WO2022067477A1

WO2022067477A1 - Method for far-field estimation and apparatus

Info

Publication number: WO2022067477A1
Application number: PCT/CN2020/118732
Authority: WO
Inventors: Arai Masami; Arai Hiroyuki
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2022-04-07
Also published as: CN116235061A

Abstract

Provided is a method for measuring far-field characteristics of an antenna, where the method comprising: measuring, by at least one probe located in a near-field region, an amplitude of an electric field generated by antenna elements of the antenna, wherein the number of probe (s) for measuring the amplitude of the electric field is M, the number of the antenna elements is N, and M is equal to or less than N; estimating, by a processor, current distribution on the antenna based on the measured amplitude of the electric field; and estimating, by the processor, the far-field characteristics based on the estimated current distribution.

Description

METHOD FOR FAR-FIELD ESTIMATION AND APPARATUS

TECHNICAL FIELD

The present disclosure relates to a method for measuring far-field characteristics of an antenna having multiple antenna elements and an apparatus implementing the method. For example, the method and apparatus may apply to an antenna implemented in a device such as a mobile phone, a smart phone, a tablet, or a personal computer.

BACKGROUND

In recent years, high frequency wireless products adopt an antenna-in-package (AIP) that an antenna and a high frequency circuit are integrated in a package. Generally, such AIP wireless products do not have an antenna connector that may be used for acquiring amplitude and phase data via a network analyzer. From these circumstances, over-the-air (OTA) measurement is becoming more important and attracting attention at manufacturing sites of such products, for example.

In regard to the OTA measurement, a conventional method for estimating far-field characteristics based on results of a near-field measurement require both the amplitude and phase data. The near-field measurement of this conventional method requires scanning an electric field around the antenna by moving a scanning point stepwise, and acquiring the phase data based on a scanning result at each scanning point. Since a movement interval of the scanning point is set to be less than a half wavelength of the field, in a high frequency range (e.g. 28GHz band) , this method takes much longer time than measuring time acceptable at the manufacturing sites.

Another conventional method known as a compact antenna test range (CATR) may reproduce a far-field environment in an anechoic chamber by using a reflector and acquire amplitude data of a plane wave in the far-field environment. Although this method may estimate the far-field characteristics without the phase information, the method requires adjustment of position and orientation of the reflector with high accuracy in order to achieve a required performance. Further, the chamber including the reflector is much larger than an acceptable volume at the manufacturing sites.

SUMMARY

Embodiments provide a method for measuring far-field characteristics of an antenna having multiple antenna elements and an apparatus implementing the method. For example, the method and apparatus may apply to an antenna implemented in a device such as a mobile phone, a smart phone, a tablet, or a personal computer.

A first aspect of the embodiments provides a method for measuring far-field characteristics of an antenna. In a first possible implementation form of the first aspect, the method comprises: measuring, by at least one probe located in a near-field region, an amplitude of an electric field generated by antenna elements of the antenna, wherein the number of probe (s) for measuring the amplitude of the electric field is M, the number of the antenna elements is N, and M is equal to or less than N; estimating, by a processor, current distribution on the antenna based on the measured amplitude of the electric field; and estimating, by the processor, the far-field characteristics based on the estimated current distribution.

According to the first possible implementation form of the first aspect, the far-field characteristics may be obtained based on the estimated current distribution derived from the measured amplitude by each probe without phase information of an electromagnetic field in the near-field region. Accordingly, the method enables measurements of the far-field characteristics while avoiding use of phase information of an electromagnetic field in the near-field region. In addition, the method may estimate the far-field characteristics in a short time since the processor just performs a simple calculation to derive the current distribution from M (M≤N) measurement results. Further, since the method may estimate the far-field characteristics based on amplitude information in the near-field region, a volume of a measurement system for the OTA measurement to which the method is applied is much smaller than a volume of the anechoic chamber for the CATR.

Optionally, the estimating, by the processor, the current distribution on the antenna may specifically comprise: estimating current on each of the antenna elements based on the measured amplitude of the electric field. Also, the estimating, by the processor, the far-field characteristics may specifically comprise: estimating the far-field characteristics based on the estimated current.

A second possible implementation form of the first aspect provides: the method according to the first possible implementation form of the first aspect, where N is equal to or more than two, and M is equal to or more than two and is equal to or less than N. According to the second possible implementation form of the first aspect, at least two probes may measure amplitudes of the electric field in the near-field respectively, thereby detecting a peak direction of radiation based on the amplitudes simultaneously measured by the at least two probes.

A third possible implementation form of the first aspect provides: the method according to the first possible implementation form of the first aspect, where N is equal to or more than two, and N is equal to M. According to our experimental study and simulation results, a distance between a first plane in which the M probes are arranged and a second plane in which the N antenna elements are arranged that is required to achieve an adequate performance gets shorter as M gets closer to N. Therefore, a condition that N is equal to M makes it possible to reduce a volume of a measurement system to which the method is applied. This may contribute to downsizing of inspection lines in the manufacturing sites of the wireless products.

Optionally, the estimating, by the processor, the far-field characteristics may specifically comprise: estimating at least one of equivalent isotropic radiated power (EIRP) , equivalent isotropic sensitivity (EIS) and total radiated power (TRP) , as the far-field characteristics. For example, EIRP and TRP may be used as indicators for evaluating characteristics of radiation power, and EIS may be used as an indicator for evaluating characteristics of sensitivity of a receiver.

A fourth possible implementation form of the first aspect provides: the method according to any one of the first to third possible implementation form of the first aspect, where each probe is arranged in a first plane parallel to a second plane in which the antenna elements are arranged, and a distance between an aperture center of the antenna and each probe is set to be a common distance. Optionally, if N is equal to M, each of the M probes may be arranged opposed to one corresponding antenna element among the N antenna elements.

A fifth possible implementation form of the first aspect provides: the method according to any one of the first to fourth possible implementation form of the first aspect, the estimating, by the processor, the far-field characteristics specifically comprises: calculating a difference between intensity values measured by a probe pair, wherein M is equal to or more than two; and estimating a direction of a maximum amplitude of the electric field in a far-field region based on the calculated difference corresponding to each probe pair. Also, the difference may be calculated for each combination of two different probes. According to the fifth possible implementation form of the first aspect, the direction of the maximum amplitude of the electric field in the far-field region may be obtained in a short time.

Optionally, the estimating the current on each of the antenna elements may specifically comprise: estimating I _n indicating current on a n-th antenna element, for each of n from 1 to N, based on the following equation:

where Xp _m indicates a position of a m-th probe, and C _mn is a coefficient associated with a given radiation pattern of the n-th antenna element around a direction from the n-th antenna to the m-th probe and a distance between the n-th antenna and the m-th probe.

Optionally, C _mn may be provided by the following equation:

where A _n indicates a given amplitude coefficient of the n-th antenna, j is an imaginary unit, k indicates a wave number of the electric field, r _mn indicates the distance between the n-th antenna and the m-th probe, and D _n indicates the given radiation pattern of the n-th antenna element around the direction from the n-th antenna to the m-th probe.

Optionally, the estimating the far-field characteristics based on the estimated current corresponding to the antenna elements may specifically comprise: estimating a far-field E _f based on the following equation:

where

indicates a radiation direction based on a reference position of the antenna, r indicates a distance from the reference position to an observation point, and (xs _n, ys _n) indicates a position of the n-th antenna element based on the reference position; and estimating the far-field characteristics based on the estimated far-field.

A second aspect of the embodiments provides an apparatus for measuring far-field characteristics of an antenna. In a first possible implementation form of the second aspect, the apparatus comprises: at least one probe located in a near-field region, configured to measure an amplitude of an electric field generated by antenna elements of the antenna, wherein the number of probe (s) for measuring the amplitude of the electric field is M, the number of the antenna elements is N, and M is equal to or less than N; and a processor configured to estimate current distribution on the antenna based on the measured amplitude of the electric field, and estimate the far-field characteristics based on the estimated current distribution.

According to the first possible implementation form of the second aspect, the far-field characteristics may be obtained based on the estimated current distribution derived from the measured amplitude by each probe without phase information of an electromagnetic field in the near-field region. Accordingly, the apparatus enables measurements of the far-field characteristics while avoiding use of phase information of an electromagnetic field in the near-field region. In addition, the apparatus may estimate the far-field characteristics in a short time since the processor just performs a simple calculation to derive the current distribution from M (M≤N) measurement results. Further, since the apparatus may estimate the far-field characteristics based on amplitude information in the near-field region, a volume of a measurement system for the OTA measurement using the apparatus is much smaller than a volume of the anechoic chamber for the CATR.

Optionally, the processor may be specifically configured to: estimate current on each of the antenna elements based on the measured amplitude of the electric field, and estimate the far-field characteristics based on the estimated current.

A second possible implementation form of the second aspect provides: the apparatus according to the first possible implementation form of the second aspect, where N is equal to or more than two, and M is equal to or more than two and is equal to or less than N. According to the second possible implementation form of the second aspect, at least two probes may measure amplitudes of the electric field in the near-field respectively, thereby detecting a peak direction of radiation based on the amplitudes simultaneously measured by the at least two probes.

A third possible implementation form of the second aspect provides: the apparatus according to the first possible implementation form of the second aspect, where N is equal to or more than two, and N is equal to M. According to our experimental study and simulation results, a distance between a first plane in which the M probes are arranged and a second plane in which the N antenna elements are arranged that is required to achieve an adequate performance gets shorter as M gets closer to N. Therefore, a condition that N is equal to M makes it possible to reduce a volume of a measurement system for the OTA measurement using the apparatus. This may contribute to downsizing of inspection lines in the manufacturing sites of the wireless products.

Optionally, the processor may be specifically configured to estimate at least one of equivalent isotropic radiated power (EIRP) , equivalent isotropic sensitivity (EIS) and total radiated power (TRP) , as the far-field characteristics. For example, EIRP and TRP may be used as indicators for evaluating characteristics of radiation power, and EIS may be used as an indicator for evaluating characteristics of sensitivity of a receiver.

A fourth possible implementation form of the second aspect provides: the apparatus according to any one of the first to third possible implementation form of the second aspect, where each probe is arranged in a first plane parallel to a second plane in which the antenna elements are arranged, and a distance between an aperture center of the antenna and each probe is set to be a common distance. Optionally, if N is equal to M, each of the M probes may be arranged opposed to one corresponding antenna element among the N antenna elements.

A fifth possible implementation form of the second aspect provides: the processor is specifically configured to: calculate a difference between intensity values measured by a probe pair, wherein M is equal to or more than two, and estimate a direction of a maximum amplitude of the electric field in a far-field region based on the calculated difference corresponding to each probe pair. Also, the difference may be calculated for each combination of two different probes. According to the fifth possible implementation form of the second aspect, the direction of the maximum amplitude of the electric field in the far-field region may be obtained in a short time.

Optionally, the processor may be specifically configured to estimate I _n indicating current on a n-th antenna element, for each of n from 1 to N, based on the following equation:

Optionally, C _mn may be provided by the following equation:

Optionally, the processor may be specifically configured to estimate a far-field E _f based on the following equation:

where

indicates a radiation direction based on a reference position of the antenna, r indicates a distance from the reference position to an observation point, and (xs _n, ys _n) indicates a position of the n-th antenna element based on the reference position, and to estimate the far-field characteristics based on the estimated far-field.

A third aspect of the embodiments provides a non-transitory computer readable storage medium storing a program to cause a computer to implement the method according to any one of the first to fifth possible implementation form of the first aspect. A fourth aspect of the embodiments provides a program to cause a computer to implement the method according to any one of the first to fifth possible implementation form of the first aspect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram for describing hardware elements of an apparatus according to the embodiment of the present disclosure,

FIG. 2 is a schematic block diagram for describing functions of the processor according to the embodiment of the present disclosure,

FIG. 3A is a schematic diagram for describing positional relationship between an observation point and antenna elements, and FIG. 3B is a schematic diagram for describing positional relationship between a DUT and the observation point,

FIG. 4 is a schematic diagram for describing a field strength in an example that the antenna comprises 3-antenna elements,

FIG. 5 is a schematic diagram for describing exemplary arrangements of a probe array and an antenna array according to the embodiment of the present disclosure,

FIG. 6 is a schematic diagram for describing exemplary arrangements of 4-probes and 4-antenna elements according to the embodiment of the present disclosure,

FIG. 7A shows a graph representing an estimated current of an antenna element, FIG. 7B shows a graph representing an estimated EIRP based on the maximum electric field at a center of the antenna,

FIG. 8 is a flow chart for describing a procedure to estimate far-field characteristics according to the embodiment of the present disclosure,

FIG. 9 is a schematic diagram for describing exemplary arrangements of 3-probes and 4-antenna elements according to first variation of the embodiment of the present disclosure, and

FIG. 10 is a schematic diagram for describing exemplary arrangements of 2-probes and 4-antenna elements according to second variation of the embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions of the embodiments, referring to the accompanying drawings. It will be understood that the embodiments described below are not all but just some of embodiments relating to the present disclosure. It is to be noted that all other embodiments which may be derived by a person skilled in the art based on the embodiments described below without creative efforts shall fall within the protection scope of the present disclosure.

Following embodiment relates to an OTA measurement, and provides a method for measuring far-field characteristics of an antenna having multiple antenna elements and an apparatus implementing the method. Those embodiments may apply to an antenna implemented in a device such as a mobile phone, a smart phone, a tablet, or a personal computer.

(Exemplary configuration of the apparatus) Following describes an exemplary configuration of the apparatus with reference to FIGs. 1 and 2. FIG. 1 is a schematic block diagram for describing hardware elements of an apparatus according to the embodiment of the present disclosure. FIG. 2 is a schematic block diagram for describing functions of the processor according to the embodiment of the present disclosure.

FIG. 1 shows an apparatus 10 and a probe set 20. The apparatus 10 is an example of the apparatus according to the embodiment of the present disclosure, may be utilized for measuring far-field characteristics of an antenna. As shown in FIG. 1, the apparatus 10 includes measurement circuitry 11, a processor 12 and a memory 13.

In an example of FIG. 1, the measurement circuitry 11 is connected with the probe set 20 including at least one probe that may measure an amplitude of an electric field from the antenna. The number of probe (s) included in the probe set 20 is M, and M is equal to or more than one. If the antenna has N (N≥2) antenna elements, M is configured to be equal to or less than N. When performing operation for measuring the far-field characteristics, the probe set 20 is located in a near-field region of the antenna, and the measurement circuitry 11 acquires measurement results from each of the M probe (s) in the probe set 20.

The processor 12 obtains the measurement results from the measurement circuitry 11 and estimates a current distribution on the antenna based on the measurement results. Further, the processor 12 estimates the far-field characteristics based on the estimated current distribution on the antenna. Detail functional features of the processor 12 will be explained later.

The processor 12 may be processing circuitry such as a central processing unit (CPU) , a field-programmable gate array (FPGA) , an application specific integrated circuit (ASIC) , a graphical processing unit (GPU) , or the like. Also, the processor 12 is connected with the memory 13 such as a read-only memory (ROM) , a random access memory (RAM) , a flash memory, a hard disk drive (HDD) , a solid state drive (SSD) , or the like. The memory 13 may store a program to cause the apparatus 10 to perform the operation for measuring the far-field characteristics. The program may be obtained by the apparatus 10 via a non-transitory computer readable storage medium, or a local and/or wide network for communicating with a server managing the program, and then installed to the memory 13.

Following describes functional features of the processor 12 with reference to FIG. 2. As shown in FIG. 2, the processor 12 includes a near-field measurement portion 121, a current estimation portion 122, and a far-field characteristics estimation portion 123. Each portion may be implemented as at least one software component. Optionally, at least a part of the portions may be implemented by at least one hardware component other than the processor 12 or combination of the at least one hardware component and the processor 12. Such variation of the embodiments may be within a scope of the embodiments of the present disclosure.

In an example of FIG. 2, the near-field measurement portion 121 obtains the measurement results via the measurement circuitry 11. As mentioned above, the measurement results include the amplitude information indicating an amplitude of the electric field at each of the M probes in the near-field region. Namely, the near-field measurement portion 121 obtains information of field distribution in the near-field region.

In an example of FIG. 3A, three

antenna elements

21, 22 and 23 are arranged on a plane corresponding to a surface of a device under test (DUT) . FIG. 3A is a schematic diagram for describing positional relationship between an observation point and antenna elements. In this example, xp1, xp2, xp3 and xp represent X-coordinates of the

antenna elements

21, 22 and 23 and the observation point, respectively. Also, r1, r2 and r3 represent distances between the

antenna elements

21, 22 and 23 and the observation point, respectively. Distance d represents a distance between the observation point and the DUT.

Since the M probes are arranged in the near-field region, the distance d is configured to satisfy a condition provided by the following equation (1) , where D represents an aperture size of the DUT as shown in FIG. 3B. FIG. 3B is a schematic diagram for describing positional relationship between the DUT and the observation point. The condition provided by the equation (1) may be derived based on the following condition: de-d<λ/2, where de represents a distance between the observation point TP and the furthest antenna element in the DUT.

Under the conditions explained above with reference to FIGs. 3A and 3B, distribution of field strength observed at several observation points may be as shown in FIG. 4. FIG. 4 is a schematic diagram for describing a field strength in an example that the antenna comprises 3-antenna elements. In an example of FIG. 4, four solid lines corresponding to different d values are illustrated. As shown in FIG. 4, the field strength tends to be concentrated around a center of the

antenna elements

21, 22 and 23, and a peak height of the field strength tends to decrease with distance from the DUT. The M probes arranged in the near-field region may detect such distribution of the field strength, that is, the field distribution E ₁ ... E _M.

The current estimation portion 122 estimates current distribution on the antenna based on the measurement results obtained from the near-field measurement portion 121. Specifically, the current estimation portion 122 may specifically estimate current on each of the N antenna elements based on the amplitude of the electric field at each of the M probes.

For example, the current estimation portion 122 may estimate I _n indicating current on a n-th antenna element, for each of n from 1 to N, based on the following equation (2) :

where Xp _m indicates a position vector of a m-th probe, and C _mn is a coefficient associated with a given radiation pattern of the n-th antenna element around a direction from the n-th antenna to the m-th probe and a distance between the n-th antenna and the m-th probe.

Specifically, C _mn may be provided by the following equation (3) :

where A _n indicates a given amplitude coefficient of the n-th antenna, j is an imaginary unit, k indicates a wave number of the field, k=2π/λ where λ is a wave length of the field, and r _mn indicates the distance between the n-th antenna and the m-th probe. rmn is defined by the following equation (4) :

where (xp _m, yp _m) corresponds to the position vector Xp _m of the m-th probe based on the reference position, and (xs _n, ys _n) indicates a position of the n-th antenna element based on the reference position. In addition, D _n indicates the given radiation pattern of the n-th antenna element and may be represented by

indicates the direction from the n-th antenna to the m-th probe.

may be obtained beforehand by computer simulation and/or experimental measurement with respect to each antenna element.

Equation (2) may be expressed in a matrix form as the following equation (5) . The current estimation portion 122 may compute the inverse matrix [C _mn] ^-1 and calculate the current distribution (I ₁ ... I _N) based on the inverse matrix and the measured field distribution (E ₁ ... E _M) .

The far-field characteristics estimation portion 123 estimates the far-field characteristics based on the current distribution on the antenna that is estimated by the current estimation portion 122. For example, the far-field characteristics estimation portion 123 may estimate a far-field E _f based on the following equation (6) :

where

indicates a radiation direction based on a reference position of the antenna, r indicates a distance from the reference position to an observation point, and (xs _n, ys _n) indicates a position of the n-th antenna element based on the reference position.

In some exemplary cases, the far-field characteristics estimation portion 123 may estimate at least one of equivalent isotropic radiated power (EIRP) , equivalent isotropic sensitivity (EIS) and total radiated power (TRP) , as the far-field characteristics. EIRP and TRP may be used as indicators for evaluating characteristics of radiation power, and EIS may be used as an indicator for evaluating characteristics of sensitivity of a receiver. For example, TRP may be calculated based on the following equation (7) :

Optionally, if M is equal to or more than two, the far-field characteristics estimation portion 123 may calculate a difference between intensity values (i.e. amplitudes of the electric field) measured by a probe pair. For example, the difference may be calculated for each combination of two different probes. Further, the far-field characteristics estimation portion 123 may estimate a maximum amplitude direction of the electric field in the far-field region based on the calculated differences. This makes it possible to obtain the maximum amplitude direction of the electric field in the far-field region in a short time.

According to the configuration of the apparatus 10 described above, the far-field characteristics may be obtained based on the estimated current distribution derived from the measured amplitude by each probe without phase information of an electromagnetic field in the near-field region. Namely, the apparatus 10 enables measurements of the far-field characteristics while avoiding use of phase information of the electromagnetic field in the near-field region. This makes it possible to estimate the far-field characteristics in a short time since the processor 12 just performs a simple calculation to derive the current distribution from M measurement results. In addition, a volume of a measurement system for the OTA measurement using the apparatus 10 is much smaller than a volume of the anechoic chamber for the CATR.

Following further describes arrangements of the N antenna elements and the M probes with reference to FIG. 5. FIG. 5 is a schematic diagram for describing exemplary arrangements of a probe array and an antenna array according to the embodiment of the present disclosure.

As shown in FIG. 5, the M probes (P1 ... P4 in FIG. 5) may be arranged in a first plane parallel (a probe plane in FIG. 5) to a second plane (a X-Y plane in FIG. 5) in which the N antenna elements (S1 ... S4 in FIG. 5) are arranged, and a distance between an aperture center of the antenna and each probe may be a common distance. In an example of FIG. 5, both N and M are equal to four, each of the M probes is arranged opposed to a corresponding antenna element among the N antenna elements. Although M should be set to be equal to or less than N, M may be one and also be equal to or more than two. In some exemplary cases, measurements by at least two probes facilitate detecting a peak radiation direction. In addition, according to our experimental study and simulation results, a distance between the first and second planes that is required to achieve an adequate performance gets shorter as M gets closer to N. Thus, configuration that N is equal to M is preferable in some cases, and this configuration makes it possible to reduce a volume of a measurement system for the OTA measurement using the apparatus 10 and the probe set 20. This may contribute to downsizing of inspection lines in the manufacturing sites of the wireless products.

Following describes exemplary implementation of the apparatus 10 explained above with reference to FIG. 6. FIG. 6 is a schematic diagram for describing exemplary arrangements of 4-probes and 4-antenna elements according to the embodiment of the present disclosure.

FIG. 6 shows

probes

201, 202, 203 and 204, and an antenna 300 including

antenna elements

301, 302, 303 and 304. In an example of FIG. 6, a probe plane on which the

probes

201, 202, 203 and 204 are located is set to be parallel to a surface of the antenna 300, and each probe is arranged opposed to a corresponding antenna element. In addition, a distance between an antenna center surrounded by the

antenna elements

301, 302, 303 and 304 and each of

probes

201, 202, 203 and 204 is configured to be common. z0 in FIG. 6 indicates a distance between the probe plane and the surface of the antenna 300, and a lower limit of z0 usable for accurate estimation of current distribution on the antenna 300 depends on the number of the probes. Optionally, a first distance along a X-axis direction between adjacent two probes may be configured to be equal to a second distance along a Y-axis direction between adjacent two probes. In this example, the first and second distance may be set to be 10mm.

As mentioned above, current on each of the

antenna elements

301, 302, 303 and 304 may be estimated based on amplitude data from the

probes

201, 202, 203 and 204. If d = 30mm and frequency = 28GHz, the estimated current is as a solid line shown in FIG. 7A. FIG. 7A shows a graph representing an estimated current of an antenna element. A dash-dotted line in FIG. 7A shows a theoretical value, and FIG. 7A shows that the solid line is adequately close to the dash-dotted line.

In addition, EIRP of the electric field from the antenna 300 may be estimated based on the estimated current distribution, and the estimated EIRP is as a solid line shown in FIG. 7B. FIG. 7B shows a graph representing an estimated EIRP based on the maximum electric field at a center of the antenna. A dash-dotted line in FIG. 7B shows a calculation result based on the maximum electric field at a measurement plane on which the four probes are located. FIG. 7B shows that the solid line is adequately close to the dash-dotted line.

As described in detail above, the above-mentioned embodiments enable to implement the OTA measurement in a short time, reduce a required volume for placing the measurement system, and obtain accurate measurement results.

(Method for the far-field measurement) Following describes a procedure to estimate far-field characteristics with reference to FIG. 8. FIG. 8 is a flow chart for describing a procedure to estimate far-field characteristics according to the embodiment of the present disclosure.

At a step of S11, the measurement circuitry 11 of the apparatus 10 performs measuring, by using the probe set 20 including at least one probe located in the near-field region, an amplitude of an electric field generated by antenna elements of the antenna. The number of probe (s) for measuring the amplitude of the electric field is M, and the number of the antenna elements is N, where M is equal to or less than N. N is equal to or more than two, and M may be equal to or more than two. Optionally, N may be equal to M. In some examples, each probe may be arranged in a first plane parallel to a second plane in which the antenna elements are arranged, and a distance between an aperture center of the antenna and each probe may be configured to be a common distance.

At a step of S12, the processor 12 of the apparatus 10 performs estimating, by using the processor 12, current distribution on the antenna based on the measured amplitude of the electric field. Specifically, the processor 12 may perform estimating current on each of the antenna elements based on the measured amplitude of the electric field. For example, the processor 12 may compute the inverse matrix [C _mn] ^-1 on the basis of the above-mentioned equation (3) , and calculate the current distribution (I ₁ ... I _N) on the basis of the above-mentioned equation (4) , the inverse matrix [C _mn] ^-1 and the measured field distribution (E ₁ ... E _M) .

At a step of S13, the processor 12 of the apparatus 10 performs estimating the far-field characteristics based on the above-mentioned equation (6) and the estimated current distribution. Optionally, the processor 12 may perform calculating a difference between amplitudes of the electric field that are measured by each probe pair, and estimating a direction of the maximum amplitude of the electric field in the far-field region based on the calculated difference corresponding to each probe pair. The far-field characteristics may be at least one of equivalent isotropic radiated power (EIRP) , equivalent isotropic sensitivity (EIS) and total radiated power (TRP) , for example.

(First variation of the embodiment) Following describes a first variation of the above-mentioned embodiment with reference to FIG. 9. FIG. 9 is a schematic diagram for describing exemplary arrangements of 3-probes and 4-antenna elements according to first variation of the embodiment of the present disclosure.

As shown in FIG. 9, in the first variation, a probe set 210 including three

probes

211, 212 and 213 is used for measuring the electric field in the near-field. Each probe may be arranged in a probes plane parallel to the surface of the antenna 300, and a distance between an aperture center of the antenna 300 and each probe may be configured to be a common distance. z1 in FIG. 9 indicates a distance between the probes plane and the surface of the antenna 300. Since the number of probes in the probe set 210 of FIG. 9 is less than the number of probes in the probe set 200 of FIG. 6, a lower limit of z1 usable for accurate estimation of current distribution on the antenna 300 is larger than the lower limit of z0. However, even if the first variation of the embodiment is applied to a measurement system for the OTA measurement using the apparatus 10 and the probe set 210, a volume of the measurement system is much smaller than a volume of the anechoic chamber for the CATR.

(Second variation of the embodiment) Following describes a second variation of the above-mentioned embodiment with reference to FIG. 10. FIG. 10 is a schematic diagram for describing exemplary arrangements of 2-probes and 4-antenna elements according to second variation of the embodiment of the present disclosure.

As shown in FIG. 10, in the second variation, a probe set 220 including two probes 221 and 222 is used for measuring the electric field in the near-field. Each probe may be arranged in a probes plane parallel to the surface of the antenna 300, and a distance between an aperture center of the antenna 300 and each probe may be configured to be a common distance. z2 in FIG. 10 indicates a distance between the probes plane and the surface of the antenna 300. Since the number of probes in the probe set 220 of FIG. 10 is less than the number of probes in the probe set 210 of FIG. 9, a lower limit of z2 usable for accurate estimation of current distribution on the antenna 300 is larger than the lower limit of z1. However, even if the second variation of the embodiment is applied to a measurement system for the OTA measurement using the apparatus 10 and the probe set 220, a volume of the measurement system is much smaller than a volume of the anechoic chamber for the CATR.

Similar to the above-mentioned variations, M may be changed within a range of 1 to N. Those variations may be within a scope of the above-described embodiment according to the present disclosure.

The foregoing disclosure merely discloses exemplary embodiments, and is not intended to limit the protection scope of the present invention. It will be appreciated by those skilled in the art that the foregoing embodiments and all or some of other embodiments and modifications which may be derived based on the scope of claims of the present invention will of course fall within the scope of the present invention.

Claims

A method for measuring far-field characteristics of an antenna, comprising:

measuring, by at least one probe located in a near-field region, an amplitude of an electric field generated by antenna elements of the antenna, wherein the number of probe (s) for measuring the amplitude of the electric field is M, the number of the antenna elements is N, and M is equal to or less than N;

estimating, by a processor, current distribution on the antenna based on the measured amplitude of the electric field; and

estimating, by the processor, the far-field characteristics based on the estimated current distribution.
The method according to claim 1, wherein

the estimating, by the processor, the current distribution on the antenna specifically comprises: estimating current on each of the antenna elements based on the measured amplitude of the electric field; and

the estimating, by the processor, the far-field characteristics specifically comprises: estimating the far-field characteristics based on the estimated current.
The method according to claim 1 or 2, wherein

N is equal to or more than two, and M is equal to or more than two and is equal to or less than N.
The method according to claim 1 or 2, wherein

N is equal to or more than two, and N is equal to M.
The method according to any one of claims 1 to 4, wherein

the estimating, by the processor, the far-field characteristics specifically comprises: estimating at least one of equivalent isotropic radiated power (EIRP) , equivalent isotropic sensitivity (EIS) and total radiated power (TRP) , as the far-field characteristics.
The method according to any one of claims 1 to 5, wherein

each probe is arranged in a first plane parallel to a second plane in which the antenna elements are arranged, and a distance between an aperture center of the antenna and each probe is set to be a common distance.
The method according to any one of claims 1 to 6, wherein

the estimating, by the processor, the far-field characteristics specifically comprises:

calculating a difference between intensity values measured by a probe pair, wherein M is equal to or more than two; and

estimating a direction of a maximum amplitude of the electric field in a far-field region based on the calculated difference corresponding to each probe pair.
An apparatus for measuring far-field characteristics of an antenna, comprising:

at least one probe located in a near-field region, configured to measure an amplitude of an electric field generated by antenna elements of the antenna, wherein the number of probe (s) for measuring the amplitude of the electric field is M, the number of the antenna elements is N, and M is equal to or less than N; and

a processor configured to estimate current distribution on the antenna based on the measured amplitude of the electric field, and estimate the far-field characteristics based on the estimated current distribution.
The apparatus according to claim 8, wherein the processor is specifically configured to:

estimate current on each of the antenna elements based on the measured amplitude of the electric field, and

estimate the far-field characteristics based on the estimated current.
The apparatus according to claim 8 or 9, wherein

N is equal to or more than two, and M is equal to or more than two and is equal to or less than N.
The apparatus according to claim 8 or 9, wherein

N is equal to or more than two, and N is equal to M.
The apparatus according to any one of claims 8 to 11, wherein the processor is specifically configured to estimate at least one of equivalent isotropic radiated power (EIRP) , equivalent isotropic sensitivity (EIS) and total radiated power (TRP) , as the far-field characteristics.
The apparatus according to any one of claims 8 to 12, wherein

each probe is arranged in a first plane parallel to a second plane in which the antenna elements are arranged, and a distance between an aperture center of the antenna and each probe is set to be a common distance.
The apparatus according to any one of claims 8 to 13, wherein the processor is specifically configured to:

calculate a difference between intensity values measured by a probe pair, wherein M is equal to or more than two, and

estimate a direction of a maximum amplitude of the electric field in a far-field region based on the calculated difference corresponding to each probe pair.
A non-transitory computer readable storage medium storing a program to cause a computer to implement the method according to any one of claims 1 to 7.