CA1262571A - Radome-lens ehf antenna development - Google Patents
Radome-lens ehf antenna developmentInfo
- Publication number
- CA1262571A CA1262571A CA000524264A CA524264A CA1262571A CA 1262571 A CA1262571 A CA 1262571A CA 000524264 A CA000524264 A CA 000524264A CA 524264 A CA524264 A CA 524264A CA 1262571 A CA1262571 A CA 1262571A
- Authority
- CA
- Canada
- Prior art keywords
- lens
- radome
- center
- sphere
- antenna
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000003989 dielectric material Substances 0.000 claims abstract description 5
- 230000005540 biological transmission Effects 0.000 claims 1
- 238000003780 insertion Methods 0.000 description 9
- 230000037431 insertion Effects 0.000 description 9
- 238000005452 bending Methods 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 238000013316 zoning Methods 0.000 description 4
- 230000003321 amplification Effects 0.000 description 3
- 230000009977 dual effect Effects 0.000 description 3
- 238000003199 nucleic acid amplification method Methods 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/42—Housings not intimately mechanically associated with radiating elements, e.g. radome
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
- H01Q15/08—Refracting or diffracting devices, e.g. lens, prism formed of solid dielectric material
Abstract
ABSTRACT OF THE DISCLOSURE
A radome-lens comprises a shell of dielectric material having an outer surface in the form of a small circle defined by a sphere and a plane intersecting the sphere, an opening at one end of the shell for reception of an antenna therein, the surface having a central axis which is normal to the plane and extends through the center of the sphere, and an inner surface having a spherical portion centered at a second center disposed along the axis adjacent the first mentioned center but spaced toward the outer surface. When so constructed, the invention functions as a radome in the sense that it houses and protects an antenna in the usual manner and also functions as a lens in the sense that it amplifies the scan angle of the antenna from an angle of less than 90° to 90° or more.
A radome-lens comprises a shell of dielectric material having an outer surface in the form of a small circle defined by a sphere and a plane intersecting the sphere, an opening at one end of the shell for reception of an antenna therein, the surface having a central axis which is normal to the plane and extends through the center of the sphere, and an inner surface having a spherical portion centered at a second center disposed along the axis adjacent the first mentioned center but spaced toward the outer surface. When so constructed, the invention functions as a radome in the sense that it houses and protects an antenna in the usual manner and also functions as a lens in the sense that it amplifies the scan angle of the antenna from an angle of less than 90° to 90° or more.
Description
This invention relates to a radome-lens.
B~CKGROUND OF THE INVE~TION
A radome is a thin shell of uniforM thickness which 05 is normally used to house and protect an antenna from the weather. Because of the interpositlon of the radome between the antenna and outside space from which the antenna is to receive or transmit signals, the radome always adds some refraction and insertion losses to the 10 signal and, as a consequence, the radome has heretofore been regarded as a hinderance to the radiation perform-ance of the antenna.
A further problem with which the present invention is concerned relates to the number of antennas which are 15 employed to cover the whole spherical sky, and, parti-cularly, with minimizing the number oE antennas requirecl for this purpose. Assuming that each an-tenna is mounted on an altitude-azimuth mount or its equivalent, the scanning area oE each antenna is a circular region. The 20 term --circular region-- is referable to a --small circle-- which, in the terminology of spherical trigono-metry, is the intersection of a sphere and a plane cutting the sphere.
The largest circular region is the spherical sky ~5 itself. It is not possible for a single antenna to scan the entire sky because of blockage by the antenna mount.
The next largest region, then, is a hemispherical region. Two antennas, ~ith their broadside directions pointing in opposite directions~ are required to scan 30 the entire sky, provided that each antenna is capable of scanning up to 90 from the broadside directicn.
However, if such antennas are not available, it can be shown that four antennas would be required to cover the entire sky without holes with their broadside directions 35 being the normals of the surfaces of an equilatera]
tetrahedron. In that case, the scanning angle required from each antenna must range between 0 to 70.5, which is not significan-tly reduced from the 90 required for a "
:
- ~
.. : . , ~2~
two antenna configuration. Thu~s, it is clearly highly desirable to provide an ant~nna which is capable of scanning up to 90.
SUMMARY OF THE INVENTION
It has been found that a radome can be configured in such a manner that it not only eliminates the refraction problem discussed earlier but employs that characteristic of radomes to amplify transmitted and/or received rays to enable the scanning of the whole sky with two antennasO
In accordance with the present invention there is provided a radome-lens comprising a shell of dielectric material having an outer surface in the form o~ a small circle defined by a sphere and a plane intersecting the sphere, an opening at one end of the shell for reception of an antenna therein, the surface having a central axis which is normal to the plane and extends through the center of the sphere, and an inner surface having a spherical port:Lon centered at a second center disposed along the axis adjacent the first mentioned center but spaced toward the outer surface and including a plurality of æones concentrically disposed along said axis, each said zone being centered at said second center.
When so constructed, the present invention functions as a radome in the sense that it houses and protects an antenna in the usual manner. It also functions as a lens in the sense that it amplifies the scan angle of the antenna from an angle of less than 90 to 90.or more without much spherical aberration. Such amplification avoids ground plane obstruction and, accordingly, only two antennas, each e~uipped with the radome-lens of the present invention are required to cover the whole sky. In an aperture planar phased array with electronic scanning, such amplification enables the array to retain substantial antenna gain and partial dual polarization capability The aperture antenna could be a microstrip antenna array scanned completely electronically or a reflector scanned completely mechanically, or other hybrid systems _ 3 _ ~6~
of microstrip antennas and reflectors with partial electronic and partial mechanical scanning.
BRIEF DESCRIPTION OF THE DRAWI~GS
-05 These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:
FIGURE 1 is a cross sectional view of a fish-eye 10 lens at a scan angle of 0, FIGURE 2 is a cross sectional view of a fish-eye lens at a scan angle of 45~, F~GURE 3 is a cross sectional view of a fish-eye lens at a scan angle of 90~, FI~URE 4 is a cross sectional view of the radome-lens at a scan angle of 0, FIGURE 5 is a cross sectional view of the radome-lens at a scan an~le o~ 45, and FIGURE 6 is a cross sectional view of the radome-20 lens at a scan angle of 90~.
DETAIL~D DESCRIPTION OF A PREFERRED EMBODIME~T
-FIGUR~S 1 to 3 illustrate the present invention ~0 in its simplest form. This embodiment will be referred 25 to as a fisheye lens. The fish-eye lens is in the form of a shell 12 formed of dielectric material and includes an outer surface 14 in the form of a small circle defined by a sphere and â plane 16 intersecting the sphere. The outer surface defines a central or broad-30 side a~is 18 which is normal to plane 16 and extenclsthrough the center 20 of the sphere. An opening 22 is formed at one end of the shell for insertion of an antenna (not shown) into the shell. The aperture antenna is presumed to be capable of receiving parallel 35 or substantially parallel rays by proper phasing or focussing. The shell further includes an inner .
....
. . .
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~26~25'7~L
spherical surface 24 centered at a second center 26 slightly spaced from center 20 along the broadside axis toward the outer surface as shown. Reference numeral 28 designates a ground plane.
05 If the aperture antenna is pointed at 0 from the broadside a~is, as shown in FIGURE 1, it receives parallel rays from outside the lens a-t a 0 scan angl~e.
However~ if the aperture antenna is pointed at 34 from the lens axis~ as shown in FIGURE 2, it receives lO parallel rays from outside the lens at a 45~ scan angle.
This means that there is an average bending of 11 ana the scan angle of the receiving antenna is amplified from 34 inside the lens to 45 outside the lens. If the aperture antenna is pointed at 73 from the lens 15 axis, as shown in FIGURE 3, i~ receives parallel rays from outside the lens at a 90 scan angle. Thus, there is an average bending of 17 and the scan angle of the receiving antenna is amplified Erom 73 inside the lens to 90 outside the lens. It will be seen therefore that 20 the fish-eye lens functions as a negative lens in that it forms a wide angle lens for scanning angle amplifi-cation.
It will be seen that the fish-eye lens is effect-ively a radome for the aperture antenna inside it.
25 Unlike the radome, however, it is capable of bending incident rays to a smaller scanning angle for the aperture antenna therein. As shown in FIGURE 3, for a 90 scanning angle, the bending raises the locations o the paxallel ray bundle with respect to the ground plane 30 so that it rises above the blockage due to the grouncl plane. The antenna beam widens because of foreshorten-ing of the planar array at large scanning angles. The widening is most severe at 90 scanning angles. ~s the lens bends the rays so that they arrive at the planar 35 array at 73 instead of 90, the beam widening is substantially reduced. When the scanning angle reaches 90 from broadside, a dual polarization phased array is reduced to one polarization. As the lens bends the .-'. ::
,.
~,2S~
rays, the 9~ rays do not reach the phase array inside the lens at 90~ but rather at about 73 and thus the dual polarization capability inside the lens is partial-ly maintained.
05 Notwithstanding the aforementioned advantages of a fisheye lens, its base is necessarily very thick. Thick bases cause the lens to be excessively heavy, weighing about 100 Kg for antenna specifications discussed later, and to have very high insertion losses for rays passing 10 through the thick base. The propagation loss in the dielectric of the lens could be 6 dB or more. These drawbacks can be corrected by zoning as explained below.
In addition to reduction in weight and inser-tion losses, zoning substantially corrects the spherical aberration.
The radome-lens illustrated in FIGURES 4 to 6 is a zoned fish-eye lens. In the terminology of spherical trigonometry, a zone is the surface portion of a sphere included between two parallel planes cutting the sphere.
The radome-lens 50 is a shell 52 of dielectric 20 material. At least a portion of the outer surface 54 of the shell is in the form of a small circle which defines a central or broadside axis 56 and is centered at 58.
An opening 60 is formed at one end of the shell for insertion of an antenna into the shell.
The inner surface 62 of the shell is formed with a spherical cap portion 64 at the end of the inner surface remote from the opening and a plurality of zones 66 extending from the cap toward the opening. The cap and zones are concentrically disposed about axis 56 ancl 30 centered at a second center 68 which lies on the central axis adjacent center 58 but spaced therefrom in the broadside direction. The zones are disposed between center 68 and cap 64, although further zones could be included toward the base end. As shown in FIGURES ~ to 35 6, the radius of the zones are larger by a predeterminecl amount than their adjacent zones remote from the opening. The cap and zone are separated from their adjacent zones by frusto-conical surfaces 70 which '` "~D
.
~257.
converge at center 68. The shell is constructed so that the ground plane is disposed between centers 58 and 68.
~ s long as the zoned surfaces are spherical surfaces centered at the same origin as the inner 05 spherical surface of the of the fish-eye lens, the central ray still suffers no refraction. Further, as long as the steps between the zones are along a radial surface from the common origin of the zoned surfaces, the c~ntral ray suffers no shadowiny effect from the 10 steps. Other rays suffer a little refraction and shadowing but these are only second order effects.
As shown in FIGURE 4, the central ray of the incident parallel rays passes through the origin of the inner spherical surface. This means that the central 15 ray is perpendicular to the inner spherical surface ancL
therefore is not refracted. FIGURES 5 and 6 illustrate the incident rays at angles of 45 and 90, respective--ly. At these scan angles, the optical characteristics of the radome-lens are substantially the same as those 20 of the Ei.sh-eye lens ~iscussed earli.er.
The step height, h, between the zones is that which would induce a wavelength path difference. More specifically, h = ~/2 ~1) ( r) -1 where ~O is the desired wavelength of the incident ray and r is the relative permittivity of the lens. At frequencies other than the central frequency, fO, there 30 will be a phase error in a step given by ~ = 2~(~f - 1) (2) ., ,i .. . .
. . .:
,, , .
:
; ~ :
~2~i;7~
The phase error accumulates for successive ~oning steps.
Thus for N zonesl the phase error is ~ = 2~N( ff - 1) (3) 05 o The radome lens can also be configured for two frequencies fl and f2 wherein the f2 is almost twice fl, i.e., f2 = 2fl + ~f (~) where ~f is a small increment of frequency. If fO is the frequency that results in exactly one wavelength dif:Eerence in a step height h, then, from (1), h = c (r)l/2 -1 where c is the speed of light and ~r is the relative permittivity of the lens.
fl ~ fO~ the phase error of the step is:
~1= 2~ (6) fo 25 and the phase error in f2 is ~2= 2~( 1 - 1) ~7 F
Whether ~f is positive or negative, the phase errors in 30 the two frequencies must be opposite to each other3 i.e.:
B~CKGROUND OF THE INVE~TION
A radome is a thin shell of uniforM thickness which 05 is normally used to house and protect an antenna from the weather. Because of the interpositlon of the radome between the antenna and outside space from which the antenna is to receive or transmit signals, the radome always adds some refraction and insertion losses to the 10 signal and, as a consequence, the radome has heretofore been regarded as a hinderance to the radiation perform-ance of the antenna.
A further problem with which the present invention is concerned relates to the number of antennas which are 15 employed to cover the whole spherical sky, and, parti-cularly, with minimizing the number oE antennas requirecl for this purpose. Assuming that each an-tenna is mounted on an altitude-azimuth mount or its equivalent, the scanning area oE each antenna is a circular region. The 20 term --circular region-- is referable to a --small circle-- which, in the terminology of spherical trigono-metry, is the intersection of a sphere and a plane cutting the sphere.
The largest circular region is the spherical sky ~5 itself. It is not possible for a single antenna to scan the entire sky because of blockage by the antenna mount.
The next largest region, then, is a hemispherical region. Two antennas, ~ith their broadside directions pointing in opposite directions~ are required to scan 30 the entire sky, provided that each antenna is capable of scanning up to 90 from the broadside directicn.
However, if such antennas are not available, it can be shown that four antennas would be required to cover the entire sky without holes with their broadside directions 35 being the normals of the surfaces of an equilatera]
tetrahedron. In that case, the scanning angle required from each antenna must range between 0 to 70.5, which is not significan-tly reduced from the 90 required for a "
:
- ~
.. : . , ~2~
two antenna configuration. Thu~s, it is clearly highly desirable to provide an ant~nna which is capable of scanning up to 90.
SUMMARY OF THE INVENTION
It has been found that a radome can be configured in such a manner that it not only eliminates the refraction problem discussed earlier but employs that characteristic of radomes to amplify transmitted and/or received rays to enable the scanning of the whole sky with two antennasO
In accordance with the present invention there is provided a radome-lens comprising a shell of dielectric material having an outer surface in the form o~ a small circle defined by a sphere and a plane intersecting the sphere, an opening at one end of the shell for reception of an antenna therein, the surface having a central axis which is normal to the plane and extends through the center of the sphere, and an inner surface having a spherical port:Lon centered at a second center disposed along the axis adjacent the first mentioned center but spaced toward the outer surface and including a plurality of æones concentrically disposed along said axis, each said zone being centered at said second center.
When so constructed, the present invention functions as a radome in the sense that it houses and protects an antenna in the usual manner. It also functions as a lens in the sense that it amplifies the scan angle of the antenna from an angle of less than 90 to 90.or more without much spherical aberration. Such amplification avoids ground plane obstruction and, accordingly, only two antennas, each e~uipped with the radome-lens of the present invention are required to cover the whole sky. In an aperture planar phased array with electronic scanning, such amplification enables the array to retain substantial antenna gain and partial dual polarization capability The aperture antenna could be a microstrip antenna array scanned completely electronically or a reflector scanned completely mechanically, or other hybrid systems _ 3 _ ~6~
of microstrip antennas and reflectors with partial electronic and partial mechanical scanning.
BRIEF DESCRIPTION OF THE DRAWI~GS
-05 These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:
FIGURE 1 is a cross sectional view of a fish-eye 10 lens at a scan angle of 0, FIGURE 2 is a cross sectional view of a fish-eye lens at a scan angle of 45~, F~GURE 3 is a cross sectional view of a fish-eye lens at a scan angle of 90~, FI~URE 4 is a cross sectional view of the radome-lens at a scan angle of 0, FIGURE 5 is a cross sectional view of the radome-lens at a scan an~le o~ 45, and FIGURE 6 is a cross sectional view of the radome-20 lens at a scan angle of 90~.
DETAIL~D DESCRIPTION OF A PREFERRED EMBODIME~T
-FIGUR~S 1 to 3 illustrate the present invention ~0 in its simplest form. This embodiment will be referred 25 to as a fisheye lens. The fish-eye lens is in the form of a shell 12 formed of dielectric material and includes an outer surface 14 in the form of a small circle defined by a sphere and â plane 16 intersecting the sphere. The outer surface defines a central or broad-30 side a~is 18 which is normal to plane 16 and extenclsthrough the center 20 of the sphere. An opening 22 is formed at one end of the shell for insertion of an antenna (not shown) into the shell. The aperture antenna is presumed to be capable of receiving parallel 35 or substantially parallel rays by proper phasing or focussing. The shell further includes an inner .
....
. . .
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~26~25'7~L
spherical surface 24 centered at a second center 26 slightly spaced from center 20 along the broadside axis toward the outer surface as shown. Reference numeral 28 designates a ground plane.
05 If the aperture antenna is pointed at 0 from the broadside a~is, as shown in FIGURE 1, it receives parallel rays from outside the lens a-t a 0 scan angl~e.
However~ if the aperture antenna is pointed at 34 from the lens axis~ as shown in FIGURE 2, it receives lO parallel rays from outside the lens at a 45~ scan angle.
This means that there is an average bending of 11 ana the scan angle of the receiving antenna is amplified from 34 inside the lens to 45 outside the lens. If the aperture antenna is pointed at 73 from the lens 15 axis, as shown in FIGURE 3, i~ receives parallel rays from outside the lens at a 90 scan angle. Thus, there is an average bending of 17 and the scan angle of the receiving antenna is amplified Erom 73 inside the lens to 90 outside the lens. It will be seen therefore that 20 the fish-eye lens functions as a negative lens in that it forms a wide angle lens for scanning angle amplifi-cation.
It will be seen that the fish-eye lens is effect-ively a radome for the aperture antenna inside it.
25 Unlike the radome, however, it is capable of bending incident rays to a smaller scanning angle for the aperture antenna therein. As shown in FIGURE 3, for a 90 scanning angle, the bending raises the locations o the paxallel ray bundle with respect to the ground plane 30 so that it rises above the blockage due to the grouncl plane. The antenna beam widens because of foreshorten-ing of the planar array at large scanning angles. The widening is most severe at 90 scanning angles. ~s the lens bends the rays so that they arrive at the planar 35 array at 73 instead of 90, the beam widening is substantially reduced. When the scanning angle reaches 90 from broadside, a dual polarization phased array is reduced to one polarization. As the lens bends the .-'. ::
,.
~,2S~
rays, the 9~ rays do not reach the phase array inside the lens at 90~ but rather at about 73 and thus the dual polarization capability inside the lens is partial-ly maintained.
05 Notwithstanding the aforementioned advantages of a fisheye lens, its base is necessarily very thick. Thick bases cause the lens to be excessively heavy, weighing about 100 Kg for antenna specifications discussed later, and to have very high insertion losses for rays passing 10 through the thick base. The propagation loss in the dielectric of the lens could be 6 dB or more. These drawbacks can be corrected by zoning as explained below.
In addition to reduction in weight and inser-tion losses, zoning substantially corrects the spherical aberration.
The radome-lens illustrated in FIGURES 4 to 6 is a zoned fish-eye lens. In the terminology of spherical trigonometry, a zone is the surface portion of a sphere included between two parallel planes cutting the sphere.
The radome-lens 50 is a shell 52 of dielectric 20 material. At least a portion of the outer surface 54 of the shell is in the form of a small circle which defines a central or broadside axis 56 and is centered at 58.
An opening 60 is formed at one end of the shell for insertion of an antenna into the shell.
The inner surface 62 of the shell is formed with a spherical cap portion 64 at the end of the inner surface remote from the opening and a plurality of zones 66 extending from the cap toward the opening. The cap and zones are concentrically disposed about axis 56 ancl 30 centered at a second center 68 which lies on the central axis adjacent center 58 but spaced therefrom in the broadside direction. The zones are disposed between center 68 and cap 64, although further zones could be included toward the base end. As shown in FIGURES ~ to 35 6, the radius of the zones are larger by a predeterminecl amount than their adjacent zones remote from the opening. The cap and zone are separated from their adjacent zones by frusto-conical surfaces 70 which '` "~D
.
~257.
converge at center 68. The shell is constructed so that the ground plane is disposed between centers 58 and 68.
~ s long as the zoned surfaces are spherical surfaces centered at the same origin as the inner 05 spherical surface of the of the fish-eye lens, the central ray still suffers no refraction. Further, as long as the steps between the zones are along a radial surface from the common origin of the zoned surfaces, the c~ntral ray suffers no shadowiny effect from the 10 steps. Other rays suffer a little refraction and shadowing but these are only second order effects.
As shown in FIGURE 4, the central ray of the incident parallel rays passes through the origin of the inner spherical surface. This means that the central 15 ray is perpendicular to the inner spherical surface ancL
therefore is not refracted. FIGURES 5 and 6 illustrate the incident rays at angles of 45 and 90, respective--ly. At these scan angles, the optical characteristics of the radome-lens are substantially the same as those 20 of the Ei.sh-eye lens ~iscussed earli.er.
The step height, h, between the zones is that which would induce a wavelength path difference. More specifically, h = ~/2 ~1) ( r) -1 where ~O is the desired wavelength of the incident ray and r is the relative permittivity of the lens. At frequencies other than the central frequency, fO, there 30 will be a phase error in a step given by ~ = 2~(~f - 1) (2) ., ,i .. . .
. . .:
,, , .
:
; ~ :
~2~i;7~
The phase error accumulates for successive ~oning steps.
Thus for N zonesl the phase error is ~ = 2~N( ff - 1) (3) 05 o The radome lens can also be configured for two frequencies fl and f2 wherein the f2 is almost twice fl, i.e., f2 = 2fl + ~f (~) where ~f is a small increment of frequency. If fO is the frequency that results in exactly one wavelength dif:Eerence in a step height h, then, from (1), h = c (r)l/2 -1 where c is the speed of light and ~r is the relative permittivity of the lens.
fl ~ fO~ the phase error of the step is:
~1= 2~ (6) fo 25 and the phase error in f2 is ~2= 2~( 1 - 1) ~7 F
Whether ~f is positive or negative, the phase errors in 30 the two frequencies must be opposite to each other3 i.e.:
2 (8) , . ,, ~-~L2~2~
Substituting (6) and (7) into (8), and rearranging the -terms:
~o = (fl + f2)/3 (9) 05 Substitu-ting (9) into (5), h 3c . 1/2 (10) fl f2 (~r} -1 10 Based on (9) and (10) and in terms of f1 only f 3fo 15 With (11) into (6), the phase error is ~1 = ~ 2~ (~f/3fO) (1~) Substituting (9) into (12), the absolute value of the phase error per step is = 2~(~f/f + f )) (13) Since the phase error accumulates for a sequence of step, then for N steps, ~f (14) fl + f2 The radome-lens amplifies the scanning angle from more or less parallel rays within the lens enclosed area to the parallel rays without. As observed in FIGURE 4-6, such parallel rays within the radome-lens 35 can be incident on any aperture antenna with the proper phasing or focussing. Therefore, the design of the radome-lens i6 basically independent of the antenna within it.
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5 d:~ -g EXA_PLE
The requirements of the radome-lens may be as follows:
(a) The radome-lens must be large enough to accommodate an aperture antenna 05 with about 40 dB gain at 43.6 GHz or 34 dB at 21.15 GHz for all scanning angles.
(b) The radome-lens must be able to accommodate rays down to 90 ~- scanning angle without obstruction from the ground plane.
(c) the radome-lens must be light weight.
Using the aforementioned formulas, as shown hereinafter, 15 the results are as follows:
(1) The radome-lens has the shape illustrated in FIGURES 4 to 6.
(2) The outer radius o:E the radome-lens is 2.85 cm.
Substituting (6) and (7) into (8), and rearranging the -terms:
~o = (fl + f2)/3 (9) 05 Substitu-ting (9) into (5), h 3c . 1/2 (10) fl f2 (~r} -1 10 Based on (9) and (10) and in terms of f1 only f 3fo 15 With (11) into (6), the phase error is ~1 = ~ 2~ (~f/3fO) (1~) Substituting (9) into (12), the absolute value of the phase error per step is = 2~(~f/f + f )) (13) Since the phase error accumulates for a sequence of step, then for N steps, ~f (14) fl + f2 The radome-lens amplifies the scanning angle from more or less parallel rays within the lens enclosed area to the parallel rays without. As observed in FIGURE 4-6, such parallel rays within the radome-lens 35 can be incident on any aperture antenna with the proper phasing or focussing. Therefore, the design of the radome-lens i6 basically independent of the antenna within it.
.~ ~
, `
`:
5 d:~ -g EXA_PLE
The requirements of the radome-lens may be as follows:
(a) The radome-lens must be large enough to accommodate an aperture antenna 05 with about 40 dB gain at 43.6 GHz or 34 dB at 21.15 GHz for all scanning angles.
(b) The radome-lens must be able to accommodate rays down to 90 ~- scanning angle without obstruction from the ground plane.
(c) the radome-lens must be light weight.
Using the aforementioned formulas, as shown hereinafter, 15 the results are as follows:
(1) The radome-lens has the shape illustrated in FIGURES 4 to 6.
(2) The outer radius o:E the radome-lens is 2.85 cm.
(3) The number of steps of 20ning is 5.
(4) The step height is 1.38 cm.
(5) The most severe phase error is (for the outer ray at 90 scan) is 36.1.
(6) The dielectric volume of the radome-lens is 4921 cml.
(7) The weight of the radome-lens is 9.8 Kg, for a specific gravity of 2.
(8) The dielectric constant is 4.
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(9) The mos-t severe insertion loss due to reElection of surfaces is 4 dB
and the average loss is 2 dB.
In order to satisfy requirement (a), the 40 dB
S gain means that the directivity, D, must be 104. Since D = 4~A~ = 4~(~R~ ) (15) where A~ is the aperture area in wave]ength square and R~2 is the radius in wavelength of the aperture antenna.
L0 Assuming the aperture antenna to be circular, then R~ = (10,000/4~ ) / (16) = 15.92~ ~ 16~
At f2 = 43.6 GHz, the wavelength ~2 = 0.69 cm, and R~ of -the aperture is translated to R = 15.92~ x 0.69 cm = 10.98 cm (17) If R i9 taken as 1.6 division widths of parallel rays in FIGURE 6 for scanning to 90, the required radius Router of the outer sphere of the radome-lens is about 3.33 divisions or RoUter = (3.33/1.6) x 10.98 cm = 22.85 cm (18) i.e., a diameter of 45.70 cm. It is to be noted a division width is taken to be arbitrary and, inasmuch as it is used as a ratio, it is not important.
STEPS OF ZONING AND STEP HEIGHT
By measuring the original fish-eye lens of FIGURB 3, the thickest part of the lens that a 3.2 divisions wide parallel ray bundle passes is about 1.0 35 division. One division translates to 10~2 at 43.6 GHz and into a thickness, T, of 6.9 cm.
. ., :
,~
.
:
2~
Let ~r=4 for the lenses of FIGURES 3 and 6. Then, according to equation (9), the zoning step height is h = 3 x 3 x 10 - = 1 39 cm (19) 05 (43.6 ~ 21.15) x 103 The number of steps, N, between the zones is given by N = T/h = 6.9/1.39 = 5 (20) This is the number of steps shown in FIGURES 4 to 6.
MOST SEVERE PHASE ERROR
The phase errors for both frequencies are equal 15 except for a change of signs. The most severe phase error at the edge of the lens is, according to equation (13), (f2 2fl) t21) 20 ~ =
tfl ~ f2) = 0.63 rads = 36.1.
It will be appreciated by those skilled in thls art that such an error is not a major problem.
VOLUME OF THE RADOME-LENS
From the step size in equation (18), it ls e~pected that the average thickness o~ the lens is about 1.5 cm.
Therefore, the dielectric volume of the radome-lens ls V = 2~R2 x 1.5 cm ~ 4921 cm2 , ,, . . . . ; , ~ :
. :, , . ~ '~ :'`''~''`
.: :
WEIGHT OF THE RADOME-LENS
If the speciic gravity of the dielectric is 2, then the mass of the lens is 05 M = 2 x 4921 = 9842 gm = 9.84 Kg = 21.71 lbs.
INSERTION LOSS
The insertion loss is assumed to be a result of reflection from the surface. Based on sample calculat-ions, it is assumed that the insertion loss can not be worse than 4 dB, and more probably 2 dB.
. . .
. .~ ~ ,. . .
and the average loss is 2 dB.
In order to satisfy requirement (a), the 40 dB
S gain means that the directivity, D, must be 104. Since D = 4~A~ = 4~(~R~ ) (15) where A~ is the aperture area in wave]ength square and R~2 is the radius in wavelength of the aperture antenna.
L0 Assuming the aperture antenna to be circular, then R~ = (10,000/4~ ) / (16) = 15.92~ ~ 16~
At f2 = 43.6 GHz, the wavelength ~2 = 0.69 cm, and R~ of -the aperture is translated to R = 15.92~ x 0.69 cm = 10.98 cm (17) If R i9 taken as 1.6 division widths of parallel rays in FIGURE 6 for scanning to 90, the required radius Router of the outer sphere of the radome-lens is about 3.33 divisions or RoUter = (3.33/1.6) x 10.98 cm = 22.85 cm (18) i.e., a diameter of 45.70 cm. It is to be noted a division width is taken to be arbitrary and, inasmuch as it is used as a ratio, it is not important.
STEPS OF ZONING AND STEP HEIGHT
By measuring the original fish-eye lens of FIGURB 3, the thickest part of the lens that a 3.2 divisions wide parallel ray bundle passes is about 1.0 35 division. One division translates to 10~2 at 43.6 GHz and into a thickness, T, of 6.9 cm.
. ., :
,~
.
:
2~
Let ~r=4 for the lenses of FIGURES 3 and 6. Then, according to equation (9), the zoning step height is h = 3 x 3 x 10 - = 1 39 cm (19) 05 (43.6 ~ 21.15) x 103 The number of steps, N, between the zones is given by N = T/h = 6.9/1.39 = 5 (20) This is the number of steps shown in FIGURES 4 to 6.
MOST SEVERE PHASE ERROR
The phase errors for both frequencies are equal 15 except for a change of signs. The most severe phase error at the edge of the lens is, according to equation (13), (f2 2fl) t21) 20 ~ =
tfl ~ f2) = 0.63 rads = 36.1.
It will be appreciated by those skilled in thls art that such an error is not a major problem.
VOLUME OF THE RADOME-LENS
From the step size in equation (18), it ls e~pected that the average thickness o~ the lens is about 1.5 cm.
Therefore, the dielectric volume of the radome-lens ls V = 2~R2 x 1.5 cm ~ 4921 cm2 , ,, . . . . ; , ~ :
. :, , . ~ '~ :'`''~''`
.: :
WEIGHT OF THE RADOME-LENS
If the speciic gravity of the dielectric is 2, then the mass of the lens is 05 M = 2 x 4921 = 9842 gm = 9.84 Kg = 21.71 lbs.
INSERTION LOSS
The insertion loss is assumed to be a result of reflection from the surface. Based on sample calculat-ions, it is assumed that the insertion loss can not be worse than 4 dB, and more probably 2 dB.
. . .
. .~ ~ ,. . .
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A radome-lens comprising:
a shell of dielectric material having an outer surface in the form of a small circle defined by a sphere and a plane intersecting said sphere, an opening at one end of said shell for reception of an antenna therein, said surface having a central axis which is normal to said plane and extends through the center of said sphere, and an inner surface having a spherical portion centered at a second center disposed along said axis between said first mentioned center and said outer surface and including a plurality of zones concentrically disposed along said axis, each said zone being centered at said second center.
a shell of dielectric material having an outer surface in the form of a small circle defined by a sphere and a plane intersecting said sphere, an opening at one end of said shell for reception of an antenna therein, said surface having a central axis which is normal to said plane and extends through the center of said sphere, and an inner surface having a spherical portion centered at a second center disposed along said axis between said first mentioned center and said outer surface and including a plurality of zones concentrically disposed along said axis, each said zone being centered at said second center.
2. A radome-lens as defined in claim 1, wherein the radius of each said zone being incrementally larger than its adjacent zone remote from said end.
3. A radome-lens as defined in claim 1, wherein adjacent zones are separated by a frusto-conical surface which converges at said second center.
4. A radome-lens as defined in claim 1, wherein the radial height, h, of each said frusto-conical surface is given by:
(1) wherein .lambda.o is the designed wavelength of the incident or transmitted wave, and .epsilon.r is the relative permittivity of the lens.
(1) wherein .lambda.o is the designed wavelength of the incident or transmitted wave, and .epsilon.r is the relative permittivity of the lens.
5. A radome-lens for housing an antenna and amplifying transmitted or received rays, comprising:
a shell of dielectric material, said shell having an outer surface, at least a portion of said outer surface being in the form of a small circle defined by a sphere and a plane intersecting said sphere, said outer surface defining a central axis normal to said plane and extending through the center of said sphere, an opening at one end of said shell for reception of an antenna therein, and an inner surface having a spherical cap portion at the end of said inner surface remote from said opening and a plurality of zones extending from said cap toward said opening, said cap and each said zone being concentrically disposed about said axis and centered at a second center, said second center lying on said central axis between said first mentioned center and said outer surface, and said zones being disposed between said second center and said cap, the radius of each said zone being larger by a predetermined amount than its adjacent zone remote from said opening, and said cap and each said zone being separated from its adjacent zones by a frusto-conical surface which converges at said second center.
a shell of dielectric material, said shell having an outer surface, at least a portion of said outer surface being in the form of a small circle defined by a sphere and a plane intersecting said sphere, said outer surface defining a central axis normal to said plane and extending through the center of said sphere, an opening at one end of said shell for reception of an antenna therein, and an inner surface having a spherical cap portion at the end of said inner surface remote from said opening and a plurality of zones extending from said cap toward said opening, said cap and each said zone being concentrically disposed about said axis and centered at a second center, said second center lying on said central axis between said first mentioned center and said outer surface, and said zones being disposed between said second center and said cap, the radius of each said zone being larger by a predetermined amount than its adjacent zone remote from said opening, and said cap and each said zone being separated from its adjacent zones by a frusto-conical surface which converges at said second center.
6. A radome-lens as defined in claim 5, wherein the radial height, h, of each said frusto-conical surface is given by:
(1) wherein .lambda.o is the design wavelength of the incident or transmitted wave, and .epsilon.r is the relative permittivity of the lens.
(1) wherein .lambda.o is the design wavelength of the incident or transmitted wave, and .epsilon.r is the relative permittivity of the lens.
7. A radome-lens as defined in claim 5, said radome-lens being adapted for reception or transmission of frequencies f1 and f2 wherein f2 is almost twice f1, i.e., f2 = 2f1 + .DELTA.f (4) the radial height, h, of each said frusto-conical surface is given by:
(10) wherein c = speed of light, .epsilon.r= the relative permittivity of said lens.
(10) wherein c = speed of light, .epsilon.r= the relative permittivity of said lens.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000524264A CA1262571A (en) | 1986-12-09 | 1986-12-09 | Radome-lens ehf antenna development |
| US07/129,626 US4872019A (en) | 1986-12-09 | 1987-12-07 | Radome-lens EHF antenna development |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000524264A CA1262571A (en) | 1986-12-09 | 1986-12-09 | Radome-lens ehf antenna development |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1262571A true CA1262571A (en) | 1989-10-31 |
Family
ID=4134470
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000524264A Expired CA1262571A (en) | 1986-12-09 | 1986-12-09 | Radome-lens ehf antenna development |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4872019A (en) |
| CA (1) | CA1262571A (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5121129A (en) * | 1990-03-14 | 1992-06-09 | Space Systems/Loral, Inc. | EHF omnidirectional antenna |
| US6011524A (en) * | 1994-05-24 | 2000-01-04 | Trimble Navigation Limited | Integrated antenna system |
| US5691736A (en) * | 1995-03-28 | 1997-11-25 | Loral Vought Systems Corporation | Radome with secondary heat shield |
| US5652631A (en) * | 1995-05-08 | 1997-07-29 | Hughes Missile Systems Company | Dual frequency radome |
| DE19621075C1 (en) * | 1996-05-24 | 1998-02-12 | Siemens Ag | Housing for a distance measuring device in a motor vehicle |
| DE19741081C1 (en) * | 1997-09-18 | 1999-03-18 | Bosch Gmbh Robert | Method of making an antenna lens |
| US6639567B2 (en) * | 2001-09-14 | 2003-10-28 | Raytheon Company | Low radar cross section radome |
| US7042407B2 (en) * | 2003-08-14 | 2006-05-09 | Andrew Corporation | Dual radius twist lock radome and reflector antenna for radome |
| US8692172B2 (en) * | 2009-04-21 | 2014-04-08 | Raytheon Company | Cold shield apparatus and methods |
| JP5616103B2 (en) * | 2010-04-09 | 2014-10-29 | 古野電気株式会社 | Antenna device and radar device |
| JP5603636B2 (en) * | 2010-04-09 | 2014-10-08 | 古野電気株式会社 | Radome, antenna device, and radar device |
| EP2754205B1 (en) * | 2011-09-08 | 2023-10-04 | Intel Corporation | Overlapped and staggered antenna arrays |
| US9985347B2 (en) * | 2013-10-30 | 2018-05-29 | Commscope Technologies Llc | Broad band radome for microwave antenna |
| US11129077B2 (en) * | 2015-07-10 | 2021-09-21 | Comcast Cable Communications, Llc | Directional router communication and tracking |
| JP6643203B2 (en) * | 2016-07-26 | 2020-02-12 | 株式会社Ｓｏｋｅｎ | Radar equipment |
| US11894612B2 (en) * | 2022-02-25 | 2024-02-06 | Qualcomm Incorporated | Antenna array having a curved configuration |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3430245A (en) * | 1965-05-19 | 1969-02-25 | Whittaker Corp | Spherical reflector with lens to convert to parabolic surface |
| US3787872A (en) * | 1971-08-10 | 1974-01-22 | Corning Glass Works | Microwave lens antenna and method of producing |
| US3886561A (en) * | 1972-12-15 | 1975-05-27 | Communications Satellite Corp | Compensated zoned dielectric lens antenna |
| US4321604A (en) * | 1977-10-17 | 1982-03-23 | Hughes Aircraft Company | Broadband group delay waveguide lens |
| US4156878A (en) * | 1978-01-25 | 1979-05-29 | The United States Of America As Represented By The Secretary Of The Air Force | Wideband waveguide lens |
| US4220957A (en) * | 1979-06-01 | 1980-09-02 | General Electric Company | Dual frequency horn antenna system |
| FR2492142A1 (en) * | 1979-06-29 | 1982-04-16 | Thomson Csf | ACOUSTIC ANTENNA WITH GEODESIC LENS |
| US4769646A (en) * | 1984-02-27 | 1988-09-06 | United Technologies Corporation | Antenna system and dual-fed lenses producing characteristically different beams |
| JPS62189803A (en) * | 1986-02-14 | 1987-08-19 | Matsushita Electric Works Ltd | Antenna dome |
-
1986
- 1986-12-09 CA CA000524264A patent/CA1262571A/en not_active Expired
-
1987
- 1987-12-07 US US07/129,626 patent/US4872019A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| US4872019A (en) | 1989-10-03 |
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