CN111413552A - Antenna near field rapid measurement method - Google Patents
Antenna near field rapid measurement method Download PDFInfo
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- CN111413552A CN111413552A CN202010195575.9A CN202010195575A CN111413552A CN 111413552 A CN111413552 A CN 111413552A CN 202010195575 A CN202010195575 A CN 202010195575A CN 111413552 A CN111413552 A CN 111413552A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/10—Radiation diagrams of antennas
Abstract
The invention provides an antenna near field rapid measurement system, which comprises an FPGA, a programmable metamaterial surface and a probe; the programmable metamaterial surface is arranged between the probe and the antenna to be tested; the programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array; each reconfigurable metamaterial unit is loaded with a diode; the FPGA encodes the surface of the programmable metamaterial by controlling the on-off of the diodes in each reconfigurable metamaterial unit; and the probe acquires near-field data of the antenna to be tested, which is transmitted through the surface of the programmable metamaterial, and reconstructs a signal of the antenna to be tested according to the near-field data. The invention greatly improves the measurement efficiency, shortens the measurement time and can obtain good radiation reconstruction effect.
Description
Technical Field
The invention relates to the technical field of antenna near field measurement, in particular to an antenna near field measurement system and method.
Background
The development of antenna technology brings great challenges to the high-precision and high-efficiency measurement of antennas, the measurement of antennas with large size and large phased array is limited by places, the measurement efficiency is low, and the antenna measurement needs a large amount of data due to the reason, so that a long time is needed for collecting the data. It is currently expected that compact field and near field measurement techniques will be studied and developed by acquiring far field patterns of antennas in a limited distance space. This technique reduces the measurement site requirements, but provides a small significant improvement in measurement efficiency. In this context, effective methods must be proposed to characterize the radiation characteristics of the antenna.
Compressed Sensing (CS) is a new Sensing method, and is a technology that compresses and samples a signal at a frequency far lower than Nyquist sampling theorem, and recovers the original signal with high probability, and the aspects of signal acquisition and processing are significantly changed. The idea of using the sparsity of the signal to realize the low sampling rate has important application in the aspects of signal processing, information theory, electrical engineering and the like. Despite the great potential, CS is more recently used in electromagnetism, and the research on antenna measurement is much more known, and most of the proposed methods rely on a priori knowledge of the antenna under test.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides an antenna near field measurement system and method.
The invention provides an antenna near field rapid measurement system, which comprises an FPGA, a programmable metamaterial surface and a probe; the probe is arranged on one surface of the programmable metamaterial, and the other surface of the programmable metamaterial is used for placing an antenna to be tested;
the programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array; each reconfigurable metamaterial unit is loaded with a diode; the FPGA encodes the surface of the programmable metamaterial by controlling the on-off of the diodes in each reconfigurable metamaterial unit;
the probe acquires near-field data of the antenna to be tested, which penetrates through the surface of the programmable metamaterial, and reconstructs the radiation characteristic of the antenna to be tested according to the near-field data.
Preferably, on the surface of the programmable metamaterial, the distance between adjacent reconfigurable metamaterial units is half wavelength of the working frequency; the working frequency is the frequency with the largest phase difference of the reconfigurable metamaterial unit under two states of diode conduction and diode cut-off.
Preferably, the dielectric substrate in the reconfigurable metamaterial unit adopts TaconicT L X-8.
Preferably, the dielectric substrate has a dielectric constant of 2.55, a loss tangent of 0.0019, and a thickness h of 0.762 mm.
Preferably, the number of reconfigurable metamaterial units on the surface of the programmable metamaterial is 25 × 25.
A method for quickly measuring the near field of an antenna comprises the following steps:
firstly, a programmable metamaterial surface is arranged between a probe and an antenna to be detected, and the programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array;
adding a diode on each reconfigurable metamaterial unit to obtain a frequency with the maximum phase difference of each reconfigurable metamaterial unit under two states of diode conduction and diode cutoff as a working frequency;
controlling the conduction or cut-off state of the diodes of the reconfigurable metamaterial units through the FPGA, and encoding the surface of the programmable metamaterial;
and respectively measuring the near field distribution of each reconfigurable metamaterial unit in the states of diode conduction and diode cut-off, and calculating the electric field received by the probe according to the Huygens principle.
Preferably, when calculating the electric field, the programmable metamaterial surface is regarded as a measurement matrix in the CS, and the signals acquired by the probe are represented as:
wherein the content of the first and second substances,ymrecord value, x, for the m-th antenna measured by the probenRepresenting the original signal of the antenna to be tested,
is the encoding state of the programmable metamaterial;
and then recovering the original signal through a CS recovery algorithm.
Preferably, the distance between adjacent reconfigurable metamaterial units on the surface of the programmable metamaterial is half wavelength of the working frequency.
The invention provides an antenna near-field measurement system and method, wherein a programmable metamaterial surface is arranged between an antenna to be measured and a probe, and the transmission characteristic of electromagnetic waves is controlled by changing the conduction and cut-off states of unit diodes on the metamaterial surface; the space between adjacent codeable metamaterial units is about half wavelength, the electromagnetic coupling between the units can be ignored, the near-field distribution of the units in the same state is the same, and the radiation information of the antenna can be recovered and reconstructed by using a CS (Circuit switching) technology only by changing the state distribution of the metamaterial codes; the method greatly improves the measurement efficiency, shortens the measurement time and can obtain good radiation reconstruction effect.
The invention considers that most of the information collected in the antenna near-field plane scanning is redundant, a programmable metamaterial surface is arranged on the antenna near-field plane, which is equivalent to a measurement matrix in the CS, and the original data can be recovered by only a small amount of data.
Drawings
Fig. 1 is a structural diagram of a near-field rapid antenna measurement system according to the present invention;
fig. 2 is a flowchart of a method for rapidly measuring a near field of an antenna according to the present invention;
FIG. 3(a) is a schematic diagram of a reconfigurable metamaterial unit;
FIG. 3(b) is an equivalent circuit diagram of the reconfigurable metamaterial unit under two states of diode conduction (ON) and cut-OFF (OFF);
FIG. 3(c) is a diagram showing the transmission phase of a linearly polarized wave at normal incidence;
FIG. 3(d) is a graph of the transmission amplitude of a linearly polarized wave at normal incidence;
FIG. 4(a) is an original image of the near field amplitude of the antenna;
FIG. 4(b) is an amplitude recovery image of the present invention with 40% of near-field sparse sampling;
FIG. 5(a) is a conventional sampling phase raw graph;
FIG. 5(b) phase recovery image of the present invention for near-field sparse sampling of 40%;
Detailed Description
Referring to fig. 1, the antenna near field rapid measurement system provided by the invention comprises an FPGA, a programmable metamaterial surface and a probe. The probe is arranged on one surface of the programmable metamaterial, and the other surface of the programmable metamaterial is used for placing an antenna to be tested.
The programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array.
A reconfigurable metamaterial unit includes a substrate, a metal via, and a diode. Therefore, each reconfigurable metamaterial unit is loaded with a diode, and the state of the reconfigurable metamaterial unit is controlled through the on-off of the diode, namely the state of the reconfigurable metamaterial unit is controlled through controlling the bias voltage of the diode.
The FPGA controls the on-off of the diodes in the reconfigurable metamaterial units, so that the reconfigurable units have different resonant frequencies, and the programmable metamaterial surface is coded.
Specifically, electromagnetic waves of an antenna to be tested are incident on the surface of the programmable metamaterial, the FPGA is used for controlling the on-state or off-state of each metamaterial unit, specifically, the state can be represented by '1' and '0', the '1' represents on, and the '0' represents off, so that the coding sequence of the surface of the encodable metamaterial is obtained.
The probe acquires near-field data of the antenna to be tested, which penetrates through the surface of the programmable metamaterial, and reconstructs the radiation characteristic of the antenna to be tested according to the near-field data. Specifically, a series of solving equations can be established by using a CS technology, so that the signal reconstruction of the antenna to be detected is carried out through a CS perception recovery algorithm.
In this embodiment, on the surface of the programmable metamaterial, the distance between adjacent reconfigurable metamaterial units is half a wavelength of the operating frequency; the working frequency is the frequency with the largest phase difference of the reconfigurable metamaterial unit under two states of diode conduction and diode cut-off.
Specifically, in the present embodiment, TaconicT L X-8 is used as the dielectric substrate in the reconfigurable metamaterial unit, the dielectric constant of the dielectric substrate is 2.55, the loss tangent is 0.0019, and the thickness h is 0.762 mm.
The invention also provides a method for quickly measuring the near field of the antenna, which comprises the following steps:
firstly, a programmable metamaterial surface is placed between a probe and an antenna to be tested, and the programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array.
And secondly, adding a diode on each reconfigurable metamaterial unit, and obtaining the frequency with the largest phase difference of each reconfigurable metamaterial unit under two states of diode conduction and diode cut-off as the working frequency. In this embodiment, the distance between adjacent reconfigurable metamaterial units on the surface of the programmable metamaterial is half a wavelength of the operating frequency.
And thirdly, controlling the conduction or cut-off state of the diodes of the reconfigurable metamaterial units through the FPGA, and encoding the surface of the programmable metamaterial. Specifically, in the present embodiment, the state of the reconfigurable metamaterial unit when the diode is turned on is referred to as "1", and the state of the reconfigurable metamaterial unit when the diode is turned off is referred to as "0", so that the encoding of the surface of the programmable metamaterial is realized by controlling the operating state of the diode.
In this embodiment, a programmable metamaterial surface is placed in a near field region away from an antenna to be measured by several wavelengths, and a direction function of an electromagnetic wave emitted by the antenna to be measured passing through the programmable metamaterial surface is as follows:
exp represents an exponential function with e as a base, j is an imaginary number unit, and M, N is the number of rows and columns of a two-dimensional whole column formed by the reconfigurable metamaterial unit on the surface of the programmable metamaterial respectively; theta and
elevation and azimuth in any direction, Am,nAnd phim,nIs the amplitude and phase distribution of the field of the antenna to be measured on the surface unit of the programmable metamaterial, feFor each unit of the mode function, k0D is the size of the cell, the wavenumber in free space. The programmable metamaterial surface is composed of '0' and '1', if only the phase difference between the codes '1' and '0' is considered, and the relative phase response of the '0' element can be in feIn (2), the orientation coefficient of the metamaterial surface is as follows:
after an electromagnetic field passes through the surface of the programmable metamaterial, the amplitude and phase information of the antenna obtained by the probe under different codes are different, the surface of the metamaterial is equivalent to a measuring device in a CS (circuit switched) at the moment, a measuring matrix is randomly distributed from '0' to '1' according to an FPGA (field programmable gate array), and a signal Y (Y) obtained by the probe at the momentpWhen p is 1,2,3, L M, there are:
phi is a code consisting of 0 and 1, the coding state is controlled by the FPGA, the coding sequence can be set according to needs, the coding sequence does not need to be changed after the setting is finished, the probe measures along the set scanning plane, the step length is increased, and the scanning points are reduced.
And step four, respectively measuring the near field distribution of each reconfigurable metamaterial unit in the states of diode conduction and diode cut-off, and calculating the electric field received by the probe according to the Huygens principle.
Specifically, after the electromagnetic wave passes through the programmable metamaterial, the electric field of the electromagnetic wave has different measurement distributions in different encoding states, and at this time, the electric field is:
in this way, the electromagnetic wave is acquired by the probe through the programmable metamaterial, and the induced current acquired by the probe can be expressed as:
wherein
Is the normal direction of the probe, and according to the standard huygens principle, the electric field received by the probe can be obtained as follows:
where I is the unit dyadic, ω denotes the angular frequency of the electromagnetic field, μ0And k0Respectively the vacuum magnetic permeability and the electromagnetic wave number,
it is shown that two gradient operations are performed,
the method includes the steps that for a Green function in a free space, r represents a position vector of a programmable metamaterial surface, r' represents a position vector of a probe, signals are transmitted by an antenna to be tested and acquired by the probe through a digital metamaterial surface, and original information is restored through a Total Variation (TV) reconstruction algorithm.
Specifically, when calculating the electric field, the programmable metamaterial surface is regarded as a measurement matrix in the CS, and the signals acquired by the probe are represented as:
wherein, ymRecord value, x, for the m-th antenna measured by the probenRepresenting the original signal of the antenna to be tested,
is the encoding state of the programmable metamaterial; and then recovering the original signal through a CS recovery algorithm.
The invention is further illustrated below with reference to specific examples and the accompanying drawings.
The antenna near-field rapid measurement system in the embodiment comprises an antenna near-field measurement system and a programmable metamaterial surface, wherein 1 represents an antenna to be measured, 2 is the metamaterial surface, 3 is a probe, 4 is an FPGA system, an FPGA is used for controlling a metamaterial surface coding sequence through a computer, and the probe obtains electric field distribution after passing through the metamaterial surface to obtain a radiation field of the antenna to be measured.
In the example, the programmable metamaterial unit comprises a substrate, a metal through hole and a diode, wherein the dielectric substrate adopts TaconicT L X-8, the dielectric constant is 2.55, the loss tangent is 0.0019, the thickness h is 0.762mm, the shape of the unit is shown in fig. 3(a), the specific parameters of the unit structure are w is 12mm, w0 is 6.65mm, l0 is 6.23, w2 is 0.6mm, and R is 0.35mm, two states of the metamaterial unit are obtained by controlling the conduction or non-conduction of the diode, and the equivalent circuit of the Pin diode under the two states of conduction (ON) and cut-OFF (OFF) is shown in fig. 3 (b).
In this embodiment, the transmission performance of the linearly polarized wave under the vertical incidence obtained by the Ansoft HFSS simulation software is as shown in fig. 3(c) (d), the on and off of the diode have the maximum phase difference at 12GHz, which is the operating frequency, and the projection loss is small at different bias voltages.
In this example, the number of reconfigurable metamaterial units on the surface of the programmable metamaterial is M × N, specifically, M may be 25, the turn-on and turn-off of the units are determined by external bias direct current voltage, and the coding sequence is controlled by the FPGA, the source antenna is a rectangular probe, the antenna to be measured is a horn antenna with a working frequency of 12GHz, the surface of the programmable metamaterial is placed in the near field region of the antenna to be measured, the coding of the programmable metamaterial is set as required, at this time, the surface of the metamaterial has the coding of "1" and "0", an observation matrix can be perfectly formed to observe signals, and the electric field obtained by the probe can be obtained according to the state distribution of the surface units of the programmable metamaterial:
i is a unit dyadic vector, and the unit dyadic vector is,
and r is a position vector of the surface of the programmable metamaterial and r' is a position vector of the probe.
The measurement method provided by the invention can recover the original signal by only 40% of the original data. The results are shown in fig. 4 and fig. 5, fig. 4(a) is the original image of the measured near field amplitude of the antenna, fig. 4(b) is the image of the invention which collects 40% data recovery, and it can be seen from the figure that the near field amplitude can be basically recovered. Fig. 5(a) and 5(b) are a conventional sampling phase original graph and a sparse sampling recovery graph of the present invention, respectively, and it can be seen that the present invention can perfectly recover near-field phase information, and can obtain good signal recovery while reducing measurement time. In addition, in the embodiment, only 40% of data acquisition is needed to recover the original signal, thereby reducing the data processing amount and improving the efficiency.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention are equivalent to or changed within the technical scope of the present invention.
Claims (8)
1. The antenna near field rapid measurement system is characterized by comprising an FPGA, a programmable metamaterial surface and a probe; the probe is arranged on one surface of the programmable metamaterial, and the other surface of the programmable metamaterial is used for placing an antenna to be tested;
the programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array; each reconfigurable metamaterial unit is loaded with a diode; the FPGA encodes the surface of the programmable metamaterial by controlling the on-off of the diodes in each reconfigurable metamaterial unit;
the probe acquires near-field data of the antenna to be tested, which penetrates through the surface of the programmable metamaterial, and reconstructs the radiation characteristic of the antenna to be tested according to the near-field data.
2. The antenna near-field rapid measurement system of claim 1, wherein on the surface of the programmable metamaterial, the distance between adjacent reconfigurable metamaterial units is half a wavelength of the operating frequency; the working frequency is the frequency with the largest phase difference of the reconfigurable metamaterial unit under two states of diode conduction and diode cut-off.
3. The antenna near field rapid measurement system of claim 1, wherein the dielectric substrate in the reconfigurable metamaterial unit adopts TaconicT L X-8.
4. The antenna near-field rapid measurement system of claim 3, wherein the dielectric substrate has a dielectric constant of 2.55, a loss tangent of 0.0019, and a thickness h of 0.762 mm.
5. The antenna near-field rapid measurement system of claim 1, wherein the number of reconfigurable metamaterial units on the surface of the programmable metamaterial is 25 × 25.
6. A method for quickly measuring the near field of an antenna is characterized by comprising the following steps:
firstly, a programmable metamaterial surface is arranged between a probe and an antenna to be detected, and the programmable metamaterial surface comprises a plurality of reconfigurable metamaterial units distributed in a two-dimensional array;
adding a diode on each reconfigurable metamaterial unit to obtain a frequency with the maximum phase difference of each reconfigurable metamaterial unit under two states of diode conduction and diode cutoff as a working frequency;
controlling the conduction or cut-off state of the diodes of the reconfigurable metamaterial units through the FPGA, and encoding the surface of the programmable metamaterial;
and respectively measuring the near field distribution of each reconfigurable metamaterial unit in the states of diode conduction and diode cut-off, and calculating the electric field received by the probe according to the Huygens principle.
7. The antenna near-field rapid measurement method according to claim 6, characterized in that when calculating the electric field, the programmable metamaterial surface is regarded as a measurement matrix in the CS, and the signals acquired by the probe are represented as:
wherein, ymRecord value, x, for the m-th antenna measured by the probenRepresenting the original signal of the antenna to be tested,
is the encoding state of the programmable metamaterial;
and then recovering the original signal through a CS recovery algorithm.
8. The antenna near-field rapid measurement method according to claim 6 or 7, characterized in that on the surface of the programmable metamaterial, the distance between adjacent reconfigurable metamaterial units is half wavelength of the working frequency.
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| CN107110948A (en) * | 2014-11-12 | 2017-08-29 | Emscan公司 | Reactive near antenna measurement |
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Application publication date: 20200714 |