United States Patent c19J
`Johnston et al.
`
`[54] COMPACT DIVERSITY A1''TENNA WITH
`WEAK BACK NEAR FIELDS
`
`[75]
`
`Inventors: Ronald H. Johnston. Calgary; Laurent
`Joseph Levesque. Winnipeg. both of
`Canada
`
`[73] Assignee: Telecommunications Research
`Laboratories, F.dmonton. Canada
`
`[21] Appl. No.: 551,547
`
`Nov. 1, 1995
`
`[22] Filed:
`Int. CI.6
`········---············ ................ H0lQ 1/24
`[51]
`[52] U.S. Cl . ........................... 343no2; 343n42; 343/846
`[58] Field of Search · · · · - - - - 343n02. 700 MS.
`343/741. 742. 846. 848. 841. 725. 727.
`729. 789. 797. 866
`
`[56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2,897,496
`3,036,301
`3,172,111
`3,475,756
`4,217,591
`4,611,212
`4,684,953
`5,075,820
`
`7/1959 Woodward, Jr ......................... 343/818
`5/1962 Wiesner _ _ _ _ .......... 343/100
`3/1965 BreelZ - - - - -............. 343/730
`10/1969 Martino ...............••........•..•.....• 343/743
`8/1980 Czerwinski ........•.•....•....•••...... 343/713
`9/1986 Lee .......................................... 343/351
`8/1987 Hall ··----······· .......... 343/725
`12/1991 Juskey et al ..................... 343/700 MS
`
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`
`2/1986 Canada .... ·---············ 351/60
`1201200
`2278500 11/1994 United Kingdom
`343n94
`
`OTHER PUBLICAl'IONS
`
`Fundamentals of Diversity Systems, W.C. Jakes. Y.S. Yeh.
`M.J. Gans. and D.O. Reudink. Microwave Mobile Commu(cid:173)
`nications. IBEE Press. pp. 309-329. 1994.
`Combining Technology. Lee. W.C.Y .• Mobile Communica(cid:173)
`tions Engineering. McGraw-Hill. pp. 291-318. 1982.
`Energy Reception for Mobile Radio. by E.N. Gilbert. BSTJ.
`vol. 44. pp. 1779-1803, Oct .• 1965.
`
`11■11111111111111
`5,784,032
`Jul. 21, 1998
`
`US005784032A
`c111 Patent Number:
`[451 Date of Patent:
`
`Effects of System RF Design on Propogation. Lee. W.C.Y..
`Mobile Communications Engineering. McGraw-Hill. pp.
`159-163.
`A Comparison of Switched Pattern Diversity Antennas. Tim
`Aubrey and Peter White. Proc. 43rd IBEE Vehicular Tech(cid:173)
`nology Conference, pp. 89-92. 1993.
`A Survey of Diversity Antennas for Mobile and Handheld
`Radio. Johnson. R.H .. Proc. Wireless 93 Conference. Cal(cid:173)
`gary. Alberta. Canada. pp. 307-318, Jul.. 1993.
`A Flat Energy Density Antenna System for Mobile Tele(cid:173)
`phone. Hiroyuki Arai. Hideki Iwashita. Nasahiro Toki. and
`Naohisa Goto, IBEE Transactions on Vehicular Technolo(cid:173)
`gies. vol. Vf40. No. 2. pp. 483-486. May 1991.
`A Multiport Patch Antenna For Mobile Communications.
`R.G. Vaughan and J.B. Andersen. Proc. 14th European
`Microwave Conference. pp. 607-612. Sep. 1984.
`Small Antennas. Harold A Wheeler. IBEE Transactions on
`Antennas and Propagation. vol. AP-23. No. 4, pp. 462-469
`(Fig. 12). Jul. 1975.
`Radiowave Propagation and Antennas for Personal Com(cid:173)
`munications. Siwiak. K. pp. 228-245. Artech House. 1995.
`EM Interaction of Handset Antennas and a Human in
`Personal Communications, Michael A. Jensen. Yahya Rah(cid:173)
`mat-Samil. Proc. IBEE. vol. 83. No. 1. pp. 7-17. Jan .. 1995.
`
`Primary Examiner-Donald T. Hajec
`Assistant Examiner-Tan Ho
`Attome_)I Agent, or Firm-Anthony R. Lambert
`ABSTRACT
`
`[57]
`
`A compact diversity antenna is presented consisting of two
`electrically isolated orthogonal loop conductors joined at a
`midpoint. 'Ihls midpoint is also electrically attached to a
`vertical conductor which produces a third mode of operation
`electrically isolated from the first modes. The two horizontal
`conductors and the vertical conductor may be constructed to
`have various relationships with a ground plane of various
`shapes and sizes. Some of the possible feed arrangements for
`each of the antennas is presented as well as matching and
`tuning circuits. All three antenna elements are found to have
`relatively weak near electric and magnetic fields on the
`ground plane side of the antenna where the ground plane is
`small in extent This feature provides for reduced radiation
`into the head and neck of the cellular phone user.
`
`65 Claims, 13 Drawing Sheets
`
`rlO
`J.
`
`14
`
`11
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`
`U.S. PATENT DOCUMENTS
`
`9/1992 Nishikawa .............................. 343nl3
`5,146,232
`5,173,715 12/1992 Rodal et al ............................. 343n97
`2/1993 Bitter, Jr ................................. 343/702
`5,185,611
`
`5,231,407
`5,291,210
`5,325,403
`5,338,896
`5,392,054
`5,521,610
`
`7 /1993 McGirr et al. .................. ...... .. 343/702
`3/1994 Nakase ............................. 343/700 MS
`6/1994 Siwiak et al ........................... 375/100
`8/1994 Danforth ................................. 343/841
`2/1995 Bottomley et al. ..................... 343/702
`5/1996 Rodal ...................................... 343/797
`
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`U.S. Patent
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`Jul. 21, 1998
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`Sheet 1 of 13
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`5,784,032
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`z
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`flO
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`14
`
`FIGURE
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`22
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`24
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`2
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`U.S. Patent
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`Jul. 21, 1998
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`Sheet 2 of 13
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`5,784,032
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`41
`42
`
`S4
`SI
`S2
`
`FIGURE 4
`
`FIGURE S
`
`FIGURE 6
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`FIGURE 8
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`U.S. Patent
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`Jul. 21, 1998
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`Sheet 3 of 13
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`5,784,032
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`U.S. Patent
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`Jul. 21, 1998
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`Sheet 4 of 13
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`5,784,032
`
`z
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`U.S. Patent
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`Jul. 21, 1998
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`Sheet 5 of 13
`
`5,784,032
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`U.S. Patent
`
`Jul. 21, 1998
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`Sheet 6 of 13
`
`5,784,032
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`U.S. Patent
`
`Jul. 21, 1998
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`Sheet 7 of 13
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`5,784,032
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`U.S. Patent
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`Jul. 21, 1998
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`Sheet 8 of 13
`
`5,784,032
`
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`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 9 of 13
`
`5,784,032
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`U.S. Patent
`
`Jul. 21, 1998
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`Sheet 10 of 13
`
`5,784,032
`
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`U.S. Patent
`
`Jul. 21, 1998
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`Sheet 11 of 13
`
`5,784,032
`
`MATCHING
`TUNING
`
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`U.S. Patent
`
`Jul. 21, 1998
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`Sheet 12 of 13
`
`5,784,032
`
`TUNING/
`MATCHJNG
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`U.S. Patent
`
`Jul. 21, 1998
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`Sheet 13 of 13
`
`5,784,032
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`112
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`5.784.032
`
`1
`COMPACT DIVERSITY ANTENNA WITH
`WEAK BACK NEAR FIELDS
`
`FIELD OF THE INVENTION
`This invention relates to diversity antennas that can
`simultaneously receive or transmit two or three components
`of electromagnetic energy.
`
`BACKGROUND OF THE INVENTION
`Antenna diversity is especially useful for improving radio
`communication in a multipath fading environment. Sporadic
`deep fades occur ( especially in an urban or inbuilding
`environment) on a radio channel leading to signal loss.
`Without diversity. power levels must be maintained suffi(cid:173)
`ciently high to overcome these deep fades. Antenna diversity
`may be used to produce low correlation radio channels
`which produce signal amplitudes that are statistically inde(cid:173)
`pendent. The probability of simultaneous deep fades on
`uncorrelated channels is relatively low. When a deep signal
`fade occurs on one channel, signal degradation or loss can
`usually be avoided by switching to another channel.
`Consequently, signal reliability can be improved, and power
`requirements can be reduced while maintaining signal reli(cid:173)
`ability by using antenna diversity. The improvements in
`signal strength with various diversity antenna combining
`techniques are quantified by authors such as W. C. Jakes,
`Editor. Microwave Mobile Communications, IEEE Press.
`pp. 309-329.1994. and W. C. Y. Lee. Mobile Communica(cid:173)
`tions Engineering. McGraw-Hill. pp. 291-318. 1982.
`Increasing the number of diversity channels improves
`signal reliability and lowers the transmitter power require(cid:173)
`ment. However, as the number of diversity channels is
`increased, the incremental improvement decreases with each
`additional diversity channel. For instance, two-way diversity
`offers a significant improvement over a single channel.
`Three-way diversity offers a significant improvement over
`two-way diversity. although the incremental improvement is
`not as great. At higher diversity levels, i.e., greater than 5,
`the signal improvement is generally not significant when
`weighed against the additional complexity of the switching
`and control circuitry. Three-way diversity can significantly
`improve signal to noise ratio over two-way diversity. but
`neither are widely used, largely, it is believed, due to a lack
`of antennas with suitable compactness, bandwidth and rug(cid:173)
`gedness.
`There are several types of antenna diversity. Angle diver(cid:173)
`sity involves the use of elemental antennas with narrow
`beams that point in slightly different directions. Sufficient
`angle separation between the elemental antennas produces
`low correlation channels. Space diversity involves separat(cid:173)
`ing antennas by a sufficient distance (horizontally or
`vertically) to produce low correlation channels. These two
`methods have the disadvantage of requiring separate anten(cid:173)
`nas and are generally not physically compact.
`Polarization diversity involves having elemental antennas
`for independently receiving separate polarizations of the
`electromagnetic wave. Channels may exhibit sensitivity to
`the polarization of the transmitted electromagnetic wave.
`E. N. Gilbert, "Energy Reception for Mobile Radio",
`BSTJ, vol. 44, pp. 1779-1803, October 1965, and W. C. Y.
`Lee. Mobile Communications Engineering, McGraw-Hill,
`pp. 159-163. 1982 have proposed a field diversity antenna
`where three individual antennas are sensitive to Hx, Hy and
`Ez field which are all vertically polarized. Pattern diversity
`uses broad radiation patterns of elemental antennas to
`receive or transmit into wide angles but each elemental
`
`2
`antenna has a different arrangement of nulls to suppress
`multipath fading effects. Pattern. polarization and field
`diversity methods are probably the most promising for
`producing compact diversity antennas. T. Auberey and P.
`s White, "A comparison of switched pattern diversity
`antennas". Proc. 43rd IEEE Vehicular Technology
`Conference. pp. 89-92. 1993. have shown that the Hx. Hy
`and Ez field diversity antenna has very similar performance
`to the three way pattern diversity with patterns of sin 4>. cos
`10 4> and omni.
`It has recently been shown that standard cell phone
`antennas deposit between 48% and 68% of transmitter
`output energy into the head and the hand of the user. M. A.
`Jensen and Y. Rahmat-Samii. "EM Interaction of Handset
`15 Antennas and a Human in Personal Communications". Proc.
`IEEE. Vol. 83. No. L pp. 7-17. January. 1995.
`This deposition of electromagnetic energy (into the head
`especially) raises health and legal issues and it also removes
`EM power from the communications channel. It therefore
`20 behooves the antenna designer to find methods for reducing
`this electromagnetic energy deposition into the head of a cell
`phone user.
`A moderate number of diversity antennas are discussed in
`the literature as reviewed by R. H. Johnston, "A Survey of
`25 Diversity Antennas for Mobile and Handheld Radio". Proc.
`Wireless 93 Conference. Calgary, Alberta. Canada. pp.
`307-318, July 1993.
`Three of the antennas discussed in that paper should be
`30 considered in relation to the three way diversity antenna
`being presented here. These are:
`The crossed loop antenna of E. N. Gilbert. "Energy
`Reception for Mobile Radio" BSTJ, vol. 44. pp. 1779-1803,
`October 1965. and W. C. Y. Lee. Mobile Communications
`35 Engineering, McGraw-Hill. pp. 159-163, 1982, responds to
`the Hx. Hy and Ez radiation fields. The antenna requires
`three hybrid transformers which introduce circuit complex(cid:173)
`ity and signal power loss and the antenna requires a large
`ground plane. The issue of antenna efficiency. impedance
`40 matching and bandwidth are not effectively addressed.
`The slotted disk antenna of A. Hiroyaki. H. Iwashita, N.
`Taki, and N. Goto, "A Hat Energy Diversity Antenna
`System for Mobile Telephone", IEEE Transactions on
`Vehicular Technologies, Vol. VT40, no. 2, pp. 483-486. May
`45 1991, also responds to the Hx, Hy and Ez fields and is an
`innovative and complete design with a diameter of about
`0.6A. and a height of about 0.05A. and has bandwidths of 10%
`and 6%. The antenna has an interelemental antenna isola(cid:173)
`tions of 10 dB. This antenna is the smallest antenna presently
`50 available but even smaller sized antennas and greater inter(cid:173)
`elemental antenna isolations are required in many cellular
`radio applications.
`The multirnode circular patch antenna by R. G. Vaughan
`and J. B. Anderson. "A Multiport Patch Antenna for Mobile
`ss Communications", Proc. 14th European Microwave
`Conference. pp. 607-612. September 1984, provides
`approximately a sin 4>. cos 4> and omni radiation pattern but
`the antenna is fairly large and the isolation is only about 10
`dB. The antenna is a rnicrostrip patch design which is
`60 inherently narrow band for a reasonable dielectric thickness.
`H. A. Wheeler. in a paper entitled "Small Antennas".
`IEEE Transactions on Antennas and Propagation". Vol.
`AP-23. no. 4. pp. 462-469(FIG. 12). July 1975. discusses a
`structure which has an appearance similar to one of the
`65 embodiments seen later in this patent application. It shows
`an open top shallow square box with cross conductors across
`the top. Wheeler indicates that this antenna has good band-
`
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`5,784,032
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`3
`width for its size and it may be operated in two modes. He
`does not note that this can provide diversity operation and he
`does not note the possibility of the third vertical elemental
`antenna which produces another mode of operation.
`The standard antennas used on handheld cellular radio
`telephones are the electric monopole mounted on a conduc(cid:173)
`tive box and single and double PIFA (Planar inverted F
`antennas) and BIFA (Bent inverted F antennas) mounted on
`conductive boxes. Recent analytical work on these antennas
`indicate that these various antennas deposit between 48% 10
`and 68% of the total output power into the head and the hand
`of the user. M. A. Jensen and Y. Rahm.at-Samii. "EM
`Interaction of Handset Antennas and a Human in Personal
`Communications". Proc. IEEE. Vol. 83. No. 1. pp. 7-17.
`January. 1995.
`
`4
`In a further aspect of the invention. at least each of the first
`and second antenna elements create a reactance in use and
`the invention further includes means integral with each of
`the first and second antenna elements for tuning out the
`reactance of the respective first and second antenna ele(cid:173)
`ments.
`In a further aspect of the invention. each means for tuning
`out the reactance of the first and second antenna elements
`includes a capacitative element matching the respective one
`of the first and second antenna elements to a given imped(cid:173)
`ance.
`In a further aspect of the invention. the feed means for
`each antenna element forms a transmission line connected to
`the respective antenna elements at the intersection of the
`15 antenna elements.
`In a further aspect of the invention. the feed means
`includes. for each antenna element, a conducting microstrip
`capacitatively coupled to the antenna element.
`In a further aspect of the invention, the first and second
`20 antenna elements are each formed of first and second
`conducting strips spaced from each at the intersection of the
`first and second antenna elements; and the conducting
`microstrip of each antenna element connects to one of the
`first and second conducting strips and extends along and
`25 spaced from the other of the first and second conducting
`strips.
`In a further aspect of the invention. the feed means for
`each antenna element is a coaxial transmission line in which
`an outer conductor is continuously connected to a portion of
`30 the antenna element.
`In a further aspect of the invention. the feed means
`includes a first feed point on the first antenna element. a
`second feed point on the second antenna element. a source
`of electrical energy. and a splitter connected to the source of
`35 electrical energy and to the first and second feed points to
`provide equal anti-phasal currents to the respective first and
`second feed points.
`In a further aspect of the invention. there is provided a
`mobile phone transceiver comprising a housing. a radio
`40 transceiver disposed within the housing. the radiotransceiver
`including a microphone on one side of the housing; and an
`antenna having means forming a ground plane with a weak
`near field on a first side of the antenna. and antenna elements
`on a second side of the antenna. the antenna being oriented
`45 with respect to the housing such that when the microphone
`is in position close to the mouth of a mobile phone user the
`first side of the antenna is closer to the head of the user than
`the second side of the antenna.
`These and other aspects of the invention will now be
`50 described in more detail and claimed in the claims that
`follow.
`BRIEF DESCRIPTION OF THE DRAWINGS
`There will now be described preferred embodiments of
`55 the invention. with reference to the drawings. by way of
`illustration. in which like numerals denote like elements and
`in which:
`FIG. 1 is a schematic showing arrangement of two mag(cid:173)
`netic loops and one electric monopole according to an aspect
`of the invention;
`FIG. 2 is a schematic showing an embodiment of loop
`conductors lying on the surface of a spherical shell accord(cid:173)
`ing to an aspect of the invention;
`FIG. 3 is a schematic showing a rectangular conductor top
`65 view embodiment according to an aspect of the invention;
`FIG. 4 is a schematic showing a square ground plane
`according to an aspect of the invention;
`
`SUMMARY OF THE INVENTION
`
`In a broad aspect of the invention. there is therefore
`provided an antenna comprising:
`means forming a ground plane;
`a first antenna element extending in a loop from a first part
`of the ground plane to a second part of the ground
`plane; and
`a second antenna element extending in a loop from a third
`part of the ground plane to a fourth part of the ground
`plane. the second antenna element intersecting the first
`antenna element at an intersection.
`In a further aspect of the invention. a third antenna
`element forming a conducting monopole having a predomi(cid:173)
`nantly Ez field radiation pattern is located at the intersection
`of the first and second antenna elements.
`In a further aspect of the invention. there is provided feed
`means to feed electric signals to the first and second antenna
`elements. The feed means is configured to produce a virtual
`ground at the intersection of the first and second antenna
`elements. thereby providing isolation of the antenna ele(cid:173)
`ments.
`In a further aspect of the invention. the feed means
`provides feed electric signals to the first and second antenna
`elements at the intersection of the first and second antenna
`elements.
`In a further aspect of the invention. the ground plane
`forms a box. the box including a peripheral wall depending
`from the first and second antenna elements and a bottom
`spaced from the first and second antenna elements and
`enclosed by the peripheral wall.
`In a further aspect of the invention. each antenna element
`is formed of strips whose width is greater than their thick(cid:173)
`ness.
`In a further aspect of the invention. the first and second
`antenna elements bisect each other.
`In a further aspect of the invention. the ground plane is
`commensurate in size to the first and second antenna ele(cid:173)
`ments.
`In a further aspect of the invention. each of the first and
`second antenna elements is curved
`In a further aspect of the invention. each of the first and
`second antenna elements form part of a spherical shell.
`In a further aspect of the invention. the ground plane 60
`extends laterally no further than the first and second antenna
`elements.
`In a further aspect of the invention. the first and second
`antenna elements extend between diagonal corners of the
`box.
`In a further aspect of the invention. the first and second
`antenna elements are orthogonal to each other.
`
`Ex.1006
`APPLE INC. / Page 17 of 24
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`5.784.032
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`5
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`25
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`5
`FlG. 5 is a schematic showing a round ground plane
`according to an aspect of the invention;
`FlG. 6 is a schematic showing a diamond shaped ground
`plane according to an aspect of the invention;
`FlG. 7 is a schematic showing a non-symmetrical rect-
`angular ground plane according to an aspect of the inven(cid:173)
`tion;
`FlG. 8 is a schematic showing an embodiment using a
`local sunken ground plane according to an aspect of the
`invention;
`FlG. 9 is a schematic showing an embodiment of a
`cylinder local sunken ground plane according to an aspect of
`the invention;
`FlG. 10 is a schematic showing an embodiment installed
`in a conductive box according to an aspect of the invention; 15
`FlG. 11 is a schematic showing an embodiment on top of
`a rectangular box structure according to an aspect of the
`invention;
`FlG. 12 is a schematic showing detail of electrical feed
`points according to an aspect of the invention;
`FlG. 13 is a schematic showing a signal splitter feed
`arrangement realized by a magic T according to an aspect of
`the invention;
`FlG. 14 is a schematic showing a signal splitter realized
`by a 3 dB Branch line coupler feed arrangement;
`FlG. 15 is a schematic showing 3 dB Splitter Feed
`arrangement according to an aspect of the invention;
`FlG. 16 is a schematic showing a feed arrangement using
`a microstrip line feed according to an aspect of the inven- 30
`tion;
`FlG. 17 is a schematic showing an equivalent circuit of
`the magnetic loop elemental antennas according to an aspect
`of the invention;
`FlG. 18 is a schematic showing a capacitive matching 35
`circuit for the magnetic loop elemental antennas according
`to an aspect of the invention;
`FlG. 19 is a schematic showing a T matching circuit
`according to an aspect of the invention;
`FlG. 20 is a schematic showing a 1t matching circuit 40
`according to an aspect of the invention;
`FlG. 21 is a schematic showing a matching and tuning
`circuit integrated with the loop antenna according to an
`aspect of the invention;
`FlG. 22 is a schematic showing a detail of individual 45
`H-Element electrical feed point according to an aspect of the
`invention;
`FIG. 23 is a schematic showing the relationship of the
`human head, antenna and cellular phone according to an
`aspect of the invention;
`FlG. 24 shows a pie shaped antenna configuration accord(cid:173)
`ing to an aspect of the invention;
`FIG. 25 shows a top view of the embodiment of FIG. 24;
`FIG. 26 shows a top view of a pie shaped antenna
`configuration with diagonalized antenna loops;
`FIG. 27 shows an embodiment of an antenna with diago(cid:173)
`nalized pie shaped antenna elements for sliding over a radio
`transceiver, such as shown in FIG. 23;
`FIG. 28 shows a coaxial feed arrangement for an antenna 60
`element according to an aspect of the invention;
`FIG. 29a is a schematic showing basic components of a
`first embodiment of a radio transceiver according to the
`invention;
`FIG. 29b is a schematic showing basic components of a 65
`second embodiment of a radio transceiver according to the
`invention; and
`
`6
`FIG. 30 is a schematic showing a feed for a monopole
`antenna element for use in the invention.
`DEfAlLED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`The three-way diversity antenna. as realized by orthogo(cid:173)
`nal horizontal conductors and a vertical conductor. in a
`compact configuration. has many advantages over other
`diversity antennas. One embodiment is shown in FIG. 1. The
`basic shape of the antenna 10 is shown without the elemental
`10 antenna feed arrangements. and is formed on a ground plane
`11. The ground plane 11, and the other ground planes shown
`in the figures. is preferably electrically small. namely its
`length. in the longest dimension. should be less than the
`wavelength. and preferably less than half the wavelength,
`for example one-quarter of the wavelength. of the carrier
`frequency of the transceiver the antenna is to be used with.
`The Hx antenna element 12 (aligned in the y direction)
`extends in a loop from spaced apart locations on the ground
`plane 11, provides (when a current passes through it. that is.
`20 when it is in use) a magnetic field in the x direction (Hx)
`which produces a vertically polarized EM wave with
`approximately a sin q, radiation pattern and provides an
`electric field in the y direction, which in turn produces a
`horizontally polarized EM wave with approximately a cos q,
`radiation pattern.
`The Hy antenna element 14 (aligned in the x direction)
`also extends in a loop from spaced apart locations on the
`ground plane 11, and. in use. provides a y directed magnetic
`field (Hy) which produces a vertically polarized EM wave
`with an approximate pattern of cos q, and provides an electric
`field in the x direction (Ex) which produces a horizontally
`polarized EM wave with approximately a sin q, radiation
`pattern.
`This complete angular coverage and polarization cover(cid:173)
`age makes the antenna very suitable for a cell phone and
`personal communication phone as the antenna can have a
`variety of orientations with the user and can have a variety
`of orientations and polarizations with the base station
`antenna. The vertical reactively loaded monopole conductor
`13 produces an electric field in the z direction (E=) that is
`approximately omnidirectional and is vertically polarized.
`The antenna elements 12 and 14 intersect at an intersection
`15, and the monopole 13 connects between the intersection
`15 and the ground plane 11. When these antennas are fed so
`as to preserve physical and electrical symmetry each antenna
`element is highly isolated from the other two antenna
`elements.
`The length of the loop antenna elements should not
`exceed about 'J.J2 and the height of the monopole should not
`exceed about A/4 where A is the wavelength of the carrier
`frequency the antenna is to be used with. The choice of the
`actual dimensions is dictated by the end use, and involved a
`trade off between features well known in the art such as
`efficiency, bandwidth and return loss.
`Good isolation between the antenna elements ensures that
`antenna elements do not affect each other in terms of their
`radiation patterns or input impedance or polarization. The
`outputs from all antenna elements may be directed to
`separate receivers (not shown) without diminishing the
`power available from any other antenna element. This
`allows the antenna elements to be used for switched selec-
`tive combining, equal gain combining and maximal ratio
`combining as discussed by W. C. Jakes. Editor, Microwave
`Mobile Communications. IEEE Press, pp. 309-329. 1994. or
`W. C. Y. Lee, Mobile Communications Engineering,
`McGraw-Hill, pp. 291-318, 1982, or any other combining
`method.
`
`50
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`Ex.1006
`APPLE INC. / Page 18 of 24
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`5.784,032
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`0:o::t:i;:~~ia~ ~~dt;:::~~!e i:in~~~~~ 25
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`7
`8
`a peripheral wall 106 depending from antenna elements 102
`For most cellular radio applications it is desirable to make
`the antenna as small as possible but still achieve the neces(cid:173)
`and 104 and a bottom surface 107 spaced from the antenna
`sary electrical performance. This antenna can be made very
`elements 102 and 104 and enclosed by the peripheral wall
`compactly for a given bandwidth and operating frequency.
`106. The antenna elements 102 and 104 of FIG. 10 are
`Another possible conductor arrangement is shown in FIG. s commensurate in size with the ground plane 107. Preferably.
`2 in which an antenna 20 is formed from a round ground
`the ground plane 107 does not extend any further outward
`plane 21. intersecting loop antenna elements 22 and 24
`than the antenna elements 102 and 104 as shown in FIG. 10.
`forming part of a spherical shell. and monopole 23. Each of
`The conductive box 100 does not need to be square in
`the antenna elements and the ground plane function in much
`cross section but it may have other shapes (such as part of
`the same manner as the configuration of FIG. 1. While the 10
`a spherical or ellipsoid shell) and may be build into the end
`configuration of FIG. 2 provides improved bandwidth using
`of a rectangular box 118 as shown in FIG. 11. The box in
`curved antenna elements. the configuration of FIG. 1 is
`FIG. 11 is formed from sides 116 and bottom 117 with
`easier to make. It is preferred that the antenna elements
`antenna elements 112. 113 and 114.
`bisect each other as shown in FIGS. 1. 2 and 3, and that the
`Each antenna element must accept electrical power from
`antenna elements be orthogonal to each other as shown in
`FIGS. 1. 2 and 3. However. the antenna elements do not need 15
`a transmission line or some other electrical circuit. The feed
`arrangement should satisfy two issues. (1) the physical and
`to be equal in length. As shown in FIG. 3. one antenna
`electrical symmetry of the antenna structure must be main(cid:173)
`element 32 may be shorter than the other antenna element
`tained to retain antenna element isolation and (2) tuning and
`34. such that the antenna elements 32 and 34 have different
`impedance matching between the antenna elements and the
`height to width aspect ratios.
`feed structures minimizes the VSWR and therefore maxi-
`In addition to the variations in the shape of the H antenna
`mizes power transfer from the antenna to receiver or maxi(cid:173)
`element profiles. the antenna elements 12. 13. 14. 22. 23 and
`mizes power transfer from the transmitter to the antenna.
`24 etc may also have different cross-sectional shapes as well
`The feed arrangement can best be illustrated with an
`as widths along the length of the conductor. The cross
`antenna 120 in place on a ground plane 121 with antenna
`elements 122 and 124 as illustrated in FIG. 12. The Hx
`element 122 is driven by feed points FP3 and FP4. These
`feed points must be supplied with equal currents that are
`anti-phasal. essentially 180° out of phase. In this way the
`center point of the cross becomes a virtual ground. thus
`ensuring isolation. No voltage is conveyed to the Hy element
`feed point (FPl and FP2) or to the E: element feed point
`(FPS).
`Voltages may be delivered to feed points 1 and 2 (FPl and
`FP2) with a variety of circuits that are shown in FIGS. 13
`through to 15. The Hx element will have another feed circuit
`which would normally be identical to the Hy element feed.
`Transmission lines 11 leading to the feed points can have a
`length that may be varied to maximize the bandwidth of the
`E. antenna element. The bandwidth of the Ez element is
`sinsitive to the transmission line length 11. The E: element
`achieves best bandwidth when the composite impedance
`looking into the fe