U.S. patent application number 10/935559 was filed with the patent office on 2005-02-10 for interlaced multiband antenna arrays.
Invention is credited to Baliarda, Carles Puente.
Application Number | 20050030247 10/935559 |
Document ID | / |
Family ID | 8307385 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050030247 |
Kind Code |
A1 |
Baliarda, Carles Puente |
February 10, 2005 |
Interlaced multiband antenna arrays
Abstract
Antenna arrays which can work simultaneously in various
frequency bands thanks to the physical disposition of the elements
which constitute them, and also the multiband behaviour of some
elements situated strategically in the array. The configuration of
the array is described based on the juxtaposition or interleaving
of various conventional mono-band arrays working in the different
bands of interest. In those positions in which elements of
different multiband arrays come together, a multiband antenna is
employed which covers the different working frequency bands. The
advantages with respect to the classic configuration of using one
array for each frequency band are: saving in cost of the global
radiating system and its installation (one array replaces several),
and its size and visual and environmental impact are reduced in the
case of base stations and repeater stations for communication
systems.
Inventors: |
Baliarda, Carles Puente;
(Barcelona, ES) |
Correspondence
Address: |
JOSEPH M. SAUER
JONES DAY REAVIS & POGUE
NORTH POINT, 901 LAKESIDE AVENUE
CLEVELAND
OH
44114
US
|
Family ID: |
8307385 |
Appl. No.: |
10/935559 |
Filed: |
September 7, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10935559 |
Sep 7, 2004 |
|
|
|
10135019 |
Apr 23, 2002 |
|
|
|
Current U.S.
Class: |
343/824 |
Current CPC
Class: |
H01Q 1/246 20130101;
H01Q 21/30 20130101; H01Q 21/062 20130101; H01Q 21/061 20130101;
H01Q 21/08 20130101; H01Q 21/28 20130101; H01Q 5/42 20150115; H04W
16/24 20130101 |
Class at
Publication: |
343/824 |
International
Class: |
H01Q 021/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 1999 |
WO |
PCT/ES99/00343 |
Claims
1. Interlaced multiband antenna arrays which works simultaneously
on various frequencies characterised in that the position of the
elements in the array is obtained from the juxtaposition of as many
mono-band arrays as there are working frequencies required,
employing a single multiband antenna, capable of covering the
different working frequencies, in those positions of the array in
which the positions of two or more elements of the mono-band arrays
come together.
Description
OBJECT OF THE INVENTION
[0001] The present invention consists of antenna arrays which can
be operated simultaneously in various frequency bands thanks to the
physical disposition of the elements that constitute it, as well as
the multiband behaviour of some elements situated strategically in
the array.
[0002] The array configuration is described on a basis of the
juxtaposition or interleaving of various conventional single-band
arrays operating in the different bands of interest. In those
positions where elements of different multiband arrays come
together, use is made of a multiband antenna which covers the
different working frequency bands.
[0003] The use of a multiband interleaved antenna array
(hereinafter simply Multiband Interleaved Array, MIA) implies a
great advantage over the classical solution of employing an array
for each frequency band: there is a cost saving in the overall
radiating system and in its installation (one array replaces
several), its size is reduced as well as its visual and
environmental impact in the case of base and repeater stations for
communication systems.
[0004] The present invention finds its application in the field of
telecommunications and more specifically in radiocommunication
systems.
BACKGROUND AND SUMMARY OF THE INVENTION
[0005] Antennas started to be developed at the end of the
nineteenth century based on the fundamental laws of
electromagnetism postulated by James Clerk Maxwell in 1864. The
invention of the first antenna has to be attributed to Heinrich
Hertz in 1886 who demonstrated the transmission through air of
electromagnetic waves. In the mid-1940's the fundamental
restrictions regarding the reduction in size of antennas were shown
with respect to wavelength and at the beginning of the sixties
appeared the first frequency-independent antennas (E. C. Jordan, G.
A. Deschamps, J. D. Dyson, P. E. Mayes, "Developments in Broadband
Antennas," IEEE Spectrum, vol.1, pp. 58-71, April 1964; V. H.
Rumsey, Frequency-Independent Antennas. New York Academic, 1966; R.
L. Carrel, "Analysis and design of the log-periodic dipole array,"
Tech. Rep. 52, Univ. of Illinois Antenna Lab., Contract AF33
(616)-6079, October 1961; P. E. Mayes, "Frequency Independent
Antennas and Broad-Band Derivatives Thereof", Proc. IEEE, vol.80,
no.1, January 1992). At that time proposals were made for helical,
spiral, log-periodic arrays, cones and structures defined
exclusively by angle pieces for the implementation of broadband
antennas.
[0006] Antenna array theory goes back to the works of Shelkunoff
(S. A. Schellkunhoff, "A Mathematical Theory of Linear Arrays,"
Bell System Technical Journal, 22,80), among other classic
treatises on antenna theory. Said theory establishes the basic
design rules for shaping the radiation properties of the array
(principally its radiation pattern), though its application is
restricted mainly to the case of mono-band arrays. The cause of
said restriction lies in the frequency behaviour of the array being
highly dependent on the ratio between the distance between elements
(antennas) of the array and the working wavelength. Said spacing
between elements is usually constant and preferably less than one
wavelength in order to prevent the appearance of diffraction lobes.
This implies that once the spacing between elements is fixed, the
operating frequency (and the corresponding wavelength) is also
fixed, it being particularly difficult that the same array work
simultaneously at another higher frequency, given that in that case
the magnitude of the wavelength is less than the spacing between
elements.
[0007] The log-periodic arrays suppose one of the first examples of
antenna arrays capable of covering a broad range of frequencies (V.
H. Rumsey, Frequency-Independent Antennas. New York Academic, 1966;
R. L. Carrel, "Analysis and design of the log-periodic dipole
array," Tech. Rep. 52, Univ. Illinois Antenna Lab., Contract AF33
(616)-6079, October 1961; P. E. Mayes, "Frequency Independent
Antennas and Broad-Band Derivatives Thereof", Proc. IEEE, vol.80,
no.1, Jan. 1992). Said arrays are based on distributing the
elements that constitute it in such a manner that the spacing
between adjacent elements and their length vary according to a
geometric progression. Although said antennas are capable of
maintaining a same radiation and impedance pattern over a broad
range of frequencies, their application in practice is restricted
to some concrete cases due to their limitations regarding gain and
size. Thus for example, said antennas are not employed in cellular
telephony base stations because they do not have sufficient gain
(their gain is around 10 dBi when the usual requirement is for
about 17 dBi for such application), they usually have linear
polarisation whilst in said environment antennas are required with
polarisation diversity, their pattern in the horizontal plane does
not have the width necessary and their mechanical structure is too
bulky.
[0008] The technology of individual multiband antennas is markedly
more developed. A multiband antenna is understood to be an antenna
formed by a set of elements coupled to each other
electromagnetically which interact with each other in order to
establish the radio-electric behaviour of the antenna, behaviour
which with respect to radiation and impedance patterns is similar
in multiple frequency bands (hence the name multiband antenna).
Numerous examples of multiband antennas are described in the
literature. In 1995 antennas of the fractal or multifractal type
were introduced (the coining of the terms fractal and multifractal
is attributable to B. B. Mandelbrot in his book The Fractal
Geometry of Nature, W. H. Freeman and Co. 1983), antennas which by
their geometry have a multifrequency behaviour and, in determined
cases, a reduced size (C. Puente, R. Pous, J. Romeu, X. Garcia
"Antenas Fractales o Mulitfractales", (Spanish patent P9501019).
Subsequently multi-triangular antennas were introduced (Spanish
patent P9800954) which could work simultaneously in the GSM 900 and
GSM 1800 bands and, more recently, multilevel antennas (Patent
PCT/ES99/00296), which offer a clear example of how it is possible
to shape the geometry of the antenna in order to achieve a
multiband behaviour.
[0009] The present invention describes how multiband antennas can
be combined in order to obtain an array that works simultaneously
in several frequency bands.
[0010] A Multiband Interleaved Array (MIA) consists of an array of
antennas which has the particularity of being capable of working
simultaneously in various frequency bands. This is achieved by
means of using multiband antennas in strategic positions of the
array. The disposition of the elements that constitute the MIA is
obtained from the juxtaposition of conventional mono-band arrays,
employing as many mono-band arrays as frequency bands that it is
wished to incorporate in the Multiband Interleaved Array. In those
positions in which one or various elements originating in the
conventional mono-band arrays coincide, a single multiband antenna
(element) shall be employed which covers simultaneously the
different bands. In the remaining non-concurrent positions, it can
be chosen to employ also the same multiband antenna or else recur
to a conventional mono-band antenna which works at the pertinent
frequency. The excitation at one or various frequencies of each
element of the array depends therefore on the position of the
element in the array and is controlled by means of the signal
distribution network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The characteristics expounded in the foregoing, are
presented in graphical form making use of the figures in the
drawings attached, in which is shown by way of a purely
illustrative and not restrictive example, a preferred form of
embodiment. In said drawings:
[0012] FIG. 1 shows the position of the elements of two classic
mono-band arrays which work at frequencies f and f/2 respectively,
and the disposition of elements in a multiband interleaved array,
which has a dual frequency behaviour (at frequencies f and f/2),
working in the same manner as classic arrays but with a smaller
total number of elements.
[0013] FIG. 2 shows another particular example of multiband
interleaved array but with three frequencies in this case, and the
respective three classic mono-band arrays which constitute it. It
is a matter of extending the case of FIG. 1 to 3 frequencies f, f/2
and f/4.
[0014] FIG. 3 shows another particular example of multiband
interleaved array, in which the different working frequencies are
not separated by the same scale factor. It is a matter of extending
the case of FIGS. 1 and 2 to 3 frequencies f, f/2 and f/3.
[0015] FIG. 4 shows a further particular example of multiband
interleaved array, in which the different working frequencies are
not separated by the same scale factor. It is a matter of extending
the case of FIG. 3 to 3 frequencies f, f/3 and f/4.
[0016] FIG. 5 shows a multiband interleaved array configuration
which requires a repositioning of the elements to obtain
frequencies that do not correspond to an integer factor of the
highest frequency. In this particular example the frequencies f,
f/2 and f/2,33 have been chosen.
[0017] FIG. 6 shows the extension of the design of an MIA to the
two-dimensional or three-dimensional case, specifically, an
extension of the example of FIG. 1 to two dimensions.
[0018] FIG. 7 shows one of the preferred of operating modes (AEM1).
It is a matter of an MIA in which the multiband elements are
multi-triangular elements. The array works simultaneously at dual
frequencies, for example in the GSM 900 and GSM 1800 bands.
[0019] FIG. 8 shows another of the preferred operating modes
(AEM2). It is a matter of an MIA in which the multiband elements
are multilevel elements. The array works simultaneously at dual
frequencies, for example in the GSM 900 and GSM 1800 bands.
[0020] FIG. 9 shows another of the preferred operating modes
(AEM3). It is a matter of an MIA in which the multiband elements
are multilevel elements. The configuration is similar to that of
FIG. 8 (AEM2 mode), the difference being that the new disposition
permits the total width of the antenna to be reduced.
[0021] FIG. 10 shows another example of multiband antenna which can
be employed in MIAS. It is a matter of a stacked patch antenna,
which in this specific example works at two dual frequencies (for
example, GSM 900 and GSM 1800).
[0022] FIG. 11 shows the disposition of said patches in the MIA
type array (AEM4 configuration). Observe that, in contrast to the
previous cases, in this case multiband antennas are employed only
in those positions where it is strictly necessary; in the remainder
mono-band elements are employed the radiation pattern of which is
sufficiently like that of the multiband element in the pertinent
band.
[0023] FIG. 12 shows another configuration (AEM5), in which the
elements have been rotated through 45.degree. in order to
facilitate the procurement of double polarisation at +45.degree. or
-45.degree..
DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
[0024] In making the detailed description that follows of the
preferred embodiment of the present invention, reference shall
constantly be made to the Figures of the drawings, throughout which
use has been made of the same numerical references for the same or
similar parts.
[0025] A multiband interleaved array (MIA) is constituted by the
juxtaposition of various conventional mono-band arrays. The
conventional antenna arrays usually have a mono-band behaviour
(that is, they work within a relatively small frequency range,
typically of the order of 10% about a centre frequency) and this is
not only because the elements (antennas) that constitute it have a
mono-band behaviour, but also because the physical spacing between
elements conditions the working wavelength. Typically, the
conventional mono-band arrays are designed with a spacing between
elements of around a half-wavelength, spacing which may be
increased in some configurations in order to enhance directivity,
though it is usually kept below one wavelength to avoid the
appearance of diffraction lobes.
[0026] This purely geometric restriction (the magnitude of the
wavelength conditions the geometry of the elements of the array and
their relative spacing) signifies a major drawback in those
environments and communication systems in which various frequency
bands have to be employed simultaneously. A clear example is the
GSM cellular mobile telephony system. Initially located in the 900
MHz band, the GSM system has turned into one of the most widespread
on a world scale. The success of the system and the spectacular
growth in demand for this type of service has led to the cellular
mobile telephony operators expanding its service into a new band,
the 1800 MHz band, in order to provide coverage for a greater
customer base. Making use of classic mono-band antenna technology,
the operators have to duplicate their antenna network in order to
provide coverage simultaneously to GSM 900 and GSM 1800. Using a
single MIA specially designed for the system (like that described
in the particular cases of FIGS. 7 through 12), the operators
reduce the cost of their network of base stations, the time to
expand into the new band and the visual and environmental impact of
their installations (through the simplification of the overall
radiating structure).
[0027] It is important to point out that the scenario which has
just been outlined above deals only with one particular example of
a type of MIA and its application; as may well be gauged by anyone
familiar with the subject, in no way are the MIAs which are
described in the present invention restricted to said specific
configuration and can easily be adapted to other frequencies and
applications.
[0028] The multiband interleaved arrays base their operation on the
physical disposition of the antennas which constitute them and on
the particular type of element that is employed in some strategic
positions of the array.
[0029] The positions of the elements in an MIA are determined from
the positions of the elements in as many mono-band arrays as there
are frequencies or frequency bands required. The design of the
array is, in that sense, equal to that of the mono-band arrays
insomuch as it is possible to choose the current weighting for each
element, in order to shape the radiation pattern according to the
needs of each application. The configuration of the MIA is obtained
from the juxtaposition of the positions of the different mono-band
arrays. Naturally, such juxtaposition proves difficult to implement
in practice in those positions in which various antennas of the
different arrays coincide; the solution proposed in this invention
rests in the use of a multiband antenna (for example of the
fractal, multi-triangular, multi-level, etc. type) which covers all
the frequencies associated with its position.
[0030] A basic and particular example of how to arrange the
elements in an MIA is described in FIG. 1. In the columns of the
FIGS. (1.1) and (1.2) two conventional mono-band arrays are shown
in which the positions of the elements (indicated by the black
circles and the circumferences respectively) are chosen in such a
manner that the spacing between elements is typically less than the
working wavelength. Thus, taking as reference the working frequency
f of the array (1.1), the array (1.2) would work at a frequency f/2
as the elements have a spacing double that of the previous case. In
FIG. (1.3) the disposition is shown of the elements in the MIA
which is capable of working simultaneously on the frequencies f and
f/2 conserving basically the same facilities as the two arrays
(1.1) and (1.2). In the positions in which elements of the two
conventional arrays (indicated in FIG. (1.3) by means of black
circles located at the centre of a circumference) coincide, a
multiband antenna is employed capable of working in the same manner
(same impedance and pattern) on the frequencies (1.1) and (1.2).
The remaining not common elements (indicated either by a black
circle, or by a circumference) can be implemented either by means
of the same multiband element employed in the common positions (and
selecting the working frequency by means of the signal distribution
network of the array), or by employing conventional mono-band
elements. In this example the array (1.3) has a dual behaviour
frequency-wise (at frequencies f and f/2), working in the same
manner as the arrays (1.1) and (1.2) but with a smaller total
number of elements (12 instead of 16).
[0031] Multiple examples of multiband antennas are already
described in the state of the art. Antennas with fractal geometry,
multi-triangular antennas, multi-level antennas even stacked patch
antennas are some examples of antennas capable of working in like
manner in multiple frequency bands. These, and other multiband
elements can be employed in the positions of the MIAs in which
elements of various mono-band arrays come together.
[0032] In the following figures other MIA configurations are shown,
based on the same inventive concept, though having the disposition
of the elements adapted to other frequencies. In FIG. 2 the
configuration described is that of a tri-band MIA working at
frequencies f, f/2 and f/4. The disposition of elements in the
three classic mono-band arrays at the frequencies f, f/2 and f/4 is
illustrated in the FIGS. (2.1), (2.2) and (2.3) by means of black
circles, circumferences and squares respectively. The position of
the elements of the MIA is determined from the configuration of the
three mono-band arrays designed for each one of the three
frequencies. The three arrays come together in the MIA that is
shown in FIG. (2.4). In those positions where elements of the three
arrays would come together (indicated in the drawing by the
juxtaposition of the different geometric figures identifying each
array) use is made of a multiband element. The three-frequency
array of FIG. (2.4) behaves in the same manner as the three arrays
(2.1), (2.2) and (2.3) at their respective working frequencies, but
employing only 13 elements instead of the 21 required in the total
of the three mono-band arrays.
[0033] FIGS. 3, 4 and 5 describe, by way of example and not
restrictively, the design of other MIAs based on the same principle
though at other frequencies. In the first two cases the frequencies
employed are integer multiples of a fundamental frequency; in the
case of FIG. 5 the ratio between frequencies is not restricted to
any particular rule, though it supposes an example of array in
which the frequencies the GSM 900, GSM 1800 and UMTS services can
be combined.
[0034] Specifically, FIG. 3 illustrates another particular example
of multiband interleaved array, in which the different working
frequencies are not separated by the same scale factor. It concerns
the extension of the case of FIGS. 1 and 2 to 3 frequencies f, f/2
and f/3. The disposition of elements of the three classic mono-band
arrays at the frequencies f, f/2 and f/3 is shown in FIGS. (3.1),
(3.2) and (3.3) by means of black circles, circumferences and
squares respectively. The column of FIG. (3.4) shows the
disposition of elements in the tri-band interleaved array. In those
positions in which elements of the three arrays come together
(indicated in the drawing by the juxtaposition of the different
geometric figures identifying each array), use is made of a
multiband element; the same strategy is followed in those positions
in which elements of two arrays coincide: use should be made of a
multiband element capable of covering the frequencies pertinent to
its position, preferentially the same element as that used in the
remaining positions, selecting those frequencies which are
necessary by means of the feeder network. Notice that as the
three-frequency array of FIG. (3.4) behaves in the same manner as
the three arrays (3.1), (3.2) and (3.3) at their respective working
frequencies, but employing only 12 elements instead of the 21
required in the total of the three mono-band arrays.
[0035] FIG. 4 illustrates a new particular example of multiband
interleaved array, in which the different working frequencies are
not separated by the same scale factor. It concerns the extension
of the case of FIG. 3 to 3 frequencies f, f/3 and f/4. The
disposition of elements of the three classic mono-band arrays at
the frequencies f, f/3 and f/4 are shown in FIGS. (4.1), (4.2) and
(4.3) by means of black circles, circumferences and squares
respectively. The column of FIG. (4.4) shows the disposition of
elements in the tri-band interleaved array. In those positions
where elements of the three arrays would come together (indicated
in the drawing by the juxtaposition of the different geometric
figures identifying each array), use is made of a multiband
element. The three-frequency array of FIG. (4.4) behaves in the
same manner as the three arrays (4.1), (4.2) and (4.3) at their
respective working frequencies, but employing only 15 elements
instead of the 24 required in the total of the three mono-band
arrays.
[0036] It is convenient to re-emphasise that in the particular
cases of FIGS. 3 and 4 the arrays can work at 3 frequencies
simultaneously. The disposition of elements is such that the three
frequencies do not always coincide in all the elements;
nonetheless, by employing a tri-band antenna in those positions and
selecting the working frequencies for example by means of a
conventional frequency-selective network, it is possible to
implement the MIA.
[0037] In some configurations of multiband interleaved array,
especially in those in which the different frequencies do not
correspond to an integral factor of the highest frequency 1, it is
required that the elements be repositioned, as in FIG. 5. In this
particular example the frequencies f, f/2 and f/2,33 have been
chosen. The disposition of elements of the three classic mono-band
arrays at the frequencies f, f/2 and f/2,33 is represented in FIGS.
(5.1), (5.2) and (5.3) by means of black circles, circumferences
and squares respectively. The column of FIG. (5.4) shows what would
be the disposition of elements in the tri-band interleaved array
according to the same plan as in the previous examples. Notice how
in this case the ratio of frequencies involves the collocation of
elements at intermediate positions which make its practical
implementation difficult. The solution to be adopted in this case
consists in displacing the position of the element of the array
that works at the lowest frequency (indicated by arrows) until it
coincides with another element (that nearest) of the highest
frequency array; then the two or more coincident elements in the
new position are replaced with a multiband element. An example of
the final configuration once the elements have been repositioned,
is shown in FIG. (5.5). It is important that the element displaced
be preferentially that of the lowest frequency array, in this way
the relative displacement in terms of the working wavelength is the
least possible and the appearance of secondary or diffraction lobes
is reduced to the minimum.
[0038] FIG. 6 illustrates how the configuration MIAs is not limited
to the linear (one-dimensional) case, but it also includes arrays
in 2 and 3 dimensions (2D and 3D). The procedure for distributing
the elements of the array in the 2D and 3D cases is the same,
replacing also the different coincident elements with a single
multiband antenna.
[0039] More examples of particular configurations of MIAs are
described below. In the five examples described, various designs
are presented for GSM 900 and GSM 1800 systems (890 MHz-960 MHz and
1710 MHz-1880 MHz bands) It is a question of antennas for cellular
telephony base stations, which present basically the same
radiofrequency behaviour in both bands; by employing such versions
of MIA antenna the operators reduce the number of antennas
installed to one half, minimising the cost and environmental impact
of their base stations.
[0040] AEM1 Mode
[0041] The AEM1 configuration, represented in FIG. 7, is based on
the use of GSM 900 and GSM 1800 multi-triangular elements. The
array is obtained by interleaving two conventional mono-band arrays
with spacing between elements less than one wavelength ( ) in the
pertinent band (typically a spacing is chosen less than 0.9 in
order to minimise the appearance of the diffraction lobe in the
end-fire direction). The original arrays can have 8 or 10 elements,
depending on the gain required by the operator. The juxtaposition
of both arrays in a single MIA is achieved in this case by
employing dual multi-triangular elements. Such elements incorporate
two excitation points (one for each band), which allows the working
band to be selected according to their position in the array. In
FIG. 7 the position of the elements is shown, as well as their
working frequencies. The elements shown in white indicate operation
in the GSM 900 band; the elements shown in black indicate operation
in the GSM 1800 band and the elements marked in black in the lower
triangle and in white in their two upper triangles indicate
simultaneous operation in both bands. Precisely the simultaneous
operation in both bands via a single multiband element (the
multi-triangular element) in such positions of the array (those
positions at which those of the original mono-band arrays
coincide), is one of the main characteristic features of the MIA
invention.
[0042] The manner of feeding the elements of the AEM1 array is not
characteristic of the invention of the MIAs and recourse may be had
to any conventionally known system. In particular and given that
the multi-triangular elements are excited at two different points,
it is possible to make use of an independent distribution network
for each band. Another alternative consists in employing a
broadband or dual band distribution network, by coupling a
combiner/diplexer which interconnects the network and the two
excitation points of the multi-triangular antenna.
[0043] Finally, the antenna may therefore come with two
input/output connectors (one for each band), or combined in a
single connector by means of a combiner/diplexer network.
[0044] AEM2 Mode
[0045] This particular configuration of AEM2, shown in FIG. 8, is
based on a multilevel antenna which acts as a multiband element. In
addition to working simultaneously in the GSM 900 and GSM 1800
bands, the antenna has also double linear polarisation at
+45.degree. and -45.degree. with respect to the longitudinal axis
of the array. The fact that the antenna has double polarisation
signifies an additional advantage for the cellular telephony
operator, since in this manner he can implement a diversity system
which minimises the effect of fading by multipath propagation. The
multilevel element which is described in FIG. 8 is more suitable
than the multi-triangular element described previously since the
element itself has a linear polarisation at +45.degree. in GSM 900
and at -45.degree. in GSM 1800.
[0046] The array is obtained by interleaving two conventional
mono-band arrays with spacing between elements less than one
wavelength ( ) in the pertinent band (typically a spacing less than
0.9 is chosen in order to minimise the appearance of the
diffraction lobe in the end-fire direction). The original arrays
can have 8 or 10 elements depending on the gain required by the
operator. The juxtaposition of both arrays in a single MIA is
achieved in this case by employing in-band dual multilevel
elements. Such elements incorporate two points of excitation (one
for each band), which permits the working band to be selected
according to their position in the array. In FIG. 8 the position of
the elements is shown, as well as their working frequencies. The
elements shown in white indicate operation in the GSM 900 band; the
elements shown in black indicate operation in the GSM 1800 band and
the elements marked in black in their lower triangle and in white
in the upper triangles indicate simultaneous operation in both
bands. Precisely the simultaneous operation in both bands via a
single multiband element (the multilevel element) in such positions
of the array (those positions in which those of the original
mono-band arrays coincide), is one of the main characteristic
features of the MIA invention.
[0047] It is possible to achieve double polarisation on a basis of
exciting the multilevel element at various points on its surface;
nonetheless in order to augment the isolation between connectors of
different polarisation, it is chosen in the example described to
implement a double column to separate the +45.degree. polarization
(left-hand column) from that of -45.degree. (right-hand column). To
increase the isolation between bands, it is even possible to
interchange the polarisation inclination in the columns of the
array in one of the bands (for example in DCS).
[0048] The manner of feeding the elements of the array AEM2 is not
characteristic of the invention of the MIAs and recourse can be had
to any conventionally known system. In particular and given that
the multi-triangular elements are excited at two different points,
it is possible to make use of an independent distribution network
for each band and polarisation. Another alternative consists in
employing a broadband or dual band distribution network, by
coupling a combiner/diplexer which interconnects the network and
the two excitation points of the multilevel antenna. The antenna
may then come with four input/output connectors (one for each band
and polarisation), or else combined in only two connectors (one for
each independent polarisation) by means of combiner/diplexer
network in each polarisation.
[0049] AEM3 Mode
[0050] The AEM3 configuration, as shown in FIG. 9, is very similar
to the AEM2 (the position of the multilevel elements and the type
of element itself is the same as in the previous case), with the
difference that the right-hand column is reversed with respect to
that on the left. In this manner an antenna with dual band and
polarisation is obtained, the total width of the antenna being
reduced with respect to the previous case (in this particular
example the width is reduced by about 10%). In order to increase
the isolation between the columns of double polarisation it is
convenient that oblique fins be inserted between contiguous
elements. In that case, lateral fins are also incorporated in all
the elements which work in GSM 1800, fins which contribute to
narrowing the radiation beam in the horizontal plane (plane at
right angles to the longitudinal axis of the array).
[0051] Nor is the signal distribution system especially
characteristic of the MIA configuration and the same system can be
used as in the previous case.
[0052] AEM4 Mode
[0053] Another example of multiband interleaved array is that
termed herein AEM4 and which is shown in schematic form in FIG. 11.
In this case, the multiband element is a stacked square patch
antenna (FIG. 10), though it is obvious for anyone familiar with
the subject that patches of other shapes could be employed. Square-
or circular-shaped types are preferred in the event that is wished
to work with double polarisation. In the example of FIG. 10 the
particular case is described of square patches.
[0054] The lower patch is of appropriate size for its resonant
frequency (associated typically with the patch fundamental mode) to
coincide with the lower band (GSM 900 in this specific case);
moreover, this patch acts in turn as ground plane of the upper
patch. The latter is of a size such that its resonance is centred
in the upper band (GSM 1800). The elements of the array are mounted
on a metallic or metal-coated surface which acts as ground plane
for all the elements of the array. The feeder system is
preferentially of the coaxial type, a cable being employed for the
lower patch and band and another for the upper patch and band. The
excitation points are collocated on the bisectors of the patches
(for example, the approximate excitation points are marked by means
of circles on the plan view of the antenna) if vertical or
horizontal polarisation is desired, or on the diagonals if, on the
other hand, linear polarisation inclined at 45.degree. is desired.
In the event it is desired that the array work with double
polarisation, each of the patches is excited additionally on the
bisector or diagonal opposite (orthogonal) to the first.
[0055] The feeding of the elements of the array AEM4 is not
characteristic of the invention of the MIAs and recourse can be had
to any conventionally known system. In particular and given that
the stacked patch antenna is excited at two different points, it is
possible to make use of an independent distribution network for
each band and polarisation. Another alternative consists in
employing a broadband or dual band distribution network, by
coupling a combiner/diplexer which interconnects the network and
the two excitation points of the multilevel antenna.
[0056] The antenna may then come with four input/output connectors
(one for each band and polarisation), or else combined in only two
connectors (one for each independent polarisation) by means of a
combiner/diplexer network in each polarisation.
[0057] AEM5 Mode
[0058] The AEM5 configuration, as shown in FIG. 12, adopts the same
approach as the AEM4, though all the elements are rotated through
45.degree. in the plane of the antenna. In this manner the
radiation pattern is modified in the horizontal plane, in addition
to rotating the polarization through 45.degree..
[0059] It is of interest to point out that both in the AEM4
configuration and in the AEM5, the multiband element constituted by
the stacked patches is really only strictly necessary in those
strategic positions in which elements originating in the
conventional mono-band arrays coincide. In the remaining positions,
it shall be possible to employ indistinctly multiband or mono-band
elements that work at the frequency determined for its location, as
long as its radiation pattern is sufficiently like that of the
stacked patch antenna in order to avoid the appearance of
diffraction lobes.
[0060] It is not deemed necessary to extend further the content of
this description in order that an expert in the subject can
comprehend its scope and the benefits arising from the invention,
as well as develop and implement in practice the object
thereof.
[0061] Notwithstanding, it must be understood that the invention
has been described according to a preferred embodiment thereof, for
which reason it may be susceptible to modifications without this
implying any alteration to its basis, it being possible that such
modifications affect, in particular, the form, the size and/or the
materials of manufacture.
* * * * *