JP2793209B2 - Radiated electromagnetic field measurement device - Google Patents

Description

Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to a device for measuring a radiated electromagnetic field such as a wireless communication device, and more particularly to a radiated electromagnetic field capable of measuring over an entire solid angle. It relates to a measuring device.

(Prior Art) Generally, it is important to know in which direction and at what intensity an electromagnetic wave from an antenna is radiated in developing a high-performance antenna. In a wireless communication device with a built-in antenna such as a cordless telephone or a pager, the radiated electromagnetic wave is affected by electronic components surrounding the antenna, such as absorption and scattering. The radiation characteristics of the whole device must be considered. However, since miniaturization of equipment requires high-density mounting of electronic components including an antenna, it has become difficult to predict radiation characteristics of a built-in antenna.

It is extremely important to measure a radiation electromagnetic field over the entire solid angle of a device under test for developing a high-performance wireless communication device. From the radiation field measurement data over all solid angles,
It becomes possible to measure the radiated power of the device under test,
This also makes it possible to measure the radiation efficiency, which is an important characteristic of a small built-in antenna.

Thus, in wireless communication devices and various electronic devices,
It is required to accurately measure a radiation electromagnetic field over all solid angles, but a measuring device that satisfies this requirement has not yet been realized. Therefore, the present applicant has previously proposed an apparatus for measuring such a radiation electromagnetic field having a full solid angle (Japanese Patent Application No. 63-9889). This is a metal turntable on which an object to radiate electromagnetic waves is placed, a non-metallic rotation mechanism that rotates the turntable 360 ° about two orthogonal axes, and a non-metallic rotation mechanism that transmits power to this rotation mechanism. A power transmission mechanism, a power source connected to the power transmission mechanism, and a radio wave absorber covering the power source. It measures the field characteristics, and by integrating the measurement results of horizontal and vertical polarizations over the entire solid angle, the radiated power from the DUT can be obtained, and from the ratio of the radiated power to the incident power of the antenna, It is also possible to know the radiation efficiency of the antenna.

However, the antenna installation method is determined, such as an in-vehicle antenna used for a car phone, and the antenna whose radio wave arrival probability is not uniform over all solid angles is radiated as an antenna evaluation index. It is not always appropriate to use efficiency. The reason will be described below.

 First, let's check the definition of terms.

Radiation efficiency of antenna (ηa): Power incident on antenna
It is defined by the ratio of Din to the radiation power Pr from the antenna, and is a scalar constant (provided that the characteristics of the antenna do not change due to disturbance).

Antenna gain: There are several definitions for antenna gain:

Directivity gain (Gd) Antenna gain (Ga) Operational gain (Ge) Directivity gain Gd is a gain due to the fact that the radiation directivity of the antenna is not omnidirectional but has directivity. The antenna gain Ga is a gain in a case where the radiation efficiency of the antenna is taken into consideration and the antenna is perfectly matched. The operating gain Ge is an antenna gain that takes into account the radiation efficiency of the antenna and includes the reflection loss of the antenna.

Thus, there are three definitions of antenna gain, all of which are slacker values, but are a function of the antenna orientation. In general, the gain in the installation direction at which the maximum gain is obtained may be referred to as gain without particularly defining the installation direction of the antenna.

The radiation efficiency ηa of the antenna is a constant that does not affect the installation direction of the antenna, and the difference between the two is that the gain of the antenna is a function of the installation direction of the antenna.
The above-described antenna radiation efficiency ηa, directional gain Gd, antenna gain Ga, and operation gain Ge have the following relationship with each other.

Ga (θ, φ) = Gd (θ, φ) ηa Ge (θ, φ) = Ga (θ, φ) Lr where θ: elevation angle, θ: azimuth angle, Lr:
Here, what should be used as the evaluation function of the antenna is considered. This evaluation relates to the direction of arrival of radio waves and the directivity of the antenna. First, consider the following two cases.

The case where the arrival direction of the radio wave is completely random and the polarization changes randomly, or the case where the direction of the antenna is random (the use situation of the cordless telephone is close to this).

A case where the polarization of the arrival direction of the radio wave is constant and the direction of the antenna is also constant (the use state of the communication antenna between fixed stations corresponds to this).

As described above, it is necessary to select what is used as the evaluation index of the antenna depending on the arrival direction of the radio wave, the polarization, and the installation direction of the antenna. This requirement is particularly problematic when evaluating mobile antennas such as vehicle-mounted antennas.
However, at present, the evaluation function of the conventionally used antenna cannot be said to be appropriate due to the difficulty of measuring the radiation electromagnetic field over the entire solid angle of the antenna to be measured.

For example, a method which has been mainly used for evaluation of a vehicle-mounted antenna in the past is to measure a specific cut plane and obtain an average gain from the obtained wave pattern of one cut plane. In this method, the angle of arrival of the radio wave is evaluated as being constant, and the angle of arrival of the radio wave is evaluated in a situation different from the actual propagation path with a stochastic distribution. This is a practical problem.

(Problems to be Solved by the Invention) As described above, in the related art, when measuring the radiated electromagnetic field of the antenna, the measurement is performed assuming that the angle of arrival of the radio wave is constant, and therefore, particularly in the case of a vehicle-mounted antenna. In the case of a device under test in which the angle of arrival of a radio wave changes variously, there has been a problem that it is not possible to obtain an appropriate evaluation index under propagation characteristics in an actual use situation.

The present invention has been made in order to solve such a problem, and a radiated electromagnetic wave capable of measuring an effective radiated power, which is an evaluation index in an actual use state of an object to be measured, such as an in-vehicle antenna, in which the arrival angle of a radio wave changes variously. It is an object to provide a field measurement device.

[Configuration of the Invention] (Means for Solving the Problems) A radiation electromagnetic field measuring apparatus according to the present invention includes a turntable on which an object to be measured that emits electromagnetic waves is placed, and elevation of the turntable about two axes orthogonal to each other. Rotating mechanism that rotates 360 ° in the azimuth and azimuth directions, a power transmission mechanism that transmits power to the rotation mechanism, a power source connected to the power transmission mechanism, and a rotating mechanism that rotates the turntable. Measuring means for receiving radiated power of horizontally and vertically polarized waves from the object to be measured and measuring a radiated electromagnetic field over the entire solid angle of the object to be measured. From the arrival probability function of radio waves from each direction, the probability function of the polarization state and the probability function of the installation direction of the device under test, the arrival probability of horizontal polarization and vertical polarization from each direction to the device under test is obtained, This is regular The weighted functions for the received power of horizontal and vertical polarizations are used to calculate the effective power from the DUT by integrating the received powers of horizontal and vertical polarizations over all solid angles using these weighting functions. The radiated power is measured.

(Operation) As described above, according to the present invention, the horizontal polarization and the vertical polarization are determined by using the weighting functions for the reception power of the horizontal polarization and the vertical polarization that are predetermined in consideration of the actual use situation of the device under test. By integrating the received power of the polarized wave over the entire solid angle, the effective radiated power from the device under test is measured. The effective radiation power thus obtained gives an evaluation index suitable for evaluating the device under test (antenna) under actual propagation characteristics.

(Example) Hereinafter, an example of the present invention is described with reference to drawings.

FIG. 1 is a perspective view showing a schematic configuration of a radiation electromagnetic field measuring apparatus according to one embodiment of the present invention. In FIG.
Is a wireless communication device such as a portable telephone (cordless telephone) having a built-in antenna 50 and is mounted on the turntable 2. The turntable 2 can be rotated 360 ° in the elevation direction and the azimuth direction about two axes (azimuth axis and elevation axis) orthogonal to each other by a rotation mechanism. Rotation mechanism 3
Is as follows.

The turntable 2 is fixed to one end of an azimuth shaft 4. The azimuth shaft 4 is provided through one arm 5a of the inverted L-shaped arm 5, and a pulley 6 is connected to the other end. The azimuth spindle 7 is formed in a cylindrical shape, and has pulleys 8a and 8b at both ends. These pulleys 8a, 8b
The timing belt 9 is provided between the pulley 6 and the pulley 8b facing the other arm 5b of the arm 5.
Has been passed. The azimuth spindle 7 has a rotating mechanism 3
Are rotatably supported on support columns 10 for supporting the motor through bearings 11a and 11b (not shown).

On the other hand, an elevation shaft 12 is coaxially inserted inside the azimuth spindle 7. This elevation axis
One end of 12 is fixed to the other arm portion 5b of the arm 5. A pulley 13 is provided on the other end of the elevation shaft 12.

These azimuth shaft 4, arm 5, pulley 6, azimuth spindle 7, pulleys 8a and 8b, timing belt 9,
The rotation mechanism 3 is constituted by the bearings 11a and 11b, the elevation shaft 12, and the pulley 13.

The rotating mechanism 3 includes timing belts 15 and 16 and a pulley 1
Rotational power is transmitted from an azimuth drive device 19 and an elevation drive device 20 as power sources via a power transmission mechanism 14 composed of 7 and 18. That is, azimuth drive
19 is provided with a motor 21 and an azimuth encoder 22, and rotation of the motor 21 is transmitted to the pulley 17 via the azimuth encoder 22 and the timing belt 25. Similarly, the elevation driving device 20 is provided with a motor 23 and an elevation encoder 24, and the rotation of the motor 23 is controlled by a pulley via the elevation encoder 24 and the timing belt 26.
It is transmitted to 17.

Here, the present embodiment assumes that the lower limit frequency band of the measurement of the radiation electromagnetic field is the VHF band. In the VHF band or the UHF band, the radiation characteristics of the device under test are not as sharp as those in the microwave band. Therefore, it is difficult to install the device under test in a direction in which radio waves are emitted, avoiding a metal part. For this reason, reflection and scattering of the electromagnetic wave from the metal part occur. Therefore, in the present embodiment, the turntable 2, the rotation mechanism 3, the support column 10, and the power transmission mechanism 14 are all made of nonmetal, for example, FRP (fiber reinforced resin). The azimuth drive device 19 and the elevation drive device 20, which are power sources, are covered with radio wave absorption bands 27 and 28 made of, for example, ferrite. The non-metal used for the turntable 2, the rotation mechanism 3, the support column 10, and the power transmission mechanism 14 is the DUT 1
Ideally, the relative permittivity and relative permeability should be close to 1, that is, close to that of air, so as not to disturb the electromagnetic wave radiated from the wireless communication device. Disturb. For this reason, in this embodiment, the lightening holes 29, 30, and 31 are formed as much as possible in the turntable 2, the arm 5, the support pillar 10, and the like to further reduce the influence on the electromagnetic waves.

In the vicinity of the device under test 1, receiving antennas 32 and 33 for horizontal polarization and vertical polarization are installed. These antennas 32,
The output of 33 is detected in amplitude and phase by a network analyzer 34, and the amplitude signal and the phase signal are digitized by an A / D converter 35 and then supplied to an electronic computer 36. The electronic computer 36 performs a calculation process for measuring the effective radiated power from the DUT 1 to be described later, and D / A converters 37 and 38.
And control of the motors 21 and 23, display output control to the CRT display 39, and output to the digital video copy device 40. The computer 36 also receives signals from the azimuth encoder 22 and the elevation encoder 24.

Next, the operation of the device of this embodiment will be described. First, the entire device was placed in a radio wave anechoic chamber (not shown) with a volume of 10m x 7m x 7m, which was shielded by copper.
The device under test 1 is placed on the device, and receiving antennas 32 and 33 for horizontal polarization and vertical polarization are installed near the device under test 1. In this case, the position of the device under test 1 is located at a distance from the center of the quiet zone of the anechoic chamber due to the limitation of the height of the measuring device.
It was installed 1.5m below. In this experiment, the phase was not measured, and one log-periodic antenna was shared as the antennas 32 and 33, and this was selectively used for horizontal polarization and vertical polarization by being rotated. . In this state, a high-frequency signal having a frequency of 254 MHz is supplied from a high-frequency signal source (not shown) to the device under test to generate an electromagnetic wave.

Then, the azimuth driving device 19 and the elevation driving device 20 are operated to rotate the turntable 2 about the azimuth axis and the elevation axis. That is, when the motor 21 in the azimuth driving device 19 rotates, this rotation is performed by the azimuth encoder 22 to the timing belt 25 to
Pulley 17-Timing belt 15-Pulley 8a-Azimuth spindle 7-Pulley 8b-Timing belt 9-Pulley 6
The rotation of the turntable 2 is centered on the azimuth shaft 4.

On the other hand, when the motor 23 in the elevation driving device 20 rotates, this rotation is transmitted along the path of the elevation encoder 24, the timing belt 26, the pulley 18, the timing belt 16, the pulley 13, the elevation shaft 12, and the arm 5, The turntable 2 rotates about the elevation axis 12.

In this process, the azimuth encoder 22 and the elevation encoder 24 know the azimuth angle and the elevation angle of the DUT 1 from the rotation angles of the motors 21 and 23, respectively, and send the angle information to the electronic computer 36. In this case, as is apparent from the figure, even if the motor 21 is not rotating, the azimuth angle changes due to the rotation of the elevation shaft 12, so the output value of the azimuth encoder 22 is corrected according to the elevation angle, The azimuth angle needs to be determined. In addition, the azimuth angle and the elevation angle are also determined by the encoders 22 and 24 from the azimuth axis 4.
In addition, the output values of the encoders 22 and 24 are calculated and corrected in consideration of the power transmission ratio up to the elevation shaft 12 and the like.

The electronic computer 36 measures the radiated electromagnetic field from the DUT 1 according to the flowchart shown in FIG. First, in the pre-processing step S1, processing such as calibration of the apparatus, input of operation data, and Fris transfer equation is performed. Calibration is a network analyzer
34, the A / D converter 35, the high-frequency cable, and the like are performed using a standard attenuator, and the accuracy is 0.2 dB or less.

Next, the horizontal polarization reception power and the vertical polarization reception power received by the antennas 32 and 33 are sequentially taken in (step S
2) Next, after the interpolation processing is performed in step S3 on the data of the horizontal polarization reception power and the vertical polarization reception power, a radiation distribution pattern described later is displayed in step S4.

Next, in step S5, a radio wave arrival probability function (which is a radio wave arrival probability function from each direction to the device under test, which is hereinafter referred to as A), a polarization probability function (a polarization state Probability functions, specifically, a probability function of horizontal polarization and a probability function of vertical polarization, which are hereinafter referred to as B _H and B _V ), and a probability function of the installation direction of the device under test (hereinafter referred to as C), and weighting functions ω _H and ω _V with respect to the received power of the horizontally polarized wave and the vertically polarized wave are obtained in step S6 based on this. A specific method of obtaining these weight functions ω _H and ω _V will be described later. Then, by integrating the received power using these weight functions ω _H and ω _V , the effective radiated power from the DUT 1 is obtained. Further, if necessary, in step S8, a radiation efficiency, which is a ratio between the effective radiation power obtained in step S7 and the input power of the high-frequency signal to the DUT 1, is calculated, and a series of measurement operations ends. .

Next, the measurement operation in this embodiment will be described in more detail. First, the rotation mechanism 3 is applied to the radiation electromagnetic field characteristics of the DUT 1.
In order to evaluate the effect of the dielectric substance on the power transmission mechanism 14 and the half-wavelength dipole antenna, a small oscillator was mounted on the turntable 2 and the result measured with the device of this embodiment was compared with the theoretical value. did. If the measurement including not only the amplitude of the received signal but also the phase is performed, the polarization characteristics can be known, and the measurement data for the desired polarization can be obtained from the received signal phase difference between both polarizations. First, the purpose is to verify the radio wave characteristics of the rotation mechanism 3 and the rotation transmission mechanism 14, that is, whether these mechanisms 3 and 14 appear as air to radio waves. A measurement was made.

FIG. 3 shows a coordinate system for deriving the theoretical values. The required values are the electric field intensities E _H and E _V of both the horizontal and vertical polarization components at the observation point P in FIG. The position of the observation point P exists on a spherical surface having a radius r centered on the center of the antenna as shown in FIG. 3, and is determined by the elevation angle θ and the azimuth angle φ. The received electric field strengths E _H and E _V of the horizontally polarized wave and the vertically polarized wave at the observation point P are represented by coordinates (θ, φ) of the observation point P.
The following equation can be used to express this. However, a detailed derivation process is omitted.

The received electric field strengths E _H , E _V of the horizontal polarization and the vertical polarization obtained in this way are used as a function of the elevation angle θ and the azimuth angle φ, and the reception power 20 log E of the horizontal polarization and the vertical polarization is obtained.
Figure 4 (a) shows the result of calculating _H (dB) and 20log E _V (dB).
(B) shows a radiation distribution pattern. FIGS. 4 (a) and 4 (b) are diagrams using the same method as the Mercator projection of the world map, where the horizontal axis is the azimuth angle φ, and the vertical axis is the elevation angle θ, the horizontal polarization and the vertical polarization are shown. The absolute value of the received power is represented by a symbol shown on the right side of the figure.

FIGS. 5 (a) and 5 (b) show the reception power of the horizontal polarization and the vertical polarization actually measured using the measuring apparatus of FIG. 1 in the same manner as FIGS. 4 (a) and 4 (b). , FIG. 4 (a)
This is in good agreement with the theoretical value shown in FIG. In FIGS. 5 (a) and 5 (b), the measurement frequency (the frequency of the radio wave radiated from the DUT 1) is in the 250 MHz band.

On the other hand, FIGS. 6 (a) and 6 (b) show the same measurement results when the lightening holes 29, 30, and 31 in FIG. 1 are not formed, and FIGS. 4 (a) and 4 (b) The distribution of the received power is greatly disturbed as compared with. This is due to the effect of the non-metallic material (dielectric) used for the turntable 2, the arm 5, and the support pillar 10. Therefore, in order to perform accurate measurement, not only non-metallic materials for the rotation mechanism 3 and the power transmission mechanism 14, such as the turntable 2, the arm 5, and the support column 10, but also the lightening holes 29,3
It is desirable to form 0,31.

Incidentally, as described above, in order to obtain the radiation power and the radiation efficiency of the antenna, it is necessary to measure the radiation characteristics over the entire solid angle. It is practically difficult to perform this measurement for an antenna that is close to omni-directional because of the measurement device. In order to determine the effective radiated power by the present measuring device, it is necessary that radiation characteristics over all solid angles are accurately determined. Fig. 5 (a) (b)
Considering the measurement results shown in (1), there is a maximum difference of 1 dB between the reception power of horizontal polarization and the reception power of vertical polarization. Considering that this is a difference caused by the imperfectness of the radio wave anechoic chamber, it can be seen that according to the present apparatus, radiation characteristics over all solid angles can be obtained with sufficient accuracy.

From the comparison between the theoretical values and the experimental values of the radiation characteristics of the half-wave dipole antenna described above, the effectiveness of the structure of the mechanical part in the present apparatus will be understood. Next, the second
A specific example of the processing in steps S5 to S8 in the drawing will be described.

First, the weight function ω _H (θ,
φ) and ω _V (θ, φ) are constant, that is, a case where radio waves arrive with the same probability from all solid angle directions. This is equivalent to obtaining the radiation efficiency of the antenna if the XPD (cross polarization discrimination) is 0 dB. In this measurement, first, a sample in which a small oscillator was attached to a half-wavelength dipole antenna as the antenna 50 to be measured with a known radiation efficiency was set as the device 1 on the turntable 2 and the measurement was performed. The radiation efficiency is obtained by integrating the measurement results of the reception power of the horizontally polarized wave and the vertically polarized wave. The results are shown in FIGS. 7 (a) and 7 (b). The integration result is 0.8 dBm, the transmission power is -2.9 dBm, and the gains of the receiving antennas 32 and 33 are
From 4.9 dB, the effective emissivity of the antenna under test was -1.2 dB. This result includes the reflection loss of the antenna under test and the internal cable loss of 0.5 dB. Therefore, the radiation efficiency of the half-wave dipole antenna alone was -0.7 dB.
This measurement is an absolute measurement value of the gain, and the accuracy is an accuracy that cannot be realized by the conventional measurement method.

Further, in order to confirm whether or not the measurement change of the radiation efficiency changes depending on the installation direction of the antenna 50 to be measured, the same measurement was performed by tilting the antenna 50 on the turntable 1 by 40 ° from the horizontal. The results are shown in FIGS. 8 (a) and 8 (b). The distribution pattern of the received power is the seventh with the inclination being 0 °.
Although different from the cases of FIGS. (A) and (b), the difference between the integration results is
0.3 dB. Factors of the measurement error include a radio anechoic chamber, a mechanism part, a balun and an oscillator of a half-wave dipole antenna, and the like, but it can be said that the accuracy is higher than the radiation efficiency measurement method of a small antenna conventionally performed. .

Next, a method of obtaining the effective radiated power when the arrival angle of the radio wave is not constant will be described. Here, an on-vehicle antenna used for a mobile phone will be described as an example.

Generally, since the positional relationship between the base station and the mobile station is not constant, it is desirable that the in-vehicle antenna has omnidirectional characteristics in the horizontal direction. That is, the radio wave arrival probability is a constant probability for the azimuth angle φ.

On the other hand, it is clear that the arrival angle of the radio wave from the vertical direction, that is, the elevation angle φ, is higher in the probability of arrival in the horizontal direction than in the zenith direction. From previous studies, we found that the elevation angle θ from the horizontal was 90 ° to 60 °.
It has been reported that the angle of arrival of radio waves is concentrated in the range of ゜, 270 ゜ to 300 ゜. A description will be given using the power of sin θ as the functions ω _H (θ, φ) and ω _V (θ, φ) obtained from the arrival probability of such radio waves. Note that ω _H (θ, φ) is the horizontal polarization from each direction to the DUT 1 obtained from the radio wave arrival probability function A, the horizontal polarization probability function B _H, and the set direction probability function C of the DUT. incoming and probability weighting function obtained by _{normalizing, ω H (θ, φ)} = a · B H · C / ∫ given by _{(a · B H · C)} dθdφ. Similarly, ω _V (θ, φ) is the horizontal polarization from each direction to the DUT 1 obtained from the radio wave arrival probability function A, the vertical polarization probability function B _V, and the DUT installation direction probability function C. a weight function obtained by normalizing the arrival probability _{wave, ω V (θ, φ)} = is given by _{a · B V · C / ∫} (a · B V · C) dθdφ.

As shown in FIG. 9, the weighting functions ω _H (θ, φ) and ω _V (θ, φ) are given for the elevation angles below the horizontal = 90 ° to 180 °, 180 ° to 270 °. with sin ²⁰⁰ theta as), elevation angle theta = 0 ° to 90 ° above the horizontal, 270
For the range of {0}, sin ² θ is used. Since the radio wave arrival probability is a pair probability with respect to the azimuth angle φ as described above, ω _H (θ),
Only ω _V (θ) is shown. This is the tenth
The same applies to FIG. 11 and FIG. By performing the integration in step S7 using these weight functions, the effective radiated power can be obtained. The formula for calculating the effective radiated power is shown below.

(Wr: effective radiation power, Ge: operating gain of receiving antenna, λ: wavelength, r: distance between DUT 1 and receiving antennas 32 and 33, W _H : received power of horizontally polarized wave, W _V : vertical Polarization reception power, ω
_H : Arrival probability function of the radio wave from each direction to the DUT 1, horizontal polarization probability function, and horizontal polarization from each direction to the DUT 1 obtained from the probability function of the installation direction of the DUT Ω _V : the arrival function of radio waves from each direction to the device under test 1, the probability function of vertical polarization, and the measured function obtained from the probability function of the installation direction of the device under test Weight function that normalizes the arrival probability of vertical polarization from each direction to object 1)
The equation of the effective radiation power Wr is expressed as ω _H (θ, φ) in）,
Excluding ω _V (θ, φ), ie, ω _H (θ, φ) = 1, ω
Assuming that _V (θ, φ) = 1, the normal radiation power of the radio wave arrival probability function A, the horizontal polarization and vertical polarization probability functions B _H and B _V, and the installation direction probability function C of the device under test are not considered. It becomes an expression.
In other words, the present invention provides a weighting function ω _H (θ, φ), ω _V
By multiplying (θ, φ) by the reception power W _H , W _V of the horizontal polarization and the vertical polarization, and weighting, the radio wave arrival probability function A,
It is characterized in that the effective radiation power is determined in consideration of the probability functions B _H and B _{V of} horizontal polarization and vertical polarization and the probability function C of the installation direction of the device under test.

On the other hand, when the car travels in a suburban area, the radio waves from the base station concentrate substantially in the horizontal direction, so that a weight function concentrated in the horizontal direction as shown in FIG. 10 may be used.

In addition, when there are many slopes and the angle of the car with respect to the ground is not constant, a distribution function that is wide up and down may be considered as shown in FIG.

It should be noted that these weight functions should be determined in consideration of the XPD.

[Effects of the Invention] According to the present invention, by integrating the received power of the horizontally polarized wave and the vertically polarized wave using the weight function corresponding to the actual use condition of the device under test, especially the movement such as the on-vehicle antenna The effective radiation power, which is an evaluation index suitable for evaluating the radiation characteristics of the device under test, can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a radiation electromagnetic field measuring apparatus according to one embodiment of the present invention, FIG. 2 is a flowchart showing a measurement procedure in the embodiment, and FIG. 3 is a graph showing radiation characteristics of a half-wave dipole antenna. Diagram showing a coordinate system for deriving theoretical values,
FIG. 4 is a diagram showing the theoretical values of the radiation characteristics of the half-wave dipole antenna, FIG. 5 is a diagram showing the results of measuring the radiation characteristics of the half-wave dipole antenna using the measuring apparatus of the embodiment, and FIG. FIG. 7 shows the results of measuring the radiation characteristics of a half-wavelength dipole antenna using a device from which the lightening holes have been removed from the measuring device of the same embodiment. FIG. 7 shows a half-wavelength dipole antenna mounted horizontally on a turntable. FIG. 8 shows the results of measuring the radiation characteristics by measuring the radiation characteristics. FIG. 8 shows the results of measuring the radiation characteristics by mounting the half-wavelength dipole antenna on the turntable at an angle of 40 ° from the horizontal. Figures and No.
FIG. 11 is a diagram showing a specific example of the weight function used in the present embodiment. 1 ... DUT, 2 ... turntable, 3 ... rotating mechanism, 19 ... azimuth driving device (power source), 20 ... elevation shaft (power source), 27, 28 ... radio wave absorber, 29,30,3
1 ... Lightening holes, 32,33 ... Receiving antenna for measurement, 34 ...
Network analyzer, 35 A / D converter, 36 Computer, 39 CRT display, 50 antenna to be measured.

Claims (4)

(57) [Claims] A turntable on which an object to be measured that emits electromagnetic waves is placed; a rotation mechanism for rotating the turntable by 360 ° about two orthogonal axes; a power transmission mechanism for transmitting power to the rotation mechanism; A power source connected to the power transmission mechanism, receiving radiated power of horizontally polarized waves and vertically polarized waves from the device under test accompanying the rotation of the turntable by the rotating mechanism, Measuring means for measuring a radiated electromagnetic field over the entire solid angle, wherein the measuring means includes a probability function of the arrival of a radio wave from each direction to the device under test, a probability function of the polarization state, and a probability of the installation direction of the device under test. From the function, the arrival probability of horizontal polarization and vertical polarization from each direction to the device under test is obtained, and this is normalized to be a weight function for the reception power of horizontal polarization and vertical polarization, and these weight functions are used. Horizontal using By integrating the received power of the waves and vertically polarized waves over the entire solid angle, the radiation electromagnetic field measuring apparatus characterized by measuring the effective radiated power from the object to be measured. 2. A turntable on which an object to be measured which emits electromagnetic waves is placed, a rotating mechanism for rotating the turntable by 360 ° in two directions perpendicular to each other in an elevation direction and an azimuth direction, and power is supplied to the rotating mechanism. A power transmission mechanism for transmitting; a power source connected to the power transmission mechanism; and receiving radiated power of horizontally polarized waves and vertically polarized waves from the device under test accompanying rotation of the turntable by the rotating mechanism. Measuring means for measuring a radiated electromagnetic field over the entire solid angle of the object to be measured; (Wr: effective radiation power, Ge: operating gain of receiving antenna, λ: wavelength, r: distance between DUT and receiving antenna,
W _H : horizontal polarization reception power, W _V : vertical polarization reception power, ω _H : radio wave arrival probability function from each direction to the device under test, horizontal polarization probability function and installation direction of device under test A weighting function that normalizes the arrival probability of horizontal polarized waves from each direction to the device under test obtained from the probability function, ω _V : Arrival probability function of radio waves from each direction to the device under test and the probability of vertical polarization Measured by a weighting function that normalizes the arrival probability of vertical polarization from each direction to the DUT, obtained from the function and the probability function of the installation direction of the DUT, θ: elevation angle, φ: azimuth angle) A radiated electromagnetic field measuring device for determining effective radiated power from an object. 3. The radiation field measuring apparatus according to claim 1, wherein the turntable, the rotation mechanism, and the power transmission mechanism are formed of a non-metallic material, and the power source is covered with a radio wave absorber. . 4. The radiation field measuring apparatus according to claim 1, wherein the turntable, the rotation mechanism, and the power transmission mechanism are formed of a non-metallic material that has been lightened.