Note: Descriptions are shown in the official language in which they were submitted.
CA 02550158 2002-08-08
APPARATUS FOR MEASURING ABSORBED POWER
This is a division of co-pending Canadian Patent Application
No. 2,421,821 filed on August 8, 2002.
TECHNICAL FIELD
The present invention relates to an apparatus which uses a phantom
simulating the electromagnetic characteristics of a human body to measure the
amount of absorption by the human body of a radio wave or waves radiated
from a radio transmitter which is operated in the vicinity of the body through
a
relative scan of the phantom and the radio transmitter.
l0 BACKGROUND ART
In the prior art practice, the power absorbed by a human body, for
example, by the head of the human body, has been estimated by constructing a
head simulation phantom which simulates the configuration and the
electromagnetic characteristics of the head of the human body and measuring
15 the amount of power absorbed by the phantom.
A conventional example of the prior art will be described with
reference to Fig. 1. A head simulation phantom 2 is constructed by forming a
recess 12 configured to divide the head of the human body into two equal parts
laterally in a top surface of a vessel 11 and filling the recess 12 with a
liquid
20 medium 10 which simulates the electromagnetic characteristics of the head.
By
way of example, the liquid medium for a 900 MHz solution comprises 56.5% of
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2
sucrose, 40.92% of deionized water, 1.48% of sodium chloride, 1.0% of
hydroxyl cellulose and 0.1 % of bactericide as disclosed in a literature
IEC TC 106/PT62209 "Specific Absorption Rate (SAR) in the frequency
range 300 MHz to 3 GHz - Measurement procedure - Part 1: Hand-held
Mobile Wireless Communication Devices", published February 2005, or the
like. A radio transmitter 3 which represents a radio wave radiation source is
secured to the bottom surface of the vessel 11 on the outside thereof at a
location central of the vessel 11 or which corresponds to the ear of the head
of
the human body. An electromagnetic field probe 1 which detects an electric or
a magnetic field is inserted into the liquid medium 10 and is scanned in a
plane
which opposes the radio transmitter 3. In this instance, the head simulation
phantom 2 and the radio transmitter 3 are separately secured and only the
electromagnetic field probe 1 is moved as indicated by arrows 8 for purpose of
scan. A resulting detected value of the electromagnetic field probe 1 is
squared,
and the squared value is multiplied by a calibration factor to determine the
absorbed power which occurs within the head simulation phantom 2. Broken
lines 6, shown laterally offset, represent the locus of scan of the probe 1,
and
this corresponds to the measurement of absorbed power from the radio wave in
a situation that the mobile telephone is located close to the ear of the head
of the
human body during the transmission and reception with the antenna (not
shown) of the radio transmitter 3 extending in a direction through the casing
of
the radio transmitter 3 which runs substantially parallel to the bottom
surface of
the vessel 11.
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The head simulation phantom 2 shown in Fig. 1 is filled with the
liquid medium 10, and is inconvenient in its handling. Since the probe 1 is
moved within the liquid medium 10 for purpose of scan and measurement, the
liquid medium 10 remains open to the air, and there arises a problem that the
liquid medium 10 may be evaporated to cause an aging effect of the
electromagnetic characteristics thereof.
Another example of the prior art will be described with reference to
Fig. 2. A head simulation phantom 2 which simulates the configuration and the
electromagnetic characteristics of the head of the human body is constructed,
and an electromagnetic field probe 1 is inserted into an opening 21 formed in
the phantom 2. The electromagnetic field probe 1 is located close to the ear
of
the head simulation phantom 2, while a radio transmitter 3 which represents a
radio wave radiation source is positioned on the external surface of the head
simulation phantom 2 close to the ear. The transmitter 3 is moved vertically
and back-and-forth, as indicated by arrows 8, for purpose of two-dimensional
scan while deriving a detected value from the electromagnetic probe 1, and
multiplying a calibration factor to the square of the detected value to
determine
the absorbed power. The locus of scan for this case is illustrated by broken
line 6, shown laterally offset. It is assumed in Fig. 2 that a mobile
telephone is
used as the radio transmitter 3 with an antenna extended from the telephone
case to simulate the manner of use of a mobile telephone.
The phantom 2 shown in Fig. 2 simulates the head of the human body by
a spherical solid dielectric 10' or by a liquid dielectric (liquid medium) 10
which fills the interior of a spherical vessel. The solid dielectric 10' has a
dielectric constant Er' =52 and a dielectric loss tan8=55% (at 900 MHz), for
l
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4
example, and comprises 57% of polyvinylidene fluoride, 10% of ceramic
powder and 33% (volume %) of graphite powder, as disclosed in a literature by
H. Tamura, Y. Ishikawa, T. Kobayashi and T. Nojima "A Dry Phantom
Material Composed of Ceramic and Graphite Powder," IEEE Trans.
Electromagn. Compat., Vol. 39, No. 2, pp 132-137, May 1997 or the like.
Assuming that the head phantom 2 is formed with a size simulating
the head of the human body, or with a sphere having a diameter of 200mm, it
contains a volume of 4 x ~ x {(200/2)mm}3 /3. The dielectric which simulates
the electromagnetic characteristics of the head of the human body has a
density
which is equal to about 0.002g/mm3 for the solid dielectric 10' and which is
equal to about 0.001 g/m3 for the liquid dielectric (liquid medium).
Accordingly, the head simulation phantom 2 has a weight which is equal to the
volume 4 x ~ x {(200/2)mm}3 /3 multiplied by the density 0.002g/mm3 or
8400g for the solid dielectric 10' . Since the liquid dielectric 10 has a
density
which is nearly one-half that of the solid dielectric 10' , the phantom will
have a
weight which is nearly one-half that of the solid dielectric 10' phantom.
Thus,
a conventional head simulation phantom 2 has a weight which is as high as
4200g or 8400g, and presented an inconvenience in its handling and
transportation.
The purpose of measuring the absorbed power is to know how much _
of a radio wave is absorbed by the human body during the use of a mobile
telephone or a transceiver, and the measurement takes place in a so-called
near field in which a distance from a radio wave radiation source to the
phantom 2 is normally very small. As a consequence, there is a great
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influence that the reproducibility of positional relationship between the
radio
transmitter 3, the head simulation phantom 2 and the electromagnetic field
probe 1 has upon the reproducibility of results of measurement. In other
words, if there is a relatively small shift in the relationship, there occurs
a
5 change in the reflection characteristic of the phantom 2, producing a change
in
the distribution of the radiated electromagnetic field. If the radio
transmitter 3
is held by the hand 4' of a measuring personnel as indicated in Fig. 3, it is
difficult to maintain a correct position of the transmitter relative to the
phantom 2, and a good reproducibility of measured values cannot be
guaranteed. There also occur influences that the radio wave radiated from the
radio transmitter 3 is absorbed by the hand 4' of the measuring person and
that
the current distribution on the antenna 5 of the radio transmitter 3 may be
changed due to the hand 4' of the measuring personnel. Where the radio
transmitter has a bulky volume or heavy, it may be difficult to conduct a
spatial
scan of the radio transmitter 3 relative to the phantom 2 by hand 4' .
Conversely, if the radio transmitter 3 is fixed while the absorbed
power measuring assembly 7 comprising the head simulation phantom 2 and the
electromagnetic field probe 1 scans through a two-dimensional movement
relative to the radio transmitter 3, it is a troublesome operation to perform
the
measurement by manually moving and scanning the absorbed power measuring
assembly 7 when the head simulation phantom 2 has a weight which is as high
as 4200g or 8400g as described above.
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It is an object of the present invention to provide an apparatus for
measuring absorbed power which permits a scan through a relative movement
between an absorbed power measuring assembly comprising a simulation
phantom and an electromagnetic field probe and a radio transmitter to be
performed in a relatively simple manner.
DISCLOSURE OF THE INVENTION
In accordance with one aspect of the present invention there is
provided an apparatus for measuring absorbed power including an
electromagnetic field probe disposed within a phantom which simulates the
1 o electromagnetic characteristics of a human body, and wherein the strength
of an
electric field or a magnetic field of a radio wave externally irradiated upon
the
phantom is measured by the electromagnetic f eld probe, and the power of the
radio wave absorbed by the human body is estimated on the basis of measured
values; further comprising a scan mechanism which causes a relative
15 movement between the phantom and a radio transmitter.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a conventional apparatus
i
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for measuring absorbed power using a head simulation phantom in
which a liquid dielectric (liquid medium) is used;
Fig. 2 is a perspective view of a conventional apparatus
for measuring absorbed power in which an electromagnetic probe is
inserted inside a head simulation phantom and an absorbed power
measuring assembly is fixed while spatially scanning a radio
transmitter.
Fig. 3 is a perspective view of a conventional apparatus
for measuring absorbed power in which a radio transmitter is
1o manually held by a measuring personnel for purpose of scan;
Fig. 4 illustrates a power absorption by a head simulation
phantom;
Fig. 5 shows a layout of a calculation model including a
head simulation phantom and a half wavelength dipole antenna
is acting as a radio wave radiating source in order to calculate a
distribution of the electromagnetic field within the phantom;
Fig. 6 graphically shows a normalized power calculation
value at the location of the electromagnetic field probe which is to
be disposed inside the head simulation phantom, plotted against an
2o antenna position as measured along the length of the antenna;
Fig. 7A is a cross section showing an example of an
absorbed power measuring assembly with the apparatus according to
the invention which uses a solid dielectric 10';
Fig. 7B is a cross section showing an example of an
25 absorbed power measuring assembly in the apparatus of the
invention which uses a liquid medium 10;
Fig. 8 is a perspective view illustrating the set-up in which
a radio transmitter is fixed while an absorbed power measuring
l
CA 02550158 2002-08-08
assembly according to the invention performs a spatial scan;
Fig. 9 is a cross section showing an example in which a
spacer is applied to part of a phantom;
Fig. 10 is a cross section showing an example in which the
s entire surface of the phantom is covered by a spacer;
Fig. 11 illustrates that the portion of the. phantom which is
covered by the spacer is maintained in contact with the radio
transmitter while it is subject to a moving scan, permitting a
constant distance to be maintained between the phantom and the
1o radio transmitter;
Fig. 12 illustrates the use of detachable spacers having
different thicknesses in order to change the distance between the
head simulation phantom and the radio transmitter, Fig. 12A being a
cross section for a small spacing, Fig. I2B a cross section for an
15 intermediate spacing and Fig. 12C a cross section for a greater
spacing.
Fig. 13 is a perspective view of part of an exemplary
spacer having a variable thickness;
Fig. 14 illustrates the use of the spacer shown in Fig. 13,
2o allowing the distance between the head simulation phantom and the
radio transmitter to be changed;
Fig. 15A shows another example of a phantom with a
handle gripped by a measuring personnel;
Fig. 1 SB shows a further example of a phantom with a
25 handle which is gripped by a measuring personnel;
Fig. 16A shows a simulation phantom formed by an
ellipsoid;
Fig. 16B shows a simulation phantom formed by a regular
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9
cube;
Fig. 16C shows a simulation phantom formed by a
rectangular body;
Fig. 16D shows a simulation phantom formed by a solid
cylinder;
Fig. 17A is a perspective view of a head simulation
phantom which relatively closely simulates the configuration of a
head and having a measuring plane which corresponds to the front
of a face;
1o Fig. 17B is a perspective view of a head simulation
phantom which relatively closely simulates the configuration of a
head and having a measuring plane which corresponds to the side of
a face;
Fig. 18A is a perspective view of an embodiment of the
~s second invention;
Fig. 18B is a perspective view showing an exemplary
engagement retaining mechanism for maintaining a slidable
relationship between a drive bar and a retainer with the bottom
surface of a retainer 4 shown iri Fig. 1.8A disposed upside;
2o Fig. 19 illustrates an example of a range of measurement
obtained when the absorbed power measuring assembly 7 undergoes
a two-dimensional scan in the arrangement of Fig. 18A;
Fig. 20 is a cross section showing an example of an
absorbed power measuring assembly 7 which uses a liquid medium
25 10;
Fig. 21 is a perspective view of an exemplary absorbed
power measuring assembly in which a plurality of electromagnetic
field probes are fixedly mounted as a linear array within the
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phantom;
Fig. 22 is a perspective view of another absorbed power
measuring assembly in which a plurality of electromagnetic field
probes are fixedly mounted as a matrix inside the phantom;
Fig. 23 is a perspective view illustrating the situation that
the radiation of a radio wave from a radio transmitter is influenced,
not only by the phantom, but also by aerial condition during the
scan;
Fig. 24 is a. perspective view of an example of a phantom
to in the form of a flat plate which can be regarded as having an
infinity size a.s far as a radio transmitter is concerned;
Fig. 25 is a perspective view of an example of a scan
mechanism which ~o-mprises a belt conu.e_yor;
Fig. 26 is a perspective view of an example of a plurality
is of electromagnetic field probes disposed within the phantom and
which are disposed perpendicular to the direction o.f movement. of
the belt conveyor;
Fig. 27 is a perspective view of another example in which
a plurality of electromagnetic field probes~~ disposed withim the
2o phantom are disposed at an angle with respect to the direction of
movement of the belt conveyor;
Fig. 28 is a perspective view of an example of an absorbed
power measuring assembly comprising a plurality of phantoms
which are formed to an equal configuration from an equal material
2s and a plurality of electromagnetic field probes which are secured at
different positions within the respective phantoms;
Fig. 29 is a perspective view of an example of an absorbed
power measuring assembly comprising a plurality of phantoms
CA 02550158 2002-08-08
IZ
formed to the same configuration and from the same material and a
plurality of electromagnetic field probes which are secured at an
identical position within the respective phantoms;
Fig. 30 is a perspective view of an example illustrating a
position detecting sensor which is mounted on the phantom;
Fig. 31 is a perspective view of an example in which a
plurality of position detecting sensors are mounted on the phantom
in a manner to surround the electromagnetic field probe;
Fig. 32 is a perspective view of a radio anechoic box in
which an absorbed power measuring assembly and a scan
mechanism are entirely confined;
Fig. 33 is a perspective view of an example of a radio
anechoic box in which an absorbed power measuring assembly is
confined and through which a belt conveyor passes; and
Fig. 34 is a perspective view of a modification of Fig. 33.
BEST MODES OF CARRYING OUT THE INVENTION
First Invention
The principle of one aspect of the present invention will
be described first. When the head simulation phantom 2 which
2o simulates the configuration and the electromagnetic characteristics
of the head of the human body shown in Fig. 2 is irradiated with a
radio wave in SHF band, which represents a transmission frequency
of a mobile telephone, or with a radio wave of a higher frequency
band, the absorption of the power by the phantom 2 takes place in a
manner indicated in Fig. 4. As shown, the absorption will be
greater in a surface layer 2a of the head simulation phantom 2 which
is located close to the radio transmitter 3, but will be reduced in the
inner thin layer 2b, and will be substantially equal to zero in the
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12
inside 2c. Specifically, when a half wavelength dipole antenna is
disposed at a distance of l0mm with respect to the phantom 2
having a diameter of 200mm, for example, and a radio wave (of
frequency 900 MHz) is irradiated upon the phantom 2, it follows
s that denoting the absorption of the power of the radio wave which
occurs at the surface of the phantom 2 by I, the absorption at a point
which is removed 20mm from the surface of the phantom will be
reduced to 1 / 10, and will be reduced to 1 / 100 when removed S Omm.
In this manner, most part of the phantom is not concerned with the
to measurement of absorbed power except for. a very small portion
which is located very close to the surface of the head simulation
phantom 2. According to one aspect of the present invention, an
advantage is taken of this by reducing the volume and the weight of
the head simulation phantom 2. If there is a significant amount of
15 absorption of the radio wave at a location disposed deep inside the
phantom 2, a reduction in the volume of the phantom 2 will result in
removing an internal portion where the absorption of the radio wave
is occurring to prevent the measurement from the inner portion.
However, such likelihood is eliminated since the absorption of the
2o radio wave occurs only a portion thereof which is located close to
the surface. It is to be noted that eyes and nose displayed in
phantom lines in Fig. 4 merely indicate that this phantom simulates
the head.
The fact that there is no problem when the volume of the
25 phantom 2 is reduced will be discussed below.
A model is considered as illustrated in Fig. 5. A sphere
having a diameter of Dmm, a dielectric constant sr'=S 1.8 and a
conductivity a=I.43S/m is used as a head simulation phantom 2.
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13
The phantom 2 is formed with a probe insertion opening 21 which
extends from a point on the surface through the center to a point
close to the opposite surface. The probe insertion opening 21 has a
diameter of lOmm, and it is assumed that a distance from the inner
s end of the opening to the surface of the head simulation phantom~2
is equal to l Omm. A half wavelength dipole. antenna 5 is vertically
disposed at a location which is spaced by 1 Omm from the surface of
the head simulation phantom 2 which opposes the inner end of the
probe insertion opening 21. Fig. 6 graphically shows a result of
to calculation for a normalized power Pn (as referenced to the power
which prevails for L=0), plotted against the height Lmm when the
half wavelength dipole antenna 5 is moved vertically up and down
from a reference point where the feed point is located opposite to
the inner end 21 a. The normalized power at the location, where the
~s electromagnetic field probe 1 is disposed or at the inner end Zla of
the probe insertion opening 2I can be calculated according t~o the
finite-difference time-domain method (see, for example, "Finite
Difference Time Domain Method for Electromagnetics," Karl S.
Kung and Raymond J. Luebbers, CRC Press 1993 or the like). It is
2o to be noted that the input power to the half wavelength dipole
antenna 5 is maintained constant, and the frequency of the radiated
wave is 900 MHz. A curve which links o plots corresponds to a
diameter D of the phantom 2 which is equal to 200mm (conventional
one), a curve which links a plots corresponds to a diameter D equal
25 to 100mm, and a curve which Iinks 0 plots corresponds to D equal to
40rnm.
It will be seen that the normalized power distribution for
D=100mm is substantially similar to the normalized power
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14
distribution of the conventional phantom in which D=200mm.
Thus, it is considered that i~f the diameter of the head simulation
phantom 2 is reduced to one-half the conventional value, or if the
volume and the weight are reduced to 1/8 times the conventional
s value, it is still possible to simulate the head of a human body.
When the head simulation phantom 2 having D=100mm is
manufactured, the volume will be 4x~x{(100/2)mm}3/3=Sx105mm3,
and its weight will be 4x~x {(I00/2)mm} 3/3=Sx 105mm3 multiplied
by 0.002g/mm 3 or 1 OOOg when the solid dielectric 10' is used, and
the weight will be further reduced to one-half when the liquid
medium 10 is used. The weight of the head simulation phantom 2
which is on the order of SOOg or 1000g means that a measuring
personnel can easily handle the phantom 2 and move it for purpose
of scan. When the diameter D is reduced to one-fifth or D=40mm,
the normalized power which is substantially equal to the
conventional one having D=200mm can be obtained if. L is Located
within 20mm. However, when the value of L increases to the order
of 60mm, the normalized power will be nearly twice the normalized
power obtained with.the conventional one having D=20Omm. The
2o tendency that the normalized power increases above the value
obtained with a conventional one having D=200 as the distance
between the probe 1 and the antenna feed point increases occurs for
a diameter D which is equal to or less than 100mm. However, if
the required range of measurement L is small, there is no problem.
25 When the range of measurement L increases, it is possible to reduce
the weight and the cost required even though the accuracy of
measurement is degraded. It is to be noted that with a phantoy
having a diameter D which is equal to or greater than 100mm, there
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ZrJ
is a less contribution to reducing the weight and the cost required
even though a higher accuracy can be obtained.
Consequently, in an embodiment of the present invention,
a phantom 2 which simulates the configuration and the radio wave
absorption characteristics of part of the human body or the head in
the example to be described below comprises a phantom 2 as shown
in Fig. 7A in which a sphere is formed with the solid dielectric 10'
comprising the materials mentioned above in connection with Fig. 2,
for example. In particular, the volume of the phantom 2~ is chosen
to to be equal to or less than 1/8 times the volume of .part of the human
body being simulated, or the volume of the normal head of the
human body or S x 1.0 Smm 3 . - The less the volume of the phantom 2,
the better in respect of reducing the weight, even though the
accuracy of measurement becomes degraded as mentioned above.
ns Accordingly, a minimum value for the volume of the phantom 2 may
be chosen to be a volume which permits at least the probe 1 to~ be
contained even though the accuracy of measurement may be
degraded to a degree. A probe insertion opening 21 is formed
extending from a point on the surface of the phantom Z and
2o extending to another point located close to the surface, and an
electromagnetic field probe 1 is inserted into the probe insertion
opening 21. For example, an adhesive 14 is filled into the probe
insertion opening 21, thus securing the electromagnetic field probe
1 within the phantom 2 to be integral therewith.
2~ It will be seen from the above description with reference
to Fig. 4 that a spacing D 1 between the electromagnetic field probe
1 and the closest surface of the phantom 2 be preferably within
20mm, in particular, within l Omm in order to achieve a certain
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I6
accuracy of.measurement. While it is preferred to have a smaller
value for D l, a suitable value is chosen in consideration of the ease
of manufacture and a resistance to fracturing. As indicated by
single dot chain lines in this Figure, a lead wire 1 a of the probe 1 is
connected to a calculation and display unit 80 in the similar manner
as a conventional apparatus of this kind, and the calculation and
display unit 80 calculates and displays the absorbed power using the
values detected by the probe 1 and using the absorption effect.
As shown in Fig. 7B, a head simulation phantom 2 may be
to constructed using a confined vessel 11 which simulates the
configuration of the head and a liquid medium 10 which fills the
vessel 11. The liquid medium 10 may be similar to that mentioned
previously in connection with Fig. 1. In this instance, the volume
of the phantom 2 is again chosen to be equal to or less than 1/8
times the volume of the normal head of the human body or
5 X 10 Smm 3. The confined vessel 11 is formed with a probe
insertion opening 21 in the similar manner as in Fig. 7, into which
an electromagnetic field probe 1 is inserted and may be secured by
using an adhesive 14, for example, to be integral with the phantom 2.
2o The vessel 11 is formed of a material such as acrylic resin or Teflon
(registered trademark) having a low dielectric constant which is
close to that of the air pereferably, thus preventing the distribution
of a radio wave radiated from a radio transmitter 3 (not shown) from
being disturbed. In Figs. TA and 7B, in order to connect the
electromagnetic field probe 1 to be integral with the phantom 2,
other techniques than filling the adhesive 14 into the probe insertion
opening 21 may be used to secure them together.
The spherical head simulation phantom 2 shown in Figs.
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17
7A and 7B has its volume reduced to or less than 5 x 10 Smm' which
corresponds to 1 /8 times the volume of the conventional phantom
which represents the size of the head of the human body, and the
weight is reduced to or less than 1/8 times the weight of the
conventional phantom, and thus is greatly reduced in weight. The
weight will be equal to or less than SOOg when the liquid medium 10
is used, and will be equal to or less than 1000g when the solid
dielectric 10' is used. Accordingly, while the radio transmitter 3 is
retained by and fixed on a retainer 4 as illustrated in Fig. 8, a
measuring personnel can hold the phantom 2 by one hand and easily
move it in the directions indicated by solid line arrows 8 in
proximity to the radio transmitter 3 for purpose of scan. The locus
of scan 6 of the probe 1-is--shown offset in this Figure.
Alternatively, the phantom 2 may be fixed while the radio
transmitter 3 may be moved in directions indicated by broken Line
arrows 8. The normalized power distribution will be substantially
similar to the normalized power distribution of a conventional
arrangement where D=200mm. The volume of the solid dielectric
10' or the volume of the confined vessel in which the liquid medium
20 10 is filled, which constitutes the head simulation phantom, is
reduced, thus reducing the cost of materials and the manufacturing
cost by a corresponding amount. In addition, because the phantom
2 is integral with the electromagnetic field probe 1, the relative
positional relationship therebetween is easily reproducible during
25 the scan movement.
Fig. 9 shows another embodiment of the invention. In
this embodiment, at least a portion of the surface of the head
simulation phantom 2 shown in Fig. 7 which is located close to the
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r ,
18
radio transmitter 3 or the surface portion located close to the
location of the electromagnetic held probe 1 is coated by a thin
spacer 22. The spacer 22 may be adhesively secured or detachably
mounted using a tacky bonding agent or may be detachably mounted
s by fitting by choosing its configuration. As shown in Fig. 10, the
spacer 22 may coat substantially the entire surface of the head
simulation phantom 2. The spacer 22 is constructed with a
material such as acrylic resin, Teflon (registered trademark), foamed
styrol or wood which has a low dielectric constant close to that of
to the air, thus minimizing a disturbance in the distribution of the
electromagnetic field which may occur by the presence of the spacer
22.
With this construction, a relative movement can take place
either vertically or back-and forth, as viewed in Fig. 1 l, between the
is phantom 2 and the radio transmitter 3 for purpose of scan while
maintaining the head simulation phantom 2 and the radio transmitter
3 in contact with each other, thus maintaining a constant spacing
therebetween and improving the reproducibility of the measurement
of absorbed power. If the radio transmitter 3 is formed with a
2o projection, which is appended thereto, the head simulation phantom
2 can not be damaged by the projection during the scan which takes
place in contact therewith, thus preventing any damage o~ a sensor
of the electromagnetic field probe 1 from occurring. When the
spacer 22 is formed around the entire surface of the phantom 2, as
25 shown in Fig. 10, the spacer 22 is effective to protect the phantom 2
from mechanical damage.
The thickness of the spacer 22 simulates the thickness of
the ear of the human body or simulates the thickness of a cover
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19
applied to the radio transmitter 3, serving the both simulations.
Accordingly, it is desirable that the spacer 22 has a thickness which
is on the order of 20mm at maximum and on the order of 1 mm at
minimum, and by changing the thickness of the spacer 22, a variety
of simulations can take place. By way of example, as shown in Fig.
12, a plurality of semi-spherical spacers 22 having mutually
different thicknesses may be provided, and are mounted on the
phantom 2 in a detachable manner. Figs. 12A, 12B and 12C
illustrate that sequentially thicker spacers 22 are mounted in an
interchangeable manner.
By way of example, as shown in Fig. 13, three spacers 22a,
22b and 22c are stacked one above another and are coupled together
in a slidable manner. Such coupling is achieved by removing both
lateral edges of the spacer 22a which are located toward the spacer
~5 22b along the length thereof to define a wedge-shaped coupler 24
while the surface of the spacer 22b which is disposed toward the
spacer 22a is formed with a coupling recess 25 in which the
wedge-shaped coupler 24 is received in the manner of a wedge, thus
allowing the spacers 22a and 22b to slide relative to each other
2o along their length while securing them together in the direction of
the thickness. A similar wedge-shaped coupling takes place
between the spacers 22b and 22c to couple them in a slidable
manner in the direction of the length while securing them together
in the direction of the thickness.
25 As shown in Fig. 14, these spacers 22a, 22b and 22c which
are stacked one above another are mounted on the phantom 2 so as
to be interposed between the phantom 2 and the radio transmitter 3.
With this arrangement, by sliding the spacers, it is possible to
CA 02550158 2002-08-08
interpose only the spacer 22a between the phantom 2 and the radio
transmitter 3, to interpose both spacers 22a and 22b as shown in Fig.
14 or to interpose the spacers 22a, 22b and 22c. In this manner,
the thickness of the spacer 22 which is interposed between the
s phantom 2 and the radio transmitter 3 can be changed. The number
of stacked spacer 22 is not limited to three, but may be suitably
increased or decreased, and the individual thickness of the stacked
spacers 22a, 22b and 22c can be chosen to be different from each
other.
10 As shown in Fig. I SA, a handle 23 is secured, for example,
adhesively, to the open end of a probe insertion opening 21 in the
phantom 2 and extends in the direction opposite from the probe
insertion opening 2I to make the radio wave which is radiated from
the radio transmitter 3 to be free from the influence of the hand 4'
m as the hand 4' is moved away from the radio transmitter 3 when the
hand 4' of a measuring personnel is brought close to the handle 23
for purpose of scan and measurement as illustrated in Fig. 8, for
example. The handle 23 is formed of a material having a low
dielectric constant such as acrylic resin, fluorine containing resin,
2o foamed styrol resin or wood. The lead wire 1 a of the
electromagnetic field probe 1 is passed through an opening 26
which is formed inside the handle 23 in communication with the
probe insertion opening 21. In this instance, an adhesive 14 is
filled into the opening 26 to secure the probe 1 to the phantom 2.
2s As shown in Fig. 15B, the handle 23 may be mounted on the
phantom 2 so as to extend in a direction perpendicular to the
direction in which the probe insertion opening 21 extends.
The configuration of the head simulation phantom 2 is not
CA 02550158 2002-08-08
21
limited to the sphere mentioned above, but may assume a
geometrically simple configuration such as an ellipsoid as shown in
Fig. 16A, a cube as shown in Fig. 16B, a rectangular body as shown
in Fig. 16C or a solid cylinder as shown in Fig. 16D as long as the
s purpose of simulating the head of the human body is served. In
any event, it has a volume which is on the order of 1 /8 times the
volume of the head of a normal man or less, namely, 5 X l O Smm3.
Rather than being limited to a phantom which simulates the head of
the human body, a simulation phantom having a configuration as
1o illustrated in Figs. 16A to D may be constructed to simulate part of
the human body such as the arm or trunk. In any event; it has a
volume which is equal to or less than 1/8 times the normal volume
of part of the human body being simulated.
By constructing the phantom as a sphere or a
is geometrically simple configuration as illustrated in Figs. 16A to D,
a distribution of the electromagnetic field within the phantom 2
which is not formed with a probe insertion opening 21 may be
analytically obtained using the radio transmitter 3 as a dipole
antenna, and a calibration factor for the electromagnetic field probe
20 1 can be determined on the basis of such analytical results.
By constructing a phantom 2 which simulates the
configuration of the head of the human body, or simulating the front
face of the head by a square-shaped plane 2a as a front surface as
shown in Fig. 17A, forming a probe insertion opening 21 so that it
2~ extends from the rear side to a point close to the front surface 2A
and inserting an electromagnetic field probe 1 therein, an absorbed
power measuring assembly 7 which can be used with a transceiver
as the radio transmitter 3 may be constructed. Eyes and nose
CA 02550158 2002-08-08
22
indicated by single dot chain lines may assume configurations
which correspond to actual eyes and nose, or may be a simple plane
with dot indications thereon which represents the front face for the
sake of convenience. Alternatively, as shown in Fig. 17B, the
square-shaped plane 2a may be provided as a front surface which
simulates the lateral side of the face of the head and an
electromagnetic field probe 1 may be inserted therein to construct
an absorbed power measuring assembly 7 which can be used when
utilizing a mobile telephone as the radio transmitter 3. The ear
to indicated by single dot chain lines may be configured so as to
correspond to the actual ear, or may be a simple plane with a dot
indication representing the lateral side of the face fox the sake of
convenience. When the configuration is relatively complex as in
such a phantom, a distribution of the electromagnetic field cannot
be analytically obtained to determine a calibration factor for the
electromagnetic field probe 1, but the finite-difference time-domain
method may be used to derive a distribution of the electromagnetic
field numerically, and a calibration factor for the electromagnetic
field probe 1 can be determined therefrom.
While the above description has principally dealt with
constructing the phantom 2 with the solid dielectric I0', the
- phantom 2 of a type in which the liquid medium 10 is confined into
the enclosed -vessel 11 as shown in Fig. 7B may be used as phantoms
which are used in the embodiments shown in Figs. 9 to 17. In this
instance, since the liquid medium 10 is sealed, an aging effect in the
electromagnetic characteristics which may result from the
evaporation of components can be prevented while facilitating the
handling.
CA 02550158 2002-08-08
23
Second Invention
Fig. I8 shows an embodiment of another aspect of the
invention, and parts corresponding to those shown in Figs. I to 17
are designated by like reference characters as used before.
s A phantom 2 which simulates the electromagnetic
characteristics of the human body is provided. In this instance,
there ~is no need to simulate the configuration of part of the human
body. Fig. 18 represents an arrangement in which the phantom 2 is
formed with the solid dielectric 10' in the form of a relatively flat
1o cube: A probe insertion opening 21 is formed into one surface of
the phantom 2 and extends close to the opposite surface 2a. An
electromagnetic field probe 1 is inserted into and secured iw the
inner end of the probe insertion opening 21, thus constructing an
absorbed power measuring assembly 7. Securing the
15 electromagnetic field probe 1 may take place, for example, by way
of the adhesive 14 as illustrated in Fig. 7A.
A radio transmitter 3 is disposed in proximity to the
location of the electromagnetic field probe 1 within the phantom 2,
and a scan takes place by a scan mechanism 100 while the radio
Zo transmitter 3 is disposed opposite to the phantom 2. In the
example shown in Fig. 18, the radio transmitter 3 is disposed close
to and in parallel relationship with the surface 2a of the phantom 2
which is located close to the probe 1 while an antenna 5 of the radio
transmitter 3 such as a mobile telephone extracts from a casing 3a.
25 The radio transmitter 3 is mounted so that the casing 3a is held
gripped by a retainer 4.
The scan mechanism 100 may comprise drive screws 121,
122 extending along a pair of parallel sides of a rectangular
CA 02550158 2002-08-08
24
frame-shaped base 110, for example, and rotatably mounted by four
supports 111. Similarly, drive screws 123, 124 are rotatably
mounted by the supports 111 on the other pair of parallel sides. A
support bar 131 which extends parallel to the drive screws 121, 122
is formed with threaded holes at its opposite ends, which are
threadably engaged with the drive screws 121, 122. Also, a
support bar 132 which extends parallel to the drive screws 123, 124
is formed with threaded holes at its opposite ends, which are
threadably engaged with the drive screws 123, 124. The support
bars 131 and 132 are slightly offset from each other in a direction
perpendicular to the surface of the phantom 2 which is disposed
opposite to the radio transmitter.
As shown in Fig. 18B, pairs of opposing, inverted
L-shaped engaging peaces 141 a and 141 b, 141 c and 141 d, 142a and
142b, and 142c and 142d are fixedly mounted on the surface 4a of
the retainer 4 which is disposed opposite from the phantom 2, and
the support bar 131 passes between the pairs of engaging pieces
141 a and 141 b and 141 c and 141 d so as to be slidable between the
ends of these engaging pieces and the surface 4a of the retainer 4.
2o In the similar manner, the support bar 132 is passed between the
pairs of engaging pieces 142a and 142b and 142c and 142d so as to
be slidable. However, it is to be noted that the support bar 132 has
its opposite lateral edges received in grooves formed in the ends of
the engaging pieces 142a-142d, whereby its movement in a
2s direction perpendicular to the surface 4a of the retainer is restricted.
An arrangement is made such that the drive screws 121,
122 can be driven for rotation in forward and reverse directions by a
controller I51 including a motor for example, and the drive screws
l
CA 02550158 2002-08-08
123, 124 can be driven for rotation in forward and reverse directions
by a similar controller 152. An absorbed power measuring
assembly 7 is mounted on a support 160 which is secured to the base
110 so that the surface 2a of the phantom 2 is disposed close to and
opposite to the radio transmitter 3 which is retained by the retainer
4.
Accordingly, when the drive screws 121, 122 rotate, the
support bar 131 moves along the screws 121, 122 depending on the
direction of rotation thereof, whereby the radio transmitter 3 also
1o moves in the same direction. When the drive screws 123, I24
rotate, the support bar 132 moves along the screws 123, 124
depending on the direction of rotation thereof, whereby the radio
transmitter 3 also moves in the same direction. Thus, by
controlling the controllers 151, 152, a two-dimensional scan of the
is probe 1 relative to the radio transmitter 3 can take place, as
indicated by a locus 6 which is shown offset in this Figure. For
example, the two-dimensional scan is capable of measuring the
power absorbed from the radio wave over the entire surface 2a of
the phantom 2 while the antenna feed point 3b of the radio
2o transmitter 3 is disposed opposite to the probe 1. Fig. 19
illustrates by way of example that an area 9, shown hatched, over
the surface 2a of the phantom 2 can be measured relative to the
radio transmitter 3. It is to be noted that what is measured by the
electromagnetic field probe 1 is values on the locus of scan 6, and
25 values in interstices S between adjacent scan lines are interpolated
from adjacent measured values. In order to reduce the time of
measurement, rather than using a continuous measurement, the
measurement takes place at an interval on the scan line, and values
CA 02550158 2002-08-08
26
in the interval are interpolated from adjacent measured values.
The spacing between the adjacent scan lines may be chosen on the
order of 1 cm, for example. The range of measurement (area) 9 is
preferably a rectangular range which is determined by the
longitudinal length (inclusive of the antenna length) and the lateral
length of the radio transmitter 3.
The phantom 2 used may comprise an enclosed vessel 11
which is configured in the similar manner as shown in Fig. 18A and
which is formed with a probe insertion opening 21, into which a
liquid medium 10 is filled, as shown in Fig. 20.
The scan mechanism 100 allows a two-dimensional scan
of the absorbed power measuring assembly 7 relative to the radio
transmitter, and accordingly, the power absorbed from the radio
wave by each part of the human body which corresponds to the
phantom 2, can be measured with a high positional accuracy. In
addition, a result which is similar to a result of measurement
according to the measuring technique shown in Fig. 1 in which th.e
probe 1 is moved for purpose of scan is obtained and the likelihood
that the response of the liquid medium 10 may be changed due to the
2o evaporation is avoided with the phantom 2 which uses the liquid
medium 10. The scan mechanism 100 is not limited to the example
described above, but a variety of X~Y drive mechanism may be
used:
As -shown in Fig. 21, a plurality of electromagnetic field
probes 1 are fixedly mounted in a linear array within a phantom 2.
A moving scan of a.radio transmitter 3 obtains a range of
measurement shown in Fig. 19 with a stroke corresponding to a
spacing S 1 between the electromagnetic field probes 1 in the
CA 02550158 2002-08-08
27
direction of the array of the electromagnetic field probes 1. In Fig.
21, the probes 1 are arrayed in a direction parallel to the lengthwise
direction of the radio transmitter 3, but may be arrayed in a
direction perpendicular to the lengthwise direction.
s As shown in Fig. 22, a plurality of electromagnetic field
probes 1 may be arrayed in a matrix in a plane which is close to the
surface 2a of a phantom 2. In this instance, a measurement over
the range shown in Fig. 19 can be obtained by scanning in one
direction of the array of the electromagnetic probes 1 through a
Zo stroke corresponding to a spacing S 1 and scanning in the other
direction of the array through a stroke corresponding to a spacing
52. Again, a value or values located between measuring points are
interpolated from adjacent measured values. In consideration of
these, the number of probes 1 which are disposed within the
is phantom 2 is contemplated to be from I to the order of 10, and the
spacing between the probes are preferably S 1=S2=20mm or so.
With the arrangement shown in Fig. 21, the scan stroke is
shorter than in the example shown in Fig. 18, and the measurement
can be completed in a shorter time interval and a scan mechanism
20 100 can be constructed in a compact form. With the embodiment
shown in Fig. 22, the time interval of measurement can be made
shorter and the scan mechanism can be constructed in a smaller size.
As indicated in Fig. 23, when a radio transmitter 3 is
brought to a position A during a moving scan or when the majority
2s of the radio transmitter 3 is located opposite to a phantom 2, the
radiation characteristics of the radio transmitter 3 is strongly
influenced by the phantom 2, but at position B or when a significant
portion of the radio transmitter 3 is not disposed opposite to the
CA 02550158 2002-08-08
28
phantom 2 or misaligned therewith, the radiation characteristics of
the radio transmitter 3 is influenced by both the phantom 2. and the
air.
In consideration of this, as illustrated in Fig. 24, the
s configuration of a phantom 2 may be chosen to be in the form of a
flat plate having an infinity size as seen by a radio transmitter 3,
with the radio transmitter 3 disposed opposite to a central portion of
one surface of the plate-shaped phantom. 2. In this manner, the
influence of the phantom upon the radiation characteristics of the
radio transmitter 3 can be made substantially uniform at any
position of the radio transmitter 3 during its moving scan. When
part of the human body which is located close to the radio
transmitter 3 is more planar and its area is greater, the absorption of
the radio wave occurs more strongly. Accordingly, when an
15 absorbed power measuring apparatus is constructed in the manner
shown in Fig. 24, a maximum value evaluation can be made. In
order for the phantom 2 to be viewed by the radio transmitter 3 as
having an infinity size, its length L 1 as measured in the direction in
which an antenna S extends should be equal to or greater than 0.6~,,
2o its length L2 in a direction perpendicular to the antenna S should be
equal to or greater than 0.5~,, and its thickness L3 should be equal to
or greater than 0.3~, where ~, represents the wavelength of a radio
wave transmitted from the radio transmitter 3.
The phantom 2 may be one which simulates respective
2s part of an actual human body as illustrated in Figs. 7, I6 and 17 or
one which employs an geometrically simple configuration.
However, it is not necessary that the volume of the phantom 2 be
equal to the volume of a corresponding part of the human body. In
CA 02550158 2002-08-08
29
any event, the measurement takes place by a moving scan of the
absorbed power measuring assembly 7 and .the actual line
transmitter 3 relative to each other using the scan mechanism 100
shown in Fig. 18 or the like, for example.
The use of a belt conveyor in a scan mechanism 100 is
illustrated in Fig. 25. A belt conveyor 31 is maintained
substantially horizontal across its width and runs substantially
horizontally. A drive mechanism for the belt conveyor 31 is nat
shown in the drawing. A phantom 2 as mounted on a support 160
to is fixedly mounted over the belt conveyor 31. The surface 2a of
the phantom 2 which is located close to a probe 1 is disposed
opposite to the belt conveyor 31 with a spacing D1 with respect to
the top surface of the belt conveyor 31. The radio transmitter 3 is
placed on the belt conveyor 31 so that its lengthwise direction
extends in the crosswise direction of the belt conveyor 31 and the
direction of thickness of a casing 3a extends perpendicular to the
top surface of the belt conveyor 31. Substantially the entire length
of the radio transmitter 3 passes under the phantom 2, and the
spacing D1 is chosen so that the surface 2a of the phantom 2 is
2o disposed as close to the radio transmitter 3 as possible.
The radio transmitter 3 is placed on an upstream portion
of the belt conveyor 31, and as the radio transmitter 3 passes under
the phantom 2, a linear scan takes place between the radio
transmitter 3 and an absorbed power measuring assembly 7, thus
enabling a measurement. With this arrangement, when radio
transmitters 3 are successively placed on the belt conveyor 31, a
measurement of the power absorbed by the phantom 2 can be
automatically made for a number of radio transmitters 3.
CA 02550158 2002-08-08
As shown in Fig. 26, when a plurality of electromagnetic
field probes I are disposed within a phantom 2 as an array in a
crosswise direction of the belt conveyor 3 l, merely placing a radio
transmitter 3 on the belt conveyor 31 allows a range of measurement
of absorbed power can be extended to a two-dimensional plane. In
addition, as shown in Fig. 27, when a plurality of electromagnetic
field probes 1 are disposed as an oblique array with respect to the
crosswise direction of the belt conveyor 31, the electromagnetic
field probes 1 can be kept far away from each other. This allows a
reduction in the equivalent dielectric constant and the conductivity
of the phantom 2 under the influence of the probe insertion opening
21 which is used to secure the electromagnetic field probe 1 to be
alleviated. In this instance, a phantom 2 in the form of.a flat plate
has an infinity size as viewed from the radio transmitter 3, thus
preventing the radiation characteristics of the radio transmitter 3
and the antenna reflected power from changing as long as the radio
transmitter 3'is disposed opposite to the phantom 2.
As shown in Fig. 28, a plurality of phantoms 2, which rnay
be three in number, having an identical configuration and formed of
2o an identical material are fixedly mounted as an array in a direction
in which a belt conveyor 31 runs. However, an electromagnetic
field probe 1 is fixedly mounted in each phantom 2 at a mutually
different position as viewed in the crosswise direction of the belt
conveyor 31. In this instance, the phantom 2 has a size which
2s corresponds to a part of the human body. For example, the
phantom 2 shown in Figs. 2, I8A and 20 may be used. In this
manner, measured values from the two-dimensional scan include
contributions of configuration of the part of the human body while
CA 02550158 2002-08-08
31
the response of each phantom 2 is little influenced by the
electromagnetic field probes 1. The shift of position of the
electromagnetic field probes 1 between different phantoms 2 may be
chosen in the running direction rather than in the crosswise
s direction of the belt conveyor, or may be chosen in any other
suitable manner.
As shown in Fig. 29, a plurality of phantoms 2, which may
be three in number, for example, having an identical configuration
and formed with an identical material may be fixedly mounted as an
1o array in the running direction of the belt conveyor 31, and an
electromagnetic field probe 1 is mounted at the same position, for
example, at the center of each phantom 2. As the belt conveyor 31
runs, each radio transmitter 3 is subject to the measurement of
absorbed power by three absorbed power measuring assemblies 7
~s under the same condition. A mean value of a plurality of measured
values for each radio transmitter 3 may be chosen to define the
power absorbed from the radio wave from this radio transmitter 3;
or a maximum value among a plurality of measured values for each
radio transmitter 3 may be chosen to define the power absorbed
2o from the radio wave from this radio transmitter 3. The process of
determining such a mean value or a maximum value takes place in
the calculation and display unit 80 shown in Fig. 7.
In an example shown in Fig. 30, a position sensor S1 is
mounted on a phantom 2 in order to improve the accuracy of
2~ measuring position. The position sensor 51 is mounted on the
phantom 2 so that its position relative to the probe 1 can be defined,
thus detecting whether or not the position sensor 51 is located
opposite to a radio transmitter 3. The position sensor 51 detects
CA 02550158 2002-08-08
32
whether or not it is located opposite to the radio transmitter 3 by
radiating an infrared pulse beam in a direction perpendicular to the
surface 2a of the phantom 2, for example, and determining a time
interval until a reflected infrared pulse is received or the strength of
the reflected infrared pulse. As a scan mechanism performs a
two-dimensional moving scan of the radio transmitter 3, each point
where the radio transmitter 3 has been detected can be plotted,
whereby the configuration of the radio transmitter, 3 which opposes
the phantom 2 is detected. Since the relative position between the
1o probe 1 and the position sensor S 1 in a plane parallel to the scan
plane is fixed and is previously known, the position of each
measuring point of the probe 1 with respect to the configuration of
the detected radio transmitter 3 can be determined, and when the
configuration of the radio transmitter 3 is determined with a high
accuracy, the position of the measuring point of the probe I can be
determined with a corresponding accuracy.
When the belt conveyor 31 shown in Fig. 25 is used as the
scan mechanism, running the belt conveyor 31 at a constant speed
and placing radio transmitters 3 on the belt conveyor 31 at a given
2o time interval allows the time to be determined when a particular
radio transmitter 3 reaches the position of the probe 1, by dividing
the distance between the position where the radio transmitter 3 is
placed on the belt conveyor 31 and the absorbed power measuring
assembly 7 by the running speed of the belt conveyor 31. In this
2s instance, if the position sensor 51 is also used in the absorbed power
measuring assembly 7 as shown in Fig. 30, the measuring position
of the probe 1 relative to the radio transmitter 3 can be correctly
determined by detecting the arrival of the radio transmitter 3 by the
CA 02550158 2002-08-08
33
position sensor S I, if the position where the radio transmitter 3 is
placed on the belt conveyor 31 is misaligned or the time interval to
place it is offset.
As shown in Fig. 31, by disposing the position sensors S 1
s so as to surround the probe 1, the positional relationship between
the radio transmitter 3 and the probe 1 can be determined with a
better accuracy.
Fig. 32 shows an exemplary construction in which an
absorbed power measuring assembly 7 and a scan mechanism 100
are enclosed in a radio anechoic box 41. With this construction, it
is possible to prevent an electromagnetic field probe 1 from
detecting undesired radio waves and to prevent a leakage of the
radio wave radiated by a radio transmitter 3 to the exterior.
When the scan mechanism is constructed with the belt
15 conveyor 31, a pair of opposing walls of the radio anechoic box 41
are formed with openings 4 i a, 41 b in opposing relationship so as to
pass the belt conveyor 31 therethrough, and metal tubes 42a, 42b are
mounted to connect with the openings 41a, 4Ib, as shown in Fig. 33.
Th.e openings of the tubes 42a, 42b are chosen so that their cut-off
2o frequency is higher than the frequency of the radio wave radiated
from the radio transmitter 3 within the radio anechoic box 41, thus
preventing the radio wave from the radio transmitter 3 from passing
through the tubes 42a, 42b. Alternatively, cloths 43a, 43b woven
with metal are attached to the upper edges of the openings 41 a, 41 b
25 of the radio anechoic box 4I to hang therefrom, as shown in Fig. 34,
thus causing the cloths 43a, 43b to be forced out of the way by the
radio transmitter 3 as it passes through the openings 41 a, 41 b.
A phantom using the liquid medium 10 as well as the solid
CA 02550158 2002-08-08
34
dielectric 10' may be used also in the embodiments shown in Figs.
21 to 34. It is also desirable according to the second invention that
the probe 1 be disposed within 20mm from the surface 2a of the
phantom which faces the radio transmitter 3.
