JP5396601B2 - Radiation efficiency measuring device - Google Patents

Description

  The present invention relates to a technique for measuring radiation efficiency of an antenna. More particularly, the present invention relates to a technique for effectively measuring the radiation efficiency of an antenna by partial spherical scanning.

  Conventionally, the radiation efficiency of an antenna is measured by spherical scanning (SS). This measurement is performed by spherical integration of the radiated electric field of the antenna to obtain the radiated power.

  FIG. 1 shows an example of the configuration of an antenna radiation efficiency measurement system using spherical scanning. This measurement system includes a support unit 10 that rotates in the azimuth direction at a step Δφ, an antenna 20 to be measured installed on the support unit, and a reception probe antenna 30 that receives a signal at a radius r from the antenna to be measured. It is configured. In this measurement system, the azimuth angle of the support unit 10 is rotated by 360 ° in steps Δφ, and at each azimuth angle, the range of θ = 0 to θm is scanned in steps Δθ in the direction orthogonal to the azimuth angle. And measure the received power.

  Actual measurement is performed in an anechoic chamber 50 as shown in FIG. 2 in order to reduce the influence of reflection of electromagnetic waves. Inside the anechoic chamber, a support unit 10, an antenna to be measured 20, a reception probe antenna 30, and a spherical positioner 40 that determines a position on a spherical surface centered on the reception probe antenna are installed. Further, outside the anechoic chamber, a signal generator 110 that supplies a signal to the antenna to be measured, a spectrum analyzer 120 that analyzes a signal from the reception probe antenna, and a signal from the signal generator and the spectrum analyzer are used. And a computer 130 for calculating the radiation efficiency of the antenna under measurement.

  The radiation efficiency η of the antenna is defined by the following equation.

Here, P _in is the signal power to be input from the signal generator to the antenna under test, Pr is the received power obtained by integrating the received power at the receiving probe antenna on the scanning sphere, it can be obtained by the following equation.

  Here, r is the distance from the antenna under measurement to the receiving probe antenna, and A is the opening area of the receiving probe antenna. In addition, it is ideal that the scanning angle θ can be scanned in the range of 0 to π as in the above equation. However, in actual measurement, the maximum scanning angle θm (θm <π) is set by the support unit that supports the antenna to be measured. It will be limited.

Q. Chen, et.al, IEICE Trans. Commun., Vol.E80-B, No.5, pp.709-711, May 1997. Hirokawa, Kuga, Shingaku Sodai, B-1-52, pp.52, March 2004

  As described above, in the conventional measurement of the radiation efficiency of the antenna by spherical scanning, the unscannable range of the receiving probe antenna and the feeder line to the DUT (Device Under Test) can cause measurement errors. Specifically, the support portion may affect the radiation from the antenna under measurement. In addition, the support portion becomes an obstacle, and scanning by the reception probe antenna is limited to a range of 0 to θm. For this reason, contrivances have been made such as supporting an azimuth turntable composed of a foaming agent from the side and incorporating a transmitter into the DUT, but both require special equipment and are expensive. There is.

  The present invention has been made in view of such problems, and the object is to concentrate the radiation field of the antenna under measurement on the upper hemisphere so that the radiation efficiency can be measured by partial spherical scanning. It is an object to provide a method and apparatus.

In order to achieve such an object, the present invention provides a device for measuring the radiation efficiency of an antenna by spherical scanning, which supports the antenna to be measured and the antenna to be measured. Moving in a plane perpendicular to the azimuth angle direction, a support portion that rotates the azimuth angle direction, a reflector plate that is located between the support portion and the antenna to be measured and is spaced apart from the antenna to be measured by, and a receiving antenna for receiving a signal from the antenna under test at a fixed distance, a spherical above the reflecting plate from the top of the antenna under test, the receiving antenna is configured to scan It is characterized by that.

The invention of claim 2 is the apparatus of claim 1, said receiving antenna is moved in a plane orthogonal to the azimuthal direction, at least from the top of the previous SL antenna under test It is configured to scan a range of 120 °.

Further, the invention according to claim 3, The apparatus according to claim 1 or 2, the distance d between the measured antenna and the reflector, as a measurement signal wavelength λ, d ≦ 0.7λ It is characterized by being.

The invention according to claim 4 is the apparatus according to claim 1 , 2 or 3 , wherein the diameter 2a of the reflecting plate is 2a ≧ 2. It is 6λ .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3 shows a configuration example of an antenna radiation efficiency measurement system according to the present invention. This measurement system includes a support unit 10 that rotates in the azimuth direction at a step Δφ, a circular reflector 60 installed on the support unit, a measured antenna 20 that is installed at a distance d from the reflector, and The receiving probe antenna 30 receives a signal at a distance of a radius r from the antenna to be measured. In this measurement system, the azimuth angle of the support unit 10 is rotated by 360 ° in steps Δφ, and at each azimuth angle, the range of θ = 0 to θm is scanned in steps Δθ in the direction orthogonal to the azimuth angle. And measure the received power. Further, the actual measurement is performed in an anechoic chamber 50 as shown in FIG. 2 as in the case of the prior art.

  According to the present invention, since downward radiation from the antenna to be measured can be suppressed by the reflector, the influence of the support portion in the radiation efficiency measurement can be reduced. Further, since the radiation from the antenna to be measured is reflected upward by the reflecting plate, sufficient radiation efficiency can be measured by partial scanning of the hemispherical surface above the reflecting plate.

  FIG. 4 shows a state in which downward radiation from the antenna under measurement is suppressed by the reflector. Here, FIG. 4 shows a result when a dipole antenna is used.

  FIGS. 4A and 4B are H-plane and E-plane antenna patterns obtained by conventional spherical scanning (that is, without a reflector), respectively, and the scanning angle θ is changed from 0 to 165 °. FIGS. 4C and 4D are H-plane and E-plane antenna patterns according to the present invention (that is, with a reflector), respectively, and the scanning angle θ is similarly changed from 0 to 165 °. Comparing FIGS. 4 (a) and 4 (c) and FIGS. 4 (b) and 4 (d), it can be seen that the downward radiation from the antenna under measurement is suppressed when the reflector is used. Here, the H plane and the E plane are observation planes of the antenna pattern when the azimuth angle φ is 90 ° different in FIGS. 1 and 3, and are observation planes when φ = 90 ° and φ = 0 °, respectively. is there.

  Next, the distance d between the antenna under measurement and the size of the reflector will be examined. FIG. 5 shows a radiation efficiency with respect to a distance d / λ where a measurement signal wavelength is λ and a standard dipole antenna (2 GHz) is used for both the antenna to be measured and the receiving probe antenna in the configuration of FIG. When the radius a of the reflecting plate is a = 0.7λ, FIG. 5B shows the case where a = 1.3λ.

  In general, when the diameter of the reflector increases, the amount of reflection by the reflector increases, and the radiation efficiency is considered to be less dependent on the maximum scanning angle θm. That is, power is concentrated on the upper hemisphere by the reflector, and the radiation efficiency can be effectively measured by scanning only the upper hemisphere. From the results of FIGS. 5A and 5B, when the radius a = 1.3λ, the dependency on the maximum scanning angle θm is reduced, and the effect of the reflector can be confirmed.

  In general, when the distance d between the antenna and the reflector is close, the amount of reflection by the reflector increases, and the radiation efficiency is considered to be less dependent on the maximum scanning angle θm. That is, power is concentrated on the upper hemisphere by the reflector, and the radiation efficiency can be effectively measured by scanning only the upper hemisphere. From the result of FIG. 5B, the dependency on the maximum scanning angle θm is reduced in the range of d ≦ 0.7λ, and the effect of the reflector can be confirmed in this range.

  Next, the determination of the optimum value of the parameter will be considered. FIG. 6 shows the radiation efficiency in the case of using the standard dipole antenna (2 GHz) for the antenna to be measured and the receiving probe antenna in the configuration of FIG. 3 and using the distance d and the radius a of the reflector as parameters with the measurement signal wavelength being λ. Is shown. Specifically, using the radius a as a parameter, a calculated value (dotted line) and an actual measurement value (solid line) of the radiation efficiency η with respect to the maximum scanning angle θm are shown, and FIG. 6A is a case where d = 0.3λ. FIG. 6B shows the case where d = 0.6λ.

  Although the actual measurement value in FIG. 6A is smaller than the distance d in FIG. 6B, the overall radiation efficiency is lowered. This is caused by the leakage current absorbed by the radio wave absorber wound outside the feeder line, and is caused by the deterioration of the VSWR (Voltage Standing Wave Ratio). Further, from FIGS. 6A and 6B, when the maximum scanning angle θm is 120 ° or more, the radiation efficiency is not so affected by the distance d and the radius a, and can be regarded as almost constant. Further, from FIGS. 6A and 6B, the larger the radius “a” of the reflector, the less the wraparound of the radio wave and the more stable the reflection efficiency. From the above, under this measurement condition, the distance d = 0.6λ, θm = 120 °, and radius a = 2.3λ can be said to be the optimum parameter settings. The difference between the calculated value and the actually measured value is about 10 to 15%, and numerical integration error, copper loss, manufacturing error, power absorption in an absorber wound outside the feeder line, and the like can be considered.

  Next, the difference in the effect of the reflector on the polarization will be examined. FIG. 7 shows the installation state of the antenna to be measured with respect to the reflector and each antenna pattern, and FIG. 8 shows the radiation efficiency with respect to the maximum scanning angle θm in each installation state. Specifically, FIG. 7A shows a state where the polarization planes of the reflector and the antenna to be measured are installed horizontally, and FIG. 7B shows the polarization plane of the reflector and the antenna to be measured being vertical. The installed state is shown. 7C shows the antenna pattern of the antenna under measurement in the state of FIG. 7A, and FIG. 7D shows the antenna pattern of the antenna under measurement in the state of FIG. 7B. Yes. FIG. 8 shows the radiation efficiency with respect to the maximum scanning angle θm in the horizontal installation state, the vertical installation state, and the state without the reflector. At this time, the radius a of the reflector is a = 2.3λ, the distance d is d = 0.6λ, and a 2.45 GHz dipole antenna is used for the DUT.

  From FIG. 8, the drop in radiation efficiency is larger in the vertical installation state than in the horizontal installation state. This suggests that the wraparound of the radio wave is larger in the vertically installed state. When the maximum scanning angle θm is 120 ° or more in the horizontal installation state and 90 ° or more in the vertical installation state, there is almost no deterioration in radiation efficiency. Therefore, if the maximum scanning angle θm is 120 °, sufficient radiation efficiency can be measured regardless of the polarization.

  Finally, in order to examine the validity of the radiation efficiency measurement method according to the present invention, a comparison result with the radiation efficiency measurement by the waveguide method is shown. FIG. 9 shows the results of radiation efficiency measurement for several antennas under measurement using the waveguide method and according to the present invention. As the antenna to be measured, three types of chip antennas (antenna numbers 1 to 3) and one type of printed dipole antenna (antenna number 4) were used. As shown in the figure, the measurement result is higher in the waveguide method than in the method according to the present invention, and the difference is about 10 to 15%. This is considered to be due to the loss in the absorber applied to the outer skin of the feeder line in the case of the chip antenna and the loss of the balun in the case of the printed dipole antenna. However, the tendency of the measurement results is the same in both measurement methods, and it can be seen that the measurement of the radiation efficiency according to the present invention is appropriate.

  As described above, by using the reflecting plate, the radiation power from the antenna to be measured can be concentrated on the upper hemisphere, and the radiation efficiency can be measured only by partial scanning of the upper hemisphere. Then, by appropriately setting the distance between the antenna to be measured and the reflecting plate, the size of the reflecting plate, and the maximum scanning angle, the radiation efficiency of the antenna can be measured with sufficient accuracy. Thereby, the influence of the support part in radiation efficiency measurement is reduced, and effective radiation efficiency measurement can be performed in a narrow scanning range.

  Although the present invention has been described with respect to specific embodiments, the embodiments described herein are merely illustrative in view of the many possible embodiments to which the principles of the present invention can be applied, and are within the scope of the present invention. It is not intended to limit. For example, the present invention can be applied not only to measurement of radiation efficiency of an antenna but also to measurement of radiated power of a wireless device or the like. As described above, the configuration and details of the embodiment exemplified here can be changed without departing from the gist of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

It is a figure which shows the structure of the radiation efficiency measuring system of the antenna by the conventional spherical scan. It is a figure which shows the whole environment which performs the radiation efficiency measurement of an antenna. It is a figure which shows the structure of the radiation efficiency measuring system of the antenna by this invention. FIGS. 4A and 4B show antenna patterns on the H plane and E plane when there is no reflector, and FIGS. 4C and 4D show antenna patterns when a dipole antenna is used. ) Are antenna patterns on the H plane and E plane when there is a reflector. FIG. 5 is a graph showing the radiation efficiency with respect to the distance d / λ in the configuration of FIG. 3. FIG. 5A shows a case where a = 0.7λ, and FIG. 5B shows a case where a = 1.3λ. is there. FIG. 6 is a graph showing the radiation efficiency when the distance d and the radius a of the reflector are used as parameters in the configuration of FIG. 3, and FIG. 6 (a) shows the result when d = 0.3λ. b) shows the result when d = 0.6λ. It is a figure which shows the installation state of the to-be-measured antenna with respect to a reflecting plate, and each antenna pattern, and FIG. FIGS. 7C and 7D show the antenna patterns of the antenna under measurement in the states of FIGS. 7A and 7B, respectively. It is a graph which shows the radiation efficiency with respect to the maximum scanning angle (theta) m in a horizontal installation state, a vertical installation state, and the state without a reflecting plate. It is a graph which shows the result of the radiation efficiency measurement in the case of using the waveguide method and the case of the present invention for several antennas to be measured.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Support part 20 Antenna to be measured 30 Reception probe antenna 40 Spherical positioner 50 Anechoic chamber 60 Reflector 110 Signal generator 120 Spectrum analyzer 130 Computer

Claims (4)

An apparatus for measuring the radiation efficiency of an antenna under measurement by spherical scanning,
A support unit for supporting the antenna under measurement and rotating the antenna under measurement in an azimuth direction;
A reflector disposed between the support portion and the antenna to be measured and spaced from the antenna to be measured;
A receiving antenna that receives a signal from the antenna under measurement at a certain distance by moving in a plane orthogonal to the azimuth direction;
An apparatus , wherein the receiving antenna scans a spherical surface above the reflecting plate from above the antenna to be measured . The apparatus of claim 1, comprising:
The receiving antenna can be moved in a plane orthogonal to the azimuthal direction, before Symbol apparatus characterized by being configured to scan a range of at least 120 ° from the top of the antenna under test. The apparatus according to claim 1 or 2, comprising:
The distance d between the reflector and the antenna to be measured is d ≦ 0.7λ, where λ is a measurement signal wavelength. The apparatus according to claim 1, 2 or 3,
The diameter 2a of the reflecting plate is 2a ≧ 2.6λ.

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