JPH1138056A - Estimating system for environmental characteristic of electromagnetic field in wireless terminal machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out sufficient characteristic estimation of a wireless terminal machine by an indoor simulation through a simple system formation. SOLUTION: Transmitting antennas 23a-23c are arranged in a sealed box 20 and a wireless terminal machine 22 being estimated object is also installed, and the environmental characteristic in electromagnetic field of a signal which is transmitted from the transmitting antennas 23a-23c and received by the terminal machine 22 is therefore reproduced. The terminal machine 22 is provided with a means for transmitting an information signal about the received signal of the strength of an electric field as a radio wave, and in addition, a receiving antenna 24 to receive a received information signal transmitted from the terminal machine 22 is provided in the sealed box 20. The received information signal of the terminal machine 22 in the sealed box 20 is inputted into an estimation control means composed of a personal computer 26 provided outside the sealed box 20, and a measurement excellent in reproduction ability can be carried out without being influenced by weather, time and surrounding environment, and moreover the characteristic estimation of the whole of the terminal machine including an antenna system can be carried out without using a cable with a space taken as an interface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for evaluating the electromagnetic field environment characteristics of a wireless terminal such as a mobile communication device with a simple configuration.

[0002]

2. Description of the Related Art In recent years, for example, mobile communication systems have been rapidly spread with the expansion of service areas of cellular phones and the like and reduction in communication costs. The importance of techniques for evaluating the characteristics of mobile phones (mobile phones) in an outdoor propagation environment is also increasing. In particular, in an environment where multiple waves arrive, such as in mobile communications in a city, intense fading occurs with the movement of the portable wireless terminal, so that static characteristic evaluation alone is not sufficient.

Conventionally, many methods for evaluating the characteristics of portable wireless terminals have been proposed, but there is an evaluation method for actually performing measurement outdoors as shown in FIG.
That is, the simple base station 1 is installed, and the measurement path 2 in the city is set.
This is a method in which a radio wave transmitted from a portable wireless terminal (device under test) that travels is received by the simple base station 1 and the characteristics of the portable wireless terminal in the environment are evaluated. However, in the method of actually performing the measurement outdoors as described above, the received electric field intensity measured by the weather, time, surrounding environment, and the like changes. Has to be evaluated statistically, which requires a great deal of time and effort.

[0004] On the other hand, a method of evaluating the characteristics of a portable radio terminal indoors has been proposed in the past, and one example is shown in FIG. That is, the fading simulator 3 and the antenna of the portable wireless terminal 4 are directly connected by the cable 5, and the fading signal output from the fading simulator 3 is received by the portable wireless terminal 4 via the cable 5, so that the portable wireless terminal 4 This is a method of evaluating the characteristics by the reception level of No. 4. However, in the method of causing the portable wireless terminal 4 to receive the fading signal via the cable 5 in this manner, it is necessary to reproduce a situation in which a wireless signal is received by an antenna in a spatially wide environment. Therefore, there is a problem that the evaluation including the entire antenna system of the portable wireless terminal 4 cannot be performed.

A method for evaluating the characteristics of the antenna of a portable wireless terminal indoors has been proposed in the past, and an example thereof is shown in FIG. That is, an antenna 7 to be evaluated is installed on a portable wireless terminal housing 6 that does not have a receiving function inside, and is installed in a shield box 8 made of an electromagnetically shielded metal wall. In the shield box 8, three transmitting antennas 9a to 9 are provided.
c and a standard signal generator 1 outside the shield box
The signal from 0 is distributed and transmitted to each of the transmitting antennas 9a to 9c with a random phase change by the phase shifters 11a to 11c. Therefore, radio waves having a phase difference are transmitted from each of the transmitting antennas 9a to 9c into the shield box 8, and the electric field strength in the shield box 8 fluctuates randomly. The environment is realized.

The antenna 7 to be evaluated is a cable 1
2 is connected to a receiver 13 outside the shield box, and the signal received by the antenna 7 is received by the receiver 13 via the cable 12. The signal received by the receiver 13 is digitally converted by the A / D converter 14 and input to the personal computer 15, and the received electric field intensity data by the antenna 7 is obtained by the arithmetic processing by the personal computer 15. The personal computer 15 also controls the phase change by the phase shifters 11a to 11c, and variously changes the electromagnetic field environment in the shield box 8 to acquire the received electric field intensity data.

However, in the method of connecting the antenna 7 and the external receiver 13 with the cable 12 as described above, the cable 12 is routed inside the shield box 8 and the reproducibility of the measurement environment is impaired. Alternatively, there is a problem that an electric field environment in the shield box 8 is disturbed by a current flowing through the cable 12 and accurate evaluation cannot be performed.

[0008]

As described above, when performing a field simulation indoors to save time and labor, it is not possible to sufficiently evaluate the characteristics of a wireless terminal. was there. The present invention has been made in view of the above-described conventional circumstances, and has as its object to provide an electromagnetic field environment characteristic evaluation system capable of performing sufficient characteristic evaluation of a wireless terminal by indoor simulation.

[0009]

In a system for evaluating the electromagnetic field environment characteristics of a wireless terminal according to the present invention, a transmitting antenna is provided in a shield box that is electromagnetically shielded, and a wireless terminal to be evaluated is mounted. The wireless terminal is installed and transmits a wireless signal from the transmitting antenna to reproduce the electromagnetic field environment characteristics of the signal received by the wireless terminal. Here, in the present invention, the wireless terminal is provided with means for transmitting an information signal relating to a received signal such as electric field strength as a radio wave, and a plurality of transmitting antennas are provided in a shield box, and A receiving antenna for receiving a reception information signal transmitted from the wireless terminal is disposed in the box.
Thereby, the reception information signal of the wireless terminal in the shield box is input to the evaluation control means provided outside the shield box via the receiving antenna.

[0010] This makes it possible to perform measurement with excellent reproducibility without being affected by weather, time, surrounding environment, and the like, and to evaluate the characteristics of the wireless terminal as a whole including the antenna system. The space can be accurately used as an interface without using a space.

Further, in the electromagnetic field environment characteristic evaluation system according to the present invention, the transmitting antennas are disposed at intervals of about one wavelength or more. As a result, the coupling between antennas between the transmitting antennas can be reduced, and an almost actual electromagnetic field environment can be reproduced as an independent signal source.

Further, in the electromagnetic field environment characteristic evaluation system according to the present invention, a rotary table is installed in a shield box, and a wireless terminal is installed on the rotary table.
Thus, it is possible to perform reception evaluation from various directions of arrival, and to perform characteristic evaluation in consideration of the antenna directivity of the wireless terminal.

Further, in the electromagnetic field environment characteristic evaluation system according to the present invention, a radio wave absorber is provided on part or all of the inner wall of the shield box. As a result, even when the space volume in the shield box is reduced, fluctuations in the antenna input impedance of the wireless terminal can be avoided, and stable measurement can be performed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electromagnetic field environment characteristic evaluation system for a portable wireless terminal according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the entire configuration of the electromagnetic field environment characteristic evaluation system according to the present embodiment in a state where the shield box 20 is seen through.

The shield box 20 is a rectangular parallelepiped box made of metal, and the internal space of the shield box 20 is electromagnetically shielded from the outside. In this embodiment, since the measurement frequency is 800 MHz, the width W of the shield box 20 is 1670 mm, the height H is 1330 mm,
The depth L is set to 2000 mm. The size of the shield box 20 is not particularly limited. However, if the volume of the internal space of the shield box 20 is increased, a favorable evaluation environment is maintained even when a relatively large portable wireless terminal is evaluated. be able to.

Incidentally, in order to maintain a favorable evaluation environment,
The portable wireless terminal to be evaluated preferably has a volume of about 2% or less of the internal space volume of the shield box. Also,
In order to further reduce the size of the shield box 20, the whole or a part of the inner wall surface of the shield box may be
1 and avoiding a change in the antenna input impedance of the portable wireless terminal (evaluation target) 22 installed inside the shield box 20, a favorable evaluation environment can be maintained. In the present embodiment, only the inner wall surface serving as the back surface of the portable wireless terminal 22 is covered with the radio wave absorber 21.

The portable radio terminal 2 of the shield box 20
The three transmitting antennas 23a-
23c, these transmitting antennas 23a
23c face the inner space of the shield box 20. In addition, a receiving antenna 24 is provided on the same wall surface of the shield box 20, and the tip of the receiving antenna 24 also faces the inside space of the shield box 20. Here, each transmission antenna 23a-
23c are provided at an interval from each other, and this interval is set to about one wavelength or more of a radio signal used for measurement to suppress coupling between antennas between the transmitting antennas 23a to 23c, and to provide an independent signal source. I am trying to be.

The types of the transmitting antennas 23a to 23c and the receiving antenna 24 are not particularly limited, and a linear antenna such as a standard dipole antenna, a planar antenna or a plate antenna printed on a printed circuit board or the like may be used. Can be. In addition, these antennas may be used by being tilted with respect to a wall surface (tilt), whereby coupling between antennas and cross polarization discrimination (XPD) can be made variable. In this embodiment, all the antennas 23a to 23a
Although 3c and 24 are installed on the same wall surface, the installation positions of these antennas are not particularly limited. For example, as shown in FIG. 2, the transmitting antennas 23a to 23c may be installed on different wall surfaces. Good. The receiving antenna 24 is preferably installed at a position where radio waves from the portable wireless terminal 22 can be easily received. In addition, each transmitting antenna 2
It is preferable to avoid installing the antennas 3a to 23c and the receiving antenna 24 in a corner surrounded by a wall surface.

The number of transmitting antennas is required to be two or more, and there is no problem in a weak electric field sensitivity test or the like. However, there is a close relationship with the correlation coefficient in the electric field intensity inside the shield box 20. In order to make the correlation coefficient close to the low correlation coefficient as in the outdoor environment, the number of transmitting antennas is required to be three or more as is known (IEICE Technical Report, AP94).
-1, 1994, "Basic study of field simulator"). Note that four or more transmitting antennas may be provided. As the number of transmitting antennas increases, the correlation coefficient further decreases, and favorable evaluation can be performed. For reference, FIG. 3 shows a correlation coefficient histogram at the center of the shield box 20 when three transmitting antennas are provided, and the average value of the correlation coefficients is as low as about 0.2. This is a value that has no practical problem.

Here, the portable radio terminal 22 installed in the shield box 20 to be evaluated includes an antenna 22a, a receiving circuit for receiving a radio signal via the antenna 22a, and an antenna 22a, similarly to a normal portable telephone. In particular, the portable wireless terminal 22 detects information related to a received signal such as a received electric field strength and bit information, and transmits the information signal. A circuit for transmitting radio waves from the antenna 22a is provided. As a result, the information regarding the received signal is wirelessly transmitted from the portable wireless terminal 22 to the receiving antenna 24 as shown by a broken arrow in FIG. Is output.

Outside the shield box 20, an evaluation control means for evaluating the portable radio terminal 22 and performing control for this evaluation test is provided. The evaluation control means includes a simple base station 25 having a receiving and transmitting function connected to a receiving antenna 24, and a personal station for analyzing a signal received by the simple base station 25 and outputting a random phase shift control voltage. A computer 26, a divider 27 for dividing a signal transmitted from the simple base station 25 into three signals, three phase shifters 28a to 28c for controlling phases of signals output from the divider 27, and a personal computer The D / A converter 29 which converts the phase shift control voltage from the analog-to-digital converter 26 into analog signals and inputs the analog signals to the respective phase shift controllers 28a to 28c, and amplifies the signals output from the respective phase shifters 28a to 28c to transmit the respective signals. Amplifiers 30a to 30c for transmitting from the trust antennas 23a to 23c.

According to the electromagnetic field environment characteristic evaluation system configured as described above, the characteristic evaluation of the portable wireless terminal 22 installed in the shield box 20 is performed as follows. First, a signal transmitted from the simple base station 25 is distributed by the distributor 27 and input to each of the phase shifters 28a to 28c, and based on a phase shift control voltage from the personal computer 26,
The phase of each signal is changed by each of the phase shifters 28a to 28c. These phase-controlled signals are amplified by the amplifiers 30a to 30c, respectively, and transmitted from the transmitting antennas 23a to 23c into the shield box 20. The amplification degree of each of the amplifiers 30a to 30c is set so that the electric field strength measuring circuit of the receiver of the portable wireless terminal 22 that receives a signal does not saturate and the received electric field strength (RSSI: Received Signal Strength Indicator) as described later. )
The level is set to maximize the dynamic range.

As a result, each of the transmitting antennas 23a to 23
c, signals having a random phase difference from each other are transmitted into the shield box 20, these signals are reflected on the inner wall surface of the shield box 20, and signals incident from various directions are received by the portable wireless terminal 22. Is done. The portable wireless terminal 22 transmits an information signal relating to a predetermined reception signal such as electric field strength and bit information as a radio wave, and the reception information signal is received by the simple base station 25 via the reception antenna 24. The received information signal is input to the personal computer 26, where the received electric field strength and its fluctuation are analyzed, and the shield box 20 is analyzed.
The characteristics of the portable wireless terminal 22 under the fading environment formed therein are evaluated. Therefore, by randomly controlling the phase of the transmission signal by the personal computer 25, the characteristics of the portable wireless terminal 22 under various fading environments can be evaluated.

More specifically, the transmitting antennas 23a to 23a
When a signal having a random phase difference is transmitted from 23c, the electric field of the spatial field in the shield box 20 is disturbed, and a random electric field intensity fluctuation occurs. As a result, at many observation points in the shield box 20, the cumulative probability distribution with respect to the electric field intensity exhibits a distribution close to the Rayleigh distribution as shown by B in FIG. 4, and at other observation points, A in FIG.
A rice distribution is exhibited as shown by. Note that the horizontal axis in FIG. 4 is normalized by the median value of the received electric field strength, and the vertical axis represents the cumulative probability of being equal to or lower than the level of the median value.

FIG. 5 shows the variation of the electric field strength at the observation points showing the distribution B, and the horizontal axis represents the number of switchings (ie, the number of samplings) for changing the control voltage of the phase shifter.
Is represented. In the present embodiment, the switching frequency of the phase shifter is set to 40 Hz, and by changing the switching frequency of the phase shifters 28a to 28c, an environment having a desired fading pitch is formed in the shield box 20, and the portable wireless terminal An evaluation of the characteristics of the machine 22 can be performed. Therefore, by using the electromagnetic field environment characteristic evaluation system, accurate and highly reproducible characteristic evaluation can be easily performed indoors without being affected by the weather, time, and surrounding environment.

Here, in the above-described embodiment, the portable radio terminal 22 to be evaluated is statically installed in the shield box 20. However, as shown in FIG. The terminal 22 may be installed to perform an evaluation test. In the example shown in FIG. 6, the cylindrical member 32 made of a foam material that does not affect the electric field of the environment
Is installed on the rotary table 31, and the portable wireless terminal 22 is installed thereon. By performing the evaluation test while the rotary table 31 is driven to rotate, the wireless signals arriving from various directions can be received by the portable wireless terminal 22, and the antenna directivity of the portable wireless terminal 22 can be reduced. An evaluation test that takes into consideration can be performed. In the above-described embodiment, the portable wireless terminal (mobile phone) is evaluated, but the present invention can be widely applied to general evaluation tests of wireless terminals.

In the above system, a function of transmitting an information signal relating to a received signal as an optical signal or a function of transmitting an audio signal such as a tone signal to the wireless terminal 22 is provided, and the receiving antenna 24 receives the optical signal. If the simple base station 25 is provided with a function of outputting a signal from the optical sensor or the microphone to the personal computer 26, the reception information signal from the wireless terminal 22 is provided. Can be obtained in a signal format different from that of radio waves. When a signal format different from a radio wave is used as described above, it is not necessary to consider the coupling between the transmitting antenna and the receiving antenna, so that the degree of freedom in design is increased and the signal transmitted to the wireless terminal and the It is not necessary to consider the interference with the signal received from the terminal, so that a more accurate evaluation test can be performed.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The result of a characteristic evaluation test of a portable radio terminal performed by the system having the configuration shown in FIG. 1 will be described below.

In this evaluation test, the lower limit frequency of the measurement was 800 M
Hz band, the size of the shield box 20 was set to width W = 1650 mm, height H = 1330 mm, and depth L =
It was 2000 mm. The spatial field sizes inside the shield box at the measurement frequency of 820 MHz are 4.51λ, 3.64λ, and 5.47λ, respectively. The outer walls surrounding the measurement space field are all metal walls, and the radio wave absorber 21 is laid only on the wall surface from the wave source (the transmitting antennas 23a to 23c) to the portable wireless terminal 22 to be evaluated.

Here, the reason why the radio wave absorber 21 is provided is to prevent deterioration of the characteristics of the portable wireless terminal 22 due to a change in the input impedance of the portable wireless terminal 22. A simple base station (signaling tester MD162) controlled by a personal computer 26 uses three offset standard dipole antennas as wave sources.
0B) The transmission signal distributed from 25 is randomly changed by independent phase shifters 28a to 28c, and a fading environment is realized by disturbing the electric field in the measurement space field.

The portable radio terminal 22 is a shield box 2
0, the actual moving speed (mobile station speed) of the portable radio terminal 22 is fixed at an arbitrary position inside the phase shifters 28a-28.
Control was performed at a switching interval for controlling c. As a result, the fading pitch can be changed, and various propagation environments can be realized. Furthermore, in this system, the signal level received by the portable wireless terminal 22 is converted into an IF to convert the signal level into an IF without connecting a cable or the like to the portable wireless terminal 22 in order to minimize the influence of the measurement conditions.
The SSI output voltage signal is transmitted from the portable wireless terminal 22 again. As a result, the reception signal can be received by the reception antenna 24 and the reception signal level of the portable wireless terminal 22 can be obtained.

An evaluation test is performed with the hardware configuration as described above, and the electric field intensity distribution in the shield box 20 is calculated by the following analysis, and the cumulative probability distribution and the correlation coefficient in the measurement area are examined. And the cross polarization discrimination (XPD) was also clarified.

The analysis of the shield box 20 requires that the shape is a rectangular parallelepiped, that diffraction waves and transmitted waves are not taken into account, and that the calculation time is significantly longer than a method of numerically calculating the Maxwell equation such as the FDTD method. Therefore, ray tracing by the mirror image point method (image method) was used. The mirror point method will be briefly described.

The radio wave radiated from the transmission point is
Repeat the geometric reflection on the inner wall and receive
Reach the confidence point. Superimpose all the radio waves that arrived
To calculate the electric field strength. At this time, at the reflection point,
Assuming that the launch angles are equal, as shown in FIG.
By considering the transmission point, the direct wave reaching the reception point
All of the reflected waves can be considered as straight lines. But
Therefore, the distance from the mirror image transmission point to the reception point is
The electric field strength is the propagation distance of the
Decreases proportionately. From the above, the electric field strength at the receiving point
E can be expressed by equation (1). Where E₀Is the electric field at the transmission point
Intensity, k is the propagation constant, R _iIs the distance from each transmission point, and n is
This is the number of all transmission points. In FIG. 10, the intersection at the boundary surface is shown.
A two-dimensional model in which the number of reflections, ie, the number of reflections, is considered to be one
However, the calculation considers three-dimensional reflection a plurality of times.

[0035]

(Equation 1)

Next, regarding the analysis model shown in FIG.
The distribution of the electric field intensity in the shield box 20 was analyzed. The radio wave absorber 21 is provided on one surface of the analysis space, and the reflection coefficient greatly differs depending on the angle of incidence on the reflection surface, the polarization, and the material. The incident angle of the TE wave and the TM wave in the single-layered electromagnetic wave absorber used is θ, the complex relative permittivity of the electric absorber,
The complex reflection coefficient of Fresnel, where the complex magnetic permeability is ε _r and μ _r and the thickness is D, can be expressed by equations (2) to (5).

[0037]

(Equation 2)

[0038]

(Equation 3)

[0039]

(Equation 4)

[0040]

(Equation 5)

The electric field strength at the receiving point must be calculated by decomposing the incident wave into each polarization component in consideration of the reflection coefficient at each reflection point. Therefore, as shown in FIG. 12, a plane including the transmission point T, the reception point R, and the mirror image point T ′ is defined as an entrance plane with respect to a reflection plane having a normal vector n, and the normal vector of the entrance plane is defined as Let p. Mirror point T 'to receiving point R
Is a direction vector to r, and an electric field vector at a mirror image point T ′ is e. Since the electric field vector e at the mirror image point T 'needs to consider only a component perpendicular to the direction vector r, the vector e
Considering only the component parallel to the plane of incidence (TM reflection for the reflection plane) and the component perpendicular to the plane of incidence for vector e (TE reflection for the reflection plane), The electric field strength can be expressed by equation (6).

[0042]

(Equation 6)

[0043]

[Table 1]

Using the analysis parameters shown in Table 1, the expression (6) is calculated to obtain the electric field intensity distribution of the vertically polarized wave and the electric field intensity distribution of the horizontally polarized wave, and the analysis is as follows. In these distributions, all sources are vertical and equi-amplitude in-phase fed. However, the analyzed cross section (observation cross section) does not include the vicinity of the wave source, the metal wall surface, and the vicinity within one wavelength from the absorber as the analysis range. This is because the reflecting surface is also considered to be a secondary wave source and is not desirable as a calculation area.

Next, the cross polarization discrimination (XPD) in the observation section is examined. In the electric field strength distribution of the vertical polarization and the electric field strength distribution of the horizontal polarization obtained by calculating the equation (6), the difference between the normalized levels of the respective polarization components when all the wave sources are vertical is 11.6 dB. It is. On the other hand, when all the wave sources are horizontal, that is, when the transmitting antenna serving as the wave source is tilted by 90 degrees in the XY cross section, the horizontal polarization component is slightly stronger, and the XPD is −0.0.
7 dB. Therefore, it can be seen that the XPD of the entire field can be varied within a range of 12.3 dB at the maximum.
In the vertical polarization component, by gradually tilting the transmitting antenna from the vertical, the electric field strength level at a location distant from the wave source becomes relatively strong, and the electric field strength level of the entire field also increases for the horizontal polarization component. Become.

Next, in order to realize fading which occurs in an actual moving environment, the phases of all the wave sources were changed at random to change the electric field strength in the field. When the fading distribution on the observation cross section (ZX plane at Y = 1.82λ) was obtained, it was found that fading according to the Rayleigh distribution and the Rice distribution occurred at many measurement points in the field. At this time,
In any distribution, the measurable range is 0.5 at the maximum.
It is about λ × 0.5λ. In the observation cross section, there are many areas having a Rayleigh distribution in a range where the distance from the wall where the wave source is located in the Z direction which is the direction of the portable wireless terminal 22 is within 2.5λ. There were many areas showing rice distribution in the direction of the distant absorber. This is because the electric field intensity level reflected from the absorber 21 is much smaller than the electric field level reflected from the other wall surface.
It is considered that the electric field strength level of the direct wave becomes dominant in a place close to 1.

Next, when the cumulative probability distribution of the measurement points serving as the Rayleigh distribution and the Rice distribution was obtained, the distribution shown in FIG. 4 was obtained. The distribution B in FIG.
1%, normalized received electric field strength level is about -28d
The measurement up to B is in very good agreement with the Rayleigh distribution, and it can be determined that this measurement point is very close to the actual outdoor travel propagation path. The electric field intensity fluctuation at this time is as shown in FIG. 5, and the fading speed is set to the phase shifters 28a to 28.
Since this depends on the switching cycle for controlling c, this cycle time can be controlled to match the desired moving speed of the mobile station. When the switching cycle is halved, the fading pitch is also halved. In this case, the median value of the short section is -7.54 dB. Therefore, it was found that by controlling the phase shifter, fading occurred and the speed of the mobile station could also be controlled.

Although the study on the plane has been clarified from the above, the size of the measurement space must be accurately grasped because the portable radio terminal 22 is actually installed in the space. For the fading distribution obtained above, the Z direction is 1.5λ
As a result of examining the spatial spread (Rayleigh zone) in the range from to 2.5λ, the observed cross section (Y = 1.82)
There were three cross-sections A, B and C for those containing λ).
A was 0.36λ in both the positive and negative directions of the Y axis, B was the widest space as a space, 0.55λ in the positive direction, 0.73λ in the negative direction, and C was 0.18λ in the positive direction and 0.36λ in the negative direction. Table 2 summarizes these. Both A and B are spaces enough to place the portable wireless terminal 22, and the frequency is 8
At 20MHz, A is about 5,000cc, B is about 6,60cc
There is a measurable area of 0 cc. Also, the XPD of the widest space B is 40 dB from about -10 dB to 30 dB.
It changed at random within the range of B, and the median at this time was found to be 10.69 dB.

[0049]

[Table 2]

What is important in evaluating each characteristic in the shield box 20 is that each measurement point shows a low correlation. If the data of any two points is X _i and Y _i , the correlation coefficient R can be obtained by equation (7). Where N is the number of data, X
(Over bar) and Y (over bar) are X,
The average value of Y, S _X and S _Y are the standard deviations of X and Y, respectively.

[0051]

(Equation 7)

The correlation coefficient R is in the range of -1 ≦ R ≦ 1,
When the relationship that X is larger and Y is larger is stronger, the value approaches 1, and conversely, when the relationship that X is larger and Y is smaller is stronger, the value approaches -1. In order to reproduce the outdoor environment, it is an essential condition that the correlation is low as in the outdoor environment. The correlation coefficients of the two spaces A and B, which are the Rayleigh zones in the shield box 20, are as shown in FIGS. 13A and 13B, respectively. It can be seen that variation and correlation are low. In particular, it has been found that the wide space A has a low correlation and is optimal for performing characteristic evaluation.

According to the above embodiment, the transmitting antenna 2
By randomly changing the phase of the signal transmitted from 3a to 23c, it was confirmed that the field electric field intensity in the shield box 20 was disturbed and the Rayleigh distribution and the Rice distribution could be reproduced. Also, the fading pitch is
This can be realized by changing the switching cycle for controlling the phase shifters 28a to 28c. Also, the mobile wireless terminal 2 is actually
Since the space for evaluating No. 2 was sufficiently large and the correlation coefficient in the measurement space was low, it was confirmed that the conditions were sufficient for evaluating the characteristics in a mobile communication environment.

[0054]

As described above, according to the present invention,
A system capable of performing field simulation indoors can be realized with a simple configuration, and it is not necessary to connect a cable or the like to the object to be evaluated, and sufficient characteristic evaluation of the wireless terminal can be accurately performed. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electromagnetic field environment characteristic evaluation system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating another arrangement example of a transmitting antenna.

FIG. 3 is a graph showing an example of a correlation coefficient histogram.

FIG. 4 is a graph showing a cumulative probability distribution in an electric field intensity.

FIG. 5 is a graph showing a change in electric field intensity.

FIG. 6 is a configuration diagram of an electromagnetic field environment characteristic evaluation system according to another embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a conventional outdoor evaluation method.

FIG. 8 is a diagram illustrating an example of a conventional indoor evaluation method.

FIG. 9 is a diagram illustrating another example of a conventional indoor evaluation method.

FIG. 10 is a diagram illustrating a mirror image point method.

FIG. 11 is a diagram illustrating an analysis model.

FIG. 12 is a diagram illustrating component decomposition on an incident surface.

FIG. 13 is a graph showing a correlation coefficient histogram.

[Explanation of symbols]

20: shield box, 21: radio wave absorber, 22: portable wireless terminal, 22a: antenna, 23a to 23c: transmitting antenna, 24 ...
· Receiving antenna, 25 ··· Simple base station, 26 · · ·
・ Personal computer, 27 ・ ・ ・ Distributor, 28
a to 28c: phase shifter, 31: rotary table,

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Arai 615-11 Imajuku Higashicho, Asahi-ku, Yokohama-shi, Kanagawa

Claims (4)

[Claims] 1. A signal that a transmitting antenna is arranged in a shielded box that is electromagnetically shielded, a wireless terminal to be evaluated is installed, and a wireless signal is transmitted from the transmitting antenna and received by the wireless terminal. An electromagnetic field environment characteristic evaluation system that reproduces the electromagnetic field environment characteristics of the above, wherein a plurality of transmitting antennas are arranged in a shield box, and a means for transmitting an information signal regarding a received signal to a wireless terminal as a radio wave. Further, a receiving antenna for receiving a received information signal transmitted from the wireless terminal is disposed in the shield box, and evaluation control means provided outside the shield box is connected to the wireless terminal via the receiving antenna. An electromagnetic field environment characteristic evaluation system for a wireless terminal, which receives a reception information signal of the terminal. 2. The wireless terminal according to claim 1, wherein the transmitting antennas are spaced apart from each other by at least about one wavelength. EM environment evaluation system for machines. 3. The system for evaluating electromagnetic field environment characteristics of a wireless terminal according to claim 1, wherein a rotary table is installed in the shield box, and the wireless terminal is installed on the rotary table. Characteristic electromagnetic field environment characteristic evaluation system for wireless terminals. 4. The electromagnetic field environment characteristic evaluation system for a wireless terminal according to claim 1, wherein a radio wave absorber is provided on part or all of the inner wall of the shield box. Characteristic electromagnetic field environment characteristic evaluation system for wireless terminals.