U.S. patent number RE29,296 [Application Number 05/596,263] was granted by the patent office on 1977-07-05 for dual slot microstrip antenna device.
This patent grant is currently assigned to Ball Brothers Research Corporation. Invention is credited to Carl N. Bullai, Jack K. Krutsinger, Robert E. Munson.
United States Patent |
RE29,296 |
Krutsinger , et al. |
July 5, 1977 |
**Please see images for:
( Certificate of Correction ) ** |
Dual slot microstrip antenna device
Abstract
A dual slot antenna assembly is disclosed herein and generally
includes a pair of concentrically positioned and radially spaced
cylindrical conductors defining a pair of circumferential slots
which are longitudinally spaced one-half wavelength apart at the
anticipated operating frequency of the antenna device. An
electrical signal feed assembly is connected with the conductors
for exciting the slots so as to provide overlapping radiation
patterns emanating in the same direction.
Inventors: |
Krutsinger; Jack K. (Boulder,
CO), Bullai; Carl N. (Longmont, CO), Munson; Robert
E. (Boulder, CO) |
Assignee: |
Ball Brothers Research
Corporation (Boulder, CO)
|
Family
ID: |
26796157 |
Appl.
No.: |
05/596,263 |
Filed: |
July 16, 1975 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
099481 |
Dec 18, 1970 |
03810183 |
May 7, 1974 |
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Current U.S.
Class: |
343/700MS;
343/708; 343/769 |
Current CPC
Class: |
H01Q
9/0471 (20130101) |
Current International
Class: |
H01Q
9/04 (20060101); H01Q 013/10 (); H01Q 001/28 () |
Field of
Search: |
;343/769,801,846,7MS,708 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lieberman; Eli
Attorney, Agent or Firm: Haynes; James D.
Claims
What is claimed is:
1. A dual slot antenna assembly comprising: a pair of laterally
spaced-apart conductive elements electrically isolated with respect
to one another, said conductive elements defining a pair of
radiation slots longitudinally spaced-apart a predetermined
distance approximately equal to one-half wavelength at the
anticipated operating frequency of said assembly, each of which
slots emanates radiation therefrom such that the radiation patterns
developed are in substantially the same direction, said slots being
of greater length than the spacing between said conductive
elements; and electrical signal feed means connected with said
conductors for electrically exciting both of said slots, said
electrical signal feed means including a plurality of leads
connected to an edge of one of said conductive elements adjacent
one of said slots and spaced-apart at intervals at least
substantially equal to one wavelength at said anticipated operating
frequency.
2. An assembly according to claim 1 including nonconductive means
for supporting said laterally spaced-apart conductive elements,
said conductive elements and nonconductive means each comprising
part of a single sheet of dielectric material metallically cladded
on opposite sides thereof.
3. A dual slot antenna assembly comprising: a first substantially
cylindrical conductor, the axial length of which is approximately
equal to one-half wavelength at the anticipated operating frequency
of said assembly; a second substantially cylindrical conductor, the
axial length of which is at least equal to the axial length of said
first conductor, said second conductor being positioned
concentrically within and radially spaced from said first conductor
and electrically isolated with respect thereto so as to define a
pair of circumferential slots spaced one-half wavelength apart at
said anticipated operating frequency and providing independent
radiation patterns emanating in the same direction; and electrical
signal feed means connected with said conductor for electrically
exciting both of said slots, said electrical signal feed means
including a plurality of leads connected to an edge of said first
conductor adjacent one of said slots and circumferentially
spaced-apart at intervals at least substantially equal to one
wavelength at said anticipated operating frequency.
4. An assembly according to claim 3 including nonconductive means
for supporting said first and second conductors, said conductors
and nonconductive means each comprising part of a single sheet of
dielectric material metallically cladded on opposite sides thereof.
.Iadd. 5. A dual slot antenna assembly comprising:
a pair of laterally spaced-apart conductive elements separated with
respect to one another by a sheet of dielectric material,
one of said conductive elements being of larger dimensions and
underlying the other element and defining an electrical reference
or ground surface;
said conductive elements defining a pair of radiation slots between
opposing edges of said other element and said reference surface,
said radiation slots being longitudinally spaced-apart a
predetermined distance approximately equal to one-half wavelength
at the anticipated operating frequency of said assembly,
each of which radiation slots emanates radiation therefrom such
that the radiation patterns developed are in substantially the same
direction;
said radiation slots having a length dimension equal to the entire
length of said opposing edges, which length dimension is greater
than the spacing between said conductive elements; and
a single electrical signal feed assembly integrally connected with
said other conductive element at only one of said opposing edges
for electrically exciting both of said radiation slots from a
single signal
feed junction. .Iaddend. .Iadd. 6. An assembly according to claim 5
wherein said conductive elements and said sheet of dielectric
material each comprise part of a single sheet of dielectric
material metallically cladded on opposite sides thereof. .Iaddend.
.Iadd. 7. An antenna structure comprising:
an electrically conducting ground surface,
a single layer electrically conducting surface comprising both an
r.f. radiator conducting area and an r.f. feedline conducting area
integrally connected thereto and formed therewith,
a dielectric sheet disposed between said ground surface and the
single layer electrically conducting surface,
said conducting surfaces defining a pair of radiation slots between
opposing edges of said r.f. radiator and said ground surface, said
radiation slots being longitudinally spaced apart by a
predetermined distance approximately equal to one-half wavelength
at the anticipated operating frequency of said antenna
structure;
each of which radiation slots emanates radiation therefrom such
that radiation patterns developed are in substantially the same
direction;
said radiation slots having a length dimension equal to the entire
length of said opposing edges, which length dimension is greater
than the spacing between said surfaces; and
said r.f. feedline being connected to the outside edge of one only
of said opposing edges of said r.f. radiation conducting area to at
least one predetermined point on the periphery of said radiator
conducting area. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to antenna assemblies and more
particularly to a new and improved dual slot antenna assembly.
2. Description of the Prior Art
The use of antenna assemblies for both transmission and reception
of radio signals is well known, and such antenna assemblies have
taken many diverse dimensions and/or shapes to accomplish given
objectives. Among such antennas known in the art are those useful
in conjunction with propelled vehicles including missiles and more
particularly missiles which carry instrument payloads for short
term measurements of very high altitude environment data, which
data is transmitted from an antenna mounted on a missile to
receiving stations on the ground, which receiving stations are
often ground tracking stations. However, monitoring has been found
to be difficult due to signal nulls encountered as the vehicles
assume different roll and aspect orientations.
Although the problem has been attacked in many ways, including the
use of refined circuitry such as automatic gain control amplifiers
which have to some effect alleviated the problem of antenna
deficiencies, there still has been a need to improve the antennas
so as to develop radiation patterns without signal lobes of varying
strength. More particularly, the antenna should be characterized by
an isotropic antenna radiation coverage, that is, a pattern of
constant relative power for any orientation of the antenna. As
such, the pattern coverage is then relatively constant regardless
of the roll or aspect orientation of the rocket, thereby
facilitating data monitoring at a tracking station. The avoidance
of signal nulls as a characteristic of the antenna eliminates an
important deficiency that has previously caused temporary loss of
signal information, and in the case of an unrecovered rocket,
permanent loss thereof.
Although some previous attempts have been made to design antennas
having patterns more nearly isotropic for use in rockets carrying
environmental data sensors and associated instruments for telemetry
purposes and the like, such antennas have not completely solved the
problems in all cases due to one or more of such diverse reasons as
failing to satisfy strict aerodynamic design requirements,
exhibiting intolerable signal variations in the aspect patterns
(the signal pattern measured about the missile in a plane
containing the missile) and/or in the roll patterns (the signal
pattern measured about the missile in a plane perpendicular to the
missile axis), requiring complicated and often expensive components
due to complex design requirements, and/or requiring excessive time
and/or material in assembly so as to make antenna costs too high
for at least some intended uses. For example, the aspect and roll
radiation patterns in some antennas of recent design have been
found to fluctuate as much as 30 db from isotropic radiation, while
the required dimensions and/or costs inherent in other such
antennas have made these antennas unusable, or at least
undesirable, for many intended uses.
SUMMARY OF THE INVENTION
The present invention overcomes the aforementioned disadvantages,
as well as other disadvantages, by providing an antenna which has
an improved signal radiation pattern and which is both simple in
design and economical to make. In addition, the antenna is
particularly useful in airborne telemetry vehicles, which assume
many orientations relative to any given tracking station, since it
may be easily flush-mounted to the vehicle so as to provide a low
profile and thereby avoid any substantial increase in air drag.
As will be seen hereinafter, a preferred embodiment of the antenna
assembly constructed in accordance with the present invention
generally comprises a pair of laterally spaced-apart conductive
elements defining a pair of longitudinally spaced radiation slots,
each of which is of greater than the spacing between the conductive
elements and each of which emanates radiation therefrom, the slots
being electrically excited by an electrical feed assembly.
The antenna, constructed in the aforedescribed manner not only
exhibits improved radiation patterns, but also is relatively simple
in design and economical to produce, as will become more apparent
hereinafter. It should be noted that the antenna assembly, as
constructed, is similar in many respects to the "Single Slot Cavity
Antenna Assembly" disclosed in an application, by Robert E. Munson
et al. Ser. No. 99,434 and filed concurrently herewith. However,
because of the dual slot feature, the antenna assembly of the
present invention operates in an entirely different manner as will
be seen hereinafter, and may be utilized in different operational
environments. In addition, because of this dual slot feature,
assemblage of the antenna assembly of the present invention is
different than that of the single slot antenna assembly referred to
hereinabove.
An object of the present invention is to provide a new and improved
antenna assembly having an improved signal radiation pattern.
Another object of the present invention is to provide a new and
improved antenna assembly which is both simple in design and
economical to manufacture.
Still another object of the present invention is to provide a new
and improved antenna assembly which utilizes a pair of
longitudinally spaced circumferential slots for the emanation of
radiation patterns.
Another object of the present invention is to provide an antenna
assembly of the last-mentioned type wherein the electromagnetic
energy emanating from the aforementioned slots radiate in the same
direction so as to provide an overall radiation pattern of improved
quality.
Still another object of the present invention is to provide an
antenna assembly of the last-mentioned type wherein slot excitation
is provided with only one electrical signal feed assembly.
These and other objects and features of the present invention will
become more apparent to those skilled in the art from the following
description of a preferred embodiment, as illustrated in the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a missile utilizing a dual slot
antenna assembly constructed in accordance with the present
invention;
FIG. 2 is an enlarged perspective view of the antenna assembly
apart from the missile illustrated in FIG. 1;
FIG. 3 is a cross-sectional view taken generally along line 3--3 in
FIG. 2;
FIG. 4 is a partially broken-away enlarged sectional view taken
generally along line 4--4 in FIG. 3 and particularly illustrating
the radiation patterns emanating from the antenna's dual slots;
FIG. 5 is an enlarged flattened out view of the antenna illustrated
in FIG. 2, specifically displaying a portion of the electrical
signal feed assembly used therewith;
FIG. 6 is a diagrammatic view of a portion of the antenna of FIG.
2, illustrating the manner in which the dual slots operate; and
FIG. 7 is a graphic representation showing an experimental antenna
gain radiation pattern utilizing the antenna of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawings, wherein like components are designated
by like reference numerals throughout the various figures, a dual
slot antenna assembly 10, constructed in accordance with the
present invention, is shown in FIG. 1 flush-mounted to a missile 12
having a metallic outer cylindrical body or skin 14 and a nose
portion 15. As will be been hereinafter, antenna assembly 10 is
characterized by an isotropic antenna radiation coverage, that is
an omnidirectional dipole type pattern of constant relative power
for any orientation of the antenna. As such, the pattern coverage
is then relatively constant regardless of the roll or aspect
orientation of missile 12 thereby facilitating data monitoring at a
tracking station. For purposes of description, the antenna will be
considered as a transmitting device, it being readily apparent to
those skilled in the art that the same may be used for reception
purposes also.
Turning to FIGS. 2 through 5, antenna 10 is shown to include a thin
inner cylindrical conductor 18, preferably constructed of copper,
the conductor being adapted for flush mounting directly to and
about the skin 14 of missile 12, as illustrated in FIG. 1, and
thereby providing, in effect, a ground plane having an axial length
equal to that of the missile. Antenna 10 further includes a thin
second or outer cylindrical conductor 20, which is also preferably
constructed of copper, and which displays an axial length
substantially equal to one-half wavelength at the anticipated
operating frequency of the antenna. Conductor 20 is positioned
concentrically about one end portion of conductor 18 and is
radially spaced therefrom so as to define a one-half wavelength
coaxial cavity 22, as illustrated best in FIG. 3. In accordance
with a feature of the present invention, cavity 22 is electrically
opened at both ends thereof so as to provide a pair of exposed
circumferential slots 23 and 25 which are longitudinally spaced
one-half wavelength apart at the antenna's anticipated operating
frequency and which, as will be seen hereinafter, cooperate to
produce the aforestated omnidirectional radiation pattern.
While coaxial cavity 22 may be left void of material, for ease of
construction a dielectric layer 24, preferably polytetrafluoro
ethylene (commercially available Teflon), and particularly
Teflon-fiberglass, is positioned between and supports conductors 18
and 20. In this regard, it is to be noted that the actual length of
coaxial cavity 18 must be corrected for the impedance-producing
effect of the dielectric layer. This may be accomplished by
resorting to the relationship of effective wavelength .lambda.c as
a function of actual wavelength .lambda., which relationship
is:
wherein .lambda.c is the corrected wavelength in a cavity filled
with dielectric material, .lambda. is the actual wavelength in a
cavity void of material and .epsilon..sub.R is the dielectric
constant of the cavity filled material. By utilizing the
above-stated equation, the length of cavity 22 easily can be
corrected so as to be "effectively" one-half wavelength. However,
for purposes of clarity, only the term "one-half wavelength cavity"
will be used hereinafter, it being understood that when the cavity
is filled with dielectric material, such as material 24, an
effective one-half wavelength cavity is contemplated.
Thus, for operation at a carrier frequency of, for example, 2.2 GHz
and utilizing a dielectric such as polymerized tetrafluoro
ethylene, .lambda. is approximately equal to 5.4 inches and
.epsilon..sub.R is approximately 2.5 inches. Solving the
aforestated equation yields of .lambda.c of approximately 3.4
inches. Therefore, the effective one-half wavelength cavity of this
example is approximately 1.7 inches in length with slots 23 and 25
being separated the same distance.
Circumferential slots 23 and 25 may be excited by signal energy
produced at a source 30, as seen in FIG. 3, which may be located
within missile 12 and which may be of conventional type such as,
for example, a unit having an appropriate power source and radio
frequency oscillator modulated in accordance with data signals from
external environmental sensor devices. In this regard, a single
electrical signal feed assembly 32, operating in the TEM mode, is
provided for coupling source 30 to the aforementioned slots, as
will be seen hereinafter.
As illustrated best in FIG. 3, feed assembly 32 includes a coaxial
transmission line 34 having outer and inner conductive cables 36
and 38 extending from within source 30 where they are connected to
the appropriate components. The otherwise free end of outer
conductive cable 36 is electrically connected to inner conductor 18
while the otherwise free end of inner conductive cable 38 is
connected to the input of a combination multiple feed and
impedance-matching network 40 which is part of assembly 32 and
which is to be described hereinafter.
The connections of the inner and outer conductive cables of
transmission line 34 with conductor 18 and network 40,
respectively, may be accomplished in any suitable manner, so long
as the inner conductive cable is appropriately insulated from inner
conductor 18. In this regard, a jack assembly illustrated in FIG.
3, is provided and generally comprises an externally threaded
female connector 42 having an integral shoulder 44 suitably mounted
to the inner surface of conductor 18 and an internal insulating
sleeve 46, the opening of which is axially aligned with an aperture
48 provided radially through antenna 10. Female connector 42 is
adapted to receive a cooperating internally threaded male connector
50 mounted to the otherwise free end of conductive cable 36, as
illustrated in FIG. 3. In this manner, the last mentioned
conductive cable is electrically connected to inner conductor 18
while, on the other hand, inner conductive cable 38 of coaxial
transmission line 34 is positioned through insulating sleeve 46 and
aligned aperture 48 for connection with combination multiple feed
and impedance matching network 40.
Turning to FIG. 5, attention is directed to network 40 which is
supported on the exposed side of dielectric layer 24 and which
comprises a plurality of thin ribbon-like conductive leads
constructed preferably of and displaying the same thinness as outer
cylindrical conductor 20. In this regard, it has been found that
the most favorable radiation patterns emanating from slots 23 and
25 of coaxial cavity 22 are developed when the slots are excited in
the TEM mode with a plurality of uniform phase and amplitude
signals provided at feed points generally designated by the
reference numeral 53. As illustrated, these feed points are
separated about the periphery of circumferential slot 25 (on outer
conductor 20) at intervals substantially equal to one wavelength
(as corrected for the dielectric material 24 in cavity 22) at the
aforestated anticipated operating frequency. Accordingly, network
40 includes a first plurality of leads 52, common ends of which are
preferably integrally formed with, but in any case, terminate at
feed points 53.
Assembly 40 further includes a plurality of T-shaped leads 54 (two
of which are shown in FIG. 5), a third plurality of leads 56 and an
input lead 58, all of which combine to connect the first plurality
of leads 52 to the inner conductive cable 38 of coaxial
transmission line 34 at a signal feed junction designated by the
reference numeral 59. As illustrated in FIG. 5, the head of each
T-shaped lead connects a pair of adjacent leads 52 while the leads
56 substantially form a continuous band connecting the base of each
T-shaped lead to input lead 58. In this regard, it is to be noted
that dielectric layer 24 maintains the predetermined orientation
between the aforestated leads as well as the inner and outer
conductor.
Leads 52, 54, 56 and 58 are suitably dimensioned (length, width and
thickness) so as to provide continuous impedance matching between
coaxial transmission line 34 and coaxial cavity 22. With the
impedance of coaxial transmission line 34 being appropriately
chosen so as to match the impedance of source 30, it is readily
apparent that there is substantially a perfect impedance match
between the source and antenna 10 which, of course, provides for a
more efficient antenna. In addition, the distances between input 58
and each feed point 53 are equal. In this manner, combination
multiple feed and impedance matching network 40 separates the input
signal from coaxial transmission line 34 into a plurality of equal
phase and amplitude signals and transfers the same to feed points
53 for exciting slots 23 and 25 in the most favorable manner
possible.
While network 40 is formed in the manner illustrated in FIG. 5 and
includes four paths to conductor 20, it is to be understood that
the invention, as contemplated, is not limited thereto. For
example, there may be any number of feed points and paths depending
upon the circumference of conductor 20. Accordingly, the paths
between input 58 and feed points 53 may take on various dimensions
and designs so long as the aforedescribed impedance matching and
input signal separation functions are preserved. In this regard,
the latter function is assured if the paths are of equal
distances.
With antenna device 10 constructed in the aforedescribed manner,
attention is now directed to a preferred method of making the same.
As stated above, inner and outer cylindrical conductors 18 and 20
are preferably constructed of copper. More specifically, these
conductors are preferably parts of a sheet of microstrip, that is,
copper-clad layers supported by and on opposite sides of a sheet of
dielectric material such as, polytetrafluoro ethylene (commercially
available Teflon), the dielectric sheet being dielectric material
24 illustrated in FIG. 2.
The method of making antenna 10 utilizing the aforedescribed sheet
of microstrip includes the step of removing various portions of one
of the copper-claded layers from the intermediate dielectric
insulating sheet so as to provide an integral configuration
including outer conductor 20 and combination multiple feed and
impedance matching network 40. This may be accomplished in any
suitable manner, but is most preferably accomplished by resorting
to conventional printed circuit board techniques such as, for
example, a photo-etching process. Thereafter, aperture 48 is
provided through the laminated material at the input or signal feed
junction of assembly 40 and a suitable jack assembly of the type
described above is soldered or otherwise suitably mounted over the
aperture on the opposite side of network 40, in the manner
illustrated in FIG. 3.
If the antenna assembly is to be used in the manner shown in FIG.
1, that is, as a wrap-around or cylindrical flush-mounted antenna,
the longitudinal edges of the microstrip or laminated material are
suitably connected together by any suitable means such as apertures
61 provided through opposite sides of the material as illustrated
in FIG. 5. In this regard, construction of antenna device 10 is
facilitated by connecting only the lengthwise edges of the
intermediate dielectric layer 24 as illustrated by gaps 60 and 62
representing the unconnected lengthwise edges of inner and outer
conductors 18 and 20, respectively. So long as these gaps are small
relative to the operating wavelengths of the antenna, they may be
neglected as having no substantial effect on either the antenna
impedance or radiation pattern. In this regard, the longitudinal
edges of the laminated material may be connected together after the
antenna assembly is wrapped around the body of the propelled
vehicle or they may be initially connected together whereupon the
assembly is then slid over and about the vehicle's body.
Having described the rather simple and economical manner in which
antenna device 10 is constructed, attention is now directed to its
operation, which may be best described in conjunction with FIG. 6
illustrating a portion of the antenna assembly diagrammatically. As
stated above, circumferential slots 23 and 25 are excited in the
TEM mode by a plurality of equal phase and amplitude signals (such
as radio frequency signals) which are fed to the cavity at points
53 adjacent slot 25 by electrical signal feed assembly 32. For
purposes of clarity, FIG. 6 shows a single conventional coaxial
cable 70 which is connected with conductors 18 and 20 adjacent slot
25 and which, for purposes of explanation, represents a portion of
feed assembly 32.
From an impedance standpoint, because circumferential slots 23 ad
25 are electrically in parallel and one-half wavelength apart, slot
25 presents only one-half of the impedance which would otherwise
exist if the slot 23 were replaced by a short circuit. This, of
course, is an important consideration when matching the impedance
of antenna 10 with that of the electrical signal feed assembly 32.
Upon exciting coaxial cavity 22, an electric field develops about
slot 25 in the direction indicated by arrow E.sub.1. This, of
course, only represents the instantaneous electric field and will
change in accordance with the oscillatory signals exciting the
cavity. Since circumferential slot 23 is positioned one-half
wavelength from slot 25, the instantaneous electric field shifts
180.degree. thereat, as indicated by arrow E.sub.2. In this manner,
the electric fields at the two slots are always in opposite
directions. Accordingly, the electromagnetic energy emanating from
the two slots radiate in the same direction, as indicated by arrows
R.sub.1 and R.sub.2, respectively, and therefore overlap in an
additive manner so as to provide a stronger radiation pattern, as
illustrated in FIG. 4.
In the case where antenna assembly 10 is utilized in combination
with missile 12, as illustrated in FIG. 1, it has been found that
the antenna's dual slot feature provides a typical omnidirectional
dipole-type radiation pattern, however, displaying more broadside
gain and less nulls in the roll axis due to dual slot cooperation.
In this regard, it is to be noted that assembly 10 operates
effectively at any desired frequency and operates particularly well
at frequencies within the VHF, UHF and microwave bands generally
and at the aforestated frequency of 2.2 GHz specifically.
Referring to FIG. 6, the aspect radiation pattern developed by
antenna device 10 utilized in the manner illustrated in FIG. 1 is
shown, wherein the axis of the missile was positioned substantially
within the plane containing the pattern and wherein the assembly
was operated at a frequency of 2.2 GHz. It is to be understood that
this particular frequency is provided for illustrative purposes
only and is not intended to limit the invention, the assembly
operating equally well at other desired frequencies.
The pattern, representing the antenna gain relative to linear
isotropic radiation, is substantially representative within one db
of the infinite number of aspect radiation patterns which may be
utilized to define a figure of revolution about the missile axis.
More particularly, the radiation pattern of FIG. 7 is substantially
representative of the pattern contained in any plane defining a
cross section for any figure of revolution produced by all aspect
patterns containing the axis of the missile.
It readily may be appreciated that deep nulls exist only directly
forwardly (0.degree.) and rearwardly (180.degree.) of the missile,
that is, at the tip and tail thereof. As is well known, tip and
tail pattern nulls in a telemetry missile are usually of little
concern. As can also be seen from FIG. 7, the remainder of the
signal pattern displays an average strength variation between peaks
and nulls in the aspect plane of less than 5 db. Thus, the improved
antenna device is highly favorable for receipt of transmission of
electromagnetic signal energy to or from the missile without any
appreciable loss in the signal due to the vehicle orientation.
It is to be understood that while antenna device 10 has been
described both operationally and in construction as a cylindrical
flush mountable-type antenna displaying an omnidirectional
radiation pattern, the invention is not limited thereto.
Specifically, antenna device 10 may be substantially flat or only
partially curved so as to provide a more directional radiation
pattern while retaining the various advantageous features described
above. In addition, although only one embodiment of the invention
has been shown and described, various modifications as may appear
to those skilled in the art are intended to be within the
contemplation of the invention as defined in the scope of the
claims.
* * * * *