Radio frequency standard field generation system and method based on near-field beam forming

Abstract

The invention relates to the field of electromagnetic field technology and radio frequency signal testing, in particular to a radio frequency standard field generation system and method based on near-field beam forming, and the system comprises a control unit, a radio frequency signal generation unit, a radio frequency field control unit and a broadband radiation antenna array. The control unit carries a near-field electromagnetic wave synthesis mathematical model and is used for receiving a target field type setting requirement and calculating excitation amplitude and injection compensation phase required by each radiation unit configured in the broadband radiation antenna array; the radio frequency signal generation unit comprises a pulse modulation laser source and a plurality of semiconductor radiation units and is used for generating high-power programmable radio frequency signals; the radio frequency field control unit comprises an optical delay line and an FPGA matrix and is used for performing amplitude and phase regulation and control on the high-power programmable radio frequency signal output by the radio frequency signal generation unit; and the broadband radiation antenna array is used for receiving the regulated radio frequency signal and radiating the regulated radio frequency signal to the near-field space of the darkroom, and a target field pattern is formed through multi-unit electric field vector superposition.

Description

Technical Field

[0001] This application relates to the fields of electromagnetic field technology and radio frequency signal testing, and more specifically, to a radio frequency standard field generation system and method based on near-field beamforming. Background Technology

[0002] In key application scenarios such as high-power radio frequency signal equipment testing, electromagnetic compatibility (EMC) testing, radar target simulation, and electromagnetic countermeasures testing, the core requirement is to construct a known, controllable, and uniform or highly concentrated standard electromagnetic field environment within a specific area. Traditional testing methods rely on far-field (Fraunhofer zone) conditions, which require the testing distance to meet certain requirements. (Where D is the radiation aperture size and λ is the wavelength). However, in practical applications, the test distance required to meet this condition is often as high as hundreds of meters to kilometers. Due to the physical constraints of the laboratory darkroom space, far-field test conditions are difficult to achieve, forming a core contradiction between "limited darkroom space" and "necessary far-field conditions," which seriously restricts the indoor conduct of related test work.

[0003] To address the aforementioned spatial constraints, near-field testing technology has gradually gained attention. However, existing near-field testing systems suffer from several technical bottlenecks: Firstly, traditional systems lack sufficient phase control precision, have poor amplitude adjustment flexibility, and lack accurate near-field electromagnetic synthesis models. This makes it difficult to achieve accurate field distribution synthesis in high-power scenarios in the near-field region, and thus fails to generate traceable, highly uniform, or precisely focused RF standard fields. Secondly, in existing RF signal testing environments, especially in high-power near-field environments, the accuracy of field strength values ​​typically relies on field-calibrated sensors. Measurement results are mostly relative values, lacking a complete and closed metrological traceability chain from basic principle parameters such as power, phase, and distance to the final synthesized field strength. This makes it difficult to effectively guarantee the accuracy, consistency, and reproducibility of test results, preventing the formation of truly "measurable and traceable" standard fields, further hindering the development of high-precision quantitative testing technology. In summary, existing technologies have significant shortcomings in terms of spatial adaptability, field distribution synthesis accuracy, and metrological traceability. There is an urgent need for a new radio frequency standard field generation system and method to solve the problem of constructing high-power, high-precision, and traceable standard electromagnetic fields in near-field scenarios. Summary of the Invention

[0004] In view of this, this application provides a radio frequency standard field generation system and method based on near-field beamforming. Through high-precision multi-dimensional parameter control, and based on the near-field electromagnetic wave synthesis model, a programmable, high-power, uniformly field-strength radio frequency standard field or a high-energy-density focal point or other set radio frequency field is synthesized in the target area, solving the problem of accurate testing or experimentation of high-power radio frequency signal equipment in a limited space.

[0005] The technical solution provided in this application is as follows: In a first aspect, this application provides a radio frequency standard field generation system based on near-field beamforming, including a control unit, a radio frequency signal generation unit, a radio frequency field control unit, and a broadband radiating antenna array; The control unit is equipped with a pre-configured near-field electromagnetic wave synthesis mathematical model, which is used to receive the target field pattern setting requirements, calculate the excitation amplitude and injection compensation phase required for each radiating element configured in the broadband radiating antenna array, and generate corresponding control commands. The radio frequency signal generation unit includes a pulse-modulated laser source and multiple semiconductor radiation units; the pulse-modulated laser source is used to adjust the sub-pulse repetition rate and pulse width to excite the semiconductor radiation units to generate a high-power programmable radio frequency signal. The radio frequency field control unit includes an optical delay line and an FPGA matrix, which is used to receive control commands from the control unit and to perform amplitude and phase modulation on the high-power programmable radio frequency signal output by the radio frequency signal generation unit. The broadband radiating antenna array is used to receive high-power programmable radio frequency signals after modulation and radiate them into the near-field space of the anechoic chamber, forming a target field pattern through the superposition of multiple unit electric field vectors; the target field pattern includes a uniform field or a focal point position.

[0006] In one possible implementation, the control unit also integrates a near-field synthesis module, and the target field pattern setting requirements received by the control unit include a preset focus. The near-field synthesis module is used to calculate the distance from each radiating element to the preset focus based on a near-field focusing algorithm. distance , is represented as:

[0007] In the formula, R 0 indicates the specified focus. Location coordinates, r n Statement No. n The known position coordinates of each radiating element in space; Based on the distance Determine the required compensation phase for each radiating element. , is represented as:

[0008] In the formula, Indicates wave number; Based on the compensation phase, the signal phase of the corresponding radiating element is adjusted so that the signals of all radiating elements are at a preset focal point. The point where the power density reaches its maximum value is the focal point where the power is superimposed in phase.

[0009] In one possible implementation, the target field pattern setting requirement received by the control unit includes generating a uniform field in the target region; based on the near-field synthesis module integrated within the control unit, M sampling points are set within the set target region, and an optimal set of unit excitation parameters, including the injected radio frequency signal power of each radiating unit, is obtained by using an inversion algorithm with field strength uniformity as the objective function. A n and injection compensation phase ; The radio frequency field control unit is also used to generate a radio frequency field in a set target uniform region in response to the optimization results.

[0010] In one possible implementation, the field strength uniformity is characterized as the field strength variance at the sampling points and the power source traceability constraint. The inversion algorithm takes the field strength variance at the sampling points and the power source traceability constraint as the objective function, adopts a hybrid solution strategy of conjugate gradient and genetic algorithm, outputs the optimal excitation parameters of each radiating unit within a preset time, and ensures that the residual between the synthetic field and the desired standard field, and the output uncertainty in the focal point or uniform region, all meet the preset requirements.

[0011] In one possible implementation, the near-field electromagnetic wave synthesis mathematical model is expressed as:

[0012] In the formula, Represents any point P The total electric field intensity, For the first n The incentive magnitude of each unit, To inject compensation phase; For the first n Units to target point P The distance, where, R p Indicates the target point P Location coordinates, r n Indicates the first n The known position coordinates of each radiating element in space; This represents the radiation pattern function of each radiating element. , Indicates the first n azimuth and elevation angles in a spherical coordinate system with each radiating element as the origin. t Represents the instantaneous phase of the signal, where Angular frequency, t For time, Indicates wave number.

[0013] In one possible implementation, the radio frequency signal generation unit further includes a microchannel cooling module connected to each semiconductor radiation unit for cooling the high-power units in the system.

[0014] In one possible implementation, the pulse-modulated laser source is used to output optical pulses with high repetition rate, programmable pulse width, and phase delay better than ps, and achieves picosecond-level stepping via an optical delay line; the semiconductor and radiation unit is used to receive the optical pulses and output transient radio frequency fields with peak power ≥80kW / channel, and each semiconductor radiation unit integrates a current probe and a B-dot for online measurement of photoelectric conversion efficiency.

[0015] In one possible implementation, the optical delay line is used to directly trace back to the National Institute of Metrology or other time references via a femtosecond optical frequency comb, so as to control the phase uncertainty to meet preset requirements.

[0016] Secondly, this application provides a method for generating a radio frequency standard field based on near-field beamforming, applied to a radio frequency standard field generation system as described in any of the first aspects, the method comprising: Receive a target field shape setting request, wherein the target field shape includes a focal point or a target uniform region. Based on the mathematical model of near-field electromagnetic wave synthesis, combined with the near-field focusing algorithm or the near-field uniform field optimization algorithm, the required excitation amplitude and injection compensation phase of each radiating element are calculated. A high-power programmable radio frequency signal is generated by exciting multiple semiconductor radiating units using a pulse-modulated laser source. Amplitude and phase modulation of RF signals in each channel are achieved based on optical delay lines and FPGA matrices. Each radiating element of the broadband radiating antenna array receives the modulated radio frequency signal, radiates it into the near-field space of the anechoic chamber, and synthesizes the target field pattern through the superposition of electric field vectors.

[0017] In one possible implementation, before synthesizing the target field type, the method further includes: tracing and verifying the power meters and time-frequency devices used in the system, including tracing at the basic parameter level, tracing at the field strength synthesis level, and tracing at the field strength verification level. Based on the source-tracing parameters and radiation unit pattern function, the predicted field strength is calculated using a near-field electromagnetic wave synthesis mathematical model. The field strength E was measured using a traceable standard field strength probe at a reference point in the darkroom. measured Comparison E measured With field strength prediction value E calculatedWhen the field strength deviation is within the preset uncertainty range, the model calculation value is used as the standard value of the field strength in the entire field to synthesize the target field shape.

[0018] Compared with the prior art, the above-mentioned technical solution of this application has the following beneficial effects: This application, within a limited space, utilizes high-precision multi-dimensional parameter control and a near-field electromagnetic wave synthesis model to synthesize a programmable, high-power, uniformly strong radio frequency standard field, a high-energy-density focal point, or other pre-defined radio frequency field in the target area. This solves the problem of accurately testing or experimenting with high-power radio frequency signal equipment within a confined space. Furthermore, this application provides a calculable, predictable, and measurably traceable high-power near-field radio frequency standard field. The electromagnetic field environment generated by this system not only allows for direct calculation and prediction of field strength values ​​through precise physical models but also enables rigorous metrological methods to trace its origin to national or International System of Units (SI), ensuring the accuracy, consistency, and authority of the field strength values. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a radio frequency standard field generation system based on near-field beamforming, provided in Embodiment 1 of this application.

[0020] Figure 2 This is a flowchart of a radio frequency standard field generation method based on near-field beamforming, provided in Embodiment 2 of this application. Detailed Implementation

[0021] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] Example 1 See Figure 1 This is a schematic diagram of a radio frequency standard field generation system based on near-field beamforming, provided in Embodiment 1 of this application. Figure 1 As shown, the system specifically includes a control unit 1, a radio frequency signal generation unit 2, a radio frequency field control unit 3, a broadband radiating antenna array 4, and a near-field synthesis module 5.

[0023] The aforementioned broadband radiating antenna array 4 includes multiple radiating elements. Each radiating element can independently receive amplitude / phase modulation commands from the radio frequency field control unit 3 and radiate the high-power radio frequency signal optimized by the radio frequency signal generation unit 2 into the anechoic chamber space. The radiation pattern function of each radiating element is shown below. It is known. Among them, and Indicates the first n The azimuth and elevation angles in a spherical coordinate system with each radiation unit as the origin define the observation point. P Relative to the direction of this element. Optionally, the above-mentioned broadband radiating antenna array adopts a composite structure combining logarithmic periodicity and slot coupling, with a voltage standing wave ratio (VSWR) < 2.0 in the operating frequency range of 1-18 GHz. Each radiating element is orthogonally mounted to achieve independent dual-polarization control, with cross-polarization isolation > 25 dB.

[0024] The aforementioned near-field synthesis module 5, built into the aforementioned control unit 1, is used to calculate the excitation amplitude and phase of each radiating element based on the near-field electromagnetic wave synthesis mathematical model. The aforementioned control unit 1 generates corresponding control commands based on the calculation results to control the aforementioned radio frequency field control unit 3 to independently and precisely modulate the amplitude and phase of the radio frequency signals in each channel, thereby generating a programmable radio frequency standard field or focusing point in the near-field region. The aforementioned near-field electromagnetic wave synthesis mathematical model is expressed as follows:

[0025] In the formula, This represents the total electric field intensity at any point P. For the first n The incentive magnitude of each unit, To inject compensation phase, For the first n Units to target point P The precise distance, of which, R p Indicates the target point P Location coordinates, r n Indicates the first n The known position coordinates of each radiating element in space. This represents the radiation pattern function of each radiating element. t Represents the instantaneous phase of the signal, where Angular frequency, t For time, Indicates wave number.

[0026] This application utilizes a precise near-field model, eliminating the need for far-field conditions, and enables high-precision radio frequency signal testing—traditionally requiring far-field conditions—to be performed within a confined, dark chamber. The functions and specific implementations of each unit in the aforementioned radio frequency standard field generation system are described in detail below with reference to specific embodiments.

[0027] In a practical application scenario, based on the radio frequency standard field generation system described in this application, a focal point and a uniform target area can be preset. The core of near-field focusing is to maximize the field strength through the in-phase superposition of electromagnetic waves; that is, the radio frequency signals radiated simultaneously by multiple radiating elements need to be focused at the preset focal point. Only when the radiating elements arrive synchronously and are in phase can phase cancellation be avoided, thus forming a focused point of concentrated energy. However, due to the different installation positions of each radiating element in the antenna array, their distance to the focal point varies. The spatial distances between objects will inevitably differ, and the propagation phase of electromagnetic waves is directly related to the propagation distance. Therefore, after receiving the target field pattern setting requirement, the control unit 1 of this application calculates the distance from each radiation element to the focal point based on the near-field focusing algorithm configured within the control unit 1. precise distance , is represented as:

[0028] In the formula, R 0 indicates the specified focus. Location coordinates, r n Indicates the first n The known position coordinates of each radiating element in space. Further, based on the aforementioned distance... Determine the required injection compensation phase for each radiation element. , is represented as:

[0029] In the formula, Indicates wave number.

[0030] Based on the above-mentioned injection compensation phase, the signal phase of each radiating element is further adjusted, so that the signals of all radiating elements are superimposed in phase at the focal point, and the peak power density is synthesized at the focal point, achieving a high energy density effect with a focusing gain of >30dB.

[0031] Specifically, the aforementioned radio frequency signal generation unit 2 includes a pulse-modulated laser source with adjustable repetition rate and pulse width, and multiple semiconductor radiation units. The aforementioned pulse-modulated laser source is specifically used to output optical pulses with a repetition rate, programmable pulse width, and phase delay ≤10ps, and achieves picosecond-level steps via optical delay lines, which are used to excite each semiconductor radiation unit to generate the required high-power radio frequency signal.

[0032] The aforementioned semiconductor radiation unit employs photoconductive switch arrays such as SiC, AlGaN, or diamond to receive the aforementioned optical pulses and output transient radio frequency power with a peak power ≥80kW / channel. Each unit integrates a current probe and a B-dot to achieve online measurement of photoelectric conversion efficiency.

[0033] Furthermore, each semiconductor radiating unit is connected to a microfluidic cooling module for efficient cooling of the high-power units in the system, ensuring stable operation under high-power conditions. The RF field control unit 3 is equipped with an optical delay line and an FPGA matrix for independent control of each high-power programmable RF signal. The broadband radiating antenna array consists of four broadband antenna elements (radiating units). Ultimately, each high-power programmable RF signal is synchronously radiated into the anechoic chamber space through its corresponding broadband antenna element, ensuring a time synchronization error of ≤20ps.

[0034] This application achieves a time synchronization accuracy better than 20ps by combining optical delay and FPGA digital phase shifting. Combined with independent amplitude control, it allows dynamic programming of frequency, phase, amplitude, and field pattern (4D parameters), enabling accurate reproduction and rapid switching of complex electromagnetic environments. Employing semiconductor devices and efficient cooling technology, it achieves a single-channel peak power ≥80kW and a multi-channel combined peak power exceeding 300kW, providing extreme testing conditions for the device under test. Through near-field optimization algorithms, it can generate a uniform field with a field strength uniformity better than 10% or a high-energy-density focusing point with a gain exceeding 30dB in the target area, providing a traceable and reproducible standard field environment.

[0035] For the defined target uniform region, the near-field synthesis module 5 is used to set M sampling points in the target uniform region based on the near-field uniform field optimization algorithm. Using field intensity uniformity as the objective function, an inversion algorithm is used to solve for a set of optimal unit excitation parameters. This ensures that the field strength fluctuation in the target area is less than 15%. Optionally, the above-mentioned field strength uniformity can be characterized as field strength variance, etc. The above-mentioned inversion algorithm includes, but is not limited to, genetic algorithm, particle swarm algorithm, etc., and those skilled in the art can set it according to the actual situation.

[0036] For example, in some embodiments, the particle swarm optimization algorithm is used to calculate a set of optimal unit excitation parameters by using the minimization of field strength variance as the objective function and iteratively in reverse. .in, A n This represents the injected radio frequency signal power of each radiating element. This indicates the compensation phase. The aforementioned RF field control unit 3, in response to the optimization results, generates an RF field within the defined target uniform region. Probe scanning tests show that the field strength uniformity meets the technical requirement of ±10%.

[0037] In other embodiments, the aforementioned field strength uniformity can also be characterized as the field strength variance at sampling points and power source traceability constraints. The aforementioned inversion algorithm uses the field strength variance at sampling points and power source traceability constraints as objective functions, employing a hybrid solution strategy of conjugate gradient and genetic algorithm. It outputs the optimal excitation parameters for each radiating element within a preset time, ensuring that the residual between the synthesized field and the desired standard field, as well as the output uncertainty within the focal point or uniform region, meet preset requirements. Optionally, the preset time can be 200 ms, meaning that the optimal excitation parameters are provided within 200 ms, ensuring that the residual between the synthesized field and the desired standard field is <0.5 dB, and the output uncertainty U is <5% (k=2), thus meeting the preset requirements.

[0038] Furthermore, before generating a uniform field, this application first sends the power meter and time-frequency equipment used in the system to the National Institute of Metrology for calibration, tracing the power meter and time-frequency equipment back to national standards to ensure the accuracy and reliability of the field strength value from the source to the final value. In the embodiments of this application, the tracing of the power meter and time-frequency equipment includes basic parameter-level tracing, field strength synthesis-level tracing, and field strength verification-level tracing.

[0039] The aforementioned basic parameter-level tracing includes, but is not limited to, RF signal power tracing, phase tracing, and geometric position tracing. Specifically, for the injected RF signal power of each radiating element... A n The system uses calibrated directional couplers and power meters for real-time monitoring. The power meters need to be periodically sent to national metrology institutes (such as NIM or NIST) or authorized institutions for calibration according to national power standards, ensuring that power values ​​are accurately traceable to national standards. This is for high-precision phase control units. Φ n To ensure accuracy, the system utilizes a high-precision time-frequency counter for calibration. This counter is traceable to the national time and frequency standard, allowing time synchronization accuracy to be controlled to better than 20 ps, ​​and ultimately traceable to the basic unit of time, the second. At the location of the radiating unit... r n and target point location R p For measurement, the system uses a calibrated laser tracker or total station. These measuring instruments also need to be sent to a metrology institution periodically for calibration based on length standards to ensure the accuracy of the spatial distance d between the radiating element and the target point. np It can be traced back to the basic unit of length, the meter.

[0040] The aforementioned field strength synthesis level tracing includes the basic parameters that have been traced as described above. Compared with the radiation pattern function of each radiation element that has been precisely measured and modeled in advance These parameters are combined and substituted into the mathematical model for near-field electromagnetic wave synthesis. For any point P in the anechoic chamber, the total electric field strength Etotal(P) is a deterministic value determined by these precisely known input parameters, which can be directly solved by a computer, realizing the calculability of the field strength. At the same time, before the system performs any field synthesis operation such as focusing or uniform field synthesis, the complete field distribution of the target area can be pre-simulated and calculated using this mathematical model, thereby accurately predicting the magnitude and uniformity of the field strength and providing a reliable basis for subsequent field synthesis.

[0041] The aforementioned field strength verification-level traceability, as a crucial step in achieving final field strength measurement traceability, involves selecting one or more reference points in an anechoic chamber during system debugging or periodic calibration. The field strength at these points is measured using a standard electric field probe traceable to the National Institute of Metrology (NIM) of China, yielding the measured field strength value E. measured Simultaneously, based on all the fundamental parameters of the current operation, the system calculates the predicted field strength E at the reference point using a near-field electromagnetic wave synthesis mathematical model. calculated Then, by comparing E measured With E calculated The deviation is used to verify and fine-tune the overall synthesis accuracy of the system. When the deviation is within the allowable uncertainty range (e.g., ±10%), it proves that the entire synthesis chain of the system is accurate and reliable. At this point, the field strength value at any location in the near-field region of the anechoic chamber where no probe is placed can be obtained from the model-calculated value E. calculated This authoritative characterization ultimately enables indirect tracing of the field strength values ​​in the near-field region of the entire anechoic chamber.

[0042] For example, the field strength measurement value E is obtained using a standard field strength probe traceable to the national field strength standard. measured =200V / m. The system controller determines the current injection voltage based on the voltage level. Using parameters such as E, the electric field strength at the reference point is calculated as E. calculated =195V / m. The deviation between the two is approximately 0.3dB, which is within the system's nominal uncertainty range of ±0.6dB, and the traceability verification is passed. Subsequently, without the need for individual measurements at each location in the uniform field, the model-calculated values ​​can be used as standard values ​​for the field strength at each point, efficiently providing a high-precision calibration basis for the device under test with traceable values ​​and reproducible results.

[0043] Based on this, this application establishes, for the first time, a complete metrological traceability path under near-field, high-power conditions. By tracing the fundamental parameters to national standards and utilizing a validated and accurate physical model as a "transfer bridge," the final synthesized field strength value has a traceable basis, filling a gap in this field. This system generates not only an electromagnetic environment but also a calculable, predictable, and authoritative standard, providing a reliable benchmark for scientific research and industrial testing.

[0044] Example 2 Embodiment 2 of this application provides a method for generating a radio frequency standard field based on near-field beamforming, applied to the radio frequency standard field generation system provided in Embodiment 1. See also... Figure 2 The flowchart below illustrates a method for generating a radio frequency standard field based on near-field beamforming, as provided in this application. Figure 2 As shown, the specific implementation steps of the above method include: Step 101: Receive the target field shape setting requirements. The target field shape includes a focal point or a target uniform region.

[0045] Step 102: Based on the near-field electromagnetic wave synthesis mathematical model, and combined with the near-field focusing algorithm or the near-field uniform field optimization algorithm, calculate the required excitation amplitude and injection compensation phase for each radiating element.

[0046] Step 103: Excite multiple semiconductor radiation units with a pulse-modulated laser source to generate a high-power programmable radio frequency signal.

[0047] Step 104: Based on the optical delay line and FPGA matrix, the amplitude and phase of the RF signals in each channel are modulated.

[0048] Step 105: Each radiating element of the broadband radiating antenna array receives the modulated radio frequency signal, radiates it into the near-field space of the anechoic chamber, and superimposes the electric field vectors.

[0049] Step 106: Conduct source tracing verification of the power meters and time-frequency equipment used in the system, including source tracing at the basic parameter level, source tracing at the field strength synthesis level, and source tracing at the field strength verification level.

[0050] Step 107: Based on the basic parameters and radiation unit pattern function after source tracing, calculate the predicted field strength value through the near-field electromagnetic wave synthesis mathematical model.

[0051] Step 108: Measure the field strength E at the reference point in the anechoic chamber using a traceable standard field strength probe. measured Comparison E measured With field strength prediction value E calculated .

[0052] Step 109: When the field strength deviation is within the preset uncertainty range, the model calculation value is used as the standard value of the field strength in the entire field.

[0053] It should be noted that the specific technical details of Embodiment 2 of this application can be found in conjunction with the relevant description of Embodiment 1 of this application, and Embodiment 2 of this application will not be described in detail.

[0054] Compared with the prior art, the technical solution provided in Embodiment 2 of this application has the following beneficial effects: This application, within a limited space, utilizes high-precision multi-dimensional parameter control and a near-field electromagnetic wave synthesis model to synthesize a programmable, high-power, uniformly strong radio frequency standard field, a high-energy-density focal point, or other pre-defined radio frequency field in the target area. This solves the problem of accurately testing or experimenting with high-power radio frequency signal equipment within a confined space. Furthermore, this application provides a calculable, predictable, and measurably traceable high-power near-field radio frequency standard field. The electromagnetic field environment generated by this system not only allows for direct calculation and prediction of field strength values ​​through precise physical models but also enables rigorous metrological methods to trace its origin to national or International System of Units (SI), ensuring the accuracy, consistency, and authority of the field strength values.

[0055] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A near-field beamforming based radio frequency standard field generation system, characterized in that, The control unit, the radio frequency signal generation unit, the radio frequency field control unit and the wideband radiation antenna array are included. The control unit is equipped with a pre-configured near-field electromagnetic wave synthesis mathematical model, and is used for receiving a target field type setting requirement, calculating excitation amplitudes and injected compensation phases required by each radiation unit arranged in the wideband radiation antenna array, and generating corresponding control instructions. The radio frequency signal generation unit includes a pulse modulation laser source and a plurality of semiconductor radiation units. The radio frequency field control unit includes an optical delay line and an FPGA matrix, and is used for receiving the control instructions of the control unit, and performing amplitude and phase regulation on the high-power programmable radio frequency signals output by the radio frequency signal generation unit. The wideband radiation antenna array is used for receiving the high-power programmable radio frequency signals after regulation and radiating to a near-field space of a darkroom, and forming a target field type through multi-unit electric field vector superposition.

2. A near-field beamforming based radio frequency standard field generating system according to claim 1, characterized in that, The control unit is also integrated with a near-field synthesis module, and the target field pattern setting requirement received by the control unit includes a preset focal point The near-field synthesis module is used for calculating the distance of each radiation unit to the preset focal point based on a near-field focusing algorithm , which is represented as: wherein R 0 denotes the position coordinate of the specified focus r n the expression n the known position coordinate of the respective radiation unit in space; based on the distance the required compensation phase for each radiation unit is derived is expressed as​ In the formula, denotes the wave number; Based on the compensation phase, the signal phase of the corresponding radiation unit is adjusted, so that the signals of all the radiation units are in-phase superimposed at the preset focal point to synthesize a focal point with maximum peak power density.

3. The near-field beamforming based radio frequency standard field generating system of claim 1, wherein, The target field pattern setting requirement received by the control unit includes generating a uniform field in a target area; based on the near-field synthesis module integrated in the control unit, M sampling points are set in the target area, the field strength uniformity is used as an objective function, and a set of optimal unit excitation parameters including the injection radio frequency signal power of each radiation unit is solved by using an inversion algorithm for reverse optimization A n and injection compensation phase ​ The radio frequency field control unit is also used for generating a radio frequency field in a set target uniform area in response to an optimization result.

4. A near-field beamforming based radio frequency standard field generating system according to claim 3, characterized in that, The field strength uniformity is characterized by a sampling point field strength variance and a power traceability constraint.

5. The near-field beamforming based radio frequency standard field generating system of claim 1, wherein, The inversion algorithm takes the sampling point field strength variance and the power traceability constraint as a target function, adopts a mixed solution strategy of a conjugate gradient and a genetic algorithm, outputs optimal excitation parameters of each radiation unit within a preset time, and makes the residual error of a synthesized field and an expected standard field and the output uncertainty in a focal point or a uniform area meet preset requirements. wherein denotes the total electric field strength at an arbitrary point P , denotes the excitation amplitude of the n th unit, denotes the injection compensation phase; denotes the distance of the n th unit to the target point P , wherein R p denotes the position coordinates of the target point P , r n denotes the known position coordinates of the n th radiating unit in space; denotes the directional diagram function of the respective radiating unit, , denotes the azimuth and elevation angle in a spherical coordinate system with the n th radiating unit as origin, t denotes the instantaneous phase of the signal, wherein is the angular frequency, t is the time, denotes the wave number.

6. The near-field beamforming based radio frequency standard field generating system of claim 1, wherein, The near-field electromagnetic wave synthesis mathematical model is represented as:

7. The near-field beamforming based radio frequency standard field generating system of claim 1, wherein, The radio frequency signal generation unit further includes a micro-channel cooling module connected with each semiconductor radiation unit, and is used for cooling high-power units in the system.

8. The near-field beamforming based radio frequency standard field generating system of claim 1, wherein, The pulse modulation laser source is used for outputting optical pulses with programmable repetition frequency and pulse width and phase delay better than ps level, and realizing picosecond level stepping through the optical delay line.

9. A method for generating a radio frequency standard field based on near field beamforming, applied to the radio frequency standard field generating system according to any one of claims 1-8, characterized in that, The optical delay line is used for directly tracing to the national institute of metrology or other time reference through a femtosecond optical frequency comb, so as to control the phase uncertainty to meet preset requirements. The method includes: Receiving a target field type setting requirement, the target field type including a focal point or a target uniform area Based on the near-field electromagnetic wave synthesis mathematical model, combining a near-field focusing algorithm or a near-field uniform field optimization algorithm, calculating excitation amplitudes and injected compensation phases required by each radiation unit Generating high-power programmable radio frequency signals through a pulse modulation laser source exciting a plurality of semiconductor radiation units Based on the optical delay line and the FPGA matrix, regulating amplitudes and phases of radio frequency signals of each channel Each radiation unit of the wideband radiation antenna array receives the regulated radio frequency signals, radiates to a near-field space of a darkroom, and synthesizes a target field type through electric field vector superposition.

10. The method of claim 9, wherein, Before synthesizing the target field pattern, the method further comprises: verifying the power meter and time-frequency device used by the system through traceability, including basic parameter level traceability, field strength synthesis level traceability and field strength verification level traceability; Based on the traceable basic parameters and the radiation element directional diagram function, a field strength prediction value is calculated through a near-field electromagnetic wave synthesis mathematical model; and The field strength E is measured at the reference point in the darkroom using a standard field strength probe that is traceable measured , the comparison E measured with the predicted value of the field strength E calculated ; when the field strength deviation is within the preset uncertainty range, the model calculation value is taken as the full-field field strength standard value.

Images