US3471811A - Tunable microwave cavity using a piezoelectric device - Google Patents

Tunable microwave cavity using a piezoelectric device Download PDF

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Publication number
US3471811A
US3471811A US636334A US3471811DA US3471811A US 3471811 A US3471811 A US 3471811A US 636334 A US636334 A US 636334A US 3471811D A US3471811D A US 3471811DA US 3471811 A US3471811 A US 3471811A
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Prior art keywords
cavity
microwave
wall
microwave cavity
piezoelectric
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Expired - Lifetime
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US636334A
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English (en)
Inventor
Robert E Klotz
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Northrop Grumman Guidance and Electronics Co Inc
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Litton Precision Products Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P7/00—Resonators of the waveguide type
    • H01P7/06—Cavity resonators

Definitions

  • a piezoelectric device is affixed to a movable wall of a microwave cavity. Expansion and contraction of the piezoelectric material as a function of applied voltages is utilized to position the movable wall; and hence, tune the microwave cavity.
  • a microwave cavity a cavity including conductive walls, possesses electrical properties similar to the conventional tuned circuit consisting of an inductance and a capacitance at low radio frequencies.
  • a conductively walled enclosure or cavity possesses the familiar characteristics of resonance and impedance.
  • the frequency at which resonance occurs is primarily a function of cavity size or volume.
  • a microwave tuner may be constructed with a cavity utilizing a movable wall therewith that is adjustably positionable relative to the other cavity walls so as to increase or decrease the elfective size of the cavity, thereby lowering or raising the resonant frequency of the cavity.
  • a mechanically actuated movement for mechanically moving a cavity wall is relatively slow. Tuning at a relatively rapid rate is not possible due to mechanical inertia.
  • tuners are constructed utilizing conductive or dielectric rods or strips xedly placed within the cavity or adjustably positioned within the cavity by a screw or slot and screw arrangement.
  • ferroelectric devices are utilized as a tuner for a microwave cavity. In that instance, with a ferroelectric tuning device exposed to microwaves within a microwave cavity, the effective capacitance of the included ferroelectric; hence, the impedance of the microwave cavity, is adjustable with variations in the level of the voltage applied to the ferroelectric.
  • ferromagnetic or garnets exposed to microwaves are utilized as tuners for microwave cavities.
  • Electron discharge devices operable in the microwave frequency region such as the klystron and magnetron, contain tunable cavities for adjusting the output frequency of the device. Such tunable cavities are used for setting the electron discharge device to the desired frequency and to modulate the frequency of the electron discharge device for jamming radar stations, in addition to other more exotic applications of a modulated or swept signal. Additionally, tunable cavities are used as adjustable or variable impedances.
  • ferroelectric material possesses theoretical capabilities for purely electronic tuning without mov- ICC ing parts at relatively rapid rates, there are problems inherent in a relatively lossy ceramic ferroelectric material which render this alternative impractical in microwave cavities sustaining large magnitudes of microwave power. For example, at any signilicant power, the microwaves appearing within a microwave cavity heat a relatively lossy ceramic, such as the ferroelectric material, exposed to the elds within the cavity, causing it to decompose.
  • a microwave cavity having a plurality of conductive walls including a movable wall.
  • the movable wall is connected to a piezoelectric device that possesses the property of varying its dimensions as a function of applied electrical voltages. Accordingly, the movable wall is positioned and the cavity is tuned by the movement which occurs due to expansion and contraction of the piezoelectric as a function of the voltage applied to the latter.
  • the figure shows a microwave cavity 1 in section consisting of a plurality of conductively walled sides 2, 3, 4, 5, and 12.
  • the cavity contains a passage 7 for permitting the exit or entrance of microwave energy and other passages may be provided.
  • a support wall 6 is connected with the positionally iixed side walls 2, 3, and 5, and the unillustrated front wall to form a closed chamber containing the cavity 1.
  • Disposed within the formed chamber is an elongated piece of piezoelectric material 8, rectangular in cross section.
  • first conductive layer 10 Along two opposed sides of piezoelectric material 8 is a first conductive layer 10 and a second conductive layer 12, each of conductive material which forms, respectively, first and second electrodes.
  • Conductive layer 12 forms one wall or side of the cavity in addition to its function as an electrode for the piezoelectric material.
  • the piezoelectric material and electrodes are supported within the cavity 1 upon a layer of insulating material 9 and the bottom support wall 6.
  • the insulating layer 9 can be deleted if electrical isolation is not desired.
  • a rst electrical lead 13 is connected through wall 6, an insulator 14, through an opening in insulating layer 9, to electrode 10 in order to provide an electrical path for voltages from an electrical source, not illustrated.
  • a second electrical lead 15 is connected through wall 3 and through an insulator 16 to the second electrode 12 in order to provide a second conductive path for electrical voltages from an external source, not illustrated.
  • piezoelectric ymaterial is inuenced by the application of an electrical field across portions thereof.
  • the piezoelectric material By applying an electrical voltage between the two electrodes, the piezoelectric material very rapidly expands or contracts in an amount proportional to the magnitude and polarity of the applied voltages.
  • the direction of expansion and/or contraction is dependent on the direction of polarization Iand cut of the piezoelectric material.
  • the application of voltages from a source across electrical leads 13 and 15; hence, across electrodes 10 ⁇ and 12 provides expansion and contraction of piezoelectric material 8 in a vertical ⁇ directionin dependence upon the magnitude of the applied voltage at any instant.
  • the conductive layer 12 is thus positioned at various distances from upper wall 4 by such movement and Ivaries rthe sizeof the microwave cavity.
  • the source of voltages applied between electrical leads 13 ⁇ and 15 may be a periodically varying sweep voltage source, if periodic movement of the conductive layer 12 is desired.
  • the voltage source may be an adjustable DC source which is utilized to position conductive llayer 12 at a Idesired location and maintain such position.
  • the frequency of resonance of a microwave cavity is predominantly la function of the size of the cavity.
  • a movable cavity wall which borders a volume otherwise enclosed by other conductive walls changes the ⁇ frequency of resonance of the cavity as a function of the position of the movable wall.
  • the conductive layer 12 subsequentially extends about the entire bottom portion of the chamber and tfaces the upper wall 4, the conductive layer 12 effectively acts as the bottom wall of the volume vforming microwave cavity 1.
  • the clearances between the ends of wall 12 and walls perpendicular thereto, such as 3 and 5 in the figure, is small relative to the wavelength of the microwave energy in the range of frequencies for which the microwave cavity is used.
  • Each of the walls and 12 may be a metallic film deposited upon the piezoelectric material in any conventional manner, or alternatively, physically separate thin layers coupled mechanically to the piezoelectric layer at one or more locations.
  • the piezoelectric material 8 may be natural material or of the well known substances, such as Barium Titanate, which requires initially the application of a polarizing current to polarize the material.
  • the conductive wall or layer 12 substantially covers the piezoelectric material 8; hence, the piezoelectric material is effectively shielded or isolated from microwave energy 'appearing within cavity 1. This effectively prevents the microwave energy from heating the piezoelectric material.
  • the microwave cavity of ⁇ FIGURE 1 has been described as rectangular in cross-section, it is apparent that the cavity may be constructed in any shape including the common circular cross-section cylindrical cavities without detracting from the invention. For instance, by deleting reference to one of Ithe side walls and back walls, the remaining wall 10 may be considered cylindrical in shape and FIGURE 1 may be considered a cross-section of a cylindrical cavity. Likewise, similar preferencesl in the selection in the shape of the piezoelectric material and its electrodes are allowable and within the scope of the disclosed invention.
  • a microwave tuner comprising 'a microwave cavity having a plurality of conductive walls including: a movable wall; piezoelectric means connected to said movable wall; lirst and second electrodes connected to said piezoelectric means; means for lapplying voltages across said iirst and second electrodes comprising tirst and second

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US636334A 1967-05-05 1967-05-05 Tunable microwave cavity using a piezoelectric device Expired - Lifetime US3471811A (en)

Applications Claiming Priority (1)

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US63633467A 1967-05-05 1967-05-05

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US (1) US3471811A (fr)
FR (1) FR1570690A (fr)
GB (1) GB1187572A (fr)
SE (1) SE334184B (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3948350A (en) * 1974-12-20 1976-04-06 Honeywell Inc. Acoustic resonant cavity
US5596324A (en) * 1994-07-11 1997-01-21 Mcdonnell Douglas Corporation Electronic baffle and baffle controlled microwave devices
WO2004045018A1 (fr) * 2002-11-07 2004-05-27 Sophia Wireless, Inc. Filtres a resonateurs couples formes par micro-usinage
EP2013939A1 (fr) * 2006-04-27 2009-01-14 Powerwave Comtek Oy Element d'accord et resonateur pouvant etre accorde
EP2887449A1 (fr) * 2013-12-17 2015-06-24 Alcatel Lucent Filtre à cavité accordable
CN112955768A (zh) * 2018-08-27 2021-06-11 麻省理工学院 集合固态自旋传感器的微波谐振器读出

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2463472A (en) * 1945-03-16 1949-03-01 Premier Crystal Lab Inc Cavity resonator

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2463472A (en) * 1945-03-16 1949-03-01 Premier Crystal Lab Inc Cavity resonator

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3948350A (en) * 1974-12-20 1976-04-06 Honeywell Inc. Acoustic resonant cavity
US5596324A (en) * 1994-07-11 1997-01-21 Mcdonnell Douglas Corporation Electronic baffle and baffle controlled microwave devices
US5689262A (en) * 1994-07-11 1997-11-18 Mcdonnell Douglas Corporation Electronic baffle and baffle controlled microwave devices
US5847672A (en) * 1994-07-11 1998-12-08 Mcdonnell Douglas Corporation Electronic baffle and baffle controlled microwave devices
WO2004045018A1 (fr) * 2002-11-07 2004-05-27 Sophia Wireless, Inc. Filtres a resonateurs couples formes par micro-usinage
US20060232364A1 (en) * 2002-11-07 2006-10-19 Sophia Wireless,Inc. Coupled resonator filters formed by micromachining
US7449979B2 (en) 2002-11-07 2008-11-11 Sophia Wireless, Inc. Coupled resonator filters formed by micromachining
EP2013939A1 (fr) * 2006-04-27 2009-01-14 Powerwave Comtek Oy Element d'accord et resonateur pouvant etre accorde
US20100007442A1 (en) * 2006-04-27 2010-01-14 Powerwave Comtek Oy Tuning element and tunable resonator
US8149074B2 (en) 2006-04-27 2012-04-03 Powerwave Comtek Oy Tuning element and tunable resonator
EP2013939A4 (fr) * 2006-04-27 2012-12-26 Powerwave Comtek Oy Element d'accord et resonateur pouvant etre accorde
EP2887449A1 (fr) * 2013-12-17 2015-06-24 Alcatel Lucent Filtre à cavité accordable
CN112955768A (zh) * 2018-08-27 2021-06-11 麻省理工学院 集合固态自旋传感器的微波谐振器读出
EP3844517A4 (fr) * 2018-08-27 2022-10-05 Massachusetts Institute of Technology Lecture de résonateur à micro-ondes d'un capteur de spin à semi-conducteurs d'ensemble

Also Published As

Publication number Publication date
FR1570690A (fr) 1969-06-13
SE334184B (fr) 1971-04-19
GB1187572A (en) 1970-04-08

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