US 2479209 A
Description (OCR text may contain errors)
L. J. CHU
ANTENNA Filed July 9, 1945 5555555500' Lf/ 70a @Jaaa 7 1 JJU M- wwf/MM cv/ INVENTOR LAN JEN. CHU
ATTORN EY Patented ug. 16,V 1949 Y Y z ,r'zazoa` Y Y y Lan J en Chu, Brookline, Mass., assigner, by mesne ssignm'ents,"t`o` tlieUnited States of America as1represcnted.by.the Secretary of l f Aereaengage.er
eclaimsv.. (C1150- salem This invention relates "to antenna andmore participara to' ritenne adapte@ for lise win; highA frequency'communication systeins.' i"
'Figfl illustrates-orie embodiment of theinvention; and; l. A
Fig'.- l2l illustrates-a preferred. embodiment-ofthe invention.-
Fig.- 3`-illustrates a sectional Aview takenv alongV line-S-ofiig. l; anda Fig. 4-illustrates yal sectional-,view taken: along 1ine.4-4ioff.fFig.1.u" M u Rectangular wave guide 5 has a pluralitylloffr apertures y'82preferably in one narrow wall 6 thereof, these apertures being` spaced apart a distance a which isYsubst'aritially equal to a wavelengthinrthe jguide,r and .is .terminatedbytanf adjustable'plunger 1. Parallel plat'elwaveguidef Comprisinewo, .coniugare .,paalllel-plaii filetes ID and I,"extends generally normal to the wall E of lwave guide 5 in whichithe aperture 8lare provided.y Y f waveguide. 9. restricts remedied@ fregi @l2-11.- tures 8 to the spa`ce betwe n itsuplates I0 and IIJ', that is, generally speaking; to a plane normal to Wave guide 9 is terminated by a movable plunger.; I I along the side opposed to apertures 8. As will be apparent from the explanation to follow, the other two sides I'2 and I3 of wave guide 9 may be closed or not, as desired.
One plate I of wave guide 9 has a plurality of apertures I4 therein spaced apart a distance b corresponding to the wavelength in wave guide 9, which may be the same as the free space wavelength at the frequency contemplated.V
If energy is directed into wave guide in the direction of plunger 1, part of the energy will leak or escape through apertures 8. Plunger 1 may be faced with energy-absorbent material, or have a reflecting surface, and is adjusted to reduce the standing wave ratio to a minimum in wave guide 5. As shown in Fig. 3, plunger I m'oves Within Wave guide 5 in the direction of the arrow. T0 make a desired adjustment, set screw 3D is moved, in the direction of the arrow, Within slotted portion 3I of wave guide 5. It is preferred that distance a approach the free space wave length, and in any event since energy escaping from apertures 8 is in phase, the major portion of the energy will be directed normally to the wall 6 containing apertures 8.- Thus', it'willbe seen that-itis not necessary'to haveslde walls" I2 arid vI3 to'fvvaveV- gli eS although th'es may 'be'inclded toiinini? iriiaethe fescapel'f( energy conta 1 a longitudinal central line alongA bfad waIlI Therefore?prtrs'* |15 mairie pcdfrom apertures lrrby a distance a substantially a half wave length in the wave guide I5 at the frequency involved, and by staggering apertures I1 and I8 on opposite sides of the longitudinal median line of broad wall I5, radiation from al1 the apertures will be in phase. A parallel plate Wave guide I9 having plates 2D and 2D may be extended generally normal to broad wall I5 in a manner similar to that in which parallel plate wave guide 9 extends normally to narrow wall 6 of wave guide 5 in'Fig. 1. In one plate 20 of wave guide I9 of Fig. 2 are an array of apertures 2! and 22 aligned with apertures I1 and I8 respectively, and also spaced apart a distance a in the direction parallel to broad wall I6. In the direction normal to broad wall I6 they may be spaced apart a distance b substantially equal to one Wave length in free space. Thus a narrow directed pencil beam will extend normally to plate 20 containing apertures 2I and 22.
A further improvement may be obtained Vby reducing the distance b' (or b) to a value less than the free space wavelength, even though slightly less, which will result in materially reducing side lobes. The radiation then will not be normal to plate 20, but Will still be a pencil, or directed beam, with side lobes reduced. Although not shown in Fig. 2, adjustable plungers may be used in a manner similar to that in which they are employed in the device shown in Fig. 1 in order to reduce standing Waves Within wave guides I5 and I9.
As is Well known in the art, antennas having directive effects in radiation conversely have like directive effects in reception and similar structures may be used for radiation or reception of electromagnetic energy.
Many variations will be apparent to those skilled in the art, and therefore it is not desired to restrict the scope of the invention to the precise embodiment herein disclosed.
What is claimed is:
1.' In combination, a rectangular Wave guide having apertures along one Wall thereof spaced at equal intervals of substantially one Wavelength in the guide at the operating frequency, and a parallel plate Wave guide whose plates eX- tend substantially normal from said one Wall, one of said plates having openings therein in alignment in a direction normal to said one Wall with the apertures in said one Wall and spaced apart substantially one free-space Wavelength at the operating frequency in the direction normal to said one Wall, whereby a pencil beam of electromagnetic energy may be radiated into space from said parallel plate Wave guide in a direction normal to the said one plate.
2. The combination of claim 1, including an adjustable plunger termination in said rectangular Wave guide and an adjustable plunger termination in said parallel plate Wave guide.
3. In combination a rectangular wave guide having apertures equally spaced along one wall thereof, and a parallel plate wave guide having plates which extend substantially normal from said one Wall, one of said plates having openings in alignment in a direction normal to said Wall with said apertures, said openings being also aligned in a direction parallel to said Wall, and spaced apart equally in a direction normal to said Wall, whereby a pencil beam of electromagnetic energy may be radiated into space from said openings.
4. The combination of claim 3 including an adjustable plunger termination in said rectangular Wave guide and an adjustable plunger termination in said parallel plate Wave guide.
5. A directive antenna comprising a rst rectangular wave guide having apertures along one Wall thereof spaced at equal intervals of substantially one half Wave length in the guide at the operating frequency, said apertures being staggered on opposite sides of the longitudinal median line of said Wall, and a parallel plate Wave guide Whose plates extend substantially normal from said one Wall, one of said plates having openings therein in alignment in a direction normal to said one Wall with the apertures in said one Wall and spaced apart in the direction parallel to said one Wall at intervals equal to those of the apertures in said one Wall, said plate openings being spaced apart in the direction normal to said one Wall at equal intervals of substantially one wave length in free space at the operating frequency.
6: VA directive antenna comprising a rst rectangular wave guide, one of the walls thereof having a plurality of equally spaced apertures formed therein, said apertures being staggered on opposite sides of the longitudinal median line of said Wall, and a second Wave guide including two parallel plates normal to said apertured Wall and enclosing said-apertures, one of said enclosing plates having apertures therein in alignment in a direction normal to said one Wall with the apertures in said one wall and spaced apart in the direction parallel to said one Wall at intervals equal to those of the apertures in said one wall, said plate apertures being spaced apart at predetermined intervals in the direction normal to said one Wall.
LAN JEN CHU.
REFERENCES CITED The following references are of record in the iile of this patent:
UNITED STATES PATENTS Number Name Date 2,226,479 Pupp Dec. 24, 1940 2,297,202 Dallenbach Sept. 29, 1942 OTHER REFERENCES Ser. No. 353,755, Dallenbach (A. P. C.) pub. May 25, 1943.