JP3593566B2 - Antenna measuring method and antenna measuring device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an antenna measuring device used for measuring antenna gain.
[0002]
[Prior art]
2. Description of the Related Art In recent years, far-field measurement and near-field measurement are well known as methods for measuring the characteristics of antennas in which the use of radio waves is diversified and various technologies are introduced.
[0003]
The far-field measurement is a method of measuring an electromagnetic field distribution in a far-field region where the distance R from the antenna is 2D ² / λ <R (D: antenna diameter, λ: wavelength). The near-field measurement is a method of measuring the electromagnetic field distribution in the near-field region where the distance R from the antenna is λ / π <R <2D ² / λ. Each of these methods has advantages and disadvantages, but the characteristics of the antenna can be measured using these methods.
[0004]
In addition, a method in which a comparison method generally used in far-field measurement is applied to near-field measurement is often used as a method of measuring an antenna gain, which is one of indexes indicating characteristics of an antenna.
[0005]
[Problems to be solved by the invention]
However, in the near-field measurement, since the measurement time is generally longer than that in the far-field measurement, the signal power tends to change during the measurement, and the change increases as the frequency increases. When the comparison method is applied to the field measurement, there is a problem that it appears as a measurement error of the antenna gain as it is.
[0006]
Then, this invention makes it a main subject to solve the above-mentioned problem.
[0007]
[Means for Solving the Problems]
That is, according to the present invention, an antenna measurement for obtaining the antenna gain of the test antenna by continuously measuring each of the reference antenna having a known antenna gain and the test antenna having the unknown antenna gain as a measured antenna in the near field. A near-field electric field distribution of the measured antenna obtained by measuring a plurality of scanning points arranged on a surface facing the measured antenna based on a reference signal power measured at a reference point set at a predetermined position. A first calibration unit for calibrating the antenna, and a second field for calibrating the near-field electric field distribution of the measured antenna measured immediately thereafter based on the power offset at the reference point generated during the measurement of the measured antenna previously. And a calibration unit.
[0008]
Here, the antenna gain indicates a gain in a direction indicating the maximum radiation direction of the antenna unless the direction is specified.
[0009]
According to such a configuration, measurement can be sufficiently performed even indoors, and calibration can be performed even when a change in signal power occurs during measurement, so that measurement accuracy is high, and high-precision measurement is performed even when the measurement frequency is increased. It is possible to provide an antenna measuring apparatus having extremely excellent measurement performance such as capable of performing the measurement.
[0010]
Further, as a specific embodiment of the present embodiment, the power offset indicates a power difference between a reference signal power at the start of measurement and a reference signal power at the end of measurement of the antenna to be measured previously. It is preferable that
[0011]
Further, in order to perform measurement with a small measurement error, the reference point disposed at the predetermined position may be provided on or near the scanning center axis of the antenna to be measured. Further, an embodiment is also conceivable in which a plurality of reference points arranged at the predetermined positions are provided near the scanning center axis, and the reference signal power averages the signal power at the plurality of reference points. .
[0012]
Further, as a method of reducing the measurement error, the reference signal power is measured during measurement of the near-field electric field distribution of the antenna to be measured, using the same probe as that for measuring the antenna to be measured. It is preferable that the same probe alternately measures the scanning point and the reference point.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
As shown in FIG. 1, the antenna measuring apparatus 1 of the present invention is connected to a measured antenna support 21 for supporting the measured antenna 2, a probe 3, a moving device 4, the measured antenna 2, the moving device 4, and the like. The main measuring device 5 and the like described later are the main constituent elements. The main parts of these parts are set to be used, for example, in an anechoic chamber R provided with a radio wave absorbing material (not shown).
[0015]
The measured antenna support unit 21 selectively supports one of the reference antenna 2s having a known antenna gain and the test antenna 2a having an unknown antenna gain. In the present embodiment, the reference antenna 2s and the test antenna 2a supported by the measured antenna support 21 are connected to a connection line having a loss Ls and a connection line having a loss La, respectively. It is set to emit radio waves generated by a signal generator that does not. In this embodiment, the loss Ls and La are both known. However, the present invention is not limited to this, and there may be an embodiment in which the loss is measured and measured when each antenna is measured. Further, there may be an embodiment in which one of the antennas 2s and 2a to be measured is connected to one connection line.
[0016]
The probe 3 receives a radio wave radiated from the measured antenna 2 supported by the measured antenna support 21.
[0017]
The moving device 4 supports the probe 3 movably in a plane PL facing the antenna 2 to be measured. This plane PL has a plurality of scanning points P ₁ , P _2, ... Which are measurement points. In this embodiment, these scanning points P ₁ , P _2, ... Are collectively referred to as scanning points P.
[0018]
In the present embodiment, the moving device 4 is movably supported in the plane PL facing the antenna 2 to be measured. However, the present invention is not limited to this. For example, the moving device 4 moves a three-dimensional space to an arbitrary position. It may be possible.
[0019]
The main measurement device 5 controls the measurement in the present system, and as shown in FIG. 2, a CPU 501, an internal memory 502, an external storage device 503 such as an HDD, and a user interface 504 such as a keyboard and a mouse. , A display unit 505 such as a display, a transmission / reception unit 506 for transmitting / receiving data to / from the probe 3, the mobile device 4, and the like.
[0020]
The main measuring device 5 operates the CPU 501 and peripheral devices according to the programs stored in the external storage device 503, the internal memory 502, and the like, and as shown in FIG. Section 521, radio wave receiving section 522, reference antenna scanning point power storage section 531, reference antenna reference point power storage section 532, test antenna scanning point power storage section 533, test antenna reference point power storage section 534, system control section 541. , A storage unit 551, a characteristic curve generation unit 560, a first calibration unit 561, a reference antenna first calibration result processing unit 562, a test antenna first calibration result processing unit 563, a second calibration unit 564, an output unit 571, and the like. Function.
[0021]
These components will be described in detail below.
[0022]
The signal generator 511 is set so that the antenna under measurement 2 generates a radio wave when receiving an instruction to generate a signal from the system controller 541.
[0023]
The probe position controller 521 receives the instruction from the system controller 541, and controls the moving device 4 to sequentially move the probe 3 to a scanning point P or the like as a measurement point. In the present embodiment, when moving from a plurality of scanning points P to the next plurality of scanning points P, the probe 3 moves to a reference point D, and the probe 3 measures signal power at this reference point D as well. I have. Since the reference point D is further composed of four vertices D1, D2, D3, and D4 of a square surrounding the scanning center axis C, if these measurement orders are shown more specifically, the first scanning point P ₁ , a second scanning point P ₂ ,..., An N-th scanning point P _N , reference points D1, D2, D3, D4, an [N + 1] -th scanning point P _{N + 1} , and an [N + 2] -th scanning point P _{N + 2} ,... The signal power at each measurement point is measured in the order of [2N] th scanning point P _2N , reference points D1, D2, D3, D4, [2N + 1] th scanning point P _{2N + 1.} . Note that one measurement time at a plurality of scanning points P is set to 180 seconds.
[0024]
The radio wave receiving unit 522 receives a measured value of the signal power received by the probe 3.
[0025]
The reference antenna scanning point power storage unit 531 is formed in a predetermined area such as the internal memory 502 and stores a measured value of the reference antenna scanning point reception power at each scanning point P radiated by the reference antenna 2s. Things.
[0026]
The reference antenna reference point power storage unit 532 is formed in a predetermined area of the internal memory 502 or the like, and is measured during scanning of the reference antenna 2s. It stores the measured value of the point reception power.
[0027]
The test antenna scan point power storage unit 533 is formed in a predetermined area of the internal memory 502 or the like, and is a measured value of the test antenna scan point reception power at each scan point P radiated by the test antenna 2a. Is stored.
[0028]
The test antenna reference point power storage unit 534 is formed in a predetermined area of the internal memory 502 or the like, and is measured during the scanning of the test antenna 2a, at the reference point D radiated by the test antenna 2a. It stores the measured value of the test antenna reference point received power.
[0029]
The system control unit 541 controls the entire system of the antenna measuring device 1. More specifically, it is set so that the probe position control unit 521 is controlled so as to sequentially move the probe 3 to the scanning point P or the like. In addition, it is set so that the measured value of the signal power received by the radio wave receiving unit 522 is stored in the reference antenna scanning point power storage unit 531 or the like.
[0030]
More specifically, the measured value of the signal power received by the radio wave receiving unit 522 is stored in the reference antenna scanning point power storage unit 531, the reference antenna reference point power storage unit 532, and the test antenna scanning point power storage unit according to four conditions. 533, the storage unit 551 is instructed to be stored in the test antenna reference point power storage unit 534, respectively. Further, these conditions will be described in detail. When the measured antenna 2 is the reference antenna 2s and the probe 3 is located at the scanning point P, the measured value of the received signal power is stored in the reference antenna scanning point power storage unit 531. Is set so as to instruct the accumulation unit 551 to be stored in the storage unit 551. When the measured antenna 2 is the reference antenna 2 s and the probe 3 is located at the reference point D, the storage unit stores the measured value of the received signal power in the reference antenna reference point power storage unit 532. 551. When the antenna under test 2 is the antenna under test 2a and the probe 3 is located at the scanning point P, the measured value of the received signal power is stored in the antenna scanning point power storage unit 533 under test. It is set to instruct the storage unit 551. When the antenna under test 2 is the test antenna 2a and the probe 3 is located at the reference point D, the measured value of the received signal power is stored in the test antenna reference point power storage unit 534. It is set to instruct the storage unit 551.
[0031]
The storage unit 551 stores the measured value of the signal power received by the radio wave receiving unit 522, based on an instruction from the system control unit 541, in the reference antenna scan point power storage unit 531, the reference antenna reference point power storage unit 532, The test antenna scan point power storage unit 533 and the test antenna reference point power storage unit 534 are stored.
[0032]
The characteristic curve generator 560 includes a reference antenna reference point received power measurement value and a measured antenna reference point received power stored in the reference antenna reference point power storage unit 532 and the test antenna reference point power storage unit 534, respectively. Based on the measured values, a reference-point signal power characteristic curve indicating each change with time at the reference point D is generated. More specifically, this reference point signal power characteristic curve indicates, for example, as shown in FIG. 4, a change in reference signal power between a reference signal power Ps at the start of measurement and a reference signal power Pe at the end of measurement. Is plotted with the horizontal axis as the time axis and the vertical axis as the reference point amplitude determined from the change in the reference signal power. The reference point amplitude is obtained by taking an average value of the reference points D1, D2, D3, and D4, and is plotted by setting the average value of the reference signal power Ps at the start of the measurement to 0 dB. I have. In addition, a reference point signal power difference Pd, which is a power offset between the reference signal power Ps at the start of measurement and the reference signal power Pe at the end of measurement, is set to be output to the second calibration unit 564.
[0033]
The first calibration unit 561 includes a measured value of the reference antenna scan point received power stored in the reference antenna scan point power storage unit 531 and a test antenna scan stored in the test antenna scan point power storage unit 533. A near-field electric field distribution before calibration is generated from the measured value of the point received power, and the generated near-field electric field distribution before calibration is calibrated based on the reference point signal power characteristic curve obtained by the characteristic curve generation unit 560. Then, a near-field electric field distribution after each calibration is generated.
[0034]
The reference antenna first calibration result processing unit 562 generates the peak power Ps' based on the near-field electric field distribution of the reference antenna 2s after calibration obtained by the first calibration unit 561. More specifically, the near-field electric field distribution after the calibration of the reference antenna 2s obtained by the first calibration unit 561 is subjected to near-field / far-field conversion processing to obtain a far-field radiation pattern. The peak power Ps' is set to be generated from the far-field radiation pattern.
[0035]
The test antenna first calibration result processing unit 563 uses the same method as the reference antenna first calibration result processing unit 562 to calculate the near-field electric field distribution of the test antenna 2a obtained by the first calibration unit 561 after calibration. Is used to generate a peak power Pa ′.
[0036]
The second calibration unit 564 outputs the reference point signal power difference Pd output from the characteristic curve generation unit 560, the reference point signal power difference Pd, and the reference antenna first calibration result processing unit 562. Based on the peak power Ps ′ of the reference antenna 2s, the peak power Pa ′ of the test antenna 2a output from the test antenna first calibration result processing unit 563, and the like, the test antenna 2a Is output to the output section 571.
[0037]
(Equation 1)
[Ga] = [Gs]-[La] + [Ls] + [Pa ']-[Pd]-[Ps']
(Unit: dB)
The output unit 571 displays the gain Ga and the like of the test antenna 2a output from the second calibration unit 564 on the screen of the display unit 505, or prints out the output with a printer (not shown).
[0038]
Next, the operation of the system according to the present embodiment will be described with reference to the flowcharts shown in FIGS.
[0039]
FIG. 5 is a flowchart showing a process of measuring the reference antenna 2s and the test antenna 2a in this order, and measuring the antenna gain Ga of the test antenna 2a.
[0040]
Replace the reference antenna 2s to the antenna under test supporting unit 21, and sets the probe 3 at the scanning point _{P 1} (step S101), performs a power measurement at the scanning point _{P 1} (step S102). Then, when the measurement ends at the scanning point _{P 1} (step S103), moves the probe 3 to the next measurement point (step S101), performs the measurement in the next measurement point (step S102). In this embodiment, the order of measurement at each measurement point is as follows: scanning points P ₁ , P ₂ ,..., P _n , reference point D, scanning points P _{n + 1} , P _{n + 2 ,.} As in the case of the reference points D,..., The measurement at the reference point D is set between the measurements of the plurality of scanning points P and the next scanning point P. The measurement at the reference point D is set to be performed at four measurement points D1, D2, D3, and D4 constituting the reference point D. In this way, when the power measurement at all the measurement points for the reference antenna 2s is completed (step S103), the antenna under test 2 is replaced with the test antenna 2a from the reference antenna 2s (step S104). The power is measured at all the measurement points for the test antenna 2a (steps S105 to S107).
[0041]
In the power measurement in steps S102 and S106, the following processing is performed as a measurement routine.
[0042]
Specifically, as shown in FIG. 6, when a signal is generated by the signal generation unit 511 (step S201), the measured antenna 2 attached to the measured antenna support 21 emits a radio wave (step S202). The radio wave receiving unit 522 receives the radio wave received by the probe 3 as a measured value of the signal power (Step S203).
[0043]
When the measured antenna 2 is the reference antenna 2s (step S204), the operation is performed as follows. When the probe 3 is located at the scanning point P (Step S205), the measured value of the received signal power is stored in the reference antenna scanning point power storage unit 531 (Step S206). If it is located at the point D (step S205), the measured value of the received signal power is stored in the reference antenna reference point power storage unit 532 (step S207).
[0044]
On the other hand, when the antenna under test 2 is the test antenna 2a (step S204), the operation is performed as follows. When the probe 3 is located at the scanning point P (step S208), the measured value of the received signal power is stored in the test antenna scanning point power storage unit 533 (step S209), and the probe 3 is set at the reference point. If it is located at D (step S208), the measured value of the received signal power is stored in the test antenna reference point power storage unit 534 (step S210).
[0045]
In the present embodiment, the setting is made such that the radio wave emission ends after each measurement at each measurement point (step S211), the probe 3 is moved (steps S101, S105), and the radio wave is again emitted. (Step S201) is not limited to this, and an embodiment in which radio waves are emitted while the probe 3 is moving may be considered.
[0046]
The first calibration is performed based on the measurement results of the reference antenna 2s and the test antenna 2a obtained by the measurement as described above (step S108).
[0047]
Note that this step S108 has a function as a subroutine for performing the first calibration, and the processes of steps S301 to S312 are performed as shown in FIG. More specifically, for the reference antenna 2s, a near-field electric field distribution before calibration is generated from the measured value of the reference antenna scanning point received power stored in the reference antenna scanning point power storage unit 531 (step S301). Further, based on the measured value of the reference antenna reference point received power stored in the reference antenna reference point power storage unit 532, a reference point signal power characteristic curve indicating a temporal change at the reference point D is generated (step S302). Then, the near-field electric field distribution of the reference antenna 2s is calibrated based on the reference point signal power characteristic curve, and the calibrated near-field electric field distribution is obtained (step S303). Further, near-field-far-field conversion is performed on the calibrated near-field electric field distribution (step S304), a far-field radiation pattern is generated (step S305), and peak power Ps' is obtained from the far-field radiation pattern (step S305). Step S306).
[0048]
Similarly, the peak power Pa 'is obtained for the test antenna 2a (steps S307 to S312).
[0049]
The second calibration is performed on the peak power Ps 'of the reference antenna 2s and the peak power Pa' of the test antenna 2a obtained as described above (step S109), and the gain Ga of the test antenna 2a is obtained (step S110).
[0050]
Note that step S109 has a function as a subroutine for performing the second calibration, and the processes of steps S401 to S402 are performed as shown in FIG. More specifically, the measurement start time and the measurement end time of the reference point signal power characteristic curve obtained for the reference antenna 2s are obtained, and the reference point signal power difference Pd is obtained from these (step S401). Based on the power difference Pd and the peak powers Ps 'and Pa', the gain Ga of the test antenna 2a is obtained from the above equation 1 (step S402).
[0051]
The gain Ga of the test antenna 2a thus obtained is set to be displayed on the display unit 505 on the screen (step S110).
[0052]
Next, based on the measurement conditions shown in FIG. 9, a description will be given of a verification experiment result of the antenna measurement device 1 according to the present embodiment when the measurement 1 of the reference antenna 2s and the measurement 2 of the test antenna 2a are continuously performed. I do.
[0053]
In this verification experiment, the reference antenna 2s and the test antenna 2a were measured with the same antenna. For this reason, these gain differences obtained by measurement should theoretically be 0 dB.
[0054]
FIG. 9 shows the measurement conditions of the verification experiment.
[0055]
Specifically, the antenna used for the measurement is an aluminum mirror surface, circularly polarized wave feeding offset parabolic antenna. The near-field measuring device (not shown) used for the measurement is a device which is installed in the anechoic chamber of the Kashima Space Communication Research Center of the Communications Research Laboratory, and is capable of scanning 1.8 mx 1.8 m planes. The measurement frequencies are 28 GHz and 40 GHz. As the reference point D, the vertices D1, D2, D3, and D4 of the square centered on the scanning center axis C were selected as the reference points. The interval between these four points is set to 20 cm. The cycle for measuring the reference point was 180 seconds.
[0056]
FIG. 10 shows the results of the verification experiment.
[0057]
At a measurement frequency of 28 GHz, the gain difference when no calibration was performed was -0.24 dB, and the gain difference when performing the first calibration and the second calibration was 0.06 dB. On the other hand, at 40 GHz, the gain difference without any calibration was 1.69 dB, and the gain difference when performing the first calibration and the second calibration was 0.17 dB.
[0058]
That is, by performing the first calibration and the second calibration on the measurement result, a very excellent measurement result could be obtained. Further, the effect was able to be obtained even at a high frequency.
[0059]
As described in detail above, the antenna measuring apparatus 1 of the present embodiment can sufficiently measure even in a room such as an anechoic chamber, and can perform calibration even if a change occurs in the signal power during measurement, so that the measurement accuracy is high. Further, it is possible to provide an antenna measuring apparatus having extremely excellent measuring performance such that highly accurate measurement is possible even when the measuring frequency is increased.
[0060]
In the present embodiment, the measurement is performed in the order of the reference antenna 2s and the test antenna 2a, but the measurement may be performed in the order of the test antenna 2a and the reference antenna 2s.
[0061]
Further, the radio wave is radiated from the reference antenna 2s and the test antenna 2a, and the radio wave is radiated from the probe 3 and received by the probe 3 to obtain the gain of the test antenna 2a. The signal can be received by the reference antenna 2s and the test antenna 2a to determine the gain of the test antenna 2a.
[0062]
Various methods for replacing the reference antenna 2s with the test antenna 2a may be considered depending on the embodiment, such as an automatic replacement method or a manual replacement method.
[0063]
In addition, a variable attenuator that attenuates the reception signal received by the test antenna 2a by a predetermined attenuation amount α is provided between the connection line having the loss La and the signal generator, and measurement is performed. An embodiment is also conceivable in which measurement is performed by connecting the above devices.
[0064]
Other specific functions and configurations of each unit can also be variously changed within the scope of the present invention.
[0065]
【The invention's effect】
According to the present invention described in detail above, measurement is sufficiently possible even in a room such as an anechoic chamber, and calibration is possible even if a change in signal power occurs during measurement, so that the measurement accuracy is high and the measurement frequency is further increased. In this case, it is possible to provide an antenna measuring device having extremely excellent measurement performance such as high-precision measurement.
[Brief description of the drawings]
FIG. 1 is an overall device configuration diagram according to an embodiment of the present invention.
FIG. 2 is a device configuration diagram showing a main measurement device in the embodiment.
FIG. 3 is a functional configuration diagram showing a main measurement device in the embodiment.
FIG. 4 is a view showing a reference point signal power characteristic curve in the embodiment.
FIG. 5 is a flowchart showing an operation of measuring the gain Ga in the embodiment.
FIG. 6 is a flowchart showing an operation of measuring each antenna under measurement in the embodiment.
FIG. 7 is a flowchart showing the operation of a first calibration unit in the embodiment.
FIG. 8 is a flowchart showing the operation of a second calibration unit in the embodiment.
FIG. 9 is a view showing measurement conditions of a verification experiment in the same embodiment.
FIG. 10 is a view showing experimental results of a verification experiment in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Antenna measuring device 2 ... Measured antenna 2s ... Reference antenna 2a ... Test antenna 3 ... Probe 561 ... First calibration part 564 ... Second calibration part C · · · scanning center axis D, D1, D2, D3, D4 ··· reference point _{P, P 1, P 2,} P 3 ··· scanning point Pd · · · power offset (reference signal power difference)
Ps: Reference signal power at start Pe: Reference signal power at end

Claims (7)

An antenna measurement apparatus for measuring the antenna gain of the antenna under test by continuously measuring each of the reference antenna and the antenna under test whose antenna gain is known and the antenna under test whose antenna gain is unknown in the near field.
A first method for calibrating a near-field electric field distribution of an antenna to be measured obtained by measuring a plurality of scanning points arranged on a surface facing the antenna to be measured based on a reference signal power measured at a reference point set at a predetermined position. Calibration section,
A second calibrating unit for calibrating the near-field electric field distribution of the measured antenna measured immediately after, based on the power offset at the reference point generated during the measurement of the measured antenna previously. Antenna measuring device. 2. The antenna measurement according to claim 1, wherein the power offset indicates a power difference between a reference signal power at the start of the measurement and a reference signal power at the end of the measurement of the antenna under test measured earlier. apparatus. 3. The antenna measuring apparatus according to claim 1, wherein the reference point arranged at the predetermined position is on or near a scanning center axis of the antenna to be measured. A plurality of reference points arranged at the predetermined position are provided in the vicinity of a scanning center axis, and the reference signal power is obtained by averaging signal powers at the plurality of reference points. The antenna measuring device according to claim 3. 4. The apparatus according to claim 1, wherein the reference signal power is measured during measurement of a near-field electric field distribution of the measured antenna by using the same probe as that for measuring the measured antenna. Or the antenna measuring device according to 4. The antenna measuring apparatus according to claim 5, wherein the same probe measures the scanning point and the reference point alternately. An antenna measurement apparatus for measuring the antenna gain of the test antenna by continuously measuring each of the reference antenna and the test antenna whose antenna gain is unknown and the test antenna whose antenna gain is unknown in the near field, and
A program that activates a computer to measure antennas,
A first method for calibrating a near-field electric field distribution of an antenna to be measured obtained by measuring a plurality of scanning points arranged on a surface facing the antenna to be measured based on a reference signal power measured at a reference point arranged at a predetermined position. Calibration section,
A second calibrating unit for calibrating the near-field electric field distribution of the measured antenna measured immediately after, based on the power offset at the reference point generated during the measurement of the measured antenna previously. Antenna measurement program.

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