0U
`
`S005784032A
`
`[11]
`
`[45]
`
`Patent Number:
`
`Date of Patent:
`
`5,784,032
`Jul. 21, 1998
`
`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 IEEE Vehicular Tech-
`nology Conference, pp. 89-92, 1993.
`A Survey of Diversity Antennas for Mobile and Handheld
`Radio. Johnson, R.H.. Proc. Wireless 93 Conference. Cal-
`gary, Alberta, Canada. pp. 307-318, Jul., 1993.
`A Flat Energy Density Antenna System for Mobile Tele-
`phone. Hiroyuki Arai. Hideki Iwashita. Nasahiro Toki. and
`Naohisa Goto, TEEE Transactions on Vehicular Technolo-
`gies, vol. VT40. 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, IEFE Transactions on
`Antennas and Propagation, vol. AP-23. No. 4, pp. 462-469
`(Fig. 12), Jul. 1975.
`Radiowave Propagation and Antennas for Personal Com-
`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-
`mat—Samii. Proc. IEEE, vol. 83. No. 1. pp. 7-17. Jan.. 1995.
`
`Primary Examiner—Donald T. Hajec
`Assistant Examiner—Tan Ho
`Attomey, Agent, or Firm—Anthony R. Lambert
`
`[S7]
`
`ABSTRACT
`
`United States Patent 1
`Johnston et al.
`
`(54) COMPACT DIVERSITY ANTENNA WITH
`WEAK BACK NEAR FIELDS
`
`{75]
`
`Inventors: Ronald H. Johnston, Calgary; Laurent
`Joseph Levesque, Winnipeg, both of
`Canada
`
`[73] Assignee: Telecommunications Research
`Laboratories, Edmonton, Canada
`
`[21] Appl. No.: 551,547
`
`[22]
`
`Filed:
`
`Nov. 1, 1995
`
`TSA] Wate, C06 acs cccsscccnesesevsccsnonecrnccscevenessee HO1Q 1/24
`
`(52] U.S. CL 343/702; 343/742; 343/846
`[58] Field of Search.
`.......0...0..-10 343/702. 700 MS,
`343/741, 742, 846. 848. 841. 725. 727,
`729, 789, 797, 866
`
`[56]
`
`References Cited.
`
`U.S. PATENT DOCUMENTS
`
`7/1959 Woodward, Jr... ane 343/818
`2,897,496
` S/1962 Wiesner
`wee 343/100
`3,036,301
`3/1965 Breet
`«. 343/730
`3,172,111
`3,475,756 10/1969 Martino
`we 343/743
`4,217,591
`8/1980 Czerwinski
`ww. 343/713
`4,611,212
`9/1986 Lee .......
`+» 343/351
`4,684,953
`8/1987 Hall ......
`wee GAB/T25
`5,075,820 12/1991 Juskey et ab...scsseessees 343/700 MS
`
`
`
`(List continued on next page.)
`FOREIGN PATENT DOCUMENTS
`
`OTHER PUBLICATIONS
`
`Fundamentals of Diversity Systems, W.C. Jakes. Y¥.S. Yeh.
`M.J. Gans, and D.O. Reudink, Microwave Mobile Commu-
`nications, IEEE Press, pp. 309-329. 1994.
`Combining Technology, Lee. W.C.Y¥., Mobile Communica-
`tions Engineering. McGraw-Hill. pp. 291-318, 1982.
`Energy Reception for Mobile Radio. by EN. Gilbert, BSTJ.
`vol. 44, pp. 1779-1803. Oct., 1965.
`
`A compact diversity antenna is presented consisting of two
`electrically isolated orthogonal loop conductors joined at a
`midpoint. This midpoint is also electrically attached to a
`vertical conductor which producesa third mode of operation
`1201200=2/1986 Cama...sseessssnnnsean
`
`electrically isolated from the first modes. The two horizontal
`
`conductors andthe vertical conductor may be constructed to
`2278500
`11/1994 United Kingdom....
`have various relationships with a ground plane of various
`shapes and sizes. Someof 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
`
`c
`
`IO
`
`f
`
`jy
`
`I]
`
`<r
`
`IS
`
`IZ
`
`SAMSUNG 1005
`
`1
`
`SAMSUNG 1005
`
`

`

`5,784,032
`
`.S. PATENT DOCUMENTS
`
`$146,232
`5,173,715
`5,185,611
`
`9/1992 Nishikawa .....ccscscsssessenseccsseers 343/713
`12/1992 Rodal et al.
`...csesecsssesessseesnes 343/797
`2/1993 Bitter, Jr.
`...sssesssssssessssesneeseeseee 343/702
`
`5 U
`
`5,231,407
`5,291,210
`3,325,403
`5300084
`5,521,610
`
`T1993
`3/1994
`6/1994
`8/1994
`2/1995
`5/1996
`
`MecGirr et al.
`..cccccsneccesnncesee 343/702
`Nakase.........
`. 343/700 MS
`
`Siwiak et al.
`.
`wae 375/100
`Danforth .......scscsssccessoeesereenease 343/841
`Bottomleyet al.
`we 343/702
`Rodal ........c0
`wees 343/797
`
`
`
`2
`
`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 1 of 13
`
`5,784,032
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`7
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`US. Patent
`
`Jul. 21, 1998
`
`Sheet 2 of 13
`
`5,784,032
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`a
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`5,784,032
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`US. Patent
`
`Jul. 21, 1998
`
`Sheet 3 of 13
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`
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`9 F
`
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`
`10
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`FIGURE
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`

`US. Patent
`
`Jul. 21, 1998
`
`Sheet 4 of 13
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`5,784,032
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`
`
`FIGURE
`
` I!2
`
`
`
`FIGURE 3
`
`6
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`

`

`US. Patent
`
`Jul. 21, 1998
`
`Sheet 5 of 13
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`5,784,032
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`
`
`FIGURE [4
`
`
`
`FIGURE 15
`
`7
`
`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 6 of 13
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`5,784,032
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`
`
`FIGURE
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`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 7 of 13
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`5,784,032
`
`OTLs
`
`LiOop
`
`RRAD
`
`FIGURE
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`18
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`
`19
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`FIGURE 20
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`

`

`USS. Patent
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`Jul. 21, 1998
`
`Sheet 8 of 13
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`5,784,032
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`
`
`FIGURE
`
`2l
`
`
`
`FIGURE 22
`
`10
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`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 9 of 13
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`5,784,032
`
`FIGURE 24
`
`252
`
`FIGURE 25
`
`11
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`
`11
`
`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 10 of 13
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`5,784,032
`
`FIGURE 2
`
`
`
`FIGURE 27
`
`12
`
`12
`
`
`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 11 of 13
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`5,784,032
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`YT
`
`V7
`
`W7
`
`MATCHING
`TUNING
`
`MATCHING
`TUNING
`
`304
`
`304
`
`MAT.
`TUNING.
`304
`
`FEED
`LINE
`
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`LINE
`
`FEED
`LINE
`
`302
`
`302
`
`302
`
`SWITCHED SELECTION ComBINeR|}206
`
`CONTROL
`Ry
`
`TZ —LIRANSCEIVER|
`
`308
`
`FIGURE 29A
`
`13
`
`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 12 of 13
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`5,784,032
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`WY
`
`4
`
`VTA
`
`TUNING/
`MATCHING!
`
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`|MATCHING
`
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`MATCHING
`
`304
`
`304
`
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`LINE
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`LINE
`
`302
`
`302
`
`302
`
`COMBINER
`
`TRANSCEIVER
`
`307
`
`309
`
`FIGURE
`
`298
`
`
`
`FIGURE
`
`28
`
`14
`
`

`

`U.S. Patent
`
`Jul. 21, 1998
`
`Sheet 13 of 13
`
`5,784,032
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`
`
`FIGURE
`
`30
`
`15
`
`

`

`5.784,032
`
`1
`COMPACTDIVERSITY ANTENNA WITH
`WEAK BACK NEARFIELDS
`
`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-
`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-
`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-
`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-
`tions Engineering, McGraw-Hill, pp. 291-318, 1982.
`Increasing the number of diversity channels improves
`signal reliability and lowers the transmitter power require-
`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-waydiversity. although the incremental improvementis
`not as great. At higher diversity levels, ic. 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-
`gedness.
`There are several types of antenna diversity. Angle diver-
`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-
`ing antennas by a sufficient distance (horizontally or
`vertically) to produce low correlation channels. These two
`methods have the disadvantage of requiring separate anten-
`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”,
`BSTIJ.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
`Ezfield which are all vertically polarized. Pattern diversity
`uses broad radiation patterns of elemental antennas to
`receive or transmit into wide angles but each elemental
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`55
`
`65
`
`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.
`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 . cos
`@ 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 ofthe user. M. A.
`Jensen and Y. Rahmat-Samii, “EM Interaction of Handset
`Antennas and a Humanin Personal Communications”. Proc.
`TREE, Vol. 83. No. 1. pp. 7-17. January, 1995.
`This deposition of electromagnetic energy (into the head
`especially) raises health and legal issues andit also removes
`EM power from the communications channel. It therefore
`behoovesthe antenna designer to find methods for reducing
`this electromagnetic energy deposition into the headofa cell
`phone user.
`A moderate numberof diversity antennas are discussed in
`the literature as reviewed by R. H. Johnston, “A Survey of
`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
`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
`Engineering. McGraw-Hill. pp. 159-163, 1982, respondsto
`the Hx. Hy and Ez radiation fields. The antenna requires
`three hybrid transformers which introduce circuit complex-
`ity and signal power loss and the antenna requires a large
`ground plane. The issue of antenna efficiency, impedance
`matching and bandwidth are not effectively addressed.
`The slotted disk antenna of A. Hiroyaki, H. Iwashita. N.
`Taki, and N. Goto, “A Flat Energy Diversity Antenna
`System for Mobile Telephone”, IEEE Transactions on
`Vehicular Technologies, Vol. VT40. no. 2. pp. 483-486, May
`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 0.05/ and has bandwidths of 10%
`and 6%. The antenna has an interelemental antenna isola-
`tions of 10 dB, This antenna is the smallest antenna presently
`available but even smaller sized antennas and greaterinter-
`elemental antenna isolations are required in many cellular
`radio applications.
`The multimode circular patch antenna by R. G. Vaughan
`and J. B. Anderson, “A Multiport Patch Antenna for Mobile
`Communications”, Proc. 14th European Microwave
`Conference. pp. 607-612. September 1984, provides
`approximately a sin @, cos @ and omniradiation pattern but
`the antenna is fairly large and theisolation is only about 10
`dB. The antenna is a microstrip patch design which is
`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
`embodiments seenlater 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-
`
`16
`
`16
`
`

`

`5,784,032
`
`4
`In a further aspect ofthe invention, at least each ofthe 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-
`ments.
`
`In a further aspectof the invention. each meansfor tuning
`out the reactance of the first and second antenna elements
`includesa capacitative element matching the respective one
`of the first and second antenna elements to a given imped-
`ance.
`
`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
`telephonesare the electric monopole mounted on a conduc-
`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%
`and 68% of the total output power into the head and the hand
`of the user, M. A. Jensen and Y. Rahmat-Samii, “EM
`Interaction of Handset Antennas and a Human in Personal
`Communications”, Proc. IEEE, Vol. 83, No. 1, pp. 7-17.
`January, 1995.
`
`SUMMARY OF THE INVENTION
`
`there is therefore
`
`20
`
`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
`antenna elements.
`the feed means
`In a further aspect of the invention,
`includes. for each antenna element, a conducting microstrip
`capacitatively coupled to the antenna element.
`In a broad aspect of the invention,
`In a further aspect of the invention. the first and second
`antenna elements are each formed of first and second
`provided an antenna comprising:
`means forming a ground plane;
`conducting strips spaced from each at the intersection of the
`a first antenna element extending in a loop fromafirst part
`first and second antenna elements; and the conducting
`microstrip of each antenna element connects to one of the
`of the ground plane to a second part of the ground
`plane; and
`first and second conducting strips and extends along and
`spaced from the other of the first and second conducting
`a second antenna element extending in a loop from a third
`strips.
`part of the ground plane to a fourth part of the ground
`In a further aspect of the invention, the feed means for
`plane, the second antenna elementintersectingthefirst
`each antenna elementis a coaxial transmission line in which
`antenna elementat an intersection.
`an outer conductor is continuously connected to a portion of
`In a further aspect of the invention. a third antenna
`the antenna element.
`element forming a conducting monopole having a predomi-
`the feed means
`In a further aspect of the invention,
`nantly Ezfield radiation pattern is located at the intersection
`of the first and second antenna elements.
`includes a first feed point on the first antenna element, a
`second feed point on the second antenna element, a source
`In a further aspect of the invention. there is provided feed
`of electrical energy, and a splitter connected to the source of
`meansto feed electric signals to the first and second antenna
`electrical energy and to the first and second feed points to
`elements. The feed means is configured to produce a virtual
`provide equal anti-phasal currents to the respectivefirst and
`ground at the intersection of the first and second antenna
`second feed points.
`elements. thereby providing isolation of the antenna ele-
`ments.
`In a further aspect of the invention, there is provided a
`mobile phone transceiver comprising a housing. a radio
`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
`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 antennais closer to the head of the user than
`the second side of the antenna.
`These and other aspects of the invention will now be
`described in more detail and claimed in the claims that
`follow.
`
`the feed means
`In a further aspect of the invention,
`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-
`ness.
`
`40
`
`50
`
`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-
`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
`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.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`55
`
`65
`
`There will now be described preferred embodiments of
`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 arrangementof two mag-
`netic loops and oneelectric 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-
`ing to an aspect of the invention;
`FIG.3 is a schematic showing a rectangular conductor top
`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;
`
`17
`
`17
`
`

`

`5.784,032
`
`5
`FIG. 5 is a schematic showing a round ground plane
`according to an aspect of the invention;
`FIG.6 is a schematic showing a diamond shaped ground
`plane according to an aspect of the invention,
`FIG. 7 is a schematic showing a non-symmetrical rect-
`angular ground plane according to an aspect of the inven-
`tion;
`FIG. 8 is a schematic showing an embodiment using a
`local sunken ground plane according to an aspect of the
`invention;
`FIG. 9 is a schematic showing an embodiment of a
`cylinder local sunken ground plane according to an aspect of
`the invention;
`FIG. 10 is a schematic showing an embodimentinstalled
`in a conductive box according to an aspect of the invention;
`FIG.11 is a schematic showing an embodiment on top of
`a rectangular box structure according to an aspect of the
`invention;
`FIG. 12 is a schematic showing detail of electrical feed
`points according to an aspect of the invention,
`FIG. 13 is a schematic showing a signal splitter feed
`arrangementrealized by a magic T according to an aspect of
`the invention;
`FIG. 14 is a schematic showing a signal splitter realized
`by a 3 dB Branch line coupler feed arrangement;
`FIG. 15 is a schematic showing 3 dB Splitter Feed
`arrangement according to an aspect of the invention;
`FIG. 16 is a schematic showing a feed arrangementusing
`a microstrip line feed according to an aspect of the inven-
`tion;
`FIG. 17 is a schematic showing an equivalent circuit of
`the magnetic loop elemental antennas accordingto an aspect
`of the invention;
`FIG. 18 is a schematic showing a capacitive matching
`circuit for the magnetic loop elemental antennas according
`to an aspect of the invention;
`FIG. 19 is a schematic showing a T matching circuit
`according to an aspect of the invention;
`FIG. 20 is a schematic showing a m matching circuit
`according to an aspect of the invention;
`FIG. 21 is a schematic showing a matching and tuning
`circuit integrated with the loop antenna according to an
`aspect of the invention;
`FIG. 22 is a schematic showing a detail of individual
`H-Elementelectrical 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;
`FIG. 24 shows a pie shaped antenna configuration accord-
`ing to an aspect of the invention;
`FIG. 25 showsa 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-
`nalized pie shaped antenna elements for sliding over a radio
`transceiver, such as shown in FIG. 23;
`FIG. 28 showsa coaxial feed arrangementfor an antenna
`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. 295 is a schematic showing basic components of a
`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.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`The three-way diversity antenna. as realized by orthogo-
`nal horizontal conductors and a vertical conductor,
`in a
`compact configuration. has many advantages over other
`diversity antennas. One embodimentis shown in FIG. 1. The
`basic shape of the antenna 10 is shown withoutthe elemental
`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 antennais 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.
`whenit is in use) a magnetic field in the x direction (Hx)
`which produces a vertically polarized EM wave with
`approximately a sin
`radiation pattern and provides an
`electric field in the y direction, which in turn produces a
`horizontally polarized EM wave with approximately a cos
`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 > and provides an electric
`field in the x direction (Ex) which produces a horizontally
`polarized EM wave with approximately a sin $ radiation
`pattern.
`This complete angular coverage and polarization cover-
`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 14intersect 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 preservephysical 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 A/2 and the height of the monopole should not
`exceed about 1/4 where A is the wavelength of the carrier
`frequency the antennais to be used with. The choice of the
`actual dimensionsis 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.
`
`10
`
`20
`
`25
`
`35
`
`40
`
`45
`
`30
`
`35
`
`65
`
`18
`
`18
`
`

`

`5.784,032
`
`7
`For mostcellular radio applicationsit is desirable to make
`the antenna as small as possible but still achieve the neces-
`sary electrical performance. This antenna can be made very
`compactly for a given bandwidth and operating frequency.
`Another possible conductor arrangement is shown in FIG.
`2 in which an antenna 20 is formed from a round ground
`plane 21.
`intersecting loop antenna elements 22 and 24
`forming part of a spherical shell. and monopole 23. Each of
`the antenna elements and the ground plane function in much
`the same manner as the configuration of FIG. 1. While the
`configuration of FIG. 2 provides improved bandwidth using
`curved antenna elements, the configuration of FIG. 1 is
`easier to make. It is preferred that the antenna elements
`bisect each other as shown in FIGS.1, 2 and 3, and that the
`antenna elements be orthogonal to each other as shown in
`FIGS. 1. 2 and 3. However. the antenna elements do not need.
`to be equal in length. As shown in FIG. 3, one antenna
`element 32 may be shorter than the other antenna element
`34, such that the antenna elements 32 and 34 havedifferent
`height to width aspect ratios.
`In addition to the variations in the shape of the H antenna
`elementprofiles. the antenna elements 12, 13, 14, 22. 23 and
`24 etc mayalso have different cross-sectional shapes as well
`as widths along the length of the conductor. The cross
`section of the magnetic loops and the monopole conductor
`may be round. elliptical. flat or a cross made out of flat
`conductors. These conductors may also be tapered along
`their length as shown in FIGS. 25-28. This might be useful
`where the physical strength of the antenna could be impor-
`tant in exposed environments. Varying the cross section of
`the conductors may be used to vary the bandwidth and input
`impedance of the antenna.
`Various placements of the antenna elements to the ground
`plane may be used. The simplest conceptual arrangement
`consists of the conductors being placed on an infinite ground
`plane, or a ground plane that is very large in relation to the
`size of the antenna elements. Possible ground planes include
`the square ground plane 41 of FIG.4, round ground plane of
`FIG. 5, diamond ground plane of FIG. 6 and rectangular
`ground plane of FIG.7. An elliptical ground plane as shown
`in FIG. 3 may also be used.
`The antenna elements 42, 44, 52, 54, 62, 64, 72 and 74 of
`FIGS. 4-7 are preferably symmetrically placed on a sym-
`metrical ground plane to ensure that high isolation between
`the radiating elements will be maintained. The non-
`symmetrical arrangement shown in FIG. 7 will cause a
`degradation of the isolation between Hx magnetic loop and
`the E, radiating clement monopole. The high isolation
`between the Hx and the Hy antenna element feed points will
`be maintained.
`
`The relationship between the ground plane and the radi-
`ating elements can also be changed in the side cross sec-
`tional view of the antenna. In fact, the concept of the ground
`plane can be significantly altered. FIG. 8 shows an embodi-
`mentthat uses a local sunken ground plane 81 forming a box
`in which antenna elements $2 and 84 span across the top of
`the ground plane 81. The sunken ground plane may have
`plan views other than square configurations. These may also
`be round as shown in FIG. 9, diamond, elliptical and
`rectangular.
`A vertical, cross-sectional view of the cavity below the Hx
`and Hy antenna elements may take the shape of a square, a
`circle, a rectangle or an ellipsoid, or other largely arbitrary
`but symmetrical shape. The normal cross-sectional vertical
`view may be different from the top view.
`The antenna may also be built into a conductive box 100
`as shown in FIG. 10. in which the box 100 is formed from
`
`20
`
`8
`a peripheral wall 106 depending from antenna elements 102
`and 104 and a bottom surface 107 spaced from the antenna
`elements 102 and 104 and enclosed by the peripheral wall
`106. The antenna elements 102 and 104 of FIG. 10 are
`commensurate in size with the ground plane 107. Preferably.
`the ground plane 107 does not extend any further outward
`than the antenna elements 102 and 104 as shown in FIG. 10.
`
`The conductive box 10@ does not need to be square in
`cross section but it may have other shapes (such as part of
`a spherical or ellipsoid shell) and may be build into the end
`of a rectangular box 118 as shown in FIG. 11. The box in
`FIG. 11 is formed from sides 116 and bottom 117 with
`antenna elements 112, 113 and 114.
`Each antenna element must accept electrical power from
`a transmissionline or some other electrical circuit. The feed
`arrangement should satisfy two issues. (1) the physical and
`electrical symmetry of the antenna structure must be main-
`tained to retain antenna elementisolation and (2) tuning and
`impedance matching between the antenna elements and the
`feed structures minimizes the VSWR and therefore maxi-
`mizes powertransfer from the antenna to receiver or maxi-
`mizes power transfer from the transmitter to the antenna.
`The feed arrangement can best be illustrated with an
`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 (FP1 and FP2) or to the E, element feed point
`(FPS).
`Voltages may be delivered to feed points 1 and 2 (FP1 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 1, 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
`sensitive to the transmission line length 1,. The E, element
`achieves best bandwidth when the composite impedance
`looking into the feedpoints and ground plane from the loop
`approaches an open circuit.
`In FIG.13, a signal is input at feedpoint 132 and split by
`splitter 133 to feedpoints FPI and FP2 at the end of equal
`length transmission lines 1,
`in a magic T arrangement.
`Splitter 133 provides a 180° delay on one path (34/4) as
`compared with the other (A/4) where 4 is the wavelength of
`the carrier frequency of the signals the antenna is to be used
`with.
`In FIG. 14, a 3 dB branch line coupler splitter arrange-
`ment
`is shown with signal
`input from a source at 142