JP2006208019A - Electromagnetic wave coupling apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for accurately measuring spurious radiation, covering a very wide frequency band. <P>SOLUTION: A stage for putting an object to be measured, a wide band progressive wave antenna pair facing X, Y, Z axis directions from the stage in the center, a compositor for combining and adding signals from the antenna pair, and a means for reading the added power spectrum are provided. By constituting the stage connected with the compositor so that the facing antenna pair can be added with the same phase to be a movable stage or that maximum power value can be calculated by varying the phase with a variable phase shifter, the maximum value in each frequency is recorded at all times and the fundamentals waves, higher harmonic waves or other spurious components can be measured and recorded. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electromagnetic wave coupling device capable of accurately measuring a target carrier component emitted from a radio wave device such as a VHF band or a UHF band (for example, a mobile phone) and an unnecessary radiation spurious component such as a high frequency over a wide band.

  Recent mobile phones are not only making calls, but also being provided with image display and Internet functions, and many other uses have been devised, and are making remarkable progress. Other wireless information terminal devices will also be developed as wireless LAN broadband, data links between information devices in offices, homes, automobiles, etc. In the near future, small information devices that use various electromagnetic waves will be developed in the IT era. is there.

  From these devices, in addition to the fundamental frequency component for communication purposes, unnecessary signal components called spurious components are also radiated, which may cause interference. Therefore, there is a strong demand to manufacture devices that accurately grasp the actual state of these emissions and take appropriate measures. However, since these spurious radiations extend over a very wide frequency band, it is difficult to obtain accurate measurement means.

  (1) Spurious components can be measured by measuring each frequency component of electromagnetic waves flying toward a device under test at an electromagnetic wave measurement site such as an anechoic chamber. However, in order to measure each XYZ polarization component, it is necessary to repeat the measurement by changing the installation of the object to be measured each time. It can happen that the state of the object to be measured changes.

  (2) In a small space such as a factory or office, there is a method of putting an object to be measured in a kind of transmission line shape called TEM-CELL. Since TEM-CELL is compatible with unidirectional polarization, it has only a single polarization. Therefore, it is necessary to re-install the device under test for each axial polarization. In addition, since the object to be measured is inserted between the inner conductor of the large coaxial line and the outer skin, there is a problem that the coupling coefficient changes depending on the position where the object to be measured enters, which becomes more problematic in a wide frequency range. In addition, since the phase center of the object to be measured changes variously at the spurious frequency, it is necessary to find the installation position for each spurious frequency, but this is almost impossible, so it is not possible to measure very accurately. .

  The amount of coupling in the method (2) increases as it approaches the inner conductor, and decreases as it goes to the outer skin side. In short, it is a method of limiting the installation location and reading the value based on the convention, so it becomes difficult to place it in the specified position, especially as the object to be measured becomes larger in the device, and the measurement becomes increasingly inaccurate. Become.

  Japanese Patent Application No. 5-72095 proposes a device for measuring radiation power and radiation pattern with an antenna measurement device. This is basically intended to save the measurement time by surrounding the relationship (1) with a large number of antennas in a circle and electrically sweeping the relationship.

  As in the above (1), the measurement is performed by changing the installation of the object to be measured for each polarized wave, but when measuring harmonic spurious with this device, the power of each frequency component is sequentially obtained, Since the relationship between the fundamental wave component and the spurious radiation intensity ratio is obtained by comparing the data after the measurement operation is completed, it has the same drawback as the above (1).

In order to solve such a problem, the present applicant arranges traveling wave antennas having the same characteristics on the circumference of the object to be measured so that the transmission transfer amount between the antenna elements from each center point becomes the same. A method of adjusting, that is, acquiring and synthesizing radio waves radiated from a transmission source in the same phase on the circumference has been developed, and a patent has been obtained (see Patent Document 1).
Patent No. 3436669 In this case, the device focuses only on a single polarized wave, and the polarization components of the XYZ three axes are separated separately, and over a very wide band including several harmonics in all axes and all frequency ranges. It is difficult to construct a relationship in which the measurement antenna is located equidistant from the center point.

  Although the above-mentioned patent has realized a method for quickly obtaining radiated power at a predetermined frequency and polarization, in digital communication with broadband as in the past, not only the carrier frequency for transmission but also high-speed digital inside Since the processing signal or the like is operating, there is a problem of radiating unnecessary electromagnetic wave components in a very wide band.

  In addition, handy information devices that are becoming smaller in size such as plastic housings tend to have insufficient measures such as shielding as compared to conventional full-fledged communication devices. Therefore, the emission of harmonic components of carrier signals cannot be ignored.

  In order to accurately measure these very wide frequency band spurious signal emissions, the above-described conventional method requires a great deal of time and is almost impossible, and therefore, an appropriate measurement method is desired.

  The present invention has been made paying attention to such points, and an object thereof is to provide a method for accurately measuring spurious radiation over a very wide frequency band.

  The configuration of the present invention that meets the above-described object includes a movable table on which a device under test (electromagnetic wave emitter) is placed, a broadband traveling wave antenna pair that faces the XYZ axis around the table, and the antenna pair. And a means for reading the added power spectrum, and the opposed antenna pairs are connected to the combiner so that they can be added in the same phase and move the stage. The maximum value at each frequency is always recorded by setting it as a platform to obtain, or by changing the phase with a variable phase shifter, so that the maximum value at each frequency is always recorded, and the fundamental, harmonic, or other spurious components Can be recorded. The antenna pair is an antenna having the same polarization.

  It is preferable that the antenna pairs are arranged to face each other at equal distances in the XYZ axial directions with the platform as a center.

  The broadband traveling wave antenna pair may be a traveling wave antenna having a bandwidth that is three times or more the fundamental frequency.

  The means for reading the added power spectrum is preferably a swept power measuring instrument such as a spectrum analyzer having a peak value holding function.

  The platform on which the object to be measured is placed is preferably provided with a mechanism that can be swept so that the center of the electromagnetic wave radiation source to be measured passes through an intermediate point between the opposing antennas. . If comprised in this way, the stand which mounts a to-be-measured object can be moved, sweeping in an arbitrary frequency range.

  Preferably, the opposing antenna pairs are connected to the combiner with equal phase amounts so that they are added in the same phase.

  Furthermore, it is preferable that a shield box composed of an electromagnetic wave absorbing material and a metal shielding plate is formed outside the antenna pair. By doing in this way, the electromagnetic wave radiated | emitted from a to-be-measured object is not reflected, but it can prevent that this device antenna pair makes an image image on a case metal surface.

According to the present invention, it is possible to measure and analyze a broadband spurious component that has conventionally been difficult to measure accurately even in a long time, in a short space and in a short time. In addition to taking measures to stop the generation of disturbing waves that cause unnecessary disruption in advance, it contributes to the orderly development of the information-oriented society, such as the increasing interference between various radio wave devices and the prevention of interference with electronic devices such as cardiac pacemakers. It is extremely large.

Next, an embodiment of the present invention will be described.
In order to achieve the object of the present invention of the first to sixth aspects, there are technical problems to be solved such as (1) to (3) below.

(1) The ability to detect polarization components over three axes This is because not only the so-called main antenna for communication but also electromagnetic radiation from various places, the polarization cannot be determined in advance. It is an indispensable condition. Furthermore, this condition is necessary because components that include high frequencies other than the carrier frequency even when radiating from the main antenna generate various modes on the main antenna and are not guaranteed to be polarized in the same direction as the fundamental wave. It is.

(2) A wide frequency range that is at least 3 times higher than the fundamental frequency can be observed and measured reliably. Generally, the large components of spurious signals are second and third harmonics. It is preferable to measure. Furthermore, since the above-mentioned digital equipment emits a large amount of clock signals and their harmonics unrelated to the carrier, it is preferable to reliably observe and measure the frequency range up to at least three times the fundamental wave. This is a necessary condition for fully exhibiting the effects of the present invention.

(3) The above-mentioned components can be measured The radio wave radiated into the space is attenuated by the propagation distance. In the vicinity of the emission, the third power term, the second power term, and the first power term are mixed. With a certain distance and antenna system, it is possible to create a relationship in which the same first power term as the far field is dominant. However, there is no change in the transmission amount (coupling amount) when the distance changes. Therefore, in order to sufficiently exhibit the effects of the present invention, a method for obtaining the value of each frequency component with good reproducibility is required even if the positional relationship between the object to be measured and the measurement antenna changes.

  (4) Furthermore, if the transmission amount can be calibrated for each axis and each frequency, accurate measurement becomes possible, and the effects of the present invention are more fully exhibited.

  First, the above (1) can be realized by the following means.

  Centering on the object to be measured, traveling wave antennas of linear polarization, preferably parallel to the X, Y, and Z axes at a distance equal to each other in three directions, are arranged to face each other. Then, the antennas of the same polarization facing each other are connected from the center with a cable having the same phase amount and a signal combiner. That is, an XYZ polarized antenna is formed on the object to be measured.

  The above (2) can be realized by designing a traveling wave antenna having a bandwidth that is at least three times the fundamental frequency as a broadband antenna. This can be formed by existing antenna theory. For example, in the embodiment, an antenna covering 700 MHz to 12 GHz was prototyped.

  Realization of the stable reproducibility of (3) above requires that a table on which an electromagnetic wave emitter (transmitter) is installed while sweeping a radiated power measuring device (for example, a spectrum analyzer) connected to a measurement antenna in an arbitrary frequency range. Since the spurious signal radiated from the transmitter under measurement passes through the center point at each frequency point by moving or changing the phase with a variable phase shifter, the maximum value of each frequency component Is recorded, and measurement with good reproducibility becomes possible.

  The true center point of the opposed antenna pair is the point where the phase to both outer antennas is equal, so when the amount of transmission between the antennas placed just in between the combined output end of the opposed antenna pair is the same phase Doubled and maximized. In particular, in the harmonic region with a short wavelength, the phase difference also changes abruptly and the amount of transmission also decreases abruptly due to a slight change in position, so that the center point can be more discriminated.

  Now, a mechanism is provided that can variably move the base installed on the electromagnetic wave emitter (transmitter), which is the object to be measured, in the direction of both outer antennas that are arranged so as to sandwich it, and the combined output of both antennas is measured. When connected to a measuring device such as a tram analyzer, the measuring device uses a max hold mode in which the maximum value is held, so that the maximum value of each frequency component can be viewed. Max mode is a mode in which measured data is recorded in digital memory and compared with data at the same address while constantly recording large values. In the case of a spectrum analyzer, the maximum value is obtained at each position corresponding to the horizontal axis frequency. This is because the record is kept.

  Since the device under test is moved while sweeping in an arbitrary frequency range, the maximum value of each frequency component is recorded at each frequency point and always passes through the above-mentioned “center point”, so the reproducibility is extremely good. Measurement is possible.

  In order for this relationship to hold in the three directions of XYZ, a mechanism that can move in the three-axis directions is provided. If the spectrum analyzer has three input terminals, the frequency characteristics of each axis of XYZ can be obtained at once. Even with one input, the data of the three axes can be obtained separately by switching sequentially, transferred to a personal computer (hereinafter referred to as a PC), etc., and overwritten on the same screen, for example, can be easily viewed directly.

  The calibration method (4) can be easily and accurately calibrated by the following procedure.

  Since the UHF / VHF band has a reasonable wavelength, a λ / 2 dipole antenna is used. This dipole antenna is placed in the center of the above-mentioned counter antenna, and the transmission amount at the combiner output end of this dipole antenna and both outer antennas is measured. At this time, the maximum value is obtained by moving the dipole antenna. This is the amount of transmission when a standard dipole antenna is placed at the midpoint, and this is the standard coupling coefficient. Since the theoretical gain of the half-wave dipole antenna is always 1.64 (2.1 db) regardless of the frequency, this value is used as a reference. In addition, since the manufactured dipole antenna is not possible, it is necessary to measure the gain deviation from the theoretical value (calibration work). For this calibration, a distance between two antennas is accurately determined and calibrated from a theoretical attenuation amount, or a three-antenna comparison method (US NIST method) is known.

  Next, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, antennas (antenna pairs) having the same polarization are placed facing each other with the object to be measured interposed therebetween, and the antenna pairs are connected by a combiner. At this time, the phase from the antenna output end to the combiner is matched.

  If an electromagnetic wave radiation source (object to be measured) having the same polarization is placed in the middle of the antenna pair, power is induced in both the left and right antennas. If radiated from the true midpoint, in-phase power is induced in the left and right antenna pairs and added twice by the combiner. Since the maximum value is indicated at this time, reproducibility and accuracy can be ensured by searching for the maximum value. In addition, if it deviates from an intermediate point, a synthetic | combination output will be reduced by the phase difference of the induced electric power of a left-right antenna pair.

  FIG. 2 shows an embodiment of the present invention. If the polarization of the left and right antenna pairs in FIG. 1 is called Y-axis polarization, X-axis polarization is formed above and below the object to be measured, and XYZ 3-axis polarization is shown. The example which comprised the polarization is shown. Z-axis polarization can be created by combining antenna elements (orthogonal elements) perpendicular to the left / right or upper / lower antenna pairs. With this configuration, two of the octahedral boxes can be opened, and the object to be measured can be taken in and out.

  A shield case made of a radio wave absorber and metal is formed on the outside of the XYZ triaxial antenna pair so as to absorb a reflection component so as not to cause an error and to prevent an external radio wave from entering by the metal shield case.

  FIG. 3 shows another embodiment of the present invention, in which the object to be measured is placed so that the phase center of the electromagnetic wave radiation of the object to be measured always passes through the true middle point of the XYZ triaxial antenna pair. An example in which a movable device that moves in the XYZ directions is provided on the table will be described.

  Outputs from each axis antenna pair are added by a synthesizer and connected to a measuring instrument. A spectrum analyzer is usually used as a measuring instrument. At this time, a maximum hold function for recording the maximum value of the measurement signal intensity value is used. The maximum value when passing through the intermediate point between each antenna pair is recorded and held by the movable device.

  Normally, a spectrum analyzer sweeps the frequency axis over time. By making the sweep cycle asynchronous with the above-described sweep cycle of the movable device, the maximum value at each frequency point is recorded over the entire measurement frequency if a certain amount of time is taken.

  This movement is not limited to a linear direction parallel to the XYZ axes, and it may be more efficient to rotate a mobile phone or the like. The spectrum analyzer to be used is optimal if it has a three-input function (multi-channel function), but an old one-channel type may be used.

  While switching the combiner output of each of the XYZ antenna pairs, the output for each channel is subjected to max hold measurement, and the data is transmitted to a PC or the like.

  The PC can display the radiation power value for each frequency of the radiation source by plotting and displaying the data corresponding to each channel or displaying the maximum value while comparing the data.

  FIG. 4 shows another embodiment of the present invention, which is configured so that the maximum power value can be found by changing the phase with a variable phase shifter instead of moving the DUT (device under test) installation base. An example is shown. In FIG. 4, only a pair of antenna pairs is shown, but the antenna pairs are arranged opposite to each other in the XYZ axis direction as in the above embodiment.

  Since the maximum power value is the point where the phase of the opposing antenna pair becomes equal, instead of moving the stage, the phase of the opposing antenna pair is changed to find the point where the phase becomes equal (the maximum power value) However, similar results can be obtained.

  In the above-described embodiment, the control of the opposite phase shifter, the control of the power meter, and the data plotting are performed by software.

(Transmission power calibration)
The gain characteristics of the antenna pair are not constant. Since so-called frequency characteristics exist, calibration is required over each frequency.

  Calibration by the method of the present invention can be performed very simply as follows.

  Insert a standard dipole antenna at the “midpoint” instead of the DUT. At this time, it is set according to the polarization of each axis of XYZ. It is convenient to use a network analyzer as a measuring instrument to directly view and measure the amount of propagation between antennas.

  If the value that is movable and has the smallest transmission loss is read in the same manner as described above, it becomes the reference coupling amount at the standard dipole, which is the so-called coupling coefficient of this apparatus. This is because the gain of the half-wave dipole antenna is constant regardless of the frequency, and the distance between the antennas is also constant, so that power directly proportional to the radiated power value is induced in the antenna and can be read by the measuring instrument. .

  For more precise measurement, the half-wave dipole antenna may be calibrated separately. This is because the theoretical gain value of the half-wave dipole antenna is 1.64, and is obtained by comparing with the theoretical value from the transmission amount between the antennas set at the accurately measured distance.

  In addition, the traveling wave broadband antenna to be used can be manufactured very gently. Therefore, if the half-wavelength dipole antenna is calibrated at a certain frequency interval, it can be used as a continuous frequency characteristic while being sufficiently supplemented.

It is a principle figure which shows the Example of this invention. It is a principle figure which shows the other Example of this invention. It is a principle figure which shows the other Example of this invention. It is a principle figure which shows the other Example of this invention.

Claims (7)

A table on which the object to be measured is placed; a broadband traveling wave antenna pair opposed to each other in the X, Y, and Z axis directions around the table; a combiner that combines and adds signals from the antenna pair; and a means for reading the added power spectrum The antenna pair is connected to the combiner so that the opposite antenna pairs can be added in the same phase and the stage can be moved, or the phase can be changed by a variable phase shifter, so that the maximum power can be obtained. An electromagnetic wave coupling device configured to obtain a value. 2. The electromagnetic wave coupling device according to claim 1, wherein the antenna pairs are arranged to face each other at equal distances in the XYZ axial directions with the base as a center. The electromagnetic wave coupling device according to claim 1 or 2, wherein the broadband traveling wave antenna pair is a traveling wave antenna having a bandwidth of three times or more of a fundamental frequency. The electromagnetic wave coupling device according to any one of claims 1 to 3, wherein the means for reading the added power spectrum is a sweep type power measuring instrument having a peak value holding function. The table on which the object to be measured is placed is provided with a sweeping movable mechanism for allowing the center of the object to be measured electromagnetic wave radiation to pass through an intermediate point between the opposing antennas. The electromagnetic wave coupling device described in 1. The electromagnetic wave coupling device according to claim 1, wherein the opposing antenna pairs are connected to the combiner with equal phase amounts so that the antenna pairs are added in the same phase. The electromagnetic wave coupling device according to any one of claims 1 to 6, wherein a shield box composed of an electromagnetic wave absorbing material and a metal shielding plate is formed outside the antenna pair.

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