US2573401A - Louver antenna - Google Patents

Description

Oct. 30, 1951 P. s. CARTER I 2,573,401

LOUVER ANTENNA Filed NOV. 13, 1947 INVENTOR PHILIP S. CARTER BY AT RNEY Patented Oct. 30, 1951 LOUVER ANTENNA Philip S. Carter, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application November 13, 1947, Serial No. 785,584

3 Claims.

provision of the antenna system as aforesaid which is adapted to be mounted at the front end of a vehicle.

The foregoing objects and others which may appear from the following detailed description are attained by providing a wedge radiator having a plurality of wedge directors and reflectors associated therewith whereby there results a highly directive radiation pattern inclined at a small angle to the surface of the sheet on which the wedges are mounted. Ordinarily the antenna as described above is utilized in pairs, one mounted on each side of the forward end of the hull or body of an airplane or other vehicle. The metallic body of the plane for which this antenna was devised slopes inwardly at said location. Due to the tilt of the radiation away from the plane of the radiator the resultant radiation patterns measured with respect to the longitudinal axis of the vehicle provide a ratio of cross-over amplitude to maximum amplitude of the two patterns in the dead-ahead direction providing optimum results in radio homing service.

The present invention will be more clearly understood by reference to the following detailed description which is accompanied by a drawing in which: I

Figure 1 is a plan view of a portion of an airplane showing the mounting of the antennasof the present invention at the forward end of the hull of the airplane;

Figure 2 is a perspective View of the antenna of the present invention partly i n section, while Figure 3 is a plan view of an antenna arrangement as in Figure 2, mounted on a conductive plane sheet for purposes of testing, and

Figures 4 and 5 are radiation patterns obtained with the antenna of Figures 2 and 3.

Referring now to the drawing, Figure 1 shows an airplane having a hull I0. As indicated by of the hull slope inwardly at an angle of about 6 degrees from the longitudinal axis of hull [0 at the point where the antennas 23 are mounted. The preferred form of radiation pattern to be obtained from the antennas is indicated bythe curves l3 and I5 drawn at the nose of the hull Hi. It will be noted that the axes of the two radiation patterns are inclined at an angle at about 12 degrees from dead-ahead and that the cross-over point of the two patterns occurs exactly on the longitudinal axis of hull H) at about the optimum drop from the maximum radiation amplitude.

The antennas 2i] of Figure 1 are shown in perspective and partly in section in Figure 2. The section is taken along line 2-2 of Fig. 3 along the longitudinal axis of the antenna. In

this figure, the hull of the plane is indicated by metallic ground sheet II. On this ground sheet are mounted a number of inclined metallic flaps 2|, 22, 23, 26 and 25. Each of these flaps is attached. to the ground plate ll along one edge and tilted up at a small angle 0. Thus, generally the arrangement has the appearance of a louvred metal sheet. Preferably the wedgeshaped openings at the ends of the flaps are closed by end walls 3!, 32, 33, 34 and 35 which may be separate conductive triangles weldedor soldered in place. Alternatively they may be formed as integral portions of the flaps 21 to 25 inclusive. Preferably each of the louvres 2! to 25 has a width of the order of .34 Wavelength and a length of the order of of a Wavelength. The louvres are overlapped to such an extent that the free surface of each has a width of the order of of the operating wavelength. Louvre 22 is energized from a suitable source of radio frequency energy by transmission line TL having its inner conductor I6 connected to the inner surface of the sheet and the sheath ilconnected to the metallic ground plate I i. Radiation takes place from the wedge formed between louvre 22 and plate II in somewhat the same way as described in my prior filed application, Serial No. 488,584, filed May 26, 1943 (Patent 2,425,303). The radiation is concentrated in the desired direction due to action of the wedge shaped cavity beneath louvre 2| acting as a reflector andthe wedge shaped cavities formed beneath flaps 23, 24 and 25 acting as directors. The parasitically energized directors and reflector are tuned for proper operating conditions by capacitive tuning means along their free edges. A simple form of capacity tuning means which has been used the dimension marks on the figure, the sides 56 and which has proved satisfactory includes a metallic disc 4| mounted on a screw 42 passing through a threaded hole near the edge of each of the parasitically energized radiators. The effective capacity between the free edges of the flaps 2 l,

23, 24, 25 and the plates which they overlap may be controlled by moving discs 4| more closely adjacent to or further away from the flap over which they lie. In order to protect the antenna, as so far described, from the efiects of weather and reduce adverse effects upon the streamlining of high-speed vehicles, the entire assembly.

may be covered by a formed sheet of insulating material 50 forming a generally elongated, flattened dome over the antenna assembly; If desired, holes such as that indicated by 51 may be provided for the entrance of adjusting means for adjusting the screws 42. If desired, after the proper adjustments have been made, holes 5| may be blocked with insulating plugs or insulatingcement pressedinto the holes.

Figure 3 show a plane View of an antenna as described with reference to Figure 1 which has actually been constructed and tested. The metallic plate H simulating the housingof the airplane on which it is mounted has, as is shown in Figure 1, an overall length of 6.6 wavelengths and a width of 2.8 wavelengths. I have deter mined that these dimensions are about the minimum sizes which provide an accurate picture or the radiation pattern to be obtained rom Such an antenna when it is actually mounted on the plane. The overall length of the antenna is, as indicated in Figure 3, of the order of 1.6 wavelengths. The antenna of Figure 3 produces radiation patterns in the horizontal and vertical planes as shown in Figures 4 and 5 by curves 60 and BI.

It will be noted that the maximum of the radiation pattern of Figure 4 falls along a line 62 making an angle of about 18 degrees from the zero axis. Thus, when this is mounted on the nose of a plane at a place where the hull curves inwardly at an angle of 6 degrees the resultant radiation patterns are tilted from the deadahead direction about 12 degrees.

It will be noted that there are no large secondary lobes of radiation in the pattern shown in Figure 1. Thus, there is no possibility of obtaining erroneous responses when the antenna is used in radar homing. Also, the curve SI of Figure 5 shows a highly symmetrical radiation pattern in the vertical plane with substantially no secondary lobes.

What is claimed is:

1. A sharply directive beam antenna including a conductive base plate having a number of radiator elements arranged in a line along the length of said plate, said radiators being in the form of a narrow conductive flap attached along one edge to said plate and forming a small angle with respect to the plate thereof, said elements having the width of substantially one third wavelength at the operating frequency and being overlapped so that the free width is substantially one quarter wavelength at the operating frequency and means for, energizing an intermediate one of said radiator elements including a two conductor line having one conductor connected to said base plate and the other to said fiap at a point intermediate its ends, one of the other 4 of said radiators serving as a parasitically energized reflector and the remainder of said radiators serving as parasitically energized director elements, said parasitically energized radiator elements being arranged to be tuned by capacitive tuning means, said tuning means including a threaded rod carried in an aperture near the free edge of each of said parasitically energized elements and carrying on its inner end a capacity disc and a flattened dome of insulating material covering the whole of said radiator elements and apertures in said covering for giving access to said tuning means.

2. A radar homing antenna arrangement including a pair of beam antennas mounted one on each side of an end of a vehicle body, said body having conductive areas at least where said antennas are mounted, each of said antennas including a number of radiator elements arranged in a line along the length of said vehicle body, said radiators each being in the form of a narrow conductive flap attached along one edge to said conductive area and forming a small angle with respect to the plane of said area and means energizing an intermediate one of said radiator elements including a two conductor transmission line having one conductor connected to said conductive area and the other to said flap, the remainder of said radiator elements being parasitically energized, the conductive areas of said body and said beam antennas cooperating to produce overlapping radiation patterns. 7

3. A radar homing antenna arrangement including a pair of beam antennas mounted one on each ide of an end of a vehicle body, said body having conductive areas at least where said antennas are mounted, each of said antennas including a number of radiator elements arranged in a line along the length of said vehicle body, said radiators each being in the form of a narrow conductive flap attached along one edge to said conductive area and forming a small angle with respect to the plane of said area and transducer apparatus coupled to an intermediate one of said radiator elements including a two conductor transmission line having one conductor connected to said conductive area and the other to said flap, the remainder of said radiator elements being parasitic-ally energized, the conductive areas of said body and said beam antennas cooperating to produce overlapping radiation patterns, whereby said transducer is adapted to respond to said overlapping radiation patterns to home said body.

PHILIP S. CARTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- OTHER REFERENCES 7 v p F. M. and Television, January 1946, page 45.

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