Method for measuring and calculating electromagnetic field quiet zone parameters in anechoic chamber

Abstract

The present application relates to the technical field of anechoic chamber, and provides a method for measuring and calculating electromagnetic field quiet zone parameters of an anechoic chamber, comprising the following steps: S1, measuring electromagnetic field quiet zone receiving level by using an omnidirectional antenna to form a corresponding number series of space path-receiving level; S2, obtaining a sparse sampling waveform by using a first space resolution with equal intervals, performing fast Fourier transform to form an original sequence of a space spectrum calculation sequence, performing zero padding to form a sequence after zero padding, and performing inverse fast Fourier transform to obtain a sparse sampling recovery waveform; and S3, calculating electromagnetic field quiet zone parameters based on the sparse sampling recovery waveform obtained in step S2. The present application uses a sparse sampling recovery waveform, greatly reduces sampling points, can achieve high waveform fidelity, can detect the peak value corresponding to the original waveform, and obtains more detailed tapering and ripple curves, thereby improving test efficiency and saving test time.

Description

Technical Field

[0001] This invention relates to the field of anechoic chamber technology, and in particular to a method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber. Background Technology

[0002] An anechoic chamber is a device used to test and measure the performance of electromagnetic waves. It uses absorbing materials to eliminate electromagnetic wave reflections from walls, ceilings, and floors to simulate an open space environment. The quiet zone refers to the reflection level within the anechoic chamber, specifically the area used to measure antenna performance. Testing the quiet zone reflection level in an anechoic chamber typically follows industry standards in my country. Common testing methods use a standard antenna as the transmitter, moving it along a predetermined spatial path within the quiet zone and measuring the received signal strength. This creates a correlation between the spatial path and the received signal strength. Processing this correlation yields data such as taper, ripple, and quiet zone reflection level.

[0003] Based on the test results and performance metrics, evaluate whether the reflection level in the quiet zone of the anechoic chamber meets the expected performance requirements. If it does not meet the requirements, optimization of the anechoic chamber design or absorbing materials may be necessary.

[0004] In current testing standards, there are two traditional approaches when measuring the spatial path-received signal strength correlation:

[0005] 1. The spatial resolution of the spatial path is generally chosen to be 1 / 8 to 1 / 10 of the wavelength corresponding to the test frequency. This is because when calculating ripple data, it is necessary to extract the maximum and minimum values ​​of this sinusoidal waveform sequence. If the spatial resolution is not fine enough, there will be a significant deviation in extracting the maximum and minimum values. However, when testing in the millimeter-wave band, the wavelength is very small. For example, 1 / 10 of the wavelength corresponding to 30 GHz is 1 mm. Therefore, measuring a quiet zone of a certain length, such as 3 m, would require measuring 3000 points, which would consume a lot of time.

[0006] 2. A directional antenna with a certain gain is selected for reception. However, research shows that this method introduces certain errors and test inconsistencies.

[0007] 3. Currently, there is a lack of methods for simulating and predicting the quiet zone parameters under different absorption angles of absorbing materials.

[0008] Currently, there is an urgent need for a technical solution that can simultaneously address the above three technical problems. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber.

[0010] The present invention adopts the following technical solution:

[0011] On one hand, the present invention provides a method for measuring and calculating the quiet zone parameters of the electromagnetic field in an anechoic chamber, characterized in that the method includes:

[0012] S1. Measure the received level in the electromagnetic field quiet zone: Use an omnidirectional antenna to move along a set spatial path in the electromagnetic field quiet zone, measure the strength of the received electromagnetic signal, and form a corresponding sequence of spatial path-received level.

[0013] S2. Using an equally spaced first spatial resolution, the received level in the quiet zone is measured by a point-by-point spatial scanning method to obtain a spatial path-received level sequence as a sparse sampled waveform; the sparse sampled waveform is subjected to a fast Fourier transform to form the original sequence of the spatial spectrum calculation sequence; the original sequence is padded with zeros to form a zero-padded sequence; the zero-padded sequence is subjected to an inverse fast Fourier transform to obtain the sparse sampled recovered waveform.

[0014] S3. Calculate the electromagnetic field quiet zone parameters based on the sparse sampling recovered waveform obtained in step S2.

[0015] In addition to any of the possible implementations described above, another implementation is provided in which, in step S1, the omnidirectional antenna is measured using two configurations: one in which the main polarization direction of the omnidirectional antenna is placed horizontally, and the other in which the main polarization direction of the omnidirectional antenna is placed vertically.

[0016] In addition to any of the possible implementations described above, another implementation is provided in which, in step S2, the zero-padded sequence undergoes further spatial spectral separation algorithm processing:

[0017] Based on the absolute value of the zero-padded sequence data, apart from the sequence elements close to zero, there will be 4 groups of data in the sequence that are significantly larger than the surrounding absolute values, denoted as A, B, C, and D from left to right; these will be processed using the following two different algorithms.

[0018] Algorithm 1: In the zero-padded sequence data, only the corresponding sequences of A and D are retained, and the values ​​at other positions are reset to zero, forming a new spatial spectrum sequence S. T , for S T Performing an inverse fast Fourier transform (IFFT) yields the space-level data sequence M corresponding to the quiet zone taper. T ;

[0019] Algorithm 2: In the zero-padding sequence data, only the corresponding sequences of parts B and C are retained, and the values ​​at other positions are reset to zero, forming a new spatial spectrum sequence S. R , for S RPerforming an inverse fast Fourier transform (IFFT) yields the space-level data sequence M corresponding to the quiet zone ripple. R .

[0020] In addition to any of the possible implementations described above, another implementation is provided in which the electromagnetic field still zone parameters in step S3 include taper, ripple, and still zone reflection level.

[0021] In addition to any of the possible implementations described above, another implementation is provided in which, in step S2, the first spatial resolution uses 1 / 2 times the electromagnetic wave wavelength λ, or 1 / 3 times the interference wavelength λ. L .

[0022] In addition to any of the possible implementations described above, another implementation is provided, wherein the interference wavelength λ L The calculation method is as follows:

[0023]

[0024] In the formula: λ is the wavelength of the electromagnetic wave, and α is the angle between the direction of the electromagnetic wave and the direction of the mirror electromagnetic wave.

[0025] In addition to any of the possible implementations described above, a further implementation is provided, wherein the electromagnetic wave power reflectivity R[dB] of the absorbing material at different angles is calculated as follows:

[0026] R[dB]=R min +ΔR[dB];

[0027] ΔR[dB]=0.001α 2 +0.0737α;

[0028] The electromagnetic wave power reflectivity is lowest when incident perpendicularly, let's assume it's R. min The dimension is dB.

[0029] In addition to any of the possible implementations described above, another implementation is provided in which, in step S2, when performing zero-padding on the original sequence, a certain number of zero values ​​are inserted starting from the middle sequence, and the number of zero values ​​inserted is 3 to 10 times the length of the original sequence.

[0030] In addition to any of the possible implementations described above, a further implementation is provided in which, in step S2, the spatial resolution of the data sequence of the sparsely sampled recovered waveform is ΔS0.

[0031]

[0032] Where L is the spatial scale corresponding to the data sequence, and N0 is the number of sequence elements after zero-padding the spatial spectrum.

[0033] On the other hand, the present invention also provides a processor-readable storage medium including instructions that, when executed on a processor, cause the processor to perform the above-described method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber.

[0034] The beneficial effects of this invention are as follows: This invention proposes a formula for calculating the electromagnetic wave power reflectivity R[dB] of absorbing materials at different angles. This allows for analytical prediction of the reflectivity of absorbing materials at different angles, thus establishing a foundation for subsequent calculations. This invention proposes a complete set of equations for simulating the quiet zone parameters of a cuboid anechoic chamber, enabling the prediction of these parameters in advance, thus avoiding design errors and facilitating design optimization. This invention proposes a measurement method using an omnidirectional antenna. Theoretical analysis and simulation calculations both demonstrate that this method can improve the consistency of measurement results. The measurement method proposed in this invention employs "sparse sampling to recover waveforms," ​​significantly reducing the number of sampling points while achieving high waveform fidelity. It can detect the peak value corresponding to the "original waveform," and the obtained tapered and ripple curves have richer details, thus greatly improving testing efficiency. While obtaining accurate results, it saves testing time and instrument operation time, especially at higher frequencies such as above 6GHz, where the shorter wavelength of electromagnetic waves makes the time-saving benefits even more pronounced. Attached Figure Description

[0035] Figure 1 The diagram shown is a schematic representation of the multipath propagation generated by the interface reflection of the anechoic chamber in the embodiment.

[0036] Figure 2 The image shown is a mirrored schematic diagram of the radiation pattern corresponding to the GFEH surface reflection in the embodiment.

[0037] Figure 3 The diagram shown is a mirror image of the radiation pattern corresponding to the compression field in the embodiment.

[0038] Figure 4 The diagram shown is a schematic diagram of the interference wavelength calculation in the embodiment.

[0039] Figure 5 The figure shows the relationship curve between ΔR[dB] and the incident angle in the embodiment.

[0040] Figure 6 The diagram shows the spatial spectrum sequence processing in the embodiment; (a) is the original sequence; (b) is the sequence after zero padding.

[0041] Figure 7 The diagram shown illustrates the weighting effect of the receiving antenna pattern during the measurement process in this embodiment.

[0042] Figure 8 The diagram shows the arrangement of the omnidirectional receiving antenna in the embodiment.

[0043] Figure 9 The image shown is a normalized spatial field strength map obtained by measuring an ideal omnidirectional receiving antenna in the embodiment.

[0044] Figure 10 The image shows the normalized spatial field strength obtained from measurements taken with a directional receiving antenna.

[0045] Figure 11 The figure shows the taper and ripple curves calculated by the 18GHz "spatial spectrum separation method" in the embodiment.

[0046] Figure 12 The figure shows the taper and ripple curves calculated using the 18GHz polynomial fitting method.

[0047] Figure 13 The image shows the "original waveform", "sparsely sampled waveform", and "sparsely sampled recovered waveform" in the quiet zone of a 5.8 GHz anechoic chamber.

[0048] Figure 14 The image shown is a magnified view of the "original waveform", "sparsely sampled waveform", and "sparsely sampled recovered waveform" in the quiet zone of a 5.8 GHz anechoic chamber.

[0049] Figure 15 The figure shows the taper and ripple curves calculated by the 5.8 GHz "spatial spectrum separation method" in the embodiment.

[0050] Figure 16 The figure shows the taper and ripple curves calculated using the 5.8GHz polynomial fitting method.

[0051] Figure 17 The images shown are the "original waveform", "sparsely sampled waveform", and "sparsely sampled recovered waveform" in the quiet zone of the 32GHz anechoic chamber in the embodiment.

[0052] Figure 18 The image shown is a magnified view of the "original waveform", "sparsely sampled waveform", and "sparsely sampled recovered waveform" in the quiet zone of a 32GHz anechoic chamber.

[0053] Figure 19 The figure shows the taper and ripple curves calculated by the 32GHz "spatial spectrum separation method" in the embodiment.

[0054] Figure 20 The figure shows the taper and ripple curves calculated using the 32GHz polynomial fitting method.

[0055] Figure 21 The figure shown is a graph illustrating the variation of the quiet zone reception amplitude of a certain compressed anechoic chamber at 8 GHz, as measured in the embodiment.

[0056] Figure 22The figure shown is a graph illustrating the variation of the quiet zone reception amplitude of a certain compressed anechoic chamber at 38.5 GHz, as measured in the embodiment.

[0057] Figure 23 The diagram shown is a flowchart illustrating a method for measuring and calculating the electromagnetic field quiet zone parameters in an anechoic chamber according to an embodiment of the present invention. Detailed Implementation

[0058] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered in isolation, but can be combined with each other to achieve better technical effects.

[0059] This invention provides a method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber, as illustrated in the flowchart below. Figure 23 As shown.

[0060] 1. Analyze the interference wavelength using multiple mirror images. For example... Figure 1 As shown, in a rectangular anechoic chamber, if the transmitting antenna is located at point O, a cross-section of the quiet zone space, as shown by cross-section R, is required. Then, on the five faces other than ABCD, a mirror image of the transmitting antenna pattern is formed. The mirroring rule is: symmetrical mirroring is performed according to the geometry of the antenna pattern, as shown... Figure 1 As shown. It is particularly important to note that the main lobe direction of the antenna pattern corresponding to the GFEH plane is opposite to the main lobe direction of the main antenna pattern, as shown below. Figure 2 As shown.

[0061] 2. In the analysis of a compact field with a reflective surface, the image formed by the reflection of the feed source by the reflective surface is regarded as the radiation body, such as... Figure 3 As shown in the diagram, the geometric position of OT can be calculated using the method for calculating the image of a concave mirror. Then, the radiation pattern image formed by reflections from the walls of the anechoic chamber, such as O1T1, is calculated.

[0062] 3. Calculate the interference wavelength. For example... Figure 4 As shown, considering the interference formed by the electromagnetic waves emitted by the antenna body and the electromagnetic waves of a certain mirror antenna, since the quiet zone is mainly on the central axis of the anechoic chamber, the angle between the direction of the electromagnetic wave emitted by the antenna body and the direction of the electromagnetic wave emitted by the mirror antenna is α. Then, the path difference of the electromagnetic wave emitted by the mirror antenna towards the quiet zone is Δd, and the line segment in the direction of the interference formed in the quiet zone is ΔL. Then, the following relationship exists:

[0063]

[0064] Let the wavelength of the electromagnetic wave be λ, then the interference wavelength in the direction ΔL can be calculated as λ. L :

[0065]

[0066] In typical anechoic chamber configurations, sinα is less than 1 or even less than 1 / 2, so the interference wavelength is generally greater than the electromagnetic wave wavelength.

[0067] 4. Calculate the electromagnetic wave power reflectivity at different angles. On the walls of an anechoic chamber lined with absorbing material, the reflectivity is generally lowest when the wave is incident perpendicularly; let's assume it's R. min The dimension is dB. Therefore, the reflectivity at other incident angles can be expressed as R[dB]:

[0068] R[dB]=R min +ΔR[dB] (3)

[0069] Assuming the incident angle is expressed as β, then ΔR[dB] can be expressed as equation (4), such as Figure 5 As shown:

[0070] ΔR[dB]=0.001α 2 +0.0737α (4)

[0071] 5. When measuring the received level in the quiet zone using a point-by-point spatial scanning method and then calculating the quiet zone parameters, a coarser, equally spaced first spatial resolution can be used, such as 1 / 2 times the electromagnetic wave wavelength λ, or 1 / 3 times the interference wavelength λ. L Then, the spatial-received level data sequence is obtained, called the "sparse sampled waveform." This data sequence is then subjected to a Fast Fourier Transform (FFT) to form the original sequence for spatial spectrum calculation, such as... Figure 6 As shown in (a). Then, zero-padding is performed on the original sequence, that is, starting from the middle of the sequence, a certain number of zero values ​​are inserted. The number of insertions should ideally be 3 to 10 times the length of the original sequence, forming a "zero-padding sequence", as shown in (a). Figure 6 As shown in (b). Then, performing an inverse fast Fourier transform (IFFT) on this "zero-padded sequence" yields a more refined space-received level data sequence M. F , which can be called “sparse sampling recovery waveform”, the spatial resolution of the new data sequence can be expressed as △S0, as shown in equation (5), where L is the spatial scale corresponding to the spatial sequence and N0 is the number of sequence elements of the “zero-padding sequence” of the spatial spectrum;

[0072]

[0073] It can be based on data sequence M F Parameters such as quiet zone taper, ripple, and quiet zone reflection level are calculated.

[0074] 6. Regarding the "zero-padded sequence" of the spatial spectrum described in point 5, further separation algorithms can be performed, such as... Figure 6 As shown in (b), based on the absolute value of the data, apart from sequence elements close to zero, there are generally four groups of data in the sequence that are significantly larger than the surrounding absolute values, denoted as A, B, C, and D from left to right. Two different algorithms are used for processing: (1) In the original sequence, only the sequences corresponding to A and D are retained, and the values ​​at other positions are reset to zero, forming a new spatial spectrum sequence S. T , for S T By performing an inverse fast Fourier transform (IFFT), the space-level data sequence M corresponding to the quiet zone taper can be obtained. T (2) In the original sequence, only the sequences corresponding to B and C are retained, and the values ​​in other positions are reset to zero to form a new spatial spectrum sequence S. R For S R By performing an inverse fast Fourier transform (IFFT), the space-level data sequence M corresponding to the quiet zone ripple can be obtained. R M T and M R The corresponding spatial resolution is determined by equation (5). We can call this method the "spatial spectrum separation method".

[0075] 7. When measuring the received level in the quiet zone, in order to improve the signal-to-noise ratio, a directional antenna with a certain gain, such as a horn antenna, is generally used. In this case, during the process of converting electromagnetic waves into antenna port voltage, electromagnetic waves incident through different paths will be weighted by the antenna pattern. Generally, the gain corresponding to the main path of the direct incident is high, while the gain corresponding to the multipath of the reflected incident is low, which leads to two problems: (1) The ratio of the measured multipath level to the main path level is smaller than the ratio of the field strength of the electromagnetic wave, resulting in an underestimation of the evaluation result. (2) The measurement results are inconsistent when using antennas with different patterns. In order to solve this problem, an omnidirectional antenna is used for measurement. Considering that the omnidirectional antennas that can be realized in engineering are all omnidirectional antennas on a certain cross section, two configurations are used for measurement: (1) The main polarization direction of the omnidirectional antenna is placed horizontally, such as Figure 8 A in H (2) The main polarization direction of the omnidirectional antenna is placed vertically, such as... Figure 8 A in V .

[0076] An embodiment of the present invention provides a processor-readable storage medium, including instructions that, when executed on a processor, cause the processor to perform the aforementioned method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber.

[0077] Example 1

[0078] exist Figure 1Within the geometric configuration shown, the transmitting antenna in the simulation is set with a gain of 19dB, a horizontal 3dB beamwidth of 27.5°, and a vertical 3dB beamwidth of 13.7°, positioned at (0,0,0) in the above coordinate system. The anechoic chamber has dimensions of 20m in the y-direction and 20m in the z-direction, and the transmitting antenna is 40m away from the GFEH surface on the x-axis. The reflectivity of the absorbing materials on each surface is set to -30dB under perpendicular incident conditions. In the simulation model, the simulation frequency is 18GHz, and the curve of the normalized spatial field strength as a function of spatial coordinates obtained using an ideal omnidirectional antenna is shown below. Figure 9 As shown in the figure. Using a directional antenna for measurement, with a gain of 12dB, a horizontal 3dB beamwidth of 61.5°, and a vertical 3dB beamwidth of 30.7°, the measured normalized received level as a function of spatial coordinates is shown in the figure. Figure 10 As shown. Comparison Figure 9 and Figure 10 It can be seen that, Figure 9 The corresponding electric field strength variation range is 0.27 dB. Figure 10 The corresponding field strength variation range is 0.18 dB, which indicates that the data measured using an omnidirectional antenna is more reasonable.

[0079] Then, according to the "spatial spectrum separation method" of this invention, the taper and ripple curves are calculated, such as... Figure 11 As shown. For comparison, the tapering and ripple curves calculated using the traditional polynomial fitting method are also presented, such as... Figure 12 As shown. Comparison Figure 11 and Figure 12 It can be seen that the results are largely consistent, but Figure 11 The details of the tapered curve shown are more in line with the actual situation.

[0080] Example 2

[0081] Conducting quiet zone simulations of a 5.8GHz anechoic chamber, such as... Figure 13 and Figure 14 As shown, the waveform using an electromagnetic wave wavelength λ of 1 / 10 is called the "original waveform", the waveform using an electromagnetic wave wavelength λ of 1 / 2 is called the "sparsely sampled waveform", and the "sparsely sampled recovered waveform" as described in claim 5.

[0082] from Figure 14 As shown in the magnified view, the "sparse sampling waveform" itself has a defect in detecting the peak value of the "original waveform". At the same time, the "sparse sampling recovered waveform" achieves a very high waveform fidelity and can detect the peak value corresponding to the "original waveform".

[0083] Then, the "spatial spectrum separation method" of this invention calculates the taper and ripple curves corresponding to 5.8 GHz, as shown below. Figure 15 As shown. For comparison, the tapering and ripple curves calculated using the traditional polynomial fitting method are also presented, such as... Figure 16 As shown. Comparison Figure 15 and Figure 16 It can be seen that the results are largely consistent, but Figure 15 The tapered curve shown is more detailed.

[0084] Example 3

[0085] Conducting quiet zone simulations in a 32GHz anechoic chamber, such as... Figure 17 and Figure 18 As shown, a waveform using an electromagnetic wave wavelength λ of 1 / 10 is called the "original waveform," a waveform using an electromagnetic wave wavelength λ of 1 / 2 is called the "sparsely sampled waveform," and the "sparsely sampled recovered waveform" as described in claim 5. Figure 17 In the millimeter wave band, due to the dense waveforms and the difficulty in distinguishing superimposed waveforms, local magnification can be used to form... Figure 18 .

[0086] Then, according to the "spatial spectrum separation method" of this invention, the taper and ripple curves corresponding to 32 GHz are calculated, as follows: Figure 19 As shown. For comparison, the tapering and ripple curves calculated using the traditional polynomial fitting method are also presented, such as... Figure 20 As shown. Comparison Figure 19 and Figure 20 It can be seen that the results are largely consistent, but Figure 19 The tapered curve shown is more detailed.

[0087] Example 4

[0088] Actual measurements were conducted in a compact anechoic chamber to measure amplitude changes in the quiet zone. Measurements were first performed at 8 GHz, and the results are as follows: Figure 21 As shown, approximately three interference peaks appear on a scale of 100 cm, therefore the interference wavelength λ in the ΔL direction can be calculated. L The wavelength is approximately 33cm, which is greater than the wavelength of electromagnetic waves of 8GHz, λ = 3.75cm, consistent with the calculation principle of interference wavelength in this invention.

[0089] Then measurements were performed at 38.5 GHz, and the results are as follows: Figure 22 As shown, approximately six interference peaks appear on a scale of 50 cm to the left, thus the interference wavelength λ in the ΔL direction can be calculated. L It is approximately 50cm / 6 = 8.33cm, which is greater than the wavelength λ = 0.78cm of electromagnetic waves greater than 38.5GHz, which is consistent with the law of calculating interference wavelength in this invention.

[0090] While several embodiments of the present invention have been provided herein, those skilled in the art should understand that modifications can be made to these embodiments without departing from the spirit of the invention. The above embodiments are merely exemplary and should not be construed as limiting the scope of the invention.

Claims

1. A method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber, characterized in that, The method includes: S1. Measure the received level in the electromagnetic field quiet zone: Use an omnidirectional antenna to move along a set spatial path in the electromagnetic field quiet zone, measure the strength of the received electromagnetic signal, and form a corresponding sequence of spatial path-received level. S2. Using an equally spaced first spatial resolution, the received level in the quiet zone is measured by a point-by-point spatial scanning method to obtain a spatial path-received level sequence as a sparse sampled waveform; the sparse sampled waveform is subjected to a fast Fourier transform to form the original sequence of the spatial spectrum calculation sequence; the original sequence is padded with zeros to form a zero-padded sequence; the zero-padded sequence is subjected to an inverse fast Fourier transform to obtain the sparse sampled recovered waveform. S3. Calculate the electromagnetic field quiet zone parameters based on the sparse sampling recovered waveform obtained in step S2; In step S2, the zero-padded sequence undergoes further spatial spectral separation algorithm processing, specifically as follows: Based on the absolute value of the zero-padded sequence data, apart from the sequence elements close to zero, there will be 4 groups of data in the sequence that are significantly larger than the surrounding absolute values, denoted as A, B, C, and D from left to right; these will be processed using the following two different algorithms. Algorithm one: in the zero-padded sequence data, only the A, D part corresponding to the number sequence is retained, and the values at other positions are reset to zero to form a new spatial spectrum sequence S T , and the S T is subjected to inverse fast Fourier transform IFFT to obtain a spatial-level data sequence M corresponding to the static zone tapering T ; Algorithm two, only keep the corresponding number sequence of B, C part in the zero-padded sequence data, and set the value of other positions to zero, forming a new spatial spectrum sequence S R , do inverse fast Fourier transform IFFT on S R , to get the spatial-level data sequence M corresponding to the static zone ripple R .

2. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 1, characterized in that, In step S1, the omnidirectional antenna is measured using two configurations: one in which the main polarization direction of the omnidirectional antenna is placed horizontally, and the other in which the main polarization direction of the omnidirectional antenna is placed vertically.

3. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 1, characterized in that, In step S3, the electromagnetic field still zone parameters include taper, ripple, and still zone reflection level.

4. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 1, characterized in that, In step S2, the first spatial resolution uses 1 / 2 times the electromagnetic wave wavelength λ, or 1 / 3 times the interference wavelength λ. L .

5. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 3, characterized in that, Interference wavelength λ L The calculation method is as follows: In the formula: λ is the wavelength of the electromagnetic wave, and α is the angle between the direction of the electromagnetic wave and the direction of the mirror electromagnetic wave.

6. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 3, characterized in that, The calculation method for electromagnetic wave power reflectivity R [dB] at different angles is as follows: ； ； The electromagnetic wave power reflectivity is lowest when incident perpendicularly, which is R. min The dimension is dB.

7. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 1, characterized in that, In step S2, when performing zero-padding on the original sequence, a certain number of zero values ​​are inserted starting from the middle of the sequence. The number of zero values ​​inserted is 3 to 10 times the length of the original sequence.

8. The method for measuring and calculating the electromagnetic field quiet zone parameters of an anechoic chamber as described in claim 1, characterized in that, In step S2, the spatial resolution of the data sequence of the sparsely sampled recovered waveform is ΔS0. Where L is the spatial scale corresponding to the data sequence, and N0 is the number of sequence elements after zero-padding the spatial spectrum.

9. A processor-readable storage medium comprising instructions that, when executed on a processor, cause the processor to perform the method for measuring and calculating the quiet zone parameters of an electromagnetic field in an anechoic chamber as described in any one of claims 1-8.

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