U.S. patent number 3,737,909 [Application Number 05/047,378] was granted by the patent office on 1973-06-05 for parabolic antenna system having high-illumination and spillover efficiencies.
This patent grant is currently assigned to Radiation Incorporated. Invention is credited to Homer E. Bartlett, Emory L. Sheppard.
United States Patent |
3,737,909 |
Bartlett , et al. |
June 5, 1973 |
PARABOLIC ANTENNA SYSTEM HAVING HIGH-ILLUMINATION AND SPILLOVER
EFFICIENCIES
Abstract
An antenna feed system which simultaneously produces nearly
uniform amplitude and phase illumination as well as high spillover
efficiency, in a parabolic antenna, is composed of a feed or horn
source and an interposed dielectric element. The dielectric element
diffracts the emitted energy to maximize the spillover and
illumination efficiencies. These efficiencies are increased by
configuring the surface of the interposed dielectric element. In
one species the interposed element is a lens and in another is a
reflector coated with dielectric material.
Inventors: |
Bartlett; Homer E. (Melbourne,
FL), Sheppard; Emory L. (Morrisville, NC) |
Assignee: |
Radiation Incorporated
(Melbourne, FL)
|
Family
ID: |
21948622 |
Appl.
No.: |
05/047,378 |
Filed: |
June 18, 1970 |
Current U.S.
Class: |
343/755;
343/781R; 343/840 |
Current CPC
Class: |
H01Q
19/19 (20130101); H01Q 19/026 (20130101) |
Current International
Class: |
H01Q
19/10 (20060101); H01Q 19/02 (20060101); H01Q
19/19 (20060101); H01Q 19/00 (20060101); H01q
019/10 () |
Field of
Search: |
;343/753,754,755,781,840 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
973,583 |
|
Oct 1964 |
|
GB |
|
1,163,156 |
|
Sep 1969 |
|
GB |
|
Primary Examiner: Lieberman; Eli
Claims
We claim:
1. An antenna system having a main focusing means for redirecting
energy having a focus proximate the axis of symmetry of said main
focusing means and a feed device having a phase center proximate
the axis of symmetry, said antenna system including a dielectric
energy refracting means through which a beam transmitted between
said main focusing means and said feed device passes, said
refracting means having a first irregular surface means at which
energy is redirected and substantially wholly comprising segments
whose slopes are each a function of beam intensity at the segment
to redirect the beam across an intervening space to a boundary at
which the intensity of the beam has a relative distribution within
the beam different from that of the beam at the first surface
means, and a second irregular surface means at said boundary
comprising a plurality of segments having slopes which are a
function of the directions of the redirected beam at the segments
for further redirecting the beam to proceed along a course
comprising lines extending from one of said focus and center, said
slopes of the segments of one of said irregular surface means of
said refracting means being a function of a first angle between the
axis of symmetry of said main focusing means and the apparent line
of travel of energy through said focus and a second angle formed
between the axis of symmetry and the line of travel of said energy
through said refracting means, and said slopes of the segments of
the other of said irregular surface means being a function of said
second angle and of a third angle between the axis of symmetry and
the apparent line of travel of energy through said phase
center.
2. The antenna system of claim 1 wherein said energy refracting
means is a transparent lens; and the two surface means of the lens
are defined by the equations:
- (dr/rd.theta.) = sin (.theta. - .alpha.)/(1/.sqroot..epsilon.) -
cos (.theta. - .alpha.) (1) da/ad.beta. = .sqroot..epsi lon. sin
(.beta. - .alpha.)/.sqro ot..epsilon. cos (.beta. - .alpha.) - 1
(2)
tan .alpha. = (a sin .beta. - r sin .theta.)/(P.sub.1 P.sub.2 + a
cos .beta. - r cos .theta.) (4)
wherein:
a = the distance from said focus to said one surface means
.epsilon. = the dielectric constant of said refracting means
.beta. = said first angle
.beta..sub.m = maximum value of .beta.
.alpha. = said second angle
r = the distance from said phase center to said other of said
surface means
.theta. = said third angle
.theta..sub.m = maximum value of .theta..
3. The antenna system of claim 1 wherein said refracting means is
located between said feed device and said main focusing means; and
wherein substantially all of the energy coupled to said feed device
passes through said refracting means.
4. An antenna system as defined in claim 1 and wherein a relative
distribution of intensity of the reflected beam resulting external
to the antenna is substantially uniform, and wherein said beam has
a first phase front about said focus and has a second phase front
about said phase center and at least one of said first and second
phase fronts is approximately spherical.
5. An antenna system having a main focusing means for redirecting
energy having a focus proximate the axis of symmetry of said main
focusing means and a feed device having a phase center proximate
the axis of symmetry, said antenna system including a dielectric
energy refracting means through which a beam transmitted between
said main focusing means and said feed device passes, said
refracting means having a first irregular surface means at which
energy is redirected and substantially wholly comprising segments
whose slopes are each a function of beam intensity at the segment
to redirect the beam across an intervening space to a boundary at
which the intensity of the beam has a relative distribution within
the beam different from the beam redirected by the first surface
means, and a second irregular surface means at said boundary
comprising a plurality of segments having slopes which are a
function of the directions of the redirected beam at the segments
for further redirecting the beam to proceed along a source
comprising lines extending from one of said focus and center, said
refracting means including highly reflective means on one of said
irregular surface means, said refracting means being arranged so
that energy in said beam passes in a first direction through the
other of said surface means and through said refracting means and
impinges upon said reflective means and passes through aid
refracting means in a second direction between said reflective
means and through said other surface means, said slopes of said
other of said surface means being a function of a first angle
formed between said axis of symmetry of the main focusing means and
the line of travel of said energy along lines extending from the
focal point of said main focusing means and a second angle formed
between said axis and the line of travel of said energy as it
passes through said refraction means, said slopes of the one of
said surface means having said reflective means being a function of
said second angle and a third angle formed between said axis and
the line of travel of said energy as it passes in said second
direction through said refracting means; and said slopes of the
other of said surface means of said refracting means being a
function of said third angle and a fourth angle formed between the
axis of symmetry of said main focusing means and the line of travel
of said energy along lines extending from said phase center.
6. the antenna system of claim 5 wherein said reflective means on
said one surface means and said other surface means are defined by
the equations:
dr/rd.theta. = .sqroot..epsilon. sin
(.theta.-.alpha.)/.sqroot..epsilon. cos (.theta.-.alpha.) - 1 (5)
da/ad.beta. = .sqroot..epsi lon. sin (.beta.-.xi.) /.sqroot..epsi
lon. cos (.beta.-.xi.) (6)
dx/dy = - tan (.xi. - .alpha.)/2 (8) .alpha. = tan .sup..sup.-1 (y
- r sin .theta.)/P.su b.1 P.sub.2 - x - r cos (9) eta.)
.xi. = tan.sup..sup.-1 (a sin .beta. - y)/(a cos .beta. - x)
wherein:
.epsilon. = the dielectric constant of said refracting means
a = the distance from said focus to said other of said surfaces
along said lines extending from said focal point
.beta. = said first angle
.beta..sub.m = maximum value of .beta.
.xi. = said second angle
.theta. = said fourth angle
.theta..sub.m = maximum value of .theta.
.alpha. = said third angle
r = the distance from said phase center to said other surface along
said lines extending from said phase center
x = a coordinate of a rectangular coordinate system having its
origin at said first focal point, extending along said axis
y = a coordinate of said coordinate system extending transversely
to said axis.
7. The antenna system of claim 1 wherein said highly reflective
means is a metallic surface; and wherein said feed device is
located between said refracting means and said main focusing means;
said refracting means being situated between said metallic surface
and said feed device.
8. An antenna system as defined in claim 5 and wherein a relative
distribution of intensity of the reflected beam resulting external
to the antenna is substantially uniform, and wherein said beam has
a first phase front about said focus and has a second phase front
about said phase center and at least one of said first and second
phase fronts is approximately spherical.
9. An antenna apparatus for transmitting or receiving
electromagnetic power comprising main focusing means for
redirecting power with a principal axis and having a geometric
focus, and a feed device having a phase center and a power density
pattern F(.theta.), comprising lens means having first and second
boundary portions for changing the direction of propagation of
electromagnetic power received thereon, the power between said
phase center and said main focusing means being a beam having a
first segment at least a portion of which is between said phase
center and lens means and a second segment at least a portion of
which is between said lens means and said main focusing means, said
first and second boundaries extending generally transversely of the
axis and said second boundary being offset a distance along the
beam route from the first means in a downstream direction for power
flow, said first beam segment being directed along lines emanating
from said phase center at various directional angles .theta. up to
an angle .theta..sub.m, said second beam segment being directed
along lines emanating from said focus at various directional angles
.beta. up to an angle .beta..sub.m, both .theta. and .beta. being
measured from the principal axis, said apparatus having a first
phase wavefront shape and a first power density distribution
F(.theta.) in the first beam segment up to the angle .theta..sub.m,
and having a substantially spherical second phase wavefront shape
and a substantially uniform second power density distribution of
said beam as measured with respect to the angle .beta. in the
second beam segment up to the angle .beta..sub.m, said first means
receiving one of said beam segments and being configured to be
comprised of differential segments for redirecting by differing
amounts the portions of received beam power received upon the
segments at differing distances from said axis and cooperating with
said offset distance to convert the power density distribution
within said beam to the distribution in the other of said beam
segments, said second boundary being configured to be comprised of
a plurality of differential segments for redirecting by differing
amounts the portions of beam power received upon segments at
differing distances from said axis to follow lines emanating at
angles .theta. and .beta. respectively from one of said center and
focus, and wherein the portions of beam power flowing at any
directional angle .theta. in the first segment flow at a respective
directional angle .beta. in accordance with the relationship
Description
BACKGROUND OF THE INVENTION
Various types of antenna systems are known in the prior art. One of
these systems utilizes a reflecting element which is parabolically
configured and which has a source of energy at its focal point. The
energy emitted by the energy source is theoretically reflected from
the parabolic reflector in substantially parallel rays. Although
the following description is directed to a transmitting antenna
system, the description is equally applicable to a receiving
antenna.
Various attempts have been made to maximize the efficiency of such
antenna systems. One such system is the Cassegrain. In this type of
antenna system, a parabolic main reflector is used and a hyperbolic
subreflector is located near the focal point of the parabolic main
reflector. An energy source is then located near the hyperbolic
subreflector. The energy emitted by the energy source is reflected
by the subreflector onto the parabolic main reflector and out into
the atmosphere. The over-all efficiency of such an antenna system
is determined primarily by the ability of the energy source to
illuminate the reflector uniformly across its surface. This is
commonly referred to as the illumination efficiency. Another
determining factor of the over-all efficiency of such an antenna
system is the spillover efficiency. This is the ability of the
subreflector to uniformly illuminate the main reflector while
minimizing the energy which passes the edges of the main
reflector.
To some extent these two efficiencies are inconsistent. This is so
because the maximization of the illumination efficiency requires
the edges of the main reflector to be illuminated to the same
extent that its interior portions are illuminated. This inherently
results in an increase of the radiation spillover and thereby
decreases the spillover efficiency. Likewise, an attempt to
decrease the energy spillover and thereby increase the spillover
efficiency results in a decrease of the illumination along the
edges of the reflector and a decrease in the illumination
efficiency results. This difficulty has been recognized in the past
and has been partially solved by compromising between the two
efficiencies. Accordingly, most prior art antenna systems
compromise between the illumination and the spillover efficiencies
so that each are in the order of 75 to 80 per cent. These
efficiencies are about the highest obtainable by conventional
technology.
One known system has greatly improved these theoretical and
practical efficiencies in a Cassegrain system such that a
theoretical 100 percent illumination efficiency is obtainable while
increasing the spillover efficiency to above 90 per cent. This
system is based on the principle that planned deviations of the
hyperbolic subreflector and parabolic main reflector from the
hyperbolic and parabolic configurations can result in the above
noted increases in efficiencies.
An article entitle "High Efficiency Antenna Reflector" by William
F. Willaims, published in the July 1965 issue of The Microwave
Journal on pages 79 to 82 describes an antenna system which
improved the illumination and spillover efficiencies of a
Cassegrain antenna system. The article presents a mathematical
analysis showing that deviations of the sort mentioned above
results in increases of the illumination and spillover
efficiencies. Although the antenna system described in the article
is a theoretical improvement of the other prior art antenna systems
it has several practical disadvantages. As a practical matter, it
is more expensive to manufacture a reflector which conforms to the
required configuration. Also, the technique described does not
allow for the optimization of antenna systems which are already in
use.
SUMMARY OF THE INVENTION
The inventive antenna system contains a dielectric refractive
element to refract the energy emitted from the energy source so
that the main reflector is uniformly illuminated over its entire
surface while the energy spillover around its edge is minimized.
These two results are achieved by forming the surface of the
refracting element according to equations derived for an antenna
system having a parabolic main reflector. The inventive system
therefore is more practical than the system describe in the
Microwave Journal article fully referenced hereinabove. Because a
parabolic main reflector is used, existing manufacturing procedures
can be used. For this reason the inventive antenna system is more
economical and mechanically feasible than the prior art
systems.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a first preferred embodiment of the inventive system
utilizing a reflective subreflector.
FIG. 2 is a second preferred embodiment of the inventive system
utilizing a shaped lens which is transparent to the energy emitted
by the energy source.
FIGS. 3, 4 and 5 are diagrams useful in developing the equations
which define the configurations of the refracting elements.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiment shown in FIG. 1 includes a reflector 10, the
cross-sectional configuration of which is parabolic. An energy
refractor 11 is located close to the focal point 12 of the
parabolic reflector 10. Refractor 11 includes a reflective surface
13 and a dielectric coating 14. The reflective surface 13 is made
from a highly reflective metal. Dielectric coating 14 is made from
a material which is transparent to the energy, polypropylene and
quartz are examples of materials which can be used. An energy
source 15 is located at a point P.sub.1 positioned between
refractor 11 and parabolic reflector 10. Solid lines 16, 17, 18,
and 19 are used to illustrate the path of radiation from the energy
source 15 through the dielectric coat 14 and to the reflector 10
out to the atmosphere from the reflector. Broken line 20 is used as
an extension of line 18 to show that the radiation appears to
emanate from the focus point 12 located at a point P.sub.2. Only
half of the parabolic reflector 10 is shown in the figure;
actually, the reflector 10 is symmetrical about the X axis and also
has radial symmetry about this axis. Reflector 11 also is radially
symmetrical about the X axis. Reflector 11 has two irregular
surfaces. Reflective element 13 is bonded, or otherwise fixed to
one of these surfaces. The other surface is indicated by reference
number 21. Both of these surfaces are irregular, and they can have
different configurations. The exact configurations are defined by a
set of equations which are based on the parameters of the antenna
system, and the dielectric constant of coating 14. The illumination
efficiency is optimized and the spillover efficiency is greatly
increased by configuring the two surfaces of the refractor 11 in
accordance with these equations and their development is presented
hereinafter.
FIG. 2 is a second preferred embodiment of the invention. This
embodiment also employs a parabolic reflector 10. A shaped lens 26,
which is transparent to the radiation emitted by the energy source
27, is located in the vicinity of the focal point 28 of the
parabolic reflector 10. Lens 26 is composed of a dielectric
material such as quartz or polypropylene. The two irregular
surfaces 29 and 30 of lens 26 are configured such that the energy
passing through the lens optimizes the illumination efficiency of
the reflector 10. The configurations required for this optimization
are also defined by a set of equations based on the same types of
considerations as those of the FIG. 1 embodiment.
The FIG. 2 solid lines 31, 32, 33 and 34 are used to show the path
of the radiation from the feed source 27 through the lens 26, its
path between refractor 26 and reflector 10, and its reflection from
the reflector 10. In both FIGS. 1 and 2 the line A-B is used to
represent a surface upon which constant amplitude and phase
illumination is desired.
The primary difference between the FIG. 1 and FIG. 2 embodiments
lies in its refractive elements 11 and 26. In FIG. 1 a reflective
surface 13 reflects the energy back through the dielectric 14.
Consequently energy source 15 is positioned between refractor 11
and reflector 10. In FIG. 2 refractor 26 has no reflective surface.
Energy therefore passes through the dielectric lens 26 only once.
Lens 26 is therefore positioned between energy source 27 and
reflector 10.
The refractive elements 11 and 26 are very similar, in that they
bend the energy after it emanates from the energy source but before
it reaches parabolic reflector 10. They are also similar because
they both have two irregular surfaces defined by equations
developed by using the same system criterion. Lens 26 and refractor
11 are symmetrical about the X axis and their axis of symmetry are
coincident with the axis of symmetry or reflector 10. The mean
thickness of lens 26 and refractor 11 can be as thin as a fraction
of an inch and can exceed 5 inches.
Both refractive elements 11 and 26 respectively shown in FIGS. 1
and 2 are designed such that the percentage of the energy from the
energy source which is contained within the solid angle .theta. is
equal to the percentage of the aperture area contained within a
circle of radius X. The aperture illumination is therefore very
nearly uniform. Also, the design configurations of the refractive
elements 11 and 26 are such that the energy leaving the dielectric
refractor (11 or 26) must have a spherical phase front about point
P.sub.2.
The result of shaping the surfaces of lens 26 and refractor 11 as
dictated by the equations set forth hereinafter invariably will
result in the surfaces being irregular in configuration. However,
the configurations shown in the figures are not necessarily those
which will be derived for every instance. The shapes of the
surfaces will be dependent upon the design parameters of the
antenna system as well as the dielectric constant of the material
used to construct the refractive element 11 or 26.
The following four equations described the configurations of
surfaces 29 and 30 of lens 26 shown in the FIG. 2 embodiment
- (dr/rd.theta.) = sin (.theta.- .alpha.)/(1/.sqroot..epsilon.) -
cos (.theta. - .alpha.) (1) da/ad.beta. = .sqroot..epsi lon. sin
(.beta. - .alpha.)/.sqro ot..epsilon. cos (.beta. - .alpha.) - 1
(2)
tan .alpha. = (a sin .beta. - r sin.theta.)/(P.sub.1 P.sub.2 + a
cos.beta. - r cos.theta.) (4)
where: .epsilon. is the dielectric constant of the dielectric lens
26, all other variables are defined by FIG. 2.
In equation (3) the maximum value of .beta. is .theta.by
.beta..sub.m and represents the angle from the edge of the
parabolic reflector 10. Likewise, .theta..sub.m is the maximum
value of .music-flat. at which an electromagnetic ray from P.sub.1
will be refracted by the lens 26 at an angle .beta..sub.m to the
edge of the parabolic reflector 10.
Equation (1) is written with Snell's Law of Refraction at surface
29. It is used to relate the slope of surface 29 to the angles
.theta. and .alpha..
Equation (2) is written with Snell's Law of Refraction at surface
30. It is used to relate the angles .beta. and .alpha. to the slope
of surface 30. It also requires the energy leaving the lens 26 to
have a constant phase about point P.sub.2. P.sub.2 is the focal
point of parabolic reflector 10.
P.sub.1 is the origin of the polar coordinate system r,.theta. and
also the phase center of the feed source 27.
In equation (4) P.sub.1 P.sub.2 is the distance between points
P.sub.1 and P.sub.2.
A better understanding of equations (1) - (4) can be obtained by
viewing their development.
Equation (1) is developed by use of Snell's Law of Refraction at
surface 29. For convenience and clarity those portions of FIG. 2
required for the development of equation (1) are shown in FIG.
3.
From FIG. 3:
.alpha. = .theta. + .delta..sub.1 - .delta..sub.2 (1a)
.delta..sub.1 .noteq. .delta..sub.2 because of the dielectric
constant .epsilon. of the lens material
.sqroot..epsilon. sin .delta..sub.2 = sin .delta..sub.1 (1b) -
(dr/rd.theta.) = tan .gamma. = tan .delta..sub.1 (1c)
.sqroot..epsilon. sin (.theta. + .delta..sub.1 - .alpha.) = sin
.delta..sub.1 (1d) sin (.theta.-.alp ha.) cos .delta..sub.1 + cos
(.theta.-.alp ha.) sin .delta..sub.1 = sin .delta..sub.1 /
.sqroot..epsi lon. (1e)
cot .delta..sub.1 = [(1/.sqroot..epsilon.) - cos (.theta.-.alpha.)]
/sin (.theta.-.alpha.) (1f)
and
-(dr/rd.theta.) = sin (.theta.-.alpha.)/(1/.sqroot..epsilon.) - cos
(.theta.-.alpha.) (1)
Equation (2) is developed with Snell's Law of Refraction at surface
30. Here, for purposes of convenience and clarity those portions of
FIG. 2 required for the development of equations (2) are repeated
in FIG. 4.
From FIG. 4:
da/ad.beta. = tan .gamma. = tan (.PSI..sub.1 + .beta. -.alpha.)
(2a) .sqroot..epsi lon. sin .PSI..sub.1 = sin (2b) ..sub.2
.sqroot..epsilon. sin .PSI..sub.1 = sin
(.beta.-.alpha.+.PSI..sub.1)
= sin (.beta.-.alpha.) cos.PSI..sub.1 +
cos (.beta.-.alpha.) sin .PSI..sub.1 (2c) .sqroot..epsi lon. =
cot.PSI..sub.1 sin (.beta.-.alph a.) + cos (.beta.-.alph a.)
(2d)
cot.PSI..sub.1 = [.sqroot..epsilon. - cos (.beta.-.alpha.)] /sin
(.beta.-.alpha.) 2e) tan.PSI..sub. 1 = sin (.beta.-.alph
a.)/[.sqroot.. epsilon. - cos (.beta.-.alph a.)] (2f)
da/ad.beta. = [tan.PSI..sub.1 + tan (.beta.-.alpha.)]/[1 -
tan.PSI..sub.1 tan (.beta.-.alpha.)] (2g)
and
da/ad.beta. = .sqroot..epsilon. sin
(.beta.-.alpha.)/.sqroot..epsilon. cos (.beta.-.alpha.) - 1 (2)
Equation (3) is derived from the conservation of energy principle
as follows:
Integration of the right side of equations (3a) and (3b) while
holding I (.beta.) = constant, subsequent division of (3a) by (3b)
and their differentiation of the result with respect to .theta.
yields:
FIG. 5 combines the portions of FIGS. 3 and 4 necessary to an
understanding of equation (4).
From FIG. 5:
tan.alpha.= f/g (4a) f = a sin.beta.- r (4b) g = P.sub.1 P.sub.2 +
a cos.beta. - r cos.theta. (4c)
tan.alpha. = (a sin.beta. - r sin.theta.)/(P.sub.1 P.sub.2 + a
cos.beta. - r cos.theta.) (4)
FIG. 2 and equations (1) - (4) related thereto are directed to an
antenna utilizing a transparent lens 26 to optimize the
illumination efficiency. FIG. 1 shows an antenna system which
utilizes a dielectric coated subreflector as the energy refracting
device. The geometry of the two antenna systems therefore varies
slightly. However, the same principles apply.
Equations (5) through (10) are presented below as those defining
the boundary surfaces 13 and 21 of the FIG. 1 embodiment necessary
to optimize the illumination efficiency of an antenna utilizing a
dielectric coated subreflector.
dr/rd.theta. = .sqroot..epsilon. sin
(.theta.-.alpha.)/.sqroot..epsilon. cos (.theta.-.alpha.) - 1 (5)
da/ad.beta. = .sqroot..epsi lon. sin (.beta.-.xi.) /.sqroot..epsi
lon. cos (.beta.-.xi.) (6)
dx/dy = - tan (.xi. - .alpha.)/2 (8) .alpha. = tan .sup..sup.-1 (y
- r sin .theta.)/(P.s ub.1 P.sub.2 - x - r (9) .theta.)
.xi.= tan.sup..sup.-1 (a sin .beta.- y)/(a cos .beta.- x)
Equations (5) and (6) are developed by use of Snell's Law of
Refraction at surface 21 in a manner very similar to Equations (1)
and (2). The symbol .epsilon. is the dielectric constant of coating
14.
Equation (5) relates the slope of surface 21 to the angles .theta.
and .alpha.. Equation (6) relates the slope of surface 13 to the
angles .beta. and .xi..
Equation (7) is the same as Equation (3). Some manipulation of this
equation shows that the energy density as a function of .beta. is
sec.sup.4 .beta./2 for 0 < .beta. < .beta. .sub.m and zero
for .beta. > .beta..sub.m. Uniform amplitude distribution at
Plane AB results from this relationship.
Equation (8) is developed by use of Snell's Law of Refraction at
surface 13 and relates the slope of surface 13 to the angles
.alpha. and .xi..
Equations (9) and (10) relate the points of surface 13 to those of
surface 21. In equations (9) and (10) x and y respectively refer to
the horizontal and vertical coordinates of a coordinate system
having its origin at P.sub.2.
Because the same basic principles apply to equations (1) - (4) and
equations (5) through (10) the full development of the last set of
equations is not presented.
The problem of optimizing the illumination efficiency of a
parabolic antenna system while simultaneously increasing the
spillover efficiency has been solved by the invention. The solution
lies in providing the antenna system with an energy refraction
device interposed between the energy source and the main parabolic
reflector. The two surfaces of the refracting device are
irregularly formed according to a set of equations based upon the
parameters of the antenna system. The equations are developed for
an antenna system having a parabolic reflector and therefore the
invention is very practical from both a theoretical and a
manufacturing view point. The use of a parabolic main reflector
also makes antenna systems in accordance with the invention and
thereby greatly improve their illumination and spillover
efficiencies.
While we have described and illustrated specific embodiments of our
invention, it will be clear that variations of the details of
construction which are specifically illustrated and described may
be resorted to without departing from the true spirit and scope of
the invention as defined in the appended claims.
* * * * *