JP5476532B2 - Propagation environment control type radio wave reflection box - Google Patents

Description

  The present invention relates to a propagation environment control type radio wave reflection box that can be suitably used to implement an OTA (Over The Air) measurement method that is one of methods for evaluating the performance of a mobile terminal for mobile communication. .

In the field of mobile communications, technologies for large capacity and high speed are being promoted, and in particular, MIMO (Multi Input Multi Output) technology using multiple antennas for transmitting and receiving antennas has begun to be put into practical use. ing.
In order to evaluate a mobile terminal equipped with a MIMO antenna, testing in a real environment is desirable, but from the viewpoint of reproducibility and efficiency, there is an OTA measurement method that creates a radio wave environment equivalent to the real environment around the mobile terminal. Attention has been paid.
Several proposals have been made for OTA measurement methods. Among them, the method using the radio wave reflection box described in Patent Document 1 and the like can generate a delayed wave by using multiple reflections in the radio wave reflection box, so that a Rayleigh fading environment can be easily obtained. In addition, a great advantage is obtained that the device itself can be constructed at low cost.

JP-A-10-26645

However, in the conventional method, it is not easy to change the propagation environment parameter in the reflection box, and therefore it is difficult to control the cross polarization power ratio and the incoming wave distribution around the receiving antenna.
That is, in the radio wave reflection box, a delayed wave is generated by repeating the reflection of the radio wave inside. For this reason, there are almost equal amounts of polarization components around the receiving antenna, and radio waves come from all directions, so the cross-polarization power ratio and the incoming wave distribution must be controlled. It becomes difficult.

  Therefore, an object of the present invention is to provide a propagation environment control type radio wave reflection box capable of controlling the cross polarization power ratio and the incoming wave distribution.

In order to solve the above-described problems, the present invention provides a first box formed of a material having a property of reflecting radio waves, and a material disposed in the first box and having a property of reflecting radio waves. Provided on the inner surface of the second box, which is formed in a columnar shape and has a plurality of openings arranged on the peripheral surface and having a size capable of passing radio waves in the used frequency band. A radio wave absorber, a transmitting antenna that is disposed between the first and second boxes and radiates radio waves in the use frequency band, and a polarization in a specific direction of the radio waves at the opening of the second box A passage amount restriction means for restricting the passage amount of the component, a displacement means for changing the receiving position in the second box body, and a form that can be attached to and detached from the outer peripheral surface of the second box body and arranged in the circumferential direction in polymerization and a plurality of dielectric substrates which are arranged, wherein the The excessive amount limiting means is a reflective element that reflects the polarization component in the specific direction, and is formed of a metal foil adhered to the dielectric substrate, and the specific amount in the corresponding opening of the second box providing propagation environment controlled wave reflector box that limits the passage of the direction of polarization components.

Before SL first box is, for example, formed to have a rectangular parallelepiped shape, the second box is formed to have, for example, polygonal prism shape.

The second box is arranged in such a manner that the central axis is vertical, and the passing amount limiting means is configured to set a horizontal direction radio wave passing angle range centering on the central axis.

The polarization component in the specific direction is a polarization component in the horizontal direction or the vertical direction.

  According to the present invention, while maintaining the advantages of a radio wave reflection box that can be constructed inexpensively and easily, it is possible to control the cross polarization power ratio and the incoming wave distribution that were impossible with a conventional reflection box.

It is a see-through | perspective perspective view which shows one Embodiment of the propagation environment control type | mold electromagnetic wave reflection box which concerns on this invention. It is a front view which shows the structure of the side plate of an internal box. It is an enlarged view of the dotted line frame part of FIG. It is the XX sectional view taken on the line of FIG. It is a perspective view which shows the state which attached the quarter wavelength type electromagnetic wave absorber and the dielectric substrate to the side plate. It is a schematic plan view which shows the positional relationship of a transmission antenna and an internal box. It is the graph which illustrated the change of the received power median value according to the change of reflective element length about each of vertical and horizontal polarization. It is a schematic plan view which shows a horizontal direction electromagnetic wave passage angle range. It is the graph which illustrated the spatial correlation characteristic about each electric wave passage angle range.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a transparent perspective view showing an embodiment of a propagation environment control type radio wave reflection box according to the present invention used for OTA (Over The Air) measurement. The radio wave reflection box includes an outer box 1, an inner box 3 disposed in the outer box 1, and a transmission antenna 5.

  The outer box 1 is formed in a rectangular parallelepiped shape using an aluminum panel which is a radio wave reflector, and the length is 4 m, and the width and height are 2 m in consideration of human beings inside. Is set. Similarly, the inner box 3 is formed in a regular octagonal column shape using an aluminum panel that is a radio wave reflector, and is sized so as to be inscribed in a cylinder having a diameter of 1 m and a height of 1 m. The sizes of the outer box 1 and the inner box 3 are not limited to the above.

The inner box 3 is composed of a regular octagonal upper plate 9 and lower plate 11, and eight side plates 13 provided between the upper plate 9 and the lower plate 11. As shown in FIG. 2, each side plate 13 is formed with a large number of openings 15 for passing radio waves arranged vertically and horizontally at predetermined intervals.
In the present embodiment, the structure of the opening 15 is determined so that radio waves in the 5 GHz band, which is the use frequency band, pass. That is, as shown in FIG. 3 which is an enlarged view of the dotted line frame portion A in FIG. 2, the opening 15 in the present embodiment has a square shape with a side length of 30 mm, and an interval of 15 mm between the adjacent openings 15. Are arranged in such a way that they are formed.

Further, as shown in FIGS. 4 and 5 which are sectional views taken along the line XX of FIG. 3, a radio wave absorber 17 is attached to the inner surface of the side plate 13.
In the present embodiment, a ¼ wavelength type radio wave absorber is used as the radio wave absorber 17. This quarter-wave type wave absorber includes a spacer 19 made of a foam material attached to the inner surface of the side plate 13 and a resistance film 21 attached to the back surface of the spacer 19.
The resistive film 21 is spaced from the metal plate by ¼λ (λ is the wavelength of the center frequency of the used frequency band) and exhibits a skin resistance equal to the characteristic impedance of free space. Since the configuration and operation of this ¼ wavelength type electromagnetic wave absorber are well known, detailed description thereof will be omitted.

As shown in FIG. 5, the quarter wavelength electromagnetic wave absorber 17 is uniformly attached to the inner surface of the side plate 13. In this case, the radio wave absorber 17 functions as an absorber in a portion where the metal surface exists, but does not function as a radio wave absorber in the portion of the opening 15 where the metal surface does not exist.
In addition, the electromagnetic wave absorber is stuck also to the inner surface of the upper board 9 and the lower board 11 (refer FIG. 1) of the internal box 3 in which the opening 15 does not exist. This radio wave absorber functions as an absorber because the upper plate 9 and the lower plate 11 do not have openings.

The transmission antenna 5 is installed in a space formed by the inner surface of the outer box 1 and the outer surface of the inner box 3. As shown in FIG. 6, in the present embodiment, the installation point of the transmission antenna 5 is included in the vertical plane 25 including the longitudinal center axis of the outer box 1 together with the vertical center axis of the inner box 3.
A slide rail 29 is provided in the inner box 3. The slide rail 29 is disposed along a direction perpendicular to the vertical surface 25 (the width direction of the outer box 1 shown in FIG. 1), and the receiving antenna 7 is positioned at the vertical center axis of the inner box 3. Has a function of moving the receiving antenna 7 along the same direction.

As shown in FIGS. 5 and 6, on the outer surface of each side plate 13 of the inner box 3, a dielectric substrate 23 having the same dimensions as the side plate 13 is superposed and detachably arranged. As shown in FIGS. 3 to 5, the dielectric substrate 23 is formed with an array of reflective elements 27 made of rectangular metal foil (for example, copper foil) having a narrow width (for example, 3 mm). The reflective element 27 can be formed using a technique for forming a so-called printed wiring pattern.
The reflecting element 27 is provided for the purpose of limiting the amount of incoming radio waves passing through the opening 15 of the vertically polarized component, and is directed vertically in front of the center of each opening 15.

In FIG. 6, the radio wave radiated from the transmitting antenna 5 is directly or after being reflected on the inner surface of the outer box 1, the openings 15 shown in FIG. 3 provided in the side plates 13 of the inner box 3. To reach. At this time, the amount of passage of the vertically polarized wave component of the radio wave through the opening 15 changes according to the length a of the reflecting element 27. As the transmission antenna 5, for example, a dipole antenna that radiates 45-degree polarized waves is used.
A part of the radio wave that has passed through the opening 15 is reflected by the skin resistance film 21 of the quarter-wave absorber 17 shown in FIG. To reach. Most of the radio waves not absorbed by the receiving antenna 7 are absorbed by the radio wave absorber 17 attached to the inner surface of the inner box 3. Therefore, the reflection of radio waves is suppressed in the inner box 3.

In FIG. 6, the eight dielectric substrates 23 each have a reflective element 27 having a common length. Therefore, the reflecting elements 27 perform the same amount of passing amount limiting action on the vertically polarized component that has reached the opening 15 of the corresponding side plate 13.
Therefore, if the eight dielectric substrates 23 used so far are replaced with another eight dielectric substrates 23 having different lengths of the reflecting elements 27, that is, the respective openings 15 of the inner box 3 are related. If the length of the reflecting element 27 is changed, the above-mentioned passing amount limiting action is changed. This means that the reception level of the vertical polarization component at the reception antenna 7 changes.

FIG. 7 exemplifies the change characteristic of the median received power with respect to vertical polarization (V polarization) and horizontal polarization (H polarization) when the length of the reflective element 27 is changed as described above. Is.
Here, the median received power will be described. The measurement frequency range is 5.0 to 5.2 GHz, and the receiving antenna 7 (in this case, a diball antenna is used) for each frequency of 1601 points in this frequency range is 2 mm in the direction indicated by the arrow in FIG. When the step is slid within the range of 0 to 200 mm, a total of 1601 × 101 received power can be obtained from the output of the receiving antenna 7. The median means the median value of the 1601 × 101 received power. Each characteristic shown in FIG. 7 shows the change in the median value according to the length of the reflective element 27 for the vertical polarization component and the horizontal polarization component.
The receiving antenna 7 is slid from the vertical central axis portion of the inner box 3 along the slide rail shown in FIG. 6 by an appropriate actuator. The receiving antenna 7 has dipole elements oriented vertically and horizontally when receiving vertically polarized waves and horizontally polarized waves, respectively.

As apparent from FIG. 7, if began to increase the length a of the reflective elements 27, the ones received power median vertical polarization to decrease received power median horizontal polarization is hardly changed. This indicates that the cross polarization power ratio can be controlled by the length of the reflective element 27.
Therefore, in the present embodiment, by changing the dielectric substrate 23 having the reflective elements 27 having different lengths, a desired difference is provided between the power of the vertically polarized wave and the horizontally polarized wave.
As a result, according to the present embodiment, a mobile terminal (not shown) is arranged at the position of the receiving antenna 7 to evaluate the reception operation of the mobile terminal in a radio wave environment having different cross polarization power ratios. It becomes possible.

Next, an embodiment in the case of controlling the incoming wave distribution will be described.
In FIG. 8 corresponding to FIG. 6, 2σ is a horizontal radio wave passing angle range centering on the vertical central axis of the inner box 3, and the vertical plane 25 bisects this angular range 2σ.
In the example of FIG. 8, the angle range 2σ is 90 °. In this case, the length a of the reflecting element 27 of the dielectric substrate 23 related to the front side plate 13 facing the transmitting antenna 5 is zero. In other words, the reflective element 27 is not formed on the dielectric substrate 23.

On the other hand, in each dielectric substrate 23 related to the side plate 13 adjacent to both sides of the front side plate 13, the reflective element 27 is formed only in a half region on the side away from the dielectric substrate 23 related to the front side plate 13, In addition, in the dielectric substrate 23 related to the remaining side plate 13, a reflective element 27 is formed over the entire area.
Therefore, the angle range 2σ defines a radio wave passing range that is not limited by the amount of passage by the reflecting element 27.
In the present embodiment, the width and length of the reflective element 27 are set to 3 mm and 22.5 mm, respectively. Therefore, in the opening 15 in which the reflecting element 27 is interposed, the passing amount of the vertically polarized component is greatly reduced (20 dB or more).

The horizontal radio wave passing angle range 2σ can be set to an arbitrary size by preparing in advance the dielectric substrate 23 in which the reflective element 27 is formed and selectively combining them.
FIG. 9 shows the spatial correlation characteristics when the radio wave passing angle range 2σ is 45 °, 90 °, 135 °, and 360 °, respectively.
This spatial correlation characteristic is obtained by obtaining a correlation with the received power measurement value at each position of the reception antenna 7 with reference to the received power measurement value at the center position of the inner box 3. That is, as in the case of obtaining the data of FIG. 7, the receiving antenna 7 is set to 0 to 200 mm in 2 mm steps in the direction indicated by the arrows in FIG. 6 for each frequency of 1601 points in the frequency range of 5.0 to 5.2 GHz. A total of 1601 × 101 received power is measured while sliding the range, and the calculation is based on the measurement result.

As is apparent from FIG. 9, as the radio wave passing angle range 2σ is narrowed, the spatial correlation main lobe widens, which indicates that the arrival angle distribution can be controlled.
Therefore, in the present embodiment, the radio wave passing angle range 2σ is set to an arbitrary size by selectively combining the dielectric substrates 23 in which the reflective elements 27 are formed in different ways.
As a result, according to the present embodiment, by placing a mobile terminal (not shown) at the position of the receiving antenna 7, it is possible to evaluate the reception operation of the mobile terminal in a radio wave environment with different arrival angle distributions. It becomes possible.

The present invention is not limited to the above-described embodiment, and may include various modifications as described below, for example.
a. In each of the above-described embodiments, the amount of passage of the vertically polarized wave is limited by the reflecting element 27, but the amount of passage of the horizontally polarized wave can be limited by the reflecting element 27. In this case, the reflecting element 27 shown in FIGS. 5 and 6 is formed so as to face horizontally.
b. Internal box body 3 are not regular octagonal columnar positive polygonal pillar shape, or may be formed in a cylindrical shape.
c. The radio wave passing angle range 2σ shown in FIG. 6 may be formed so that the angle center is directed in a direction different from the direction of the transmitting antenna.
d. The slide rail 29 can have a function of sliding the receiving antenna 7 and the portable terminal in an arbitrary direction (including a three-dimensional direction) different from the direction of FIG.
e. In FIG. 6, a region indicated by a thick line on the dielectric substrate 23 (a region where the reflective element 27 exists) may be covered with a uniform metal foil.
f. The radio wave reflection box according to the above embodiment is applied to a frequency of 5 GHz band, but can be applied to other frequency bands. In that case, the size and arrangement interval of the openings 15 shown in FIG. The size of 27 is set so as to be compatible with the other frequency bands.

  Since the propagation environment control type radio wave reflection box according to the present invention can control the cross polarization power ratio and the arrival wave distribution, it is useful as an OTA evaluation apparatus for a mobile terminal for mobile communication, and is simple and inexpensive. Can be built.

DESCRIPTION OF SYMBOLS 1 External box 3 Internal box 5 Transmitting antenna 7 Receiving antenna 9 Upper plate 11 Lower plate 13 Side plate 15 Opening 17 Radio wave absorber 19 Spacer 21 Resistance film 21
23 Dielectric substrate 27 Reflective element 29 Slide rail

Claims (4)

A first box formed of a material having a property of reflecting radio waves;
Arranged in the first box and formed in a columnar shape by a material having a property of reflecting radio waves, and a plurality of openings having a size capable of passing radio waves in the used frequency band are arranged on the side plate . A second box,
A radio wave absorber provided on the inner surface of the second box;
A transmitting antenna disposed between the first and second boxes and radiating radio waves in the use frequency band;
A passage amount limiting means for limiting a passage amount of the polarization component in the specific direction of the radio wave at the opening of the second box;
Displacement means for changing a reception position in the second box;
A plurality of dielectric substrates arranged in a circumferential direction of the second box, and arranged in a superposed manner so as to be attached to and detached from the outer surface of the side plate of the box,
Equipped with a,
The passage amount limiting means is a reflective element that reflects the polarization component in the specific direction, is formed by a metal foil attached to the dielectric substrate, and is formed in a corresponding opening of the second box. propagation environment controlled wave reflector box characterized that you limit the throughput of the polarization component in the specific direction.   The propagation environment control type radio wave reflection box according to claim 1, wherein the first box has a rectangular parallelepiped shape, and the second box has a polygonal column shape. The second box is arranged so that a central axis is vertical, and the passing amount limiting means is configured to set a horizontal direction radio wave passing angle range centering on the central axis. The propagation environment control type radio wave reflection box according to claim 1 or 2. The propagation environment control type radio wave reflection box according to claim 1, wherein the polarization component in the specific direction is a polarization component in a horizontal direction or a vertical direction.

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