US3579153A - Microwave filter - Google Patents

Microwave filter Download PDF

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Publication number
US3579153A
US3579153A US666013A US3579153DA US3579153A US 3579153 A US3579153 A US 3579153A US 666013 A US666013 A US 666013A US 3579153D A US3579153D A US 3579153DA US 3579153 A US3579153 A US 3579153A
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United States
Prior art keywords
guide
filter
irises
cavities
characteristic
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Expired - Lifetime
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US666013A
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English (en)
Inventor
Han-Chiu Wang
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AT&T Corp
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Bell Telephone Laboratories Inc
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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
    • H01P1/207—Hollow waveguide filters
    • H01P1/209—Hollow waveguide filters comprising one or more branching arms or cavities wholly outside the main waveguide

Definitions

  • the structure in accordance with the invention reduces to a single slab of conductive material one and one-half wavelengths long and of a specified thickness, extending in the connecting rectangular guide adjacent to a wide wall and centered therein across from the irises of the resonant cavities.
  • the principles of the invention may be extended to filters having an arbitrary number of cavities both symmetrical and unsymmetrical.
  • FIG. 1 is a cross-sectional view of an illustrative three-cavity filter in accordance with the invention
  • FIG. 2 is a schematic of a typical lumped element prototype filter having a characteristic desired for FIG. 1;
  • FIGS. 3 through 5 represent sequential transmission line substitutions to derive an equivalence between FIG. 1 and FIG. 2.
  • FIG. I a three-cavity filter has been selected to illustrate the principles of the invention.
  • the filter comprises a section of rectangular conductively bounded waveguide 10 and three, approximately one-half wavelength long cavities Ill, 12 and 13 coupled through a wide wall of guide 10 by means of irises I4. 15 and 16 at points spaced three-quarters of a guide wavelength.
  • Capacitive tuning screws 17. 18 and 19 are located in the wide wall opposite each of the irises I4, 15 and 16 respectively. To this extent the structure is conventional and well known in the art.
  • the characteristic impedance of guide 10 in the region extending from iris 14 to iris 15 is reduced to a value designated Z by restricting the narrow cross-sectional dimension of guide 10 by conductive slab 20, and in the region between irises 15 and iris 16 (or screws I18 and 19) to a value designated 2. by conductive slab 21.
  • screws 17, 18 and 19 extend through holes in slabs 20 and 21 and the end of each slab is considered to coincide with the diameter of a screw.
  • FIG. 2 a typical low-pass prototype circuit is shown comprising a series inductance 31, a pair of shunt capacitors 32 and 33, a source impedance 34 and a load impedance 35.
  • the values g,,, g,, g g and g referred to in the foregoing literature as g" values, are the normalized element values giving the frequency response desired.
  • FIG. 3 The transmission line equivalent of FIG. 2 is shown in FIG. 3 in which a shorted stub 36 of characteristic impedance Z and of length I has been substituted for the inductive element 31, and the open line stubs 37 and 38 of characteristic admittance Y, and Y and the same length l have been substituted for the capacitive elements 32 and 33, respectively, using the frequency transformation:
  • the Q of a resonant cavity is readily varied by varying the size of its coupling iris. Therefore it is an obvious advantage to express the parameters of cavities 1 l, 12 and I3 of FIG. 1 by their loaded Qs. It is known that a one-half wavelength cavity of given loaded Q is equivalent to a short circuited three-quarter wavelength transmission line stub of characteristic impedance Z when This expression is known to be sufficiently accurate for frequencies close to resonance as in most waveguide filters.
  • the desired filter is symmetrical, as in the case in a maximally flat filter of the type most often desired, Q and Q and Z, and Z are identical. Therefore, the slabs 20 and 21 are reduced to a single slab of conductive material of the required thickness one and one-half wavelengths long. If only a twocavity filter is desired, the values of Q Q and Z define the required parameters when The principles of the invention may be extended to filters of four or more cavities. Following the same approach detailed with respect to FIGS. 2 through 5 for a five-cavity filter, for example, the following table of relationships may be obtained:
  • An electromagnetic wave filter having a predetermined transmission characteristic comprising a conductively bounded rectangular waveguide and a plurality of resonant cavities coupled to said guide each by one of a plurality of spaced irises, said guide cross section as defined by said conductive boundary being reduced in at least one dimension in the region of said irises to a dimension which remains uniform from the center of one iris to the center of an adjacent iris in order to include the wave transmission characteristics of said guide between said irises as a contribution to said predetermined transmission characteristic.
  • the filter according to claim 1 having the same band edge frequency m as a given lumped constant prototype filter of the type defined by a plurality of shunt capacitors interconnected by at least one series inductance and in which each component thereof is specified by a normalized g value giving the filter response desired, said filter including three cavities having loaded values of Q Q and Q separated by sections of waveguides of characteristic impedances Z and Z where R is a load impedance one of a plurality of spaced irises, the characteristic imductive boundary is restricted to reduce the characteristic impedance of said guide between said irises.
  • Electromagnetic wave filter having a predetermined transmission characteristic comprising a conductively bounded waveguide having a given characteristic impedance, a plurality of resonant cavities coupled to said guide each by pedance of said guide being sharply reduced in a step at the transverse cross section of the center of one iris and remaining constant along a length of said guide to the transverse cross section of the center of an adjacent iris, the value of said reduced impedance being proportioned relative to the Qs of said cavities to make the transmission characteristics of said guide along said length of said predetermined transmission characteristic.

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US666013A 1967-09-07 1967-09-07 Microwave filter Expired - Lifetime US3579153A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US66601367A 1967-09-07 1967-09-07

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US3579153A true US3579153A (en) 1971-05-18

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US666013A Expired - Lifetime US3579153A (en) 1967-09-07 1967-09-07 Microwave filter

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US (1) US3579153A (de)
BE (1) BE720055A (de)
DE (1) DE1791017B1 (de)
FR (1) FR1582682A (de)
GB (1) GB1236983A (de)
NL (1) NL6812761A (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673522A (en) * 1971-04-05 1972-06-27 Northern Electric Co Microwave balanced external cavity rejection filter
US4124830A (en) * 1977-09-27 1978-11-07 Bell Telephone Laboratories, Incorporated Waveguide filter employing dielectric resonators
US4321568A (en) * 1980-09-19 1982-03-23 Bell Telephone Laboratories, Incorporated Waveguide filter employing common phase plane coupling
EP0226951A1 (de) * 1985-12-13 1987-07-01 Siemens Aktiengesellschaft Bandsperre für kurze elektromagnetische Wellen mit Leitungselementen
EP0275650A1 (de) * 1986-12-04 1988-07-27 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of Communications Speisungsvorrichtung einer Satellitenantenne
US4833428A (en) * 1986-12-04 1989-05-23 Mok Chuck K 14/12 GHz Duplexer
EP0668623A1 (de) * 1994-02-22 1995-08-23 Hughes Aircraft Company Mikrowellen-Hohlleitermultiplexer
US20150280299A1 (en) * 2014-03-27 2015-10-01 Electronics And Telecommunications Research Institute Waveguide band pass filter using short-circuit stub for rejection performance improvement

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3119925C2 (de) * 1981-07-10 1983-07-21 András Dipl.-Ing. 1116 Budapest Bely Verfahren und Gerät zur Erdschlußortung an Starkstrom-Freileitungsnetzen

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434646A (en) * 1942-07-30 1948-01-20 Bell Telephone Labor Inc Wave guide branching arrangement
US2649576A (en) * 1949-10-07 1953-08-18 Bell Telephone Labor Inc Pseudohybrid microwave device
US2961619A (en) * 1957-06-21 1960-11-22 Sperry Rand Corp Microwave filter
US3058072A (en) * 1956-11-15 1962-10-09 Raytheon Co Microwave 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
GB1018923A (en) * 1963-01-14 1966-02-02 Standard Telephones Cables Ltd Waveguide filters
US3237134A (en) * 1963-03-26 1966-02-22 Gen Electric Microwave filter
US3353123A (en) * 1965-09-01 1967-11-14 Gen Electric Microwave filter comprising absorbing structures for removing suprious wave energy
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

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434646A (en) * 1942-07-30 1948-01-20 Bell Telephone Labor Inc Wave guide branching arrangement
US2649576A (en) * 1949-10-07 1953-08-18 Bell Telephone Labor Inc Pseudohybrid microwave device
US3058072A (en) * 1956-11-15 1962-10-09 Raytheon Co Microwave filters
US2961619A (en) * 1957-06-21 1960-11-22 Sperry Rand Corp Microwave filter
GB1018923A (en) * 1963-01-14 1966-02-02 Standard Telephones Cables Ltd Waveguide filters
US3237134A (en) * 1963-03-26 1966-02-22 Gen Electric Microwave filter
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
US3353123A (en) * 1965-09-01 1967-11-14 Gen Electric Microwave filter comprising absorbing structures for removing suprious wave energy

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3673522A (en) * 1971-04-05 1972-06-27 Northern Electric Co Microwave balanced external cavity rejection filter
US4124830A (en) * 1977-09-27 1978-11-07 Bell Telephone Laboratories, Incorporated Waveguide filter employing dielectric resonators
FR2404316A1 (fr) * 1977-09-27 1979-04-20 Western Electric Co Filtre en guide d'ondes a resonateurs dielectriques
US4321568A (en) * 1980-09-19 1982-03-23 Bell Telephone Laboratories, Incorporated Waveguide filter employing common phase plane coupling
EP0226951A1 (de) * 1985-12-13 1987-07-01 Siemens Aktiengesellschaft Bandsperre für kurze elektromagnetische Wellen mit Leitungselementen
EP0275650A1 (de) * 1986-12-04 1988-07-27 Her Majesty The Queen In Right Of Canada As Represented By The Minister Of Communications Speisungsvorrichtung einer Satellitenantenne
US4833428A (en) * 1986-12-04 1989-05-23 Mok Chuck K 14/12 GHz Duplexer
US4868575A (en) * 1986-12-04 1989-09-19 Mok Chuck K Phase slope equalizer for satellite antennas
EP0668623A1 (de) * 1994-02-22 1995-08-23 Hughes Aircraft Company Mikrowellen-Hohlleitermultiplexer
US20150280299A1 (en) * 2014-03-27 2015-10-01 Electronics And Telecommunications Research Institute Waveguide band pass filter using short-circuit stub for rejection performance improvement

Also Published As

Publication number Publication date
BE720055A (de) 1969-02-03
DE1791017B1 (de) 1972-05-31
NL6812761A (de) 1969-03-11
FR1582682A (de) 1969-10-03
GB1236983A (en) 1971-06-23

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