U.S. patent number 3,568,205 [Application Number 04/704,671] was granted by the patent office on 1971-03-02 for novel helical antenna.
This patent grant is currently assigned to Goodyear Aerospace Corporation. Invention is credited to Albert C. Buxton, Jerrold S. Foley.
United States Patent |
3,568,205 |
Buxton , et al. |
March 2, 1971 |
NOVEL HELICAL ANTENNA
Abstract
A directional electromagnetic radiating antenna with circular
polarization capable of operating over wide frequency bands and
having a greater electrical length than actual physical length. The
invention applies basically to a helical antenna utilizing one or
more unifilar or multifilar windings which possess the
characterizing feature of having an increased electrical path
length whereby the operating characteristics of the antenna will
resemble that of a larger physical structure than is actually
necessary to support the hardware comprising the antenna.
Inventors: |
Buxton; Albert C. (Akron,
OH), Foley; Jerrold S. (Stow, OH) |
Assignee: |
Goodyear Aerospace Corporation
(Akron, OH)
|
Family
ID: |
24830435 |
Appl.
No.: |
04/704,671 |
Filed: |
February 12, 1968 |
Current U.S.
Class: |
343/749; 343/834;
343/895 |
Current CPC
Class: |
H01Q
11/08 (20130101) |
Current International
Class: |
H01Q
11/08 (20060101); H01Q 11/00 (20060101); H01g
001/36 (); H01g 009/00 () |
Field of
Search: |
;343/834,895,731,749 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
576,159 |
|
Mar 1946 |
|
GB |
|
1,129,191 |
|
May 1962 |
|
DT |
|
Other References
"Antennas" Kraus McGraw Hill New York 1950 TK7872 A6K7 pages
173--174 and 179--183 .
Harris "A Helical Beams for Citizen's Radio" In ELECTRONICS March
1953 Vol 26 TK 7800 E58 pages 134--135 .
Kraus; ANTENNAS McGraw-Hill N.Y. 1950 TK 7872 Title page and pages
175--178 .
Walter TRAVELLING WAVE ANTENNAS N.Y. McGraw-Hill 1950 TK7872 A6 W33
Title page and pages 331--333.
|
Primary Examiner: Saalbach; Herman Karl
Assistant Examiner: Nussbaum; Marvin
Claims
We claim:
1. A directional electromagnetic radiating device with circular
polarization capable of operating over a side frequency band which
includes:
a supporting structure;
at least one radiating element wound in helical fashion around the
supporting structure with each convolution substantially uniformly
spaced from the adjacent convolution;
circuit means connected periodically to the radiating elements to
increase the electrical path length thereof; and
means to drive at least one radiating element.
2. The device according to claim 1 wherein an even number of
radiating elements are provided with alternate ones of the elements
forming first and second sets of radiating elements, respectively,
and the circuit means periodically couple the first and second sets
of radiating elements.
3. The device according to claim 2 wherein the circuit means
comprise periodic capacitor loading circuits.
4. The device according to claim 2 wherein the circuit means
comprise amplifiers with controlled gain and phase shift.
5. The device according to claim 1 wherein the circuit means
comprises inductive loadings uniformly periodic with respect to
each convolution.
6. A directional electromagnetic radiating device with circular
polarization capable of operating over a wide frequency band which
includes:
a supporting structure;
a first conductor wound in helical fashion around the supporting
structure with each convolution uniformly spaced from the adjacent
convolutions;
a second conductor with a lengthened electrical path wound in
helical fashion around the support structure with each convolution
uniformly spaced from the adjacent convolutions of the first
conductor; and
means to drive at least one of the conductors.
7. The device according to claim 6 wherein each conductor is
multifilar, each conductor has the same number of elements, and the
elements of the first and second conductors alternate along the
supporting structure in uniformly spaced relation.
8. The device according to claim 6 wherein the first conductor also
has an increased electrical path length, each conductor has two
elements, the elements of the first and second conductors alternate
along the supporting structure in uniformly spaced relation, the
first conductor is active and the other conductor is parasitic, and
electrical connection straps connect the parasitic elements in a
closed loop.
Description
Heretofore, it has been well-known to utilize helical antennae to
obtain a circularly polarized radiating element for the purpose of
endfiring, backfiring, or broadside firing, to obtain highly
directional or omnidirectional radiating patterns. It is also
well-known to utilize unifilar or multifilar windings with such
antennae, with such windings acting as the radiators, and being
electrically actuated separately to obtain an enhanced radiation
pattern. However, the primary problem associated with such multiple
radiating elements in a helical antenna has been to obtain a
greater range and more power in a unidirectional radiation pattern.
There have been attempts made to reduce the physical size of such
antennae while still maintaining particular electrical radiation
characteristics and these have met with only limited success. Such
techniques are necessary for the utilization of such antennae on
aircraft or satellites where size and configuration are both very
important to weight and aerodynamic flow considerations.
Therefore, it is the general object of the present invention to
meet the needs of the art by providing a unidirectional or
omnidirectional electromagnetic radiating device, depending upon
how it is fired, which utilizes circular polarization, and is
capable of operating over a wide frequency band that has less
physical size than its radiating electrical characteristics would
indicate.
A further object of the invention is to provide a compact, rigid,
and reliable helical antenna which may be packaged and deployed
because of its physical characteristics, and is physically smaller
than its electrical characteristics because the radiating element
is formed with characteristics to lengthen the electrical path
length thereof.
These and other objects of the invention which will become apparent
as the description proceeds are achieved by providing a directional
electromagnetic radiating device which comprises in combination a
support housing and a radiating element helically wrapped in
uniformly spaced convolutions around said housing whereby the
convolutions are concentrically aligned to a straight axis, which
element is provided with characteristics to lengthen the electrical
path while maintaining a physically reduced size.
For better understanding of the invention reference should be had
to the accompanying drawings wherein:
FIG. 1 is a schematic illustration of a basic embodiment of the
invention with a single radiating element possessing desired
electrical path characteristics;
FIG. 2 is a schematic illustration of the basic embodiment of the
invention with two radiating elements;
FIG. 3 is a schematic illustration of a modification of the winding
of the radiating element that might be utilized with periodic
inductive loading;
FIG. 4 is a schematic illustration of a modified embodiment of the
invention comprising two or bifilar helical windings with periodic
capacitor loading;
FIG. 5 is a schematic illustration of a modified embodiment of the
invention comprising two or multifilar helical windings with active
elements for control of mutual coupling between windings;
FIG. 6 is a schematic illustration of another embodiment of the
invention utilizing two band helical antennae with a conventional
unifilar winding and a slow wave unifilar winding;
FIG. 7 is a schematic illustration of a modified embodiment of the
invention comprising a strapped duobifilar backfire antenna to
achieve improved directional capability; and
FIG. 8 is a schematic block diagram illustration of a modified
embodiment of the invention comprising a multifrequency helical
antenna.
With reference to the form of the invention illustrated in FIG. 1
of the drawings, the numeral 10 illustrates generally a
conventional supporting structure or housing upon which radiating
element or winding 12 is wrapped in a helical pattern to define
uniform spaced convolutions about a central axis 14 defined by the
structure or housing 10. In most preferred instances, the structure
or housing 10 will be of some dielectric material, and preferably
will be cylindrically shaped, and either solid or hollow as the
structural requirements may demand. However, cords in tension over
a supporting framework may provide a suitable lightweight structure
to support the antenna. For some circumstances a conical shape or
other uniform geometric shape might be preferable. In any event,
the structure 10 must not possess any metal or other characteristic
that will interfere with the radiating pattern developed by winding
12 when it is properly loaded with electrical energy, all in the
manner conventionally known in the art.
The features of the winding 12 which form the essence of the
invention reside in the fact such winding 12 is provided with
electrical characteristics to lengthen its electrical path. Because
of the increased path length electrical loading of the winding 12
results in a radiation pattern that would normally be required of a
much larger structure. The electrical path of winding 12 is
lengthened in the preferred embodiment of the invention shown in
FIG. 1 by having the winding 12 being compacted or actually follow
a meandering path as it defines the helical convolutions around the
outer surface of structure 10, and this path is particularly
illustrated at 16 in FIG. 1 of the drawings. Of course, it should
be understood that path 16 of winding 12 is not actually meandering
in its normal meaning since it is necessary that in effect each
meander of the path of winding 12 be periodically repetitious. If
effect, any periodically repeating curving or meandering path, such
as a sine wave or a sawtooth pattern, could be utilized to achieve
the objects of the invention. Specifically, the radiation
characteristics of the winding 12 will depend upon the compaction
or meandering ratio with respect to the pitch ratio of the helical
convolutions. The relationship between the meandering ratio and the
pitch ratio will be related to the firing mode and frequency range
at which the element will be operated. A way to define the
meandering ratio would be in terms of the length of wire it would
take to cover the distance without any compaction or meandering
divided into the length of wire it actually takes to cover the
distance with compaction or meandering. Ratios of between about 1.2
to about 2.5 appear to best satisfy the objects of the
invention.
Specifically, it has been found that an operation in a backfire
mode is favored by a larger pitch angle for the helical
convolutions than operation in an endfire mode, with operation in a
broadside mode falling somewhere in between. Similarly, it has been
found that the wavelength to the diameter of the helical
convolutions is a larger fraction in the backfire mode than the
endfire mode with the broadside mode again falling somewhere in
between. It should be understood, as is well known to anyone
skilled in the art, that the same antenna may operate in backfire,
endfire, or broadside mode depending upon the frequency of the
electrical energization, although operation in any of the modes is
greatly enhanced by utilizing the optimum meandering ratio and
pitch ratio. Thus, it should be understood that the essence of the
invention resides in a loading technique which makes a physically
smaller antenna radiate at an electrical longer wavelength, thereby
enhancing the phase constant of the antenna, and being able to
operate the antenna at two or more frequencies simultaneously by
making the antenna compound multifilar, or compound unifilar as
shown in FIG. 6. The dual frequency operation is due to the
difference in meandering of the two windings.
FIG. 2 illustrates a modified embodiment of the invention utilizing
two helical wrapped radiating elements 18 and 20 formed in equally
spaced convolutions around a supporting structure or housing 22. It
is important to this embodiment of the invention as well as to the
basic embodiment illustrated in FIG. 1 that the convolutions be
equally spaced from each other, and that the electrical path length
of each element be increased by utilizing the compaction or
meandering pattern to the elements themselves in their helically
wrapped convolutions. In this embodiment of the invention, however,
the elements may be fired with different frequencies thereby
creating a much broader band of radiation, or achieving an enhanced
radiation pattern by the combination of the two separate
frequencies operating simultaneously to enhance each other. Thus,
it should be understood that the meandering ratio of elements 18
and 20 may vary depending upon the desired frequency at which
elements will be electrically driven, but that the pitch ratio of
the helical convolutions must remain the same so that the equal
spacing between adjacent convolutions is maintained. Variable pitch
may be used to increase bandwidth where directivity may be
sacrificed.
FIG. 3 illustrates a modified helically wrapped embodiment
differing slightly from the meandering relationship illustrated in
FIGS. 1 and 2, but which will achieve the same purpose of providing
an increased electrical path length to such helical convolutions.
In this embodiment, the helical element 24 is provided with
periodic inductive loading at 26, where the periodic nature is
uniform with respect to each convolution so the same electrical
characteristics are present along the length of the supporting
structure about which such element is wrapped. Any convenient type
of inductive loading might be utilized, or in some cases the
element 24 might be coiled throughout its length to form a reduced
diameter helical winding in and of itself, in addition to the total
element being formed to a helical configuration. For practical
winding purposes the helical winding to achieve the desired
meandering ratio is probably the easiest and least expensive.
FIG. 4 illustrates a further modified embodiment of the invention
which is applicable only to plural helical windings. In this
embodiment, the windings 28 and 30 are connected with periodic
capacitor loading circuits 32, where again the periodic nature is
uniform with respect to each phase helical convolution. This
configuration achieves an increase in electrical path length for
each element 28 and 30.
FIG. 5 again represents a modified embodiment of the invention
applicable to at least two 180.degree. phase spaced helical wound
radiating elements 34 and 36, respectively. In this embodiment,
active circuits, indicated generally by numeral 38 are periodically
coupled by transformers 40 to the elements 34 and 36 again to
increase electrical path length, while at the same time providing a
control of the mutual coupling between the elements 34 and 36. The
active circuits 38 might, for example, comprise an amplifier with
controlled gain and phase shift, which type circuits are well-known
to those skilled in the art. Naturally the periodic nature of the
active circuits 38 is uniform with respect to each convolution to
the helical pattern to which the elements 34 and 36 are wrapped
with respect to a carrying structure or housing.
Thus, it should be understood that the basic purpose of the
invention is to modify the propagation along the path of the
radiating element of the electrical wave by increasing the
electrical path length, and which increase in electrical path
length can, also, in certain circumstances by utilized to control
coupling between the radiating elements. This basic purpose is
extended to multifilar elements which are phase spaced on the
supporting structure. For example, a bifilar combination would have
180.degree. phase spacing, a trifilar 120.degree. , and so on.
FIG. 6 illustrates a modified embodiment of the invention which is
particularly adapted to provide a directional electromagnetic
radiating device capable of operating over several frequency bands.
This embodiment specifically combines a conventional bifilar
helical conductor 42, 42a and a bifilar slow wave helical conductor
44, 44a, each separate conductor wrapped in alternating uniformly
phase spaced helical convolutions about a supporting structure or
housing 46. The conductors are spaced 90.degree. apart. In this
embodiment of the invention, the inclusion of the two slow wave
conductors 44 and 44a extends the capability of the antenna to
lower frequencies and lower frequency bands. This combination can
be used in the backfire mode and in the conventional endfire mode
over a ground plane. As illustrated, the slow wave windings 44 and
44a utilize a helical convolution within themselves but might
utilize the meander or other type loading to lengthen their
electrical path characteristic in the same manner as defined in the
embodiments above. However, the helical conductors 42 and 42a do
not utilize any combination of the invention techniques to lengthen
their electrical paths. Thus this embodiment of the invention
represents a two frequency band helical antenna in combination on a
single structural housing, where the conventional conductor might
be unifilar or multifilar, with the same being applicable to the
slow wave winding, so long as all windings are properly phase
spaced. It should clearly be understood that such combination
greatly enlarges the operating frequency bands of the
combination.
The embodiment of the invention illustrated in FIG. 7 of the
drawings utilizes four separate windings 50 through 56,
respectively, wrapped in equally phase spaced helical convolutions
about a supporting housing 58. However, in this embodiment, the
radiating elements 50 and 54 are active while elements 52 and 56
are parasitic. The parasitic elements have propagation velocities
very near those of the active elements, and therefore appear
electrically to possess backfire wavelengths near the backfire
wavelength of the active pair. The invention contemplates providing
electrical connecting straps 60 at each end of the parasitic
windings which strapping permits the currents to circulate in the
parasitic elements 52 and 56 to provide a coupled system. It should
be noted that this will provide a broadening of the frequency
response by achieving a difference in backfire wavelengths between
the active elements 50 and 54 and the parasitic elements 52 and 56.
Again, each of the elements has provided for increased electrical
path length by utilizing a helical winding or meandering ratio
within each element itself. Thus, this embodiment of the invention
provides a means for radiating a broad electromagnetic spectrum
with a reduced physical size antenna, while still maintaining high
directivity over the radiating band.
FIG. 8 is a block diagram schematic illustration of a
multifrequency helical antenna. Specifically, the antenna comprises
a housing 61 upon which is wound a helical similarly coiled bifilar
windings consisting of conductors 62 and 64, each having equal
space between adjacent coils. The ends of conductor 62 are
identified as 62a, while the ends of conductor 64 are identified by
64a. A transmitter and/or receiver 66 drives through band-pass
filters 68 and 70 to feed or receive from both ends of the antenna
with filter 68 driving into a band-pass filter 74 and filter 70
into band-pass filter 72. The band-pass filters 72 and 74,
respectively, provide the proper resistance value to the windings
62 and 64 at the operating frequency. The filters 72 and 74 are
electrically similar to filters 68 and 70, but are integral to the
housing 61, rather than the receiver 66. The band-pass filter 72
drives with one frequency into ends 62a and 64a adjacent thereto,
and band-pass filter 74 drives with another frequency into ends 62a
and 64a adjacent thereto.
If one assumes that for purposes of explanation channel 1 supplied
by filter 68 operates at a lower frequency than a channel 2
supplied by filter 70, the antenna operates in a backfire mode with
respect to channel 1 and an endfire mode with respect to channel 2.
Thus, operation of channel 1 in the backfire mode requires feeding
that winding on the left end and operation of channel 2 in the
endfire mode requires feeding that winding from the right end.
Thus, both frequencies can be used giving a dual frequency
transmission or reception capability to the antenna. It should be
pointed out that the transmission lines supplying the feed to the
antenna may be conveniently placed within the interior of the
housing 61, even though it is shown on the exterior in FIG. 8 for
sake of clarity.
While in accordance with the patent statutes only the preferred
embodiments of the invention have been illustrated and described in
detail, it is to be particularly understood that the invention is
not limited thereto or thereby, but that the inventive scope is
defined in the appended claims.
* * * * *