US2963702A - Microwave antenna - Google Patents

Description

v FM? ME w Dec. 6, 1960 G. A. WALTERS MICROWAVE ANTENNA Filed Oct. 18, 1 954 FIEJL 2 Sheets-Sheet 1 INVENTOR.

GLENN ,4; MLTERS rrow/5w vi RL UNE Dec. 6, 1960 e. A. WALTERS MICROWAVE ANTENNA Filed Oct. 18, 1954 2 Sheets-Sheet 2 FIIEl 7 'FIE E INVENTOR. GLENN 14. M ALTERS United States Patent C) MICROWAVE ANTENNA Glenn A. Walters, Atherton, Calif., assignor to The Dalmo Victor Company, San Carlos, Calif., a corporation of California Filed Oct. 18, 1954, Ser. No. 462,927

18 Claims. (Cl. 343-709) This invention relates to a microwave antenna and more specifically to a radar antenna for use on a submarine.

The principal object of this invention is to provide a microwave antenna having a broadband means for rotating the plane of polarization of a propagated wave.

Another object of this invention is to provide a micro- Wave antenna having a plurality of radiating sources wherein said sources are so arranged to reduce the etfects of scattered radiation resulting from said plurality of radiating sources.

A further object of this invention is to provide a microwave radar antenna having a parabolic feed to an array of sectoral horns.

A further object of this invention is to provide a microwave radar antenna having a parabolic feed to an array of sectoral horns wherein there is provided a broadband impedance match to both air and water, whereby the antenna may be submerged without damage to the transmitter.

A still further object of this invention is to provide a submarine radar antenna which is streamlined in its exterior configuration, whereby the drag of the antenna when submerged is reduced to a minimum.

Various other objects of the invention will be apparent from reading the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a perspective view of an antenna embodying the principles of my invention, certain parts being broken away to reveal details of other elements located therebehind.

Fig. 2 is a transverse section taken on line 2-2 of Fig. 1.

Fig. 3 is a partial section taken on line 3-3 of Fig. 1, showing a front view of a portion of the sectoral horn array.

Fig. 4 is a partial plan view of the elements shown in Fig. 3.

Fig. 5 is a sectional view taken on line 5-5 of Fig. 1, showing the details of the hinge construction and the spring for biasing the hinged housing section toward its open position.

Fig. 6 is a side elevation of one of the dielectric windows removed from the horn in which it is mounted.

Fig. 7 is a plan view of the window shown in Fig. 6.

Referring now to the drawings, there is disclosed an antenna comprising a housing, generally indicated by the reference numeral 10, having formed in its lower end portion a double-layer pillbox comprising a lower layer 13 and an upper layer 14 separated by a metal partition 35. The housing is supported by a vertical post 12 extending generally underneath the mid-portion of the housing 10.

An input waveguide 11 terminates in an energy radiating window 15 located in the lower layer of the pillbox structure. The waveguide is connected to a source of transverse electromagnetic waves and said waves are radiated from the window 15 to be focused by a parabolic reflector 16 adjacent the forward end of the pillbox structure, the parabolic reflector being so constructed that its focus is at the window 15. The waves having been focused by the parabolic reflector travel back along the upper layer 14 of the pillbox and travel around a developed bend 17, and enter a plurality of step-twisted sections generally indicated at 18. These step-twisted sections are best seen in the perspective view shown in Fig. l and they function to receive the vertically polarized wave emanating from the parabolic reflector and rotate the polarization of the wave to the horizontal position in three steps labeled respectively 19, 20 and 21. Each of these step-twisted sections for rotating the polarization of the emanating wave is connected to one of a battery of twenty-two sectoral horns, indicated by the reference numeral 22, and arranged in side by side relation with the center to center distance between horns being equal to or greater than one-half wavelength.

Certain of the horns 22 are spaced rearwardly of the remainder of the horns by a distance equal to an odd multiple of one-quarter wavelengths of the wave being emanated in order to provide a better impedance match and reduce the reflections in the radiating system. The spacing of these horns is not accomplished in a regular pattern. However, the pattern is symmetrical about the center of the antenna. Considering the horns as numbered consecutively from one end of the array to the other, horns 3, 4, 5, 9, 11, 13, 15, 16, 17, 21 and 22 are spaced one-quarter wavelength or an odd multiple of one-quarter wavelengths behind the remainder of the horns, since it has been found by experimentation that this particular arrangement ofthe horns is the best arrangement for suppressing deleterious side eflects of the wave emanating from one horn upon the wave issuing from the horns adjacent thereto since by this arrangement it is possible to break up the pattern of the scattered radiation emanating from the individual horns so that reinforcement of individual radiated components is avoided. In this manner, the overall side lobe energy is held below a desired minimum in any given direction.

In order to prevent water from entering the horns and into the antenna system, and also to provide a broadband impedance match to either water or air, each of the horns 22 has a dielectric window 23 sealed into its open or flared end. The dielectric windows are best illustrated in Figs. 6 and 7 and each comprises a main section 24 which is the same width as that of the horn at its flared end. A generally square inwardly projecting portion 25 formed with a taper 26 on its side edges conforms to the internal dimensions of the flared horn 22 and is sealingly engaged therewith. A vertically extending rectangular section 27 extends from the forward face of the block 24. A square block 28 projects inwardly from the section 25, and similarly, a square block 29 projects forward from the rectangular section 27. The upper surface 30 of each of these windows is tapered downwardly and outwardly away from the horn at an angle of approximately 25. A Window designed in this manner will provide a broadband impedance to match the antenna output to either air or water and thereby eliminate the possibility of damage to the transmitter should the antenna be inadvertently submerged while the transmitter is still energerized.

A non-reflecting lossy dielectric 31 is provided in the rear portion ofthe antenna housing to absorb any back radiation which may emanate from the waveguide feed.

The forward half of the upper surface of the housing is in the form of a flap 32 which is hinged to the remainder of the housing by means of a piano type hinge 33. A torsion spring 34 surrounds the pin of the piano type hinge and bears against the undersurface of the flap and the stationary portion of the housing in order to bias the flap toward its outwardly extended position illustrated in the dot-dash lines in Fig. 2. When in this outwardly extended position, the flap 32 forms one side of a large flared horn to help in the vertical shaping of the beam emanating from the antenna. When the antenna is submerged, the flap 32 is closed by the hydrodynamic pressure of the water therearound induced by the motion of the submarine to the position shown in full lines in Fig. 2 and forms a fairing completing the streamline construction of the outer surface of the antenna in order to reduce to a minimum the drag pro duced by the antenna in passing through the water.

Throughout the specification I have used the terms front and rear with respect to the electrical properties of the antenna. It will be appreciated that when traveling through the water the antenna is trailed with its rear portion as considered above toward the front of the vessel. The same designations of front and rear with respect to the antenna are used in the appended claims.

From the foregoing description, it may be seen that I have provided an antenna adapted for use on submarines, which antenna has a streamlined exterior configuration in order to reduce the drag of the antenna to a minimum, .wherein a parabolic reflector is used to focus the transverse electromagnetic wave energy, and wherein the vertically polarized wave is rotated to a horizontal polarization by the novel use of a plurality of steptwisted sections and then emanated from a sectoral horn array. It is further evident that I have provided an antenna which provides a broadband impedance match to either air or water, whereby, if the antenna should be inadvertently submerged while the antenna is still energized, there will be no damage to the transmitter.

While I have shown and described the preferred form ofmy invention, it is to be understood that various modifications may be made therein without departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a microwave system, a rectangular waveguide having a relatively long side and a relatively short side, means for introducing microwave energy into said waveguide, a plurality of polarization rotating elements each connected to said Waveguide adjacent each other in the plane of the relatively large dimension of said wave guide, each of said polarization rotating elements being adapted to receive a portion of the wave traveling through said waveguide and rotating the polarization of said portion through 90, a plurality of adjacent radiating means connected one to each of said polarization rotating elements for radiating the said portions, whereby said portions will re-merge into a single wave having its plane of polarization normal to the plane of polarization of the initial wave.

2. In a microwave system, a rectangular waveguide having a relatively long side and a relatively short side, means for introducing plane polarized microwave energy into said waveguide, a plurality of polarization rotating elements each connected to said waveguide adjacent each other in the plane of the relatively large dimension of said waveguide, each of said polarization rotating elements being adapted to receive a portion of the polarized microwave energy traveling through said waveguide and rotating the polarization of said portion through 90, a plurality of adjacent radiating means connected one to each of said polarization rotating elements for radiating the said portions, whereby said portions will re-merge into a single Wave having its plane of polarization normal to the plane of polarization of the initial wave.

3. In a microwave system, a parallel plate waveguide, means for introducing microwave energy into said parallel plate waveguide, a plurality of polarizati n r t ting elements each connected to said waveguide adjacent each other in a plane parallel to the plane of mid parallel plate waveguide, each of said polarization rotating elements being adapted to receive a portion of the microwave energy traveling through said parallel plate waveguide and rotating the polarization of said portion through a plurality of adjacent radiating means connected one to each of said polarization rotating elements for radiating the said portions, whereby said portions will re-merge into a single wave having its plane of polarization normal to the plane of polarization of the initial wave.

4. In a microwave system, a parallel plate waveguide, means for introducing plane polarized microwave energy into said parallel plate waveguide, a plurality of polarization rotating elements each connected to said parallel plate waveguide adjacent each other in a plane parallel to the plane of said parallel plate waveguide, each of said polarization rotating elements being adapted to receive a portion of the polarized microwave energy traveling through said parallel plate waveguide and rotating the polarization of said portion through 90", a plurality of adjacent radiating means connected one to each of said polarization rotating elements for radiating the said portions, whereby said portions will remerge into a single wave having its plane of polarization normal to the plane of polarization of the initial wave.

5. In a microwave system, a rectangular waveguide having a relatively long side and a relatively short side, means for introducing a plane polarized TEM wave into said waveguide, a plurality of polarization rotating elements each connected to said waveguide adjacent each other in the plane of the relatively large dimension vof said waveguide, each of said polarization rotating elements being adapted to receive a portion of the wave traveling through said waveguide and rotating the polarization of said portion through 90, a plurality of adjacent radiating means connected one to each of said polarization rotating elements for radiating the said wave portions, whereby said wave portions will re-merge into a single wave having its plane of polarization normal to the plane of polarization of the initial wave.

6. In a microwave system, a parallel plate waveguide, means for introducing a plane polarized T EM wave into said parallel plate waveguide, a plurality of polarization rotating elements each connected to said parallel plate waveguide adjacent each other in a plane parallel to the plane of said parallel plate waveguide, each of said polarization rotating elements being adapted to re ceive a portion of the wave traveling through said parallel plate waveguide and rotating the polarization of said portion through 90', a plurality of adjacent radiating means connected one to each of said polarization rotating elements for radiating the said wave portions, whereby said wave portions will re-merge into a single wave having its plane of polarization normal to the plane of polarization of the initial wave. 7

7. In a microwave antenna, a parallelplate waveguide construction, an input waveguide connected to said parallel plate waveguide for feeding microwaves into said parallel plate waveguide, an array of adjacent sectoral horns, and a plurality of step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns.

8. In a microwave antenna, a parallel plate waveguide construction, an input waveguide connected to said parallel plate waveguide for feeding microwaves into said parallel plate waveguide, an array of adjacent sectoral horns, and a plurality of step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, said sectoral horns being spaced a center to center distance equal to at least one-half wavelength.

9. In a microwave antenna, a housing, a double-layer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM 'waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, and a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns.

10. In a submarine radar antenna, a housing, a doublelayer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, and a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water.

11. In a submarine radar antenna, a housing, a doublelayer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, certain of said horns being spaced an odd multiple of one-quarter wavelengths behind the remainder of said horns, and a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water. 7

12. In a submarine radar antenna, a housing, a doublelayer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, said sectoral horn array comprising an even number of horns wherein approximately one-half of the horns are spaced an odd multiple of one-quarter wavelengths behind the remainder of the horns and wherein the horns are arranged symmetrically on either side of the axis of propagation of the system, a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water.

13. In a submarine radar antenna, a housing, a doublelayer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, said sectoral horn array comprising an even number of horns and wherein approximately one-half of the horns are spaced an odd multiple of one-quarter wavelengths behind the remainder of the horns and wherein the horns are arranged symmetrically on either side of the axis of propagation of the system, a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water, and a nonreflecting lossy dielectric adjacent the rear wall of said housing to absorb the back radiation of the Waveguide feed.

14. In a submarine radar antenna, a streamlined housing, the front half of the top of said housing being hinged to the remainder of said housing and adapted to open to form one side of a flared horn, a double-layer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns.

15. In a submarine radar antenna, a streamlined housing, the front half of the top of said housing being hinged to the remainder of said housing and adapted to open to form one side of a flared horn, a double-layer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water.

16. In a submarine radar antenna, a streamilend housing, the front half of the top of said housing being hinged to the remainder of said housing and adapted to open to form one side of a flared horn, a double-layer parallel plate waveguide construction in the lower portion of said housing, an input waveguid fixed to the rear of said housing for feeding TEM waves into said parallel platewaveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, certain of said horns being spaced one-quarter wavelength behind the remainder of said horns, a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water.

17. In a submarine radar antenna, a streamlined housing, the front half of the top of said housing being hinged to the remainder of said housing and adapted to open to form one side of a flared horn, a double-layer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, said sectoral horn array comprising twenty-two horns and wherein horns numbers 3, 4, 5, 9, 11, 13, 15, 16, 17, 21 and 22 respectively are spaced one-quarter wavelength behind the remainder of the horns, a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or water.

18. In a submarine radar antenna, a streamlined housing, the front half of the top of said housing being hinged to the remainder of said housing and adapted to open to form one side of a flared horn, a double-layer parallel plate waveguide construction in the lower portion of said housing, an input waveguide fixed to the rear of said housing for feeding TEM waves into said parallel plate Waveguide, an array of horizontally adjacent sectoral horns in the upper portion of said housing, a plurality of horizontally adjacent step-twisted sections connecting the output end of said parallel plate waveguide with said array of sectoral horns, said sectoral horn array comprising twenty-two horns and wherein horns numbered 3, 4, 5, 9, 11, 13, 15, 16, 17, 21 and 22 respectively are spaced one-quarter wavelength behind the remainder of the horns, a dielectric window mounted in the flared end of each of said horns and sealed thereto, said windows being suitably shaped to provide a broadband impedance match to either air or Water, and a non-reflecting lossy 5 dielectric adjacent the rear wall of said housing to absorb the back radiation of the wave guide feed.

References Cited in the file of this patent UNITED STATES PATENTS King May 26, 19 42 Purcell et a1 Aug. 19, 1952 Chu et a1 May 12, 1953 Cohn Feb. 2, 1954

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