Note: Descriptions are shown in the official language in which they were submitted.
CA 02298991 2000-02-18
TITLE OF THE INVENTION
A BROADBAND COMPACT SLOT DIPOLE/MONOPOLE AND ELECTRIC
DIPOLE/MONOPOLE COMBINED ANTENNA
FIELD OF THE INVENTION
The present invention relates generally to radio frequency antennas and, in
particular,
to broadband compact antennas for use in a communications apparatus.
BACKGROUND OF THE INVENTION
to The increasing demand for mufti-channel and broadband applications in
wireless
communications has necessitated the design of broadband antennas. With the
current
emphasis on antenna miniaturization, an antenna that possesses a wide
impedance
bandwidth, a compact structure and a high radiation efficiency is therefore
very desirable.
However, the design and construction of such an antenna are a significant
challenge.
~5 Theoretical limitations exist in this endeavor [1, 2].
The designer of practical communications equipment that has wide consumer
usage
must pay careful attention to the ergonomics of the design of the units, such
as the
handsets. In general, the consumer requires increasingly more compact
equipment that
provides more functions. The antenna is a major limitation with respect to its
size, its
2o efficiency and its ability to cover a wide frequency range. In the near
future, the handsets
may be required to cover the cellular bands (800 to 900 MHz), the GPS (Global
Positioning Satellite) frequency (1525 MHz), the PCS (Personal Communication
System)
band (1800 to 2000 MHz) and possibly higher frequency bands. A single antenna
that
can cover many frequency bands is much more desirable than multiple antennas
that
25 cover each frequency band individually. For the above reason, it is an
object of the
present invention to provide a highly efficient, compact antenna having a wide
impedance
bandwidth for use in a mufti-channel or broadband communications apparatus.
A widely employed antenna on radio handsets and cellular phones is a quarter
wave
monopole mounted on the radio that uses the radio case (or circuit boards) as
the
3o equivalent of a small ground plane to provide a rough equivalent of a
dipole antenna.
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CA 02298991 2000-02-18
The usage of a. monopole on a ground plane and its equivalence to a dipole is
widely
known. The fact that a radio case is used instead of a ground plane causes
changes in the
radiation pattern and input impedance of the antenna, but in most cases
acceptable
changes or recoverable changes (through minor modification to the monopole)
are
introduced. Due to the large variations in their input impedances with
frequency, thin
dipoles and monopoles are considered to be narrowband. Nevertheless, the
impedance
bandwidth of a dipole or monopole can be substantially broadened by increasing
the
thickness of the conductor. The well-known cylindrical and bow-tie
(triangular) antennas
are broadband variants of wire dipole and monopole antennas. A typical bow-tie
antenna
1o comprising two triangular sheet of conducting material is depicted in FIG.
1 [3]. To
obtain a reduction in antenna size, a triangular sheet of metal can be placed
over a ground
plane conductor (as shown in FIG. 2) to form a equivalent monopole structure
of the
bow-tie antenna. Another broadband derivative of the dipole and monopole
antennas are
sleeve antennas. A sleeve dipole, formed by extending the inner and outer
conductors of
a coaxial line over a ground plane conductor, is shown in FIG. 3 and it has
broadband
properties superior to those of a half wave or full-wave dipole [4]. FIGS. 4 -
6 [5, 6]
illustrate some other varieties of a sleeve antenna.
A slot antenna is a complement of a dipole antenna with dimensions identical
to the
slot. Because of its low profile, slot antennas have many practical
applications in
2o wireless communications, especially where flush installations are needed.
According to
Babinet's principle [7], the radiation pattern of a slot antenna in an
infinite conducting
sheet is the same as that of the complementary dipole antenna, except that the
electric and
magnetic fields are interchanged. The input impedances of a slot antenna and
its
complementary dipole are related by
Zslot Zdip = T12 ~ 4 ( 1 )
where ZS~o~ and Zap are the input impedances of the slot antenna and the
complementary
dipole respectively, and r) is the intrinsic impedance of the surrounding
medium (= 120
3o in free space). From the relationship as expressed by equation (1), it is
evident that the
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CA 02298991 2000-02-18
input impedance of the slot antenna is inversely proportional to that of the
complementary dipole, or vice versa. FIG. 7 depicts the input impedance of a
typical
dipole antenna, as a function of frequency, on a Smith Chart. The impedance
curve of the
complementary slot antenna is also shown in FIG. 8. By examining the two
impedance
spirals, it can be found that the slot antenna and the complementary dipole
always have
opposite reactances or susceptances. The dipole resonates, with a practical
input
impedance of roughly 70 ohms, when its electrical length is an odd number of
half
wavelengths, whereas the complementary slot is resonant and has a low input
resistance
when its electrical length is an even number of half wavelengths. Accordingly,
if the slot
to antenna and the dipole are combined in some ways to form a single radiating
structure, it
is feasible to cause the input reactance or susceptance of the resulting
antenna to be
cancelled or reduced to some extend over a wide frequency range and to achieve
a low
input resistance across very wide bandwidths. The present invention thus
employs both
the slot antenna and the dipole or monopole antenna as the building blocks of
the antenna
structure and combines them together to achieve a wide impedance bandwidth and
physical compactness. The slot antenna and the electric monopole or dipole
antenna are
connected together in a simple parallel connection or tight magnetic or
electric coupling.
It is to be noted that an antenna made of a combined slot dipole and electric
monopole
connection has been disclosed by Mayes [8 - 11 ] using a more complex series
and
2o parallel connection of the elemental antennas. Variations of this antenna
have been
presented by Hall [12 - 14]. The basic structure of this group of antennas
involves a
microstrip line with two inputs or outputs mounted under the ground plane [8].
The slot
is built into the ground plane to intercept ground currents flowing in the
ground plane
immediately above the "hot" conductor of the microstrip line. The slot antenna
is
therefore connected in series with the microstrip line. The monopole is
connected in
parallel to the microstrip line at a point coincident with the effective feed
point of the slot
antenna. The monopole emerges from below the ground plane through the slot.
This
antenna can produce a cardioid-like radiation pattern when fed on one of the
transmission
line arms and another cardioid-like radiation pattern oriented in the other
direction when
3o fed by the other transmission line arm. Variations of this antenna have
been constructed
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CA 02298991 2000-02-18
by Hall [ 12] axid by Mayes [ 11 ]. Four port extensions of this antenna have
been
developed by Mayes [llJ and by Hall [13]. This antenna can be constructed to
have a
large bandwidth by terminating one of the transmission lines in a matched
resistor [10].
This resistor will increase loss and lower the efficiency of the antenna
however. The
antenna described in this invention has a more simple connection of the
electric
monopole and the slot dipole and achieves large bandwidth without an
efficiency
reducing resistor. The simple connection of the slot and electric antennas
permits a great
range of electric monopole and dipole elemental antennas to be connected to a
range of
monopole and dipole slot antennas to provide a wide variety of combined
antennas.
SUMMARY OF THE INVENTION
In accordance with an aspect of the present invention, a broadband compact
antenna
comprises an electric dipole or monopole coupled or connected in parallel to a
slot
antenna. In other aspects, the slot antenna is composed of a flat, square or
rectangular
conducting sheet with a slot having a variety of possible shapes including a
bow-tie or
rectangle. The slot is preferably fed at the center by a coaxial transmission
line with its
outer conductor bonded to the sheet. In another aspect, to obtain broadband
characteristics and compactness, a dipole or monopole, formed using either
wire, flat
strips or shapes formed in sheets of metal, is located in close proximity to
the center of
2o the slot. In one embodiment of the present invention, a parasitic dipole is
magnetically
coupled to a slot antenna by placing a low dielectric spacer between the slot
and the
dipole. The spacer allows maximum coupling between the slot and the dipole,
while
preventing a direct electrical contact of the two elements. The parasitic
dipole and the
slot are oriented so that the polarizations of the two elements are identical.
In another
embodiment of the present invention, a dipole or monopole is connected to the
center of a
slot antenna and both antennas are energized by a common coaxial feed. The
dipole or
monopole is positioned in a plane at an angle or normal to that of the slot
antenna.
Practical and commercially available shielded (i.e., coaxial) transmission
lines have
characteristic impedances that cover a relatively small range of values, for
example 50 to
75 ohms. Broadband antennas must have an impedance that matches these
transmission
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CA 02298991 2000-02-18
lines for maximum practical application. Thus, the input impedance of a
broadband
antenna must be roughly in the range of 50 to 75 ohms. The electrical dipole
antenna has
input resistances of approximately 70 ohms when its electrical length is an
odd number of
half wavelengths and has high resistances when its electrical length is an
even number of
half wavelengths. The slot antenna can be made (by selection of its width) to
have input
resistances in the 50 to 75 S2 range when its electrical length is an even
number of half
wavelengths. The input resistances of the slot antenna are high when the slot
is an odd
number of half wavelengths long. Hence, if the electric dipole and the slot
antenna is
connected together in parallel, the element with the smaller impedance will
dominate and
1 o it is practicable to reduce the input impedance of the resulting antenna
to a resistance in
the 50 to 75 S2 range whenever the two elements are a integral multiple of
half
wavelength long. At intermediate frequencies, the input reactances or
susceptances of the
two elements will tend to cancel each other out and the resulting antenna will
possess an
input impedance of value that is within the practical range. It has been found
that, with
the above arrangements, a highly efficient, broadband compact antenna, suited
for use in
hand-portables or other communications equipment, can be achieved by varying
the
relative dimensions and shapes of the slot and the dipole or monopole. The
combination
of the slot and dipole or monopole antennas is therefore a more effective
radiator than
either one alone.
BRIEF DESCRIPTION OF THE DRAWINGS
There will now be described preferred embodiments of the invention, with
reference to
the Figures, by way of example and without intending to limit the generality
of the
invention, in which like reference characters denote like elements, and in
which:
FIG. 1 is a side view of a bow-tie antenna;
FIG. 2 is a side view of a triangular antenna mounted upon a ground plane
conductor;
FIG. 3 is a side view of a sleeve dipole antenna;
FIG. 4 is a side view of a broadband sleeve antenna;
FIG. 5 is a side view of a top-loaded sleeve antenna;
3o FIG. 6 is a side view of a partial sleeve aerial for use in an aircraft;
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CA 02298991 2000-02-18
FIG. 7 is a graph illustrating the input impedance of a dipole antenna as a
function of
frequency;
FIG. 8 is a graph illustrating the input impedance of a slot antenna as a
function of
frequency;
FIG. 9A is an isometric view of the first preferred embodiment of the present
invention;
FIG. 9B is a top view of the first preferred embodiment of the invention;
FIG. l0A is a side view of the slot antenna element;
FIG. 1 OB is a side view of the dipole antenna element;
1o FIG. 11 is a graph illustrating the return loss of the first preferred
embodiment of the
invention;
FIG. 12 is a graph illustrating the input impedance of the first preferred
embodiment of
the invention;
FIG. 13 is a graph illustrating the radiation pattern of the first preferred
embodiment of
the invention;
FIG. 14 is an isometric view of the second preferred embodiment of the
invention;
FIG. 15 is a side view of the dipole antenna element;
FIG. 16 is a graph illustrating the return loss of the second preferred
embodiment of
the invention;
2o FIG. 17 is a graph illustrating the input impedance of the second preferred
embodiment of the invention;
FIG. 18 is a graph illustrating the radiation pattern of the second preferred
embodiment of the invention;
FIG. 19 is an isometric view of the equivalent monopole structure of the first
preferred
embodiment of the invention;
FIG. 20 is an isometric view of the equivalent monopole structure of the
second
preferred embodiment of the invention;
FIG. 21 is an isometric view of the third preferred embodiment of the
invention;
FIG. 22 is a graph illustrating the return loss of the third preferred
embodiment of the
invention;
6
CA 02298991 2000-02-18
FIG. 23 is an isometric view of the fourth preferred embodiment of the
invention;
FIG. 24 is a graph illustrating the return loss of the fourth preferred
embodiment of the
invention;
FIG. 25 is an isometric view of the fifth preferred embodiment of the
invention;
FIG. 26 is a graph illustrating the return loss of the fifth preferred
embodiment of the
mventlon;
FIG. 27 is an isometric view of the sixth preferred embodiment of the
invention;
FIG. 28 is a graph illustrating the return loss of the sixth preferred
embodiment of the
invention;
1o FIG. 29 is an isometric view of the seventh preferred embodiment of the
invention;
FIG. 30 is an isometric view of the eighth preferred embodiment of the
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Refernng to FIGS. 9A & 9B, a compact broadband antenna 10 is shown comprising
a
parasitic dipole 1, located in close proximity to the center of a slot antenna
2. The slot
antenna 2 (as shown in FIG. l0A) is composed of a flat, square conducting
sheet 3 (here
comprising copper) with a slot 4 having a shape of a bow-tie, at the center of
the sheet 3.
The bow-tie slot 4 has a flare angle of 90°. The slot 4 is energized at
the center and
coupled to an RF (radio frequency) feed, a coaxial transmission line 5. As
depicted in
2o FIG. 10A, the outer conductor 6 of the coaxial transmission line 5 is
bonded to the
conducting sheet 3 on one side of the slot 4, such as by soldering, while the
inner
conductor 7 of the line 5 is connected to the other side of the slot 4. The
transmission
line 5 is bent and wrapped around the edges of the conducting sheet 3, so that
the electric
field of the antenna 2 will not induce any current flow on the coaxial line 5.
Besides, a
plane of zero potential that is normal to the conducting sheet 3 and passes
through the slot
4, is created so as to make the transformation of the entire antenna structure
10 into an
equivalent monopole structure feasible.
As shown in FIG. lOB, in the preferred embodiment, the parasitic dipole 1
comprises a
flat sheet of conducting material (here comprising copper) possessing a shape
of a bow
3o tie with a flare angle of 90°. To achieve broadband characteristics,
the parasitic dipole 1
CA 02298991 2000-02-18
is approximately three times larger in length and width than the slot 4. The
center of the
dipole 1 is positioned in close proximity to the center of the slot 4 and the
two elements 1
& 2 are separated by a low dielectric spacer 8 (FIG. 9B). The dielectric
spacer 8 prevents
direct electrical contact between the two elements 1 & 2, while maintaining a
maximum
magnetic and electric coupling between the two elements 1 & 2. The dipole 1
and the
slot 4 are oriented so that the polarizations of the two elements 1 & 2 are
identical. With
the coaxial feed 5 located as illustrated in FIG. 10A, a potential difference
is created
across the slot 4 and current will flow from the higher potential side of the
slot 4 to the
lower potential side, around the edges of the slot 4. As a result, a magnetic
flux will be
1o created within the slot 4. The magnetic flux will encircle the parasitic
dipole 1 and thus
induce a current flow on the dipole 1. It has been found that, with the
arrangement and
configuration discussed above, the impedance bandwidth of the resulting
antenna 10 is
very substantial.
FIG. 11 shows the return loss of the antenna 10 over a frequency range of 0.5
to 4.5
GHz. The antenna has a 10 dB return loss bandwidth of over 1 GHz from 1.76 to
2.78
GHz. In addition, the bandwidth ratio for voltage standing wave ratio (VSWR) <
2 is
found to be about 1:1.6. FIG. 12 illustrates the input impedance of the
antenna # from 0.5
to 4.5 GHz on a Smith Chart. From FIG. 12, it is apparent that the antenna 10
has a
medium value of resistance and a small value of reactance over a wide
frequency range.
2o The azimuth, horizontal polarization field pattern of the antenna 10 at 1.8
GHz is depicted
in FIG. 13. The radiation pattern is found to be bi-directional with maxima at
0° and
180°, and minima at 90° and 270°.
To further enhance the broadband characteristics of the antenna 10, the
parasitic bow
tie dipole 1 shown in FIG. lOB is replaced by a top-loaded strip dipole, and
FIG. 14
discloses another preferred embodiment of the present invention. As
illustrated in FIG.
14, the parasitic dipole 21 of the antenna 20 is formed using a flat strip of
conducting
material (here comprising copper). In order to achieve compactness, the
parasitic dipole
21 (as shown in FIG. 1 S) further comprises two capacitive plates or hats 23 &
24 located
at the ends of the strip, giving a shape of a letter 'H' to the dipole 21. The
capacitive hats
23 & 24 are utilized to reduce the frequency of the lower operating frequency
point. In
8
CA 02298991 2000-02-18
the preferred embodiment, the separation between the slot antenna 22 and the
dipole 21 is
reduced, when compared to that of the antenna 10, to attain a wide impedance
bandwidth.
Despite the above modifications, the configuration and dimensions of the slot
antenna, as
well as the feeding arrangement, remains the same as the antenna 10.
FIG. 16 shows the return loss of the antenna 20 over a frequency range of 0.5
to 4.5
GHz. The antenna 20 has a 10 dB return loss bandwidth of over 2.8 GHz from
1.15 to
3.97 GHz. Besides, the bandwidth ratio for VSWR < 2 is found to be around
1:3.5.
Hence, the antenna 20 possesses a more broadband characteristics than the
antenna 10.
FIG. 17 illustrates the input impedance of the antenna 20 from 0.5 to 4.5 GHz
on a Smith
1o Chart. As indicated in FIG. 17, the impedance curve loops around the center
of the Smith
Chart several times, which implies that there are multiple resonances in this
frequency
range and the antenna 20 is very broadband. The azimuth, horizontal
polarization field
pattern of the antenna 20 at 1.8 GHz is depicted in FIG. 18. The radiation
pattern is
found to be bi-directional with maxima at 0° and 180°, and
minima at 90° and 270°.
The broadband antennas 10 & 20 can be transformed into their equivalent
monopole
structures that are more practical and small enough to fit into many portable
communications devices requiring broadband operations. FIGS. 19 & 20 show the
equivalent monopole structures of the broadband antennas 10 & 20 respectively.
In each
case, half of the broadband antenna is removed and is placed upon a ground
conducting
2o plane to obtain a monopole equivalent using the image theory. The resulting
antenna
structures 30 & 40 (FIGS. 19 & 20) are easier to feed (does not require
bending of the
coaxial transmission line) and have a better isolation to the rest of the
electronic circuitry
due to the presence of the ground plane conductor.
For the resulting antenna to acquire a wide impedance bandwidth, the slot
antenna and
the dipole may be connected together in parallel, instead of magnetically
coupled to each
other. A series connection between the slot antenna and the dipole would not
normally be
used as the input impedance of the resulting antenna would be too high for the
antenna to
be practical for most applications. FIG. 21 discloses another preferred
embodiment of the
present invention, in which a slot antenna is directly connected to a dipole
antenna. The
3o broadband antenna 50, as shown in FIG. 21, consists of a slot antenna 51
connected in
9
CA 02298991 2000-02-18
parallel with a dipole antenna 52. The slot antenna 51 is composed of a flat,
rectangular
conducting sheet 53 (here comprising copper) with a slot 54 having a shape of
a
rectangle. The dipole antenna 52 comprises two flat strips of conducting
material (here
comprising copper) with each connected to one side of the conducting sheet 53,
such as
by soldering, in close proximity to the center of the slot 54. The dipole
antenna 52 is
oriented in a plane normal to that of the conducting sheet 53. Both the slot
54 and the
dipole 52 are energized at the center by a common coaxial feed 55. FIG. 22
shows the
return loss of the antenna 50 over a frequency range of 0.5 to 10.5 GHz. The
antenna SO
is very broadband and has a return loss of more than 3 dB from 0.9 to above
10.5 GHz.
1o FIG. 23 depicts a modified version of the broadband antenna 50, in which
half of the
slot antenna is removed to attain a further reduction in antenna size. The
width of the slot
63 in the broadband antenna 60 (as shown in FIG. 23) is increased, when
compared to
that of the antenna 50, to acquire optimum performance. FIG. 24 illustrates
the return
loss of the antenna 60 over a frequency range of 0.5 to 10.5 GHz. The antenna
60 has a 3
dB return loss bandwidth of at least 1.63 GHz from 0.97 to 2.6 GHz and from
2.93 to
above 10.5 GHz. The combination of a half slot antenna 61 and a dipole 62
(FIG. 23)
thus gives a significant reduction in antenna size, while retaining the
broadband
characteristics of the resulting antenna 50.
FIG. 25 reveals another preferred embodiments of the present invention where a
2o monopole antenna is connected in parallel with a quarter-wave slot antenna.
As shown in
FIG. 25, the broadband antenna 70 is a modified version of the antenna 60 and
a further
reduction in antenna size is achieved by removing part of the conducting sheet
of the slot
antenna 61 in the antenna 60. The monopole antenna 72 is located in close
proximity to
the RF feed 73 that excites the quarter-wave slot antenna 71, on the narrower
side of the
conducting sheet 74. The monopole antenna 72 is oriented in a plane normal to
the slot
antenna 71. FIG. 26 depicts the return loss of the antenna 70 over a frequency
range of
0.5 to 10.5 GHz. The antenna 70 has a 3 dB return loss bandwidth of at least
1.77 GHz
from 0.91 to 2.68 GHz and from 3.1 to above 10.5 GHz.
FIG. 27 shows another preferred embodiment of the present invention, in which
a
3o monopole antenna is connected to the top edge of a half slot antenna
mounted upon a
CA 02298991 2000-02-18
ground plane conductor. The half slot antenna 81, as illustrated in FIG. 27,
comprises a
'M' shaped conducting sheet 83 placed on top of a ground plane conductor 84.
The
conducting sheet 83 is positioned in a plane normal to that of the ground
plane conductor
84 and has a rectangular slot 85 located at the bottom end of the sheet 83.
The monopole
antenna 82 is connected to the center of the top edge of the slot antenna 81
and is oriented
in the same plane as the slot antenna 81. Both the slot antenna 81 and the
monopole
antenna 82 are excited by a common RF feed 86 located at the center of the
slot 85. FIG.
28 depicts the return loss of the antenna 80 over a frequency range of 0.5 to
10.5 GHz.
The antenna 80 has a 3 dB return loss bandwidth of at least 1 GHz from 0.72 to
1.76 GHz
1o and from 2.21 to above 10.2 GHz. To obtain a further reduction in antenna
size, half of
the slot antenna 81 can be removed to form another broadband antenna 90, as
illustrated
in FIG. 29.
FIG. 30 discloses yet another preferred embodiment of the present invention
where
two triangular antennas are connected directly to a half bow-tie slot antenna.
As
illustrated in FIG. 30, the broadband antenna 100 consists of two triangular
antennas 102
& 103 connected to the center of a half bow-tie slot 104, on each side of the
half slot
antenna 101, over a ground plane conductor 105. Both the slot and the two
triangular
antennas are excited by a common RF feed 106 located at the center of the half
bow-tie
slot 104. Each of the two triangular antennas 102 & 103 is positioned in a
plane at an
2o angle to that of the slot antenna 101.
Hence, there has been disclosed a number of novel broadband antennas that are
highly
efficient and compact in size. By combining a slot antenna and a dipole or
monopole
antenna of different configurations and sizes together in various ways, the
resulting
antenna exhibits a very substantial impedance bandwidth, while maintaining a
compact
antenna structure. Due to their compactness, these broadband antennas are
practical and
suitable for use in many portable communications devices that require multi-
channel or
broadband operations. The arrangement and configuration of each broadband
antenna
may be altered to operate in other frequency bands and to have wider or
narrower
bandwidths.
n
CA 02298991 2000-02-18
Instead of a co-axial cable, the feed may be a microstrip or a coplanar
waveguide
in a similar fashion to the coax. If a stripline is used, the slot radiator is
made out of two
parallel plates. One could feed the antenna with a balanced feedline such as a
two round
conductor feedline coming in normal to the dipole and in line with the slot.
Any two
conductor balanced feedline could then be connected. Magnetic or electrically
coupled
parallel antennas give the equivalent of a parallel connection. For a direct
series
connection, the total impedance of the antenna is very high and not normally
practical.
The separation of the feed points should not be so great as to severely affect
the input
impedance of the electric dipole. The feed point could be offset from the
centre of the slot
1o providing is does not negatively affect the input impedence. It has been
found that if the
feed is connected to the bow tie antenna, unfavourable results are obtained.
Immaterial modifications may be made to the preferred embodiments shown here
without departing from the essence of the invention.
REFERENCES
[ 1 ]R. C. Hansen, "Fundamental Limitations in Antennas", Proceedings of the
IEEE,
Vol. 69, February 1981, pp. 170 - 182
[2]J. S. Mclean, "A Re-Examination of the Fundamental Limits on the Radiation
Q
of Electrically Small Antennas", IEEE Transactions on Antennas and
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[3]G. H. Brown and O. M. Woodward, "Experimentally Determined Radiation
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December 1952, pp. 425 - 452
[4]R. W. P. King, "Asymmetrically Driven Antennas and the Sleeve Dipole",
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[5]R. A. Burberry, "Progress in Aircraft Aerials", The Proceedings of the IEE,
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[6]J. V. N. Granger and J. T. Bolljahn, "Aircraft Antennas", Proceedings of
the IRE,
Vol. 43, May 1955, pp. 533 - 550
[7]J. D. Kraus, "Antennas", McGraw Hill, New York, 1988, Second Edition,
12
CA 02298991 2000-02-18
pp. 632 - 642
[8]P. E. Mayes, W. T. Warren and F. M. Wiesenmeyer, "The Monopole Slot: A
Small Broad-Band Unidirectional Antenna", IEEE Transactions on Antennas and
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[9]B. M. Halpern and P. E. Mayes, "The Monopole Slot as a Two-Port Diversity
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Technology, Vol. 33, No. 2, May 1984, pp. 76 - 83
[10] P. E. Mayes, "Small, Broadband, Unidirectional Antenna", U. S. Patent
3710340,
January 9, 1973
[11] P. E. Mayes, "Stripline Fed Hybrid Slot Antenna", U. S. Patent 4443802,
April
17, 1984
[12] E. A. Hall, "Reduced Height Monopole/Slot Antenna with Offset Stripline
and
Capacitively Loaded Slot", U. S. Patent 4587524, May 6, 1986
[13] E. A. Hall, "Reduced Height Monopole/Crossed Slot Antenna", U. S. Patent
4684953, August 4, 1987
[14] E. A. Hall and G. J. Schmitt, "Monopole/Crossed Slot Single Antenna
Direction
Finding System", U. S. Patent 5402132, March 28, 1995
13
