U.S. patent number 3,716,861 [Application Number 05/126,448] was granted by the patent office on 1973-02-13 for serpentine antenna mounted on a rotatable capacitive coupler.
Invention is credited to John J. Root.
United States Patent |
3,716,861 |
Root |
February 13, 1973 |
SERPENTINE ANTENNA MOUNTED ON A ROTATABLE CAPACITIVE COUPLER
Abstract
This disclosure teaches an antenna including a conductor
disposed in a serpentine arrangement defined by a plurality of
undulations, wherein the amplitude or size of the undulations
determines the directivity of the antenna, and wherein the
undulations function to cancel mutual inductance parameters of the
antenna while increasing the capacitive reactance thereof, to yield
broadband characteristics. The antenna can take a variety of
shapes, as for example the undulations may all fall entirely in a
common plane and generally define a circle, a square, or an
ellipse, etc.; or, such undulations may be arranged to form a ring
or other three-dimensional object. The said shape of the antenna
and its disposition with the earth's surface also contribute to the
directivity of the antenna.
Inventors: |
Root; John J. (Bronx, NY) |
Family
ID: |
22424872 |
Appl.
No.: |
05/126,448 |
Filed: |
March 22, 1971 |
Current U.S.
Class: |
343/741; 343/882;
343/806 |
Current CPC
Class: |
H01Q
7/00 (20130101) |
Current International
Class: |
H01Q
7/00 (20060101); H01q 009/16 () |
Field of
Search: |
;343/741,744,748,802,806,866,908,882 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lieberman; Eli
Claims
I claim:
1. A broadband transmit/receive antenna comprising:
an antenna element having two ends and having between said two ends
a continuous serpentine configuration defined by a plurality of
serially connected together loop portions each orientated relative
to its immediate adjacent loop portions to effectively cancel out
mutual inductance occurring therebetween during use of the
antenna;
support means for rotatably supporting said antenna element;
a pair of terminals connected to said support means and connectable
to devices for transmitting and receiving electromagnetic energy
during use of the antenna;
and means at least partially disposed interiorly of said support
means for capacitively connecting each end of said antenna element
to respective ones of said terminals.
2. A broadband transmit/receive antenna as set forth in claim 1, in
which said plurality of loop portions comprise means defining a
direct relationship between the capacitive reactance of said
antenna element and the number of said loop portions.
3. A broadband transmit/receive antenna as set forth in claim 1, in
which all said loop portions lie in a common plane.
4. A broadband transmit/receive antenna as set forth in claim 3, in
which said plurality of loop portions comprise means defining an
antenna directivity extending normal to said common plane when said
loop portions are of equal size and are equal to one wavelength of
the lowest frequency to be applied to said antenna, and said
directivity is in said common plane when said loop-portions are of
equal size and are equal to one-half wavelength of said lowest
frequency.
5. A broadband transmit/receive antenna as set forth in claim 1, in
which each said loop portion has a peak portion and a valley
portion, and wherein each said peak portion lies in a first plane
and each said valley portion lies in a second plane extending
parallel to said first plane.
6. A broadband transmit/receive antenna as set forth in claim 5, in
which said plurality of loop portions comprise means defining an
antenna directivity extending normal to said first and second
planes when said loop portions are of equal size and are equal to
one wavelength of the lowest frequency to be applied to said
antenna, and said directivity is in a plane parallel to said first
and second planes when said loop portions are of equal size and
equal to one-half wavelength of said lowest frequency.
7. A broadband transmit/receive antenna as set forth in claim 5, in
which said plurality of loop portions form a hollow truncated cone
having major and minor diameters, wherein said first plane is
disposed at the minor diameter of said truncated cone and said
second plane is disposed at the major diameter of said truncated
cone, and wherein said plurality of loop portions comprise means
defining an antenna directivity which is in a direction projecting
outward from said first plane.
8. A broadband transmit/receive antenna as set forth in Claim 1,
wherein said support means comprises a base member, an insulative
sleeve, first and second conductive sleeve portions fixed on said
insulative sleeve in axially spaced-apart relationship, means
rotationally interconnecting said insulative sleeve with said base
member, conductive means for electrically interconnecting one end
of said antenna element to said first conductive sleeve portion and
the other end of said element to said second conductive sleeve
portion, first and second conductive terminals fixedly
interconnected with said base member, an insulative tubular member
fixed to said base member and disposed coaxially within said
insulative sleeve, first and second conductive tubular members
mounted in axially spaced-apart relationship on said insulative
tubular member and extending coaxially and in opposed facing
relationship with said first and second sleeve portions,
respectively, and means connecting said first and second conductive
terminals to said first and second tubular members,
respectively.
9. A broadband transmit/receive antenna as set forth in Claim 1;
wherein said support means comprises
a base member having connected thereto said pair of terminals,
an electrically insulated tube connected to and extending outwardly
from said base member and having around the exterior thereof a pair
of peripherally extending and axially spaced-apart electrically
conductive portions,
a support plate having means therein defining an opening through
which said tube extends,
means mounting said support plate for rotational movement around
said tube,
a hollow member coaxially disposed around and spaced from said tube
and connected to said support plate to undergo rotational movement
therewith around said tube and having a pair of electrically
conductive portions peripherally extending thereover and axially
spaced-apart therealong each in opposing spaced-apart relationship
from respective ones of said electrically conductive portions of
said tube,
and means electrically connecting said two ends of said antenna
element to respective ones of said electrically conductive portions
of said hollow member and electrically connecting said pair of
terminals to respective ones of said electrically conductive
portions of said tube,
whereby said antenna element may be angularly displaced to vary the
antenna directivity.
10. A broadband transmit/receive antenna as set forth in claim
9;
wherein said electrically conductive portions of said tube and
hollow member comprise annular sleeves connected to said tube and
hollow member.
Description
BACKGROUND OF THE INVENTION
A conventional method of fabricating a broadband antenna is to
couple together a plurality of highly-selective antennae. For
example, a conventional television receiving antenna comprises a
plurality of dipoles coupled together on a boom for connection to
the television receiver. However, dipole antennae which are
disposed adjacent each other are subject to an interaction which
changes their individual characteristics in ways which are almost
impossible to predict. Accordingly, it is usually necessary to
experiment with antennae configurations in an effort to arrive at
proper relationships between length and spacing of elements. A
further problem of such conventional antennae is that they are
highly directional and must be pointed towards the transmission
source for good reception.
A principal object of this invention is to provide a broadband
antenna which alleviates the coupling problems of conventional
antennae, and which lends itself to a plurality of similar
configurations providing widely varying directivity qualities.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a broadband
transmit/receive antenna including a conductor arranged in a
serpentine configuration to provide a plurality of loop portions or
undulations. The changing direction of the antenna element cancels
mutual inductance between the undulations, and the capacitive
reactance of the antenna is increased by increasing the number of
undulations thereof. Thus, such an increase in the number of
undulations causes an unbalanced reactance characteristic and a
resultant increase in radiation resistance of the antenna system,
thereby providing the antenna with a broadband frequency
response.
The directivity of the antenna is controlled by the relative
disposition of the individual undulations in the serpentine
arrangement. For example, if the undulations are arranged in a
common plane, then the directivity can be controlled by the
positioning of the plane defined by the antenna. In this respect,
the undulations can be arranged to form a circle, a diamond shape,
a square or any other geometric configuration. Then, in another
embodiment, the undulations can be formed in a band, or in the form
of a truncated cone, to control the directivity of the antenna.
The directivity is also effected by the size or amplitude of each
undulation in the serpentine arrangement. For example, if the
undulations lie in a common plane, and if such amplitude defines
one wavelength at the lowest desired frequency of the broadband
antenna, then the directivity of the antenna is normal to the
common plane in which the undulations lie. Alternatively, if the
amplitude is arranged at one-half wavelength of the lowest
frequency, then the directivity of the antenna is to the edges of
the plane in which the element lies.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawing illustrates various modifications of a
preferred embodiment of the invention. In such drawing:
FIG. 1 is an elevational view of a broadband antenna according to
the invention;
FIG. 2 is an enlarged view of a support portion of the antenna of
FIG. 1, with sections broken away for clarity;
FIG. 3 is a sectional view taken along the line 3--3 of FIG. 2;
and
FIGS. 4-7 are views similar to FIG. 1, but showing antennae having
different profiles than that illustrated in FIG. 1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
As illustrated in the drawings, all of the modifications of the
invention include an antenna element defining a serpentine
arrangement of individual undulations. The undulations in each
modification have the same size, and as described below, the
relative disposition and size of the undulations determines the
directivity of the antenna, while the number of undulations
determines its broadband response.
In a rotational antenna assembly 2 according to the invention, as
illustrated in FIGS. 1-3, an antenna element portion 4 is formed by
a continuous serpentine arrangement of antenna tubing 6, and is
mounted on a pedestal assembly 10. The serpentine arrangement of
the tubing 6 is formed by outer and inner bends 6a and 6b which
define peaks and valleys of the loop portions or undulations, and
which follow a generally circular path. A sleeve hollow member
composed of portions 20, 22, 24 is held in an upright position with
a straight portion 6e of the tubing by spaced upper and lower discs
8 and 12. One end 6c of the tubing is mounted on the upper end of
the sleeve portion adjacent a bent portion 6d of the tubing and the
portion 6d defines the transition between the straight portion 6e
and the serpentine portion of the tubing 6. The lower disc 12 is
fixed to a rotatable support plate 14, which in turn, rotatably
rests by means of a conventional ball bearing 14b on an electrical
connector block 16 fixed to a base member 18.
As shown, the element 4 and sleeve portions 20, 22 and 24 are fixed
together and to plate 14 for rotation with respect to the base
member and connector block 18 and 16, which in turn are fixed
together as by a screw 18a. That is, the end 6c of the tubing 6
passes into a recess 8a in the disc 8, wherein it is electrically
connected by a member 22a to the upper end of conductive sleeve
portion 22. The conductive sleeve portion 22 is received over an
upper section of the sleeve portion 20, while the conductive sleeve
portion 24 is received over a lower section of sleeve 20, said
sleeve 20 comprising an insulative tube fixed at its lower end to
the insulative rotational plate 14. On the other hand, the straight
portion 6e of the tubing passes through an opening 8b in the
insulative disc 8, and is fixed at its lowermost end within an
opening 12a in the lower disc 12, which in turn is fixed to the
plate 14 as by a screw 14a. Thus, the tubing end 6c and the
straight portion 6e of the tubing are both fixedly interconnected
with the plate 14 for rotation therewith.
A length of twin-lead cable 34 is provided and has one conductor
connected directly to the metal conductor block 16 as at 16c, and
its other conductor mounted insulatively on the block 16 as at 16a
and 16b. An insulative tube 26 extends upwardly from the base
member 18 and has conductive sleeves 28 and 30 coaxially disposed
thereon at its upper and lower portions, respectively. The lower
sleeve 30 is fixed to the connector block 16, thereby providing an
electrical connection between one of the twin lead conductors and
the sleeve 30 and the sleeve 30 extend 5 upwardly and coaxially
with the conductive sleeve 24. Thus, the straight tubing portion 6e
is electrically coupled, directly, to the disc 12, which in turn is
electrically coupled, directly, to the sleeve portion 24, which in
turn is electrically coupled, indirectly, to the conductive sleeve
30 by the coaxial disposition therebetween.
An insulated conductor lead 32 is connected to the insulated
mounting point 16a, 16b between the block 16 and the other
conductor of the twin-lead cable 34, and the lead 32 passes upward
through the insulative tube 26 for electrical connection to the
upper conductive tube 28 as at 28a. Thus, the tube 28 and sleeve
portion 22 provide an indirect electrical coupling along their
coaxial extent to complete the antenna circuit.
Accordingly, the antenna assembly 2 provides a rotational antenna
element 4 to facilitate adjustments in the directivity of the
antenna.
The serpentine configuration functions to cancel the mutual
inductance of the element 4 with the result that the capacitive
reactance of the element has an increasing relationship with
respect to an increase in the number of undulations. That is, a
reactance imbalance occurs due to the decrease in inductance.
In the antenna illustrated in FIG. 1, all of the undulations of the
tubing 6 are disposed in a common vertical plane, and are arranged
in a circle, with the connecting leads of cable 34 being for
coupling the antenna to a transmitting and/or receiving device.
Both the antenna element of FIG. 1 and that of FIG. 4 provide for
horizontal polarization of the antenna pattern, and as illustrated,
the device of FIG. 4 differs from FIG. 1 only in the arrangement of
undulations. That is, in FIG. 4, the antenna element forms an
elongated oval shape 36 which provides the same broadband qualities
and general directivity of the device of FIG. 1.
The various embodiments disclosed herein have been tested and have
been found to provide, for example, a frequency response from 50
MHz to 890 MHz, whereby 50 MHz becomes the lowest frequency to be
operatively applied to the antenna. Also, conventional coupling to
the transmitter or receiver device is possible, as by stacking
coupling or, as described above, by transmission lines to rotary
devices.
In the antenna of FIG. 5, the undulations are arranged to form a
band 38, wherein such undulations are defined axially of the band
and advance circumferentially thereof. Again, in the modification
of FIG. 5, the antenna pattern is polarized horizontally and has
characteristics which are much the same as the antennae of FIGS. 1
and 4. In these three embodiments it has been found that the size
or amplitude of each undulation, as indicated at reference numeral
40 in FIGS. 4 and 5 which designates the distance between peak and
valley portions of the undulations in each of those views, has an
effect on the directivity of the device, according to the following
relationship: if the amplitude 40 is equal to one wavelength of the
lowest frequency to be transmitted or received, then the antenna
will have a pattern extending in opposing directions normal to a
vertical plane through each undulation; and, if the undulation
amplitudes define one-half wavelength of the lowest frequency, the
directivity of the device changes so that it projects from the
edges of the antenna.
FIGS. 6a and 6b show modifications of the antennae of FIGS. 1 and
5, respectively, wherein such antennae are identical except for the
disposition of their principal planes; and, as shown, FIGS. 6a and
6b illustrate antennae, formed as bands 42 and 44 respectively,
which are disposed horizontally as compared to the vertically
disposed antennae of FIGS. 1 and 5.
Another modification as illustrated in FIG. 7, defines an antenna
element which takes the shape of a truncated cone 46, wherein the
undulations of the serpentine arrangement are disposed along the
side walls of the cone. The directivity of the antenna of FIG. 7 is
along the axis of the cone, and in the direction of the vertex
thereof. Again, the broadband qualities of the device increase with
an increase in the number of undulations.
* * * * *