Phase-free antenna measurement method and system and storage medium

Abstract

The invention discloses a phase-free antenna measurement method, a phase-free antenna measurement system and a storage medium. The phase-free antenna measurement method comprises the following steps: constructing a measurement system comprising an antenna to be measured, a measurement probe, a fixed auxiliary reference antenna and software defined radio; the probe is controlled to move and sample on the scanning plane, and the SDR synchronously collects receiving signals of the probe and the reference antenna; based on the frequency domain transformation result of the two paths of signals, the radiation field amplitude of each sampling point and the relative phase relative to the reference antenna are directly calculated through non-iterative operation, so that complete complex electric field distribution on the scanning plane is reconstructed; and finally, obtaining a far-field directional diagram through near-field-far-field transformation. The fixed reference antenna is introduced to serve as a phase reference, synchronous acquisition and direct calculation are achieved in combination with the SDR, the antenna radiation field can be rapidly and accurately recovered without direct phase measurement or complex iteration in the single scanning plane and single scanning process, and the method has the advantages of being simple in system, high in measurement efficiency and high in signal drift resistance.

Description

Technical Field

[0001] This invention relates to the field of antenna measurement technology, and in particular to a planar near-field antenna measurement method, system, and storage medium based on a reference signal that does not require direct phase measurement. Background Technology

[0002] With the development of wireless communication technology, active integrated devices (such as massive MIMO antennas and beamforming antennas) are increasingly widely used. Accurate measurement of the radiation characteristics of such devices is crucial to ensuring their performance. However, because the radio frequency links of these devices are usually not directly accessible, it is difficult to obtain phase information of their radiation field, posing a significant challenge to accurate measurement.

[0003] Existing phase-free measurement techniques mainly include holography and interferometry.

[0004] 1) Holographic methods (or indirect holographic methods) are based on combining the received signal with a known reference source and retrieving phase information in the spectral domain. However, this technique is susceptible to aliasing problems. Although off-axis techniques have partially overcome this, its application is usually limited to planar measurements, and the system complexity and cost are relatively high.

[0005] 2) Interferometry calculates the phase difference by measuring and combining power at different locations. Although its baseline is the same as that of holography, it does not require a direct reference antenna. However, this method relies on solving a set of linear equations, is sensitive to measurement errors, and the solution process may have stability and uniqueness issues.

[0006] Therefore, there is an urgent need in this field for an antenna measurement method that can quickly and accurately recover the amplitude and phase information of the radiation field in a single scan without increasing the complexity of the system. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing phaseless measurement technology and provide a phaseless antenna measurement method, system and storage medium to achieve single-scan planar phaseless antenna measurement that can accurately recover the amplitude and phase of the radiation field, and has high measurement efficiency and low system complexity.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A phaseless antenna measurement method includes the following steps: Step 1: Construct a measurement system, which includes an antenna under test, a measurement probe movable on a scanning plane, a fixed auxiliary reference antenna, and a software-defined radio with dual-channel synchronous reception capability; the auxiliary reference antenna is used to receive electromagnetic waves emitted by the antenna under test to provide a phase reference; the software-defined radio is used to synchronously acquire two signals.

[0009] Preferably, the sampling interval of the measuring probe on the scanning plane is no greater than half a working wavelength.

[0010] Step 2: Control the measurement probe to perform two-dimensional moving sampling on the scanning plane according to a preset sampling interval; at each sampling point, the software-defined radio synchronously collects and records the first signal received by the measurement probe and the second signal received by the auxiliary reference antenna.

[0011] Step 3: The software-defined radio or a connected computing device reconstructs the complex electric field distribution on the scanning plane through a non-iterative computation process based on the first signal and the second signal at each sampling point.

[0012] Specifically, the first signal and the second signal at each sampling point are subjected to frequency domain transformation to obtain the corresponding first spectrum and second spectrum; based on the first spectrum and the second spectrum, the radiation field amplitude of the antenna under test at each sampling point and its relative phase with the auxiliary reference antenna are calculated, thereby reconstructing the complete complex electric field distribution on the scanning plane; specifically including: The amplitude of the radiation field at the sampling point is determined based on the amplitude of the first spectrum. Calculate the complex ratio of the first spectrum to the second spectrum at a specific frequency, and directly determine the relative phase of the sampling point with respect to the auxiliary reference antenna based on the phase angle of the complex ratio; for example, the specific frequency is the peak frequency of the first spectrum and / or the second spectrum, especially the center operating frequency of the antenna under test.

[0013] The complex electric field distribution is constituted by the amplitude and relative phase of all sampling points.

[0014] Step 4: Based on the complex electric field distribution, obtain the far-field radiation pattern of the antenna under test through near-field-far-field transformation.

[0015] Specifically, the complex electric field distribution on the reconstructed scanning plane is used as input, and the far-field radiation pattern of the antenna under test is calculated using a near-field to far-field transformation algorithm.

[0016] Preferably, in step 1, the placement of the auxiliary reference antenna must meet at least one of the following conditions: 1) Maintain a distance of 18 to 22 operating wavelengths from the antenna under test. This distance is optimized to ensure that the auxiliary reference antenna receives a sufficiently strong reference signal while minimizing significant multiple reflection interference between it and the measurement probe and the antenna under test.

[0017] 2) Its location needs to be optimized. It must be located within the effective radiation area of ​​the antenna under test, while precisely avoiding the null points of the main lobe and side lobe of the radiation pattern, so as to ensure the stability and reliability of the reference signal.

[0018] 3) Its position must completely avoid the scanning plane of the measuring probe to prevent physical obstruction or electromagnetic interference to the field distribution within the scanning plane.

[0019] Preferably, a system calibration step is included before step 4: A standard gain antenna is used to replace the antenna under test. Two signals are acquired at the center point of the scanning plane. The calculated relative phase is used as the fixed phase offset of the system and is subtracted from the phase results of subsequent formal measurements to eliminate the error introduced by the inconsistency of the acquisition channels.

[0020] The present invention also provides a phaseless antenna measurement system for implementing the aforementioned phaseless antenna measurement method, the system comprising: Antenna under test; A measuring probe is configured to move on a scanning plane; A fixed auxiliary reference antenna; A software-defined radio having at least dual-channel synchronous reception capability for synchronously acquiring the received signals from the measurement probe and the auxiliary reference antenna; The signal processing unit is configured to perform the following operations: Based on the two synchronously acquired signals, the complex electric field distribution on the scanning plane is reconstructed through a non-iterative computation process; Perform a near-field to far-field transformation algorithm to generate a far-field radiation pattern.

[0021] In one embodiment, the specific steps of the signal processing unit reconstructing the complex electric field distribution include: Perform frequency domain transformation on the first signal and the second signal at each sampling point to obtain the first spectrum and the second spectrum; The amplitude of the radiation field at the sampling point is determined based on the amplitude of the first spectrum. Calculate the complex ratio of the first spectrum to the second spectrum at a specific frequency, and directly determine the relative phase of the sampling point with respect to the auxiliary reference antenna based on the phase angle of the complex ratio. The complex electric field distribution is constituted by the amplitude and relative phase of all sampling points.

[0022] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the signal processing steps in the phaseless antenna measurement method of the present invention.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) High efficiency with a single scan: Only one scanning plane and one scanning process are needed to simultaneously acquire amplitude and phase information, which significantly shortens the measurement time and improves the measurement efficiency.

[0024] 2) Simple system and low cost: By introducing a fixed auxiliary reference antenna as a phase reference, the complex dual-probe cooperative system or additional reference signal generation hardware is avoided, thus reducing system complexity and cost.

[0025] 3) High accuracy and good convergence: Based on frequency domain analysis and relative phase reconstruction technology, it can accurately recover the complex electric field distribution on the plane. After near-field to far-field transformation, it has good consistency with the real radiation pattern in the reliable angular domain. Moreover, the algorithm has fast convergence speed and good stability.

[0026] 4) Strong anti-drift capability: Since the measuring probe and the reference antenna receive the same signal transmitted by the antenna under test, the influence of signal source frequency drift or jitter on phase measurement can be effectively offset.

[0027] 5) The method is robust: Unlike existing technologies that rely on iterative or interferometric equation solving, the phase reconstruction process of this invention is deterministic and non-iterative, which ensures the uniqueness and global optimality of the results and avoids the risk of iteration not converging or getting trapped in local optima.

[0028] 6) High quality of reference signal: By setting the auxiliary reference antenna at 18~22 wavelengths and avoiding the pattern null, the reference signal is ensured to have both high signal-to-noise ratio and phase stability, laying a solid foundation for accurate phase recovery. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the measurement system according to an embodiment of the present invention.

[0030] Figure 2 This is a flowchart of phase and power calculation according to an embodiment of the present invention.

[0031] Figure 3 This is a simulation test setup diagram of an embodiment of the present invention.

[0032] Figure 4This is a comparison diagram (E-plane) of the far-field radiation pattern reconstructed by the method of this invention and the simulation reference radiation pattern.

[0033] Figure 5 This is a comparison diagram (H-plane) between the far-field radiation pattern reconstructed by the method of this invention and the simulation reference radiation pattern. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] This invention provides a preferred embodiment of a phaseless antenna measurement method. For example... Figure 1 As shown, the measurement system in this embodiment mainly includes: an antenna under test (AUT) 1, a measurement probe 2 that can move precisely on a two-dimensional plane, an auxiliary reference antenna 3 with a fixed position, and a software-defined radio 4 with dual-channel synchronous reception capability.

[0036] In this embodiment, the antenna under test 1 is placed at the origin of the coordinate system, with its main beam pointing in the positive Z-axis direction. The measuring probe 2 is mounted on a computer-controlled two-dimensional translation stage, with its scanning plane being the XOY plane. The size of the scanning area and the sampling interval of the probe in the X and Y directions (set to half a wavelength, i.e., 3 cm in this embodiment) are all set by the computer program. The auxiliary reference antenna 3 is fixedly installed at positions (0 cm, 120 cm, 21 cm). This position was determined through electromagnetic simulation optimization, located within the effective area of ​​the radiation field of the antenna under test, and completely outside the scanning plane (XOY plane) of the measuring probe 2. The two receiving channels of the software-defined radio 4 are connected to the measuring probe 1 and the auxiliary reference antenna 3 respectively through RF cables of equal length to ensure the consistency of hardware delay and are configured for synchronous acquisition mode.

[0037] The phaseless antenna measurement method described in this embodiment has the following core data processing flow: Figure 2 As shown, the specific steps include: S1: Synchronous signal acquisition and recording.

[0038] The measurement probe 2 is controlled to move point by point along a preset grid on the XOY scanning plane. At each sampling point, the antenna under test 1 continuously transmits a 5 GHz continuous wave (CW) signal. The software-defined radio 4 synchronously triggers its dual channels, simultaneously acquiring and recording the first signal received by the measurement probe 2. and the second signal received by auxiliary reference antenna 3 .in, The coordinates of the probe on the scanning plane are given.

[0039] S2: Calculation of complex electric field at a single point.

[0040] For the two time-domain signals acquired at each sampling point, the complex electric field value at that point is obtained through the following non-iterative direct calculation: 1) Perform Fast Fourier Transform (FFT) on both signals to obtain their spectra. and .

[0041] 2) Extract the peak value of the spectrum at the target frequency (5 GHz in this example). The amplitude of the electric field at this point is... It is determined directly by the spectral amplitude of the probe signal, i.e. .

[0042] 3) The phase of the electric field at that point relative to the reference signal The ratio of the complex peak values ​​of the two signals at 5 GHz is obtained by calculating the ratio of their spectral peak values. The calculation formula is as follows: Thus, the complex electric field at the sampling point can be obtained. .

[0043] S3: Full-field distribution reconstruction and near-field-far-field transformation.

[0044] By iterating through all sampling points and repeating step S2, the complex electric field distribution across the entire scanning plane can be reconstructed. Subsequently, the known complex near-field distribution was transformed from near-field to far-field using the standard plane wave spectrum expansion method to calculate the far-field radiation pattern of the antenna under test. .

[0045] To verify the effectiveness of this method, simulation verification was performed. The simulation settings are as follows: Figure 3 As shown, an electromagnetic simulation software FEKO was established with... Figure 1 The physical system corresponds to a model where the antenna under test is a standard horn antenna. Following the procedure described in this invention, signals from the probe and reference antenna are virtually "acquired" in the simulation, and then executed... Figure 2 The algorithm is shown.

[0046] The far-field radiation pattern reconstructed from simulation measurement data using the method of this invention is compared with the accurate theoretical radiation pattern directly calculated by FEKO software. The results are as follows: Figure 4 and Figure 5As shown, the normalized radiation patterns of the E-plane (φ=0°) and H-plane (φ=90°) are compared. It can be seen that within an angle range of ±40°, the radiation pattern reconstructed by the method of this invention essentially coincides with the simulated reference radiation pattern. Calculations show that the root mean square error (RMSE) of both in the main radiation region is approximately 0.5 dB, which fully demonstrates that the method described in this invention can accurately recover the antenna's radiation field without directly measuring the absolute phase.

[0047] It should be noted that the position of the auxiliary reference antenna (20 wavelengths) in this embodiment is an example optimized through simulation. The optimization principle is to minimize its disturbance to the scanning area field while ensuring sufficient received signal strength. A feasible criterion is to compare the difference in the scanning plane field distribution before and after introducing the reference antenna in the simulation, and select the position where the relative error change does not exceed 5%.

[0048] In summary, this invention introduces a fixed auxiliary reference antenna as a stable phase reference, utilizes software-defined radio to achieve dual-channel synchronous coherent measurement, and recovers the relative phase through non-iterative direct spectral ratio calculation, ultimately realizing efficient and accurate phase-free antenna near-field measurement. This method is particularly suitable for evaluating the radiation performance of integrated antennas or devices where RF ports are not accessible.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of phaseless antenna measurement, the method comprising: The method comprises the following steps: constructing a measurement system, which comprises an antenna to be measured, a measurement probe movable in a scanning plane, a fixedly arranged auxiliary reference antenna, and a software-defined radio with dual-channel synchronous receiving capability; controlling the measurement probe to move and sample in the scanning plane, and synchronously collecting, by the software-defined radio, a first signal received by the measurement probe and a second signal received by the auxiliary reference antenna at each sampling point; reconstructing, by the software-defined radio or a computing device connected thereto, a complex electric field distribution on the scanning plane through a non-iterative operation process based on the first signal and the second signal at each sampling point; obtaining a far-field radiation pattern of the antenna to be measured through near-field to far-field transformation based on the complex electric field distribution.

2. The method of phaseless antenna measurement of claim 1, wherein, The implementation steps of reconstructing the complex electric field distribution on the scanning plane through the non-iterative operation process comprise: performing frequency domain transformation on the first signal and the second signal of each sampling point respectively to obtain a first frequency spectrum and a second frequency spectrum; determining the radiation field amplitude of the sampling point according to the amplitude of the first frequency spectrum; calculating the complex ratio of the first frequency spectrum and the second frequency spectrum at a specific frequency, and directly determining the relative phase of the sampling point relative to the auxiliary reference antenna according to the phase angle of the complex ratio; composing the complex electric field distribution by the amplitudes and relative phases of all sampling points.

3. The phaseless antenna measurement method of claim 2, wherein, The specific frequency is the peak frequency of the first frequency spectrum and / or the second frequency spectrum.

4. The method of phaseless antenna measurement of claim 2, wherein, The specific frequency is the central operating frequency of the antenna to be measured.

5. The method of phaseless antenna measurement of claim 1, wherein, The auxiliary reference antenna is arranged at a distance of 18-22 operating wavelengths from the antenna to be measured to ensure that an effective reference signal can be received and at the same time to avoid significant reflection interference between the auxiliary reference antenna and the measurement probe.

6. The method of phaseless antenna measurement of claim 5, wherein, The position of the auxiliary reference antenna needs to avoid the scanning plane of the measurement probe and the main lobe and side lobe nulls of the radiation pattern of the antenna to be measured.

7. The method of phaseless antenna measurement of claim 1, wherein, The sampling interval of the measurement probe on the scanning plane is not greater than half an operating wavelength.

8. A phaseless antenna measurement system for implementing the method of claim 1, characterized by The system comprises: an antenna to be measured; a measurement probe configured to move in a scanning plane; a fixed auxiliary reference antenna; a software-defined radio with at least dual-channel synchronous receiving capability for synchronously collecting the received signals of the measurement probe and the auxiliary reference antenna; a signal processing unit configured to perform the following operations: reconstructing a complex electric field distribution on the scanning plane through a non-iterative operation process based on the two synchronously collected signals; performing a near-field to far-field transformation algorithm to generate a far-field radiation pattern.

9. The phaseless antenna measurement system of claim 8, wherein, The specific steps of reconstructing the complex electric field distribution by the signal processing unit comprise: performing frequency domain transformation on the first signal and the second signal of each sampling point to obtain a first frequency spectrum and a second frequency spectrum; determining the radiation field amplitude of the sampling point according to the amplitude of the first frequency spectrum; calculating the complex ratio of the first frequency spectrum and the second frequency spectrum at a specific frequency, and directly determining the relative phase of the sampling point relative to the auxiliary reference antenna according to the phase angle of the complex ratio; The complex electric field distribution is composed of the amplitudes and the relative phases of all the sampling points.

10. A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the signal processing steps in the method of any one of claims 1 to 7.

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