US2479227A

US2479227A - Dual frequency antenna

Info

Publication number: US2479227A
Application number: US627042A
Authority: US
Inventors: Edgar N Gilbert
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-11-06
Filing date: 1945-11-06
Publication date: 1949-08-16
Anticipated expiration: 1966-08-16

Description

Patented Aug. 16, 1949 Tino :niesne This riiwentiim .rellates-togaitennas f for cornninnioationystenis. andgrnorleparticularly to an antenna .ip r. use as lag Juie'aeo-nfin. connection with rad-iofobect-.locating Ls'ysten- 1`s sirable @to l:utilize ,a frendxor .."foe -interrogation (IEE) kWit/tia :tanget seachtindication. I tlisialso desired toobtain 5511.10'si'antially uniform omnidirectional radiation;o ff-.eisierg'y- I-Ieretoiore, itfh'as beeneconsidered :rieqelssarynthair beacon antenna for-fobtaining nnifornieoninidirectional radiation be^radial1ly symrnetricaii in crosslesedtionand' that separate-,antennas the :used as ea beacon and .'f or EFF-interrogation. n

itfhasfnowebeenifminid thatfsiibstantially Luni; formtomnidirectiona diationimayabepbtained with'-an ant enna fa s'yrnmetrica1 `in crosss'eotion such esfof streamlined tearedropior evene-'recetang/ula'r cross-secton- `Such anqantenna .has

beencdiselosed -in thefcopending application of Henry -J.Rib1e1;, seria1=Nn, f62ri,o4o,.LmedgNovember :6, V19415, 'entitled .?Antenna. ,'Ihisrinvention contempates van #improgeitnenteof the ,invention of"themforesaiducopendin pplcationfandfom'- bines therewith means for:sinniltaneoslymadiatingfenergy.ofitwo difierentreguencies `T'Ihusfmzler of .thefcbectsiof'thejpres'entinventionl'is fto utilize ahsingle =antenna :adapted Vto transmit and receive energy at @two .different ranges offrequencies .fsininltaneoslesuch asa f' microwave :frequeney range @having wavelengths of the order of centimetelgsforvguse as aheacon inconnection,withragiiogobject-locating systems, arid asionger wave :frequency grangeliaving Wavelengths s of the AVordereef,metersorlonger for the i .It iswanotherobjeet offftheinyention .to provide .a beacon antenna having a streamlined, ,teandrop ,or other non-,circular f shape Lin V.Ygross-:section capable .o radiating energypt twodierent ranges ,of frequencies fin substantially -uniiorm Aomnidirectional radiationpatterns.:

Forsa better understar-nii n g,oi. tI-1 e Airwentionltogether with 'other -and further bjects thereof,

'reference is :had to, thefollowingdescriptmn f'- rlgfflfisaa longitudinal sideiiseetional viewof the antenna'according Ttof-the present invention;

E'Figxfs; isf'a transversegseotional vieweofttheean- 'tenna of Figs. 1 fand l2itakenAsiibstari-ti ally .,along zthe;1ine-:3.0f=Fi g.r2; f f

incliidingfpipe l`| 1entend' the4 approximate ent 3 coming the other section of a dipole radiator. Energy is fed to the long wave dipole radiating element 2'I comprising sections I3 and I 4 by means of a coaxial conductor transmission line 28 connected to a source of lower frequency energy not shown. The center conductor 29 of coaxial line 28 extends beyond the end of the outer conductor 30 and is connected to the upper dipole section I3, for example, through a transverse partition member 3| connected -to the wall o f dipole section I3. The outer conductor 30 is connected to the lower pipe or dipole section I4 by means of a transverse partition member 32. It will thus be understood that the pipe or dipole sections I3y and I4 comprising the long Wave radiating element 21 is excited by means of the coaxial line 28 and is adapted to radiate energy of longer wave lengths than, or of lower frequencies than, that of the microwave energy. Also such longer wave energy is radiated in a substantially uniform omnidirectional pattern. -With the antenna in its contemplated vertical position, radiations of both frequencies will therefore have approximately uniform azimuth patterns.

In order to prevent any lower frequency excitation from interfering with the high frequency transmission through antenna IIJ, and particularly to keep the low frequency or long wave signais from being carried along the outside surface of line 2| inside of the aircraft, the long wave dipole 21 is shortedby a stub 33. Stub 33 comprises the inner surfaces of partition 32, and of lower pipe section |4' which is shorted at the junction of antenna IIJ with the base I2 by means of a plate 34, the inner conductor of the stub 33 being the outer surface of coaxial line 2| extending longitudinally therethrough. Inasmuch as the outer conductor I4' of this stub is large compared with the outer surface of the coaxial line 2l, the characteristic impedance of the stub 33 will be large Yand the admittance will be reasonably small even though the length X of the stub 33 is only, for example, of the order of V3 wavelength of the longer wave energy. The overall'length of-antenna I 0 and the length of the bottom pipe or dipole section I4 are so chosen as to obtain proper-impedance matching for the long wave dipole radiating element 21 comprising the sections I3 and I4. It has beeen found that even though the currents ofboth the higher and lower frequency ranges of energy both exist on the upper section V|3, the polarization is such that no interference exists between energy of one frequency with that of the other and that radiation of both frequency ranges can simultaneously be emitted from antenna I l) without interference.

With the arrangement as. described hereinbefore, theantenna has several advantages over known types of beacon antennas. In `the first place becausethe microwave radiating element comprises slots rather than Vdipoles and because of the streamlined nature of the entire assembly, a tight fitting housing may be used which may be small and streamlined for low wind drag effect. Also, since the microwave frequency antenna is mounted at the upper end of the longer wave radiating element rather than in the bottom section, the nulls in the elevation pattern Ydue to reflections from the skin surface of the aircraft are less likely to occur and are less serious than would otherwise occur. Also, the antenna as thus described provides a more compact, light-weight easily constructedand easily mountable structure than heretofore known. Y e

While there has beendescribed what is at pres- 4 ent considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

What is claimed is: l 1. An antenna for radiating electromagnetic energy of two different ranges of frequencies,

l comprising a hollow pipe of electrically conductive material and of streamlined shape in crosssection, said pipe comprising two aligned pipe sections forming upper and lower pipe sections when said pipe is in' its contemplated vertical position, a ring of dielectric material separating said upper and lower sections, whereby said sections comprise the two poles of a dipole radiating element, a coaxial transmission line disposed within said pipe and longitudinally thereof adapted to transmit energy of one range of frequencies, means for coupling said coaxial line to each of said pipe sections whereby said sections are adapted to be excited by and to radiate said energy, the walls of said upper pipe sections on opposite sides of the major axis of the crosssection thereof each having a slot disposed longitudinally of said upper section and along the approximate centerline of each of said walls whereby said slots are directly opposite each other, said upper pipe section including said slots comprising a second radiating element adapted to radiate energy of a different range of frequencies than said dipole radiatingV element, and means for feeding energy of said diiferentrange' of frequencies `to and for exciting said second radiating element, said means including a second coaxial line extending longitudinally through said hollow pipe, and means for coupling said Vsecond c0- axial line to the edge portions of said slots, said dipole radiating element and second radiating element being adapted to be excited by and to radiate energy of both said ranges of frequencies simultaneously without interference of one with the other in substantially uniform omnidirectional radiation patterns in planes perpendicular to said pipe sections.

2. An antenna as claimed in claim 1 wherein said second radiating element is adapted to be excited and to radiate energy within the microwave range of frequencies and said dipole radiating element is vadapted to be excited by and to radiate energy within a range of lower frequencies than said microwave energy.

3. An antenna as claimed in claim 1 wherein means are provided for shorting said lower pipe section at the base thereof whereby said lower pipe section forms a stubY to prevent energy currents being carried on the outer surface of said second coaxial line.

4. An antenna as claimed in claim 1 wherein the outer conductor of' said first-mentioned c0- axial line extends upwardly substantially to the upper end of said' lower section and the inner conductor'thereof extends beyond said outer conductor, said means for coupling said first coaxial line to said pipe sections comprising a member connecting said outer conductor'to said lower section and a member connecting said inner conductor to said upper section, and wherein said means for coupling said second coaxial line to said slots comprises a balanced dipole termination of said secondrcoaxial line, one element of said dipole termination connecting the inner conductor of Ysaid second coaxial line to the midpoint of the edge portion of onev'of said. slots, the other element of said dipole termination connecting the outer conductor of said second coaxial line to the midpoint of the edge portion of the opposite slot, said coaxial lines being disposed substantially parallel to each other within said pipe.

5. An antenna for radiating electromagnetic energy of two different ranges of frequencies simultaneously in substantially uniform oninidirectional radiation patterns in planes perpendicular to the axis of said antenna comprising a substantially hollow pip-e of electrically conductive material and of non-circular cross-section, said pipe comprising two aligned pipe sections affording upper and lower pipe sections when said pipe is in its contemplated vertical position, a member of dielectric material separating said sections whereby said sections form the two poles of a dipole radiating element, means for transmitting energy of one range of frequencies to and energizing said two poles, said upper section having at least one slot in each of two opposed sides thereof said slots being disposed longitudi nally of said upper section and means for feeding energy of a different range of frequencies to said slots whereby said upper section is adapted to radiate said last-mentioned energy.

6, An antenna for radiating electromagnetic energy of two diffe-rent ranges of frequencies simultaneously in substantially uniform omnidirectional radiation patterns in planes perpendicular to the axis of the antenna comprising a substantially hollow pipe of electrically conductive material and of non-circular cross-section, said pipe comprising two aligned pipe sections affording upper and lower pipe sections when said pipe is in its contemplated vertical position, said sections forming two poles of a dipole radiating element, means for transmitting energy of one range of frequencies to and energizing said two poles, said upper section having at least one slot in each of two opposed sides thereof said slots being disposed longitudinally of said upper section and means for feeding energy of a different range of frequencies to said slots whereby said upper section is adapted to radiate said last mentioned energy EDGAR N. GILBERT.

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

UNITED STATES PATENTS Number Name Date 2,251,997 Goldmann Aug. 12, 1941 2,287,220 Alford June 23, 1942 2,349,942 Dallenbach May 30, 1944 2,362,561 Katzin Nov. 14, 1944 2,398,096 Katzin Apr. 9, 1946 2,404,196 Seeley July 16, 1946 Y2,414,266 Lindenblad Jan. 14, 1947 FOREIGN PATENTS Number Country Date y 523,074 Great Britain July 4, 1940