U.S. patent number 3,569,973 [Application Number 04/821,207] was granted by the patent office on 1971-03-09 for constrained lens type antenna.
This patent grant is currently assigned to North American Rockwell Corporation. Invention is credited to Charles T. Brumbaugh, Jr, Jack W. Preston, Jerry L. McFarland, Richard W. Wesley.
United States Patent |
3,569,973 |
|
March 9, 1971 |
CONSTRAINED LENS TYPE ANTENNA
Abstract
A constrained lens-type antenna including a lens having a
controlled aperture phase distribution and utilizing stripline
circuitry. The lens is formed of a plurality of mutually parallel
stripline assemblies, each assembly comprising a pair of mutually
nested dielectric U-channels sandwiching a dielectric slipsheet
having a plurality of deposited electrically conductive lines of
selected lengths as discrete delay elements. The outer surface of
the opposing walls of the U-shaped channel assembly include
microwave ports, each being electromagnetically coupled to an
associated terminus of a mutually exclusive one of said delay
elements, the ports in one of the opposing walls being exposed to a
feed horn, serve as feed ports, while the ports in the other of the
opposing walls serve as radiating ports. The novel use of stripline
circuitry provides a lens assembly of minimum bulk and weight while
also having improved geometrical tolerances and performance.
Inventors: |
Charles T. Brumbaugh, Jr
(Norwalk, CA), Jerry L. McFarland (Fullerton, CA), Jack
W. Preston (Placentia, CA), Richard W. Wesley (Yorba
Linda, CA) |
Assignee: |
North American Rockwell
Corporation (N/A)
|
Family
ID: |
25232799 |
Appl.
No.: |
04/821,207 |
Filed: |
May 2, 1969 |
Current U.S.
Class: |
343/753; 123/80D;
333/238; 343/853; 343/771 |
Current CPC
Class: |
H01Q
15/02 (20130101); H01Q 19/062 (20130101) |
Current International
Class: |
H01Q
15/00 (20060101); H01Q 19/06 (20060101); H01Q
15/02 (20060101); H01Q 19/00 (20060101); H01g
019/06 (); H01g 021/00 () |
Field of
Search: |
;343/754,755,854,753,771,853 ;333/31,84 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Eli Lieberman
Attorney, Agent or Firm: William R. Lane L. Lee Humphries
Rolf M. Pitts
Claims
1. A constrained lens-type antenna comprising a lens having a
controlled aperture phase distribution and including in combination
a plurality of discrete and mutually parallel laminated stripline
assemblies, each assembly comprising: a laminated pair of
dielectric plates; a dielectric slipsheet having a plurality of
electrically conductive delay lines of selected lengths deposited
thereon, said slipsheet being sandwiched between said plates of
said laminated pair; and opposing faces of said laminated assembly
being clad with an electrically conductive coating, at least one of
said faces having a plurality of microwave ports formed by
apertures in said coating, each aperture being in registry with an
associated terminus of a mutually exclusive one of said delay lines
for effecting electromagnetic coupling between each port
2. The device of claim 1 in which said apertures in said one
coating form two parallel lineal arrays of ports, each array being
electromagnetically
3. The device of claim 1 in which said apertures in one of said
coatings form two lineal arrays of ports, each array parallel to
and proximate opposite edges of said laminated assembly and being
electromagnetically coupled to opposite terminii of said delay
lines, each said assembly being formed as a U-shaped channel, the
outer surface of the opposing walls of
4. The device of claim 1 in which said apertures are located in
each said coating, forming a lineal array of ports in a respective
one of said plates, arrays on opposite faces of said laminated pair
being
5. The device of claim 1 in which said apertures are located in
each of said coatings, forming a lineal array of ports parallel to
and proximate an opposite edge of said laminated assembly and being
electromagnetically
6. A constrained lens-type antenna comprising a lens having a
controlled phase aperture distribution and including in
combination: a plurality of discrete and mutually parallel-stacked
U-shaped channel stripline assemblies; each assembly comprising: a
pair of mutually nested rigid dielectric U-channels sandwiching a
dielectric slipsheet having a plurality of electrically conductive
coplanar lines of selected lengths as discrete delay elements; the
outer surface of the opposing walls of the outer U-shaped channel
including microwave windows as ports formed by conductive loops,
each window being in registry with an associated terminus of a
mutually exclusive one of said delay elements, the inside surface
of the inner U-shaped channel being electrically conductively
coated; and a plurality of shorting pins formed through opposing
walls of said assembly, the locus of which pins define microwave
cavities for effecting electromagnetic coupling between each said
windows and an associated
7. A constrained lens-type antenna comprising a lens having a
controlled aperture phase distribution and including in combination
a plurality of discrete and mutually parallel stacked stripline
assemblies, each assembly comprising: a pair of mutually nested
rigid dielectric U-channels sandwiching a dielectric slipsheet
having a plurality of deposited electrically conductive coplanar
lines of selected lengths as discrete delay elements; the outer
surface of the opposing walls of the U-shaped channel assembly
including microwave ports, each being electromagnetically coupled
to an associated terminus of a mutually exclusive one of said delay
elements.
8. A constrained lens-type antenna comprising a lens having a
controlled aperture phase distribution and including in combination
a plurality of discrete and mutually parallel U-shaped channel
stripline assemblies, each assembly comprising; a pair of mutually
nested rigid dielectric U-channels; a dielectric slipsheet having a
plurality of electrically conductive delay lines of selected
lengths, said slipsheet being sandwiched between said nested
U-channels; the outer surface of the opposing walls of the outer
U-shaped channel including microwave ports formed by enclosed
conductive loops, each port being in registry with an associated
terminus of a mutually exclusive one of said delay lines, the
inside surface of the inner U-shaped channel being electrically
conductively coated; and opposing walls of said assembly including
microwave cavities for effecting electromagnetic coupling between
each said windows and an associated
9. A constrained lens-type antenna comprising a lens having a
controlled aperture phase distribution and including in combination
a shingled plurality of discrete and mutually parallel-laminated
stripline assemblies, each assembly comprising: a laminated pair of
dielectric plates; a dielectric slipsheet having a plurality of
electrically conductive delay lines of selected lengths deposited
thereon, said slipsheet being sandwiched between said plates of
said laminated pair; and opposing faces of said laminated assembly
being clad with an electrically conductive coating, each said face
having a plurality of microwave ports formed by apertures in said
coating, each aperture being in registry with an associated
terminus of a mutually exclusive one of said delay lines for
effecting electromagnetic coupling between each port and an
associated
10. The device of claim 9 in which said apertures in each said
coating form a lineal array of ports in a respective one of said
plates, arrays on opposite faces of said laminated pair being
electromagnetically coupled to
11. The device of claim 9 in which said apertures in each of said
coatings form a lineal array of ports parallel to and proximate an
opposite edge of said laminated assembly and being
electromagnetically coupled to opposite terminii of said delay
lines.
Description
Most radar system requirements demand that the antenna system be
capable of transmitting and receiving electromagnetic energy in a
number of different operational modes, in the most efficient manner
possible. In particular, it is often desired to obtain a high gain
pencil beam mode with extremely low sidelobes combined with special
functions such as ground map and four beam conical scan modes over
wide bandwidths, and to do this with the lightest and most compact
structure conceivable.
High gain antennas which exhibit very wide bandwidth
characteristics belong to a class known as true time delay
antennas. A true time delay antenna is one wherein the electrical
length from the input to every point in the radiating aperture
plane is a constant. These systems include reflectors, distributed
lenses, constrained lenses and corporate feed systems and others.
Of these, the reflector system is the most practical, wideband
lightweight antenna but it exhibits high sidelobes due to spillover
and aperture blockage. The other systems can be designed to yield
very low sidelobes and multimode operation but they all possess
weight and/or volume penalties, and in some cases include several
mechanical tolerance limitations. An example of a dish-type antenna
having a preselected or controlled phase aperture distribution is
described, for example, in U.S. Pat. No. 3,355,738 issued to J. A.
Algeo for Microwave Antenna Having a Controlled Phase
Distribution.
The term constrained lens relates to the prior art use of a
plurality of discrete transmission lines, each line having a
selected phase length, whereby the curved (approximately spherical)
wave front of a primary feed may be converted to a substantially
planar wave front of selected directivity. An advantage of such
type of lens over a dish or reflector-type lens is the avoidance of
aperture blockage caused by the feed, coupled with the ease of
controlling beam shape and sidelobes by adjustment of the
associated discrete elements, relative to the difficulties of
accurately shaping a dish or "spoiled parabola" to achieve a
selected aperture phase distribution.
The prior art of constrained lens antennas is limited to the use of
coaxial cables as discrete delay lines, each coupled to an
associated pair of microwave input and exit ports, thus forming a
large, dense and expensive assembly, which demonstrates performance
limitations or aperture phase distribution inaccuracies due to
tolerances in the electromechanical connections of the individual
coax sections and due to geometric variations in the shapes and
orientations of the loops formed by such coax sections.
By means of the concept of the subject invention, a lens is formed
by means of strip line assemblies, whereby the above-noted
shortcomings of prior art constrained lens antennas are
avoided.
In a preferred embodiment of the invention there is provided a
constrained lens-type antenna comprising a lens having a controlled
aperture phase distribution and adapted to cooperate with a
switchable feedhorn cluster for effecting selected antenna modes.
There is provided a plurality of discrete and mutually parallel
laminated strip line assemblies, each assembly comprising a
laminated pair of rigid dielectric plates. A dielectric slip sheet,
having a plurality of electrically conductive delay lines of
selected length deposited thereon, is sandwiched between the
dielectric plates of the laminated pair. Opposing faces of the
laminated assembly are clad with an electrically conductive
coating, at least one of said faces having a plurality of microwave
ports formed by apertures in the coating, each aperture being in
registry with an associated terminus of a mutually exclusive one of
said delay lines for effecting electromagnetic coupling between
each port and an associated delay line element. Thus, two arrays of
ports are provided, the ports of a first array being coupled to a
first end of respective ones of the delay lines and the ports of a
second array being coupled to the opposite end of said ones of the
delay lines.
In normal operation of the above-described arrangement, one array
is adapted to be fed or illuminated by feedhorn means and the
second array serves as a transmitting array, the delay line
elements interconnecting associated pairs of illuminated and
transmitting ports effecting a preselected aperture phase
distribution. By means of such laminated arrangement using
stripline circuitry, photo etching and bonding techniques may be
employed, whereby a more nearly uniform product is achieved in
production. Also, by the use of such arrangement and techniques,
more accurate geometrical control is obtained for a given
configuration, resulting in improved antenna performance. Further,
the use of such laminated stripline circuitry provides a lens
antenna assembly of minimum weight and bulk, thereby improving the
suitability of such assembly for airborne use. Moreover, such
arrangement readily lends itself to low cost, high volume
production of high-performance microwave arrays.
Accordingly, it is an object of the subject invention to provide an
improved antenna array.
It is another object of the invention to provide a constrained
lens-type antenna having improved performance.
It is a further object to provide an array element for a lens-type
antenna and employing stripline circuit elements.
Still another object is to provide a laminated array of improved
accuracy and reduced weight, bulk and cost.
These and other objects of the invention will become apparent from
the following description, taken together with the accompanying
drawings, in which:
FIG. 1 is a schematic representation of a dielectric lens system,
illustrating the principles thereof;
FIG. 2 is a front elevation of a representative antenna array in
which the inventive concept may be advantageously employed;
FIG. 3 is a side elevation of the antenna of FIG. 2 and showing the
feedhorn therefor;
FIG. 4 is a front elevation of the feedhorn of FIG. 3;
FIG. 5 is a plan, or bottom view, of the feedhorn of FIG. 3;
FIG. 6 is a perspective view, partially exploded, of a portion of
the lens of FIG. 2 and showing certain details of the arrangement
thereof;
FIG. 7 is a vertical section taken through two stacked lineal
arrays of the assembly of stacked lineal arrays of FIG. 6;
FIG. 8 is a plan view of the slipsheet employed in the lineal
arrays of FIGS. 6 and 7;
FIG. 9 is an end view of the slip sheet of FIG. 8 as folded about
the fold lines thereof, and illustrating the shape thereof as
employed in FIGS. 6 and 7;
FIG. 10 is a view in elevation, partially in section, of an
alternate embodiment of the stacked arrays of FIGS. 2 and 6 and
employing a shingled arrangement;
FIG. 11 is a phantom front view of a portion of the embodiment of
FIG. 10, showing in further detail the shingled arrangement;
FIG. 12 is a plan view of a representative array or shingle of the
shingled assembly of FIG. 11;
FIG. 13 is a vertical section of the shingle assembly of FIG. 12;
and
FIG. 14 is an exploded view of a portion of the assembly of FIGS.
12 and 13.
In the FIGS. like elements refer to like parts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The principle of operation of a constrained lens antenna is shown
in FIG. 1. Energy is radiated from a microwave feed 15, such as a
monopulse multimode feed, forming an approximately spherical phase
front. This energy is picked up by suitable elements 16 distributed
over an entrance aperture 17. The energy picked up by a given
entrance aperture element is then transferred via an associated
delay line 18 to a corresponding element or port 19 of an exit
aperture 20. The emergent energy from elements 19 is radiated as a
series of rays 21. The total electrical delay from the feed bridge
15 to the exit aperture 20 for every ray is the same. That is to
say: k.sub.o l.sub.1 + k.sub.m l.sub.2 = constant = k.sub.o f+
k.sub.m l.sub.2o (1) where: .lambda..sub.o = wavelength in free
space .lambda..sub.m = wavelength in the delay medium l.sub.1 =
distance from the feed to any point 16 on the entrance aperture
1.sub.2 = distance from point 16 on the entrance aperture to a
corresponding point 19 on the exit aperture via the delay line
1.sub.2o = a fixed distance in the lens on the system axis f =
focal length This is precisely the condition for a collimated true
time delay antenna system. For beams other than the collimated
ones, the phase delay is made to produce the appropriate phase
distribution.
While ordinarily (in the prior art) the delay medium takes the form
of multichannel branched waveguides or coaxial transmission lines,
the constrained lens antenna of the subject invention uses a unique
stripline packaging technique to produce a transmission line which
is very lightweight and has a low volume, as to be especially
advantageous for airborne applications.
A representative arrangement of an exit aperture 20 comprising a
coplanar plurality of radiating elements or ports 19 is shown in
front elevation in FIG. 2. As illustrated, such coplanar
arrangement of elements is comprised of a plurality of discrete and
mutually parallel lineal arrays 22 of radiating elements or ports
19 mounted within a ringlike frame 23. The backside of the device
of FIG. 2 is similarly arranged and includes an entrance aperture
17 having a plurality of stripline assemblies 22 of lineal arrays
of radiating elements exposed to a feedhorn 15 mounted aft of frame
23 by support rods 24a and 24b, as shown more particularly in the
side elevation of FIG. 3. Such feedhorn may be of the switchable
multihorn-type for providing a selected feed for achieving a
desired antenna beamwidth or mode in a multimode radar system
application. Such multihorn feed arrangement is shown more
particularly by the front elevation view in FIG. 4 of the feedhorn
15 of FIG. 3, while the multiport input 25 thereto is shown more
particularly in the bottom view of feed 15 in FIG. 5. The details
of the construction and operation of such feed are known in the art
and do not form a part of the inventive concept and may be departed
from or varied without effecting such inventive concept.
The construction and arrangement of the lens having an entrance
aperture 17 and exit aperture 20 of FIGS. 2 and 3 and embodying the
inventive concept is shown in greater particularity in FIG. 6.
Referring to FIG. 6 there is illustrated a perspective view,
partially exploded, of a portion of the lens of FIGS. 2 and 3 and
showing certain details of the arrangement thereof. There is
provided a plurality of discrete and mutually-parallel, stacked
laminated stripline assemblies 22. Each assembly 22 comprises a
laminated pair of mutually nested, rigid dielectric U-channels 26
and 27, (shown in vertical section in FIG. 7), sandwiching a
flexible dielectric slipsheet 28 having a plurality of electrically
conductive coplanar lines 18 of selected lengths deposited thereon
as discrete delay elements. Each delay line 18 has two terminii 29a
and 29b a corresponding terminus of each of the delay elements 18
being regularly spaced along sheet 28, as shown in FIG. 8, with the
same regularity as the occurrence or spacing of microwave ports 16
and 19 in assembly 22. The sheet 28, when installed in the
sandwiched situation of FIG. 7, is folded about fold lines shown in
the end view of FIG. 9.
The inner and outer U-shape surfaces of laminated assembly 22 of
FIG. 6 (e.g., the outer surfaces of dielectric U-channels 26 and
27) are electrically conductively coated, as to comprise a metallic
clad assembly, entrance and exit or feed ports 16 and 19 being
etched or otherwise formed in the metallic cladding of opposing
walls of dielectric U-channel 26, each port being in registry with
an associated terminus of a mutually exclusive one of the delay
lines 18. In other words, an entrance port 16 will be in registry
with one terminus 29b of a delay line 18 while the corresponding
exit port 19 will be in registry with the other terminus 29a of
delay element 18. Locii of shorting pins 40 through the opposing
walls of the laminated U-channel assembly describe microwave
cavities containing separate ones of ports 16 and 19 and associated
terminii 29a and 29b as to effect efficient and close-tolerance
electromagnetic coupling therebetween. Such shorting pins, shown
more particularly in FIG. 7, serve to suppress spurious energy
modes. In practice, a foam plastic filler 30 may be inserted in the
volume enclosed by the stacked U-shaped channel assemblies, as
indicated in FIG. 7, in order to structurally stiffen the lens
assembly.
In normal operation of the above-described arrangement, microwave
electromagnetic energy impinging upon an entrance port 16 is
coupled to a terminus 29b of delay line 18 by means of the
above-described microwave cavity, conducted through delay line 18
and electromagnetically coupled to an associated output or exit,
port 19. The cooperation of all such selectively delayed couplings
of entrance and exit port pairs defining the lens, provides a
desired aperture phase distribution.
Although the laminated microwave stripline lens assembly has been
described in terms of parallel stacked U-shaped channels, the
concept of the invention is not so limited and a shingled
arrangement may be alternatively preferred, as shown in FIGS.
10--15 inclusive.
Referring to FIG. 10, there is illustrated in side elevation,
partially torn away, an alternate embodiment of the dielectric lens
assembly of FIG. 2, and illustrating a shingled arrangement for a
plurality of discrete and mutually parallel laminated stripline
assemblies 38. As illustrated, an impinging ray of microwave energy
is received from the left and at the top of a single or laminated
stripline assembly 38 is selectively delayed therethrough, and
emergent therefrom at the lower portion on the right side thereof
as emergent beam 21.
As shown in FIGS. 12 and 13, each such stripline assembly 38
comprises a laminated pair of relatively rigid dielectric plates 36
and 37 and a dielectric slipsheet 28 having a plurality of
electrically conductive delay lines 18 of selected lengths
deposited thereon, slipsheet 28 being sandwiched between the plates
36 and 37 of the laminated pair of dielectric plates. Opposing
faces 39 and 40 of laminated assembly 38 are clad with an
electrically conductive coating, each of faces 39 and 40 having a
plurality of microwave ports formed by apertures 19 and 16 in such
coatings. Each aperture is in registry with an associated terminus
of a mutually exclusive one of the delay lines 18 for effecting
electromagnetic coupling between a port and an associated delay
line element. Apertures 19 in coating 39 and apertures 16 in
coating 40 form lineal arrays of ports in a respective one of
plates 36 and 37 and parallel to and proximate an opposite edge of
laminated assembly 38. Thus, as shown in the exploded view of FIG.
14, apertures 16 form a lineal array in plate 37 parallel to and
proximate the bottom edge thereof and in registry with associated
ones of terminii 29b of delay lines 18, while apertures 19 form a
lineal array in plate 36 parallel and proximate the top thereof and
in registry with associated ones of terminii 29a of delay lines 18.
Thus, the array of apertures in each of coatings 39 and 40 form a
lineal array of ports parallel to and proximate an opposite edge of
laminated assembly 38 and being electromagnetically coupled to
opposite terminii 29a and 29b of delay lines 18. Thus, as shingle
assembly 38 is utilized in the shingled arrangement of FIGS. 10 and
11, the upper array of apertures 19 in face 39 of dielectric plate
39 may comprise an entrance aperture of the lens assembly, while
the lower array of apertures 16 in face 40 of plate 37 may comprise
an exit aperture.
Such shingled arrangement, in which the radiating apertures or
ports are arranged on opposite sides of the flat stripline laminate
and at opposite ends or terminii of the delay line elements,
eliminates the need for the double bend of the U-channel
configuration of FIGS. 6, 7 and 9, and allows a much thinner
package for the dielectric lens assembly. Although such shingle
arrangement has been illustrated as lineal, other singling
arrangements may be used. For example, a circular arrangement may
be employed, in which case each shingle may be shaped in the form
of a ring or arcuate section thereof. Although rigid dielectric
plates have been described for supporting the slipsheet and the
metallic cladding, it is clear that other dielectric means
including nonrigid media may be employed.
Although the invention has been described and illustrated in
detail, it is to be clearly understood that the same is by way of
illustration and example only and is not to be taken by way of
limitation, the spirit and scope of this invention being limited
only by the terms of the appended claims.
* * * * *