U.S. patent number 3,742,358 [Application Number 05/102,597] was granted by the patent office on 1973-06-26 for tethered airborne communications and information transfer system.
Invention is credited to Richard S. Cesaro.
United States Patent |
3,742,358 |
Cesaro |
June 26, 1973 |
TETHERED AIRBORNE COMMUNICATIONS AND INFORMATION TRANSFER
SYSTEM
Abstract
A tethered balloon including means for controlling the height
thereof is utilized as an airborne platform for transmitting and
receiving apparatus including a multiple antenna assembly. The
antenna assembly is suspended from a gimbal or ball joint
configuration attached to the balloon so that it is gravity
stabilized in the vertical plane. The antenna assembly itself is
comprised of a plurality of independently rotatable coaxial shafts
having respective antenna means coupled thereto. The shafts are
hung from a pendulum arm member which is freely moveable within a
vertical cone angle limit of 45.degree. and maintains vertical
orientation to within .+-.2.degree.. The rotation of each of the
coaxial shafts is independently controlled from a ground station by
means of a control signal to selectively point each antenna means
in a predetermined compass direction. Additionally, each coaxial
shaft couples respective transmitter-receiver means to its antenna
means in order to provide selective signal transfer between the
ground station and/or other similar airborne systems.
Inventors: |
Cesaro; Richard S. (Bethesda,
MD) |
Family
ID: |
22290668 |
Appl.
No.: |
05/102,597 |
Filed: |
December 30, 1970 |
Current U.S.
Class: |
455/9; 343/705;
343/758; 455/13.1; 455/13.3 |
Current CPC
Class: |
H04B
7/185 (20130101); H04B 7/18504 (20130101) |
Current International
Class: |
H04B
7/185 (20060101); H04b 001/60 () |
Field of
Search: |
;325/4,118,115,113,185,3,5,15 ;343/756.5,758,705 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mayer; Albert J.
Claims
Having thus described the present invention with what is considered
at present to be the preferred embodiment of the subject invention,
I claim as my invention:
1. A system for receiving and transmitting electromagnetic
radiation including various types of radio signals, TV signals as
well as other types of information and/or data communication
signals, comprising, in combination:
airborne apparatus for providing a mounting platform for electronic
transmitting and receiving apparatus;
a gravity stabilized antenna assembly suspended from said airborne
apparatus, said antenna assembly being comprised of (a) a mounting
base attached to the underside of said airborne apparatus including
a ball-joint housing depending therefrom, said housing having a
downwardly depending side portion and a lower end portion having a
circular opening therein, said side portion also including an
inwardly projecting ball bearing mount intermediate its length and
a tapered race type ball bearing assembly having a concave bearing
surface affixed thereto, a spherical member of predetermined
diameter resting on said concave bearing surface, said diameter
being of such a magnitude that the center of the sphere is located
above the uppermost contact point between the spherical member and
the ball bearing assembly, said opening additionally having an
inwardly angulated circular damper member affixed thereto the outer
surface of which defines a hypothetical cone having an apex at the
center of said spherical member, (b) a pendulum arm member attached
to one extremity to said spherical member and projecting through
said damper member and being suspended therefrom in substantially
vertical alignment, (c) a support member attached to the other
extremity of said arm member, and (d) a plurality of coaxial
cylindrical shafts which are independently rotatable about the
central longitudinal axis thereof mounted on said support member
and wherein selected shafts of said plurality of shafts each
additionally includes separate electrical signal transmission line
means carried by the respective shaft side wall for coupling
electrical signals from one end of the respective shaft to
substantially the opposite end thereof;
respective antenna means mounted at said one end of said selected
coaxial shafts and being coupled to said respective transmission
line means;
a ground station for controlling said airborne apparatus;
antenna directional control means coupled to said selected coaxial
shafts for properly pointing the respective antenna means in a
predetermined compass heading in a substantially horizontal plane,
said control means including a telemetry control radio link with
said ground station whereby each antenna means is independently
oriented in response to a compass heading signal transmitted to
said control means from said ground station;
respective electrical signal transmitter-receiver apparatus located
on said airborne apparatus and coupled to said antenna means and
additionally including respective electrical slip ring assemblies
integral with said selected shafts, coupled to the opposite end of
said respective transmission line means; and
electrical signal command and control apparatus, located on said
airborne apparatus, coupled to each of said signal
transmitter-receiver apparatus for selectively controlling the
operation of the respective signal transmitter-receiver apparatus
to provide, (1) an "up-down" communication link with said ground
station including the transfer of command and control signals
therefrom as well as the transfer of communications signals on one
or more communications channels to said airborne apparatus
including said signal transmitter-receiver apparatus by means of at
least one of said antenna means, (2) a transmitting and receiving
link for a local ground area coverage by at least one other of said
antenna means, and (3) a communication air-to-air relay link along
a substantially horizontal direction by at least one of yet another
of said antenna means.
2. The invention as defined by claim 1 wherein said airborne
apparatus comprises a lighter than air vehicle.
3. The invention as defined by claim 2 wherein said lighter than
air vehicle comprises a balloon.
4. The invention as defined by claim 1 wherein said directional
control means includes a flux gate transmitter at said ground
station for providing a compass heading signal for each of said
antenna means via said "up-down" link and wherein each of said
selected coaxial shafts is coupled to a flux gate compass system
and additionally including means responsive to the output of said
compass system to rotate said shaft in a predetermined direction in
accordance with said compass heading signal.
5. The invention as defined by claim 4 wherein said last-recited
means comprises an electrical drive motor and an electrical servo
system coupled between said flux gate compass system and said drive
motor for controlling the operation of said drive motor.
6. The invention as defined by claim 1 wherein said signal
transmitter-receiver apparatus includes means for multi-channel
electrical signal communications.
7. In an electromagnetic signal communication system,
a plurality of tethered aircraft disposed at predetermined heights
above the surface of the earth in order to provide respective free
space antenna platforms for electronic signal receiving and
transmitting apparatus;
a ground based receiving and transmitting station located beneath
each of said aircraft and including means for controlling the
aircraft and means for transmitting and receiving a plurality of
electrical signals to and from the respective aircraft and means
for transmitting at least a first and a second control signal
thereto;
each of said aircraft additionally including a multiple antenna
structure comprising a pendulum type gravity stabilized antenna
mount comprised of (a) a mounting base attached to the underside of
said airborne apparatus including a ball-joint housing depending
therefrom, said housing having a downwardly depending side portion
and a lower end portion having a circular opening therein, said
side portion also including an inwardly projecting ball bearing
mount intermediate its length and a tapered race type ball bearing
assembly having a concave bearing surface affixed thereto, a
spherical member of predetermined diameter resting on said concave
bearing surface, said diameter being of such a magnitude that the
center of the sphere is located above the uppermost contact point
between the spherical member and the ball bearing assembly, said
opening additionally having an inwardly angulated circular damper
member affixed thereto the outer surface of which defines a
hypothetical cone having an apex at the center of said spherical
member, (b) a pendulum arm member attached at one extremity to said
spherical member and projecting through said damper member and
being suspended therefrom in substantially vertical alignment, (c)
a support member attached to the other extremity of said arm
member, and (d) a plurality of coaxial shafts attached to and
suspended from said antenna mount in a substantially vertical
direction and including electrically controlled means for
independently rotating a selected number of said shafts about the
center longitudinal axis thereof, said selected number of said
coaxial shafts each additionally including separate transmission
line means mounted within the respective shaft side wall and
extending substantially between each end thereof, antenna means
attached to the lower extremity of said selected number of coaxial
shafts and coupled to the respective transmission line means,
independent transmitter-receiver means and slip ring coupling means
integral with said selected shafts coupled to the respective
transmission line means at the other end of the respective shaft
for receiving or transmitting signals to the respective antenna
means;
means coupled to said selected number of coaxial shafts for
rotating each shaft independently to the predetermined azimuth
direction in accordance with a compass setting transmitted from
said ground station via said first control signal transmitted from
said ground station whereby at least one antenna means is directed
toward said ground station, at least one other antenna means
directed toward a predetermined local area under the respective
aircraft as determined by the subtended radiation pattern of the
antenna means, and at least one still another antenna means is
directed toward another tethered aircraft of said plurality of
aircraft; and
circuit means located on each said aircraft, being responsive to
said second control signal transmitted from said ground station to
selectively operate each said transmitter-receiver means to relay
communication signals between adjacent tethered aircraft and to
provide communication signal transfer between the respective ground
stations and aircraft.
8. The invention as defined by claim 7 wherein said plurality of
aircraft are comprised of lighter than air balloons and wherein
said ground station additionally includes means for controlling the
height of the respective balloons as well as means for monitoring
the condition thereof.
9. The invention as defined by claim 8 wherein said first recited
means comprises a tether cable and wherein said tether cable
includes means for coupling electrical power from said ground
station to said antenna platform.
10. The invention as defined by claim 7 wherein said at least one
of said antenna means comprises a first type antenna, said at least
one other antenna means comprises a second type antenna, and said
at least one yet another antenna means comprises a third type
antenna.
11. The invention as defined by claim 10 wherein said first type
antenna comprises a spiral antenna, said second type antenna
comprises a dish type antenna, and said third type antenna
comprises a parabolic cylindrical type antenna.
12. The invention as defined by claim 7 wherein said means for
transmitting and receiving a plurality of electrical signals
comprises a multi-channel transmitter and a multichannel receiver
of microwave signals.
13. The invention as defined by claim 12 and additionally including
a frequency synthesizer coupled to said transmitter and said
receiver for respectively coupling at least one local oscillator
signal thereto for generating an IF signal.
Description
BACKGROUND OF THE INVENTION
2. Field of the Invention
This invention relates generally to electronic communications and
information transfer systems and more particularly to a free space
system incorporating an airborne antenna system capable of
radiating and receiving electromagnetic energy over relatively long
ranges and large earth areas in order to meet specific geographic
application requirements.
2. Description of the Prior Art
The concept of removing radiating and receiving antenna systems
from ground based towers or masts and elevating the systems by
means of airborne apparatus for covering a relatively larger area
is well known to those skilled in the art. For example the concept
of tethered balloon antenna systems is taught in such references as
British Pat. No. 358,972; U.S. Pat. No. 2,641,756; and U.S. Pat.
No. 3,030,500. Additionally, the use of airplanes for providing an
airborne antenna platform is taught in U.S. Pat. No. 2,626,348.
U.S. Pat. No. 2,598,064 and U.S. Pat. No. 2,627,021, moreover,
discloses the use of a plurality of aircraft for providing a radio
relay system. Finally, the concept of using tethered hovercraft or
helicopters for microwave signal transmission is disclosed in U.S.
Pat. No. 2,995,740, and U.S. Pat. No. 3,241,145.
While the above noted prior art presumably operates as intended
there nevertheless exists certain limitations insofar as diverse
and multi-channel communication is concerned as well as selective
orientation or directivity of the channel propagation and
reception.
SUMMARY
The present invention is directed to an improved airborne radiating
and receiving antenna system for communications and information
transfer or radio, television, telephone, digital data signals,
etc. for obtaining not only predetermined ground area coverage, but
also a communication common carrier network relay capability over
relatively long distances. Briefly, the subject invention is
directed to tethered airborne apparatus utilized as a radiating and
receiving platform and including means for controlling the height
of the airborne apparatus for specific operational requirements.
The airborne apparatus is preferably comprised of a lighter than
air device such as a balloon under which is mounted a gravity
stabilized multiple antenna and transceiver assembly suspended from
a universal ball joint subassembly which has a limited freedom of
movement. The antenna assembly comprises a plurality of
independently rotatable coaxial shafts mounted on a base member
attached to the ball joint subassembly, thereby forming a
substantially vertically aligned pendulum arm which is adapted to
maintain a vertical orientation by means of its own weight.
Respective transmitter-receiver means and antenna means are coupled
to either end of selected coaxial shafts which additionally include
transmission line means for coupling electrical signals
therebetween. Each of the selected coaxial shafts and attached
antenna means is controlled in azimuth or horizontal plane by means
of telemetry control from a ground station which radiates a compass
heading signal via a flux gate transmitter to the antenna assembly.
A flux gate compass system controls a servo system coupled to each
of the selected coaxial shafts to aim the respective antenna means
in a predetermined compass direction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a system embodying the
principles of the present invention;
FIG. 2 is a schematic representation of a long distance
communications network providing an air-to-air relay of electrical
signals as well as ground station transfer at predetermined
intervals;
FIG. 3 is a representation of a typical radiation pattern and
network contemplated by the subject invention;
FIGS. 4A and 4B is an elevational view partially in vertical
transverse section of a plurality of independently controlled
coaxial shafts coupling respective transmitter-receiver means to
antenna mounting pads located at the lower extremity thereof;
FIG. 5 is a view of one type of antenna means contemplated for use
in combination with the subject invention;
FIG. 6 is a view of a second type of antenna means utilized by the
subject invention;
FIG. 7 is a view of yet another type of antenna means utilized by
the subject invention;
FIG. 8 is a block diagram of a ground based multiple channel
communication transmitter utilized in combination with the subject
invention;
FIG. 9 is a block diagram of a ground based multiple channel
communication receiver adapted to receive signals from the antenna
system contemplated by the subject invention;
FIG. 10 is a block diagram of a typical airborne relay
subsystem;
FIG. 11 is a block diagram illustrative of one airborne receiver
apparatus shown in FIG. 10;
FIG. 12 is a block diagram illustrative of one airborne transmitter
apparatus shown in FIG. 10; and
FIG. 13 is a block diagram illustrative of another
receiver-transmitter apparatus shown in FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings wherein like numerals refer to like
parts and more particularly to FIGS. 1 through 3, which is
generally illustrative of the inventive concept of the present
invention, FIG. 1, inter alia, discloses a pair of lighter than air
free space aircraft consisting of tethered balloons 10. It should
be observed, however, that this is shown by way of a preferred
embodiment only since when desirable other types of tethered
airborne apparatus may be utilized as well such as dirigibles,
helicopters or even airplanes. Each of the balloons 10 is connected
to a tether line or cable 12 which is connected to a winch 14
located on the ground for providing selective altitude control of
the balloon 10 and thus provides a variation in antenna platform
heights as required for specific geographic locations and/or signal
communication requirements. A base member generally illustrated by
reference numeral 16 is mounted on the underside of each balloon 10
from which is suspended a multiple antenna assembly 18 which is
enclosed within a wind screen 20. The base member 16 is also
adapted to include transmitting and receiving apparatus not shown
as well as suitable command and control circuitry and the necessary
power supplies. Primary electrical power for this apparatus can
either be obtained from a respective ground control station 22
coupling power to the airborne base 16 up the tether cable 12 or
the balloon itself may additionally include a self-contained
electrical power generating system.
Each balloon 10 and its respective transmitter-receiver apparatus
which may be for example a plurality of transceivers adapted to
provide an up-down communication link between itself and the
control ground station 22 by means of one antenna assembly 26 as
well as transmitting and/or receiving signals to and from one or
more satellite ground stations 24 within the respective local area,
for example area A defined by the radiation pattern of another
antenna assembly 28. Additionally, the antenna system 18 is adapted
to provide a direct air-to-air communication relay link between an
adjacent airborne system similar to itself. This is provided by one
or more still other antenna assemblies 29. The ground station 22 is
adapted to provide all interface functions with the respective
airborne apparatus including directional control of the antenna
elements, as well as controlling the overall operation of the
receiving and transmission apparatus and the command and control
circuitry. This will be considered in detail subsequently.
A balloon 10 tethered at a height h is adapted to
electromagnetically radiate and receive information in a
substantially circular area (FIG. 3) defined by A = .pi.R.sup.2.
Information can also be relayed by means of two balloon antenna
systems 10 separated by a distance 2R over a distance 4R. If the
parameter R is considered the line of sight distance, a balloon
having an altitude h = 10,000 feet, will have a distance R which is
in the order of 140 miles. Therefore, local area coverage within
the order of 63,000 square miles will be provided while a long line
transmission capability with two balloon antennas would be in the
order of 550 miles. The following table is more illustrative of
typical values for a communication system illustrated in FIG. 1 as
compared with a conventional TV transmission tower:
TABLE I
Tethered Altitude height h 5000ft. 10,000ft. 15,000ft. Single
Station horizon radius line of sight R 100.0mi. 140.0mi. 170.0mi. D
200.0mi. 280.0mi. 340.0mi. Long Line Transmission, two stations
dist. 4R 400.00mi. 560.0mi. 680.0mi. Local Ground area radiated
A.sub.L A.sub.L 31,400 62,800 94,200 single station sq. mi. sq. mi.
sq. mi. Present Tv Tower ground 700 700 700 area radiated sq. mi.
sq. mi. sq. mi. Ratio of area covered by single balloon station to
45.0 89.0 134.0 area covered by times times times conv. TV station
more more more
As noted earlier, the ground station 22 provides an "up-down" link
with the airborne system and performs two functions: (1)
controlling the airborne system and (2) transmitting and/or
receiving communications signals therebetween. Accordingly, two
transmitting and receiving antennas 30 and 32 are located at the
particular ground station and are coupled to apparatus, not shown,
housed in the station. The satellite stations 24, however, are
shown including but one transmitting-receiving antenna 34. This is
because its purpose is primarily for the transfer of communication
signals either in single channel or multi-channel configurations;
however, when desirable a control function could be added. The
satellite stations 24 may be, for example, automotive vehicles
having two way mobile phone service, fixed installations such as
schools including educational TV apparatus, police stations,
radio-FM-TV stations, or commercial activities providing high speed
computer digital information transfer, teletype and/or telephoto
transmission as well as any other types of information transfer
both in analog and digital modes. It can be seen, therefore, that
any desired configuration of balloon locations can be utilized to
configure the network either stretched out in length or for
encompassing a predetermined closed ground area, both of which are
illustrated in FIG. 3.
Referring now to FIG. 2, it is meant to be illustrative of a long
line relay network which may stretch, for example, 2,000 miles. The
ground station 22 comprising an end terminus 1 for example, can be
adapted to couple up to 14 channels of one-way transmission plus
the required telemetry and command signals to the balloon 10 which
is then relayed to the relay 1 balloon 10 which is also coupled to
its respective ground station 22 identified as a local drop insert
station No. 1 wherein for example one channel may be dropped or
inserted with the required telemetry command as well as including
one local monitor channel. The relay number No. 1 is then coupled
to any number of relay balloons 10 shown as relay n which is
similar in operation to relay number No. 1. Relay n couples to a
terminus number 2 balloon 10 at the end of the relay network which
then is coupled to the ground station 22 included in terminus
number 2 which is substantially identical to terminus number No. 1.
Also, two-way transmission between terminus number 1 and terminus
number 2 as well as the intermediate relay stations can be
mechanized wherein 7 channels, for example, are transmitted in each
direction.
Typically a long line video network would include 7 channels
transmitting in one direction (west) a band including 7925-8118.5
MHz while seven channels transmitted in the opposite (east)
direction would cover a band of 8124.5 to 8318.0 MHz. Up to seven
channels received from the east would cover the band 7300-7493.5
MHz while up to seven channels received from the west would cover
7499.5-7693.0 MHz. All of these operations would be going on at the
same time. The local drop/insert at each balloon relay point would
permit local insert in the 7699-7721.5 MHz range, local drop in the
8324-8346.5 MHz range, command in the 7727.5-7750.0 MHz range, and
monitor in 8352.5-8375.0 MHz range. This network is illustrated for
various purposes of illustration only and is not meant to be
considered in a limiting sense, since any combination of
frequencies or channels can be utilized as desired. Additionally,
each of the terminus balloon communications systems can be
transformed into relay repeaters simply by reorienting the antenna
structure and suitably interconnecting the electronics packages in
the airborne equipment by means of the command and control radio
link coupling the airborne system to the respective ground control
station. A typical ground station transmitting and receiving
apparatus adapted for use in a network such as shown in FIG. 2 is
disclosed in FIGS. 5 and 6, respectively, and will be treated
subsequently.
However, attention is now directed to the free space transmitting
and receiving apparatus mounted on the tethered balloon 10 and
which is shown in FIGS. 4A and 4B. Referring now to FIG. 4A, the
base 16 is secured to the underside of the balloon 10 shown in FIG.
1 and additionally includes a universal ball joint assembly 34
comprised of a spherical member 36 mounted in a ball bearing
assembly 38 secured to the vertical arms 40 and 42 which also form
part of the base 16. The center of the sphere 36 is located above
the upper contact point of the roller bearing assembly 38 and a
pendulum arm member 44 is coupled to the lower surface of the
sphere 36 so that it is adapted to hang vertically therefrom due to
its own weight as well as the apparatus to be described connected
thereto. The weighted pendulum arm 44 is adapted to point downward
in the direction of local gravity. A circular rubber damper member
46 is mounted on inwardly facing projections on the end of arms 40
and 42 which acts as a limit stop for the angle of sway of the
pendulum arm 44. The damper 46 is slightly angulated inwardly which
in combination with the center of the sphere 36 defines a
hypothetical cone having its apex at the center of the sphere. The
pendulum arm 44 and the assembly attached thereto is thus gravity
stabilized vertically but having a limit determined by the rubber
damper member 46 which permits the pendulum to sway within a
45.degree. cone from the vertical which is more than enough motion
to allow for continued changes in balloon orientation with respect
to varying wind conditions. Local vertical is maintained by the
pendulum to .+-.2.degree. within the 45.degree. cone. In addition
to acting as a sway limit, the rubber damper member 46 acts as a
shock absorber when the pendulum arm tries to exceed this
hypothetical 45.degree. cone. The wind screen 20 shown in FIG. 1
provides protection against weather, wind and wind gusts which
would otherwise have a tendency to affect the pendulum action or
motion of the assembly shown in FIG. 4A. All other forces acting on
the pendulum arm 44 provide slow motion changes which are easily
compensated as well as the continual changes in wind forces acting
on the balloon 10 and its resulting directional motional
changes.
Considering now the apparatus attached to the end of the pendulum
arm 44, it consists, inter alia, of a mounting ring 48 which is
adapted to provide a mounting base for a plurality of concentric
independently rotatable cylindrical shaft members. In the specific
embodiment, shown in FIGS. 4A and 4B, four shafts 50, 52, 54 and 56
are illustrated; however, it should be noted that any desired
number of concentric shafts may be utilized depending upon the
desired configuration. These shafts 50 . . . 56 moreover are
attached to its respective adjacent shaft by means of an
intermediate roller bearing assembly which permits independent
rotation of each of the shafts about a common longitudinal axis
which is in a substantially vertical plane. More specifically, the
inner-most shaft 50, which could be considered the base shaft is
also rotatable but is supported on a roller bearing assembly 58 by
means of a collar 60 threaded onto the upper end of the shaft. The
collar 60 is secured to the upper race of the roller bearing
assembly 58 while the lower race is secured to a cylindrical frame
62 attached to the mounting ring 48. The frame 62, moreover, is
adapted to provide a suspension for the entire multi-shaft assembly
including the shafts 50 . . . 56. At the lower extremity of the
shaft 50 (FIG. 4B) a second roller bearing assembly 64 provides a
support for the adjacent shaft 52. The lower race thereof is
secured to the shaft 50 while the upper race of the roller bearing
assembly 64 is attached to the shaft 52. Additionally, a spacer
ring 66 provides a necessary separation from the outer and inner
surfaces of the shafts 50 and 52, respectively. Thus the inner-most
shaft 50 is adapted to rotate around its central axis on the roller
bearing assemblies 58 and 64 shown in FIG. 4A and 4B, respectively.
Rotation of the shaft 50 is provided by means of a drive motor 66
having its rotor attached to a bevel gear 68 which mates with a
beveled ring gear 70 secured to an annular rib member 72 near the
upper extremity of the shaft 50. By suitably activating the drive
motor 66, selective rotation of the shaft 50 can be provided. The
lower extremity of the inner-most shaft 50 shown in FIG. 4B
terminates in a circular mounting pad 74 which is adapted to
receive one or more antennas 76 shown in phantom view but which are
shown in greater detail in FIG. 5. The shaft 50 additionally
includes a signal transmission line 78 within the cylindrical shaft
wall which is adapted to terminate at one end in the antennas 76
and at the other end into an electrical slip ring assembly 80 which
couples to an electronic transmitter-receiver apparatus which is
shown schematically by reference numeral 82.
In a similar manner, the second inner-most shaft 52 is located on
the outside of the shaft 50 by means of the bearing assembly 84 and
the roller bearing assembly 64 previously mentioned. The inner race
of the bearing assembly 84 is secured to the outer surface of the
shaft 50 while the outer race is secured to the upper extremity of
shaft 52 which comprises a flared portion to which is attached the
beveled ring gear 86. The ring gear 86 couples to the bevel gear 88
which is connected to the shaft of a second drive motor 90. The
lower end of the shaft 52 is secured to the upper race of the
bearing assembly 64 shown in FIG. 4B and constitutes an annular
projection 92 forming an antenna pad to which one or more antennas
94 are adapted to be mounted. It can be seen that the shaft 52 is
relatively shorter than the shaft 50 with the mounting pad member
92 shown in FIG. 4B being located above the mounting pad 74. A
second independent signal transmission line 96 is located within
the side walls of the shaft 52 similar to the transmission lines 78
and terminates in a slip ring assembly 98 which couples into second
transmitter-receiver apparatus 100.
Similarly, the two outer-most shafts 54 and 56 are driven by
respective drive motors 102 and 104 being independently rotated by
the bevel and ring gear assemblies 105 and 106. The concentric
shaft assemblies including shafts 54 and 56 are mutually supported
by the bearing assemblies 107, 108, 110 and 112 in the manner
previously noted. The shaft 54 is relatively shorter than shaft 52
while longer than shaft 56. Its lower extremity terminates in an
antenna mounting pad 114 and additionally includes a vertically
oriented annular ring member 116 which is adapted to support one or
more antennas 118 which are shown in phantom view but are more
fully disclosed in FIG. 7.
Shaft 54 also includes an electrical signal transmission line 120
incorporated in the wall thereof which is adapted to be connected
to the antennas 118 as well as terminating in the slip ring
assembly 112 which in turn is coupled to a transmitter-receiver
apparatus 122. The outer-most shaft 56 has its lower termination
connected to a mounting pad 124 which includes the vertically
oriented member 126. This is adapted to provide a mount for one or
more antennas 128 which are similar to the antennas 118. Again, a
signal transmission line 130 contained in the sidewall of the
cylindrical shaft 56 is adapted to couple to the antennas 128 which
connects to the slip ring assembly 132 at the upper end of the
shaft as shown in FIG. 4A. The slip ring assembly 132 couples into
its respective transmitter-receiver apparatus 133 in the same
manner that each of the other concentric cylindrical shaft members
are adapted to couple respective signal transmission lines
contained therein between the antennas mounted at the respective
mounting pads to its transmitter-receiver apparatus. Thus, the
configuration shown in FIGS. 4A and 4B permit the antennas 76, 94,
118, and 128 to be selectively oriented in space independently of
each other by means of the respective drive motors 66, 90, 102 and
104. Since the entire antenna assembly thus described is suspended
from the mounting ring 48 attached to the pendulum arm 44, the
weight of the assembly provides the required vertical stabilization
while the drive motors produce aiming of the antenna members
coupled to the shafts in the horizontal or azimuth direction.
Before continuing further, attention now is directed to FIGS. 5, 6
and 7, which are typically illustrative of the antennas utilized in
combination with the assembly shown in FIGS. 4A and 4B. For
example, FIG. 5 is illustrative of the antenna configuration
mounted on the lowermost pad 74 shown in FIG. 4B and which is part
of the cylindrical shaft 50. The antennas 76 comprise spiral
antenna elements attached to the bottom surface of pad 74 by means
of the antenna base elements 134 secured to the pad 74 by means of
suitable hardware such as a nut and bolt. Each of the spiral
antenna elements 76 is commonly coupled to the transmission line 78
shown in FIG. 4B and are directed downward in a substantially
vertical orientation. This is for purposes of being pointed
directly at the ground station 22 shown in FIG. 1. Thus the antenna
elements 76 form one element of an air-to-ground or "up-down" link
for electrical signals coupled between the ground station 22 and
the electronic apparatus 82 shown in FIG. 4A. Spiral antennas are
preferred for the "up-down" or air-to-ground link because such
antennas have wide beamwidth and permit the ground station command
and control equipment to be located at a remote distance from the
ground tethering point. Furthermore, a high gain antenna is not
required and the spiral antenna is very light in weight. The number
of spiral antennas required depend upon the number of channels of
communication being established between the ground station 22 and
the airborne electronics system.
Referring now to FIG. 6, there is disclosed the preferred
embodiment of the antenna shown by reference numeral 94 in FIG. 4B
and which constitutes the antenna assembly for local radiation
coverage between the airborne system and the satellite stations 24
shown in FIG. 1. The antenna configuration shown in FIG. 6
comprises the slightly tapered reflector element 138 secured to a
swival base 140 attached to an arm 142 mechanically connected to
the pad 92 by suitable hardware. The swival connection between the
base 140 and the arm 142 permits adjustment of the directivity of
the reflector 138. Additionally an antenna feed member 144 is
included which is adapted to be connected to the transmission line
96 shown in FIG. 4B. Such an antenna provides a gain of
approximately 2dbm and permits information transfer in a
substantially circular downward hemispherical radiation pattern.
Simultaneous multi-channel wideband and narrow band information in
both transmission and receiving modes can be handled by this type
of an antenna.
Considering now the antenna means utilized for the long line or
relay type transmission and reception between airborne stations,
reference is made to FIG. 7 which discloses such apparatus. The
antenna disclosed therein is typical of either of the antennas
shown by reference numeral 118 or 128 shown in FIG. 4B and
comprises a section of a parabolic cylinder shown by reference
numeral 146 coupled to the respective vertical support element 116
or 126. The parabolic cylinder design is preferred because the
antenna gain and bandwidth are the same as a parabolic antenna of
similar diameter, however its main purpose is that the main beam is
not attenuated. There is a beamwidth reduction in the vertical
plane; however, this disadvantage is disregarded since the antenna
pointing direction will be substantially in the horizontal plane.
The parabolic cylinder antenna size in the parabolic dimension is
determined by the beamwidth desired and the gain requirements of
the system. An antenna having a gain in the 23-25dbm range is
desirable. The following Table II is illustrative of the power gain
in the effective area of other types of antenna configurations
which might be utilized when desired.
TABLE II
Antenna Type Gain Above Effective Isotropic Area Radiation
Isotropic Radiation 1.0 /4 .pi. Infinitesimal dipole or loop 1.5 .1
/4 .pi. Half wave dipole 1.64 p.2 /4 .pi. Optimum horn (mouth area
= A) 10 A/.lambda..sup.2 0.81 A Horn (max. gain for fixed length
mouth area = A) 5.6A/.lambda..sup.2 0.45 A Parabola or metal lens
6.3-7.5 A/.lambda..sup.2 0.5-0.6 A Broadside array (area=A)
"Billboard" 4.pi.A/.lambda..sup.2 (max) A (max) Omnidirectional
stacked array (length-L, stack interval .ltoreq. .lambda.)
.apprxeq.2L/.lambda. .apprxeq.L.lam bda./2 .pi.
referring now back to FIGS. 4A and 4B the ground station 22 (FIG.
1) is electromagnetically coupled to the airborne system by means
of the antenna 76. The ground station is intended to serve as the
master command and control for the entire airborne system attached
to the respective balloon. These functions include the necessary
electrical, mechanical and operational control of the system which
includes among other things, steering and directional control of
each of the antenna mounts including the respective cylindrical
coaxial shaft and the intercoupling of information between
selective antennas and the respective transmitter-receiver
apparatus coupled thereto. Thus the ground station selectively
intercouples the airborne antenna structure according to the
specific requirements of the respective location. More
particularly, all signals directed to and from the ground station
22 are coupled to and from the transmitter-receiver apparatus, of
predetermined type signals, 82 by means of the transmission line 78
and the slip ring assembly 80. For example, signals transmitted to
the airborne system appear at circuit means 146 which is coupled to
a command and control assembly 150 mounted on the base 16 by means
of an input harness assembly shown by reference numeral 148. The
command and control assembly 150 as well as the electronics
apparatus attached to the mount 48 is adapted to receive suitable
power supply potentials from a power supply 151 attached to the
base 16. The command and control assembly 150 is adapted to
selectively interconnect the transmitter-receiver apparatus 82,
100, 122 and 133 by means of an output harness 149 as well as
coupling directional control signals for each of the antenna shafts
which have been received from the ground station 22 by means of the
apparatus 82.
Independent directional or compass heading control of each antenna
assembly including the antennas 76, 94, 118 and 128 is maintained
by respective servo control systems shown diagrammatically by
reference numerals 152, 154, 156 and 158 coupled to the drive
motors 66, 90, 102 and 104. Each of the servo systems 152 . . . 158
is coupled to a respective flux gate compass system and synchro
control transformer shown generally by reference numerals 160, 162,
164 and 166 attached to the mounting ring 48 and which receive
inputs from respective flux gate transmitter apparatus shown
schematically by reference numeral 49 located at the ground station
22. A flux gate transmitter and compass system is well known to
those skilled in the art, an example of which is the Bendix type
15026. The flux gate transmitter on the ground provides the heading
signal which is coupled to the flux gate compass by means of the
transceiver 82 and the command and control assembly 150. The
desired respective headings are manually set on the ground.
Deviations in heading relative to magnetic North develop a signal
voltage proportional in level and phase to the deviation from the
magnetic North. These control signals actuate the servo system
connected to its respective drive motor which will rotate the
concentric shaft to which it is coupled to the proper heading in
azimuth. A system of this type is easily able to control the
directivity within .+-.2.degree.. Thus each of the concentric
cylindrical shafts 50 . . . 56 are independently oriented by means
of the flux gate compass system 160 . . . 166 which receive
individual heading signals from the ground station.
Having thus selectively oriented each of the four antenna
structures from the ground station 22, the "up-down" link sends
telemetric control signals to the command and control assembly 150
for controlling the transmission and reception to and from the
transmitter-receiver apparatus 82, 100, 122 and 133. For example,
apparatus 122 and 133 may be interconnected such that the antennas
128 coupled to the apparatus 133 are adapted to receive signals
which are then coupled to apparatus 122 for transmission from
antennas 118 in a "long-line" relay communications such as shown in
FIG. 10. A more detailed illustrative embodiment is shown in FIGS.
11 . . . 13. A local area communication signal for the surrounding
line of sight coverage of the airborne system is coupled to and
from the apparatus 100 which is coupled to the antennas 94. Any
desired combination of interconnections can be made under the
control of the ground station 22 via the "up-down" link including
the transmitter-receiver 82 and the command and control assembly
150. The configuration shown in FIG. 4A and 4B provides a very
flexible communications system having a multi-channel flexibility
with diversity of operation as well as individual selective
orientation of each antenna configuration of the assembly as
controlled from the ground station.
In order to more fully understand the information transfer
contemplated by the subject invention, FIGS. 8 and 9 are
illustrative of a typical multi-channel communications transmitter
and receiver, respectively, adapted for use in combination with the
apparatus shown in FIGS. 4A and 4B. The ground station transmitter
shown in FIG. 8 discloses a seven channel configuration with means
provided for transforming it into a fourteen channel configuration
when desirable. Each input signal is coupled to a respective input
terminal 168-1 . . . 168-7. Considering for example channel 1, the
input signal is applied to a wide band modulator 170-1 such as a
spread spectrum generator or a video frequency UHF transmitter
which produces a modulated output signal of for example a 70MHz.
This signal is immediately mixed with a local oscillator frequency
of for example 544MHz applied from crystal oscillator 171 shown in
FIG. 9 in a mixer 172-1 which produces a "working" IF frequency of
for example, 614MHz. The IF signal is applied to a narrow band
filter 174-1 to reject the local oscillator frequency and the image
frequencies. The output of the narrow band filter 174-1 is next
applied to an IF amplifier 176-1 which provides a gain of, for
example, +13db. The amplifier IF signal is then mixed with a second
local oscillator signal in the mixer 178-1 coupled from a
synthesizer circuit 177 shown in FIG. 9 to transform the 614MHz IF
signal to an X-band RF frequency desired for the specific channel
i.e. channel 1. The other channels 2 through 7 would provide a
different X-band local oscillator RF frequency as determined by the
synthesizer outputs. The X-band output of the mixer 178-1 is passed
through an isolator 180-1 which provides an impedance match between
the mixer 178-1 and a second narrow band filter 182-1. The narrow
band filter 182-1 rejects the second local oscillator frequency and
the image frequencies. The channel 1 X-band signal is now fed to a
power amplifier 184-1 which may be, for example, a traveling wave
tube (TWT) amplifier which has an approximate net gain of +50db.
Following the TWT power amplifier 184-1, the X-band signal is
passed through a third narrow band filter 186-1 to reject noise
amplified by the traveling wave tube 184-1. Following the narrow
band filter 186-1, an isolator 188-1 and low pass filter 190-1
couple into an antenna feed 192-1 of a parabolic cylindrical
antenna 194. Since seven input feeds 192-1 . . . 192-7 are
illustrated, a system configuration comprised of 14 channels would
couple into the other seven input feeds by means of a circulator
196-1 . . . 196-7 coupled intermediate the narrow band filter 186
and the isolator 188. In either configuration, the isolator 188-1
reduces the cross coupling between antenna feeds and the low pass
filter 190-1 rejects channel harmonics. Thus what has been shown is
a seven or 14 channel X-band RF transmitter which is adapted to
radiate RF signals to the airborne system via the "up-down" link
antennas 76 for distribution by the command and control assembly
150 for coupling to one or more of the transmitter-receive
apparatus respectively associated with the antennas 94, 118 or 128,
as shown in FIGS. 4A and 4B.
Referring now to FIG. 9, the frequency synthesizer 177 is
additionally adapted to provide the local oscillator frequencies
for the receiver circuitry shown therein. FIG. 9 also discloses a
second crystal oscillator 198 which is adapted to provide a fixed
frequency of, for example, 684MHz, and which will be discussed
subsequently.
Directing attention now more particularly to the receiver apparatus
shown in FIG. 9, a parabolic antenna 204 having a gain in the range
of 28db and a beamwidth of 6.degree. is adapted to receive, for
example, 14 separate channel RF signals in the X-band range which
are fed to a wideband filter 206 and then to a low noise RF
amplifier 208 having an approximate gain of 35db and a noise figure
of 6.5db. These signals are then passed through a second wideband
filter 210 which is adapted to reject the noise due to the image
frequencies. Following the wideband filter 210 an isolator 212
couples the X-band signals into a mixer 214 which is adapted to
receive an X-band to S-band local oscillator signal from the
synthesizer 177. The output of the mixer 214 comprises 14 channels
of S-band frequencies which are fed into a 14 way power splitter
216. Seven of the outputs are terminated in substantially identical
resistive load impedances 218 while the remaining 7 signals are fed
to seven separate channel circuits. Each receiver channel circuit,
for example channel 1, includes a narrow band filter 220-1 which is
adapted to have a 20MHz bandwidth for one channel of S-band
frequency while rejecting the adjacent channel center frequency by
not less than 35db. The output of the narrow band filter 220-1 is
fed to a 24db IF amplifier 222-1. The output of the IF amplifier
222-1 is applied to the mixer 224-1 which receives a S-band to UHF
local oscillator signal from the synthesizer 177, which produces a
working IF frequency of for example, 614MHz. This IF signal is
passed through a 3db matching pad 226-1 and then to a second narrow
band filter 228-1 which rejects the local oscillator frequencies.
The 614MHz UHF IF frequency is next amplifier by an IF amplifier
230-1 including automatic gain control (AGC). The output of the IF
amplifier 230-1 is next coupled to a second mixer 232-1 through a
6db matching pad 234-1. The mixer 232-1 receives either a 544MHz
signal from the crystal oscillator 171 or a 684MHz signal from the
crystal oscillator 198 coupled thereto through a switch 200. The
554MHz signal applied to the switch 200 is identified as the NOR or
normal receive signal while the 684MHz signal is labeled the INV or
invert signal, for purposes of which will be explained
subsequently. The output of the mixer 232 provides an IF signal
which is in the range of 70MHz, which is applied to a suitable
demodulator circuit 238-1 through a low pass filter 240-1. The
output of the demodulator 238 appears at terminal 242-1 and
constitutes the desired output signal.
In the event that it is desired to relay certain types of
information such as spread spectrum signals which require
non-inversion of the signals, these signals would undergo an odd
number of hops or inversions from every other ground local
"drop/insert" station to the ground terminus shown in FIG. 2, and
would therefore be inverted. In order to maintain proper polarity
of the received signals, the two crystal oscillators 171 and 198
are utilized which are adapted to be 70MHz below and 70MHz above
respectively the working IF frequency of 614MHz. The proper LO
frequency is selected by means of the switch 236. It should be
pointed out, however, that in signal transmission, this facility is
not required and therefore only a single frequency, i.e. 544MHz is
applied to the apparatus shown in FIG. 8 from the crystal
oscillator 171. In an asymmetrical system, however, where more than
7 channels are to be received, the additional receiving channels
which are adapted to be coupled to the power splitter 216, replace
the load resistors 218 shown.
It should be pointed out that the frequencies provided by the
synthesizer 198 depend upon the desired system configuration. For
example, 14 transmitters require one set of local oscillator
frequencies while the 14 receiver circuits require a different set
of local oscillator frequencies and an odd number of hops between
terminus stations will require a different set of transmitter or
receiver local oscillator frequencies.
Referring now to FIG. 10, there is disclosed therein a typical
airborne long-line relay subsystem incorporating the apparatus
shown in FIGS. 4A and 4B which for example utilizes the antennas
128 as the receiving antennas and the antennas 118 as the
transmitting antennas. Each of the antennas respectively are
coupled to the transmitter-receiver apparatus 134 and 122 each of
which includes receiver apparatus shown more particularly in FIG.
11 and transmitter apparatus which is shown more particularly in
FIG. 12 and wherein both apparatus includes up to fourteen
channels. The respective receiver and transmitter elements
contained in each of the transmitter-receiver apparatus 122 and 133
is innerconnected through the command and control assembly 150 so
that proper innerconnection can be made for selectively utilizing
either the receiver or the transmitter portions of the apparatus
133 and 122. A synthesizer 202 is also included for providing at
least five local oscillator frequencies for proper operation of the
subsystem. Additionally, the "up-down" transmitter-receiver
apparatus 82 connected to the spiral antenna means 76 is also
coupled into the command and control assembly 150 and includes
apparatus for providing one local drop channel, one or two insert
channels plus one monitoring channel which is shown in more detail
in FIG. 13.
The receiver portion of the airborne transmitter-receiver apparatus
122 and 133 shown in FIG. 11 is identical to the ground terminus
receiver means shown in FIG. 9 from the wideband filter 206 up to
the IF amplifier 230 having AGC for the channels 1 through 7.
Considering channel 1 for purposes of illustration the output of
the IF amplifier 230-1 in FIG. 11 is fed into a two-way power
splitter 242-1, the outputs of which are coupled to two identical
matching pads 244-1 and 246-1. The signal from the pads 244-1 is
fed to the command and control assembly 150 for coupling to
transmitter apparatus shown in FIG. 12 while the output from the
pad 246-1 is adapted to be coupled to a 1 .times. 14 RF switch 248
coupled to the monitor and telemetry channel in the "up-down"
transmitter-receiver apparatus shown in FIG. 13.
With respect to the airborne transmitter apparatus shown in FIG.
12, it is substantially identical to the ground based transmitter
shown in FIG. 8 from the first IF amplifiers 176-1 . . . 176-7 to
the low pass filters 190-1 . . . 190-7 which couple to the
respective radiating antenna. It is to be noted that the input to
the respective IF amplifiers 176-1, etc. are coupled back to the
command and control assembly for innerconnection to the airborne
receiver apparatus shown in FIG. 11 and briefly described above.
The synthesizer 202 is adapted to couple the required local
oscillator frequencies as shown in FIGS. 11 and 12 so that
multi-channel signal input and output translation occurs between
the antenna 128 and 118 as shown in FIG. 10.
Referring now to FIG. 13, there is disclosed the airborne "up-down"
transmitter-receiver apparatus 82 noted in FIG. 10 as well as FIG.
4A. It includes circuit means for providing a local drop channel, a
local insert channel, and a monitor and telemetry channel to the
ground station via the spiral antenna means 76. Considering first
the local drop channel, it comprises apparatus substantially
identical to the airborne transmitter apparatus shown in FIG. 12
and is shown comprising the elements 176' . . . 190' which includes
the apparatus from the IF amplifier to the low pass filter. The
input to the IF amplifier 176' is selectively coupled to one of the
seven channel signals appearing at a selected output pad 246-1 . .
. 246-7 which is coupled thereto through the command and control
assembly 150. The channel signal to be dropped to the ground
station is coupled to the antenna means 76 from the low pass filter
190'.
The local insert channel apparatus shown in FIG. 13 is
substantially identical to the airborne receiver apparatus shown in
FIG. 12 with the exception that the wideband filters 206 and 210
have been replaced by narrow band filters 207 and 209. Also in
place of the 14 way power splitter 216 shown in FIG. 11 the
apparatus shown in FIG. 13 employs a two way power splitter 215,
one output of which is fed to the narrow band filter 220 while the
other output is coupled to a narrow band filter 250 which couples
into a mixer 252 which receives a command local oscillator
frequency from the synthesizer 202. The output of the mixer 252 is
fed into another narrow band filter 254 and then into an amplifier
256. The output of the amplifier 256 is coupled into a limiter and
discriminator 258 for obtaining command signals which are fed to a
logic circuit 260 which couples into the command and control
assembly 150. The insert signal which is fed to the amplifier 230
and the pad 246 is coupled into the command and control assembly
150 for selective coupling to one of the airborne transmitter
inputs shown in FIG. 12.
The command information which is decoded in the logic 250 and fed
into the command and control assembly 150 feeds back a control
signal to the 1 .times. 14 RF switch 248 by means of a circuit lead
262 which selectively controls the RF switch to select one of the
channel inputs from the airborne receiver apparatus shown in FIG.
11. The output is then coupled into transmitter circuitry 176" . .
. 190" which is substantially identical to the airborne transmitter
apparatus shown in FIG. 12 with the exception that a coupler 262 is
adapted to insert a telemetry signal coupled thereto from telemetry
logic circuitry contained in the command and control assembly 150.
This signal is applied through a modulator circuit 264, a mixer 266
which receives a telemetry local oscillator frequency from the
synthesizer 202 and an IF amplifier 268. Thus the monitor and
telemetry channel apparatus is adapted to couple information from
the low pass filter 190" to the spiral antenna means 76 for
transmission to the ground station.
What has been shown and described, therefore, is a multi-channel
airborne transmitting and receiving station mounted on the
underside of a tethered balloon and controlled from a ground
station which serves as the master command and control for the
entire system which includes controlling the electrical, mechanical
and operational parameters of the entire system, including control
of the "up-down" link, channel selection and routing, antenna
steering as well as safety circuits for the electrical system as
well as for emergency balloon dissent or destruction. The ground
station also includes systems, not shown, for monitoring of
information being translated into the network.
It should be pointed out that while the present system has been
shown with a certain degree of particularity, for purposes of
illustration only, the system disclosed is adapted to operate in
any desired mode or frequency range of electromagnetic signal
transmission and reception. Not only is the system adapted to
handle multi-channel X-band signal transmission as shown in FIGS. 8
. . . 13, but is also adapted to handle standard AM and FM radio
broadcasting as well as television transmission wherein amplitude
modulation of one carrier is utilized for video transmission while
the audio transmission occurs as FM modulation of a second carrier.
In addition selective types of UHF and VHF operation can also be
mechanized. Other types of information handling are also
contemplated e.g., telegraphy, telephony, facsimile, multichannel
multiplex voice frequency telegraphy, and analog/digital computer
data, etc.
Many other network combinations are adapted to be configured
utilizing the teachings of the subject invention which eliminate
the need for telephone poles, telephone lines, cables, microwave
towers and the usual elements involved in a conventional
information transfer network. The present system, moreover, can tie
into any existing conventional network or information distribution
system. For undeveloped geographic areas, the present invention is
particularly useful in that it permits an advance modern complex
information handling and distribution network system to be provided
in a very short time and at a very low cost. Furthermore, simple
conventional low cost electrical elements can be utilized in
assembling of a ground satellite station such that equipment costs
are comparable to normal high quality roof top mounted and driven
antennas or a receiver elements in home use at present. This
represents a substantial reduction in network cost and user cost
over present systems and provides a signal quality that is
technically of higher grade than with existing systems due to the
fact that no land line routing or multi-switching operations within
the land routing network are involved which inherently degrade
information quality. Direct transmission via the air-to-air relay
link maintains clean and undisturbed electromagnetic signals to its
final destination.
* * * * *