U.S. patent number 3,887,925 [Application Number 05/384,188] was granted by the patent office on 1975-06-03 for linearly polarized phased antenna array.
This patent grant is currently assigned to International Telephone and Telegraph Corporation. Invention is credited to Emmanuel J. Perrotti, Joseph C. Ranghelli.
United States Patent |
3,887,925 |
Ranghelli , et al. |
June 3, 1975 |
Linearly polarized phased antenna array
Abstract
There is disclosed herein a linearly polarized mat-strip phased
antenna array wherein the antenna array is phased by incorporating
in series relationship one or more mat-strip loaded line type phase
shifters in the mat-strip power division distribution network for
the mat-strip dipole elements and/or a combined mat-strip dipole
element and phase inverter. Two embodiments are illustrated.
Inventors: |
Ranghelli; Joseph C. (Brooklyn,
NY), Perrotti; Emmanuel J. (Ramsey, NJ) |
Assignee: |
International Telephone and
Telegraph Corporation (Nutley, NJ)
|
Family
ID: |
23516377 |
Appl.
No.: |
05/384,188 |
Filed: |
July 31, 1973 |
Current U.S.
Class: |
343/795; 343/814;
333/238; 342/374 |
Current CPC
Class: |
H01Q
3/38 (20130101); H01Q 9/065 (20130101) |
Current International
Class: |
H01Q
3/30 (20060101); H01Q 9/06 (20060101); H01Q
9/04 (20060101); H01Q 3/38 (20060101); H01q
009/28 () |
Field of
Search: |
;343/795,814,854
;333/84M |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lieberman; Eli
Attorney, Agent or Firm: O'Halloran; John T. Lombardi;
Menotti J. Hill; Alfred C.
Claims
We claim:
1. An antenna array comprising:
N linearly polarized mat-strip center fed dipole elements
indicidually disposed on opposite sides of a printed circuit board,
each of said N elements having a given orientation;
a ground plane superimposed relative to and associated with said N
elements;
a mat-strip power distribution network disposed on said board
coupled to said N elements;
said N elements, said ground plane and said distribution network
cooperating to produce a linearly polarized antenna beam; and
a mat-strip phase shifting arrangement selectively coupled to said
distribution network to control said antenna beam to have different
selected angular directions, identical portions of said phase
shifting arrangement being carried on both surfaces of said
board.
2. An antenna array according to claim 1, wherein
said phase shifting arrangement includes
at least one phase shifter having
a one quarter wavelength mat-strip impedance transformer disposed
in said distribution network and carried by said board,
a first shunt mat-strip transmission line carried by said board and
extending perpendicular from one end of said transformer,
a second shunt mat-strip transmission line carried by said board
and extending perpendicular from the other end of said transformer
parallel to said first shunt transmission line,
four normally non-conducting switching diodes carried by said
board, each of said four diodes being connected to an end of a
different one of the conductors of said first and second shunt
transmission lines, and
four radio frequency ground terminating and direct current biasing
printed circuit pads carried by said board, each of said four pads
being connected to a different one of said four diodes;
a source of switching voltage; and
a first switching arrangement connected between said source and
each of said four pads to render each of said four diodes
conductive to radio frequency ground said first and second shunt
transmission lines by said four pads to provide a predetermined
amount of radio frequency phase shift in said distribution
network.
3. An antenna array according to claim 2, wherein each of said four
diodes is a PIN diode.
4. An antenna array according to claim 3, wherein each of said PIN
diodes is parallel to said board.
5. An antenna array according to claim 2, wherein
each of said N elements includes
a first dipole wing printed with said given orientation on one
surface of said board spaced from and extending outwardly in one
direction from an end of one conductor of said distribution
network,
a first normally non-conducting switching diode interconnecting
adjacent ends of said first wing and said one conductor of said
distribution network,
a second dipole wing printed with said given orientation on said
one surface of said board spaced from and extending outwardly in a
direction opposite to said one direction from said end of said one
conductor of said distribution network,
a second normally non-conducting switching diode interconnecting
adjacent ends of said second wing and said one conductor of said
distribution network,
a third dipole wing printed on the other surface of said board in a
superimposed relation with said first wing,
a third normally non-conducting switching diode interconnecting
adjacent ends of said third wing and the other conductor of said
distribution network,
a fourth dipole wing printed on said other surface of said board in
a superimposed relation with said second wing, and
a fourth normally non-conducting switching diode interconnecting
adjacent ends of said fourth wing and said other conductor of said
distribution network; and
said phase shifting arrangement further includes
a second switching arrangement connected between said source and
each of said first and fourth wings to render each of said first
and fourth diodes conductive to connect said first and fourth wings
to said distribution network to provide energy flow in said N
elements in a first direction, and
a third switching arrangement connected between said source and
each of said second and third wings to render each of said second
and third diodes conductive to connect said second and third wings
to said distribution network to provide energy flow in said N
elements in a second direction opposite to said first
direction,
said second and third switching arrangements being non-coincidently
operated.
6. An antenna array according to claim 5, wherein
said second switching arrangement is connected to a low impedance
point of each of said first and fourth wings; and
said third switching arrangement is connected to a low impedance
point of each of said second and third wings.
7. An antenna array according to claim 6, wherein
each of said first, second, third and fourth diodes is a PIN
diode.
8. An antenna array according to claim 7, wherein
each of said PIN diodes are parallel to said board.
9. An antenna array according to claim 8, wherein
said N elements are equal to an even integer symmetrically disposed
on said board; and
said distribution network is disposed on said board extending
radially in two directions from a predetermined point and connected
to said N elements; and
further including
a combined balun and power divider coupled to said distribution
network including
a coaxial transmission line disposed perpendicular to said board
adjacent said predetermined point, said coaxial line having an
outer conductor and a center conductor extending through said board
to one surface thereof,
a first strip conductor disposed on said one surface of said board
connected directly to and extending radially in two directions from
said center conductor for connection to the inputs of said
distribution network, said first conductor having a given width,
and
a second strip conductor disposed on the other surface of said
board in a superimposed relation with said first conductor and
connected between said outer conductor and said inputs of said
distribution network, said second conductor having a width greater
than said given width.
10. An antenna array according to claim 2, wherein
said phase shifting arrangement includes
a plurality of said one phase shifter connected in a series
relationship, and
said first switching arrangement is connected between said source
and each of said four diodes of each of said plurality of said one
phase shifter to control said phase in predetermined phase shift
steps.
11. An antenna array according to claim 10, wherein
each of said four diodes of each of said plurality of said one
phase shifter is a PIN diode.
12. An antenna array according to claim 11, wherein
each of said PIN diodes is parallel to said board.
13. An antenna array according to claim 12, wherein
said N elements are equal to an even integer symmetrically disposed
on said board; and
said distribution network is disposed on said board extending
radially in two directions from a predetermined point and connected
to said N elements; and
further including
a combined balun and power divider coupled to said distribution
network including
a coaxial transmission line disposed perpendicular to said board
adjacent said predetermined point, said coaxial line having an
outer conductor and a center conductor extending through said board
to one surface thereof,
a first strip conductor disposed on said one surface of said board
connected directly to and extending radially in two directions from
said center conductor for connection to the inputs of said
distribution network, said first conductor having a given width,
and
a second strip conductor disposed on the other surface of said
board in a superimposed relation with said first conductor and
connected between said outer conductor and said inputs of said
distribution network, said second conductor having a width greater
than said given width.
14. An antenna array according to claim 10, wherein
each of said N elements includes
a first dipole wing printed with said given orientation on one
surface of said board spaced from and extending outwardly in one
direction from an end of one conductor of said distribution
network,
a first normally non-conducting switching diode interconnecting
adjacent ends of said first wing and said one conductor of said
distribution network,
a second dipole wing printed with said given orientation on said
one surface of said board spaced from and extending outwardly in a
direction opposite to said one direction from said end of said one
conductor of said distribution network,
a second normally non-conducting switching diode interconnecting
adjacent ends of said second wing and said one conductor of said
distribution network,
a third dipole wing printed on the other surface of said board in a
superimposed relation with said first wing,
a third normally non-conducting switching diode interconnecting
adjacent ends of said third wing and the other conductor of said
distribution network,
a fourth dipole wing printed on said other surface of said board in
a superimposed relation with said second wing, and
a fourth normally non-conducting switching diode interconnecting
adjacent ends of said fourth wing and said other conductor of said
distribution network; and
said phase shifting arrangement further includes
a second switching arrangement connected between said source and
each of said first and fourth wings to render each of said first
and fourth diodes conductive to connect said first and fourth wings
to said distribution network to provide energy flow in said N
elements in a first direction, and
a third switching arrangement connected between said source and
each of said second and third wings to render each of said second
and third diodes conductive to connect said second and third wings
to said distribution network to provide energy flow in said N
elements in a second direction opposite to said first
direction,
said second and third switching arrangements being noncoincidently
operated.
15. An antenna array according to claim 14, wherein
each of said first, second, third and fourth diodes is a PIN
diode.
16. An antenna array according to claim 15, wherein
each of said PIN diodes are parallel to said board.
17. An antenna array according to claim 16, wherein
said second switching arrangement is connected to a low impedance
point of each of said first and fourth wings; and
said third switching arrangement is connected to a low impedance
point of each of said second and third wings.
18. An antenna according to claim 17, wherein
said N elements are equal to an even integer symmetrically disposed
on said board; and
said distribution network is disposed on said board extending
radially in two directions from a predetermined point and connected
to said N elements; and
further including
a combined balun and power divider coupled to said distribution
network including
a coaxial transmission line disposed perpendicular to said board
adjacent said predetermined point, said coaxial line having an
outer conductor and a center conductor extending through said board
to one surface thereof,
a first strip conductor disposed on said one surface of said board
connected directly to and extending radially in two directions from
said center conductor for connection to the inputs of said
distribution network, said first conductor having a given width,
and
a second strip conductor disposed on the other surface of said
board in a superimposed relation with said first conductor and
connected between said outer conductor and said inputs of said
distribution network, said second conductor having a width greater
than said given width.
19. An antenna array according to claim 1, wherein
each of said N elements includes
a first dipole wing printed with said given orientation on one
surface of said board spaced from and extending outwardly in one
direction from an end of one conductor of said distribution
network,
a first normally non-conducting switching diode interconnecting
adjacent ends of said first wing and said one conductor of said
distribution network,
a second dipole wing printed with said given orientation on said
one surface of said board spaced from and extending outwardly in a
direction opposite to said one direction from said end of said one
conductor of said distribution network,
a second normally non-conducting switching diode interconnecting
adjacent ends of said second wing and said one conductor of said
distribution network,
a third dipole wing printed on the other surface of said board in a
superimposed relation with said first wing,
a third normally non-conducting switching diode interconnecting
adjacent ends of said third wing and the other conductor of said
distribution network,
a fourth dipole wing printed on said other surface of said board in
a superimposed relation with said second wing, and
a fourth normally non-conducting switching diode interconnecting
adjacent ends of said fourth wing and said other conductor of said
distribution network; and
said phase shifting arrangement includes
a source of switching voltage,
a first switching arrangement connected between said source and
each of said first and fourth wings to render each of said first
and fourth diodes conductive to connect said first and fourth wings
to said distribution network to provide energy flow in said N
elements in a first direction, and
a second switching arrangement connected between said source and
each of said second and third wings to render each of said second
and third diodes conductive to connect said second and third wings
to said distribution network to provide energy flow in said N
elements in a second direction opposite to said first
direction,
said first and second switching arrangements being noncoincidently
operated.
20. An antenna array according to claim 19, wherein
said first, second, third and fourth diodes is a PIN diode.
21. An antenna array according to claim 20, wherein
each of said PIN diodes is parallel to said board.
22. An antenna according to claim 21, wherein
said first switching arrangement is connected to a low impedance
point of each of said first and fourth wings; and
said second switching arrangement is connected to a low impedance
point of each of said second and third wings.
23. An antenna array according to claim 22, wherein
said N elements are equal to an even integer symmetrically disposed
on said board; and
said distribution network is disposed on said board extending
radially in two directions from a predetermined point and connected
to said N elements; and
further including
a combined balun and power divider coupled to said distribution
network including
a coaxial transmission line disposed perpendicular to said board
adjacent said predetermined point, said coaxial line having an
outer conductor and a center conductor extending through said board
to one surface thereof,
a first strip conductor disposed on said one surface of said board
connected directly to and extending radially in two directions from
said center conductor for connection to the inputs of said
distribution network, said first conductor having a given width,
and
a second strip conductor disposed on the other surface of said
board in a superimposed relation with said first conductor and
connected between said outer conductor and said inputs of said
distribution network, said second conductor having a width greater
than said given width.
24. A combined mat-strip dipole element and phase inverter
comprising:
a first dipole wing printed with a given orientation on one surface
of a printed circuit board spaced from and extending outwardly in
one direction from one end of one conductor of a mat-strip power
distribution network carried by said board;
a first normally non-conducting switching diode interconnecting
adjacent ends of said first wing and said one conductor of said
distribution network;
a second dipole wing printed with said given orientation on said
one surface of said board spaced from and extending outwardly in a
direction opposite to said one direction from said end of said one
conductor of said distribution network;
a second normally non-conducting switching diode interconnecting
adjacent ends of said second wing and said one conductor of said
distribution network;
a third dipole wing printed on the other surface of said board in a
superimposed relation with said first wing;
a third normally non-conducting switching diode interconnecting
adjacent ends of said third wing and the other conductor of said
distribution network; and
a fourth dipole wing printed on said other surface of said first
board in a superimposed relation with said second wing;
a fourth normally non-conducting switching diode interconnecting
adjacent ends of said fourth wing and said other conductor of said
distribution network;
a source of switching voltage;
a first switching arrangement connected between said source and
each of said first and fourth wings to render each of said first
and fourth diodes conductive to connect said first and fourth wings
to said distribution network to provide energy flow in said dipole
element in a first direction; and
a second switching arrangement connected between said source and
each of said second and third wings to render each of said second
and third diodes conductive to connect said second and third wings
to said distribution network to provide energy flow in said dipole
element in a second direction opposite to said first direction;
said first and second switching arrangements being non-coincidently
operated.
25. An arrangement according to claim 24, wherein
each of said first, second, third and fourth diodes is a PIN
diode.
26. An arrangement according to claim 25, wherein
each of said PIN diodes is parallel to said board.
27. An arrangement according to claim 26, wherein
said first switching arrangement is connected to a low impedance
point of each of said first and fourth wings; and
said second switching arrangement is connected to a low impedance
point of each of said second and third wings.
Description
BACKGROUND OF THE INVENTION
This invention relates to linearly polarized phased antenna arrays
and more particularly to a linearly polarized phased antenna array
employing mat-strip and printed circuit techniques.
The term "mat-strip" as employed herein is defined as a photo
etched or printed balanced transmission line printed on opposite
surfaces of a printed circuit (PC) board in such a manner that both
conductors are superimposed, are equal in width and are equal in
length. This is in contrast to a stripline transmission line which
is an unbalanced transmission line requiring two ground planes one
above and one below a single conductive strip and to a microstrip
transmission line which consists of a conductive strip above a
ground plane having a much greater width than the conductive strip.
A microstrip transmission line is analogous to a two wire line in
which one of the wires is represented by the image in the ground
plane of the wire that is physically present. Another way of
expressing what a mat-strip transmission line is is to state that
it is a balanced transmission line in which the image wire of a
microstrip transmission line has materialized and the ground plane
of a microstrip transmission line has been removed.
An antenna dipole element in mat-strip technique consists of one
half of the dipole element (one wing) being disposed on one surface
of the PC board having one end thereof connected to one conductor
of a mat-strip transmission line and the other half of the dipole
elements (the other wing) being disposed on the other surface of
the PC board having one end thereof connected to the other
conductor of the same mat-strip transmission line. A ground plane
is associated with the dipole elements (it has no function in the
mat-strip transmission line) to insure that the radiation from the
dipole element is from one surface of the PC board, namely, the
surface of the PC board removed from the ground plane.
The realization of high performing, light weight, economical
communication, radar or the like phased antenna arrays has been
hampered by narrow band lossy phase shifters, complex feed
networks, and heavy expensive components. These problems are
compounded as the antenna array becomes large and has resulted in
the almost exclusive use of fixed beam antennas in tactical
microwave communication, radar and the like systems. A typical
example is a jeep mounted antenna which affords approximately 33 db
(decibel) gain while operating in the 7.25 to 8.4 gigahertz (GHz)
communication band. Two configurations of this fixed beam antenna
have been constructed, namely, a parabolic reflector employing a
dual circularly polarized feed, and a dual circularly polarized
array. It is feasible to build either with its mount to weigh less
than 50 pounds. The cost for either is less than $1,000 with a
manually pointed mount. A comparable phased array antenna would
weigh more than 150 pounds when built by conventional
construction.
The cost of the phase shifters and driver circuits along can vary
from $3,000 for one dimensional steering to $90,000 for two
dimensional steering. In addition, an antenna mount would still be
required to obtain 360.degree. coverage for azimuth.
Printed circuit phase shifters using PIN diodes have been employed
in various designs to obtain minimum weight, broad band operation
and low cost. These have several major drawbacks. First, the loss
can be as high as 3db. Thus, the antenna efficiency is limited to
50 percent or less. The resulting antenna noise temperatures are
more than 150.degree. K (kelvin) even at zenith operation. This is
to be compared with noise temperatures under 50.degree.K for fixed
beam antennas. A second drawback to these prior art designs is that
they are difficult to integrate into a dual circularly polarized
system. The phase shifters cannot be integrated directly in the
array structure in most cases, but must be connected by external
cables, such as miniature coaxial lines. Such connections present
frequency sensitive phase shifts of their own and also contribute
to the loss of the system. A third disadvantage is that the cost of
these devices in quantities of 100 or more is still greater than
$100 per unit. This cost stems from the expensive fabrication.
techniques and the large number of components required per assembly
and, in addition, they require a fair amount of bench
alignment.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a mat-strip
linearly polarized phased antenna array that overcomes the
disadvantages of the prior art mentioned hereinabove and also which
is capable of being incorporated in a dual circularly polarized
phase antenna array such as disclosed in a copending application of
J. C. Ranghelli and E. J. Perrotti, Ser. No. 382,619, filed July
25, 1973 assigned to International Telephone and Telegraph Corp.
whose disclosure is incorporated herein by reference.
Another object of the present invention is to provide a mat-strip
linearly polarized phased antenna array incorporating the
techniques of U.S. Pat. No. 3,681,769 issued to E. J. Perrotti, J.
C. Ranghelli and R. A. Felsenheld and assigned to International
Telephone and Telegraph Corporation and in particular the
techniques of the above cited patent relative to one of the
mat-strip linearly polarized arrays and its associated ground
plane. The disclosure of the above cited patent is incorporated
herein by reference.
A further object of the present invention is to provide a mat-strip
loaded line type phase shifter for incorporation in a mat-strip
power division distribution network for the mat-strip dipole
elements wherein the mat-strip phase shifter is employed singly or
a plurality of these phase shifters are coupled in series relation
in the distribution network to provide stepped radio frequency
phase shifts in the distribution network.
Still a further object of the present invention is to provide a
mat-strip linearly polarized phased antenna array incorporating a
combined mat-strip dipole element and phase inverted either by
itself or in combination with the above-mentioned loaded line type
mat-strip phase shifters.
A feature of the present invention is the provision of an antenna
array comprising: N linearly polarized mat-strip dipole elements
disposed on a printed circuit board, each of the N-elements having
a given orientation, where N is an integer including one; a ground
plane superimposed relative to and associated with the N elements;
a mat-strip power distribution network disposed on the board
coupled to the N elements; the N elements, the ground plane and the
distribution network cooperating to produce a linearly polarized
antenna beam; and a phase shifting arrangement selectively coupled
to the distribution network to control the antenna beam to have
different selected angular directions, at least a portion of the
phase shifting arrangement being carried by the board.
Another feature of the present invention is the provision of at
least one phase shifter including a one quarter wavelength
mat-strip impedance transformer disposed in a mat-strip power
distribution network, the transformer and the distribution network
being carried by a printed circuit board, a first shunt mat-strip
transmission line carried by the board and extending perpendicular
from one end of the transformer, a second shunt mat-strip
transmission line carried by the board and extending perpendicular
from the other end of the transformer parallel to the first shunt
transmission line, four normally non-conducting switching diodes
carried by the board, each of the four diodes being connected to an
end of a different one of the conductors of the first and second
shunt transmission lines, and four radio frequency ground
terminating and direct current biasing printed circuit pads carried
by the board, each of the four pads being connected to a different
one of the four diodes; a source of switching voltage; and a
switching arrangement connected between the source and each of the
four pads to render the four diodes conductive to radio frequency
ground the first and second shunt transmission lines by the four
pads to provide a predetermined amount of radio frequency phase
shift in the distribution network.
A further feature of the present invention is the provision of a
mat-strip phase shifting arrangement comprising: a plurality of
cascade connected phase shifters disposed in a mat-strip power
distribution network carried by a printed circuit board, each of
the phase shifters including a one quarter wavelength mat-strip
impedance transformer disposed in the distribution network and
carried by the board, a first shunt mat-strip transmission line
carried by the board and extending perpendicular from one end of
the transformer, a second shunt mat-strip transmission line carried
by the board and extending perpendicular from the other end of the
transformer parallel to the first shunt transmission line, four
normally non-conducting switching diodes carried by the board, each
of the four diodes being connected to an end of a different one of
the conductors of the first and second shunt transmission lines,
and fourth radio frequency ground terminating and direct current
biasing printed circuit pads carried by the board, each of the four
pads being connected to a different one of the four diodes; a
source of switching voltage; and a switching arrangement connected
between the source and each of the four pads of each of the
plurality of the phase shifters to render each of the four diodes
of selected ones of the plurality of phase shifters conductive to
radio frequency ground the first and second shunt transmission
lines by the four pads of the selected ones of the plurality of
phase shifters to provide predetermined steps of radio frequency
phase shift in the distribution network.
Still a further feature of the present invention is the provision
of a combined mat-strip dipole element and phase inverter
comprising: a first dipole wing printed with a given orientation on
one surface of a printed circuit board spaced from and extending
outwardly in one direction from one end of one conductor of a
mat-strip power distribution network carried by the board; a first
normally non-conducting switching diode interconnecting adjacent
ends of the first wing and the one conductor of the distribution
network; a second dipole wing printed with the given orientation on
the one surface of the board spaced from and extending outwardly in
a direction opposite to the one direction from the end of the one
conductor of the distribution network; a second normally
non-conducting switching diode interconnecting adjacent ends of the
second wing and the one conductor of the distribution network; a
third dipole wing printed on the other surface of the board in a
superimposed relation with the first wing; a third normally
non-conducting switching diode interconnecting adjacent ends of the
third wing and the other conductor of the distribution network; and
a fourth dipole wing printed on the other surface of the first
board in a superimposed relation with the second wing; a fourth
normally non-conducting switching diode interconnecting adjacent
ends of the fourth wing and the other conductor of the distribution
network; a source of switching voltage; a first switching
arrangement connected between the source and each of the first and
fourth wings to render each of the first and fourth diodes
conductive to connect the first and fourth wings to the
distribution network to provide energy flow in the dipole element
in a first direction; and a second switching arrangement connected
between the source and each of the second and third wings to render
each of the second and third diodes conductive to connect the
second and third wings to the distribution network to provide
energy flow in the dipole element in a second direction opposite to
the first direction; said first and second switching arrangements
being non-coincidently operated.
BRIEF DESCRIPTION OF THE DRAWING
Above-mentioned and other features and objects of this invention
will become more apparent by reference to the following description
taken in conjunction with the accompanying drawing, in which:
FIG. 1 is a plane view of one embodiment of a mat-strip linearly
polarized phased antenna array in accordance with the principles of
the present invention;
FIG. 2 is a cross section of FIG. 1 taken along line 2--2;
FIG. 3 is a cross sectional view of FIG. 1 taken along line
3--3;
FIG. 4 is a cross sectional view of FIG. 1 taken along line
4--4;
FIG. 4A is a partial schematic diagram of one of the phase shifters
of FIG. 1;
FIG. 5 is a plane view of another embodiment of a printed circuit
mat-strip linearly polarized phased antenna array in accordance
with the principles of the present invention; and
FIG. 6 is a partial cross sectional view of FIG. 5 taken along line
6--6.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1-4 there is illustrated therein a PC mat-strip
linearly polarized array and associated ground plane to enable the
achievement of a linearly polarized antenna beam which may be
steered to be directed at different angles in accordance with the
principles of this invention. The antenna array includes a
dielectric sheet 1 having disposed thereon by PC techniques a
mat-strip dipole antenna element 2 in the form of two dipole wings
3 and 4 where wing 3 is disposed on the lower surface 5 of sheet 1
and wing 4 is disposed on the upper surface 6 of sheet 1. As
illustrated, this array includes a plurality of dipole elements 2
interconnected for symmetrical power feed by mat-strip type
balanced power division transmission line distribution network 7
including various balanced mat-strip type conductors 8 and 9 to
provide power division and parallel feeding of the groups of dipole
elements. The linearly polarized dipole element array on sheet 1 is
symmetrical in all quadrants as are their distribution networks
7.
It should be noted that as in the above cited patent the mat-strip
conductors of the balanced transmission line distribution network 7
are formed by two strip conductors, one strip conductor being
disposed on surface 5 of sheet 1 and the other strip conductor
being superimposed with respect to said one strip conductor on
surface 6 of sheet 1.
The ground plane for the linearly polarized phased antenna array on
sheet 1 is provided by the bottom of the metallic housing 10 which
is spaced from wings 4 of sheet 1 by one quarter wavelength of the
operating frequency of the array.
It will be noted that networks 7 include in each of the strip
conductors decreased width portions and increased width portions at
the branching locations thereof. The decreased width portions and
the increased width portions are each one quarter wavelength long
at the operating frequency of the antenna array to provide a
reflectionless power transformation between the transmission line
sections themselves and from the transmission line sections to the
dipole elements 2.
The spacing between sheet 1 and ground plane 10 is maintained to
the appropriate predetermined value by employment of bolts 11
extending through ground plane 10 and sheet 1 with appropriate
length spacers or standoffs 12 disposed thereon to maintain the
desired spacing of the stacked arrangement. In addition to these
bolts and spacers, the coaxial transmission line portion of the
combined balun and power dividing arrangement, to be described
hereinbelow, also cooperate in maintaining the desired separation
of the stacked members. This separation can also be maintained by a
frame structure made of low density foam. This would lend itself to
a bonded sandwich construction.
Distribution networks 7 are symmetrically fed from a combined balun
and power divider 13 which is of the double ended balun type.
Energy is coupled to the array on sheet 1 by waveguide 14 to which
is coupled a transmitter or receiver 16. The unbalanced to balanced
transformation is obtained by the combined balun and power divider
13 which includes coaxial transmission line 17 having inner
conductor 18 extending through sheet 1 for electrical contact with
strip conductor 19. Conductor 19 extends radially in two directions
from center conductor 18 with the ends thereof being respectively
connected to the inputs to networks 7. The outer conductor 20 of
coaxial transmission line 17 is physically supported and in
electrical contact with strip conductor 21 having the configuration
illustrated in FIG. 1 which obviously is wider than the width of
conductor 19 and the conductors forming networks 7. Thus, the
combined balun and power divider provides a direct transition from
waveguide 14 to the balanced mat-strip networks 7. It also provides
a positive mechanical connection to the balanced mat-strip line of
the printed antenna array without the use of solder joints and, in
addition, and more importantly provides an immediate power division
with a relatively large heat sink formed by conductor 21 thereby
enabling the feeding of greater power into networks 7.
The conductors of networks 7 and dipole elements 2 are composed of
conductive material, such as copper, copper clad material or the
like. Dielectric sheet 1 is composed of a low loss dielectric, such
as Tellite, Rexilite, Z-Tron and Duroid. The latter two low loss
dielectric materials are also high temperature materials and, of
course, would be particularly applicable to the present invention
under high temperature conditions.
To provide the desired phase shift for antenna beam steering, FIG.
1 illustrates one mat-strip phase shifter of the loaded line type
identified as phase shifter 22. Phase shifter 22 is a complete
mat-strip type phase shifter except for switching diodes, such as
PIN diodes 23, 24 and similar superimposed diodes, such as PIN
diode 25 which is superimposed with respect to PIN diode 23. Diodes
23 and 24 and the similar superimposed diodes are all parallel to
sheet 1. Phase shifter 22 includes a mat-strip impedance
transformer having a one quarter wavelength at the operating
frequency of the array to which is coupled a pair of parallel shunt
mat-strip transmission lines 27 and 28 having a length of one
eighth wavelength at the operating frequency. Each of the shunt
mat-strip lines include a pair of superimposed conductors such as
conductors 29 and 30 (FIG. 4). Diodes 23 and 24 and their
superimposed diodes are coupled to a different one of each one of
the conductors of the shunt transmission lines 27 and 28 each of
which has coupled thereto a different one of the conductors of
printed circuit type radio frequency grounding or shorting and
direct current biasing pads 31 and 32, each of which have a length
of one quarter wavelength at the operating frequency. Each of the
pads 31 and 32 include two superimposed conductors, such as
conductors 33 and 34 (FIG. 4). A direct current bias voltage is
supplied from switching voltage source 35 through switch
arrangements 36 and 37 as desired to render diodes 23 and 24 and
their superimposed diodes conductive to connect the conductors of
pads 31 and 32 to the conductors of shunt lines 27 and 28. When
diodes 23 and 24 and their superimposed diodes are conductive a
radio frequency ground or short circuit is provided by each of the
conductors of the pads 31 and 32. Bypass capacitors 38 passes a
direct current biasing voltage conductor thereto to pads 31 and 32.
When a radio frequency ground or short circuit terminates shunt
transmission lines 27 and 28 a 45.degree. radio frequency phase
shift is provided in the distribution networks 7 for the radio
frequency energy coupled to elements 2 thereby enabling control of
the angular direction of the antenna beam.
As described above the loaded line type phase shifter 22 is in
mat-strip form with no inductors, capacitors or coaxial connectors
required. The terminating circuit, the superimposed conductors of
pads 31 and 32 for the diodes provide simultaneously a radio
frequency short circuit and an arrangement to provide direct
current voltage for biasing the diodes in such a manner that a
physical arrangement is provided to install the diodes in a
parallel relation to dielectric sheet 1. This eliminates machining
operation associated with through-the-substrate mounting of the
diodes. It will be noted that through the cooperation of the
switching diodes (PIN diodes) 23 and 24 and their superimposed
diodes a double pole switching arrangement is provided which
prevents unbalanced currents.
The well known operation of each of the loaded line type phase
shifters 22 will now be described. The mat-strip transmission lines
27 and 28 are one eighth wavelength long at the operating frequency
and are effectively stubs of high impedance having superimposed
conductors 29, 30 and 29', 30', respectively, as illustrated in
FIG. 4A. The switching or PIN diodes 24 and its superimposed PIN
diode 25 and PIN or switching diode 24' and its superimposed PIN
diode 25' are coupled respectively to conductors 29, 30, 29' and
30' and to their associated low impedance pads 31 and 32 formed by
superimposed conductors 33, 34 and 33', 34', respectively, with
each of these pad conductors having a length at the operating
frequency of one quarter wavelength. These low impedance pads 31
and 32 serve two purposes. The first is to provide a radio
frequency short circuit termination for the diodes and the second
is to provide a direct current open circuit suitable for biasing
the diodes. This construction, as mentioned above, provides a means
to install the switching diodes planar to the substrate thus
eliminating machining operations associated with
through-the-substrate mounting of diodes. It should be noted that
identical elements are required above and below the dielectric
substrate because a mat-strip transmission line or other mat-strip
components, such as a loaded line type phase shifter, are balanced
devices and will radiate if an unbalance is introduced by not
duplicating the elements both above and below the substrate.
As seen in FIG. 4A the loaded line phase shifter consists of a pair
of one eighth wavelength long shunt transmission lines 27 and 28
connected across distribution network 7 with a quarter wavelength
spacing between shunt lines 27 and 28. Shunt transmission lines 27
and 28 are terminated in radio frequency diodes switches which are
driven synchronously with the diodes being terminated in pads 31
and 32. The loaded line phase shifter produces a differential
transmission phase shift between the open and short circuit switch
states of the diodes by respectively loading the transmission path
of network 7 with capacitive and inductive discontinuities. When
the distribution network 7 is capacitively loaded the energy
propagated there along is retarded by a phase shift of (-
.theta./2) while inductive loading of the distribution network 7
produces a phase advance of (+ .theta./2). In either state of the
diodes, the spacing and impedances of the interconnecting lines
result in a matched circuit.
It should be noted that the phase shifter under normal use is
either in a reverse biased or forward biased state. The phase
shifter is not switched in or out of the circuit nor in or out of
operation. With many switching diodes if all bias is removed, the
diode characteristics are very close to those of the reverse bias
state. Under these conditions, and in a multielement phased array,
all radiating elements would have similar phase shifts. If there
are no unequal line lengths in the power distribution network 7
feeding the elements, which in most mat-strip designs is the case,
the antenna would have a uniform (constant) phase distribution and
the beam would point broadside.
Referring to FIG. 5 there is disclosed therein another linearly
polarized mat-strip phased antenna array which incorporates power
division distribution networks 7' similar to networks 7 described
with respect to FIG. 1 and also a combined balun and power divider
13' similar to the combined balun and power divider 13 described
with respect to FIGS. 1 and 2. In the linearly polarized phased
antenna array of FIG. 5 the dipole elements 2', which may be
substituted for dipole elements 2 of FIG. 1, include a dipole wing
39 and a dipole wing 40 printed on one surface of sheet 1' and two
dipole wings 41 and 42 (FIG. 6) printed on the other surface of
sheet 1'. Dipole wings 39 and 40 are connected to conductor 43 of
distribution networks 7' by switching diodes, such as PIN diodes 44
and 45 which are parallel to sheet 1. Dipole wings 41 and 42 are
coupled to conductor 46 of network 7' by PIN diodes 47 and 48 which
are also parallel to sheet 1. Through means of a switching voltage
source and switching arrangements similar to source 35 and
switching arrangements 36 and 37 (FIG. 2) it is possible to provide
combined mat-strip dipole elements and a phase inverter, in other
words, a 180.degree. phase shifter. This is accomplished by moving
switches of the switching arrangement such that a switching voltage
is coupled to wings 40 and 41 to render diodes 45 and 47 conductive
thereby connecting wing 40 to conductor 43 and wing 41 to conductor
46. Having these two dipole wings active there is energy flowing in
a first direction through this dipole element. When the switching
voltage is removed from wings 40 and 41 diodes 45 and 47 are
rendered non-conductive and when a switching voltage is applied to
wings 39 and 42 diodes 44 and 48 are rendered conductive thereby
connecting wing 39 to conductor 43 and wing 42 to conductor 46.
With this orientation of the wings of the dipole elements energy
will be propagated through the dipole elements in a direction
opposite to that when dipole wings 40 and 41 were active. Thus,
this technique of providing a mat-strip dipole element and a
mat-strip phase inverter includes the printing of two dipoles in
mat-strip form which are overlayed to radiate "through" each other
according to which dipole is made active (connected to the
distribution network) and which is made inactive (disconnected from
the distribution network). The diodes are connected to the base or
low impedance point of each dipole wing to provide radio frequency
switching of the dipole wings to the feed lines. As pointed out
hereinabove the 180.degree. phase shift is obtained by inverting
the dipole through radio frequency switching of the dipole wings
such that a given wire or conductor of the mat-strip distribution
network is made to switch from a dipole wing located spatially
"above" the wire to one located spatially "below" that wire and
concurrently the second wire is switched in a reverse fashion. The
technique of biasing or switching each diode with a direct current
wire located at the dipole base, the low impedance point, with this
wire being perpendicular to the radiated field does not interfere
with the radiated field. The direct current wire incorporates a
bypass capacitor where the wire passes through the metallic housing
to provide a radio frequency terminating short circuit. This
technique reduces the interference of the biasing or switching
circuit on the radiated pattern and the dipole impedance.
It will be noted that each branch of network 7' feeding a dipole
element 2' includes therein three mat-strip phase shifters 22, 22a
and 22b which are identical to the mat-strip phase shifter 22
described with respect to FIGS. 1, 3 and 4. With this arrangement
it is possible to phase the radio frequency in network 7'
45.degree. when phase shifter 22 is inserted into 7', 90.degree.
when phase shifters 22 and 22a are switched into network 7' and
135.degree. when phase shifter 22b is switched into network 7. In
addition, the phase inverting arrangement provided for dipole
elements 2' can be used singly or additively with phase shifters 22
to provide other descrete steps of phase shifts to provide the
desired steering or angular direction of the radiated antenna
beam.
In accordance with the principles of the present invention a
linearly polarized phased antenna array is provided in mat-strip
form to provide a compact, flat, light weight array fed from a
single input. In this arrangement the total phase shifter losses
have been cut to less than half of those for previously employed
printed circuit designs (1.25 db total). The bandwidth of operation
extends through the 7.25 to 8.4 GHz while the total 3 sigma phase
error has been limited to 9.1.degree. (or approximately 3.degree.
for one sigma) for all states. The phase shifting arrangement
including both the inverter arrangement associated with dipole
elements 2' and the phase shifters 22 are completely integrated as
part of the printed circuit antenna structure and does not need
additional bench alignment since it is reproducible due to the PC
techniques employed. It is estimated that in quantities of several
hundred, the phase shifter cost can be made to approach $30 per
unit with this cost being mostly a function of the per unit cost of
the PIN diodes.
While we have described above the principles of our invention in
connection with specific apparatus it is to be clearly understood
that this description is made only by way of example and not as a
limition to the scope of our invention as set forth in the objects
thereof and in the accompanying claims.
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