115
`United States Patent
`5,771,022
`(11] Patent Number:
`
`[45] Date of Patent: Jun. 23, 1998
`Vaughanet al.
`
`US005771022A
`
`[54] COMPOSITE ANTENNA FOR HAND HELD
`OR PORTABLE COMMUNICATIONS
`
`4,494,120
`
`1/1985 Garay vecccecssccssscssssseeesssessssssesees 343/702
`
`FOREIGN PATENT DOCUMENTS
`
`[75]
`
`Inventors: Rodney Vaughan;Neil Scott, both of
`Wellington, New Zealand
`
`.
`
`6/1992
`520 564
`European Pat. Off.
`France .
`10/1986
`2 605 148
`5/1973
`2155 016
`Germany .
`10/1981
`30 46 255
`Germany .
`42 21121 10/1993
`Germany .
`1 383 976
`10/1972
`United Kingdom .
`1 390 728=4/1975
`[21] Appl. No.:
`586,707
`United Kingdom .
`2 079 063
`6/1981
`United Kingdom .
`
`[73] Assignee:
`
`Industrial Research Limited,
`Wellington, New Zealand
`
`[22]
`
`[86]
`
`[87]
`
`[30
`
`PCT Filed:
`
`Jul. 29, 1994
`
`PCT No.:
`
`PCT/NZ94/00077
`
`§ 371 Date:
`
`Apr. 25, 1996
`
`§ 102(e) Date: Apr. 25, 1996
`
`PCT Pub. No.: WO95/04386
`
`PCT Pub. Date: May 9, 1995
`
`Foreign Application Priority Data
`
`
`
`
`Primary Examiner—Hoanganh T. Le
`Attorney, Agent, or Firm—Lowe, Price, LeBlanc & Becker
`
`[57]
`
`ABSTRACT
`
`A composite antenna for hand held communications appli-
`cations comprising at least two individual antennas spaced
`from each other at less than 0.3 wavelengths relative to the
`frequency to be received. Preferably the individual antennas
`are arranged in two or more arrays each of 2, 3, 4, 5 or more
`individual closely spaced antennas. Preferably each of the
`individual antennas is between 0.1 and 0.7 wavelengths long
`and mostpreferably about 1/4 wavelengths long. The com-
`posite antenna may be designed to operate in the 800 MHz
`to 5 GHz range. Preferably the individual antennas are
`spaced from each otherin the direction of orientation of the
`individual antennas to assist
`in each individual antenna
`receiving a signal as uncorrelated as possible to the signal
`received by the other individual antennas of the composite
`array.
`
`Jul. 29, 1993
`
`[NZ]
`
`New Zealand ...... ee 248283
`
`Int. C1eeee H01Q 1/24; HO1Q 21/06
`[51]
`[52] U.S. Che oe ceenesneeseesnessees 343/702; 343/893
`[58]
`Field of Search oes eeeeee 343/702, 893,
`343/846, 725, 729, 751, 853; HO1Q 1/24,
`21/06, 21/12, 21/24
`
`[56
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,396,920
`
`8/1983 Grimberg et al. oo. 343/846
`
`10 Claims, 5 Drawing Sheets
`
`1b
`
`1
`
`SAMSUNG 1077
`SAMSUNG 1077
`SAMSUNG v. SMART MOBILE
`SAMSUNG v. SMART MOBILE
`IPR2022-01004
`IPR2022-01004
`
`1
`
`

`

`U.S. Patent
`
`Jun. 23, 1998
`
`Sheet 1 of 5
`
`5,771,022
`
`
`
`FIG. 1
`
`2
`
`

`

`U.S. Patent
`
`Jun. 23, 1998
`
`Sheet 2 of 5
`
`5,771,022
`
`1234
`
`
`
`
`
`ENVELOPECORRELATIONCOEFFICIENT
`
`0
`
`
`
`~
`
`0
`
`005
`
`O17
`
`O15
`
`O38
`
`035
`
`04
`
`pe
`O2
`O25
`
`SPACING BETWEEN ADJACENT ELEMENTS (WAVELENGTHS)
`
`FIG. 2
`
`3
`
`

`

`U.S. Patent
`
`Jun. 23, 1998
`
`Sheet 3 of 5
`
`5,771,022
`
`FIG. 3
`
`FIG. 4
`
`4
`
`

`

`U.S. Patent
`
`Jun. 23, 1998
`
`Sheet 4 of 5
`
`5,771,022
`
`
`
`FIG. 5
`
`5
`
`

`

`U.S. Patent
`
`Jun. 23, 1998
`
`Sheet 5 of 5
`
`5,771,022
`
`FIG. 6
`
`6
`
`

`

`5,771,022
`
`1
`COMPOSITE ANTENNA FOR HAND HELD
`OR PORTABLE COMMUNICATIONS
`
`FIELD OF INVENTION
`
`The invention comprises an antenna particularly for a
`hand held or portable communications terminal.
`
`BACKGROUND
`
`the radio link is usually
`In mobile communications,
`non-line-of-sight. The information-bearing radio waves
`travelling between the terminals undergo multiple path
`propagation. The result is short-term signal fading, caused
`by wave interference, combined with long-term fading
`caused by “shadowing” of the waves by objects of several-
`wavelength dimension, such as people, trees, buildings, and
`hills, etc. The short-term fading occurs on average every
`half-wavelength, which, for example, at the newly allocated
`personal mobile communications frequencies of 1.5 to 1.7
`GHz, is about every 10 cm. The short-term fading of the
`signal envelope is approximately Rayleigh-distributed. The
`long-term fading occurs over several wavelengths and is
`approximately log-normal distributed. The fading impairs
`the capacity, or quality, of the communications channel.
`A well knowntechnique to mitigate the effects of fading
`is by using antenna diversity with a signal combiner.
`Awell knownform of diversity antennais space diversity,
`in which similar elements are spaced apart by a half-
`wavelength or more.
`Further,
`for hand held terminals, up to two antenna
`elements can be configured using polarization diversity. The
`polarization diverse antenna requires a monopole antenna
`and a collocated loop antenna—i.e.,
`the loop is located
`around the monopole.
`The idea of diversity antennas is to receive “uncorrelated
`signals”. For the Rayleigh distributed short term fading,this
`can be taken to mean that “the envelopes should have
`short-term cross correlation coefficients of less than 0.7”.
`
`SUMMARYOF INVENTION
`
`The present invention provides an antenna particularly
`suitable for a hand held or portable communications termi-
`nal.
`
`In broad terms the invention may be said to comprise a
`composite antenna comprising at least two individual anten-
`nas spaced from each other at less than 0.3 wavelengths
`relative to the frequency to be received, on a hand held or
`portable communications terminal.
`Preferably a composite antenna of the invention com-
`prises multiple antennas which are spaced as closely as 0.2
`or 0.15 wavelengths from each other or even less than 0.1
`wavelengths, in two or more separate arrays. ‘lhe individual
`antennas may be spaced as closely as 0.06 wavelengths for
`a two element array and 0.07 wavelengths for a three or
`more element array,
`relative to the frequencies to be
`received. The individual antennas may be regularly or
`irregularly spaced from each other.
`Most preferably a composite antenna of the invention
`consists of two or more arrays of individual closely spaced
`antennas, with each array comprising two, three, four, five or
`more individual antennas.
`
`The frequencies to be received i.e, for which the com-
`posite antenna of the invention is designed, may be any
`portable communications frequencies such as cellular tele-
`phone communication frequency bands, frequency bands
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`that may be utilized for communicating between computers
`on a wireless network or the like. Typically the composite
`antenna will be designed to comprise a numberof individual
`antennas closely spaced for frequencies in the 800 MHzto
`5 GHzrange, and particularly the 1.5 to 1.7 GHz range and
`also at about 2.7 GHz, these being international frequencies
`for personal communications.
`Preferably each of the individual antennas making up the
`composite antenna comprises a monopole, but it
`is also
`possible for each of the antennas to comprise a folded
`monopole, a slot or loop antenna element, a patch element,
`a printed element or any other type of antenna type.
`Preferably each of the antennas is between 0.1 and 0.7
`wavelengths long relative to the received frequencies, and
`most preferably about 4 wavelength long.
`Preferably the individual antennas or al least some of the
`antennas are spaced from each other in the direction of
`orientation of the individual antennas to assist
`in each
`individual antenna receiving a signal as uncorrelated as
`possible to the signal received from the other individual
`antennas.
`
`A ground plane can be added to the composite antennato
`optically shadow the antenna from the head of a user in the
`case of a mobile phone for example, and/or to increase the
`effective gain of the antenna and/or to offer the impedance
`stability and added strength for the radome on a terminal. A
`conductive shield does not unduly influence the signal
`correlations, and mayassist in decreasing signal correlation
`throughreflection and diffraction effects between individual
`antennas by altering the effective receiving pattern of the
`antennas.
`
`DESCRIPTION OF DRAWINGS
`
`The accompanying drawingsillustrate various preferred
`forms of composite antennas of the invention, by way of
`example and without intending to be limiting. In the draw-
`ings:
`FIG. 1 shows a preferred form composite antenna of the
`invention comprising multiple, closely spaced monopole
`antennas, held in the hand,
`FIG. 2 showsthe theoretical envelope cross-correlation
`coefficients for four elements of a composite antenna similar
`to that of FIG. 1,
`FIG. 3 showsan alternative configuration for a composite
`antenna of the invention comprising multiple, closely spaced
`monopole antennas,
`FIG. 4 shows a further alternative composite antenna of
`the invention comprising closely spaced monopole antennas,
`FIG. 5 shows a composite antenna of the invention similar
`to that of FIG. 1, but where each individual antenna com-
`prises a slot antenna, and
`FIG. 6 shows a composite antenna generally similar to
`that of FIG. 1 but where the individual antennas each
`comprise a folded monopole antenna.
`
`DESCRIPTION OF PREFERRED FORMS
`
`Referring to FIG. 1, it can be seen that the composite
`antenna shown is small with a number of closely spaced
`individual antennas la and 1b in two arrays. The FIG. 1
`configuration is particularly suitable for
`incorporation
`within the casing of a mobile telephone for example. The
`small size of the composite antenna enables the antenna to
`be incorporated completely within the casing or on the back
`of a mobile phone whilst maximising reception of a number
`
`7
`
`

`

`5,771,022
`
`3
`of uncorrelated signals from which an improved quality
`received signal may be produced by combining.
`The antenna array of FIG. 1 comprises eight monopole
`antennas arranged as a top array la and a bottom array 1b.
`Within the housing 2 the antennas are terminated and the
`housing also contains a combining stage for combining the
`uncorrelated signals from each of the individual antennas.
`The combining stage may utilise any suitable combining
`technique such as switched or selection combining, equal
`gain or maximum ratio combining carried out pre- or
`post-detection, optimum combining or the like. For opti-
`mum reception,
`the signals from each of the individual
`antennas should be used simultaneously. The antennas
`should all be permanently terminated, rather than switched
`to open-circuit conditions during the combination process.
`This means that there is always mutual coupling between the
`individual antennas. While this reduces the mean received
`
`power, the signal fading, which can limit the channel capac-
`ity independently of the mean powerlevel, is reduced, and
`the ensuing channel capacity limitation can in turn be
`reduced.
`
`A ground plane 3 is optionally provided behind the
`antennas.
`
`A composite antenna of the invention as shown in FIG. 1
`wasconstructed scaled for operation at a receive frequency
`of 1.5 GHz. Each of the monopole antennas la and 1b was
`Y% wave length long for 1.5 GHz and each antenna was
`spaced from the adjacent antenna(s) by 0.07 wave length.
`The cross-correlation between signals received from any top
`array element la and any bottom array element 1b was
`found to be small, owing to their separation in the direction
`of the individual antennaorientation. The limiting spacing is
`between adjacent
`individual antennas. The composite
`antenna of FIG. 1 has been measured at 851 MHz,and the
`short term cross-correlation co-efficients of the envelopes
`were aroundor less than 0.7 and the results are shownin the
`table below. These experiments were undertaken in an
`indoor environment, where there was often a direct line of
`sight between terminals. This situation offers nominally less
`fading than in a non-line of sight situation, so the example
`is worst case in the sense that the cross-correlation coeffi-
`cients in Table 1 will be at the high end for normal operating
`conditions.
`
`TABLE
`
`Theory (figure 2)
`(Rayleigh signals only)
`0.7
`0.6
`
`Rp
`Ryo
`
`Experimental
`(Short-term coefficient)
`0.46-0.75
`0.49-0.64
`
`FIG. 2 shows the envelope cross-correlation coefficients
`for the top array of four adjacent antennas with varying
`individual antenna spacing. In FIG. 2 R,, denotes the outer
`adjacent pairs, R,, the spaced alternate pairs, and R,, the
`pair of outer antennas.
`It was found that for a cross-
`correlation coefficient of 0.7 or less, the outer most pair limit
`the linear spacing between individual antennasto about 0.07
`wave lengths. The worst case spacing is given by the R,,
`curve, i.e, that relating to outer adjacent antennas and the
`inner adjacent antennas R,,. The short tern correlation is less
`than the long term correlation, so the theoretical curves give
`pessimistic (i.e. large) antenna spacings. FIG. 2 is computed
`using assumptions for a tractable analysis and will not be
`exact
`in practice, but nonetheless offers a guide to the
`cross-sectional limitations.
`
`4
`FIG. 3 showsan alternative composite antenna of the
`invention, with four arrays of each of three individual
`monopole antennas about a central housing 2 oriented in
`four directions as shown.
`In a related alternative
`configuration, a numberof individual antennas may extend
`radially from a circular housing.It is also not necessary that
`the elements all lie in a common plane.
`FIG. 4 shows a further alternative composite antenna of
`the invention using sloping monopoles, which have the
`advantage of allowing a closer feed point spacing. Relative
`to the antenna of FIG. 1, the outer individual antennasin the
`top and bottom arrays are bent away from the central
`antenna but alternatively individual antennas could be bent
`towards each other and the bending angle can be in either the
`plane of the arrays, or orthogonal
`to that plane, or a
`combination thereof.
`
`FIG. 5 shows a composite antenna of the invention which
`is similar to FIG. 1 but comprises top and bottom arrays of
`closely spaced slot antennas la and 1b. As is knownfor such
`slot antennas, the earth sheath of a coaxial feed cable can be
`connected to one edge of the slot antenna and the central
`conductor of the coaxial cable to the other edge of the slot.
`Such slot antennas could be angled towards or away from
`each other also, for example.
`FIG. 6 shows a further composite antenna of the
`invention, in this case comprising a top array of three folded
`monopole antennas 1a, and a similar bottom array of anten-
`nas 1b.
`
`A composite antenna of the invention may also comprise
`a combination of individual antennasof different types. For
`example an antenna array may be made up of a number of
`individual monopole and slot antennas, sleeved monopole
`antennas, or antennas of any other type. The individual
`antennas may beregularly or irregularly spaced.
`The composite antennas of the invention with multiple
`closely spaced individual antennas enables multi-element
`antennas to be much more compact than previously. For
`example, a composite antenna of the invention comprising
`two closely spaced monopolesin fact occupies less volume
`than a correspondingpolarisation diverse antenna. The com-
`posite antenna design of the invention is particularly suited
`for hand held or portable communications terminals.
`The foregoing describes the invention including preferred
`forms thereof. Alterations and modifications as will be
`obvious to those skilled in the art are intended to be
`
`incorporated in the scope hereof as defined in the claims.
`Weclaim:
`
`1. A composite antenna comprising at least three indi-
`vidual antennas spaced from each other at less than 0.2
`wavelengths relative to the frequency to be received and an
`associated combining stage which combines uncorrelated
`signals from each of the antennas using an antennadiversity
`combining technique, on a hand held or portable commu-
`nications terminal.
`
`2. Acomposite antenna according to claim 1, wherein the
`individual antennasare spaced at less than 0.15 wavelengths
`from each other.
`
`3. Acomposite antenna according to claim 1, wherein the
`individual antennas are spaced at less than 0.1 wavelengths
`from each other.
`4. A composite antenna as claimed in claim 1 wherein
`individual antennas are arranged in two or more separate
`arrays, each of three or more individual antennas.
`5. A composite antenna according to claim 1, wherein
`each of the individual antennas making up the composite
`antenna comprises a monopole including a folded mono-
`pole.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`
`

`

`5
`6. Acomposite antenna according to claim 1 wherein each
`of the individual antennas is between 0.1 and 0.7 wave-
`
`6
`signal uncorrelated to the signal received by the other
`individual antennas.
`
`5,771,022
`
`lengths long relative to the received frequencies.
`7. Acomposite antenna according to claim 1 wherein each
`of the individual antennas is about % wavelength long.
`8. A composite antenna according to claim 1 wherein the
`individual antennasor at least some thereof are spaced from
`each other in the direction of orientation of the individual
`antennas to assist in each individual antenna receiving a
`
`5
`
`9. Acomposite antenna according to claim 1, including a
`ground plane adjacent the antennas.
`10. A composite antenna as claimed in claim 1, designed
`for frequencies in the 800 MHzto 5 GHzrange.
`
`9
`
`