering at the same time and the like. The signal receiving device comprises a coherent receiver, a radio frequency analog-to-digital conversion unit and a frequency band calculation unit, the coherent receiver is used for obtaining four electric signals with orthogonal phases according to the local oscillation light and the signal light, and the radio frequency analog-to-digital conversion unit converts the four electric signals to obtain two digital signals in a first polarization state and two digital signals in a second polarization state; the frequency band calculation unit is used for calculating the frequency spectrum of the signal light according to the two paths of digital signals of the first polarization state of the signal light and the two paths of digital signals of the second polarization state of the signal light, and the frequency spectrum comprises a phi OTDR signal located at the positive frequency and a BOTDR signal located at the negative frequency.

Coherent wavelength division multiplexing is provided using frequency comb sources for both the transmitter and the local oscillator (LO) in the receiver. The local oscillator is made phase coherent with the received multifrequency optical signal using two analog control loops. One of the control loops locks an optical frequency of the local oscillator to an optical frequency of the received frequency comb. The other control loop locks a microwave frequency of the local oscillator (i. e. LO the comb spacing) to the comb spacing of the received frequency comb. As a result, coherent detection is enabled in all channels with just two analog control loops. Control signals for the two loops can be derived from two of the received channels individually (asymmetric carrier recovery), or they can be derived from sum and difference signals from two of the received channels (symmetric carrier recovery).

The invention relates to the technical field of communication, and discloses a network communication chip signal interference suppression processing method. The method comprises the following steps: acquiring a local oscillator phase jitter sequence in real time through an on-chip phase noise monitoring unit; estimating Doppler frequency shift and channel coherence time based on the sequence; dynamically adjusting the closed-loop bandwidth of the phase-locked loop; and generating a phase compensation signal, and performing time-varying channel minimum mean square error equalization in combination with a received baseband signal to eliminate inter-symbol interference. The system integrates a phase noise monitoring function module, a channel parameter estimation function module, a phase-locked loop bandwidth regulation function module, a phase compensation generation function module and an interference joint elimination function module. By means of dynamic bandwidth reconstruction and high-precision phase compensation, the bit error rate under high-speed movement is remarkably reduced, the 5G millimeter wave communication standard requirement is met, and the method has the advantages of being achieved on a whole chip, low in delay and high in robustness.

In some examples, a method includes receiving, at a first device, a radar signal transmitted by a second device at a transmission frequency offset from a local oscillator (LO) frequency of the first device by a target offset and reflected off a target. The method also includes determining an intermediate frequency (IF) of the radar signal based on the transmission frequency and the LO frequency. The method also includes determining a parts per million (ppm) offset between the first device and the second device based on the intermediate frequency and the target offset.

The invention relates to the technical field of electromagnetic detection, in particular to an anti-electromagnetic interference Rydberg atom receiving device and method. The device comprises two parallel plate waveguide atomic probes with integrated optical fiber gas chambers, a 852nm frequency stabilization module, a 509nm frequency stabilization module and three microwave sources. The three microwave sources are respectively used for generating a local oscillation field signal, a signal field signal and an interference field signal; an alkali metal atom gas chamber is embedded in each of the two parallel plate waveguide atom probes, a first alkali metal atom gas chamber in the first parallel plate waveguide atom probe receives a local oscillation field signal, a signal field signal and an interference field signal, and mixes the local oscillation field signal and the signal field signal to generate an intermediate frequency signal; the second parallel plate waveguide atom probe is used for realizing signal interference resistance by compensating alternating current stark energy shift; the device provided by the invention is simple in structure and high in sensitivity, the anti-interference capability of microwave signal detection can be effectively improved, and the signal detection precision and reliability of the device in a complex electromagnetic environment are ensured.

The invention discloses a wavefront correction system and method for an offshore quantum key distribution system, and relates to the technical field of wavefront correction, and the system comprises a laser, a transmission light path, a redundant light optical antenna, at least three local oscillator light optical antennas, a signal preprocessing module and a wavefront correction module. The laser generates an initial optical signal; the transmission optical path divides the initial optical signal into a local oscillator optical signal and a redundant optical signal, and transmits the local oscillator optical signal, the redundant optical signal and an echo signal; the local oscillator optical antenna transmits a local oscillator optical signal and receives a local oscillator echo signal in a corresponding direction; the redundant light optical antenna transmits a redundant light signal and receives a redundant echo signal in a corresponding direction; the signal preprocessing module preprocesses and corrects the local oscillator echo signal and the redundant echo signal to obtain a target beam signal; and the wavefront correction module calculates a real-time atmospheric turbulence value according to the target beam signal to carry out wavefront correction. The three-dimensional velocity vector component of the carrier can be measured at the same time.

The current disclosure is related to digital-to-analog converters (DACs) with localized frequency multiplication circuits. For example, an electronic device may include a local oscillator (LO) providing clock signals, a digital front-end providing digital signals, a DAC, (e.g., a radio frequency DAC (RFDAC)), and one or more antennas. The DAC may include a number of cells (e.g., unit power amplifiers). Moreover, each cell may provide a unit power analog signal upon activation with a higher frequency than the received digital signals and clock signals. The DAC may provide an output signal (e.g., an analog signal) based on combining (e.g., aggregating) the unit power analog signals of the activated cells for transmission by the one or more antennas.

The invention provides a GEO communication satellite uplink signal Doppler frequency compensation method and device. The method comprises the following steps: acquiring a satellite orbit determination result corresponding to a GEO communication satellite; determining a Doppler compensation frequency curve according to the satellite orbit measurement result and the local frequency of the frequency conversion of a satellite transponder configured in the GEO communication satellite; and compensating a first uplink signal to be transmitted from the ground station to the GEO communication satellite by using the Doppler compensation frequency curve through the compensation frequency mixer, and transmitting the compensated first uplink signal to the GEO communication satellite. According to the invention, under the condition that the user receiver is non-inductive, the carrier frequency and the spreading code rate of the user receiver are changed in equal proportion, so that the user receiver can adopt a receiving algorithm of the carrier-assisted spreading code rate to improve the sensitivity.

An optical frequency domain reflectometer with environmental disturbance resistance and large strain measurement capability belongs to the field of distributed optical fiber sensing and comprises an opposite sweep frequency light frequency modulation continuous wave signal generation module, a light splitting device, a modulation device, a circulator, a polarization controller, an optical coupling device, a photoelectric conversion module and a data acquisition and processing module. An optical signal generated by an opposite sweep frequency light frequency modulation continuous wave signal generation module is divided into probe light and local oscillation light through a light splitting device, the probe light is modulated through a modulation device and sent to an optical fiber through a circulator, and a Rayleigh back scattering light signal generated by the optical fiber and the local oscillation light interfere in an optical coupling device to obtain interference light; the photoelectric conversion module mixes beat frequency signals of interference light, and the data acquisition and processing module analyzes and processes the beat frequency signals. According to the invention, the position information of the Rayleigh backscattering point is marked by using the modulated probe light, the Rayleigh scattering signal at the corresponding position is restored, crosstalk between channels is inhibited, and high-precision measurement in a large dynamic range and resistant to environmental disturbance is realized.

The present disclosure provides an optical module, comprising a coherent assembly for receiving local oscillator light and a first optical signal and performing coherent demodulation on the local oscillator light and the first optical signal. A reception photodetector generates a photo-generated current from the first optical signal. A transimpedance amplifier receives the photo-generated current and amplifies the photo-generated current to output a voltage signal. An analog-to-digital conversion sampler converts the voltage signal into an AD sampling value and transmits the AD sampling value to an MCU formula. The AD sampling value is substituted into a reference optical power formula to calculate a reference optical power value, and the current frequency value is substituted into a frequency deviation formula to calculate the current frequency deviation. The current frequency deviation is subtracted from the reference optical power value to obtain an optical power calculation value as a reported optical power.

The invention provides a joint demodulation method based on a fiber grating array distributed sensing system, and the distributed sensing system comprises a sweep frequency light source module, a pulse modulation module, a light beam coupling module, a grating array module, a photoelectric conversion module, and a signal collection and processing module. A radio frequency signal is modulated to sweep frequency laser output by the sweep frequency light source module through the pulse modulation module and then input to the light beam coupling and photoelectric conversion module, a modulated light signal is divided into two paths by a beam splitter, one path serves as local oscillator reference light, and the other path is input to the grating array module. The local oscillator reference light and the reflected light of the grating array are coupled and then input into the photoelectric detector to realize photoelectric conversion, and are acquired and processed by the signal acquisition and processing module to obtain a wavelength-microwave photon time domain impact response set of the distributed sensing system in a scanning period of the frequency sweeping light source; and demodulating the position of the fiber grating corresponding to the sensing quantity corresponding to the time domain impulse response and sensing information corresponding to the wavelength.

A low noise block-downconverter system (LNB system) includes a local oscillator module having first and second phase locked loop circuitry (PLL circuitry) for downconverting an electrical signal to generate a downconverted signal. The first PLL circuitry receives a low-frequency reference signal that is used with an intermediate-frequency oscillator to generate an intermediate-frequency signal. The second PLL circuitry receives and uses the intermediate-frequency signal in conjunction with a high-frequency oscillator, separate from the intermediate-frequency oscillator, to generate a high-frequency signal. The high-frequency signal is used to downconvert the electrical signal. The signal dynamic range of the first PLL circuitry is higher than the signal dynamic range of the second PLL circuitry, thus achieving improved overall dynamic range for the LNB system. The first PLL circuitry may be a first integrated circuit defining a low phase-noise amplifier. A second integrated circuit may include the second PLL circuitry and the high-frequency oscillator.

The invention discloses a method and a device for processing VHF (very high frequency) and UHF (ultra high frequency) navigation signals based on ZYNQ, and relates to the technical field of signal processing, and the method and the device are characterized in that a single ZYNQ chip is used for replacing an FPGA (field programmable gate array) + DSP (digital signal processor) dual-chip framework of a digital processing part of a traditional aviation navigation signal receiver, so that the system integration level is increased, the design is more compact, the circuit design is simpler, and the system reliability is improved. Lightweight design of airborne equipment is facilitated; besides, by means of the strong processing performance of the PL part of the ZYNQ chip and the high-speed analog-to-digital conversion chip (ADC) which develops rapidly, receiving of VHF and UHF navigation signals can be achieved through the radio frequency direct sampling technology, complete digitization of analog down-conversion is achieved, and the advantages are that the problems of leakage and frequency offset of an analog local oscillator and generation of more harmonic waves and stray can be solved. And the electromagnetic interference of equipment is obviously reduced.

A mixer includes a mixing stage, and a first transistor and a second transistor coupled to the mixing stage. A gate of the first transistor is coupled to a first input of the mixer, and a gate of the second transistor is coupled to a second input of the mixer. The mixer also includes a first source resistor coupled to a source of the first transistor, and a second source resistor coupled to a source of the second transistor. The mixer further includes an amplifier having a first input coupled to the source of the first transistor, and a second input coupled to the source of the second transistor. The amplifier is configured to adjust at least one bias voltage of at least one of the first transistor and the second transistor based on a differential voltage between the first and second inputs of the amplifier.

The invention provides a CV-QKD real-time parameter estimation method and system for resisting local oscillation light intensity fluctuation, and the method comprises the steps: obtaining an initial shot noise calibration value through calibrating an LO intensity value before the start of a quantum key distribution process; in the quantum key distribution process, the received LO is subjected to beam splitting, the stronger path is used for coherent detection of quantum signal light, and the weaker path is used for LO intensity fluctuation monitoring; performing parameter estimation according to data obtained by coherent detection and the initial shot noise calibration value to obtain over-noise epsilon'and transmissivity T '; and according to the LO intensity fluctuation monitoring result, the LO intensity fluctuation monitoring result is considered in the parameter estimation process, and the over-noise epsilon'and the transmissivity T 'are corrected to obtain the over-noise epsilon and the transmissivity T close to the ideal LO condition. According to the method, the performance and the safety of the Gaussian modulation coherent state protocol CV-QKD system can be effectively improved.

The invention provides a counter, a phase-locked loop, an automatic frequency control system and a control method, and the counter comprises a sampling window generation module which generates a sampling window signal according to a reference clock signal; the counting module is used for counting the number of cycles of the local oscillator clock signal according to the sampling window signal to obtain an initial count value; the edge detector is used for detecting clock edges of the reference clock signal and the local oscillator clock signal and obtaining an addition and subtraction indication signal according to detected edge information; and the counter calibrates the initial count value according to the addition and subtraction indication signal to obtain a counting result. According to the scheme of the invention, an additional edge detection mechanism is added in the counter, and the counting result of the counting module is calibrated, so that the counting precision of the counter is improved, and the accuracy of a frequency control result can be ensured.