WO2003098238A1

WO2003098238A1 - Local sar measurement device and method

Info

Publication number: WO2003098238A1
Application number: PCT/JP2003/005848
Authority: WO
Inventors: Yoshio Koyanagi; Yutaka Saito; Koichi Ogawa; Shoichi Kajiwara; Akihiro Ozaki; Yoshitaka Asayama
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2002-05-17
Filing date: 2003-05-09
Publication date: 2003-11-27
Also published as: AU2003235922A1; JP4010869B2; CZ20041124A3; CN100360946C; CN1668930A; JP2003332999A

Abstract

A local SAR measurement device capable of estimating a small-size radio device local SAR on a production line with a high accuracy within a short time. The local SAR measurement device includes a plurality of electromagnetic probes (1) for receiving transmission power from a mobile telephone antenna (12) extending from a mobile telephone main body (11) in Fresnels zone, a combining device for combining the reception powers (2), and a signal processor (3) for estimating a local SAR from the combined reception power. A plurality of electromagnetic probes (1) are used to measure the reception powers of a reference mobile telephone whose local SAR value is known by a precision measurement and a mobile telephone to be measured, so as to estimate the SAR value of the mobile telephone to be measured by utilizing that the SAR value is in proportional relationship with the reception power. Thus, it is possible to measure and evaluate SAR values of a plenty of mobile telephones with a high accuracy in a short time.

Description

Description Local SAR measurement device and method <Technical field>

The present invention relates to a local SAR measuring device and method for measuring local SAR in a small wireless device such as a mobile phone.

In recent years, with the rapid increase in demand for portable wireless devices such as mobile phones, there has been a worldwide movement to regulate the amount of electromagnetic waves radiated to the human body from the viewpoint of electromagnetic wave safety to living bodies. In particular, mobile phones use an antenna that is a source of electromagnetic waves in close proximity to the user's head.Therefore, there are concerns about harmful effects on the human body. I have. Along with this, even in the mobile phone production process, it is necessary to control the local SAR value of the product before shipping it, and there is a need for a measuring means for inspecting the local SAR quickly and accurately.

SAR (Specific Absorption Rate) is the absorbed power per unit weight when the human body is exposed to an electromagnetic field, such as the "Guideline for Protection of the Human Body Using Radio Waves" in the report of the Telecommunications Technology Council of the former Ministry of Posts and Telecommunications. In the same report, the "Measurement of Specific Absorption Rate for Mobile Phone Terminals Used on the Human Temporal Head" in the same report, the human body simulated the shape-dimensions and electrical characteristics of the head tissue. It has been shown to use a human body (phantom) to experimentally estimate the SAR that may occur in the human body.

In general, local SAR assuming electromagnetic wave absorption in the head of a portable wireless device user is experimentally performed using a phantom that simulates the shape and dimensions of the head and the electrical characteristics of the head tissue to the human body. Presumed. Here, the distribution of the electric field intensity excited inside the phantom with the portable wireless device approached is measured using an electric field probe, and the SAR value is calculated from the measured value by the following equation (1).

SAR = aE p [W / kg] -d) Here, and is the conductivity of the phantom, and / 0 is the density of human body tissue.

As a simple method for estimating the SAR, a method has been proposed in which the local SAR is experimentally obtained from the magnetic field strength H on the phantom surface (see, for example, N. Kuster and Q. Balzano, "Energy absorption mechanism by biological bodies in the near field of dipole ant-ennas above 300MHz ", IEEE Trans. Ve. Tech., vol. 41, no. l, pp. 17-23, Feb. 1992, etc.). According to this method, it has been confirmed that the following relational expression (2) holds for the distribution of local SAR generated on the human body surface.

SAR «H ² [A ² / m ² ]… The electric field strength E generated in the phantom or the magnetic field strength H on the phantom surface varies depending on the transmission output of the portable radio, the shape of the antenna, the positional relationship with the phantom, etc. Therefore, local SAR evaluation requires measurement of electric field intensity distribution or magnetic field intensity distribution using a phantom.

Conventionally, as a local SAR measuring device, for example, as shown in FIG. 7, a portable wireless device configured to include an electric field probe 62, a probe scanning device 63, and a phantom 64, and held on a holder 65 A device of the internal electric field detection type for measuring 61 is known. According to this device, it is possible to measure the local SAR with the highest accuracy.

As another conventional example, for example, as shown in FIG. 8, without using a phantom, an electric field probe 72 was fixed near a portion where the maximum value of local SAR occurs, and held on a holder 75. A local electric field detection type local SAR measurement device that measures a nearby electromagnetic field in free space radiated from a portable wireless device 71 is known. This device has a simple structure and does not perform probe scanning, so it can measure in a short time and is suitable for introduction into mass production.

In addition, for example, in Japanese Patent No. 2773671 and Japanese Patent No. 2710103, among the electromagnetic fields radiated from an antenna, a magnetic field reflected on a phantom surface is detected. A configuration of a near magnetic field detection type is disclosed. In this configuration, the magnetic field distribution is measured with high accuracy by moving and rotating the electromagnetic probe, and the local SAR is estimated from the measured magnetic field distribution. According to this, a relatively simple configuration It is possible to estimate the local SAR with.

Japanese Patent Application Laid-Open No. 11-133,799 discloses that a plurality of traveling wave antennas are arranged in a shield box in which a radio wave absorber is arranged on the inner wall, and the electromagnetic fields collected by the antenna group are phase-synthesized. An example of an electromagnetic wave coupling device (an electromagnetic wave coupling method) including a synthesizer and a unit for reading the added electromagnetic field as radiated power is disclosed. With this electromagnetic wave coupling type device, it is possible to stably measure the electromagnetic wave radiated from the portable wireless device antenna, which is the device under test, in the production process.

However, in the above-described conventional local SAR measuring devices of the internal electric field detection type, the near electric field detection type, and the near magnetic field detection type, the probe means is disposed very close to the antenna because of the need to measure the local SAR value of the phantom. Therefore, there is a problem that measurement data tends to vary depending on the position and placement of the portable wireless device to be measured or the position and orientation of the antenna.

Here, a description will be given of factors that are likely to cause variations in the measurement data in the SAR measurement in the extremely near field. FIG. 9 is a diagram illustrating an electromagnetic field component radiated from a small dipole antenna, which is the most basic unit of the antenna. When the origin of the wave source of the small dipole antenna is the origin, the electromagnetic field at the point C at a distance R away is expressed by the following equations (3) to (7). lie -jkR

…)… (

-(Five)

0 ー (6) a

Θ…)

Here, human is the wavelength, k is the wave number, I is the current of the small dipole antenna, L is the length of the small dipole antenna, £ is the permittivity of the propagation space, and / is the permeability of the propagation space. According to the above equation, the electromagnetic field radiated from the antenna becomes dominant in the component (radiated electromagnetic field) that is inversely proportional to the distance R as the distance from the antenna increases, but the square of the distance is small where the distance R is small. The term that is inversely proportional to (the induced electromagnetic field) and the term that is inversely proportional to the cube (the quasi-electrostatic field) become dominant. For this reason, in general, when dealing with electromagnetic fields, the region where the quasi-electrostatic field component is dominant near about / 100 is the near-field, and the radiated electromagnetic field component is farther than about 5 in. The dominant region is called the far field, and the region between them is called the Fresnel region, and these regions are distinguished.

In other words, the quasi-electrostatic field component, which is inversely proportional to the cube of the distance, is dominant in the near-field near the antenna, which is less than approximately / 100. There is a problem that a large difference in relative position results in a large error in the electromagnetic field. At the frequency of the 800 MHz band that is commonly used in mobile phone systems, input / 100 corresponds to about 0.4 cm. In the local SAR measuring device of the internal electric field detection type in FIG. 7, the near electric field detection type in FIG. 8, or the near magnetic field detection type, the local SAR is measured by arranging probe means in such an extremely near field. This is because the body and antenna of the portable wireless device in actual use are used very close to the human body, so the surface of the phantom and the electromagnetic field source must be evaluated very close. That's why. In addition, the electromagnetic field radiated from the antenna generates an induced current on the surface of the phantom, and the current generates a secondary electric field inside the phantom.To measure this, measure the electromagnetic field near the surface of the phantom. Therefore, measurement in the near-field is performed.

In the internal electric field detection-type device shown in Fig. 7, in order to reduce measurement errors due to position accuracy, the position accuracy is maintained by a probe scanning device using an industrial robot, etc., and a plurality of areas near the local SAR are maximized. The scanning accuracy is improved by scanning each part. However, this configuration is not suitable for use in a mass production process because the longer the number of measurement points is increased to improve the measurement accuracy, the longer the measurement time becomes.

In the near-field detecting device shown in FIG. 8 and the near-field detecting device described in Japanese Patent No. 2773661 and Japanese Patent No. 2791013, there is usually only one location. Measurement, the measurement time can be shortened, but there are variations in position and radiation from the antenna. There is a problem that an error occurs in the measurement result due to a minute variation of the pattern, and it is difficult to maintain the measurement accuracy.

The electromagnetic wave coupling type device described in Japanese Patent Application Laid-Open No. H11-133709 measures an electromagnetic field in a far field slightly away from an antenna to be measured. It is difficult to correspond to the measurement.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a local radio device capable of estimating a local SAR in a short time and with high accuracy on a production line of a small wireless device such as a mobile phone. An object of the present invention is to provide a SAR measuring device and method. <Disclosure of Invention>

The local SAR measurement device of the present invention includes a plurality of electromagnetic probes for measuring electromagnetic field levels in a Fresnel region of an electromagnetic wave radiated from a wireless device, and processes the electromagnetic field level obtained by the electromagnetic probe to obtain a local SAR value. A signal processing unit for calculating; and a position adjusting means for adjusting a relative positional relationship between the electromagnetic probe and the wireless device, wherein the electromagnetic probe measures a reference wireless device whose local SAR value is known in advance. The electromagnetic field level of each of the target wireless devices is measured, and the signal processor uses the fact that the SAR value is proportional to the electromagnetic field level to obtain the local SAR value of the reference wireless device. It is characterized by estimating and obtaining the local SAR value of the wireless device to be measured.

According to the above configuration, the electromagnetic field level is measured in a Fresnel area farther from the near-field near the antenna of the wireless device, and the local SAR value is calculated by calculating a proportional relationship with a reference wireless device having a known local SAR value. By estimating, it becomes possible to estimate and find the local SAR value of the wireless device to be measured in a short time and with high accuracy on a production line that manufactures small portable wireless devices such as mobile phones. . For this reason, the measurement of the local SAR value can be performed on a production line in a short time even for a large number of wireless devices.

Further, the position adjustment means moves at least one of the electromagnetic probe and the wireless device in accordance with an electromagnetic field radiation pattern from the wireless device to adjust a relative positional relationship between the two. According to the above configuration, the measurement position of the electromagnetic field level can be adjusted to an optimum position according to the radiation pattern of the electromagnetic field radiated from the wireless device, and high-precision measurement can be realized.

Further, when there are a plurality of electromagnetic field radiation patterns from the wireless device according to the transmission frequency, the position adjusting means moves at least one of the electromagnetic probe and the wireless device according to the transmission frequency, and moves both the electromagnetic probe and the wireless device. The feature is to change the relative positional relationship.

According to the above configuration, in the measurement of a wireless device having a plurality of operating frequency bands, the measurement position of the electromagnetic field level can be adjusted to an optimum position according to the electromagnetic field radiation pattern that differs depending on the transmission frequency. High-precision measurement can be realized in the frequency band.

The local SAR measurement method of the present invention includes a step of measuring an electromagnetic field level of a reference wireless device in which a local SAR value is divided in advance in a Fresnel region of an electromagnetic wave radiated from the wireless device; Measuring the electromagnetic field level in the Fresnel region of the electromagnetic wave radiated from the wireless device, and using the fact that the SAR value is proportional to the electromagnetic field level based on the measured electromagnetic field level. And estimating the local SAI direct of the wireless device to be measured from the local SAR value of the reference wireless device.

According to the above procedure, it is possible to estimate and obtain the local SAR value of a wireless device to be measured in a short time and with high accuracy on a production line for manufacturing a small portable wireless device such as a mobile phone. Become.

Further, when a plurality of electromagnetic field radiation patterns from the wireless device are present in accordance with the transmission frequency, at least one of the electromagnetic probe for measuring the electromagnetic field level in accordance with the transmission frequency and the wireless device are moved and both are moved. The method further comprises the step of changing the relative positional relationship between the two.

According to the above procedure, it is possible to adjust the measurement position of the electromagnetic field level to the optimal position according to the electromagnetic field radiation pattern that differs depending on the transmission frequency in the measurement of a wireless device with multiple operating frequency bands And high-accuracy measurement can be realized in each frequency band. <Brief description of drawings>

FIG. 1 is a configuration explanatory diagram showing a configuration of a local SAR measurement device according to an embodiment of the present invention,

Fig. 2 is a conceptual diagram showing the state of the power supplied from the wireless circuit of the mobile phone to the antenna.

FIG. 3 is a flowchart showing a procedure for estimating a local SAR of a measured mobile phone using the local SAR measuring apparatus of the present embodiment,

Fig. 4 is an explanatory diagram showing the relationship between the position of the electromagnetic probe and the radiation directivity of the electromagnetic wave. Fig. 5 shows the measurement using the local SAR measurement device of this embodiment at the position in the maximum direction of the electromagnetic field radiation pattern. FIG. 4 is a characteristic diagram showing correlation data between received power and local SAR in the case where

Fig. 6 is a characteristic diagram showing the correlation data between the received power and the local SAR when the local SAR measurement device of this embodiment is measured at a position shifted by 60 mm from the position in the maximum direction of the electromagnetic field radiation pattern. ,

FIG. 7 is an explanatory diagram showing a configuration of a conventional SAR measuring device of an internal electric field detection type. FIG. 8 is an explanatory diagram showing a configuration of a conventional SAR measuring device of a near electric field detection type. FIG. 4 is an explanatory diagram showing an electromagnetic field component radiated from a small dipole antenna.

In addition, the code | symbol in a figure, 1 is an electromagnetic probe, 2 is a synthesizer, 3 is a signal processing part, 11 is a mobile telephone main body, 12 is a mobile telephone antenna, 13 is a radio circuit, 14, 14a, 14b is The electromagnetic field radiation pattern, 15 is a probe moving section.

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

In the present embodiment, an example of the configuration and operation of a local SAR measurement device that estimates local SAR based on measurement of received power near an antenna in a mobile phone production line is described as a device for measuring local SAR in a small wireless device. Show.

First, an outline of the local SAR measurement method in the present embodiment will be described. In the case of mass production of products of the same standard, such as in the production process of mobile phones,

If the local SAR value can be ascertained for one mobile phone, it is possible to estimate the local SAR value of other products by ascertaining the cause of the variation and making a relative comparison. Therefore, first, the causes of production variation of mobile phones will be described with reference to FIG.

FIG. 2 is a conceptual diagram showing a state of power supplied from a wireless circuit of a mobile phone to an antenna, and includes an antenna element 91, a matching circuit 92, and a transmitter 93. It is assumed that the equivalent circuit of the antenna includes a matching circuit 92 and is excited by the power supply Vg of the internal impedance Z g of the transmitter 93. Assuming that the input impedance Z in viewed from the input terminal of the antenna element 91 is conjugate-matched with the internal impedance Z g of the power supply, Z in = Z g * holds. Here, (*) represents a complex conjugate.

The input power Pin applied to the antenna element 91 in this state is expressed by the following equation (8).

Here, I1 is a current flowing through the antenna element 91, and is represented by Il = Vg / (Zg + Zin).

Also, since the input power to the antenna is all supplied from the power supply Vg, it is expressed by the following equations (9) and (10).

| 2.

P ”, ^m p _av .s…)

2 +

Here, Re (X) represents the real part of X, and Pin represents the available power of the power supply. S represents the ratio between the power supplied to the antenna and the available power of the power supply, and S = 1 in the conjugate matching state. Also, the radiated power Pr from the antenna to the space is expressed by the following equation (11).

In the above equation, Pa is the power loss caused by the high-frequency resistance of the metal wire constituting the antenna element 91, Pc is the power loss caused by the loss resistance rc of the matching circuit, Pm is the power loss due to impedance mismatch, Pm = (1 -S) Pav. From these equations, the following equation (12) is derived.

When considering the factors of product variation in the production process, Pc and Pa can be considered as slight variations in parts. For this reason, it is considered that the factors that dominate the production variation are the deviation of the available power of the power source caused by the component variation in the transmitter and the adjustment variation. Therefore, it is derived that there is a relationship between the radiated power Pr into the antenna space and the current I1 on the antenna element as expressed by the following equation (13).

The current I 1 on the antenna element generates a magnetic field H near it, and the relationship is H∞I according to Ampere's law. Here, as long as the structure of the antenna element and the current distribution shape do not change, the shape of the magnetic field distribution generated in the vicinity does not change. From this, the following equation (14) is derived.

From the above equations (7) and (14), the following equation (15) is obtained.

SAR «P _r - (15) that is, under conditions where the structure and the current distribution shape of the antenna elementary Bok does not change, If the radiated power Pr is managed, local SAR variations can be managed. The radiated power Pr is obtained by the total cubic integration of the radiation directivity of the far field, but measuring the far field in the actual production process requires a large space occupied by the measuring device, which is not practical. Therefore, a large number of electromagnetic probes may be arranged in a Fresnel region where measurement accuracy is more easily ensured than in the extremely near field, and a part of the radiated power Pr may be received.

In order for the reception level P x of the electromagnetic probe to have a high correlation with the radiated power Pr, as shown in the electromagnetic wave coupling device in Japanese Patent Laid-Open Publication No. It is effective to dispose a plurality of Ps and combine the power of each electromagnetic probe. However, in order to measure with higher accuracy, unless the electromagnetic probe is arranged in a direction that maximizes the radiated power as much as possible, a high correlation between the reception level PX and the radiated power Pr cannot be secured, and the local SAR It is not possible to achieve high-accuracy measurement that can manage

As a result of intensive studies in view of the above points, the inventor has found that when measuring local SAR in a small wireless device such as a mobile phone, it is possible to measure the electromagnetic field level with relatively high accuracy rather than in the very near field. We devised to measure the electromagnetic field level in a certain Fresnel region and to arrange the electromagnetic probe in the maximum direction of the radiated power. This has made it possible to realize a local SAR measurement device that can estimate the local SAR in a short time and with high accuracy so that it can be applied on a production line.

According to the present invention, there are provided two or more electromagnetic probes, a means for synthesizing the measurement levels from each of the electromagnetic probes and reading them as an electromagnetic field level, and the relative position between the electromagnetic probe and the wireless device to be measured. By providing means for changing the positional relationship, it is possible to measure the received power level in the direction of the maximum radiated power, and the received power level of the reference wireless device whose received power level P x and the value of the local SAR are known in advance. The relative SAR value of the wireless device that is the device under test is estimated by relative comparison with the bell Po.

FIG. 1 is a configuration explanatory diagram showing a configuration of a local SAR measurement device according to an embodiment of the present invention.

The local SAR measurement device includes an electromagnetic probe 1, a synthesizer 2, and a signal processing unit 3. The electromagnetic wave radiated from the mobile phone antenna 12 of the mobile phone to be measured is measured. The mobile phone antenna 12 is connected to a wireless circuit 13 inside the mobile phone body 11, and is supplied with transmission power from the wireless circuit 13.

The electromagnetic probe 1 is configured by an antenna for detecting an electromagnetic wave, and as an electric field detection type antenna, for example, a small dipole antenna, a small monopole antenna, a normal mode helical antenna, an inverted F antenna, or the like can be used. Also, as a magnetic field detection type antenna, a small loop antenna, a shielded loop antenna, a slot antenna, and the like can be used. Alternatively, a traveling wave antenna in which a plurality of antenna elements are arrayed can be used. In the present embodiment, a plurality of electromagnetic probes 1 are provided, and FIG. 1 shows an example in which two are provided according to the electromagnetic radiation pattern 14 of the mobile phone antenna 12.

The combiner 2 combines the received power of the electromagnetic waves detected by the plurality of electromagnetic probes 1. For example, by using multiple 2-signal couplers that combine the received power from two electromagnetic probes 1 and combining the input and output in a tournament diagram, it is possible to combine the received power from 2 factorial electromagnetic probes 1 It is possible.

In this embodiment, the local SAR value of the device under test is estimated by performing a relative comparison between the received power of the mobile phone as the device under test and the received power of the reference mobile phone whose local SAR value is known in advance. I do. For example, if the local SAR value when the received power of the reference mobile phone is P0 is SAR0, and the received power obtained by measuring the mobile phone to be measured is Px, the local SAR The value SARx can be obtained from the above equation (15) using the following equation (16). … ()

Each of the plurality of electromagnetic probes 1 is arranged at a position from the mobile phone main body 11 to be a Fresnel area. The transmission power radiated from the mobile phone antenna 12 is received by a plurality of electromagnetic probes 1 in the Fresnel region. The received power of the electromagnetic wave from the mobile phone received by each electromagnetic probe 1 is combined by the combiner 2 and then input to the signal processing unit 3 to perform processing related to local SAR estimation. You.

Note that the Fresnel region here is a region in which the radiated electromagnetic field component from the electromagnetic wave radiation source is dominant is the radiated electromagnetic field component inversely proportional to the distance or the quasi-electrostatic field component inversely proportional to the cube of the distance. An area that is not dominant, and in which the induced electromagnetic field component, which is mainly inversely proportional to the square of the distance, is dominant.The distance from the electromagnetic wave radiation source is about human / 100 to 5 Refers to the area.

For example, when the transmission frequency of a mobile phone is in the 800 MHz band, its wavelength is about 38 cm, and thus the Fresnel region has a distance of about 0.38 to 190 from the mobile phone antenna 12. cm range. In addition, when the transmission frequency of the mobile phone is in the 1.5 GHz band, the wavelength is about 20 cm, so that the Fresnel region has a distance from the mobile phone antenna 12 of about 0.2 to 100 cm. Range.

In the example shown in FIG. 1, the electromagnetic probe 1 is assumed to be a mobile phone to be measured, assuming that both the 800 MHz band and the 1.5 GHz band are used as the operating frequency band. A plurality of phone antennas 12 are placed 1 to 5 cm apart. By arranging the two electromagnetic probes 1 in an area closer to the far field, the size of the entire measurement system can be configured to be about 20 x 20 x 50 cm, and the measuring device is suitable for production lines. Occupies less space.

In order to make the received power Px obtained from the output of each electromagnetic probe 1 as close as possible to the radiated power Pr, the position of the electromagnetic probe 1 should be located in the maximum direction of the electromagnetic field radiation pattern 14. desirable. As is evident from the electromagnetic field components radiated from the small dipole antenna shown in Equations (3) to (7), the electromagnetic field radiation pattern in the Fresnel region is not necessarily the electromagnetic field radiation pattern in the far field. Does not match. However, the electromagnetic field radiation pattern in the Fresnel region is closer to the far field than in the very near field, and the maximum radiation direction becomes more consistent as the distance increases. Therefore, in the Fresnel region, unlike the measurement in the very near field, stable measurement can be performed by disposing the electromagnetic probe 1 in the maximum direction of the electromagnetic field radiation pattern.

Further, the local SAR measurement device of the present embodiment is provided with a probe moving unit 15 as position adjusting means for adjusting the position by changing the relative positional relationship between the electromagnetic probe 1 and the mobile phone body 11. . As the position adjustment means, this probe moving unit The two electromagnetic probes 1 may be moved separately from the stationary mobile phone main body 11 as shown in FIG. 15, or a plurality of electromagnetic probes 1 may be simultaneously moved in the same direction in parallel. It may be the one that causes it. Alternatively, the two electromagnetic probes 1 may be fixed and the mobile phone main body 11 may be moved in parallel.

As the position adjusting means, for example, a plurality of electromagnetic probes 1 are integrally arranged on a circumference or a rectangle in a frame formed in a circular or square shape, and the mobile phone main body 11 is placed in the center of the frame. It can be realized by a configuration in which the entire frame or the mobile phone main body 11 can be moved left and right by arranging the frame. Further, for example, by providing a movable base on which the mobile phone main body 11 is disposed and automatically moving the position of the movable base under control of a convenience store, the entire measurement work can be automated. Note that each electromagnetic probe 1 does not necessarily have to be arranged at the same distance or parallel to the mobile phone main body 11 as long as it is within the range of the Fresnel region, and it is necessary to use the electromagnetic radiation pattern 14 according to the shape. It may be arranged so as to be in an optimal position or orientation.

Next, a procedure for estimating the local S A R of the mobile phone under test using the local S A R measuring apparatus of the present embodiment will be described with reference to the flowchart of FIG. In FIG. 3, what is surrounded by a broken line is a procedure executed in the apparatus of FIG.

First, in step S31, the local SAR value of the reference mobile phone (reference portable wireless device), SAR0, is measured with a long measurement time but high measurement accuracy. For example, the internal electric field detection shown in Fig. 7 It measures using the measuring device of a formula. Since the local SAR generally differs for each frequency band, if there are multiple operating frequency bands for the mobile phone to be measured, the measurement is performed for each frequency band.

Next, in step S32, the received power P 0 of the reference portable telephone (reference portable radio) is measured using the local SAR measurement device of FIG. At this time, the relative positional relationship between the electromagnetic probe 1 of the local SAR measuring device and the mobile phone main body 11 is adjusted in advance so that the measurement variation of the received power P0 is reduced as much as possible. Subsequently, in step S33, the reception power P x of the mobile phone under test (portable wireless device under test) is measured. At this time, if there is a plurality of operating frequency bands for the mobile phone under test, the received power Px is measured for each frequency band. And step S 3 In step 4, the received powers P0 and Px measured for the reference mobile phone and the mobile phone under test are calculated by substituting the received powers P0 and Px into the above equation (16), and the value of the local SAR SARx of the mobile phone under test is calculated. Ask. Then, in step S35, it is confirmed whether or not there is a mobile phone to be measured, and if there is another mobile phone to be measured, the processes in steps S33 and S34 are repeated.

According to the above procedure, the measurement of the reception power Px of the mobile phone under test can be performed in a very short time, so that a large number of mobile phones under test can be measured in a short time.

Fig. 4 is a diagram showing the relationship between the position of the electromagnetic probe 1 and the radiation directivity of the electromagnetic wave, showing how two different electromagnetic radiation patterns 14a and 14b are generated from the mobile phone antenna 12. I have. The electromagnetic field radiation pattern of a mobile phone often has various shapes according to the transmission frequency band, the length of the mobile phone body, the length of the antenna, and the like. For example, in the case of a mobile phone that uses two frequency bands in common, a completely different frequency band may be shared by one antenna, such as the 800 MHz band and the 1.5 GHz band. In this case, for example, in the 800 MHz band, the electromagnetic field radiation pattern 14a indicated by a broken line is obtained, and in the 1.5 GHz band, the electromagnetic field radiation pattern 14b is a solid line, and the shapes are different.

In FIG. 4, if the position of the electromagnetic probe 1 is at the point A, it is possible to obtain stable received power for the electromagnetic field radiation pattern 14a, but the electromagnetic field radiation pattern 14b On the other hand, since the observation is performed near the null, it is expected that the reproducibility of the measurement due to the fluctuation of the position and the like will also deteriorate as the reception level decreases. Conversely, if the position of electromagnetic probe 1 is at point B, stable received power can be obtained for electromagnetic field radiation pattern 14b, but near null for electromagnetic field radiation pattern 14a. , The reception level is low and the reproducibility of the measurement deteriorates. Furthermore, if the position of the electromagnetic probe 1 is at the point C, it is expected that the reproducibility of the measurement will deteriorate for both the electromagnetic field radiation patterns 14a and 14b. From these facts, the arrangement of the electromagnetic probe 1 is important in measuring the received power of the reference mobile phone and the mobile phone under test by the respective radiated electromagnetic fields. The following description is based on an example of data obtained by actual measurement. FIG. 5 is an example of the data showing the correlation between the received power measured using the local SAR measuring apparatus of the present embodiment shown in FIG. 1 and the local SAR. For the mobile phone under test, 20 products manufactured with the same structure were used, and in order to make the correlation easier to understand, the available power of the transmitter was deliberately dispersed by about ± 1.5 dB. I have. The vertical axis of FIG. 5 shows the local SAR data measured using the conventional measuring device shown in FIG. 7, and the horizontal axis shows the received power value measured by the local SAR measuring device of the present embodiment. . Here, the position of the mobile phone 11 is adjusted so that the position of the electromagnetic probe 1 is arranged in the maximum direction of the electromagnetic field radiation pattern 14.

From the correlation data in Fig. 5, it can be seen that the received power and the local SAR are in a proportional relationship, and that the local S SAR can be estimated from the measured value of the received power. In the data in this example, the correlation coefficient between the received power and the local SAR is 0.94, and sufficient accuracy has been obtained to easily estimate the local SAR in the mass production process.

On the other hand, FIG. 6 shows the case where the position of the mobile phone to be measured is shifted by 60 mm from the position of the electromagnetic field radiation pattern 14 in the maximum direction using the local SAR measurement apparatus of the present embodiment shown in FIG. This is an example of data indicating the correlation between the received power Px and the local SAR. In this example, the mobile phone used for the measurement and the local SAR value are the same as in Fig. 5, but the position of the electromagnetic probe 1 with respect to the mobile phone under test is from the maximum direction of the electromagnetic field radiation pattern 14. Due to the deviation, the reception level is extremely low. Furthermore, the value of the local SAR with respect to the received power varies, and the correlation coefficient is as low as 0.53, indicating that sufficient accuracy has not been obtained to estimate the local SAR. Thus, optimal selection of the relative positional relationship between the electromagnetic probe 1 and the mobile phone main body 11 and the mobile phone antenna 12 is indispensable for highly accurate local SAR estimation. To determine the optimal positional relationship, for example, pre-measurement is performed using a plurality of reference mobile phones whose local SAR values are previously determined, and the positional relationship at which the correlation increases as shown in Fig. 5 is determined. can do. Then, based on the optimal set value, the relative positional relationship between the electromagnetic probe 1, the mobile phone main body 11 and the mobile phone antenna 12 is adjusted by position adjusting means such as the probe moving section 15.

Also, for example, the graph of correlation data shown in Fig. Thus, the local SAR of the mobile phone under test can be estimated with high accuracy by calculating the proportional coefficient SAR 0 of the above equation (16) from the slope of the approximate straight line of the graph.

Since the electromagnetic field radiation pattern 14 does not change unless the distribution of current flowing through the mobile phone antenna 12 changes, the optimal relative positional relationship can be uniquely determined for each product, and the electromagnetic probe is used for each product in the production process. There is no need to adjust the relative positional relationship between 1 and the mobile phone body 11. Therefore, measurement can be performed in a short time, and it is suitable for measuring a large number of products.

Furthermore, in the case of a mobile phone sharing a plurality of frequency bands, a displacement mechanism that can arbitrarily move the position of the electromagnetic probe 1 or the mobile phone main body 11 on the production line as a position adjusting means is provided. The received power PX can be evaluated at the optimal position in each frequency band, and highly accurate local SAR estimation is possible.

As described above, according to the present embodiment, the local SAR of the small wireless device to be measured can be reduced in a short time in a small space suitable for a production line for manufacturing a small portable wireless device such as a mobile phone, and It can measure with high accuracy. Also, for wireless devices that share multiple frequency bands, the local SAR can be reduced by adjusting the relative positional relationship between the electromagnetic probe and the device under test according to different electromagnetic field radiation patterns in each frequency band. It is possible to estimate with high accuracy. Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. α2002-143326 filed on May 17, 2002, the contents of which are incorporated herein by reference.

As described above, according to the present invention, it is possible to estimate a local SAR in a short time and with high accuracy on a production line of a small wireless device such as a mobile phone. An AR measuring device and method can be provided.

Claims

The scope of the claims

1. A plurality of electromagnetic probes for measuring electromagnetic field levels in the Fresnel region of electromagnetic waves radiated from a wireless device, a signal processing unit for processing an electromagnetic field level obtained by the electromagnetic probe to calculate a local SAR value, Position adjusting means for adjusting a relative positional relationship between the electromagnetic probe and the wireless device,

The electromagnetic probe measures the electromagnetic field level of each of the reference wireless device whose local SAR value is known in advance and the wireless device to be measured, and that the SAR value is proportional to the electromagnetic field level in the signal processing unit. A local SAR measurement device that estimates a local SAR value of the wireless device to be measured from a local SAR value of the reference wireless device that is known in advance.

2. The position adjusting means moves at least one of the electromagnetic probe and the wireless device in accordance with an electromagnetic field radiation pattern from the wireless device to adjust a relative positional relationship between the two. A local SAR measurement device according to range 1.

3. The position adjusting means, when a plurality of electromagnetic field radiation patterns from the wireless device are present in accordance with a transmission frequency, moves at least one of the electromagnetic probe and the wireless device according to the transmission frequency to make a relative relationship between the two. 2. The local SAR measurement device according to claim 1, wherein a local positional relationship is changed.

4. measuring the electromagnetic field level of the reference wireless device whose local SAR value is known in advance in the Fresnel region of the electromagnetic wave radiated from the wireless device; and measuring the electromagnetic field level of the wireless device to be measured by the wireless device. Measuring in the Fresnel region of electromagnetic waves radiated from

Using the fact that the SAR value is proportional to the electromagnetic field level based on the measured electromagnetic field level, the measurement pair is calculated from the local SAR value of the reference wireless device that is known in advance. Estimating the local SAR value of the elephant's wireless device,

A local S A R measurement method, characterized by having:

5. When there are a plurality of electromagnetic field radiation patterns from the wireless device according to the transmission frequency, move at least one of the electromagnetic probe for measuring the electromagnetic field level according to the transmission frequency and the wireless device. 5. The local SAR measurement method according to claim 4, further comprising the step of changing the relative positional relationship between the two.