US3639862A - Waveguide filter utilizing evanescent waveguide, with tunable ferrite loading - Google Patents

Waveguide filter utilizing evanescent waveguide, with tunable ferrite loading Download PDF

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Publication number
US3639862A
US3639862A US681637A US3639862DA US3639862A US 3639862 A US3639862 A US 3639862A US 681637 A US681637 A US 681637A US 3639862D A US3639862D A US 3639862DA US 3639862 A US3639862 A US 3639862A
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United States
Prior art keywords
waveguide
section
filter
band
ferrite
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Expired - Lifetime
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US681637A
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English (en)
Inventor
George Frederick Craven
Richard Finnie Skedd
Bishop S Stortford
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STC PLC
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International Standard Electric Corp
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Priority claimed from GB25966/66A external-priority patent/GB1129185A/en
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Assigned to STC PLC reassignment STC PLC ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE 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

Definitions

  • WAVEGUIDE FKLTER UTIILHZHNG EVANIESCENT WAVEGUIDE, WITH TUNABLE FERRITE LOADING Inventors: George Frederick Craven, Sawbridgeworth; Richard Finnie Slredd, Bishop's Stortiord, both of England [73] Assignee: International Standard Electric Corporation, New York, N.Y.
  • ABSTRACT A waveguide filter wherein transversely magnetized ferriteloading strips are mounted within a waveguide section to produce cutoff at a higher frequency than in an empty waveguide, thereby providing evanescent-mode operation at the operating frequencies.
  • the waveguide section is then torminated in a capacitive reactance which at the center frequency of the desired passband is the conjugate of the positive imaginary characteristic impedance of the length of evanescent waveguide.
  • Means for varying the magnetic field applied to the ferrite-loading strips is provided for tuning the filter over a predetermined range of passband frequencies.
  • Waveguide band-pass filters have heretofore been constructed in waveguide in which a propagating mode-usually the dominant-exists SUMMARY OF THE INVENTION
  • an H-wave band-pass filter or filter section comprising a length of waveguide loaded with ferrite material such that when subjected to a transverse unidirectional magnetic field the effective dimensions of the length of waveguide are such that only evanescent I-I-waves can exist therein at the operating frequency.
  • FIG. I shows two lengths of propagating waveguide interconnected by a three-section band-pass filter embodying the invention
  • FIG. 2 shows effective permeability vs. angular frequency for transversely magnetized ferrite
  • FIG. 3 shows a section of waveguide loaded with ferrite sidewall strips
  • FIG. 4 shows insertion loss vs. frequency for a ferrite-loaded section of waveguide in cutoff condition with DC magnetic field as a parameter
  • FIG. 5 is the equivalent circuit of one section of the bandpass filter of FIG. 1,
  • FIG. 6 is the circuit of FIG. 5 bisected
  • FIG. 7 is the image impedance characteristic of the bandpass filter of the present invention.
  • FIG. 8 shows an alternative form of the band-pass filter of FIG. I
  • FIG. 9 shows another form of band-pass filter embodying the invention.
  • FIG. 10 is the approximate equivalent circuit of the bandpass filter of FIG. 9,
  • FIG. 11 shows the filter section of FIG. 9 coupled as aseries stub to dominant-mode waveguide
  • FIG. 12 shows the filter section of FIG. 9 coupled as a shunt stub to a dominant-mode waveguide
  • FIG. 13 shows a single-section band-pass filter coupled between dominant-mode waveguides
  • FIG. 14 is the equivalent circuit of the single'seetion bandpass filter of FIG. 13.
  • 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 in the same waveguide as the lengths 1 and 2, but containing loading strips 4 of ferrite material symmetrically arranged one at each sidewall of the waveguide.
  • FIG. I there is shown an electromagnetic apparatus for producing the DC magnetic field which includes a core having a winding 21 woundthereon. Coupled to winding-2l is a source of energy 22, the output of which is variable. This enable the magnitude of the magnetic field H to be varied.
  • the production of the DC magnetic field by means of a permanent magnet 23 is shown in FIG. 9.
  • the cutoff frequency may be controlled by the DC magnetic field.
  • the cutoff frequency can be made higher or lower than the empty '5 waveguide value.
  • the effective permeability 11. of the ferrite can be varied from positive to negative values by the DC magnetic field as shown in FIG. 2, in which ne is the cutoff frequency and w, gyromagnetI'c resonance for the infinite ferrite medium.
  • Equation 4 may be written w pt e and it follows that by having than I / ⁇ 'm I then B is made negative i.e., evanescent condition. This is brought about by adjustment of the DC magnetic field on the ferrite (by varying the output of source 22 of FIG. I, for example) so that for the frequency of operation p is made sufficiently negative (see FIG. 2).
  • the net effect is as if the width L of the waveguide has been reduced.
  • the width L of the waveguide in FIG. 1 is in the evanescent condition brought about as explained above by the DC magnetic field I-I
  • This condition is illustrated in FIG. 4 and FIG. 4 also shows how the cutoff frequency of the section is dependent on the value of DC magnetic field.
  • the field, and how the insertion loss increases at a specific frequency for increases in the strength of the DC magnetic field may be made variable in value when applied as shown in FIG I by varying the output of the energy source 22.
  • permanent magnet means is used to provide the electromagnetic field I-I the field may be varied by changing the position of the magnetic poles with respect to the waveguide structure.
  • the filter is tunable in frequency by variation in the value of the DC magnetic field. An increase in field raises the frequency, and a reduction in field lowers the frequency.
  • Waveguide which is evanescent has a positive imaginary characteristic impedance i.e., at its input tenninals (if infinitely long) it will appear as a pure inductance.
  • the A matrices for such a network are;
  • the center frequency,f, occurs at the geometric mean
  • fll IS given by An obvious characteristic of the filter is that its bandwidth is a function of y and (in the ideal lossless case) as yl m then tanh yl v cot/t yl and the bandwidth (I'm/' reduces towards zero.
  • the length of evanescent waveguide 10 may be terminated by a short-circuited section of propagating waveguide 11 having a length lsuch that tan (21rI/Ag) is negative, and thus forms the required terminating capacitive reactance for the length of evanescent waveguide.
  • This form of terminating prevents energy being lost at the termination if this form of construction is used for example as a stub.
  • a permanent magnet 23 supplies the magnetic field H It is pointed out that magnets having other shapes and movable poles may be used.
  • FIG. 14 A more accurate version of the equivalent circuit of a single-section filter similar to that of FIG. 1 is shown in FIG. 14, the filter 15 being shown schematically in FIG. 13 as a length of evanescent waveguide 16 with a central capacitive screw 17, between dominant-mode guides 18 and 19.
  • inductance shunt susceptances representedby the junction with dominant-mode guide, has the effect of bringing the two resonances much closer together than predicted by The junction susceptances, if sufficiently large can completely eliminate the resonances.
  • Experiments with X-band guide at 4,000 mc./sec. 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 olthe evanescent waveguide section to have the form ol'a 11' section, the capacitive screws then serve both to tune out the junction susceptances and as the terminating capacitive reactance of the filter section.
  • the evanescent waveguide section or sections may be constructed in waveguide of different dimensions from that of the propagating waveguide. If the waveguide dimensions are larger than that required for the cutoff condition at the operating frequency, the ferrite material loading strips have applied thereto a transverse DC magnetic field such that the effective permeability of the material is made sufficiently negative to bring the section to the evanescent condition.
  • the waveguide dimensions may be smaller than required for the operating frequency, and the ferrite material loading strips have applied thereto a transverse DC magnetic field such that the effective permeability of the material is made sufficiently positive to bring the effective dimensions of the section to the evanescent condition at the desired frequen-
  • the magnetic field H for the filters of FIGS. 8, 11, 12 and 14 are applied in the same manner as for the filter of FIGS. 1 and 9. That is, by an electromagnet such as shown in FIG. 1 or by a permanent magnet 23 such as shown in FIG. 9.
  • An I-I-band-pass filter or filter section comprising:
  • means for terminating said section of waveguide including a capacitive screw having a capacitive reactance which at the center frequency of the desired passband is the conjugate of the positive imaginary characteristic reactance of said first section of waveguide.
  • a band-pass filter or filter section as claimed in claim 1 including a capacitive reactance terminating means disposed at each end of the said section of waveguide.
  • means for terminating said section of waveguide including capacitive ridge disposed in said first section of waveguide having a capacitive reactance which at the center frequency of the desired passband is the conjugate of the positive imaginary characteristic reactance of said first section of waveguide.

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US681637A 1966-06-10 1967-11-09 Waveguide filter utilizing evanescent waveguide, with tunable ferrite loading Expired - Lifetime US3639862A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB25966/66A GB1129185A (en) 1966-06-10 1966-06-10 Improvements in or relating to waveguide filters
GB53635/66A GB1136158A (en) 1966-06-10 1966-11-30 Improvements in or relating to waveguide filters

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US3639862A true US3639862A (en) 1972-02-01

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US (1) US3639862A (de)
BE (1) BE707294A (de)
CH (1) CH496331A (de)
ES (1) ES347787A2 (de)
FR (1) FR94324E (de)
GB (1) GB1136158A (de)
NL (1) NL6716345A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958194A (en) * 1975-01-03 1976-05-18 The United States Of America As Represented By The Secretary Of The Navy Frequency-sensitive attenuator
US4578655A (en) * 1983-01-19 1986-03-25 Thomson-Csf Tuneable ultra-high frequency filter with mode TM010 dielectric resonators
US5440278A (en) * 1994-03-25 1995-08-08 Bartholomew; Darin Ferrite system for modulating, phase shifting, or attenuating radio frequency energy
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
US20130328644A1 (en) * 2012-06-12 2013-12-12 Rs Microwave Company IN-LINE PSEUDOELLIPTIC TE01(n delta) MODE DIELECTRIC RESONATOR FILTERS

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112397853B (zh) * 2020-10-28 2021-12-14 中国电子科技集团公司第二十九研究所 一种可实现快速装卸和密封的波导法兰的连接装置

Citations (11)

* 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
US2816270A (en) * 1951-06-26 1957-12-10 Bell Telephone Labor Inc Microwave channel dropping filter pairs
US2849683A (en) * 1953-07-31 1958-08-26 Bell Telephone Labor Inc Non-reciprocal wave transmission
US2866949A (en) * 1953-10-29 1958-12-30 Bell Telephone Labor Inc Microwave circulators, isolators, and branching filters
US2920292A (en) * 1956-08-30 1960-01-05 Bell Telephone Labor Inc Power saturable wave guide components
US2989709A (en) * 1955-09-16 1961-06-20 Bell Telephone Labor Inc Magnetically controlled wave guide switch
US3013229A (en) * 1958-11-17 1961-12-12 Bell Telephone Labor Inc Gyromagnetic microwave filter devices
US3051908A (en) * 1960-02-03 1962-08-28 Bell Telephone Labor Inc Slow-wave broadband nonreciprocal microwave devices
US3215955A (en) * 1964-06-01 1965-11-02 Motorola Inc Waveguide switching by variable tuning of a cavity which shunts a band-pass filter
US3237134A (en) * 1963-03-26 1966-02-22 Gen Electric Microwave filter
US3496498A (en) * 1965-08-11 1970-02-17 Nippon Electric Co High-frequency filter

Patent Citations (11)

* 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
US2816270A (en) * 1951-06-26 1957-12-10 Bell Telephone Labor Inc Microwave channel dropping filter pairs
US2849683A (en) * 1953-07-31 1958-08-26 Bell Telephone Labor Inc Non-reciprocal wave transmission
US2866949A (en) * 1953-10-29 1958-12-30 Bell Telephone Labor Inc Microwave circulators, isolators, and branching filters
US2989709A (en) * 1955-09-16 1961-06-20 Bell Telephone Labor Inc Magnetically controlled wave guide switch
US2920292A (en) * 1956-08-30 1960-01-05 Bell Telephone Labor Inc Power saturable wave guide components
US3013229A (en) * 1958-11-17 1961-12-12 Bell Telephone Labor Inc Gyromagnetic microwave filter devices
US3051908A (en) * 1960-02-03 1962-08-28 Bell Telephone Labor Inc Slow-wave broadband nonreciprocal microwave devices
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
US3496498A (en) * 1965-08-11 1970-02-17 Nippon Electric Co High-frequency filter

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
B. Lax and K. J. Button Microwave Ferrites Pub. by McGraw Hill Book Co., N.Y. 1962, pp. 367 373 QC753L3. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958194A (en) * 1975-01-03 1976-05-18 The United States Of America As Represented By The Secretary Of The Navy Frequency-sensitive attenuator
US4578655A (en) * 1983-01-19 1986-03-25 Thomson-Csf Tuneable ultra-high frequency filter with mode TM010 dielectric resonators
US5440278A (en) * 1994-03-25 1995-08-08 Bartholomew; Darin Ferrite system for modulating, phase shifting, or attenuating radio frequency energy
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
US20130328644A1 (en) * 2012-06-12 2013-12-12 Rs Microwave Company IN-LINE PSEUDOELLIPTIC TE01(n delta) MODE DIELECTRIC RESONATOR FILTERS
US9190701B2 (en) * 2012-06-12 2015-11-17 Rs Microwave Company In-line pseudoelliptic TE01(nδ) mode dielectric resonator filters

Also Published As

Publication number Publication date
CH496331A (de) 1970-09-15
DE1541939B2 (de) 1975-10-30
DE1541939A1 (de) 1970-08-20
GB1136158A (en) 1968-12-11
FR94324E (fr) 1969-08-01
ES347787A2 (es) 1969-02-16
BE707294A (de) 1968-05-30
NL6716345A (de) 1968-05-31

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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