JP2020024165A - Radiated power estimation method - Google Patents

Abstract

To provide a radiated power estimation technology capable of estimating total radiated power efficiently and highly accurately in a short time.SOLUTION: A radiated power estimation method is provided for finding total radiated power of a transmitting antenna in a measuring system comprising a base station device, a transmitting antenna, a turntable for rotating the transmitting antenna, a receiving antenna for receiving a radio wave coming from the transmitting antenna, and an electric power measuring instrument for measuring electric power of the received radio wave. The radiated power estimation method has: Step S1 of the electric power measuring instrument measuring electric power in a portion in a bandpass of a signal that is transmitted by the transmitting antenna and received by the receiving antenna in each of predetermined angle samples, while the turntable continuously rotates; Step S2 of the electric power measuring instrument specifying an angle sample having a ratio of the electric power obtained in each angle sample to the maximum value of the electric power of equal to or more than a predetermined threshold; Step S3 of the electric power measuring instrument measuring the electric power at the whole signal bandwidth with a specified angle sample; and Step S4 for estimating the total radiated power from the electric power obtained in Step S3.SELECTED DRAWING: Figure 4

Description

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

  2. Description of the Related Art In an array antenna system having a directivity having a strong radiation intensity in a specific direction, an active antenna in which an antenna and a transmitter are integrated may be used. When the output terminal of the transmitter is not equipped with a connector for monitoring in the active antenna, the transmission power measurement is performed by measuring the total radiated power radiated from the antenna to the space. A method of measuring the total radiated power radiated into the space is called an Over The Air (OTA) measurement method, and an OTA measurement system is used. For example, Non Patent Literature 1 discloses an OTA measurement system.

  With reference to FIG. 1, a conventional OTA measurement system 900 for measuring the transmission power of the base station device 91 and a measurement method will be described. The OTA measurement system 900 includes a base station apparatus 91, a transmission antenna 92 connected to the base station apparatus 91, and a turntable 96 on which the transmission antenna 92 is mounted (in this example, the base station apparatus 91 is also mounted on the turntable 96). ), A receiving antenna 93 installed at a position separated by a predetermined distance from the transmitting antenna 92, and a power measuring device 95 for measuring the power of radio waves received by the receiving antenna 93.

  The receiving antenna 93 receives a radio wave radiated from the transmitting antenna 92 toward the receiving antenna 93. The power measuring device 95 measures the power of the radio wave received by the receiving antenna 93. The propagation loss is determined from the gain of the receiving antenna 93 and the distance between the transmitting antenna 92 and the receiving antenna 93. Therefore, the power of the radio wave radiated from the transmitting antenna 92 can be estimated from the gain and the propagation loss of the receiving antenna 93 by measuring the received power with the power measuring device 95. When measuring the total radiated power, the receiving antenna 93 is moved on a spherical surface around the transmitting antenna 92, and the radiated power in each direction is estimated from the received power measured by the power measuring device 95, and the radiated power in each direction is estimated. The sum of the radiated power of Alternatively, the receiving antenna 93 is fixed, the turntable 96 is biaxially rotated in a combination of the horizontal direction and the vertical direction, the radiated power in each direction is estimated from the received power measured by the power meter 95, and the radiated power in each direction is estimated. The sum of the radiated powers may be obtained.

  Generally, the operation of the turntable 96 includes continuous rotation and step rotation. Continuous rotation is a method of rotating continuously at a constant speed without stopping the rotation. Step rotation is a rotation method in which rotation is temporarily stopped for each angle sample. Since continuous rotation has a constant time required to move from a certain angle to the next angle, the reception power measurement at a certain angle needs to be completed before the turntable 96 reaches the next angle.

  When information is transmitted as in mobile communication, a signal transmitted from a base station device is a modulated signal having a bandwidth (hereinafter, referred to as a band signal). The band signal power is the integrated power in the band. However, in general, when the measurement accuracy is fixed, the wider the broadband signal, the longer the time required for the measurement.

Toyo Technica, "OTA Measurement System (Anechoic Chamber)", [online], Toyo Technica, [Search August 2, 2018], Internet <URL: http://www.toyo.co.jp/emc/products / detail / id = 1754>

  According to the conventional OTA power measurement system 900, when measuring the total radiated power, it is necessary to measure the radiated power at each of a plurality of measurement points on a spherical surface around the transmission antenna 92. When the turntable 96 rotates continuously, it takes a long time to measure the integrated power of the broadband signal, so that it is necessary to reduce the continuous rotation speed. Further, in order to ensure the measurement accuracy, it is necessary to perform measurement at a large number of measurement points on the spherical surface. However, the measurement by the step rotation is not realistic because the time required for scanning on the spherical surface becomes long.

  Therefore, an object of the present invention is to provide a radiation power estimation technique that can efficiently and accurately estimate the total radiation power in a short time.

  The method of estimating radiated power according to the present invention includes a base station apparatus, a transmitting antenna connected to the base station apparatus, a turntable for rotating the transmitting antenna, a receiving antenna for receiving a radio wave coming from the transmitting antenna, A radiation power estimation method for estimating the total radiation power of a transmitting antenna in a measurement system including a power measurement device for measuring electric power of a radio wave, wherein the power measurement device is a predetermined method while the turntable continuously rotates. A first step of measuring the power in a portion of the band of the signal transmitted by the transmitting antenna and received by the receiving antenna at each of the angular samples; A second step of identifying an angular sample whose ratio of the determined power is equal to or greater than a predetermined threshold; and a power measuring device measuring the power of the entire signal band with the determined angle sample. That has a third step, a fourth step of estimating the total radiated power from the power obtained in the third step.

  According to the present invention, it is possible to efficiently and accurately estimate the total radiation power in a short time.

FIG. 2 is a diagram illustrating a configuration example of a measurement system. The figure explaining the definition of polar angle (theta) and azimuth (phi). The figure which shows an example of the angular distribution of EIRP radiated from a base station apparatus. FIG. 4 is a processing flowchart in the embodiment.

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

<First embodiment>
Hereinafter, the total radiation power estimation method of the first embodiment will be described. The radiated power estimation method of the first embodiment is a method of estimating total radiated power (Total Radiated Power: TRP) in all directions in the conventional OTA power measurement system 900 shown in FIG.

Generally, TRP is defined by equation (1).

EIRP (θ, φ) is an equivalent isotropic radiated power (Effective Isotropic Radiated Power), and for the transmission power Pt, when the directivity of the antenna is isotropic, the radiation power density at a distance r from the transmission source is Pt / 4πr ² is defined. EIRP (θ, φ) is expressed by equation (2) using EIRP _θ (θ, φ) and EIRP _φ (θ, φ) obtained by measuring electric field components in the θ, φ directions.

In the evaluation of the total radiated power, the sum of EIRP in all directions, that is, the polar angle θ and the azimuth angle φ in the spherical coordinate system shown in FIG. 2 is obtained. Since the actual measurement seeking EIRP at discrete measuring points (angles sample), total radiated power TRP is, theta and phi direction of the division number of each When N _theta and N _phi, is expressed by equation (3) You. Here, θ _i = (i−1) Δθ, φ _j = (j−1) Δφ, Δθ = π / N _θ , and Δφ = 2π / N _φ . For this reason, the total number N of angle samples is N = N _θ N _φ .

  In addition, the turntable 96 includes a two-axis rotation mechanism to obtain the rotation angles θ and φ. Such a rotating mechanism is well-known, and thus description thereof is omitted. Continuous rotation and step rotation are possible for each axis. As described above, continuous rotation is a rotation method in which rotation is continuously stopped at a constant speed without stopping rotation, and step rotation is a rotation method in which rotation is temporarily stopped for each angle sample. That is, the time required for one rotation is longer in the step rotation than in the continuous rotation.

  When power measurement is performed on each angle sample, a predetermined time is required for power measurement.This time differs depending on the type of measurement signal and measurement accuracy, and the longer the measurement time becomes, the wider the signal becomes and the higher the accuracy becomes. It costs. Specifically, when measuring the band signal with the power measuring device 95, it is important to appropriately set a resolution bandwidth (RBW) in order to ensure accuracy. Arbitrary RBW can be set, and the smaller the RBW, the higher the frequency resolution is and the more detail in the spectrum can be measured more faithfully. Also, when the RBW is reduced, the noise power is also reduced, so that the noise level is reduced and the dynamic range is improved. That is, even small power can be measured with high accuracy. However, if the RBW is reduced, the response becomes slow, so that the frequency must be gently swept, and it takes a long time for the measurement. That is, when the measurement signal is a wideband signal, a long measurement time is required if the RBW is reduced to improve the accuracy.

  Further, the measurement time is affected by the operation of the turntable 96. In the case of a continuous rotation in which the time required for one rotation is short in order to reduce the measurement time, the power measurement at a certain angle sample must be completed before the turntable 96 reaches the next angle. If it cannot be completed, the measured power at the angle sample is not accurate, and a large error occurs in the total radiation power estimation. On the other hand, when the rotation speed of the continuous rotation is reduced or when the step rotation is adopted, the time required for the measurement becomes longer in both cases. When the step rotation is adopted, the received power can be accurately measured at any angle sample by rotating the turntable 96 to the next angle sample after completing the power measurement at a certain angle sample. However, in general, in the case of the step rotation, as the number of angle samples increases, the TRP measurement accuracy improves, but the measurement time increases in proportion to the number of angle samples.

  Here, FIG. 3 shows an example of an angular distribution of EIRP radiated from an actual base station apparatus. In general, the main lobe of the transmitting antenna 92 of the base station device 91 is designed so that the radiated power becomes maximum in the direction of the area, so that the angular distribution of EIRP becomes maximum in a specific direction. In the other direction, there is power radiation by the side lobe, but the radiation power of the side lobe is smaller than the radiation power of the main lobe.

Table 1 shows the ratio (measurement sample rate) of the number of angle samples in which the ratio of EIRP to the maximum EIRP in each angle sample is equal to or larger than the threshold to the total number of angle samples (measurement sample rate) and the measurement error at that time. I have. The error criterion is the TPR obtained from all angle samples. From Table 1, it can be seen that the larger the threshold (ie, the closer the threshold is to the maximum EIRP), the smaller the measurement sample rate and the greater the measurement error, and the smaller the threshold (ie, the further the threshold is away from the maximum EIRP), the greater the measurement sample rate. It can be seen that the measurement error becomes smaller as the distance increases. When the threshold value is, for example, −10 dB, the measurement sample rate is 7% in the base station device A and 3% in the base station device B, but the measurement errors are −0.8 dB and −1.2 dB, respectively (that is, When the threshold value is -10 dB, the measurement sample rate is sufficiently small but the measurement error is large. On the other hand, when the threshold value is -40 dB, the measurement error is 0 dB in the base station apparatuses A and B. The rate is 91% in the base station apparatus A and 81% in the base station apparatus B (that is, when the threshold value is −40 dB, the measurement error is sufficiently small but the measurement sample rate is large). Therefore, in order to estimate the total radiated power efficiently and with high accuracy in a short time, it is preferable to set a threshold value that can achieve the smallest possible measurement error with the smallest possible sample rate. The threshold value can be changed depending on the configuration of the measurement system 900, measurement conditions (for example, required accuracy), etc., but preferably, the measurement sample rate is 50% or less and the measurement error is -0.3 dB or more. It is preferably set as a value to be set. From Table 1, it is preferable that the threshold value is a predetermined value of -15 dB or less and -30 dB or more. If the threshold value is about -20 dB, the error is very small, and the measurement sample rate is 20% (about 1/5 of the whole). As described above, the threshold is determined in advance based on a trade-off between the measurement sample rate and the measurement error in some simulation models. Note that the simulation model does not have to be created based on an actual measurement system.

  In view of such a feature, in the first embodiment, first, the power measuring device 95 transmits the transmission antenna 92 at each of the predetermined angle samples while the turntable 96 continuously rotates at a constant speed. In addition, the reception power EIRP (θ, φ) in a part of the band of the signal received by the reception antenna 93 is measured (step S1). Since the angular resolution at this time affects measurement accuracy, it is preferable that the resolution be relatively small. When the transmission signal from the base station apparatus 91 is a band signal, the signal power of the entire band cannot be measured in the continuous rotation as described above, so that the power of only a part of the signal band is reduced. Measure. If the power cannot be measured, for example, the measurement bandwidth is updated to half, and the power measuring device 95 again measures the received power of each angular sample by continuous rotation. This process is performed until the power measurement result for one rotation is obtained.

Next, the power measuring device 95 obtains the maximum value of EIRP (θ, φ) obtained by continuous rotation, and calculates the ratio of the EIRP (θ, φ) of each angle sample to the maximum value of EIRP (θ, φ). Calculate and specify an angle sample whose ratio is equal to or greater than a preset threshold (step S2). Here, the coordinates of the specified angle sample are represented by (θ _i , φ _j ), (i, j) ∈ {(a _p , b _q ) | a _p ∈ {a ₁ , a ₂ , ..., a _n }, b _q ∈ {b ₁ , b ₂ , ..., b _m }}, _ak ∈ {1,2, ..., N _θ }, b _h ∈ {1,2, ..., N _φ }, k∈ {1, 2,…, n}, h∈ {1,2,…, m}. However, (i, j) does not necessarily cover all elements of the set (a _p , b _q ).

Then, in the step rotation of the turntable 96, the power measuring device 95 measures the power of the entire signal band in each of the angle samples specified in the process of step S2 (step S3). The power at each angle sample obtained by this processing is calculated as EIRP (θ _i , φ _j ), (i, j) ∈ {(a _p , b _q ) | a _p ∈ {a ₁ , a ₂ , ..., a _n }, b _q ∈ {b ₁ , b ₂ , ..., b _m }}, a _k ∈ {1, 2, ..., N _θ }, b _h ∈ {1, 2, ..., N _φ }, k∈ {1, 2, ..., n}, h} {1, 2, ..., m}.

Finally, the power measuring device 95 obtains the EIRP (θ _i , φ _j ), (i, j) ∈ {(a _p , b _q ) | a _p ∈ {a ₁ , a ₂ , ..., a _n }, b _q ∈ {b ₁ , b ₂ , ..., b _m }}, _ak ∈ {1,2, ..., N _θ }, b _h ∈ A TRP is obtained using {1, 2,..., N _φ }, k∈ {1, 2,..., N}, h∈ {1, 2,..., M} and equation (4) (step S4). Here, Δθ = π / N _θ and Δφ = 2π / N _φ .

  Since the radiated power receives a constant attenuation according to the separation distance between the transmitting antenna 92 and the receiving antenna 93 regardless of the band, the angle dependence of the band signal and the angle dependence of some band signals in the band signal are: equal. That is, the angular distribution of the radiated power by the transmitting antenna 92 is equal to the angular distribution of the radiated power in some of the bands, and the ratio of the EIRP of each angular sample to the maximum EIRP is also equal in both cases. In addition, if EIRP having a certain intensity or higher is measured, highly accurate TRP can be estimated. Therefore, measurement time can be reduced by reducing the number of angle samples while maintaining accuracy.

  According to the estimation method of the first embodiment, the radiant power distribution in a part of the band is measured in a short time by continuous rotation, an angular sample having a large contribution to TRP is selected, and the radiant power of the entire band in the angular sample is selected. TRP estimation can be performed in a short time and with high accuracy by accurately acquiring by the step rotation.

<Embodiment 2>
In the second embodiment, when the transmission signal from the base station device 91 is a band signal in the process of step S1, the power measuring device 95 measures the power at the band center frequency. In this case, the power measuring device 95 does not need to integrate the in-band power. Further, since the peak power is searched and the power is measured, the measurement accuracy is improved, and a high dynamic range can be estimated. This is particularly effective when the reception power is small.

  In each embodiment, by setting the threshold value to -20 dB, the number of angle samples can be reduced to 1/5 or less, and the measurement time can be reduced to 1/5 or less.

<Addendum>
In the specification and the claims, the order of processing procedures, sequences, flowcharts, and the like may be changed as long as there is no inconsistency.

  In the description and the claims, the input or output information or the like may be stored in a specific place (for example, a memory) or may be managed in a management table. Information to be input or output can be overwritten, updated, or added. The output information or the like may be deleted. The input information or the like may be transmitted to another device as needed.

  In the description and the claims, the determination may be made by a value represented by 1 bit (0 or 1) or by a Boolean value (Boolean: true or false). , May be performed by comparing numerical values (for example, comparison with a predetermined value).

  In the above-described embodiment, the notification of the predetermined information (for example, the notification of “X”) is not limited to being performed explicitly, and is implicit (for example, the notification of the predetermined information is not performed). May be performed.

  In the description and the claims, the terms "system" and "network" may be used interchangeably.

  In the description and in the claims, the term "connected" and any variants thereof mean a direct or indirect connection between two or more elements, It may include the presence of one or more intermediate elements between the elements. The connection between elements may be a physical connection, a logical connection, or a combination thereof. As used in the specification and the claims, two elements may involve the use of one or more electrical wires, cables and / or printed electrical connections, as well as some non-limiting and non-exhaustive examples. As such, they can be considered "connected" to each other by using electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency, microwave, and light (both visible and invisible) regions.

  In the description and the claims, ordinal numbers (for example, the prefix "No." combined with a Chinese number or an arithmetic digit "No. ○"), unless otherwise noted, It is not intended that the elements modified by ordinal or combined with the classifier be limited by the order of the elements or the amount of the elements. The use of classifiers is used merely as a convenient way of distinguishing two or more elements from each other, unless otherwise specified. Therefore, for example, the phrase “first X” and the phrase “second X” are expressions for distinguishing two Xs, and do not necessarily mean that the total number of Xs is 2, or It does not necessarily mean that the first X must precede the second X.

  In the description and claims, the term "comprise" and its conjugations are used as non-exclusive expressions. For example, the sentence "X includes A and B" does not deny that X includes a component other than A and B (for example, C). In addition, in the specification and claims, when a sentence includes the term “include” or its inflection includes a word combined with a negative word, the sentence refers to the term “include” or the object of the inflection. Only. Thus, for example, the sentence "X does not include A and B" acknowledges that X may include components other than A and B. Further, the term "or" as used in the description or the claims is not intended to be an exclusive or.

  The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Various changes and modifications are allowed without departing from the spirit of the present invention. The embodiments selected and described are illustrative of the principles of the invention and its practical application. The invention may be used in various embodiments with various modifications or variations, which will be determined according to the expected application. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims, and should be construed in accordance with the breadth given fairly, lawfully and fairly. It is intended that the same protection be provided.

Claims (4)

A base station device, a transmitting antenna connected to the base station device, a turntable for rotating the transmitting antenna, a receiving antenna for receiving a radio wave coming from the transmitting antenna, and measuring the power of the received radio wave A radiation power estimation method for estimating the total radiation power of the transmission antenna in a measurement system including a power measuring device that performs
The power meter measures the power in a part of the band of the signal transmitted by the transmitting antenna and received by the receiving antenna in each of the predetermined angle samples while the turntable continuously rotates. A first step of measuring;
A second step in which the power measuring device specifies the angle sample in which the ratio of the power obtained in each of the angle samples to the maximum value of the power is equal to or greater than a predetermined threshold value;
A third step of measuring the power in the entire band of the signal with the specified angular sample, and a fourth step of estimating a total radiated power from the power obtained in the third step; A radiation power estimation method comprising: The radiation power estimation method according to claim 1,
In the first step, the part is a center frequency. In the radiation power estimation method according to claim 1 or 2,
The threshold is a ratio of the number of angle samples at which the ratio between the equivalent isotropic radiation power and the maximum equivalent isotropic radiation power at each angle sample is equal to or greater than the threshold value to the total number of angle samples in the prior simulation model. A radiation error estimating method, which is determined in advance based on a trade-off between a measurement error with respect to total radiation power obtained from all angle samples and a measurement error. In the radiation power estimation method according to claim 1 or 2,
The radiation power estimation method, wherein the threshold value is a predetermined value of -15 dB or less and -30 dB or more.

Images