Simulated Doppler frequency shift and arrival angle measuring device and method based on Rydberg atoms

Abstract

The invention discloses an analog Doppler frequency shift and arrival angle measuring device and method based on Rydberg atoms, and in the aspect of DFS measurement, the device performs beat frequency on two signals to obtain an intermediate frequency signal frequency which is a DFS value; the device calculates the AOA of the echo signal by measuring the phase difference of the echo signal at two different positions in the cesium gas pool. According to the invention, simultaneous measurement of DFS and AOA can be realized, and the scheme has the advantages of simple structure, stable system, multifunction, anti-interference and the like, and has great application prospects in electronic reconnaissance and countermeasure systems and the like.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology, and particularly relates to a device and method for simulating Doppler frequency shift and angle of arrival measurement based on Rydberg atoms. Background Art

[0002] Two parameters, Doppler frequency shift (DFS) and angle of arrival (AOA), can be used to measure the speed, azimuth, and movement direction of a target. Therefore, DFS and AOA measurements are widely used in modern wireless communication, radar, and electronic warfare systems. However, in traditional microwave signal measurement and electronic countermeasures, two independent analog processing hardware systems are required to measure DFS and AOA respectively, resulting in a complex and expensive system. Moreover, traditional electronics measurement methods face technical defects such as narrow bandwidth and susceptibility to electromagnetic interference. With the rapid development of quantum technology, frequency measurement systems based on Rydberg atom technology have been developed, which have advantages such as low loss, large bandwidth, and electromagnetic interference resistance. At the same time, the simultaneous measurement of Doppler frequency shift and angle of arrival has received great attention from domestic and foreign research institutions. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a device and method for simulating Doppler frequency shift and angle of arrival measurement based on Rydberg atoms. In terms of DFS measurement, the intermediate frequency signal obtained by beating two signals by the device is the DFS value; the device calculates the AOA of the echo signal by measuring the phase difference of the echo signal at two different positions in the cesium gas cell. The present invention can realize the simultaneous measurement of DFS and AOA, and the proposed scheme has the advantages of simple structure, stable system, multi-function, anti-interference, etc., and has great application prospects in systems such as electronic reconnaissance and countermeasures.

[0004] The technical solutions adopted by the present invention to solve its technical problems are as follows:

[0005] A device for simulating Doppler frequency shift and angle of arrival measurement based on Rydberg atoms, comprising a beam splitter prism PBS 1 and PBS 2 , dichroic mirror DM 1 to DM 6 , cesium atomic gas cell, 852 nm laser, 509 nm laser, photodetector PD 1 and PD 2 and spatial optical path discrete devices;

[0006] The 852 nm probe light output by the 852 nm laser is split into two optical paths by the beam splitter prism PBS 1 and then, one of the 852 nm probe lights passes through the cesium atomic gas cell from position 1 and is detected by the photodetector PD1 Received, another 852 nm probe beam passes through dichroic mirror DM 1 , DM 2 , DM 3 Refracted and transmitted through the cesium atomic cell from position 2 and received by photodetector PD 2 Received;

[0007] The 509 nm coupled light output by the 509 nm laser passes through beam splitter prism PBS 2 and is divided into two optical paths. One of the 509 nm coupled light beams passes through dichroic mirror DM 6 Refracted, passes through the cesium atomic cell from position 1 towards the 852 nm probe beam, and the other 509 nm coupled light beam passes through dichroic mirror DM 5 Refracted and passes through the cesium atomic cell from position 2 towards the other 852 nm probe beam. The two probe beams and the two coupled light beams are coupled to each other in the cesium atomic cell respectively, and the distance between the two optical paths is 18.5 mm.

[0008] A method for simulating Doppler frequency shift and angle of arrival measurement based on Rydberg atoms, comprising the following steps:

[0009] Step 1: When measuring the Doppler frequency shift DFS, two probe beams passing through the cesium atomic cell are respectively monitored by two photodetectors, and the output electrical signals are sent to an oscilloscope and a spectrum analyzer. The two photodetectors respectively collect the two probe light signals in the cesium atomic cell affected by the difference frequency signal, and the average value of the frequencies of the two probe light beams is the DFS of the measured system;

[0010] Step 2: When measuring the angle of arrival AOA, the relative positions of the echo signal to the two coupled light beams in the cesium atomic cell need to be determined; during the measurement, the transmitted signal is in a fixed position, directly above the cell and stationary; the horn of the echo signal is fixed to a rotating arm and can be rotated to different incident directions. As the rotation angle of the echo signal changes, the phase difference between the echo signal and the two coupled light beams in the cesium atomic cell will change, and the AOA of the echo signal can be deduced from the phase difference.

[0011] Preferably, step 1 is specifically:

[0012] In the Doppler frequency shift DFS measurement, the frequency of the transmitted signal is fixed at 15.29394 GHz. The DFS value is related to the intermediate frequency signal generated after the beat of the transmitted signal and the echo signal. The intermediate frequency signal generated after the beat of the two signals is positive, resulting in the inability to distinguish the positive and negative directions of the measured DFS. In order to distinguish the positive and negative directions of DFS, the frequency of the transmitted signal is set to be offset by 1 MHz, and the frequency of the echo signal is 15.29394 GHz + △f. At this time, the frequency generated after the beat of the transmitted signal and the echo signal is 1 MHz + △f. The two signal fields act on the cesium atomic gas cell simultaneously to drive the 62S 1 / 2 -62P 1 / 2 Rydberg state transition; the relative frequency zero point of the DFS measurement value is set to 1 MHz, and the DFS value changes from -100 kHz to +100 kHz in steps of 10 kHz; the waveform of the output intermediate frequency signal is collected by an oscilloscope, and the DFS spectrum information is analyzed by a spectrum analyzer to obtain the measurement result and error of DFS. In the range of 100 kHz to +100 kHz, the measurement error of DFS is between -0.4 Hz and 0.4 Hz.

[0013] Preferably, the specific step 2 is as follows:

[0014] In the arrival angle AOA measurement, the frequency of the transmitted signal is fixed at 15.29394 GHz, and the frequency of the echo signal is fixed at 15.293945 GHz. The intermediate frequency after the beat of the two signals is 5 kHz; the two beat signals are phase-shifted, and the period is 200 μs;

[0015] The measurement angle of the horn antenna of the echo signal starts from -30° and is measured to 35° by a high-precision angle measuring instrument with an accuracy of 0.05° in steps of 5°; the phase difference corresponding to each angle is measured, and the corresponding AOA is calculated.

[0016] Preferably, the principle of the method for measuring the analog Doppler frequency shift and arrival angle based on Rydberg atoms includes the following steps:

[0017] Step 3: In the DFS measurement, a radio frequency source applies a radio frequency field resonant with the Rydberg atom transition to simulate the transmitted signal, and the frequency of the transmitted signal is f tm , the transmitted signal field is E tm = |E tm |cos(2πf tm t + φ tm ), where E tm , f tm , φ tmrespectively represent the amplitude, frequency, and phase of the transmitted signal field; another RF source applies an RF field with the same polarization as the transmitted signal field and a frequency difference of Δf to simulate the echo signal, and the frequency of the echo signal is f ec , and the echo signal field is E ec = |E ec |cos(2πf ec t + φ ec ), where E ec , f ec , φ ec respectively represent the amplitude, frequency, and phase of the echo signal field;

[0018] Step 4: To measure the Doppler frequency shift using the heterodyne method, the transmitted signal |E tm | and the echo signal |E ec | need to act on the Rydberg atoms together; the frequency difference between the transmitted signal and the echo signal is Δf = |f tm - f ec |, and the initial phase difference is Δφ = φ tm - φ ec ; the echo signal field with frequency detuning is used as the target object to be detected. The transmitted signal and the echo signal interfere with each other in the Rydberg atom cell to generate a time-varying beat signal, which is expressed as:

[0019]

[0020] Step 5: If the transmitted signal and the echo signal acting on the atoms satisfy Δf << (f tm + f ec ) / 2 and |E ec | << |E tm |, the result of the actual electric field sensed by the atoms is written as:

[0021]

[0022] Step 6: When the frequency of the microwave field acting on the Rydberg atoms resonates with the Rydberg state, the resonant interaction causes an AT splitting in the EIT, thereby reducing the probe transmittance T probe below the EIT peak, and the magnitude of the AT splitting is proportional to the intensity of the applied microwave field; since the actual electric field |E atom | sensed by the atoms changes with time, the AT splitting interval changes with time; when locking the frequency of the coupling laser, the function of the probe transmittance with respect to time is:

[0023]

[0024] Step 7: The DFS of the microwave signal is the frequency of the intermediate frequency term. The phase of the DFS directly corresponds to the relative phase between the transmitted signal and the echo signal. The DFS corresponds to the frequency difference between the transmitted signal and the echo signal, that is, the frequency of the intermediate frequency signal after the two signals are beat is the DFS, and the DFS is obtained through Equation (3):

[0025] f DFS = f IF = Δf = |f tm - f ec | (4)

[0026] where f DFS represents the Doppler frequency shift, f IF represents the intermediate frequency signal frequency. By optically detecting the Rydberg atoms, the DFS can be detected and the DFS signal can be directly read out on a spectrum analyzer;

[0027] Step 8: To reduce the error in measuring the DFS, the entire measurement system includes two detection optical paths. The two intermediate frequency signal frequencies f IF1 and f IF2 are received by these two detection optical paths respectively. The two intermediate frequency signals both come from the beat of the same transmitted signal and echo signal. Then the optical signals carrying the intermediate frequency information are input into two photodetectors, and output to the spectrum analyzer through the photodetectors to respectively read out the values of f IF1 and f IF2 ; At this time, to eliminate the DFS error caused by the system, the DFS is obtained from the following formula:

[0028] f DFS = (f IF1 + f IF2 ) / 2 (5)

[0029] Step 9: To measure the AOA, the phases of the echo signal at two different positions in the cesium atomic cell need to be determined; From the above, the echo signal field is expressed as E ec = |E ec |cos(2πf ec t + φ ec ); Once the phases of the echo signal at two different positions in the cesium atomic cell are determined, the relationship between the AOA and the phase difference between the two positions can be calculated; When the echo signal is considered as a plane wave, the relationship between the arrival angle θ and the phase φ is obtained from Equation (6):

[0030] Δφ 2,1 = φ 2 - φ 1 ≈ kdsin(θ) (6)

[0031] At this time, the arrival angle θ is:

[0032]

[0033] where d is the distance between two light beams in the gas cell, and φ 2,1 is the phase difference between two different positions, k = 2π / λ, and λ is the wavelength of the echo signal;

[0034] If the connecting line between two positions in the gas cell is not perpendicular to the line determining the measurement angle θ, the phase difference relationship between the two positions is:

[0035]

[0036] The arrival angle θ is calculated as:

[0037]

[0038] where h is the height difference between two positions in the cesium atomic gas cell.

[0039] A computer program that causes a computer to execute the above method for simulating Doppler frequency shift and arrival angle measurement.

[0040] An electronic device, comprising: a processor and a memory; the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory so that the electronic device executes the above method for simulating Doppler frequency shift and arrival angle measurement.

[0041] A computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the above method for simulating Doppler frequency shift and arrival angle measurement is implemented.

[0042] A chip, comprising: a processor, configured to call and run a computer program from a memory, so that a device installed with the chip executes the above method for simulating Doppler frequency shift and arrival angle measurement.

[0043] A computer program product, the computer program product includes a computer storage medium, the computer storage medium stores a computer program, the computer program includes instructions that can be executed by at least one processor, and when the instructions are executed by the at least one processor, the above method for simulating Doppler frequency shift and arrival angle measurement is implemented.

[0044] The beneficial effects of the present invention are as follows:

[0045] The present invention can achieve simultaneous measurement of DFS and AOA, and the proposed solution has a simple structure, stable system, and has advantages such as multifunction and anti-interference, and has great application prospects in systems such as electronic reconnaissance and countermeasure. Description of the Drawings

[0046] Figure 1 This is the schematic diagram of DFS and AOA measurement based on Rydberg atoms in the present invention;

[0047] Figure 2 This is the schematic diagram of the relative position and phase of the coupling beams in the cesium atomic cell;

[0048] Figure 3 This is the schematic diagram of the measurement results and measurement errors of DFS from -100 kHz to 100 kHz;

[0049] Figure 4 This is the schematic diagram of the relative phase of the echo signal arriving at the two beams in the cell;

[0050] Figure 5 This is the schematic diagram of the measurement results and measurement errors of AOA from -30° to 35°. Specific embodiments

[0051] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0052] The technical solution adopted by the present invention is: The device includes a polarization beam splitter (PBS), a dichroic mirror (DM), a cesium atomic cell (Cs vapor cell), an 852 nm laser, a 509 nm laser, a photodetector (PD), and various spatially separated optical path devices.

[0053] The probe light with a wavelength of 852 nm and the coupling light with a wavelength of 509 nm generated by the lasers propagate in opposite directions. The two laser beams are respectively split into two beams after passing through the polarization beam splitter, and then pass through a cesium atomic cell filled with cesium atoms in opposite directions at two different positions through the reflection of the dichroic mirror, interacting with the atomic medium. The radio frequency emission signal and the echo signal act on the cell simultaneously, and the transmission spectrum of the probe laser after exiting the cell is captured and analyzed by two PDs.

[0054] The present invention includes the following steps when working:

[0055] (1) The 852 nm probe light output by the 852 nm laser is split into two optical paths after passing through the PBS 1 One of the 852 nm probe light beams passes through the cesium atomic cell from position 1 and is received by the PD 1 The other 852 nm probe light beam passes through the DM 1 、DM 2 、DM 3 refracts and passes through the cesium atomic cell from position 2 and is received by the PD 2

[0056] (2) The 509 nm coupling light output by the 509 nm laser is split into two optical paths after passing through the PBS 2 One of the 509 nm coupling light beams passes through the DM​6 Refraction. One beam of 852 nm probe light passes through the cesium atomic gas cell from position 1 in the opposite direction of the probe light, and another beam of 509 nm coupling light passes through the DM 5 Refraction. Another beam of 852 nm probe light passes through the cesium atomic gas cell from position 2 in the opposite direction of the other beam of 852 nm probe light. The two beams of probe light and the two beams of coupling light are coupled with each other in the cesium atomic gas cell respectively, and the distance between the two optical paths is 18.5 mm.

[0057] (3) In the DFS measurement, the two probe beams passing through the gas cell are monitored by two photodetectors, and the output electrical signals are sent to an oscilloscope and a spectrum analyzer. The two photodetectors respectively collect the two probe light signals in the gas cell affected by the difference frequency signal. The average value of the frequencies of the two probe lights is the DFS of the measured system.

[0058] (4) In the AOA measurement, the relative positions of the echo signal to the two coupling beams in the gas cell need to be determined. During the measurement, the transmitted signal is in a fixed position, directly above the gas cell and stationary. The horn of the echo signal is fixed to a rotating arm and can be rotated to different incident directions. As the rotation angle of the echo signal changes, the phase difference between the echo signal and the two coupling beams in the gas cell will change. The AOA of the echo signal in the system can be deduced from the phase difference.

[0059] The principle of the present invention:

[0060] In the DFS measurement, a radio frequency source applies a radio frequency field resonant with the Rydberg atom transition to simulate the transmitted signal (the frequency of the transmitted signal is f tm ), and the transmitted signal field is E tm = |E tm |cos(2πf tm t + φ tm ), where E tm , f tm , φ tm respectively represent the amplitude, frequency and phase of the transmitted signal field; another radio frequency source applies a radio frequency field with the same polarization as the transmitted signal field and a frequency difference of Δf to simulate the echo signal (the frequency of the echo signal is f ec ), and the echo signal field is E ec = |E ec |cos(2πf ec t + φ ec ), where E ec , f ec , φ ec respectively represent the amplitude, frequency and phase of the echo signal field. Since the frequency of the transmitted signal is the same as the Rydberg atom resonance frequency, this results in the EIT / AT effect in the Rydberg atoms demodulating the echo signal field with the same polarization as the transmitted signal field. Using the heterodyne method to measure the Doppler frequency shift requires the transmitted signal |E tm | and the echo signal |Eec |Act on the Rydberg atom together. The frequency difference between the emission signal and the echo signal is Δf = |f tm -f ec |, and the initial phase difference is Δφ = φ tm -φ ec . The echo signal field with frequency detuning is used as the target object to be detected. The emission signal and the echo signal interfere with each other in the Rydberg atomic cell to generate a time-varying beat signal, which is expressed as:

[0061]

[0062] The response of the atom to the magnitude of this changing electric field can be read out by detecting the transmission amplitude of the probe laser at the resonant frequency. If the emission signal and the echo signal acting on the atom satisfy Δf << (f tm +f ec ) / 2 and |E ec | << |E tm |, the result of the actual electric field sensed by the atom can be written as:

[0063]

[0064] When the frequency of the microwave field acting on the Rydberg atom resonates with the Rydberg state, the resonant interaction causes EIT to undergo an AT splitting, thereby reducing the probe transmittance (T probe ) below the EIT peak, and the magnitude of the AT splitting is proportional to the intensity of the applied microwave field. Since the actual electric field |E atom | sensed by the atom changes with time, the AT splitting interval changes with time. When the coupling laser frequency is locked, the function of the probe transmittance with time is:

[0065]

[0066] The DFS of the microwave signal is the frequency of the intermediate frequency term. The phase of the DFS directly corresponds to the relative phase between the emission signal and the echo signal. The DFS corresponds to the frequency difference between the emission signal and the echo signal, that is, the frequency of the intermediate frequency signal after the two signals beat is the DFS. The DFS can be obtained from equation (3):

[0067] f DFS =f IF =Δf = |f tm -f ec | (4)

[0068] In the formula, f DFS represents the Doppler shift, f IF represents the intermediate frequency signal frequency. By optically detecting the Rydberg atom, the DFS can be detected and the DFS signal can be directly read out on the spectrum analyzer.

[0069] However, if the DFS value is only obtained from Equation (4), there may be errors in the measured DFS. To reduce the error of measuring DFS, the entire measurement system includes two probe light paths, and two intermediate frequency signal frequencies f IF1 and f IF2 are received by these two probe light paths respectively. Both intermediate frequency signals come from the beat frequency of the same transmitted signal and echo signal. Then the optical signals carrying intermediate frequency information are input into two photodetectors, and output to the spectrum analyzer through the photodetectors to read out the values of f IF1 and f IF2 respectively. At this time, to eliminate the DFS error caused by the system, DFS can be obtained from the following formula:

[0070] f DFS =(f IF1 +f IF2 ) / 2 (5)

[0071] Next, to measure the AOA, the phases of the echo signal at two different positions in the cesium gas cell need to be determined. From the above, the echo signal field is expressed as E ec =|E ec |cos(2πf ec t + φ ec ). Once the phases of the echo signal at two different positions in the gas cell are determined, the relationship between the AOA and the phase difference between the two positions can be calculated by the formula. When the echo signal is considered as a plane wave, the relationship between the arrival angle θ and the phase φ is obtained from Equation (6):

[0072] △φ 2,1 =φ 2 -φ 1 ≈kdsin(θ) (6)

[0073] At this time, the arrival angle θ is:

[0074]

[0075] where d in the formula is the distance between the two light beams in the gas cell, φ 2,1 is the phase difference between two different positions, k = 2π / λ, and λ is the wavelength of the echo signal. The above expression assumes that the line connecting two different positions in the gas cell is perpendicular to the line of the measured angle θ. If the line connecting the two positions in the gas cell is not perpendicular to the line of the determined measured angle θ, the phase difference relationship between the two positions is:

[0076]

[0077] The arrival angle θ is calculated as:

[0078]

[0079] where h is defined as the height difference between two positions in the gas cell. Formulas (6)-(9) are applicable to relating the phase difference between two positions on a plane to the AOA, where it is assumed that the AOA is defined on a plane orthogonal to the propagation of the probing laser.

[0080] Example:

[0081] In this example, the device includes: a horn antenna connected to a radio frequency source, a polarization beam splitter (PBS), a dichroic mirror (DM), a cesium vapor cell, an 852 nm laser, a 509 nm laser, a photodetector (PD), and various spatially optical path discrete devices. The probing light with a wavelength of 852 nm and the coupling light with a wavelength of 509 nm generated by the lasers propagate towards each other. The two laser beams are respectively split into two beams after passing through the polarization beam splitter, and are reflected by the dichroic mirror and pass through a cesium vapor cell filled with cesium atoms in two different positions in opposite directions, interacting with the atomic medium. At the same time, microwave signals are sent by applying two horn antennas, and the transmission spectra of the probing laser after exiting are captured and analyzed by two PDs.

[0082] Step 1: The 852 nm probing laser and the 509 nm coupling laser are respectively split into two beams after passing through the polarization beam splitter, and pass through the cesium gas cell in opposite directions at two positions. The 852 nm laser is locked to the D2 absorption line of cesium atoms at 6S 1 / 2 (F = 4)-6P 3 / 2 (F = 4, 5). The 509 nm laser locks its frequency to 6P 3 / 2 (F = 4, 5)-62S 1 / 2 by means of EIT spectroscopy and a subsequent servo system. The two laser beams of 852 nm and 509 nm pass through the cesium vapor cell in a counter-propagating collinear manner to realize two EIT spectra. The selection of the beam direction is to ensure that the probing laser and the coupling laser are counter-propagating at two positions in the gas cell. Among them, a cesium atom cubic gas cell with a length, width, and height of 30 mm each is used for mixing. The spot diameters of the probing light and the coupling light for the atomic antenna are about 300 μm, and the light intensities are 258 μW and 60 mW respectively. After the two signal sources are synchronized with a 10 MHz clock, they respectively simulate the emission signal microwave field and the echo signal microwave field. The emission signal field and the echo signal field frequencies act on the Rydberg atomic state transition in near resonance at the same time, and the intensity of the emission field is much greater than that of the echo field. The outputs of the two signal sources are connected to two standard gain horn antennas through RF cables, and the microwave polarization direction is parallel to the polarization directions of the probing light and the coupling light. The 852 nm probing light collects the optical signal through a low-noise balanced detector with a bandwidth of 5 MHz, and the electrical signal of the detector is analyzed by connecting it to an oscilloscope or a spectrum analyzer.

[0083] Step 2: In the DFS measurement, the frequency of the transmitted signal is fixed at 15.29394 GHz. The DFS value is related to the intermediate frequency signal generated after the beat of the transmitted signal and the echo signal. The intermediate frequency signal generated after the beat of the two signals is positive, which results in the inability to distinguish the positive and negative directions of the measured DFS. In order to distinguish the positive and negative directions of DFS, the frequency of the transmitted signal is set to be offset by 1 MHz, and the frequency of the echo signal is 15.29394 GHz + Δf. At this time, the frequency generated after the beat of the transmitted signal and the echo signal is 1 MHz + Δf. The two signal fields act on the gas cell simultaneously to drive the 62S 1 / 2 -62P 1 / 2 Rydberg state transition. A concept of relative frequency zero point is introduced into the experiment so that the direction of DFS can be distinguished. The relative frequency zero point of the DFS measurement value is set to 1 MHz, and the DFS value changes from -100 kHz to +100 kHz in steps of 10 kHz. The waveform of the output intermediate frequency signal is collected by an oscilloscope, and the DFS spectrum information is analyzed by a spectrum analyzer to obtain the measurement results and errors of DFS as Figure 3 shown. In the range of 100 kHz to +100 kHz, the measurement error of DFS is between -0.4 Hz and 0.4 Hz.

[0084] Step 3: In the AOA measurement. The frequency of the transmitted signal is fixed at 15.29394 GHz, and the frequency of the echo signal is fixed at 15.293945 GHz. The intermediate frequency after the beat of the two signals is 5 kHz. For the beat signal of the set incident angle θ, it is detected by two photodetectors and displayed on the oscilloscope as Figure 4 shown. The phase shift of the two beat signals is due to the different positions of the two coupled optical paths in the gas cell, and its period is 200 μs (the intermediate frequency used in the experiment is 5 kHz).

[0085] Step 4: The measurement angle of the horn antenna of the echo signal starts from -30° and is measured by a high-precision angle measuring instrument with an accuracy of 0.05° in steps of 5° up to 35°. The phase difference corresponding to each angle is measured, and the corresponding AOA is calculated. The schematic Figure 5 shows the average value of the data after each angle corresponding to AOA in the range of -30° to 35° is measured and calculated three times. The specific values and errors of AOA measurement in the range of -30° to 35° are as Figure 5 shown. The measured AOA values are represented by solid squares, the measurement errors are plotted as vertical lines, and the average errors are plotted as solid circles. The error bars of the experimental results indicate that the measurement error of AOA in the range of -30° to 35° is within 0.5°.

[0086] In summary, the device and method for simulating Doppler frequency shift and angle of arrival measurement based on Rydberg atoms according to the present invention are simple and easy to implement, and can achieve high-precision simultaneous measurement of DFS and AOA within a large bandwidth. The present invention has great prospects in applications such as electronic warfare.

Claims

1. A simulated Doppler shift and arrival angle measurement device based on Rydberg atoms, characterized in that: It includes beam splitters PBS1 and PBS2, dichroic mirrors DM1 to DM6, cesium atom gas chamber, 852nm laser, 509nm laser, photodetectors PD1 and PD2, and spatial optical path discrete devices; The 852nm detection light output by the 852nm laser is divided into two light paths after passing through the beam splitter prism PBS1, wherein one beam of 852nm detection light passes through the cesium atom gas chamber from position 1 and is received by the photodetector PD1, and the other beam of 852nm detection light is refracted by the dichroic mirrors DM1, DM2, and DM3 and passes through the cesium atom gas chamber from position 2 and is received by the photodetector PD2; The 509nm coupling light output by the 509nm laser is divided into two light paths after passing through the beam splitter prism PBS2, wherein one beam of the 509nm coupling light is refracted by the dichroic mirror DM6, and passes through the cesium atomic gas chamber from position 1 in the direction opposite to the 852nm detection light, and the other beam of the 509nm coupling light is refracted by the dichroic mirror DM5, and passes through the cesium atomic gas chamber from position 2 in the direction opposite to the other beam of the 852nm detection light, and the two detection lights and the two coupling lights are respectively coupled with each other in the cesium atomic gas chamber, and the spacing between the two light paths is 18.5mm.

2. A method for measuring simulated Doppler frequency shift and arrival angle using the measuring device as claimed in claim 1, characterized in that: The steps include: Step 1: When measuring the Doppler frequency shift DFS, the two detection light beams passing through the cesium atomic gas chamber are monitored by two photodetectors respectively, and the output electrical signals are sent to the oscilloscope and spectrum analyzer. The two photodetectors respectively collect the two detection light signals affected by the difference frequency signal in the cesium atomic gas chamber. The average value of the two detection light frequencies is the DFS of the measured system. Step 2: When measuring the arrival angle AOA, the relative position of the echo signal to the two coupled light beams in the cesium atomic gas chamber needs to be determined; during the measurement, the transmitting signal is in a fixed position, located directly above the gas chamber and stationary; the horn of the echo signal is fixed on the rotating arm and can be rotated to different incident directions. As the rotation angle of the echo signal changes, the phase difference of the echo signal to the two coupled light beams in the cesium atomic gas chamber will change, and the AOA of the echo signal can be more accurately calculated through the phase difference.

3. A method for measuring simulated Doppler frequency shift and arrival angle according to claim 2, characterized in that: The step 1 is specifically as follows: In the Doppler shift DFS measurement, the frequency of the transmitting signal is fixed at 15.29394GHz. The DFS value is related to the intermediate frequency signal generated by the beat frequency of the transmitting signal and the echo signal. The intermediate frequency signal generated by the beat frequency of the two signals is a positive value, which makes the measured DFS unable to distinguish the positive and negative directions. In order to distinguish the positive and negative directions of DFS, the frequency of the transmitting signal is set to be offset by 1MHz, and the frequency of the echo signal is 15.29394GHz+△f. At this time, the frequency generated by the beat frequency of the transmitting signal and the echo signal is 1MHz+△f. The two signal fields act on the cesium atomic gas chamber at the same time, driving the 62S 1 / 2 -62P 1 / 2 Rydberg state transition; the relative frequency zero point of the DFS measurement value is set to 1MHz, and the DFS value changes from -100kHz to +100kHz in steps of 10kHz; the waveform of the output intermediate frequency signal is collected by an oscilloscope, and the DFS spectrum information is analyzed by a spectrum analyzer to obtain the measurement results and errors of DFS. In the range of 100kHz to +100kHz, the measurement error of DFS is between -0.4Hz and 0.4Hz.

4. A method for measuring simulated Doppler frequency shift and arrival angle according to claim 3, characterized in that: The step 2 is specifically as follows: In the arrival angle AOA measurement, the transmission signal frequency is fixed at 15.29394GHz, the echo signal frequency is fixed at 15.293945GHz, and the intermediate frequency after the two signals beat is 5kHz; the two beat tone signals are shifted in phase, and their period is 200μs; The measurement angle of the horn antenna of the echo signal starts from -30° and is measured to 35° in steps of 5° by a high-precision angle measuring instrument with an accuracy of 0.05°; the phase difference corresponding to each angle is measured and the corresponding AOA is calculated.

5. A method for measuring simulated Doppler frequency shift and arrival angle according to claim 4, characterized in that: The principle of the simulated Doppler frequency shift and arrival angle measurement method based on Rydberg atoms comprises the following steps: Step 3: In the DFS measurement, an RF source applies an RF field resonant with the Rydberg atomic transition to simulate the transmission signal with a frequency of f tm , the transmitted signal field is E tm =|E tm |cos(2πf tm t+φ tm ), where E tm 、f tm ,φ tm They represent the amplitude, frequency and phase of the transmitted signal field respectively; another RF source applies a RF field with the same polarization as the transmitted signal field and a frequency difference of △f to simulate the echo signal, and the echo signal frequency is f ec , the echo signal field is E ec =|E ec |cos(2πf ec t+φ ec ), where E ec 、f ec ,φ ec Respectively represent the amplitude, frequency and phase of the echo signal field; Step 4: Using heterodyne method to measure Doppler shift requires to convert the transmitted signal |E tm | and echo signal |E ec | act together on the Rydberg atom; the frequency difference between the transmitted signal and the echo signal is △f=|f tm -f ec |, the initial phase difference is △φ=φ tm -φ ec The frequency-detuned echo signal field is taken as the target object to be detected. The transmission signal and the echo signal interfere with each other in the Rydberg atomic gas chamber to produce a time-varying beat signal, which is expressed as: Step 5: If the transmission signal and the echo signal acting on the atom satisfy △f<<(f tm +f ec ) / 2 and |E ec |<<|E tm |, the result of the actual electric field felt by the atom is written as: Step 6: When the frequency of the microwave field acting on the Rydberg atom resonates with the Rydberg state, the resonant interaction causes the EIT to split by AT, thereby making the probe transmittance T probe The magnitude of the AT splitting is proportional to the strength of the applied microwave field; since atoms actually sense the electric field |E atom | changes with time, so the AT splitting interval changes with time; when the coupling laser frequency is locked, the function of the probe transmittance with time is: Step 7: The DFS of the microwave signal is the frequency of the intermediate frequency term. The phase of DFS directly corresponds to the relative phase between the transmitted signal and the echo signal. DFS corresponds to the frequency difference between the transmitted signal and the echo signal, that is, the frequency of the intermediate frequency signal after the two signals beat is DFS. DFS is obtained by equation (3): f DFS =f IF =△f=|f tm -f ec | (4) Where f DFS represents the Doppler frequency shift, f IF represents the intermediate signal frequency, by optical detection of Rydberg atoms DFS can be detected and the DFS signal can be directly read out on a spectrum analyzer; Step 8: In order to reduce the error of measuring DFS, the whole measurement system includes two detection beam paths and two intermediate frequency signal frequencies f IF1 and f IF2 The two intermediate frequency signals are received by the two detection optical paths respectively. Both of them come from the beat frequency of the same transmission signal and the echo signal. Then the optical signal with the intermediate frequency information is input into two photodetectors and output to the spectrum analyzer through the photodetectors to read out f IF1 and f IF2 value; at this time, in order to eliminate the DFS error caused by the system, DFS is obtained from the following formula: f DFS =(f IF1 +f IF2 ) / 2 (5) Step 9: To measure AOA, the phase of the echo signal at two different locations in the cesium atom gas cell needs to be determined; from the above, the echo signal field is represented by E ec =|E ec |cos(2πf ec t+φ ec ); Once the phase of the echo signal at two different positions in the cesium atomic gas chamber is determined, the relationship between the AOA and the phase difference between the two positions can be calculated; when the echo signal is considered as a plane wave, the relationship between the arrival angle θ and the phase φ is obtained by equation (6): △φ 2,1 =φ2-φ1≈kdsin(θ) (6) At this time, the angle of arrival θ is: where d is the distance between the two beams in the gas chamber, φ 2,1 is the phase difference between two different positions, k = 2π / λ, λ is the wavelength of the echo signal; If the line connecting two positions in the gas cell is not perpendicular to the line that determines the measured angle θ, the phase difference between the two positions is related by: The angle of arrival θ is calculated as: where h is the height difference between two positions in the cesium atom gas cell.

6. A computer program, characterized in that The computer program enables a computer to execute the method according to any one of claims 1 to 5.

7. An electronic device, characterized in that: include: Processor and memory; The memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the electronic device executes the method as claimed in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

9. A chip, characterized in that: include: A processor, configured to call and run a computer program from a memory, so that a device equipped with the chip executes a method as claimed in any one of claims 1 to 5.

10. A computer program product, characterized in that The computer program product comprises a computer storage medium storing a computer program, wherein the computer program comprises instructions executable by at least one processor, and when the instructions are executed by the at least one processor, the method according to any one of claims 1 to 5 is implemented.

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