U.S. patent number 3,618,105 [Application Number 05/017,239] was granted by the patent office on 1971-11-02 for orthogonal dipole antennas.
This patent grant is currently assigned to Collins Radio Company. Invention is credited to Ross L. Bell, Warren B. Bruene.
United States Patent |
3,618,105 |
Bruene , et al. |
November 2, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
ORTHOGONAL DIPOLE ANTENNAS
Abstract
A drooping dipole antenna having a center combination supporting
mast and indicator balun structure with the drooping dipoles
electrically close to the ground and part of the guy support system
for the antenna effective primarily in the skywave mode of
operation, but also producing a useful vertically polarized surface
wave component with the droop of the dipole elements. Further, with
two of these antennas colocated in an orthongonal configuration and
the two antennas substantially at right angles sufficient mutual
isolation is advantageously attained that the two input terminals
are connectable simultaneously to two transmitters, two receivers,
or one transmitter and one receiver.
Inventors: |
Bruene; Warren B. (Dallas,
TX), Bell; Ross L. (Dallas, TX) |
Assignee: |
Collins Radio Company (Cedar
Rapids, IA)
|
Family
ID: |
21781510 |
Appl.
No.: |
05/017,239 |
Filed: |
March 6, 1970 |
Current U.S.
Class: |
343/747; 343/861;
343/797; 343/821; 343/884 |
Current CPC
Class: |
H01Q
21/28 (20130101); H01Q 9/44 (20130101) |
Current International
Class: |
H01Q
21/00 (20060101); H01Q 21/28 (20060101); H01Q
9/04 (20060101); H01Q 9/44 (20060101); H03H
2/00 (20060101); H01q 021/26 () |
Field of
Search: |
;343/725,747,752,797,809,821,862,884,861 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Microwave Journal, Oct. 1964, p. 17, copy 343-809 .
Parten, CQ, Dec. 1966, p. 69 & 70 Copy 343-886.
|
Primary Examiner: Lieberman; Eli
Claims
We claim:
1. An antenna with opposite radiation elements extended from a
center feed section, wherein: said opposite radiation elements have
longitudinally extended effective line centers of signal
propagation effectiveness common to the same vertical plane and of
substantially equal length; a combination mast and balun structure
with two vertically extended parallel structural electrically
conductive members mounted on a supporting conductive plate and
with vertically elongate electronically active centers common to
said vertical plane; first variable capacitive means connected
between said two vertical conductive structural mast-balun members;
RF signal conductive line means connectable to RF signal
translating means and extended up a portion of one of said two
vertical mast-balun members and signal coupled across to positive
signal feed conductive contact with the other of said two vertical
mast-balun members; feed connective means for each of said opposite
radiation elements with said mast-balun structure adjacent the top
of each respective vertical mast-balun member; and with two of said
antennas colocated in an orthogonal antenna structure wherein the
vertical plane of one antenna is substantially at right angles to
the vertical plane of the other antenna for optimized mutual
isolation between the two colocated antennas of the orthogonal
antenna structure; and wherein said RF signal conductive line means
for each of the colocated antennas is extended to the top of a
first one of the two vertical mast-balun members; and a second
tunable capacitor is provided in a crossover signal feed connective
means from the top of said RF signal conductive line means to said
positive feed conductive contact to the second vertical mast-balun
member of that antenna.
2. The orthogonal antenna structure of claim 1, with said first and
second tunable capacitors of each of the colocated right-angle
antennas are included in an antenna coupler structure mounted at
the top of the combination mast and balun structure of the
respective antenna.
3. The orthogonal antenna structure of claim 2 wherein the
combination mast and balun structure of one colocated antenna is
sufficiently longer than the mast and balun structure of the other
colocated antenna that the center bottom of the antenna coupler
structure of one antenna overlies the center top of the antenna
coupler structure of the other antenna.
4. An antenna with opposite radiation elements extended from a
center feed section, wherein: said opposite radiation elements have
longitudinally extended effective line centers of signal
propagation effectiveness common to the same vertical plane and of
substantially equal length; a combination mast and balun structure
with two vertically extended parallel structural electrically
conductive members mounted on a supporting conductive plate and
with vertically elongate electronically active centers common to
said vertical plane; first variable capacitive means connected
between said two vertical conductive structural mast-balun members;
RF signal conductive line means connectable to RF signal
translating means and extended up a portion of one of said two
vertical mast-balun members and signal coupled across to positive
signal feed conductive contact with the other of said two vertical
mast-balun members; feed connective means for each of said opposite
radiation elements with said mast-balun structure adjacent the top
of each respective vertical mast-balun member, wherein each of said
two vertical mast-balun members are tubes of conductive material
projecting upwardly in parallel effective inductive spaced
relation; nonconductive dielectric structural means interconnecting
said tubes in maintenance of the spaced relation of the tubes in a
shorted transmission line balun structure; wherein said first
variable capacitive means is connected between the tops of the
tubes comprising said two vertical mast-balun members; said RF
signal conductive line means is extended upward within a first tube
of said mast-balun tubes; signal coupling means from said RF signal
line across to positive signal conductive connection with the
second tube of said mast-balun tubes as an RF signal feed point for
the shorted transmission line balun structure at that location.
5. The antenna of claim 4, wherein said crossover feed point
connection is to the top of said second tube.
6. The antenna of claim 5, wherein a second tunable capacitor is
included in said signal coupling means from the RF signal line
across to said second tube.
7. The antenna of claim 4, wherein said RF signal crossover feed
point connection is to an intermediate point between the top and
bottom of said second tube.
8. The antenna of claim 7, with a plurality of said crossover feed
point connections on said second tube connected to a plurality of
vertically spaced signal coupling means from said RF signal line,
and with said crossover feed point connections spaced along said
second tube between the bottom and top thereof; and with switch
means included in said plurality of signal coupling means from said
RF signal line for selectively switching the balun structure
between the feed point locations as desired.
9. The antenna of claim 8, with at least one switchable shorting
means connected between the two tubes of said combination antenna
mast and balun structure intermediate the bottom and top
thereof.
10. The antenna of claim 4, with a plurality of switchable shorting
means connected between the two tubes of said combination antenna
mast and balun structure at various locations intermediate the
bottom and top thereof.
11. The antenna of claim 10, wherein control means is provided for
said plurality of switchable shorting means; and said control means
includes control wire connections to switch throw means with the
control wires extending up said combination antenna mast and balun
structure.
12. The antenna of claim 4, wherein a tunable antenna coupler is
mounted at the top of the combination antenna mast and balun
structure; antenna coupler control means is provided with tunable
capacitor setting means included in the coupler; and with control
system lines extended through said combination mast and balun
structure from an external control source to the tunable antenna
coupler.
13. The antenna of claim 12, wherein a paralleled coil and
capacitor signal coupling circuit is provided in a connection
between each radiating element and the associated tube top of the
combination mast and balun two tube structure.
14. The antenna of claim 13, wherein shorting switch means is
provided across each of said paralleled coil and capacitor signal
coupling circuits for selectively switching the paralleled coil and
capacitor signal coupling circuits into and out of signal coupling
use between the radiating elements and the respective combination
mast and balun tube tops.
15. The antenna of claim 4, with the signal coupling means from
said RF signal line across to positive signal conductive connective
with the second tube of said mast-balun tube structure at a
location intermediate the top and bottom thereof; and RF signal
lines extended from a connection with respective radiating elements
down through substantially are equidistant upper portion of
respective tubes of the mast-tube balun structure to a cross
conductive line connection therebetween through tube wall openings
provided therefor.
Description
This invention relates in general to antenna systems, and in
particular, to dipole antennas having a center combination
supporting mast and inductor balun structure for primarily a
skywave mode of operation, but also producing a useful vertically
polarized surface wave component, and in a two dipole orthogonal
configuration two electrically isolated dipole antennas operational
independently with the two input terminals connectable
simultaneously to two transmitters, two receivers, or one
transmitter and one receiver.
Many preexisting short-range HF communications systems have relied
on surface wave propagation in the accomplishment of the
communications mission generally through the use of vertically
polarized whip antennas. A portion of the signal radiated from a
vertical whip is propagated along the surface of the earth and is
received by a similar antenna some distance away with the distance
the signal can be received dependent on such factors as path
attenuation, transmitter power, receiver sensitivity, antenna
efficiency, terrain masking, and noise. Some of these factors are
related only to equipment including transmitter power, receiver
sensitivity, and antenna efficiency, while others relating only to
operating environment include path attenuation, terrain masking,
and noise. With reference to path attenuation, if the ground were a
perfect conductor, the field strength of the transmitted signal
would vary inversely with distance from the transmitting antenna,
but since the earth is not a perfect conductor the signal is
subject to additional attenuation. Attenuation is increased as the
conductivity of the ground decreases and as the operating frequency
is increased. Further, many areas of the earth are covered with
foliage, another factor materially increasing signal attenuation
with, in some areas, surface wave communication over even as little
as one or two miles being difficult in dense jungle. Military
personnel in South East Asia have even found it impossible at times
in some areas to talk over distances as short as several hundred
feet with vehicular and man-pack radios. Furthermore, groundwave
signals deteriorate from predicted values when obstructions are
located between the transmitting and receiving antennas with the
presence of an obstruction causing some signal reflection and some
signal diffraction over the obstruction. The relative magnitude of
these effects depends on the height of the obstruction and the
steepness of the sides of the obstruction. Thus, surface wave
signal propagation in hilly and mountainous areas produces field
strength variations resulting from both interference patterns and
from shadowing.
Noise originating from a number of sources is received on HF
antennas, along with the desired signal, deteriorates the
intelligence of the signal. These harmful noise sources include
local man made noise, atmospheric noise originating from distant
locations, and local thunderstorm activity. Man made noise is
noteworthy in that it is predominately vertically polarized, and
therefore, more efficiently received on vertically polarized
antennas. This is a serious problem in deterioration of groundwave
signal reception particularly in areas of activity involving use of
machinery. Atmospheric noise, however, is derived from a number of
sources including sunspot activity, transmissions from unwanted HF
transmitting sources, and from remotely located thunderstorm areas.
It is significant that noise from distant sources is usually much
more pronounced at low elevation angles since propagation at higher
angles requires more hops and consequently is subject to more path
attenuation. Thus, it follows that since groundwave propagation
requires radiation on or about the horizon and at low elevation
angles, the amount of atmospheric noise received is greater than
that received with higher angle radiation patterns. With respect to
thunderstorm activities, it is interesting to note that they are
more predominately located in the equatorial regions and that,
therefore, the noise factor generated in this manner extending into
the HF band is, generally, of greater significance as the location
of operation is moved toward the equatorial regions.
It is, therefore, a principal object of this invention to provide
an antenna system having a primary mode of communications
substantially independent of local ground characteristics and
terrain, and assurance that wherever in the world the antenna
system were deployed the communication range would remain
essentially constant.
Another object is to provide an antenna system with two
electrically mutually substantially isolated dipole antennas
supported above a ground plane operating as two independent
antennas.
A further object with such an antenna system is to achieve a
skywave mode of operation that is essentially omnidirectional for
both colocated antennas of an orthogonal antenna particularly with
the high-angle skywave signal propagation.
Still a further object is to provide an antenna system that, while
having radiation patterns beamed primarily upward toward the
ionosphere, the antenna dipoles produce a useful vertically
polarized surface wave component.
Another object is to provide such an antenna system with two sets
of dipole elements disposed in orthogonal relation with
substantially complete omnidirectional surface wave coverage
allowing for communication with whip equipped man-pack and vehicle
radios.
A further object is to provide a feed to balanced antennas with
adjustable couplers that does not require changing of antenna
element lengths or heights of elements above ground.
Still a further object is to provide an orthogonal antenna
configuration of two independent colocated antennas that can be fed
separately but when used in the receive mode for signals eminating
from a transmitting antenna system over short range skywave paths
that the two received signals be uncorrelated to a high degree, and
when the operating frequency is near the optimum skywave frequency
the two received signals have essentially a negative one
correlation coefficient. Please note in this regard that
uncorrelated signals are necessary for providing good diversity
signal system operational results with, of course a negative one
correlation ideal for diversity systems in that while one signal is
fading the other signal is at a maximum.
Features of the invention useful in accomplishing the above objects
include a drooping dipole having a center combination two vertical
tube mast and balun structure with opposite antenna wire elements
part of a guy support system for the antenna. The effective
longitudinal center of the radiating antenna elements of each
individual antenna and the combination mast and balun tubes are
substantially coplanar in a vertical plane. Further, the drooping
dipoles are electrically close to the ground and configured
primarily for an effective relatively short range HF skywave mode
of operation although, a useful vertical polarized component is
developed with the drooping dipole radiating elements. Two of these
independent antennas are also quite effectively colocated in an
orthogonal configuration with the vertical plane of one
substantially at an optimized mutually isolated right-angle
orientation to the vertical plane of the other. Each antenna both
individually and in a two antenna orthogonal configuration utilize
a top mounted centerally located antenna tuning coupler with
antenna feed generally to the balun top.
Specific embodiments representing what are presently regarded as
the the best modes of carrying out the invention are illustrated in
the accompanying drawings.
In the drawings:
FIG. 1 represents a combination installation and schematic showing
of a drooping dipole electrically close to the ground antenna with
a center two tube supporting mast and balun structure topped by an
antenna coupler and with opposite antenna wires tied to ground
stakes with tag lines;
FIG. 2, two colocated antennas such as the antenna of FIG. 1
disposed at, substantially, right angles to each other with the
center mast structures extended upward from a common electrically
conductive ground plane support plate, and with the drooping dipole
antenna wires also serving as buy wires for the antenna
structure;
FIG. 3, a perspective view of the orthogonal antenna structure of
FIG. 2, showing more detail;
FIG. 4, another drooping dipole antenna structure having many
features in common with the antenna of FIG. 1, but with more
frequency-tuning features provided;
FIG. 5, an orthogonal drooping dipole antenna structure with each
of the colocated antennas thereof much the same as the antenna of
FIG. 4 with a plurality of frequency-bandswitching switches in each
antenna balun and additional tuning control detail;
FIG. 6, a partial schematic detail showing with RF and control
leads extended up one tube of an antenna combination mast and balun
structure such as employed with the antenna of FIG. 5;
FIG. 7, a partial schematic showing of antenna circuitry much the
same as that of FIGS. 5 and 6 with a step tune inductive capacitive
circuit switchable into and out of interconnect between each balun
connection with a respective antenna wire element as the wire
element goes through series resonance as the antenna is tuned
higher in each balun switched frequency-tuning band;
FIG. 8, a partial schematic showing in more detail of an antenna
embodiment such as shown in FIG. 7 with RF and discriminator wires
housed in one leg and power for torque motors and tower balun
shorting switches housed in the second balun leg;
FIG. 9, skywave mode signal waveforms sensed by the two respective
right angle orthogonally oriented antennas in the receive mode
illustrating the advantageous negative one correlation coefficient
relation therebetween ideally suited for diversity reception;
FIG. 10, an alternate drooping dipole antenna configuration with
other frequency tuning features from the embodiments of FIGS.
1,4,6, and 7;
FIG. 11, still another drooping dipole antenna structure with
frequency selectivity provided via different tuning structural
features;
FIG. 12, a balanced drooping dipole orthogonal antenna structure
with arrowhead radiating elements;
FIG. 13, a balanced drooping dipole orthogonal antenna structure
with triple wire radiating elements; and
FIG. 14, a balanced drooping dipole orthogonal antenna structure
with two radiating elements of different lengths coextended from
the same feed connection.
Referring to the drawings:
The drooping dipole structure 20 of FIG. 1 is shown to include a
set of electrically conductive tubes 21 and 22 mounted in
relatively closely spaced parallel relation to extend vertically
upward from a conductive ground plane plate 23 that shorts the
tubes 21 and 22 together at the bottom substantially at the ground
plane. The tubes 21 and 22 are physically interconnected at the top
by a top mounted antenna coupler structure 24 that includes a
tuning capacitor 25 connected between the tops of the combination
mast and balun tubes 21 and 22 and also an interconnect lead 26
extended from a feed coax center line 27 from the top thereof
within tube 21 to the top of tube 22. While center conductor 27 of
coax signal feed line 28 is shown to be extended upward alone
through the tube 21 to the upper end thereof the coax line 28
itself could be extended to the top of tube 21. Electrically
conductive radiating element antenna wires 29 and 30 extend outward
and downward at substantially 180 degrees orientation one from the
other in the planar sense and as combination guy and drooping
dipole antenna radiating elements extend from connection to the
tops, respectively, of tubes 21 and 22 to insulating elements 31
tied to guy wire or rope tag lines 32 that are anchored at their
outer ends by ground stakes or anchors 33. Coax signal feed line 28
is connected to a transmitter or a receiver (neither shown) for
transmit or receive as desired.
This is a drooping dipole antenna configuration with a center
combination supporting mast and inductor balun structure
particularly useful for relatively short range HF communication to
the range of 100 to 300 miles via the skywave high-angle skip mode
of operation. Further, with the sloped combination guy and dipole
antenna element wires a vertically polarized surface wave component
is developed useful for communication with equipped man-pack and
vehicle radios.
There is a need to be able to operate two transmitters, two
receivers, or one transmitter and one receiver simultaneously from
substantially one location with sufficient mutual isolation
provided that cross modulation between transmitters or from
transmitter to colocated receiver antenna is acceptable low. In
order to attain such capability isolation wise selectivity in
transmitter output filter and antenna system mutual isolation a two
antenna orthogonal drooping dipole antenna structure 34 such as
shown in FIG. 2 is provided. With this orthogonal antenna
configuration two colocated antennas, with each such as the antenna
of FIG. 1, are disposed in plan view at substantially right angles
to each other. Components of this orthogonal two antenna structure
duplicating those of the single drooping dipole antenna 20 of FIG.
1 are given the same numbers or primed numbers as a matter of
convenience. Referring also to FIG. 3 the orthogonal drooping
dipole antenna structure 34 is shown with additional detail from
FIG. 2 with the combination mast and balun tubes 21 and 22 of one
antenna structure longer than those of the other in order that one
top mounted antenna coupler structure 24' may overlie the other at
right angles thereto. Please note further, that the combination
mast and balun tubes of one antenna must be substantially common to
the vertical plane of that antenna and that the two antennas along
with the baluns thereof be oriented with their respective vertical
planes substantially at right angles to each other since mutual
signal coupling therebetween is proportional to the cosine of the
angle formed when there is a departure from the optimized right
angle relation therebetween.
These antenna systems are excellent tactical systems particularly
suitable for short range communications in the 0- to 300-mile
communications range via their primary skywave mode of operation.
They are capable of operation anywhere in the world and are
actually not excluded from operating in those parts of the world
where environmental conditions prohibit the use of surface wave
communications since the primary skywave mode of operation provides
essentially the same communications range whether in dense jungle,
mountainous regions, desert, or other poor earth regions, with this
mode of operation, advantageously, independent of ground
characteristics. Skywave mode communications in the range of 0 to
300 miles generally use ionosphere F.sub.2 layer propagation since
it is the most stable and predictable with a system requirement via
such usage of frequency capabilities ranging from approximately 2.9
to 12 MHz. based on factors of minimum and maximum FOT's (frequency
of optimum traffic). As observed through a period of years, these
limits have proven accurate to at least a 90 percent realiability
factor. This is with appropriate scales based on ray-path geometry
using the F.sub.2 layer limits of 240 and 450 km. and Ionosonde
date over a period of years substantiating such limits. Such 0- to
300-mile range operation requires that the antenna provides
elevation plane coverage of 44 percent to 90 percent above the
horizon and it is shown that these new antenna configurations in
their electronically close to the ground configuration provide such
44.degree. to 90.degree..degree.elevation plane coverage between
the frequencies of 2.9 to 12 MHz. Actually operation below 2.9 MHz.
is quite often possible with the presence of the D, E, and F.sub.1
layers of ionosphere, and occasionally, such skywave operation
above 12 MHZ. is possible, so, the tunable frequency band
operational capabilities extending from approximately 2 to
approximately 15 MHz., such as readily attained with some of
applicants' new antennas, is highly desired.
Referring now to the drooping dipole antenna 35 embodiment of FIG.
4 components duplicating those of FIGS. 1 and 2 are given the same
identification numbers, primed numbers where they are similar, and
new numbers for entirely different components. In this embodiment
in place of the interconnecting lead 26 of the FIG. 1 and FIG. 2
embodiments an adjustable loading capacitor 36 is provided with one
side lead connected to the end of coax lead 27 at the top end of
combination mast and balun tube 21 and the other capacitor 36 leads
is connected to the top of combination balun mast and tube 22.
Furthermore, a shorting frequency bandswitching switch 37 is
connected between the combination mast and balun tubes 21 and 22
spaced upwardly at a distance above the ground plane and shorting
plate 23 such as to alter the frequency-tuning band range of the
combination mast and balun and antenna structure to a higher
frequency range when the switch 37 is closed to provide a
conductive shorting path between the balun tubes 21 and 22 at that
point. With these embodiments the individual antennas are fed in a
balanced manner by virtue of, in effect, a 1:1 two-wire balun
placed across the antenna terminals. Physically, in actuality the
balun consists of two sets of tubing connected to the antenna wires
at the top of the mast and with these sets of tubing being the
vertical structural members of the mast. The two lengths of tubing
in each antenna tubing set are shorted together at the lower end by
the ground plate 23 or at an intermediate point by a shorting
switch such as the band switching switch 37 of the FIG. 4
embodiment with the shorted together tubes being a shorted
transmission line across the antenna feed point. Please note that
at these feed points with respect to the respective antennas these
shorted transmission lines appear as inductive susceptances
balanced with respect to ground.
Referring now to FIG. 5, the two colocated orthogonal antenna
structure 38 is shown to have, in place of one bandswitching switch
37 in FIG. 4, three balun inductor switches 37a, 37b, and 37c that
are actually enclosed within dielectric tubes. The bandswitching
switches 37a, b, and c, provide for progressively bandswitching
from lower to higher frequency bands with the respective two mast
tube and balun lines 21' and 22'. Please note the control line 39
extension from an antenna control signal box 40 that extends up
tube 21' with the RF coax line 28 for each balun and mast two tube
set. Further, the coupler antenna control source is provided with a
primary power input line 41 and with a control line 42 to control
signal box. Circularly formed spacers 43 of dielectric material
such as fiberglass are used as tube spacers in the antenna
mast-balun structure.
Referring also to the schematic detail FIG. 6 showing for one of
the two coplanar antennas of the FIG. 5, orthogonal antenna
structure 38. A group of control wires in control line 39 extends
to the antenna coupler upward through tube 21' to the antenna
coupler 24" and within the coupler structure 24' it includes wiring
to discriminator circuit 44 and in cooperation with the wiring to
the discriminator 44 wire from an interconnect system to tuning
drive motor 45 for the tuning capacitor 25' and also to loading
drive motor 46 for adjustment of loading capacitor 36'. Other
control wires of line 39 are extended to switch actuating solenoids
47a, 47b, 47c for bandswitching control of balun shorting switches
37a, 37b, and 37c.
This particular orthogonal dipole antenna system has two isolated
colocated drooping dipole antennas supported by a combination mast
and balun structure with one balun for each of the two antennas
incorporated in the antenna structure. Basically the mast consists
of four vertical tubular sections each made up of four aluminum
tubes arranged in substantially a square configuration and
maintained in position by glass-reinforced plastic spacers located
at various vertically spaced locations therealong. Four radiating
elements also serve as guys for the mast and balun structure and
are so choosen as to have high mechanical strength as well as good
electrical conductivity. These radiating elements are physically
attached adjacent the tops of respective tubes in the combination
mast and balun structure, and may be, for example, radiation
elements of one quarter inch phosphor bronze cable 45 feet long.
These in turn are connected individually each to an electrical
insulator that in turn is connected via rope or additional cable to
a ground anchor. The tow antenna couplers 24", one for each
antenna, are identical in construction with a discriminator circuit
unit 44 contained therein, and motors 45 and 46 for driving the
tuning capacitor 25' and the loading capacitor 36' therein. Please
note, that heavy plastic tie plates are provided on the tops and
bottoms of the two couplers 24" thereby providing sufficient
structural rigidity that no strain is placed on the capacitors 25'
and 36'. Further, each coupler 24" is enclosed in a high-impact
dielectric plastic material cover, and the bottom tie plate of each
coupler 24" is provided with mechanical fasteners of a conventional
nature (detail not shown) for securing the couplers 24" to the tops
of the respective antenna mast tubes. Please note again, that the
two input terminals may be connected simultaneously to two
transmitters, two receivers, or one transmitter and one receiver.
This is made possible by the high natural isolation running to as
much as 30 db. and more between the two antennas as is
advantageously attained through the orthogonality configuration
thereof. The two orthogonal drooping dipole antennas are
effectively electrically close to ground over most of the 2 to 30
MHz. band and therefore generate upwardly directed radiation
patterns admirably suited for the preferred skywave mode of
operation. Efficient operation is attained by placing the antenna
couplers 24" at the top of the mast at the feed points of the
respective antennas. In doing so, and performing the impedance
match at this feed point, little power is lost in the RF coax cable
connected to the transmitter when the individual antennas are being
used in the transmitted mode of operation.
Each antenna coupler 24" tunes the impedance of its antenna in the
two antenna orthogonal antenna structure, along with the associated
inductor-balun to provide a 50-ohm impedance 1.5:1 VSWR maximum to
the transmitter connected thereto for the transmit mode of
operation. The tuning operation of the coupler 24" is automatically
controlled by the respective antenna coupler control 40 with each
coupler containing two capacitor modules and a discriminator module
and with the coupler enclosing case configuration being shaped to
specifically minimize RF coupling into the second channel, or other
antenna, of the two antenna system. The tuning elements of each
coupler are two variable capacitors with tuning control thereof
much the same as has been employed in other antenna and coupler
system product lines for shunt type antennas (complete detail not
shown). During tuning the discriminator 44 in each coupler 24"
senses the impedance of its associated antenna through the coupler
and produces polarized DC output voltages proportional to the phase
angle and the loading impedance magnitude. These phasing and
loading voltages both go to a zero volt null when the tuned
impedance becomes 50 +j0 ohms. The phasing and loading voltages are
fed to servo amplifiers in the control unit 40 that in turn drive
the positioning motors for the two capacitors in the respective
coupler 24". During tuning the loading capacitor 36' and the tuning
capacitor 25' in the antenna coupler 24" for one of the antennas of
the two antenna orthogonal antenna system produce an impedance of
50 + j0 with a 2:1 VSWR maximum at the coax line 28 center
conductor 27 connection to the descriminator 44. The tuning
capacitor 25' is positioned by the descriminator loading voltage
and zeroed to produce an inductive impedance with a 50-ohm series
resistive component. The inductive reactance is series resonanted
in phase by the loading capacitor 36' and the 50-ohm resistive load
is produced. Capacitor 36' is positioned by the descriminator
phasing voltage and servo drive to produce series resonance. Please
note that loading capacitor 36' remains bypassed at frequencies
when the associated antenna VSWR is low and with this capacitor not
required for tuning at such times. Further, the switchable shorted
length of the antenna inductor-balun supplements the tuning range
of the associated tuning capacitor 25' and loading capacitor
36'.
With reference to FIG. 7 a simplified schematic is presented of an
alternate balanced antenna 48 having a combination mast and balun
with a top mounted tunable antenna coupler structure 24" that is
similar in many respects to the antenna structure of FIG. 6 and
applicable for use in an orthogonal antenna structure such as that
illustrated in FIG. 5. Again with antenna 48 those components the
same or substantially the same as with the antenna structure of
FIG. 6 are given the same or primed numbers. It is of particular
interest to note that the antenna radiating elements 29' and 30'
are switch signal coupled through an individual paralleled coil 49
and capacitor 50 circuit for each. That is, they are switchable
into and out of interconnect between each respective balun
connection and the respective antenna wire element 29' or 30 ' via
individual shorting switches 51 being opened and closed. This is
with the switching action taking place as the respective wire
elements 29' and 30' go through series resonance as the antenna is
tuned higher in each balun switched frequency-tuning band and the
switches 51 being opened at the wire radiating elements go through
the series resonant operational state. In FIG. 8 the antenna
structure of 48 is shown in greater schematic detail than in FIG. 7
and additional component detail such as indicated in FIG. 5 and
some that is shown in the schematic of FIG. 6 is included with
however some differences therefrom. Among differences with this
embodiment the RF and discriminator wires are housed in the antenna
mast and balun tube 21' and the power for torque motors and the
tower balun shorting switch control wires are housed in the other
combination mast and balun tube 22' . Furthermore, the control
wires to the individual switch control relays 52 are carried in
their respective balun tubes 21' and 22.varies. . This is with the
switching relays 52 controlling the switches 51 for closed shorting
out or to open to include the paralleled coil 49 and capacitor 50
circuits in the connection between the antenna radiating elements
29' and 30' respective balun tubes tops. Please note, that in this
embodiment the insulator tie-on link blocks 53 provide electrical
isolation between the antenna radiating elements 29' and 30' and
tube top mechanical tie connective cables 54 fastened to the tops
of the respective combination mast and balun tubes 21' and 22'.
This structure is required with the paralleled coil 49 and
capacitor 50 circuits so they may be switched into the out of
electrically conductive circuit state between the tops of the tubes
21' and 22' and the respective radiating elements 29' and 30'.
Please note, the more specific inductor balun shorting switch 37b
detail such as would be employed for the shorting switches 37a and
37b and, if there are more, 37c etc.
Operational results are portrayed by the received signal level vs
time tracing of FIG. 9 for both antennas of a structure such as
shown in FIG. 5, or for that matter such as alternately shown in
FIG. 3, with an appropriately tuned combination mast and balun and
top mounted antenna coupler structure being used in the receive
mode in Richardson, Tex. for a CW signal eminating from a
transmitter operated in the skywave mode of operation at a location
approximately 100 miles north of the orthogonal receiving antenna
with atmospheric and ionospheric conditions as they existed at 1330
hours on Apr. 17, 1969. Further, the colocated antennas of the two
antenna orthogonal antenna receiving structure are located east and
west, and north and south respectively with the receive signal
being a CW signal of 9.657 MHz. It is interesting to note and quite
significant that the two received signals on the antennas of the
orthogonal antenna structure are uncorrelated to a high degree in
that while one signal is fading the other signal is at a maximum.
This is particularly so with an operating frequency near an optimum
skywave frequency, such as was the case here, with transmission
over a 100-mile path the two received signals having
advantageously, essentially a negative one correlation coefficient.
Such a negative one correlation coefficient between the two
received signals with one antenna sensed signal being a maximum as
the other is a minimum is typified by the two respective antenna
received signal recorded traces as the ideal situation antenna
reception wise particularly for diversity reception.
With the embodiment of FIG. 10 another alternate approach is
provided for tuning an antenna and balun system with a variable
capacitor interconnecting the balun tube tops where components the
same are numbered the same, and some much the same are given primed
numbers, as their corresponding counterparts in the embodiments of
FIGS. 1, 4, 6, or 7. In this embodiment the center conductor 27'
extension from RF coax 28, connected to an RF translating system
55, is provided with a series of switches 56a, 56b, 56c or even
more as the case may be. These switches may all be closed to, in
effect, provide through feed to the top of the balun such as is the
condition with the embodiment of FIG. 1 or they may be selectively
thrown, individually, to selectively provide balun feed to
different selected points vertically up the balun via switch
completed crosstie connection feed lines 57a, 57b, and 57c. This
establishes cross feed from the respective feed-actuated switch
56a, 56b, 56c of line 27' to the opposite vertical combination mast
and balun tube 22" instead of having the feed line 27' being closed
all the way up to the top of mast and balun tube 21" for cross
connection there to the top of combination mast and balun tube 22".
Here again shorting switches are provided with the balun to provide
cross shorting paths in higher and higher frequency switch selected
tuning bandwidths progressively via switches 37a, 37b, and 37c from
the lowest frequency bandwidth with ground plane plate 23 being the
shorting agent for the shorted balun transmission line
configuration. With the shorted balun cross connections switchable
as desired and the switches for varying the feed points of the
balun, and with the variable capacitor 25, a very efficient highly
flexible high Q inductor system is provided. This is with the balun
being fed to provide impedance matching in bands, and where, when
the system is resonated by capacitor 25, the impedance at the balun
feed point being resistive. Please note that the value of
resistance should be within the SWR matching range of the
transmitter that may be, for example, a 3:1 SWR. This allows R to
be any value from 16.7 to 150 ohms with R.apprxeq.(L.sub.2 1L.sub.1
.sup.2 RA . Thus, it is possible to cover the lower HF range in
bands such as 2-3,3-4 and 4-6 mc. etc., and the configuration
hereby should be satisfactory for the entire 2 through 30 mc. range
with enough bands being provided although only four are provided
for in the embodiment of FIG. 10. With this antenna employed in a
coplanar relation with another such antenna to form an orthogonal
antenna system the desired right-angle antenna projected planar
configuration is readily maintained sufficiently well enough in the
field to insure at least 25 to 30 db. of antenna mutual isolation.
This is good enough mutual isolation that there should be little
interaction between transmitters during tune up and little cross
modulation between them. In fact such mutual isolation has proven
good enough so that simultaneous transmission from one antenna and
reception via the other is practical with only a fairly small
frequency separation between the transmitting antenna and the
receiving antenna required.
The balanced drooping dipole configuration of FIG. 11 is an
alternate approach that is particularly well suited for use in an
orthogonal antenna system where the antennas go resonant around 7
mc. and the feed becomes a low Q tuned balun with more selectivity
thereby achieved. This is accomplished by reconfiguring to a tuned
balun circuit with the RF line 28 center lead 27" extended from
within the combination mast and balun tube 21'" via cross feed line
57a through the wall thereof without electrical contact therewith
to direct electrical connection with the combination mast and balun
tube 22'" at a location relatively closely spaced from the shorted
bottom of the balun structure. In addition to this low balun feed
point feature, such as would be attained in the embodiment of FIG.
10 by the throwing open of switch 56a to the cross feed line 57a,
the tuned balun structure is provided at the top with inductive
coaxially located lines 58 and 59 extended down within the tops of
the combination mast and balun tubes 21'" for a portion of the
lengths thereof to an interconnection therebetween and through the
walls of the tubes 21'" and 22' " by an interconnecting line 60.
The antenna radiating elements 29" and 30" are directly connected
to the tops of lines 58 and 59 without making electrical contact
with the tubes 21'" and 22'". This approach presents a very high
selectivity factor such as may be desired for certain specific
frequency ranges.
Referring now to the orthogonal antenna configuration of FIG. 12
arrowhead-type radiating elements 29" and 30" are employed that are
balanced with respect to each of the individual antennas thereof.
The radiating elements 29" and 30" extend from respective tuned
balun feed points in a drooping dipole configuration to arrowhead
pointed outer ends thereof. Each shank 61 of each arrow head is
tied by an intervening dielectric material rope 62 or like
intervening insulator to the corresponding opposite shank 61 of the
adjacent radiating element 29" or 30" of the other antenna. This
helps insure the attainment of a square antenna configuration and
maintains the desired right angle between the two antennas of the
orthogonal antenna structure. Please note further, that the
arrowhead V ends of elements 29" and 30", since they are a
high-voltage high-power radiating points in the antenna structure,
are terminated approximately nine feet above the ground for
personnel safety. The points of the V ends of elements 29" and 30"
are connected through insulators 31 and tie lines 32 to ground
anchor stakes 33.
With the balanced drooping dipole orthogonal antenna structure of
FIG. 13 the individual antenna and antenna balun feed structures
have top mounted antenna couplers 24", such as employed with the
embodiment of FIG. 7 and 8, feeding radiating element structures 62
of a triple wire element configuration that being in a uniformly
laterally electrically balanced relation are consistent with the
attainment of the desired degrees of mutual isolation between the
two right-angled colocated antennas of an orthogonal antenna
system. Please note that such triple wire radiating element
structures 62 may be used with various other tuned balun structures
hereinbefore described in addition to that of FIGS. 7 and 8.
With the embodiment of FIG. 14 antenna radiating element structures
63 each include wires 64 and 65 of different lengths utilized in a
balanced drooping dipole orthogonal antenna structure with such
antenna radiating elements usable with any of the tuned combination
mast and balun structures illustrated, and with these multiple
radiating element structures 63 being of balanced length design
from end to opposite end in each antenna and in right angles
orthogonal antenna relation in the ground projected planar sense.
It is interesting to note that at lower frequencies the longer wire
elements will take the majority of feed energy with tuned resonance
thereof, and as higher frequencies are achieved above a certain
point the shorter elements attached to the same feed points will
take the bulk of the energy as they are brought into resonance.
Obviously, more than just two such various length radiating
elements could be connected to individual feed points as long as
they are in balanced relationship with respect to both sides or
ends of each antenna. Further, please note that insulators 66
support the outer ends of the shorter radiating element wires 65
relative to or from the longer radiating element wires 64 that are
also part of the guy wire system for the orthogonal antenna mast
and balun structure. Relatively short tag lines 32, extended from
insulators 31 to earth stakes 33, are provided with the structure
just as have been indicated with various other embodiments
presented hereinbefore.
Whereas this invention is here illustrated and described with
respect to several specific embodiments thereof, it should be
realized that various changes may be made without departing from
the essential contributions to the art made by the teachings
hereof.
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