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Publication numberUS2588226 A
Publication typeGrant
Publication dateMar 4, 1952
Filing dateDec 5, 1947
Priority dateJul 30, 1942
Also published asDE818384C, US2434646, US2503549, US2530691, US2607850, US2740094
Publication numberUS 2588226 A, US 2588226A, US-A-2588226, US2588226 A, US2588226A
InventorsGardner Fox Arthur
Original AssigneeBell Telephone Labor Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Wave filter
US 2588226 A
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Description  (OCR text may contain errors)

March 4, 1952 FOX 2,588,226

WAVE FILTER Original Filed July 30, 1942 I IN VEN T 0/? By A. 6. FOX W 77647 Patented Mar. 4, 1952 WAVE FILTER Arthur Gardner Fox, Eatontown, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application July 30, 1942, Serial No.

452,851. Divided and this application December 5, 1947, Serial No. 789,811

Claims.

This invention relates to wave transmission networks and more particularly to frequency selective networks for use in the transmission of guided electromagnetic waves.

The principal object of the invention is to transmit freely a band or bands of electromagnetic waves while effectively blocking waves falling outside of the band or bands. A further object is to improve the transmission characteristics of filters for use in wave guides.

A uniform metallic sheath with or without a dielectric filler will serve as a guide for suitable electromagnetic waves. In cross-section the sheath may be circular, rectangular, or of other shape. For all frequencies above a minimum, known as the cut-off frequency, the guide acts like a transmission line and has a specific propagation constant and characteristic impedance. For any particular frequency there are an infinite number of cross-sectional sizes and shapes of guide which will have the same characteristic impedance. Shunt reactive elements are obtained by placing partial obstructions across the wave guide. For example, a shunt reactive element for dominant transverse electric waves may be obtained by using a transverse metal partition having a slit therein which extends substantially from one side to the other. If the slit is perpendicular to the direction of polarization of the electric field the element is primarily capacitive, and if parallel with the field the element is primarily inductive. If the slot is 'replaced by a. centrally located square or circular opening, the reactance will still be dominantly inductive.

In accordance with. one embodiment of the present invention, a wave guide filter with improved transmission characteristics is formed by providing two or more branch chambers spaced along the wave guide. The chambers open into the guide through apertures the centers of which are spaced from each other approximately one quarter of a wavelength, or an odd integral multiple thereof, at the mid-band frequency. The chambers are tuned to resonate at or near the mid-band frequency and the resonance is made as sharp as desired by a proper choice of the width of the coupling aperture. If the wave guide is rectangular in cross-section, the chambers may branch from any of the four sides.

The three-branch filter disclosed may, for example, be designed to have a band-suppression characteristic with high attenuation at the midband frequency and, on each side thereof, a frequency of substantially perfect transmission, giving very sharp cut-offs. The chambers may be tuned to difierent resonant frequencies to in- 2 crease the width of the band. For example, two chambers, tuned to slightly different frequencies, may be used to provide two peaks of attenuation with sustained attenuation between. A still wider band may be provided by using more complex side branches.

This is a division of my copending application Serial No. 452,851, filed July 30, 1942, now Patent 2,432,093, issued December 9, 1947.

The nature of the invention will be more fully understood from the following detailed description and by reference to the accompanying drawing', in which like reference characters are used to designate similar parts and in which:

Fig. 1 is a perspective view, partly cut away, of a wave filter in accordance with the invention comprising three chambers branching from one of the narrower sides of a rectangular wave guide; and

Fig. 2 is a similar view of a modified form of the filter in which the chambers branch from one of the Wider sides of the wave guide.

In the embodiment shown in Fig. 1, the filter comprises a rectangular wave guide 96 and three tuned side-branch chambers 91, 98 and 99. The chambers are closed at their outer ends by the end plates I00, MI and I02, respectively, and open into one of the narrower sides I06 of the guide 96 through the apertures I03, I04 and I05. The centers of the apertures I03, I04 and I05 are spaced from each other approximately one quarter of a wavelength, or an odd integral multiple thereof,

at the mid-band frequency of the filter. The electric field E of the dominant transverse electric waves carried by the guide 96 is polarized in a direction parallel to the narrower side I06, as indicated by the arrow. Each of the branch chambers 91, 98 and 99 is tuned to resonate at the mid-band frequency by properly choosing its length, and the resonance is made as sharp as desired by a proper choice of the width of the associated aperture I03, I04 or I05. The threebranch filter shown may, for example, be designed to provide a band-suppression characteristic having high attenuation at the mid-band fre quency and, on each side thereof, a frequency 01. substantially perfect transmission, giving very sharp cut-offs.

The chambers may be tuned to different resonant frequencies to increase the width of the suppression band. For example, two chambers, tuned to slightly different frequencies, may be used to provide two peaks of attenuation with sustained attenuation between. If a still wider band is desired, any one or all on the branches 97, 98 and 99 may be replaced by more complex side branches such, for example, as are disclosed in Fig. 21 of the above-identified parent application. As shown therein such a side branch comprises a resonant end chamber opening through an aperture into a side-branch section which connects the chamber with the main wave guide. At an intermediate point a reactive impedance branch, which may be either inductive or capacitive, is shunted across the side-branch section. As described therein, the side branch may be adjusted to provide either a band-pass or a bandsuppression characteristic for the filter.

It will be understood, of course, that either more or less than three side-branch chambers may be used. Furthermore, the chambers may branch from any of the four sides of the wave guide 96. As shown, for example, in Fig. 2 all three of the side-branch chambers I91, I98 and I09 branch from one of the wider sides I ll] of the rectangular wave guide l l I. Otherwise the sidebranch chambers 506, I91 and I98 are similar to the chambers 91, 98 and 99, and the main wave guide II! is similar to the guide 96, shown in Fi 1.

What is claimed is:

l. A filter for suppressing a band of guided electromagnetic waves comprising a tubular, single-conductor wave guide of rectangular cross-section and a plurality of cavity resonators, each of said resonators having an opening into said guide, the centers of said openings having a longitudinal spacing approximately equal to an odd integral multiple or a quarter wavelength at the mid-band frequency of said band and two of said resonators being resonant respectively at different frequencies within said band.

2. A filter in accordance with claim 1 in which said guide has unequal cross-sectional dimensions and one of said resonators opens into said 4 guide through one of the narrower sides thereof.

3. A filter in accordance with claim 1 in which said guide has unequal cross-sectional dimensions and one of said resonators opens into said guide through one of the wider sides thereof.

4. An insertion piece for insertion in a signal transmission channel for effectively preventing transmission through said channel in a predetermined frequency band, said piece comprising a transmission line section having coupled thereto a plurality of cavity resonators, each tuned to a different frequency within said band, and separated one from another along the length of said line section by intervals corresponding to odd numbers of quarter wave-lengths at frequencies within said band.

5. An insertion piece for insertion in a signal transmission channel for effectively preventing transmission through said channel in a predetermined frequency band, said piece comprising a wave-guiding element having coupled thereto a plurality of cavity resonators, each tuned to a different frequency within said band, and separated one from another along the length of said wave guiding element by intervals correspond ing to odd multiples of quarter wave lengths at frequencies within said band.

ARTHUR GARDNER FOX.

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

UNITED STATES PATENTS Number Name Date 2,106,768 Southworth Feb. 1, 1938 2,129,712 Southworth Sept. 13, 1938 2,270,416 Cork Jan. 20, 1942 2,438,913 Hansen Apr. 6, 1948

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2106768 *Sep 25, 1934Feb 1, 1938American Telephone & TelegraphFilter system for high frequency electric waves
US2129712 *Dec 9, 1933Sep 13, 1938American Telephone & TelegraphTransmission of energy effects by guided electric waves in a dielectric medium
US2270416 *Dec 22, 1937Jan 20, 1942Emi LtdElectrical wave system
US2438913 *Sep 2, 1942Apr 6, 1948Sperry CorpHigh-frequency filter structure
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2654867 *Oct 5, 1949Oct 6, 1953Emi LtdElectrical wave band pass circuits
US2762986 *Aug 24, 1951Sep 11, 1956Raytheon Mfg CoLow pass filters
US2785381 *Apr 23, 1953Mar 12, 1957Brown Burton PElectromagnetic wave filter
US2790959 *May 13, 1952Apr 30, 1957Gen Electric Co LtdElectric filter circuits
US2814777 *Nov 23, 1953Nov 26, 1957Peters Jr Philip HNoise generating system
US2816270 *Jun 26, 1951Dec 10, 1957Bell Telephone Labor IncMicrowave channel dropping filter pairs
US2951221 *Aug 1, 1955Aug 30, 1960Hughes Aircraft CoPhase shifter
US2956247 *Jan 26, 1956Oct 11, 1960Sperry Rand CorpBroad band microwave phase shifter
US3058072 *Nov 15, 1956Oct 9, 1962Raytheon CoMicrowave filters
US3093733 *Jul 8, 1960Jun 11, 1963John P BlewettResonator particle separator
US3202945 *Apr 19, 1963Aug 24, 1965Nippon Electric CoCavity resonator tuned by means of magnetically controlled coaxial ferrite material located in an auxiliary cavity
US3210693 *Dec 20, 1962Oct 5, 1965Automatic Elect LabWaveguide branching filter having compensating cavities
US3428918 *May 26, 1966Feb 18, 1969Us ArmyMultiplexer channel units
US3600711 *Aug 13, 1969Aug 17, 1971Varian AssociatesCoaxial filter having harmonic reflective and absorptive means
US3611214 *Aug 18, 1969Oct 5, 1971Varian AssociatesWaveguide reflective harmonic filter
US4124830 *Sep 27, 1977Nov 7, 1978Bell Telephone Laboratories, IncorporatedWaveguide filter employing dielectric resonators
US4833428 *Nov 30, 1987May 23, 1989Mok Chuck K14/12 GHz Duplexer
DE1154886B *Jan 20, 1956Sep 26, 1963Thomson Houston Comp FrancaiseWeichenanordnung fuer sehr kurze elektromagnetische Wellen
DE3729402A1 *Sep 3, 1987Mar 16, 1989Licentia GmbhWaveguide filter arrangement
Classifications
U.S. Classification333/208
International ClassificationH01P5/02, H01P1/213, H01P1/207, H01P1/209, H01P5/08, H01P1/20, H01Q13/00
Cooperative ClassificationH01P5/08, H01P1/207, H01P1/2138, H01P5/024, H01Q13/00, H01P1/209
European ClassificationH01P1/209, H01P5/02B1, H01P5/08, H01P1/213F, H01Q13/00, H01P1/207