JP2014002065A - Near field measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near field measuring apparatus capable of sufficiently accurately measuring a tip position of a probe to estimate electric field intensity on a receiving position of K bands or more.SOLUTION: In a radio wave radiation distribution measuring apparatus including a probe for detecting a radio wave from a radio wave radiator and capable of outputting information including electric field intensity information and phase difference information as a detection value by using the probe on a predetermined measurement point, the probe has a deflected polarization characteristic, includes polarization characteristic rotation means for rotating the polarization characteristic of the probe by 90 degrees and non-contact displacement measuring means for measuring displacement of a center of a detection part of the probe, which is generated by the rotation, outputs a measurement value of the displacement or outputs the electric field information or the phase difference information corrected by the displacement measurement value, or sets a scan area offset by the displacement. By a configuration substituting the radio wave radiator by the probe, the radio wave radiator side is scanned to perform measurement in a near field.

Description

  In order to estimate the electric field strength at the reception point of radio waves radiated from a radio wave radiator of K band or higher, that is, 18 GHz or higher, that is, far-field, the present invention provides the radio wave radiator. The present invention relates to a near-field measurement apparatus having a probe for measuring the electric field distribution or phase difference of the radio wave in a relatively close region, that is, a near-field.

  When measuring a circularly polarized wave component of a radio wave having a frequency higher than microwaves of K band or higher radiated from a radio wave radiator with an NFM device (near field measuring device), conventionally, an orthogonal linearly polarized wave component, for example, a vertical component is used. (V) and the horizontal component (H) are individually measured, and the measured values are synthesized to obtain a circularly polarized wave pattern.

  An example of a conventional NFM apparatus is shown in FIG. In the measurement using this apparatus, a waveguide probe 4 having a rectangular cross section is generally used, and a surface (hereinafter referred to as a scan region) 6 on which an electric field or a phase (or a phase difference) is to be measured is placed on the waveguide. The electric field distribution and phase distribution were drawn by scanning with a probe. In this measurement, the polarization characteristics of the waveguide probe 4 are electrically or magnetically measured by using the polarization axis (or POL) positioner 3 after the one measurement. Alternatively, the scanning region is scanned by rotating it 90 ° mechanically or by repeating the rotation at each measurement point in the scanning. In particular, the polarization axis positioner is shown in FIG.

  As is well known, waveguides are typically used in a fixed state. It is usually difficult to rotate the waveguide or its polarization characteristics so as not to reduce the measurement accuracy, and by making this possible, it becomes a configuration that includes some disadvantages.

  In the conventional NFM apparatus, for example, as shown in FIG. 2B, the position of the waveguide probe at the time of measuring each component of V polarization / H polarization is shifted, and as a result, as shown in FIG. Therefore, there is a problem that the H polarization scan region and the V polarization scan region are shifted from each other, and the measured values at the same measurement point are not obtained. The influence of this deviation becomes remarkable particularly when the wavelength is short. This is because the ratio of the deviation to the wavelength is increased, and the waveguide size is reduced, and the outer wall thereof must be thinned. This is because the wavelength tends to decrease as the wavelength becomes shorter, and it is easy to bend due to carelessness of the user.

  Near-field measurement example of right-handed circularly polarized light radiated from a conical horn antenna at 94.05 GHz (wavelength is about 3.2 mm) is shown in FIGS. 7A and 7B, respectively. (H polarization) and vertical polarization component (V polarization) are shown. When measuring each, the waveguide probe is rotated as described above by the rotation of the polarization plane by the polarization axis positioner. At this time, the center of the tip section of the waveguide probe may not coincide with the center of rotation of the rotation, the normal direction of the tip section may change due to the rotation, or the curvature of the probe may change. is there.

  As described above, conventionally, for example, when the characteristic measurement of the circularly polarized antenna is performed by the NFM, the data of each polarization is acquired by changing the probe to the setting for the H polarization and the setting for the V polarization. However, the setting for each polarization is conventionally performed by rotating the polarization characteristics of the waveguide around the rotation axis with a rotation positioner that rotates the polarization plane around the probe rotation axis (that is, the polarization axis positioner). Met. For this reason, in the millimeter wave, particularly in the high frequency region of the K band or higher, as the probe position setting error becomes higher, the ratio to the wavelength becomes more prominent. In particular, errors related to the phase become significant.

  Therefore, in the present invention, the tip position of the probe is accurately measured with a simple configuration for each setting for H polarization and V polarization, and the radiation distribution or measurement region is corrected based on the measurement result. That is, the present invention proposes a near-field measuring device having a function of measuring the tip position of a probe with sufficiently high accuracy.

The near-field measuring device of the present invention is
A probe for detecting radio waves radiated from a radio wave radiator is provided, and electric field intensity information or phase difference information is included by using the radio wave radiator or the probe at a plurality of different points within a predetermined predetermined measurement region. A radio wave radiation distribution measuring device that outputs information as a detection value,
The probe or the radio wave radiator has a polarized characteristic of polarization,
Polarization characteristic rotating means capable of rotating the polarization characteristic of the probe or the radio wave radiator having a polarized characteristic by at least a quarter rotation;
Non-contact displacement measuring means capable of measuring a displacement of a center point of the probe detection unit or a center point of radiation of the radio wave radiator caused by rotation of a polarization characteristic of the probe or the radio wave radiator; Prepared,
The detection value includes a detection value A before and a detection value B after the probe or the radio wave radiator is rotated by one quarter rotation,
Output the measured value of the displacement, or
Output the electric field strength information or phase difference information corrected with the measured displacement value, or
By correcting the position of the measurement area A or the measurement area B by the displacement, a detection value in which the relative deviation between the measurement area A and the measurement area B is eliminated is output.

  The detection part of the probe is at its tip, and the probe is substantially a radiator, horn antenna, dipole antenna, or slit antenna with a rectangular or circular waveguide cut.

  In the polarization characteristic rotating means, the detection portion of the probe is located at the distal end portion thereof, and the polarization characteristic is rotated by mechanically rotating at least the distal end portion thereof.

  Further, the non-contact displacement measuring means analyzes the position of the light by detecting the imaging position of the light of the detection unit at the tip of the probe or irradiating the detection unit with a laser beam, This is an optical non-contact displacement measuring means capable of detecting the displacement of the detecting portion due to the rotation of the characteristic.

  By applying the present invention, it becomes possible to measure the electric field intensity in the near field of the radio wave radiated from the radio wave radiator of K band or higher, and the measurement data of the electric field intensity in the near field. Thus, it is possible to estimate the electric field strength at the reception point which is the far field with less error.

It is a figure which shows the example of the conventional NFM apparatus. (A) is a figure which shows a polarization axis positioner. (B) is a figure which shows that the position of the waveguide probe at the time of measuring each component of V polarization / H polarization is shifted in the conventional NFM apparatus. It is a figure which shows that a shift | offset | difference arises in a H polarization scan area | region and a V polarization scan area | region. It is a figure which shows the example of the near field measuring apparatus of this invention suitable for using in the high frequency area | region of the microwave of K band or more, ie, 18 GHz or more. It is a figure which shows the structural example for making the front-end | tip part of the waveguide probe 4 easy to see. It is an example of a measurement of the tip position of a waveguide probe using an automatic level, (a) is a diagram showing measurement of the XY plane, (b) is a diagram showing measurement of the YZ plane. It is a figure which shows the example of a measurement of the circularly polarized wave radiated | emitted from the conical horn antenna at 94.05 GHz (wavelength is about 3.2 mm). When the position of the probe is shifted between the V polarization and the H polarization, (a) shows the path difference dl at the time of synthesis in the far field of radio waves radiated from the H-pol point and the V-pol point. (B) is a figure which shows the path | route difference at the time of each polarization | polarized-light being synthesize | combined in a far field when the H polarization scan range and V polarization scan range differ. It is a figure which shows the azimuth angle and elevation angle which show the radiation | emission direction of an antenna. It is a figure which shows the example of the circular polarization pattern which measured and correct | amended it, (a) shows the pattern of the positive polarization (RHCP = clockwise circular polarization) when not correct | amending, (b) is V It is a figure which shows the result of having carried out the circular polarization synthesis | combination from this V polarization data and the said H polarization data by calculating | requiring a probe position with respect to the far field pattern data of polarization and calculating | requiring new V polarization data . In addition, regarding the cross polarization (LHCP = left-handed circular polarization), (c) shows an uncorrected pattern, and (d) shows a corrected pattern. FIG. 5 is a diagram showing a setting for measuring the characteristics of a receiving antenna. A predetermined radio wave radiator is used in place of the probe in FIG. 4, power is supplied from a transmitter to the receiving antenna, and a radio wave radiator in FIG. 4 is used. 1 is a diagram showing a configuration in which a receiver is connected to the receiving antenna. In this case, the radio wave radiator is rotated 90 degrees to change the polarization direction by 90 degrees.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

  FIG. 4 shows an example of the near-field measuring device of the present invention suitable for use in a high frequency region of K band or higher. The waveguide probe 4 having a rectangular cross-sectional shape can rotate the polarization characteristic by at least a quarter rotation by the polarization axis positioner 3. Further, a scanner is constituted by the horizontal axis driving unit 1 and the vertical axis driving unit 2, whereby the position of the polarization axis positioner 3 can be changed. As a result, the distal end portion of the waveguide probe 4 is in the scan region 6. The offset on the horizontal axis drive or the vertical axis drive can be given to the scan position and the scan position. If the background noise cannot be ignored, the near-field measuring device is installed in an anechoic chamber.

  The radio wave detected by the waveguide probe 4 is a radio wave radiated from the radio wave radiator 8 by the power supply from the transmitter 9, and the directivity center of the radio wave radiator 8 is usually at the center of the scan region 6. Directed. The radio wave detected above is sent to the receiver 7, and the data processing unit 10 compares the signal from the transmitter 9 with the signal from the receiver 7, so that the electric field strength information and phase difference information in the scan region are compared. To get. These measurements are preferably performed in an anechoic chamber, and it is desirable to provide a radio wave absorbing wall 5 on the back or floor of the scan area 6 to suppress adverse effects of reflected radio waves.

The position of the distal end portion of the waveguide probe 4 or the displacement of the position is measured by the non-contact displacement measuring means 11. This measurement value is converted into digital position data by the reader 12, and the data processing unit 10 associates the transmission signal, the reception signal and the position data with each other for the H polarization and the V polarization. Correction by the position of the tip end of the waveguide probe 4 or its displacement is possible. Further, with respect to the reader 12, the position of the waveguide probe 4 is changed using the horizontal axis driving unit 1 and the vertical axis driving unit 2, the non-contact displacement measuring means 11 detects the position mismatch and the horizontal axis driving unit 11 It is possible to substitute by reading the positions of the driving unit 1 and the vertical axis driving unit 2.
As a result, the detection value by the waveguide probe 4 includes a detection value A before the radio wave emitter is rotated by one-fourth rotation and a detection value B after the rotation. Further, when the probe is rotated as described above, the tip portion thereof is displaced, and the data processing unit 10 determines the displacement measurement value or the electric field strength information or phase difference corrected by the displacement measurement value. It is set to output information or a detection value in which the relative displacement between the measurement area A and the measurement area B is eliminated by correcting the position of the measurement area A or the measurement area B by the displacement. .

  The non-contact displacement measuring means 11 may be, for example, a telescope type well known as an automatic level, or a three-dimensional scanner type. If sufficient accuracy cannot be obtained with the telescope type or the three-dimensional scanner type, a more accurate displacement can be obtained by using a laser interferometer type displacement measuring instrument.

  Further, when the wall surface of the waveguide probe 4 is made of a thin metal foil, it is generally difficult to supplement the distal end portion of the waveguide probe 4 with the field of view of the non-contact displacement measuring means 11. Therefore, as shown in FIG. 5, a marker 22 made of a fluorescent material, a phosphorescent material, or a highly reflective material is provided on the outer wall side of the distal end portion of the waveguide probe 4 to irradiate light from the illumination device 20. . As a material used as the marker, it is naturally desirable to select a material having a small high-frequency loss in the wavelength band to be measured.

  Next, a method for obtaining circularly polarized waves from the acquired probe position deviation and the radiation distribution of V polarization / H polarization will be described.

[Measurement of probe position]
In the following, an example of measurement based on H polarization is shown. The reason why either polarization of H / V is used as a reference is to prevent mistakes.

(1) Measurement on XY plane As shown in FIG. 6A, the measurement in the XY plane is performed by, for example, looking through a scope using an automatic level, and a waveguide probe is placed at the center of the field of view of the scope. Scan the positioner to come and read the scanner position at that time. Run for both V and H polarizations and record the difference between them.

(2) Measurement of Y-Z plane The position of the H polarization is aligned with the center of the visual field of the scope of the automatic level as shown in FIG. The scanner position at that time is read. Next, the position of the probe is moved in consideration of the difference in the positions measured in (1) measurement of the XY plane with the V polarization (X and Y values match).
Next, the difference between the probe position of the V polarization probe and the crosshair position of the automatic level scope is measured.

[Electric field pattern measurement]
In the electric field distribution measurement, V polarization / H polarization is measured as usual, and a radiation distribution is obtained for each polarization. Also, distribution data of each polarization is stored. A measurement example is shown in FIG. This is a diagram showing a measurement example of circularly polarized light radiated from a conical horn antenna at 94.05 GHz (wavelength is about 3.2 mm).

The data processing proceeds as follows.
(1) The position measurement error is corrected to the V polarization data based on the stored V polarization / H polarization data.
(2) Obtain circularly polarized wave distribution using H polarization data and corrected V polarization data. Programs for this purpose are already commercially available, and the circularly polarized wave distribution can be easily obtained by using them.
(3) Check the obtained distribution data with contour display software.

[Probe position and scanner coordinate system]
The movement of the probe occurs not only in the XY plane but also in the Z-axis direction. For example, the case where the POL positioner is attached obliquely to the scanner can be considered. At that time, the difference between V and H in the Z-axis direction is measured and reflected in the correction. In this case, it can be given as an error in the Z-axis direction which is perpendicular to the scan area. This error can be examined as it is because the direction is coincident with the coordinate system.

  When the position of the probe is shifted between the V polarization and the H polarization, as shown in FIG. 8A, the nth vertical polarization component (V) with respect to the nth horizontal polarization component (H-pol) data. -Pol) Assume that data is measured by Dn away. Assuming that the radiation direction vector P is used, the difference dl of the path when the radio waves radiated from the H-pol point and the V-pol point are synthesized in the far field is the inner product of P and Dn. It is.

This is expressed as a phase difference as follows.

This phase difference can be obtained from the amount of position shift at the time of measurement (considering that the V polarization is shifted when the H polarization is used as a reference).

  Also, as shown in FIG. 8B, when the H polarization scan range and the V polarization scan range are different, it is assumed that a far field of each polarization is obtained around a certain point (for example, the origin O). For example, in the calculation with a commercially available NSI2000 measuring apparatus, the scan range is treated as the same position, and the calculation is performed assuming that the H polarization and the V polarization are emitted from the same phase center O.

  Originally, as shown in FIG. 8A, since the scan range is shifted, the distance from the center O should be different between the H polarization and the V polarization, and this must be taken into consideration. When the far-field pattern is obtained independently of the H-polarization and the V-polarization, it is necessary to treat each polarization pattern as having shifted the phase center accordingly. For example, when the relative difference between the scan areas of the H polarization and the V polarization is Da, assuming that there is an antenna for H polarization and an antenna for V polarization, as shown in FIG. The phase of the V polarization should be shifted by the distance dl. Therefore, it is necessary to correct the phase difference δ corresponding to the V polarization. Therefore, circular polarization synthesis is performed by correcting the V polarization data from the phase difference δ as follows.

  The circularly polarized waves synthesized in consideration of the above are as follows for the positive polarization and the cross polarization.

[Consideration of vector calculation]
(1) Position error vector Da
It is desirable that the measurement device first measures the H polarization, and then measures the V polarization, and the reference is also the H polarization.
Use the scanner position display function to measure the probe position.
H polarization position: x, y coordinate reading, z coordinate is zero,
V polarization position: x and y coordinate readings and z coordinates are measured separately.
To determine the difference between each component.

  In the plane scan, the position errors are all the same for each measurement point as Dn, and are as follows.

(2) Radiation direction vector P
Referring to FIG. 9, the radiation direction of the antenna is defined as follows (elevation over azimuth).
Azimuth angle: θ _Az Angle from Z axis,
Elevation angle: θ _El Angle from the XZ plane to the Y-axis direction.
Given a unit vector in the Z-axis direction and given an azimuth angle θ _Az , the vector rotates in the XZ plane and goes to the position of P ′. Therefore, the components of each P ′ are as follows: .

Further, each coordinate component when the elevation angle θ _Al is given and faces the direction P is given by the following equation.

This is a radial vector.

Examples of the measured circular polarization pattern are shown in FIGS.
The far field distribution of the polarization of each of H polarization / V polarization is obtained, and circular polarization synthesis is performed based on the far field distribution. FIG. 10A shows a pattern of positive polarization (here, RHCP = clockwise circular polarization) when correction is not performed. There are about three mountains in the elevation direction. FIG. 10 (b) shows new V polarization data obtained by correcting the probe position with respect to the far field distribution data of V polarization, and circular polarization from this V polarization data and the above H polarization data. It is the result of synthesis. There was one mountain and the radiation distribution was reasonable.
Similarly for cross-polarized waves (LHCP = left-handed circularly polarized waves), FIG. 10C shows the radiation distribution without correction, and FIG. 10D shows the radiation distribution after correction. As in the case of the positive polarization, there are many peaks without correction. However, by correcting, it becomes a single-peak characteristic and the circular polarization characteristic can be understood. Here, the contour line pattern shows a relative value, but the reference is a peak of positive polarization.

In the above description, an apparatus having a configuration in which a radio wave emitter is fixed, a probe is moved within a predetermined measurement range, and measurement relating to electric field strength and phase is performed. This is to measure the near-field characteristics at the time of radio wave radiation. Generally, since a radio wave radiator can also be used as a receiving antenna, the present invention is not set to measure the characteristics of the receiving antenna. Easy. For example, the probe shown in FIG. 4 is used as a radio wave radiator, power is supplied from a transmitter, and the radio wave radiator shown in FIG. 4 is used as a probe, and a receiver is connected to the probe. In this case, the radio wave radiator is rotated 90 degrees to change the polarization direction by 90 degrees.
In FIG. 11, the receiving antenna side is fixed, and the radio wave emitter side scans a predetermined measurement area. However, it is not always necessary to fix the probe as the receiving antenna. Obviously, the radio wave radiator may scan a predetermined measurement area. By relatively moving both of these, it is possible to reduce the absolute scan area.

  The present invention need not be limited to circularly polarized radio wave radiators as objects to be measured, but can be applied to polarized radio wave radiators such as linearly polarized waves and elliptically polarized waves. Of course, it can also be used when measuring the polarization output characteristics.

DESCRIPTION OF SYMBOLS 1 Horizontal axis drive part 2 Vertical axis drive part 3 Polarization axis positioner 4 Probe 5 Radio wave absorption wall 6 Scan area 7 Receiver 8 Radio wave emitter 9 Transmitter 10 Data processing part 11 Non-contact displacement measuring means 12 Reader 20 Illumination device 22 Markers

Claims (4)

A probe for detecting radio waves radiated from a radio wave radiator is provided, and electric field intensity information or phase difference information is included by using the radio wave radiator or the probe at a plurality of different points within a predetermined predetermined measurement region. A radio wave radiation distribution measuring device that outputs information as a detection value,
The probe or the radio wave radiator has a polarized characteristic of polarization,
Polarization characteristic rotating means capable of rotating the polarization characteristic of the probe or the radio wave radiator having a polarized characteristic by at least a quarter rotation;
Non-contact displacement measuring means capable of measuring a displacement of a center point of the probe detection unit or a center point of radiation of the radio wave radiator caused by rotation of a polarization characteristic of the probe or the radio wave radiator; Prepared,
The detection value includes a detection value A before and a detection value B after the probe or the radio wave radiator is rotated by one quarter rotation,
Output the measured value of the displacement, or
Output the electric field strength information or phase difference information corrected with the measured displacement value, or
By correcting the position of the measurement area A or the measurement area B by the amount of displacement, a detected value in which the relative deviation between the measurement area A and the measurement area B is eliminated is output. Field measuring device. 2. The near-field measurement according to claim 1, wherein the detection unit is a radiator, a horn antenna, a dipole antenna, or a slit antenna having a rectangular or circular waveguide cut off at a tip of the probe. apparatus. 2. The polarization characteristic rotating means according to claim 1, wherein the detection portion of the probe is at the tip thereof, and the polarization property is rotated by mechanically rotating at least the tip. 2. The near-field measuring device according to 2. The non-contact displacement measuring means performs the position analysis by analyzing the imaging position of the light of the detector at the tip of the probe or by irradiating the detector with a laser beam, and The near-field measuring device according to claim 1, wherein the near-field measuring device is an optical non-contact displacement measuring unit capable of detecting a displacement of the detecting unit due to rotation of the sensor.