JP7233312B2 - Radiation power estimation method - Google Patents

Description

The present invention relates to radiation power estimation technology for estimating the radiation power of radio waves radiated into space.

The radiated power of an array antenna system that realizes transmission and reception of radio waves with a large gain in a predetermined direction is represented by, for example, EIRP (Equivalent Isotropic Radiated Power). Estimation of radiated power into space is performed using an OTA (Over The Air) measurement system. For example, Non-Patent Document 1 discloses an OTA measurement system.

A conventional OTA measurement system 900 and a radiation power estimation method will be described with reference to FIG. The OTA measurement system 900 includes a base station device 91, a transmitting antenna 92 connected to the base station device 91, a turntable 96 on which the base station device 91 and the transmitting antenna 92 are placed, and radio waves coming from the transmitting antenna 92. , a power measuring device 95 that measures the power of the radio wave received by the receiving antenna 93 , and an estimator 97 that estimates the radiation power of the transmitting antenna 92 .

The receiving antenna 93 receives radio waves radiated from the transmitting antenna 92 . The power measuring device 95 measures the power P _r of the radio waves received by the receiving antenna 93 . The antenna gain G _r of the receiving antenna 93 is known, and the free space propagation loss L between the transmitting antenna 92 and the receiving antenna 93 is calculated using the wavelength λ of the radio wave and the spacing R between the transmitting antenna 92 and the receiving antenna 93. , the estimating unit 97 calculates the radiation power of the transmitting antenna ₉₂ , that is, the _radiation It is possible to estimate the EIRP of the transmitted radio wave. EIRP (unit: dB) is specifically estimated by equation (1). L appearing in equation (1) is given by equation (2). Equation (2) holds in the far field.

When estimating the EIRP in a direction different from the predetermined direction, the EIRP in the direction is calculated from the power P _r measured by the power measuring device 95 by moving the receiving antenna 93 on a spherical surface centered on the transmitting antenna 92. can be estimated. Alternatively, by fixing the receiving antenna 93 and rotating the turntable 96 along two axes in a combination of the horizontal and vertical directions, the EIRP in that direction can be estimated from the power P _r measured by the power measuring device 95. good.

Using equation (2), the receive antenna 93 is placed in the far field of the transmit antenna 92 . That is, the transmitting antenna 92 and the receiving antenna 93 are installed with an interval R not less than the predetermined distance R _p . This predetermined distance R _p is the distance from the center of the aperture plane of the transmitting antenna 92 to the boundary between the far field and the near field, and is given by Equation (3) (Non-Patent Document 2). As shown in Equation (3), the distance R _p is proportional to the square of the aperture length D of the transmitting antenna 92 and inversely proportional to the wavelength λ of the radiated electromagnetic wave. This predetermined distance R _p is hereinafter referred to as the separation distance R _p .

Toyo Technica, "OTA measurement system (anechoic chamber)", [online], Toyo Technica, [searched on June 3, 2019], Internet <URL: http://www.toyo.co.jp/emc/ products/detail/id=1754> The Institute of Electronics, Information and Communication Engineers, “Antenna Domain”, [online], The Institute of Electronics, Information and Communication Engineers, [searched June 3, 2019], Internet <URL: http://ieice-hbkb.org/files/04 /04gun_02hen_02.pdf>

For example, if the aperture length D of the transmission antenna 92 is lengthened to improve the gain, the separation distance R _p is lengthened. As a result, the problem arises that a large anechoic chamber must be prepared in order to carry out correct OTA measurements.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a radiated power estimation technique capable of estimating the radiated power well even when the antenna spacing R is set to be shorter than the separation distance R _p required for good power estimation. do.

A radiation power estimation method of the present invention includes a transmitting antenna, a receiving antenna for receiving radio waves arriving from the transmitting antenna, and a power measuring instrument for measuring the power of the radio waves received by the receiving antenna. is a radiation power estimation method for estimating the radiation power of a transmitting antenna in a measurement system in which the spacing R is shorter than the separation distance determined from the wavelength λ of the radio wave and the aperture length _D of the transmitting antenna. Step, power P _r , antenna gain G _r of the receive antenna, free space propagation loss L, and a correction value C to correct for the effect on the estimated radiated power due to the spacing R being smaller than the separation distance. and a second step of estimating the EIRP of the transmit antenna from (R).

According to the present invention, the correction value C(R) corrects the effect on the estimate of the radiated power of the transmitting antenna due to the spacing R being smaller than the separation distance, which is required for good power estimation. Even if the antenna spacing R is set to be shorter than the separation distance, the radiated power can be estimated satisfactorily.

The figure which shows the structural example of an OTA measurement system. FIG. 4 is a diagram for explaining that the estimation of EIRP by Equation (1) is inappropriate; FIG. 4 is a diagram for explaining the positional relationship between a transmitting antenna and a receiving antenna; FIG. 4 is a diagram for explaining that EIRP estimation by Equation (4) is appropriate; FIG. 4 is a processing flow diagram in the embodiment; FIG. 4 is a diagram for explaining a change range of the positional relationship between the transmitting antenna and the receiving antenna;

Embodiments of the present invention will be described with reference to the drawings.

The OTA measurement system used in the embodiment has the same configuration as the conventional OTA measurement system 900 shown in FIG. Accordingly, the description of the OTA measurement system 900 discussed above is incorporated herein, thereby omitting the description of the OTA measurement system used in the embodiments. The radiation power estimation method of the embodiment is a method of estimating the EIRP of the transmission antenna 92 in the OTA measurement system using the procedure described later.

First, it will be explained that estimation of the EIRP of the transmitting antenna 92 using equation (1) is not preferable when performing OTA measurements with an antenna spacing R shorter than the separation distance R _p . Free space propagation loss L=P _t + obtained from power P _r measured under the condition that all of the transmission power P _t , the antenna gain G _t of the transmission antenna 92, and the antenna gain G _r of the reception antenna 93 are known. The relationship between G _t + G _r - P _r (experimental value; unit dB) and antenna spacing R, and the relationship between free space propagation loss L (calculated value; unit dB) and antenna spacing R according to Equation (2), is shown in FIG. It can be understood from FIG. 2 that the shorter the antenna interval R, the greater the deviation between the experimental value of the free space propagation loss L and the calculated value of the free space propagation loss L. FIG. In other words, it can be understood that EIRP estimation by equation (1) is not preferable when performing OTA measurements in a situation where the antenna interval R is shorter than the separation distance _Rp . Also, since the degree of divergence is affected by the physical shape of the transmitting antenna 92, etc., it is difficult to estimate the EIRP of other transmitting antennas based on the specific experimental values shown in FIG.

Therefore, in this embodiment, the EIRP is estimated using a correction value C(R) that corrects for the effect on the EIRP estimate due to the antenna spacing R being shorter than the separation distance _Rp . That is, in this embodiment, EIRP (unit: dB) is estimated using Equation (4), which is a modification of Equation (1).

Hereinafter, the details of the embodiment will be described by taking as an example the case where the transmitting antenna 92 is a linear array antenna in which M antenna elements 921 are linearly arranged. M is a predetermined integer of 2 or more. Note that when the transmitting antenna 92 is a linear array antenna, the antenna gain G _t of the transmitting antenna 92 includes the array antenna gain. As shown in FIG. 3 (an example of M=8), M antenna elements 921 of the transmitting antenna 92 are arranged at equal intervals on one straight line Q1, and the aperture planes of the M antenna elements 921 are the same. (a plane parallel to the straight line Q1), and the aperture planes of the M antenna elements 921 face the same direction. The aperture length D of the transmission antenna 92 is the distance between the centers of the aperture planes of the two antenna elements 921 located on the outermost side. The receiving antenna 93 is a single antenna, and the aperture plane of the receiving antenna 93 is parallel to the above plane. The transmitting antenna 92 and the receiving antenna 93 face each other. The antenna center of the transmitting antenna 92 (position at a distance D/2 from the center of the aperture of the outermost antenna element 921) and the antenna center of the receiving antenna 93 are on a straight line Q2 perpendicular to the straight line Q1.

The correction value C(R) depends on the reception phase difference based on variations in path length from each antenna element 921 to the reception antenna 93 when the aperture length d of the reception antenna 93 is sufficiently smaller than the aperture length D of the transmission antenna 92. Expressed in gain loss. When M is an even number, that is, M=2N (N is an integer), the path difference r between the distance R from the antenna center of the transmitting antenna 92 to the receiving antenna 93 and the distance R _n from the n-th antenna element 921 to the receiving antenna 93 Since _n (see FIG. 3) is approximately represented by the equation (7), the phase difference θ _{n (} R) is represented by the formula (6). Therefore, the correction value C(R) in the case of M=2N is the power of the composite vector of received signals based on the variation in path length (twice the numerator of equation (5)) and the power of each antenna element 921 to the receiving antenna 93 (5) as a ratio to the received signal power (twice the denominator of Equation (5)) when there is no path length variation. Here, n represents each integer of 1 or more and N or less.

Similarly, the correction value C(R) when M is an odd number, that is, M=2N−1 (N is an integer) is given by equation (8). The phase difference θ _n (R) appearing in equation (8) is given by equation (9).

Also, if the n-th antenna element 921 has a directional gain G _n , Equations (5) and (8) are changed to Equations (5a) and (8a), respectively.

In comparison with FIG. 2 _{, the power P r and the} correction value C( R) and the relationship between the free space propagation loss L = P _t + G _t + G _r - P _r - C (R) (experimental value; unit dB) and the antenna spacing R, and by equation (2) FIG. 4 shows the relationship between the free space propagation loss L (calculated value; unit: dB) and the antenna interval R. In FIG. From FIG. 4, it can be understood that the experimental value of the free space propagation loss L is close to the calculated value of the free space propagation loss L even when the antenna spacing R is short. That is, it can be understood that the EIRP can be estimated well by the equation (4) when the OTA measurement is performed in a situation where the antenna spacing R is shorter than the separation distance _Rp .

Therefore, in the embodiment, as shown in FIG. 5, the power measuring device 95 measures the power P _r of radio waves (step S1), and the estimating unit 97 measures the measured power P _r and , the known antenna gain G _r of the receiving antenna 93, the free-space propagation loss L which is the calculated value of equation (2), and the radiation of the transmitting antenna 92 due to the antenna spacing R being shorter than the separation distance R _p The EIRP of the transmitting antenna 92 is estimated from the correction value C(R) for correcting the effect on the estimated power value (step S2). The correction value C(R) is obtained from any one of formula (5), formula (8), formula (5a), and formula (8a) according to the above situation.

According to the embodiment, the influence on the estimate of the radiated power of the transmitting antennas 92 due to the antenna spacing R being shorter than the separation distance R _p is corrected by the correction value C(R). A good estimate of the radiated power can be obtained even if the OTA measurements are performed with an antenna spacing R smaller than the required spacing R _p for .

In this specification, "loss" is understood as a positive number. Equations (1) and (4) are notations based on this understanding. If the reader of this specification is in a position to understand "loss" as a negative number, then each of equations (2), (5), (8), (5a), and (8a) should be considered negative. By changing to numbered formulas, formulas (1) and (4) can be changed to formulas (1a) and (4a), respectively. The difference between the two is simply a difference in notation, and there is no substantial difference between the two.

Moreover, as another notation of the equations (1) and (4), for example, a notation based on the standpoint of distinguishing between measured values and non-measured values may be adopted. In equation (1), G _r and L, which are unmeasured values, may be defined as L ₁ =L−G _r and expressed as in equation (1b). In addition, in formula (4), even if G _r , L and C (R), which are unmeasured values, are defined as L ₂ =L + C (R) - G _r and expressed as in formula (4b) good.

In the embodiment, the antenna center of the transmitting antenna 92 and the antenna center of the receiving antenna 93 are on the straight line Q2 orthogonal to the straight line Q1, that is, the normal line of the plane on which the aperture planes of the M antenna elements 921 are arranged and the receiving antenna The angle Δ (see FIG. 6) formed by the normal to the opening surface of 93 is zero degrees, but it is not limited to such a form. It has been confirmed that good estimation can be performed even when the angle Δ is in the range of about ±15 degrees.

<Addendum>
Since a known power measuring device can be used as the power measuring device 95, detailed description thereof will be omitted. Also, the estimating unit 97 is implemented as a general-purpose computer having hardware resources such as a CPU (Central Processing Unit), memory, bus, and the like. A program stored in the memory and data necessary for processing this program (in the embodiment, the wavelength λ of the radio wave, the aperture length D of the transmitting antenna, the antenna interval R, the antenna gain G _r of the receiving antenna, N=ceiling (M/ 2); ceiling(·) is a ceiling function, power P _{r ,} etc.) is appropriately processed by the CPU. As a result, the CPU implements the function of the estimation unit 97 .

As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly specified otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

In the specification and claims, input or output information may be stored in a specific location (for example, memory) or managed in a management table. Input or output information or the like may be overwritten, updated, or appended. The output information and the like may be deleted. The entered information and the like may be transmitted to another device as necessary.

As used in the specification and claims, the term "connected" and all variations thereof means a direct or indirect connection between two or more elements, and two elements that are "connected" to each other. It can include the presence of one or more intermediate elements between elements. Connections between elements may be physical, logical, or a combination thereof. As used in the specification and claims, two elements are defined by the use of one or more wires, cables and/or printed electrical connections, and as some non-limiting and non-exhaustive examples , radio frequency, microwave, and optical (both visible and invisible) regions of wavelengths.

In the specification and claims, ordinal numbers (e.g., the prefix "dai" combined with Chinese numerals or Arabic numerals "○") are defined as It is not intended that the elements modified by ordinal numbers be limited by the order of such elements or the amount of such elements. The use of ordinal numbers is merely a convenient way of distinguishing two or more elements from each other, unless otherwise noted. Thus, for example, the phrases "first X" and "second X" are expressions for distinguishing between two Xs and do not necessarily mean that the total number of Xs is two, or It does not necessarily imply that the first X must precede the second X.

In the specification and claims, the term "include" and its inflections are used as non-exclusive expressions. For example, the statement "X contains A and B" does not deny that X contains components other than A and B (eg, C where C≠A and C≠B). Also, in the specification and claims, if a sentence contains the term "comprises" or an inflection thereof combined with a negative, the sentence refers to the object of the term "comprises" or its inflections. Only. Thus, for example, the statement "X does not contain A and B" allows for the possibility that X contains elements other than A and B. Furthermore, the term "or" as used in the specification or claims is not intended to be an exclusive or.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Various changes and modifications are allowed without departing from the gist of the present invention. The selected and described embodiments are intended to illustrate the principles of the invention and its practical application. The present invention may be used in various embodiments with various modifications or variations determined according to the expected application. All such modifications and variations are intended to be included within the scope of the invention as defined by the appended claims, when construed according to the breadth afforded in fairness, lawfulness and fairness, It is intended that the same protection be afforded.

Claims (2)

a transmitting antenna, a receiving antenna for receiving radio waves arriving from the transmitting antenna, and a power measuring device for measuring the power of the radio waves received by the receiving antenna, wherein a distance R between the transmitting antenna and the receiving antenna is A radiation power estimation method for estimating the radiation power of the transmitting antenna in a measurement system shorter than the separation distance determined from the wavelength λ of the radio wave and the aperture length D of the transmitting antenna,
a first step of measuring the power _Pr of the radio wave ;
A correction that corrects for the power P r , the antenna gain G r of the receive antenna, the free space propagation loss L, and the effects on the radiated power estimate due to the spacing R being less than the _{separation distance} . a second step of estimating the EIRP of the transmit antenna from the value C(R);
has
The transmitting antenna is a linear array antenna including M antenna elements,
EIRP = P _r - G _r + L + C (R) [unit: dB] ;
When M=2N,

and
For M=2N-1,

A radiation power estimation method characterized by: a transmitting antenna, a receiving antenna for receiving radio waves arriving from the transmitting antenna, and a power measuring device for measuring the power of the radio waves received by the receiving antenna, wherein a distance R between the transmitting antenna and the receiving antenna is A radiation power estimation method for estimating the radiation power of the transmitting antenna in a measurement system shorter than the separation distance determined from the wavelength λ of the radio wave and the aperture length D of the transmitting antenna,
a first step of measuring the power _Pr of the radio wave ;
A correction that corrects for the power P r , the antenna gain G r of the receive antenna, the free space propagation loss L, and the effects on the radiated power estimate due to the spacing R being less than the _{separation distance} . a second step of estimating the EIRP of the transmit antenna from the value C(R);
has
The transmitting antenna is a linear array antenna including M antenna elements,
EIRP = P _r - G _r + L + C (R) [unit: dB] ;
n represents an integer of 1 or more and N or less, and the directional gain of the n-th antenna element is G _n ,
When M=2N,

and
For M=2N-1,

A radiation power estimation method characterized by:

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