US2438913A - High-frequency filter structure - Google Patents

Description

Patented Apr. 6, 1948 meri-FREQUENCY FILTER s'rittiiiioiiii" -iirdem-Qm N YQ; agisrn; erry'Corpoi-ation, a corporation of concentric transmissi'line`device and more specifically," to low passfltes adapted ist),Inlay?n maximumV attenuation" for 'iltra' high frfrequency,-

der ofone meter'or less. This 'applicatiopwisaf division" of 'copendirig aprilication Serial l\lo,.`` 417,229; entitled Higii'fr'eqiieriejy tute" strugture, ledoctober '31; 1941, in the nar' of William Wi Hansen.

i prirent.;.from` .he speeiicatonilistenin electromagnetic energyf Wavelengthofthe or; 5"'

tiQrtiiiththacq @Hammamet/ing wherein the invention isWeiggiN died in concrete form.

Intheldraiwins., Y, Eis.; i is .a longitudinali-parti n u L im .c. :alpe L". f fii'i." In' the aboveLineriton'f application1h ther u oughan f an equivalent cirdisclosed r4an"'improved "and practicable er'ri d cuit `o `he filter i i ment of `high freqiiiieyiiute structure 'i'itiiiziii 2,1

"inv tion em voltagemay 'be applied between" the` `sect'ior1s" oi f2() said resonator.' A transiii'issio'ri linhev'ice iiri-AV i corporating principles of "the preset'fiifivention may be used tolintrodce" `th"11irectionaljw voltage, 'and simultaneously to prefifit -leala'glel of ultra highfrequency"energy'fr`the ''ese- 2n nator. Suche, transmission Vline device alsomaybe A used as a lter Vto introdcuvoltages sueltas` heater voltages, cathode voltages,V modulation voltages, etc., through a Wallof a shieldingboxw :fm surrounding a high Afrequency' tuloe, `or other high frequency `apparatu`sf` thereby preventing any high frequency radiation fromrleaking outA of the box to disturb otherhigh frequency circuits in the vicinityo'f the shielded tube, or for 3 other' related p'iirpo'sc-zs. a A e Therefore, a principalobject Aof the "presentine;V Y vention` is to provide a low'` pass yfiltersuitable for filtering out ultra high frequencies and'passu ing only vunidirectional Vvoltageslsucl1g-asgarefuse'fY ful forrbeam voltages,V heater voltagesy'QQntrol voltages, or buncherresonatoracceleration?? voltages, or for passingvery lowfrequency'modJ ulation voltages such as are .'u'sedin` ultraVA higlilfis frequency'tube structurees'of the 'generaltypel disclosed in the aforementioedfapplicatih .Another4 object of the preserit'invntois t'o' provide a transmission? line suitable Torj'ise such ultra high frequncydevices," Where y u i directional `f voltages` or suchilowrede'nqy volt ages may be appliedthrughthetransmissie line to active'portirisffo the `iiltal,"higl'i e o quencyf devices in such a mariner'thatultra hig ng..r,elat1.

frequency energy does not leak out oftli'eiltra relftuivelysmall ndictosprmgs.

It will be observed from Fig. 1 Ythat the ratio of the respective conductor diameters Vdiiiers according to the spacing between them. Accordingly the characteristic impedance o f the respective sections increases and decreases alternatelyalong the conductor, being a function of the ratio of the inner diameter of the outerconductor to the outer diameter of the inner conductor, thus permitting the device to operate as a transmission line for matching impedances.

It is also evident that the cross-'section of the iilter of Fig. 1 may be revolved about any axis eccentric thereto, as shown in the application cf which this is a division, to generate a filter made up of annular components. Although relative dimensions of such generated devices may be necessarily slightly modified, they are equally useful as ultra high frequency lters. Fig. 3 illustrates one such section of revolution, generated from Fig. 1, and made up of annular concentric portions. One portion of the section consists of inner supporting cylindrical conducting member 58, and external conducting tubular member 64 secured to member 58, said member 58 being eiiectively an extension of tubular member 64. Another portion consists of annular tubular conducting members 65 and 66 joined by reduced diameter portions 69, all of which are concentric to support 58. Tubular member65 affords low impedance capacitive coupling to support member 58 by virtue of the close inter-conductor spacing, while tube 66 likewise is capacitively linked to external tube 64, thus again providing a closed path for ultra high frequency vide discontinuities in the characteristic impedance, the successive sections of close spacing having progressively lower impedance and the successive sections of wide spacing having progressively higher impedance, thereby tending to increase the reliection of high frequency waves toward the source.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, itV is intended that all matter contained in the above Vdescription orshown in the accompanying drawings shall be interpreted as illustrative andi not in a limiting sense. What is claimed is:

1. A high frequency lter comprising coexten sive-inner and outer conductors, means providing; a, plurality of axially separated sections of relatively small interconductor spacing within said'. filter, and means providing a plurality of axiallyi separated sections of relatively large intercon. ductor spacing within said filter alternating with; said first sections and `being equal in length to said iirst sections, the relative interconductor.` spacing in said sections being such that said iilter: suppresses high frequency energy and passes lows frequency and unidirectional wave energy.

2. A high frequency filter comprising coextenisive inner. and outer conductors, means providing a plurality of axially separated sections of." relatively small inter-conductor spacing within.; said lter, and means providing a plurality of;

axially spaced sections of relatively large interconductor spacing within said lter alternating. with said first sections, wherein said sections aref each equal in axial length to approximately once quarter of the wavelength to be suppressed, and the relative inter-conductor spacings in said sections being such that said filter suppresses high frequency energy and passes low frequency and current, while allowingva unidirectional and/or a low frequency modulating voltage to be transmitted along the separate members.

Annular filter sections 69, 'III function similarly to the filter -described in Fig. 1. Filter element 10 has a hollow annular internal cavity 9|, which may be supplied with cooling water through tubes or conduits 'H and 12, which extend through end wall 'i3 and are supported by two glass bell jar members 14 and 'I4' placed on the diameter of wall 13. Heat also maybe removed by allowing a cooling fluid to ow through axial bore 6I in support 58.

It will be observed from Fig. 3 that the device comprises an internal member 58 cooperating with the surrounding walls of outer members 69 and of reduced diameter portions 65 to provide an elongated chamber between the members having inwardly projecting walls at spaced intervals, to provide the same rhythmic effect as the alternate outwardly extending sections 35 of Fig. 1. In any case the chambers 6D between the respecunidirectional wave energy,

3. The iilter defined in claim l, including solid dielectric means interposed between said conductors at said sections of small interconductor spacing.

4.A The filter dened in claim 1, including means providing passage of a Icooling iiuid interiorly of at least one of said conductors.

5. A transmission line filter device comprising arrouter conductor; a substantially concentrically disposed inner conductor, said inner conductor having a plurality of axially separated enlarged sections extending radially outward from said tive members are characterized by the opposite ter-wavelength. The cascaded sections suppress.

high frequency current, since the successively adjoining sections of close and Vwide spacing pro-l innerv conductor, said sections being equal in length to the separations therebetween and having an outer peripheral surface in closely spaced relation to the inner peripheral surface of said outer conductor; and a dielectric member interposed between said respective inner and outer peripheral surfaces.

6. A transmission line filter device comprisingan outer tubular conductor; an inner conductorextending substantially coaxially within said tubular conductor, said conductors having a plu. rality of axially separated sections providing rel..

atively close inter-conductor spacing; and having one another.

'7. A lter device comprising a tubular outer conductor; a substantially concentrically disposed inner conductor, said inner conductor having a plurality of axially separated enlarged sections extending radially outward from said inner conductor, each of said sections having an outer peripheral surface in closely spaced relation to the inner peripheral surface of said tubular outer conductor; and a tubular dielectric member located concentri'cally Within said device between said respective conductors, said enlarged sections being electrically of quarter-wavelength along the axis of said device, and said enlarged sections being :spaced along said conductor by similar quarter-wavelengths between adjoining sections.

8. A transmission line device comprising a tubular outer conductor, a concentric extension of said outer conductor, and a substantially concentrically disposed annular inner conductor having a plurality of axially separated reduced diameter sections extending radially inward toward said extension, each or said sections having an inner peripheral surface in spaced relation to the outer peripheral surface of said extension.

9. A transmission line device comprising a tu bular outer conductor, and a substantially concentrically disposed inner conductor, said inner conductor having a plurality of axially separated enlarged sections extending radially outward from said inner conductor said sections being equal in length to the separations therebetween, each of said sections having an outer peripheral surface in closely spaced relation to the inner peripheral surface of said tubular outer conductor, at least one of said conductors being hollow, and said device being provided with conduit means for circulating a iiuid within said hollow conductor.

10. A iilter device for suppressing high frequency radio oscillations, comprising a first hollow tubular conductor, an axial extension on said rst conductor, and a substantially annular second conductor disposed concentrically within said first conductor surrounding said extension of isaid rst conductor, said respective conductors having at intervals spaced along their axis a pluralityl of similar sections of close inter-conductor spacing, with said sections being separated axially by portions of greater inter-conductor spacing, and said portions being equal in length along said axis to the length of said sections.

11. A filter device as claimed in claim wherein said sections are dened by spaced inward and outward radial projections on said second conductor.

12. An ultra high frequency filter comprising a hollow tubular outer conductor, a concentric inner conductor, a plurality of spaced radially 6 enlarged conductive members, equal in length to the separation' therebetween, on said inner conductor, and a sleeve of dielectric material inter posed between the outer peripheries of said conductive members and the inner periphery of said outer conductor.

13. An ultra high frequency iilter comprising a hollow tubular outer conductor, a concentric inner conductor, hollow radially enlarged portions on said inner conductor spaced along said conductor `by separations equal in length to said portions, each of said portions having the outer periphery thereof adjacent to and coextensive with part of the inner periphery of said outer conductor, and means providing for passage of cooling fluid through said hollow inner conductor portions.

14. The filter deiined in claim 13, wherein said outer conductor is provided wvith an axial extension, and said hollow inner conductor portions are substantially annular and surround said extension.

15. The lter defined in claim 13, wherein said outer conductor is provided with an axial extension, and said hollow inner conductor portions have the inner and outer peripheries thereof respectively adjacent to and coextensive with parts of the outer periphery of said extension and the inner periphery of said outer conductor.

16. A transmission line filter device comprising a tubularA outer conductor having a coaxial reentrant extension and an inner conductor concentrically disposed therebetween, said inner conductor having ya plurality of axially separated sections spaced along said inner conductor and extending radially therefrom, the separations between said sections being equal in length to the length of said sections, each of said radially extending sections having a peripheral portion thereof in close proximity to the inner periphery of said outer conductor and the outer periphery of said reentrant extension.

WILLIAM W. HANSEN.

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

, A UNITED STATES PATENTS Certificate of Correction Patent No. 2,438,913. April 6, 1948.

WILLIAM W. HANSEN It is hereby oertied that errors appear in the printed specification of the above numbered potent requiring correction as follows: Column 2, line 55, for the Word springs read spactngs; column 4, line 70, for lenth read length; and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the oase in the Patent Office.

Signed and sealed this 1st day of June, A. D. 1948.

THOMAS F. MURPHY,

Assistant 00m/mission of Patents.

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