US3621483A - Waveguide filter - Google Patents

Waveguide filter Download PDF

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Publication number
US3621483A
US3621483A US643279A US3621483DA US3621483A US 3621483 A US3621483 A US 3621483A US 643279 A US643279 A US 643279A US 3621483D A US3621483D A US 3621483DA US 3621483 A US3621483 A US 3621483A
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Prior art keywords
waveguide
section
frequency
filter
passband
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Expired - Lifetime
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US643279A
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English (en)
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George Frederick Craven
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STC PLC
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/219—Evanescent mode filters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C19/00—Chemical modification of rubber
    • C08C19/28—Reaction with compounds containing carbon-to-carbon unsaturated bonds

Definitions

  • Bolton and Isidore Togut ABSTRACT Waveguide band-pass filters operated such that only evanescent H waves exist at the operating frequency of the system are terminated in a capacitive reactance which at the center frequency of the desired pass band is the conjugate of the positive imaginary characteristic impedance of the length of evanescent waveguide.
  • the capacitive termination is the only obstacle required in the guide PATENTEDuuv 16 Ian 3 6 21 .48 3
  • SHEET 2 [IF 3 lnvenlor GEORGE F, CRAVf/V Agenl WAVEGUIDE FILTER BACKGROUND OF THE INVENTION This invention relates to waveguide filters.
  • Waveguide band-pass filters have heretofore been con structed in waveguide in which a propagating mode -usually the dominant --exists.
  • each of said length of waveguide being dimensioned such that a propagating mode exists at the operating frequency of the system, and at least one H-mode filter coupling said lengths of propagating waveguide together, each of said H- mode filters including at least one section of waveguide dimensioned to have a cutofi frequency above said frequency passband, said section having a positive inductive characteristic reactance at the center frequency of said passband, and a plurality of capacitive screws located at predetermined points along the length of said waveguide, the capacitive reactance of each said screw being the conjugate of the positive imaginary characteristic reactance of said section of waveguide at the operating frequency of the system.
  • FIG. 1 shows two lengths of propagating waveguide interconnected by a three section band-pass filter embodying the invention
  • FIG. 2 is the equivalent circuit of one section of the bandpass filter of FIG. 1,
  • FIG. 3 is the circuit of FIG. 2 bisected
  • FIG. 4 is the characteristic of a conventional lumped circuit band-pass filter
  • FIG. 5 is the characteristic of the band-pass filter according to the present invention.
  • FIG. 6 shows an alternative form of the band-pass filter of FIG. 1,
  • FIG. 7 shows another form of band-pass filter embodyingthe invention
  • FIG. 8 is the approximate equivalent circuit of the bandpass filter of FIG. 7, M
  • FIGS. 9 and 10 show the filter section of FIG. 7 coupled as a series and a shunt stub respectively to dominant mode waveguide
  • FIG. 11 is the equivalent circuit of a single section bandpass filter of FIG. 12.
  • dominant mode H waves are propagated in a length l of propagating waveguide from any suitable microwave source (not shown), such as a generator or a receiving aerial.
  • a length 2 of propagating waveguide is interconnected with the length l by a three section band-pass filter 3 constructed entirely in evanescent waveguide, that is to say, all modes in this filter are evanescent at the operating frequency of the system.
  • the center frequency, f,, occurs at the geometric mean
  • the network of FIG. 2 is a band-pass filter, the image impedance of which is given by (3).
  • An obvious characteristic of the filter is that its bandwidth is a function of 1 and (in the ideal lossless case) as 'yl so then tanh 1-? coth 1 and the bandwidth (f,f,) reduces towards zero.
  • this is probably the simplest waveguide filter realizable for it consists simply of a set of capacitance screws 4, (one per section) in an appropriate size of guide.
  • the rejection below resonance is intrinsically higher than other filters (because 'yl increases with wavelength) and the loss per sections is not excessive.
  • the typical insertion loss for a three section filter is on the order of 0.1 db per section.
  • unwanted passbands can occur but the usual dominant mode multiple cavity resonance effect is obviously absent.
  • FIG. 6 is used where the capacitive screws are replaced by capacitive ridges 5.
  • This style of construction is, of course, identical to that of the familiar corrugated low-pass filter. It is then possible to completely suppress this passband, or alternatively, employ it as a second controllable passband in systems requiring this feature.
  • Networks of the type described above have useful properties as reactance networks when considered as purely single port devices. This is illustrated by the network of FIG. 3 with its output terminals open circuited. The input impedance is then given by (3a) which slightly rearranged is (COS h 14-Z0B1 sin 2 2 Z "Z T" (ZgBl cosh sin y w This network has the zero and infinity values of 2, as described above and is roughly the equivalent of the m-derived section shown in FIG. 7. The approximate equivalent circuit is given in FIG. 8. p
  • the length of evanescent waveguide 10 is terminated by a short circuited section of propagating waveguide 11 having a length I such that tan 21rI/Ag is negative, and thus forms the required terminating capacitive reactance for the length of evanescent waveguide.
  • This form of termination prevents energy being lost at the termination if this form of construction is used for example as a stub.
  • the reactance section of FIG. 7 When coupled to conventional dominant mode guide 12, it can be used as a shunt or series stub in the usual way (13 or 14 in FIGS. (9 and 10 respectively). By using it as a shunt stub the passband appears at a lower frequency than the rejection band; as a series stub the positions of the two bands are reversed. It can, for instance, be used as the series element in a tenninating m-derived section for the evanescent waveguide filter. Alternatively, in this type of filter it can be used as part of an internal section giving high rejection at a specified frequency.
  • FIG. 11 A more accurate version of the equivalent circuit of a single section filter similar to that of FIG. 1 is shown in FIG. 11, the filter 15 being shown somewhat schematically in FIG. 12 as a length of evanescent waveguide 16, with a central capacitive screw 17, between dominant mode guides 16 and I9.
  • inductance shunt susceptances represented by the junction with dominant mode guide
  • the 'unction susceptances if sufficlently large can completely e iminate the resonances.
  • Experiments with X-band guide at 4,000 MI-Iz. failed to demonstrate this effect until the junction susceptances were tuned out with capacitive screws in shunt.
  • the capacitive screws By constructing the filter to have capacitive screws at each end of the evanescent waveguide section to have the fonn of a 1r section, the capacitive screws then serve both to tune out the junction susceptances and as the terminating capacitive reactance of the filter section.
  • a waveguide system comprises:
  • each said length of waveguide being dimensioned such that a propagating mode exists at the operating frequency of the system
  • each of said I-I-mode filters ineluding:
  • At least one section of waveguide dimensioned to have a cut-off frequency above the frequency passband of said filter, said section having a positive inductive characteristic reactance at the center frequency of said passband;
  • a capacitive screw located at a predetermined point along the length of said section, the capacitive reactance of said screw being the conjugate of the positive imaginary characteristic reactance of said section of waveguide at the operating frequency of the system for providing a frequency passband having 7 h ll cot h ll 7 equals the wavelength of the propagated energy, 1 equals the length of said section, 2,, equals the characteristic impedance of said section and C equals the capacitance of said screw, the center frequency of said passband defined by the equation j", flf2' i i i i I

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
US643279A 1966-06-10 1967-06-02 Waveguide filter Expired - Lifetime US3621483A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB25966/66A GB1129185A (en) 1966-06-10 1966-06-10 Improvements in or relating to waveguide filters

Publications (1)

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US3621483A true US3621483A (en) 1971-11-16

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US643279A Expired - Lifetime US3621483A (en) 1966-06-10 1967-06-02 Waveguide filter

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US (1) US3621483A (de)
CH (1) CH474871A (de)
DE (1) DE1541937C3 (de)
ES (1) ES341650A1 (de)
GB (1) GB1129185A (de)
SE (1) SE344388B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851281A (en) * 1973-06-11 1974-11-26 Raytheon Co Impedance matched waveguide device
US4761625A (en) * 1986-06-20 1988-08-02 Rca Corporation Tunable waveguide bandpass filter
US6169466B1 (en) 1999-05-10 2001-01-02 Com Dev Limited Corrugated waveguide filter having coupled resonator cavities
US6232853B1 (en) 1999-03-12 2001-05-15 Com Dev Limited Waveguide filter having asymmetrically corrugated resonators
US20030062972A1 (en) * 2001-09-10 2003-04-03 Tdk Corporation Bandpass filter

Citations (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2197123A (en) * 1937-06-18 1940-04-16 Bell Telephone Labor Inc Guided wave transmission
US2231602A (en) * 1937-03-20 1941-02-11 American Telephone & Telegraph Multiplex high frequency signaling
US2376785A (en) * 1943-02-05 1945-05-22 Westinghouse Electric & Mfg Co Adjustable attenuator
US2427098A (en) * 1943-10-23 1947-09-09 Rca Corp Variable attenuator for centimeter waves
US2432093A (en) * 1942-07-30 1947-12-09 Bell Telephone Labor Inc Wave transmission network
US2531447A (en) * 1947-12-05 1950-11-28 Bell Telephone Labor Inc Hybrid channel-branching microwave filter
US2557110A (en) * 1945-02-17 1951-06-19 Sperry Corp Wave guide attenuator apparatus
US2588103A (en) * 1946-09-14 1952-03-04 Bell Telephone Labor Inc Wave guide coupling between coaxial lines
US2623120A (en) * 1950-04-20 1952-12-23 Bell Telephone Labor Inc Microwave filter
US2659870A (en) * 1947-07-10 1953-11-17 Polytechnic Inst Brooklyn Mode filtered cutoff attenuator
US2706276A (en) * 1946-05-03 1955-04-12 Maurice B Hall Cut-off waveguide attenuator
US2724805A (en) * 1950-12-02 1955-11-22 Louis D Smullin Microwave apparatus
US2816270A (en) * 1951-06-26 1957-12-10 Bell Telephone Labor Inc Microwave channel dropping filter pairs
US2866949A (en) * 1953-10-29 1958-12-30 Bell Telephone Labor Inc Microwave circulators, isolators, and branching filters
US3215955A (en) * 1964-06-01 1965-11-02 Motorola Inc Waveguide switching by variable tuning of a cavity which shunts a band-pass filter
US3451014A (en) * 1964-12-23 1969-06-17 Microwave Dev Lab Inc Waveguide filter having branch means to absorb or attenuate frequencies above pass-band
US3496498A (en) * 1965-08-11 1970-02-17 Nippon Electric Co High-frequency filter

Patent Citations (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2231602A (en) * 1937-03-20 1941-02-11 American Telephone & Telegraph Multiplex high frequency signaling
US2197123A (en) * 1937-06-18 1940-04-16 Bell Telephone Labor Inc Guided wave transmission
US2432093A (en) * 1942-07-30 1947-12-09 Bell Telephone Labor Inc Wave transmission network
US2376785A (en) * 1943-02-05 1945-05-22 Westinghouse Electric & Mfg Co Adjustable attenuator
US2427098A (en) * 1943-10-23 1947-09-09 Rca Corp Variable attenuator for centimeter waves
US2557110A (en) * 1945-02-17 1951-06-19 Sperry Corp Wave guide attenuator apparatus
US2706276A (en) * 1946-05-03 1955-04-12 Maurice B Hall Cut-off waveguide attenuator
US2588103A (en) * 1946-09-14 1952-03-04 Bell Telephone Labor Inc Wave guide coupling between coaxial lines
US2659870A (en) * 1947-07-10 1953-11-17 Polytechnic Inst Brooklyn Mode filtered cutoff attenuator
US2531447A (en) * 1947-12-05 1950-11-28 Bell Telephone Labor Inc Hybrid channel-branching microwave filter
US2623120A (en) * 1950-04-20 1952-12-23 Bell Telephone Labor Inc Microwave filter
US2724805A (en) * 1950-12-02 1955-11-22 Louis D Smullin Microwave apparatus
US2816270A (en) * 1951-06-26 1957-12-10 Bell Telephone Labor Inc Microwave channel dropping filter pairs
US2866949A (en) * 1953-10-29 1958-12-30 Bell Telephone Labor Inc Microwave circulators, isolators, and branching filters
US3215955A (en) * 1964-06-01 1965-11-02 Motorola Inc Waveguide switching by variable tuning of a cavity which shunts a band-pass filter
US3451014A (en) * 1964-12-23 1969-06-17 Microwave Dev Lab Inc Waveguide filter having branch means to absorb or attenuate frequencies above pass-band
US3496498A (en) * 1965-08-11 1970-02-17 Nippon Electric Co High-frequency filter

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851281A (en) * 1973-06-11 1974-11-26 Raytheon Co Impedance matched waveguide device
DE2426173A1 (de) * 1973-06-11 1975-01-02 Raytheon Co Anordnung zum koppeln von hochfrequenzenergie mittels eines hohlleiters
US4761625A (en) * 1986-06-20 1988-08-02 Rca Corporation Tunable waveguide bandpass filter
US6232853B1 (en) 1999-03-12 2001-05-15 Com Dev Limited Waveguide filter having asymmetrically corrugated resonators
US6169466B1 (en) 1999-05-10 2001-01-02 Com Dev Limited Corrugated waveguide filter having coupled resonator cavities
US20030062972A1 (en) * 2001-09-10 2003-04-03 Tdk Corporation Bandpass filter
US6828880B2 (en) * 2001-09-10 2004-12-07 Tdk Corporation Bandpass filter

Also Published As

Publication number Publication date
GB1129185A (en) 1968-10-02
DE1541937C3 (de) 1975-05-22
DE1541937B2 (de) 1974-10-03
ES341650A1 (es) 1968-07-01
DE1541937A1 (de) 1970-05-06
CH474871A (de) 1969-06-30
SE344388B (de) 1972-04-10

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Owner name: STC PLC,ENGLAND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.;REEL/FRAME:004761/0721

Effective date: 19870423

Owner name: STC PLC, 10 MALTRAVERS STREET, LONDON, WC2R 3HA, E

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.;REEL/FRAME:004761/0721

Effective date: 19870423