Antenna gain calibration system and method based on Rydberg atoms

Abstract

The embodiment of the invention relates to the field of antenna calibration, in particular to an antenna gain calibration system and method based on Rydberg atoms, and the system comprises a frequency stabilization module of a detection light source, a light path module, a microwave module, a signal detection module and a darkroom. A frequency stabilization module of the detection light source is used for stabilizing the laser wavelength of a semiconductor laser in a light path module, so that the laser wavelength is suitable for detection light of a Rydberg electromagnetically induced transparency (EIT) system; the light path module is used for generating coupling light and detection light; the coupling light and the detection light are oppositely emitted in an alkali metal atom gas chamber in the darkroom, alkali metal atoms in the alkali metal atom gas chamber are excited to be in a Rydberg state through two-stage excitation, and an EIT signal window needed by an experiment is obtained; the microwave module is used for generating and transmitting a microwave signal to control a microwave electric field in an experiment, and the microwave electric field influences an EIT signal; the signal detection module is used for converting the detection light into an electric signal, and the electric signal is collected through an oscilloscope in the signal detection module so as to be analyzed.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of antenna calibration, and in particular to an antenna gain calibration method based on Rydberg atoms. Background Art

[0002] In the field of microwave electric field amplitude measurement, the commonly used calibration methods are the "standard antenna" and "standard field" methods. These methods use an electric dipole antenna as an electric field probe to calibrate microwave electric fields. This technology can detect microwave electric fields with a field strength of 1V / m, but its measurement uncertainty is approximately 12%. Traditional electric dipole antenna probes consist of an impedance-loaded dipole antenna and a detector diode. Alternating current in a conductor induces electron motion, generating electromagnetic radiation, thereby radiating and receiving microwave electric fields. The received microwave electric field is converted to DC current by the diode, and the voltage is measured using a DC voltmeter to infer the microwave electric field strength.

[0003] Existing antenna calibration methods primarily include equivalent capacitance substitution, the two-antenna method, the three-antenna method, and the standard site method. The equivalent capacitance substitution method requires replacing a 1m-long antenna pole with a 10pF capacitor, while the two-antenna method and the three-antenna method require two or three antennas of the same model, respectively, for calibration. A common problem with these mainstream calibration methods is that they require the use of the same, previously calibrated antenna, leading to a circular calibration problem. Summary of the Invention

[0004] One purpose of the embodiments of the present application is to provide an antenna gain calibration system and method based on Rydberg atoms to solve the technical problem in the prior art of using the same, calibrated antenna for calibration, thereby generating cyclic calibration.

[0005] In a first aspect, a Rydberg atom-based antenna gain calibration system is provided, comprising: a frequency stabilization module of a detection light source, an optical path module, a microwave module, a signal detection module, and a darkroom; the frequency stabilization module of the detection light source is used to stabilize the laser wavelength of the semiconductor laser in the optical path module, so that the laser wavelength is suitable for the detection light of the Rydberg EIT system; the optical path module is used to generate coupling light and the detection light; the coupling light and the detection light are irradiated against the alkali metal atom gas chamber in the darkroom, and the alkali metal atoms in the alkali metal atom gas chamber are excited to the Rydberg state through two-stage excitation, thereby achieving the EIT signal window required for the experiment; the microwave module is used to generate and transmit microwave signals to control the microwave electric field in the experiment, and the microwave electric field affects the interaction between the detection light and the coupling light; the signal detection module is used to convert the detection light into an electrical signal, so that the oscilloscope in the signal detection module collects the electrical signal for analysis.

[0006] With reference to the first aspect, in a possible implementation, the darkroom further includes an antenna to be calibrated, and the antenna to be calibrated is also located in the microwave module.

[0007] In combination with the first aspect, in one possible implementation, the frequency stabilization module of the detection light source includes a first fiber coupling head, a fiber electro-optic modulator, a second fiber coupling head, a polarization beam splitter, a λ / 4 glass plate, an ultra-stable cavity, a charge-coupled device camera, a photodetector, a third fiber coupling head, a mixer, a first signal generator, a second signal generator, and a proportional-integral-differential circuit.

[0008] In combination with the first aspect, in a possible implementation, the semiconductor laser light emits a laser as the detection light, and the laser enters the polarization-maintaining single-mode optical fiber through the first optical fiber coupling head; the laser is modulated in the optical fiber electro-optic modulator by the sinusoidal signal generated by the second signal generator to obtain a modulated laser; the modulated laser enters a preset space through the second optical fiber coupling head, the modulated laser is completely reflected by the polarization beam splitter prism, and the reflected modulated laser enters the ultra-stable cavity through the λ / 4 glass; the first part of the light corresponding to the reflected modulated laser passes through the The ultrastable cavity is captured by the charge-coupled device camera and the photodetector for monitoring the detection light signal; the second part of the light corresponding to the modulated laser after the reflection is reflected in the ultrastable cavity, passes through the λ / 4 glass again, changes the polarization direction, transmits through the polarization beam splitter prism, and is converted into an electrical signal by the photodetector; the electrical signal and the sinusoidal signal generated by the first signal generator are modulated and demodulated in the mixer to obtain an error signal; the error signal is input to the proportional-integral-differential circuit to generate a feedback signal, and the feedback signal is transmitted to the semiconductor laser to stabilize the laser wavelength of the laser for a long time.

[0009] In combination with the first aspect, in a possible implementation, the optical path module includes the semiconductor laser, a frequency-doubling laser, a fourth fiber coupling head, a fifth fiber coupling head, a wavelength meter, a sixth fiber coupling head, and a seventh fiber coupling head; the frequency-doubling laser is used to generate the required coupled light; the seed light before frequency doubling is transmitted to the wavelength meter via the fifth fiber coupling head to monitor its wavelength; the laser light emitted by the semiconductor laser is transmitted to the wavelength meter via the fourth fiber coupling head to monitor its wavelength; the coupled light after frequency doubling enters the single-mode optical fiber for transmission via the sixth fiber coupling head; and the laser light emitted by the semiconductor laser enters the single-mode optical fiber for transmission via the seventh fiber coupling head.

[0010] In combination with the first aspect, in one possible implementation, the microwave module includes a computer device, a microwave signal source, a power amplifier, and the antenna to be calibrated; the computer device calculates and controls the microwave signal source to emit the microwave signal; the microwave signal is amplified by the power amplifier and then transmitted to the antenna to be calibrated to emit the microwave electric field.

[0011] In a second aspect, a method for calibrating antenna gain based on Rydberg atoms is provided, which is implemented based on the system according to any one of the first aspects, and is characterized by comprising:

[0012] Obtain antenna parameters of the antenna to be calibrated;

[0013] Obtaining the amplitude and frequency of the microwave field to be measured;

[0014] Determining whether the antenna to be calibrated meets calibration conditions according to the antenna parameters of the antenna to be calibrated, the amplitude of the microwave field to be measured, and the microwave frequency;

[0015] When the antenna to be calibrated meets the calibration condition, antenna gain calibration is performed on the antenna to be calibrated according to a preset calibration antenna.

[0016] In combination with the second aspect, in a possible implementation method, the antenna to be calibrated is judged whether it meets the calibration conditions based on the antenna parameters of the antenna to be calibrated, the amplitude of the microwave field to be measured and the microwave frequency, including judging whether the antenna to be calibrated meets the far-field conditions based on the antenna parameters; if the far-field conditions are met, the splitting frequency interval is calculated based on the amplitude of the microwave field to be measured and the microwave frequency; when the splitting frequency interval is greater than twice the EIT peak linewidth, it is determined whether the antenna to be calibrated meets the calibration conditions, and the twice the EIT peak linewidth is obtained by the action of the coupling light and the detection light in the antenna gain calibration system based on Rydberg atoms.

[0017] In combination with the second aspect, in a possible implementation, when the antenna to be calibrated meets the calibration conditions, antenna gain calibration is performed on the antenna to be calibrated according to a preset calibration antenna, including: obtaining a first microwave frequency and multiple preset field strength values; obtaining a first relationship curve of the preset calibration antenna at the first microwave frequency according to a preset formula, the multiple preset field strength values, the first microwave frequency, and preset antenna parameters of the preset calibration antenna, wherein the first relationship curve includes a fitted frequency difference of the preset calibration antenna; obtaining a second relationship curve of the antenna to be calibrated at the first microwave frequency according to the multiple preset field strength values, the first microwave frequency, and the antenna parameters of the antenna to be calibrated, wherein the second relationship curve includes a fitted frequency difference of the antenna to be calibrated; obtaining a difference range of the antenna to be calibrated according to the first relationship curve and the second relationship curve; and performing antenna gain calibration on the antenna to be calibrated according to the difference range.

[0018] In combination with the second aspect, in a possible implementation, obtaining a second relationship curve of the antenna to be calibrated at the first microwave frequency based on the preset multiple field strength values, the first microwave frequency, and the antenna parameters of the antenna to be calibrated includes: obtaining a resonant frequency range corresponding to the Rydberg state; determining at least one resonant frequency based on the resonant frequency range; obtaining multiple data points based on the preset multiple field strength values, the at least one resonant frequency, and the EIT peak linewidth corresponding to each resonant frequency, wherein the EIT peak linewidth is obtained by the action of coupled light and detection light in the antenna gain calibration system based on Rydberg atoms; and drawing the second relationship curve based on the multiple data points.

[0019] In the scheme implemented by the above-mentioned antenna gain calibration system and method based on Rydberg atoms, the frequency stabilization mode of the detection light source in this scheme ensures the laser wavelength stability of the semiconductor laser, thereby improving the accuracy and reliability of the detection light of the Rydberg EIT system, enabling the experiment to be carried out within the preset EIT signal window; further, the optical path module effectively generates coupling light and detection light, providing the necessary optical conditions for the experiment, ensuring that the alkali metal atoms can be accurately excited to the Rydberg state; the microwave module generates and transmits microwave signals, accurately controls the microwave electric field in the experiment, optimizes the interaction between the detection light and the coupling light, and enhances the clarity and contrast of the EIT signal; the signal detection module converts the detection light into an electrical signal, enabling the oscilloscope to collect and analyze the electrical signal, providing convenience for the acquisition and processing of experimental data, and improving the quality of the data and the accuracy of the experimental results; the darkroom provides an interference-free environment, reduces external light and electromagnetic interference, ensures the stability and repeatability of the experiment, and thus improves the accuracy of the experiment and the accuracy of the calibration as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 1 is a schematic structural diagram of an antenna gain calibration system based on Rydberg atoms in one embodiment of the present invention;

[0022] Figure 2 1 is a flow chart of a method for calibrating antenna gain based on Rydberg atoms in one embodiment of the present invention;

[0023] Figure 3 A schematic diagram of a curve showing the relationship between AT splitting and microwave frequency at different microwave powers in one embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0025] It should be noted that, if there is no conflict, the various features in the embodiments of the present application can be combined with each other and are all within the scope of protection of the present application. In addition, although the functional modules are divided in the device schematic and the logical order is shown in the flow chart, in some cases, the steps shown or described can be performed in a different order than the module division in the device or the order in the flow chart. Furthermore, the words "first", "second", "third", etc. used in this application do not limit the data and execution order, but only distinguish between the same items or similar items with basically the same functions and effects.

[0026] The present invention is described in detail below through specific examples.

[0027] The technical solution of the present application can be applied to antenna gain calibration scenarios based on Rydberg atoms.

[0028] In view of this, the present application proposes an antenna gain system based on Rydberg atoms, which is described in detail below.

[0029] See also Figure 1 , Figure 1A schematic diagram of the structure of an antenna gain calibration system based on Rydberg atoms provided in an embodiment of the present invention. Figure 1 The antenna gain calibration system based on Rydberg atoms includes a semiconductor laser 1, a first fiber coupling head 2, a fiber electro-optic modulator 3, a second fiber coupling head 4, a polarization beam splitter 5, a λ / 4 glass plate 6, an ultra-stable cavity 7, a charge-coupled device camera 8, a photodetector 9, a third fiber coupling head 10, a mixer 11, a first signal generator 12, a second signal generator 13, a proportional integral differential circuit 14, a frequency-doubled laser 15, a fourth fiber coupling head 16, a fifth fiber coupling head 17, a wavelength meter 18, a sixth fiber coupling head 19, a seventh fiber coupling head 22, an eighth fiber coupling head 20, a ninth fiber coupling head 21, an alkali metal atom gas chamber 23, a computer device 24, a microwave signal source 25, a power amplifier 26, an antenna to be calibrated 27, a tenth fiber coupling head 28, an oscilloscope 29, and a computer device 30. Among them, the detection light source includes a frequency stabilization module 31, an optical path module 32, a microwave module 35, a signal detection module 33, and a darkroom 34.

[0030] Specifically, the detection light source includes a frequency stabilization module 31, an optical path module 32, a microwave module 35, a signal detection module 33 and a darkroom 34; the frequency stabilization module 31 of the detection light source is used to stabilize the laser wavelength of the semiconductor laser 1 in the optical path module 32, so that the laser wavelength is suitable for the detection light of the Rydberg EIT system; the optical path module 32 is used to generate coupling light and the detection light; the coupling light and the detection light are irradiated against the alkali metal atom gas chamber 23 in the darkroom 34, and the alkali metal atoms in the alkali metal atom gas chamber 23 are excited to the Rydberg state after two-stage excitation, thereby achieving the EIT signal window required for the experiment; the microwave module 35 is used to generate and transmit microwave signals to control the microwave electric field in the experiment, and the microwave electric field affects the interaction between the detection light and the coupling light; the signal detection module 33 is used to convert the detection light into an electrical signal, so that the oscilloscope 29 in the signal detection module 33 collects the electrical signal to analyze the electrical signal.

[0031] Among them, the laser of semiconductor laser 1 serves as the detection light source of the Rydberg EIT system (electromagnetically induced transparency, abbreviated as EIT). The maximum output power of this laser is about 70mW, the adjustable range without mode hopping is greater than 20GHz, and the laser frequency linewidth is about 300kHz.

[0032] The coupled light enters free space through the eighth fiber coupling head, then enters the single-mode fiber through the ninth fiber coupling head, where it is incident with the probe light in the alkali metal atomic chamber. After two-stage excitation, the alkali metal atoms in the chamber are excited to the Rydberg state, achieving the EIT signal window required for the experiment. The atomic chamber and the antenna to be calibrated are placed in a darkroom together, which can effectively shield the interference of external signals to improve the experimental effect.

[0033] After passing through the alkali metal atom gas chamber, the probe light enters free space through the eighth fiber optic coupling head. It is converted into an electrical signal by the tenth fiber optic coupling head and transmitted to an oscilloscope 29 for observation of the experimental results. Computer equipment 30 is used to record and store the signals obtained by oscilloscope 29.

[0034] In a possible example, the darkroom 34 further includes an antenna 27 to be calibrated, and the antenna 27 to be calibrated is also located in the microwave module 35 .

[0035] In one possible example, the frequency stabilization module 31 of the detection light source includes a first fiber coupling head 2, a fiber electro-optic modulator 3, a second fiber coupling head 4, a polarization beam splitter prism 5, a λ / 4 glass plate 6, an ultra-stable cavity 7, a charge-coupled device camera 8, a photodetector 9, a third fiber coupling head 10, a mixer 11, a first signal generator 12, a second signal generator 13, and a proportional-integral-differential circuit 14.

[0036] In one possible example, the semiconductor laser 1 emits a laser as the detection light, and the laser enters the polarization-maintaining single-mode optical fiber through the first optical fiber coupling head 2; the laser is modulated in the optical fiber electro-optic modulator 3 by the sinusoidal signal generated by the second signal generator 13 to obtain a modulated laser; the modulated laser enters the preset space through the second optical fiber coupling head 4, the modulated laser is completely reflected by the polarization beam splitter prism 5, and the reflected modulated laser enters the ultra-stable cavity 7 through the λ / 4 glass plate 6; the first part of the light corresponding to the reflected modulated laser passes through the ultra-stable cavity 7 and is The charge coupled device camera 8 and the photodetector 9 are used to capture and monitor the detection light signal; the second part of the light corresponding to the modulated laser after the reflection is reflected in the ultra-stable cavity 7, passes through the λ / 4 glass 6 again, changes the polarization direction, transmits through the polarization beam splitter prism 5, and is converted into an electrical signal by the photodetector 9; the electrical signal and the sinusoidal signal generated by the first signal generator 12 are modulated and demodulated in the mixer 11 to obtain an error signal; the error signal is input to the proportional integral differential circuit 14 to generate a feedback signal, and the feedback signal is transmitted to the semiconductor laser 1 to stabilize the laser wavelength of the laser for a long time.

[0037] Specifically, when cesium atoms are used to fill the alkali metal atom gas chamber, the corresponding probe light wavelength is 852nm, and the coupled light wavelength is 509nm. Using the PDH frequency stabilization technique based on electronic sideband modulation (ESM) used in the experiment above, the 852nm probe light frequency is stabilized to a frequency equal to the frequency interval between the two energy levels of the cesium atom, causing the probe light to resonate with the two energy levels of the cesium atom. The 509nm coupled light is then frequency-scanned using a frequency-doubled laser to generate the EIT-AT spectrum signal. This signal can be observed and stored using an oscilloscope located in the measurement module and connected to a computer device.

[0038] In a possible example, the optical path module 32 includes the semiconductor laser 1, a frequency-doubling laser 15, a fourth fiber coupling head 16, a fifth fiber coupling head 17, a wavelength meter 18, a sixth fiber coupling head 19, and a seventh fiber coupling head 20; the frequency-doubling laser 15 is used to generate the required coupled light; the seed light before frequency doubling is transmitted to the wavelength meter 18 via the fifth fiber coupling head 17 to monitor its wavelength; the laser light emitted by the semiconductor laser 1 is transmitted to the wavelength meter 18 via the fourth fiber coupling head 16 to monitor its wavelength; the coupled light after frequency doubling enters the single-mode optical fiber for transmission via the sixth fiber coupling head 19; the laser light emitted by the semiconductor laser 1 enters the single-mode optical fiber for transmission via the seventh fiber coupling head 20.

[0039] In a possible example, the microwave module 35 includes a computer device 24, a microwave signal source 25, a power amplifier 26 and an antenna to be calibrated 27; the computer device 24 calculates and controls the microwave signal source 25 to emit the microwave signal; the microwave signal is amplified by the power amplifier 26 and then transmitted to the antenna to be calibrated 27 to emit the microwave electric field.

[0040] The frequency stabilization of the detection light source in this scheme ensures the stability of the laser wavelength of the semiconductor laser, thereby improving the accuracy and reliability of the detection light of the Rydberg EIT system, allowing the experiment to be carried out within the preset EIT signal window; the further optical path module effectively generates coupling light and detection light, providing the necessary optical conditions for the experiment, ensuring that the alkali metal atoms can be accurately excited to the Rydberg state; the microwave module generates and transmits microwave signals, accurately controls the microwave electric field in the experiment, optimizes the interaction between the detection light and the coupling light, and enhances the clarity and contrast of the EIT signal; the signal detection module converts the detection light into an electrical signal, enabling the oscilloscope to collect and analyze the electrical signal, providing convenience for the acquisition and processing of experimental data, and improving the quality of the data and the accuracy of the experimental results; the darkroom provides an interference-free environment, reduces external light and electromagnetic interference, ensures the stability and repeatability of the experiment, and thus improves the accuracy of the experiment and the accuracy of the calibration as a whole.

[0041] It should be noted that, in each of the above-mentioned embodiments, there is not necessarily a certain order between the above-mentioned steps. A person skilled in the art can understand, based on the description of the embodiments of this application, that in different embodiments, the above-mentioned steps may have different execution orders, that is, they may be executed in parallel, or may be executed interchangeably, etc.

[0042] Figure 2 A schematic flow chart of a Rydberg atom-based antenna gain calibration method provided in an embodiment of the present invention is characterized in that the method comprises the following steps:

[0043] S10: Obtain antenna parameters of the antenna to be calibrated.

[0044] The antenna parameters may include but are not limited to the antenna's gain, size, bandwidth, impedance, polarization characteristics, directivity, and standing wave ratio (VSWR).

[0045] The acquisition process can include using a network analyzer to measure the antenna's return loss (Return Loss) and standing wave ratio (VSWR). These parameters can help determine the antenna's impedance matching; using an antenna measurement system to measure the antenna's directivity pattern through an antenna test range or outdoor test site to obtain gain and directivity; using a polarization grid or polarization state analyzer to measure the antenna's polarization characteristics; measuring the antenna's bandwidth through frequency scanning, that is, the frequency range in which the antenna can effectively operate; recording all measurement data and comparing them with the specifications provided by the antenna manufacturer to verify the antenna's performance.

[0046] S20. Obtain the amplitude and frequency of the microwave field to be measured.

[0047] The microwave field amplitude refers to the electric field strength of the microwave signal, while the microwave frequency refers to the oscillation frequency of the microwave signal. These data can help determine the characteristics of the microwave signal, and this information can be used during subsequent calibration to evaluate and adjust the antenna's gain and performance.

[0048] Among them, the acquisition process can be to use a spectrum analyzer to scan the signal within a specific frequency range and measure the amplitude of the signal; use a power meter to directly measure the power of the microwave signal, which is usually done through a probe or sensor; use a vector network analyzer to simultaneously measure the amplitude and phase of the signal to obtain more comprehensive signal characteristics; determining the microwave frequency may require the use of a frequency counter or other equipment that can accurately measure the frequency; when performing measurements, it is necessary to ensure that the test equipment matches the frequency and amplitude range of the microwave field to be measured to avoid measurement errors.

[0049] S30: Determine whether the antenna to be calibrated meets calibration conditions according to the antenna parameters of the antenna to be calibrated, the amplitude of the microwave field to be measured, and the microwave frequency.

[0050] Among them, the calibration conditions may be that the distance R between the antenna to be calibrated and the alkali metal atom gas cell satisfies the far-field condition, the splitting frequency interval is greater than twice the EIT peak line width, etc., which are not limited here.

[0051] For example, if the operating frequency range of the antenna to be calibrated does not match the microwave frequency to be measured, or if the microwave field amplitude is not within the expected range, calibration may be inaccurate or impossible. Therefore, this step ensures that subsequent calibration operations are only performed when specific conditions are met, thereby ensuring the reliability and accuracy of the calibration results.

[0052] S40: When the antenna to be calibrated meets the calibration condition, perform antenna gain calibration on the antenna to be calibrated according to a preset calibration antenna.

[0053] After confirming that the parameters of the antenna to be calibrated and the current microwave environment meet the requirements, a preset calibration antenna with known performance and parameters is used as a reference to perform gain calibration on the antenna to be calibrated. By comparing the response of the antenna to be calibrated and the preset calibration antenna under the same conditions, the gain of the antenna to be calibrated is adjusted and corrected to achieve the expected performance standard.

[0054] It can be seen that this implementation ensures that the gain of the antenna to be calibrated is accurate, thereby improving its performance and reliability in practical applications.

[0055] This solution effectively determines whether the antenna to be calibrated meets the calibration conditions by accurately obtaining the antenna parameters of the antenna to be calibrated and the amplitude and frequency of the microwave field to be measured. This not only improves the accuracy of parameter measurement but also ensures the targetedness and efficiency of the calibration work. When the antenna to be calibrated meets the calibration conditions, gain calibration is performed based on the preset calibration antenna, which helps optimize antenna performance and improve the transmission efficiency and receiving sensitivity of the communication system, thereby ensuring the efficient and stable operation of the entire system.

[0056] In a possible example, judging whether the antenna to be calibrated meets the calibration condition based on the antenna parameters of the antenna to be calibrated, the amplitude of the microwave field to be measured, and the microwave frequency includes: judging whether the antenna to be calibrated meets the far-field condition based on the antenna parameters; if the far-field condition is met, calculating the splitting frequency interval based on the amplitude of the microwave field to be measured and the microwave frequency; when the splitting frequency interval is greater than twice the EIT peak linewidth, determining whether the antenna to be calibrated meets the calibration condition, the twice the EIT peak linewidth being obtained by the action of the coupled light and the detection light in the antenna gain calibration system based on Rydberg atoms.

[0057] When far-field conditions are met, the amplitude and frequency of the microwave field to be measured can be used to calculate the AT splitting frequency interval. AT splitting refers to the splitting of the atomic energy levels in Rydberg atoms due to the microwave field. The splitting frequency interval can be used to calibrate the antenna gain.

[0058] The split frequency interval refers to the interval between two frequency components in a microwave signal.

[0059] The antenna is considered to meet the calibration requirements when the calculated splitting frequency interval is greater than twice the EIT peak linewidth. The EIT (Electromagnetically Induced Transparency) peak linewidth, derived from the interaction of coupling light and probe light in a Rydberg atom-based system, is a parameter related to the atomic energy level splitting.

[0060] Specifically, in antenna calibration, if the splitting frequency interval is greater than twice the EIT peak linewidth, this means that the splitting is significant enough to be used for accurate gain calibration.

[0061] In determining whether the antenna to be calibrated meets the far-field condition based on the antenna parameters, the following formula may be used for determination, where R is the distance between the antenna to be calibrated and the alkali metal atom gas cell:

[0062]

[0063] where D is the size of the antenna to be calibrated and λ is the microwave wavelength.

[0064] Therefore, the far-field condition is considered to be achieved when the distance between the antenna and the alkali metal atom gas cell is greater than or equal to the square of the maximum dimension of the antenna divided by twice the microwave wavelength.

[0065] In the process of calculating the split frequency interval according to the amplitude of the microwave field to be measured and the microwave frequency, the split frequency interval is calculated according to the following formula:

[0066] It can be seen that in this implementation, information such as antenna parameters, microwave field amplitude and frequency is used to determine whether the antenna to be calibrated meets the far-field conditions and calibration conditions. Combined with the characteristic parameters of the EIT effect, the accuracy and reliability of the antenna gain calibration are ensured.

[0067] In a possible example, when the antenna to be calibrated meets the calibration conditions, antenna gain calibration is performed on the antenna to be calibrated according to a preset calibration antenna, including: obtaining a first microwave frequency and multiple preset field strength values; obtaining a first relationship curve of the preset calibration antenna at the first microwave frequency according to a preset formula, the multiple preset field strength values, the first microwave frequency, and preset antenna parameters of the preset calibration antenna, wherein the first relationship curve includes a fitted frequency difference of the preset calibration antenna; obtaining a second relationship curve of the antenna to be calibrated at the first microwave frequency according to the multiple preset field strength values, the first microwave frequency, and the antenna parameters of the antenna to be calibrated, wherein the second relationship curve includes a fitted frequency difference of the antenna to be calibrated; obtaining a difference range of the antenna to be calibrated according to the first relationship curve and the second relationship curve; and performing antenna gain calibration on the antenna to be calibrated according to the difference range.

[0068] The preset formula is as follows:

[0069]

[0070] The horizontal axis x is the actual set microwave frequency, the vertical axis y is the frequency difference obtained by fitting, f0 is the resonant frequency, and δ0 is the frequency difference at resonance, that is, the frequency difference at the antenna resonant frequency.

[0071] The first microwave frequency is a specific microwave frequency, which is usually selected within the operating frequency range of the antenna and is not limited here.

[0072] The preset multiple field strength values ​​are a series of pre-set microwave field strength values, which will be used in the subsequent antenna calibration process.

[0073] The first relationship curve shows the relationship between the fitting frequency difference of the preset calibration antenna and the actually set microwave frequency under different field strength values.

[0074] The second relationship curve is obtained based on actual parameters of the antenna to be calibrated, and is used for comparison with the first relationship curve.

[0075] The difference range can help determine whether the gain of the antenna to be calibrated is within an acceptable range.

[0076] Furthermore, based on the difference range, necessary adjustments can be made to the antenna to be calibrated so that its gain matches the gain of the preset calibration antenna. This may involve adjusting the antenna's physical structure or electrical characteristics or using a gain calibration factor for software compensation.

[0077] For reference Figure 3 , Figure 3The following diagram shows the relationship between AT splitting and microwave frequency at different microwave powers. This curve is used to calibrate the gain of the antenna being calibrated. The following process is described in the figure: a range of field strengths (0.5 V / m, 0.7 V / m, 1 V / m, and 1.2 V / m) and frequencies (approximately 2.35 GHz to 2.45 GHz) are selected. At each selected field strength, the AT splitting spacing is measured at the corresponding frequency. The AT splitting distance refers to the energy level splitting in the Rydberg atomic structure due to the microwave electric field, resulting in two peaks in the spectrum. The frequency difference between these two peaks is the AT splitting distance. An oscilloscope is used to record the AT splitting images corresponding to different frequencies at each field strength. These images are then fitted using software to calculate the splitting frequency. The corresponding data points between the calculated splitting frequency and the set microwave frequency are plotted as a scatter plot and fitted using a quadratic function or other appropriate mathematical model to produce a relationship curve. The fit is evaluated using the R value or other statistical indicators during the fitting to ensure that the curve accurately reflects the data point trend. The relationship curves at different field strengths are compared to determine the gain difference range of the antenna to be calibrated at different frequencies. Based on this difference range, the antenna to be calibrated is gain-calibrated to match the gain of the preset calibration antenna at different frequencies. The set microwave field strength is modified and the above measurement process is repeated until 3-4 sets of data points are measured to ensure the accuracy and reliability of the calibration. The curves in the figure show the trend of the AT splitting distance as a function of frequency at different field strengths. These trends can be used to evaluate and calibrate antenna performance. In this way, the gain of the antenna to be calibrated can be accurately calibrated within a certain frequency range.

[0078] It can be seen that, in this embodiment, the use of the preset formula and multiple field strength values ​​can accurately analyze and adjust the gain of the antenna to be calibrated, ensuring its performance and reliability in practical applications.

[0079] In a possible example, obtaining a second relationship curve of the antenna to be calibrated at the first microwave frequency based on the preset multiple field strength values, the first microwave frequency, and the antenna parameters of the antenna to be calibrated includes: obtaining a resonant frequency range corresponding to the Rydberg state; determining at least one resonant frequency based on the resonant frequency range; obtaining multiple data points based on the preset multiple field strength values, the at least one resonant frequency, and the EIT peak linewidth corresponding to each resonant frequency, wherein the EIT peak linewidth is obtained by the action of coupled light and detection light in the antenna gain calibration system based on Rydberg atoms; and drawing the second relationship curve based on the multiple data points.

[0080] The resonant frequency range corresponding to the Rydberg state refers to the frequency range that includes the resonant frequencies that can excite the Rydberg state. Frequencies within this range are used in subsequent resonant frequency selection and data point calculations. Rydberg states occur when atomic electrons are excited to very high energy levels, which are very sensitive to electromagnetic fields.

[0081] In determining at least one resonant frequency based on the resonant frequency range, for each selected resonant frequency, the EIT peak linewidth corresponding to each resonant frequency is calculated in combination with multiple preset field strength values. The EIT peak linewidth is derived from the interaction of coupling light and probe light in an antenna gain calibration system based on Rydberg atoms. Specifically, the EIT effect is a transparent window created by Rydberg atoms under the combined action of coupling light and probe light, the width of which is the EIT peak linewidth.

[0082] A second relationship curve is plotted using each resonant frequency, corresponding field strength, and EIT peak linewidth as data points. This curve reflects the response of the antenna to be calibrated at different field strengths and resonant frequencies. The abscissa of the second relationship curve is typically the actual microwave frequency or field strength, while the ordinate is the fitted frequency difference or other relevant parameters.

[0083] It can be seen that this embodiment ensures that the calibration process is based on accurate physical measurements and can reflect the performance of the antenna under actual working conditions.

[0084] For example, if the AT splitting of an uncalibrated antenna measured at a specific microwave detuning point falls outside the theoretical curve, it can be determined that the antenna's gain at that frequency requires calibration. This point-by-point measurement method allows for calibration of microwave antennas over a wide range. Two laser beams, transmitted via optical fiber, interact with each other within an atomic probe filled with cesium vapor in a microwave darkroom. This excites the cesium atoms within the glass chamber to Rydberg states, resulting in electromagnetically induced transparency (EIT). A photodetector detects the 852nm laser light transmitted through a 509nm optical fiber, observing two peaks of varying heights, known as EIT peaks. By varying the optical power of the two laser beams as they pass through the chamber, the linewidth of the EIT peak can be altered. Once the linewidth is optimized, experimental conditions are achieved, allowing calibration of the antenna under test to proceed. As the microwave electric field intensity decreases, the separation between the EIT peaks decreases. When the microwave field intensity is very low, the AT splitting is so small that the spectral representation of the EIT peak cannot be distinguished. In other words, the minimum measurement value for the system is when the AT splitting frequency interval is twice the EIT peak linewidth. Therefore, the microwave field intensity set during the experiment should not be too low. When there is detuning between the microwave electric field and the resonant transition frequency of the Rydberg state, the two peaks of the AT splitting signal become dissymmetrical and shift relative to each other. The greater the detuning, the greater the shift of the AT peak, allowing the antenna to be calibrated over a wide range. To clearly identify the frequency at which the antenna gain needs to be calibrated, microwave frequency-AT splitting curves should be measured at three to four field intensities. Generally, several field intensities with intervals of 0.5 V / m and 0.7 V / m or higher are selected for calibration. Each calibration covers the antenna gain within a ±100 MHz range around the resonant frequency of the selected Rydberg state. The microwave electric field received by the atom probe can be calculated using the far-field formula. The microwave system is controlled by a computer program connected via an Ethernet cable. The microwave field amplitude and frequency output by the microwave source can be input into the interface. The program can calculate the theoretical output power of the horn antenna. The microwave power meter detects and compares the actual output power with the theoretical value, and the PID module adjusts the actual microwave output power until it matches the theoretical value. A fixed microwave field intensity is set in the program, and the microwave output frequency is continuously changed near the resonant frequency. Specifically, within the resonant frequency range of ±20MHz, 1 / 8 of the EIT peak line width is selected as the step size; within the resonant frequency range of ±20MHz to ±50MHz, 1 / 4 of the EIT peak line width is selected as the step size; within the resonant frequency range of ±50MHz to ±100MHz, 1 / 2 of the EIT peak line width is selected as the step size. The AT splitting image observed on the oscilloscope is recorded, and the AT splitting situation is fitted in the software. The calculated splitting frequency can obtain a corresponding data point between the set microwave frequency and the splitting frequency.Based on this, several data points can be measured, and then the microwave field intensity is set to be modified and repeated until 3-4 groups of data points are measured. The measured groups of data points are plotted in a scatter plot and fitted using a quadratic function to obtain a fitting curve, and the fitting effect can be evaluated by the R value during fitting. After obtaining a good fitting result, observe the offset of the scatter points relative to the curve. If a certain frequency measurement point can be observed above or below its fitting curve in multiple curves, it can be determined that at this frequency, the gain of the antenna to be measured is larger or smaller than the nominal value. By repeating the above method, the gain of the antenna to be measured within a certain frequency range can be accurately calibrated. The polarization directions of the two light beams in the alkali metal atom gas chamber 23 must be the same so that the peak value of the transmission peak can be the highest.

[0085] It should be noted that, in each of the above-mentioned embodiments, there is not necessarily a certain order between the above-mentioned steps. A person skilled in the art can understand, based on the description of the embodiments of this application, that in different embodiments, the above-mentioned steps may have different execution orders, that is, they may be executed in parallel, or may be executed interchangeably, etc.

[0086] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing related hardware through a computer program. The program can be stored in a computer-readable storage medium, and when executed, the program can include the processes in the above-described method embodiments. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0087] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. An antenna gain calibration system based on Rydberg atoms, characterized in that: include: A frequency stabilization module (31) for detecting a light source, an optical path module (32), a microwave module (35), a signal detection module (33) and a darkroom (34); The frequency stabilization module of the detection light source is used to stabilize the laser wavelength of the semiconductor laser in the optical path module, so that the laser wavelength is suitable for the preparation of the Rydberg EIT signal; The optical path module is used to generate coupling light and the detection light; the coupling light and the detection light are irradiated against the alkali metal atom gas chamber in the dark room, and the alkali metal atoms in the alkali metal atom gas chamber are excited to the Rydberg state through two-stage excitation to obtain the EIT signal required for the experiment; The microwave module is used to generate and transmit microwave signals to control the microwave electric field in the experiment, and the microwave electric field affects the interaction between the detection light and the coupling light; The signal detection module is used to convert the detection light into an electrical signal, and the electrical signal is collected by an oscilloscope in the signal detection module to analyze the electrical signal.

2. The system according to claim 1, characterized in that The darkroom also includes an antenna to be calibrated, and the antenna to be calibrated is also located in the microwave module.

3. The system according to claim 1, characterized in that The frequency stabilization module of the detection light source includes a first optical fiber coupling head, an optical fiber electro-optic modulator, a second optical fiber coupling head, a polarization beam splitter prism, a λ / 4 glass plate, an ultra-stable cavity, a charge coupled device camera, a photodetector, a third optical fiber coupling head, a mixer, a first signal generator, a second signal generator, and a proportional integral differential circuit.

4. The system according to claim 3, characterized in that The semiconductor laser emits a laser as the detection light, and the laser is coupled into a polarization-maintaining single-mode optical fiber through the first optical fiber coupling head; the laser is phase-modulated in the optical fiber electro-optic modulator by a sinusoidal signal generated by the second signal generator to obtain a modulated laser; the modulated laser enters a preset space through the second optical fiber coupling head, the modulated laser is completely reflected by the polarization beam splitter prism, and the modulated laser after reflection enters the ultra-stable cavity through the λ / 4 glass plate; The first part of the light corresponding to the reflected laser passes through the ultra-stable cavity and is captured by the charge-coupled device camera and the photodetector for monitoring the detection light signal; the second part of the light corresponding to the reflected laser is reflected in the ultra-stable cavity, passes through the λ / 4 glass again, changes the polarization direction, transmits through the polarization beam splitter prism, and is converted into an electrical signal by the photodetector; the electrical signal and the sinusoidal signal generated by the first signal generator are demodulated in the mixer to obtain an error signal; the error signal is input to the proportional-integral-differential circuit to generate a feedback signal, and the feedback signal is transmitted to the semiconductor laser to achieve long-term stabilization of the laser wavelength.

5. The system according to claim 1, characterized in that The optical path module includes the semiconductor laser, the frequency-doubled laser, the fourth optical fiber coupling head, the fifth optical fiber coupling head, the wavelength meter, the sixth optical fiber coupling head, and the seventh optical fiber coupling head; the frequency-doubled laser is used to generate the required coupling light; the seed light before frequency-doubled is transmitted to the wavelength meter through the fifth optical fiber coupling head to monitor its wavelength; The laser light emitted by the semiconductor laser is transmitted to the wavelength meter through the fourth optical fiber coupling head to monitor its wavelength; The frequency-doubled coupled light enters the single-mode optical fiber for transmission via the sixth optical fiber coupling head; the laser light emitted by the semiconductor laser enters the single-mode optical fiber for transmission via the seventh optical fiber coupling head.

6. The system according to claim 1, characterized in that The microwave module includes a computer device, a microwave signal source, a power amplifier and an antenna to be calibrated; the computer device calculates and controls the microwave signal source to emit the microwave signal; the microwave signal is amplified by the power amplifier and then transmitted to the antenna to be calibrated to emit the microwave electric field.

7. A method for calibrating antenna gain based on Rydberg atoms, implemented based on the system according to any one of claims 1 to 6, characterized in that: include: Obtain antenna parameters of the antenna to be calibrated; Obtaining the amplitude and frequency of the microwave field to be measured; Determining whether the antenna to be calibrated meets a calibration condition according to the antenna parameters of the antenna to be calibrated, the amplitude of the microwave field to be measured, and the microwave frequency; When the antenna to be calibrated meets the calibration condition, antenna gain calibration is performed on the antenna to be calibrated according to a preset calibration antenna.

8. The method according to claim 7, characterized in that Judging whether the antenna to be calibrated meets a calibration condition according to the antenna parameters of the antenna to be calibrated, the amplitude of the microwave field to be measured, and the microwave frequency, includes: According to the antenna parameters, determining whether the antenna to be calibrated meets the far-field condition; If the far-field condition is met, the AT (Aulter-Towns) splitting frequency interval of the EIT spectrum is calculated according to the amplitude of the microwave field to be measured and the microwave frequency; When the AT split frequency interval is greater than twice the EIT peak line width, it is determined whether the antenna to be calibrated meets the calibration condition, and the twice the EIT peak line width is obtained by performing Gaussian function fitting on the EIT spectrum signal.

9. The method according to claim 7, characterized in that: When the antenna to be calibrated meets the calibration condition, antenna gain calibration is performed on the antenna to be calibrated according to a preset calibration antenna, including: Acquiring a first microwave frequency and a plurality of preset field strength values; According to a preset formula, the preset multiple field strength values, the first microwave frequency and the preset antenna parameters of the preset calibration antenna, a first relationship curve of the preset calibration antenna at the first microwave frequency is obtained, wherein the first relationship curve includes a fitting frequency difference of the preset calibration antenna; According to the preset multiple field strength values, the first microwave frequency and the antenna parameter of the antenna to be calibrated, a second relationship curve of the antenna to be calibrated at the first microwave frequency is obtained, wherein the second relationship curve includes a fitting frequency difference of the antenna to be calibrated; Obtaining a difference range of the antenna to be calibrated according to the first relationship curve and the second relationship curve; According to the difference range, antenna gain calibration is performed on the antenna to be calibrated.

10. The method according to claim 9, characterized in that Obtaining a second relationship curve of the antenna to be calibrated at the first microwave frequency according to the preset multiple field strength values, the first microwave frequency and the antenna parameter of the antenna to be calibrated, including: Obtain the resonant frequency range corresponding to the Rydberg state; determining at least one resonant frequency according to the resonant frequency range; Obtaining a plurality of data points according to the plurality of preset field strength values, the at least one resonance frequency, and the EIT peak line width corresponding to each resonance frequency, wherein the EIT peak line width is obtained by the coupling light and the detection light in the antenna gain calibration system based on Rydberg atoms; The second relationship curve is obtained by drawing based on the multiple data points.

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