JPS6061664A - Nearby electric field measuring apparatus - Google Patents

Abstract

PURPOSE:To improve the accuracy of directivity obtained with a less measuring time by using a plurality of probes for measuring electric fields near an antenna to be measured to acquire a plurality of nearby electric fields with one scanning. CONSTITUTION:While a power is supplied to an antenna 21 to be measured with a transmitter 20, a probe 22 is moved with a probe driver 29 and a probe position detector 30 detects the position of the probe 22 to sends information to a computer 27. When the position of the probe coincides with that of a sample, the computer 27 uses a microswitch 24 to connect one of output signals of guidewave probes (not illustrated) to a receiver 26 while having other output signals subjected to non-reflection termination 43 to store data into a data storage unit 28. Then, another probe signal is fetched while other probe signals are subjected to the non-reflection termination. This operation is repeated three times to obtain three nearby electric field data with one scanning and a remote field directivity of the antenna being measured is determined for each of data to perform an averaging operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a near-field electric field measuring device that measures an electromagnetic field in the vicinity of an antenna, and particularly relates to a probe scanning method.

[Technical background of the invention and its problems] As shown in FIG. 1, a conventional plane scanning near-field electric field measurement device consists of an open antenna under test 1, a transmitter 2 feeding power to the antenna under test 1, and an electric field of the antenna under test. It consists of a measuring probe 3, a device 4 for driving this probe, a receiver 5, and a device 6 for accumulating and processing measurement data.

In near-field measurement, two probes with different characteristics are used to measure the amplitude and phase of the near-field at each measurement point on a two-dimensional plane using only one probe, and then this measurement is performed using different characteristics. This is done using a probe that has a

Generally, a probe 3 that measures only the X polarization is scanned on a two-dimensional plane with respect to the antenna 1 to be measured, and the amplitude and phase of each measurement point are measured.
It is rotated to scan a two-dimensional plane, measuring only the X polarized wave, and measuring the amplitude and phase at each measurement point.

Based on the measured values of the X and X polarizations, the processing device 6 performs calculations such as Fourier transform to determine the far-field radiation pattern, gain, etc. of the antenna 1 to be measured.

In order to determine the far-field characteristics of the antenna under test in plane scanning near-field measurements, it is necessary to use two probes with different directivity, or to rotate the same probe by 9 degrees and measure with orthogonal polarization. So, twice.

The same scanning plane must be scanned. Since it takes time to measure the line with this probe scanning method, there is a probability that level fluctuations will occur due to transmitter/receiver fluctuations during that time, and error factors such as the accuracy of the probe's measurement position will occur due to scanning twice. growing.

Furthermore, even if information is acquired in one scan using a single probe that simultaneously receives orthogonal polarized waves, level fluctuations and probe measurement position accuracy may occur due to the above-mentioned fluctuations in the transceiver. This error causes a random error in the far-field directivity of the antenna under test. The above random error is a problem, although it depends on the required accuracy of the directivity obtained by near-field measurement.

Although it is possible to obtain accurate received signal information by increasing the accuracy of the measurement position by using an optical system, etc., K has the drawback of being extremely expensive.

[Purpose of the Invention] The present invention has been made in view of the above points. Obtain nearby electric field data for 1000 yen, and use these data to reduce errors that occur in the far-field directivity of the antenna under test.
It is an object of the present invention to provide a near-field electric field measurement device that improves the accuracy of the directivity obtained.

[Summary of the invention]

The present invention uses a plurality of probes that measure the electric field near the antenna under test, sets the distance between the measurement probes at a distance such that the amount of mutual coupling between the probes is 140 dB or less, and sets the sample interval to the distance between the probes. The present invention provides a near-field measuring device that measures a plurality of near-field electric field values in one scan using a system set to a fraction of an integer.

[Effects of IjlJ] According to the present invention, when the probe is installed so as to receive the orthogonal polarized waves shown in FIG. 2(a), it is possible to obtain near electric field data of the antenna to be measured with one scan.

When this method is used, the scanning time is shortened and the probability that error factors such as receiver and transmitter fluctuations and probe position errors will be introduced is reduced, so errors occurring in far-field directivity are also reduced and accuracy is improved.

In addition, as shown in Figure 2(b), if data is acquired using three probes that receive the same polarized wave, three far-field directivities of the antenna under test can be obtained for each probe. , by averaging these data,
The amount of error is averaged, and the accuracy of the obtained directivity is improved.

Also, the three probes are at the same sample point.

Since data is collected, it is possible to compare and correct neighboring electric field values.

Therefore, by using the present invention, the accuracy of the antenna characteristics obtained can be improved. The system does not need to use an optical system, and the manufacturing cost of the device can be reduced.

[Embodiments of the invention] An embodiment of the present invention is shown in FIG.

The present invention includes a transmitter, an antenna to be measured 21, a plurality of probes n, a device frame for driving the probes on a two-dimensional plane, a switching device U for switching RF signals from the probes, and a receiver. , a control uF #27 made up of a computer, a device for storing probe position type information and received signals, a device 29 for driving the probe, and a device (9) for detecting the position of the probe.

The operation of the present invention will be described below with reference to specific examples. 1
As an example, Fig. 4 shows an antenna to be measured 31 and two open
0 showing a measurement system consisting of ended waveguides 32 and 33
In this measurement system, a voltage vO1 is applied to the antenna 31 under test.
Let al be the incident signal when the transmitter 34, which is an internal resistance ZO, is connected. Furthermore, the incident signal to the probe of $1.1 is changed to b2. Let it be ba.

In FIG. 4, when only the probe +1 exists, the signal level generated by the antenna under test 31 at the Brobner 1 is b2, b2 = 812 al-(1) 812 represents the transmission function from the antenna under test to the waveguide 32. Similarly, the signal level b3 that occurs on Blobner 2 when only Blobner 2 is present is expressed as a coefficient: ba = 81311
−(2) It is expressed as

Next, in the case where Blowbunners 1 and 2 are present at the same time, the amount of light that is scattered and reflected by Blowbunner 2 and coupled onto Blowbunner 1 is expressed as a coupling coefficient 832. This means that the signal that entered probe +2 goes out to the outside space again and probe +2
It represents an incoming signal.

When probes ◆1 and 2 are placed close to each other, the coefficient 8 of the signal generated by the antenna to be measured 31 at the blower 1
The coefficients 81s of the signals occurring on probe 12 and probe +2 are approximately the same strength.

Therefore, the electric field signal b2 received by probe ÷ 1 is b2
= aI S12 + aI S13 S32 - (3
)=: als, (1+832)...(4
).

Since b2 "'"I S13 when Brobner 2 is not present, the error that occurs on the received signal when probe≠1 due to mutual coupling 832 caused by the presence of probe +2 is given by 832.

The measurement accuracy of near electric field measurement, which is determined by the request for determining the radiation directivity of the antenna under test, generally requires that the error occurring in the receiving near electric field be within 0.1 dB for low side rope antennas and high performance antennas. be. That is, it is clear from equation (4) that the mutual coupling 832 between the probes needs to be -40 dB or less.

FIG. 5 shows the amount of mutual coupling 832 between probes when two waveguides are arranged at a frequency of 12 GHz and the interval d between them is varied. In Figure 5, it can be seen that the amount of mutual bonding forms a periodic wave depending on the distance d9, and it can be seen that the amount of mutual bonding between the E planes, shown by the solid line, is stronger than the amount of bonding on the H plane.

Furthermore, as shown in FIG. 5, there is a range in which the amount of mutual coupling on both the B and H planes is less than -40 dB, and the initial probe spacing d is 4λ.

Therefore, as a specific example, three probes are used as shown in Figure 6.
Let's consider an example using a single individual. The probe needs to receive two polarized signals: a horizontally polarized component and a vertically polarized component of the electric field near the antenna under test.

In the probe arrangement for receiving vertically polarized waves shown in Fig. 6(a), waveguides 40 and 41 are H-plane coupled, and 40 and 42 are H-plane coupled, @horizontal polarized waves shown in Fig. 6(b). The probe arrangement for receiving is that 40 and 41 are in the E plane, and 40 and 42 are in an 11-fold bond. Both li and H-plane coupling need to be -40 dB or less, so from FIG. 5, the probe spacing d1. d2
It can be seen that it is sufficient to select both of them to be 4λ.

Also, measure the electric field near the antenna under test at the probe 4 at the same point.
By sampling at 0, 41, and 42, changes in the received signal due to probe position errors, transmitter/receiver amplitude, and phase fluctuations can be compared using nearby electric field values. For that purpose, the above-mentioned interval d1
．． It is necessary to make d2 an integral multiple of the sample interval. Since it is sufficient to set the interval λ ail between samples to satisfy this condition, here, it is assumed that Si=. That is, the point 40 sampled at 41 will be sampled again 8 samples later.

The probe and drive device move the probe n in the X direction, detect the position of probe z2 between the probe position detection devices, and send that information to the converter n. When the probe position and the sample position match, the device n Using the switch 24, each waveguide probe 40 , 41 , 42
Of the output signals, one is connected to the receiver, and the other output signals are taken in as data only for the non-reflection terminated 43 sil probe signal and stored in the device recorder. Next, another probe signal is taken in, and the other probe signals are terminated without reflection. Repeat this several times for each probe. Within this switching time, errors in the set point due to probe travel can be ignored because the time to capture the received signal is much shorter.

When near electric field data is collected in this way, three pieces of near electric field data can be obtained in one scan for the same scanning plane. Then, for each data, calculate the far-field directivity of the antenna to be measured.

This obtained pattern has an error due to the error factor caused by the level fluctuation of the probe position error transmitter/receiver mentioned above.

Therefore, by performing an averaging operation on the far-field pattern of the antenna under test using three pieces of data, the errors can be averaged.
Errors can be reduced compared to those based on data.

Further, as shown in FIG. 7, by using two waveguides and placing them orthogonally to each other, it is also possible to collect orthogonally polarized received signals.

Using this method, the collection time can be cut in half.

Therefore, the probability that errors occurring in the near-field electric field described above will be introduced is also reduced, so that highly accurate directivity can be achieved.

Further, similar effects may be obtained with a probe other than the waveguide probe shown in FIG.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional near electric field measuring device, Fig. 2 is an explanatory diagram of an example of probe installation, Fig. 3 is a diagram illustrating an embodiment of the present invention, and Fig. 4 is a diagram illustrating the mutual relationship between probes according to the present invention. FIG. 3 is a diagram showing an example of a probe arrangement. Rib...Transmitter, 21...Antenna to be measured,...
・Receiver, n...control device (CVP), data storage device, 4...probe drive device, (9)...
・Position detection device, 31... antenna element, 32,
33... Waveguide, 40, 41, 42... Waveguide probe, 43... Non-reflection termination 0 Agent Patent attorney Noriyuki Chika (and 1 other person) Fig. 1 Fig. 21 tcl) (Mun) Figure 3 Figure 4 Figure 5 Figure 1 included 1 person 3 people 4 included 3＾ Otsuiri burono “Zhouht” Figure 6 Figure 7

Claims (2)

[Claims] (1) An antenna to be measured, a transmitter that feeds power to the antenna to be measured, a probe that measures an electric field near the antenna to be measured, a device that drives this probe, and a device that detects the position of the probe; A device for acquiring a probe reception signal using position information of the probe, a device for acquiring a probe reception signal using the reception signal information and probe position information, and a device for storing the reception signal information, probe position information, etc. In plane scanning near electric field measurement consisting of, a plurality of the probes are provided and the output of the probes controlled by a device that acquires a received signal using position information of the probes is switched between the probes and the receiver. A switching device is provided, and the operation of connecting only one probe output to the receiver and wirelessly terminating the other probe outputs by the switching device is repeated an even number of times for the probes within a sample interval. Nearby electric field measuring device. (2) Set the spacing between the probes that measure the electric field near the antenna under test to a distance such that the amount of mutual coupling between the probes is -40 dB or less, and set the sample spacing to an integer fraction of the distance between the probes. A near-field electric field measuring device according to claim 1, characterized in that: