US3278868A - Cavity resonator - Google Patents

Cavity resonator Download PDF

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Publication number
US3278868A
US3278868A US417367A US41736764A US3278868A US 3278868 A US3278868 A US 3278868A US 417367 A US417367 A US 417367A US 41736764 A US41736764 A US 41736764A US 3278868 A US3278868 A US 3278868A
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Prior art keywords
cavity
resonator
coupling
recess
frequency
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Expired - Lifetime
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US417367A
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English (en)
Inventor
Kach Alfred
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Patelhold Patenverwertungs and Elektro-Holding AG
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Patelhold Patenverwertungs and Elektro-Holding AG
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B19/00—Generation of oscillations by non-regenerative frequency multiplication or division of a signal from a separate source
    • H03B19/16—Generation of oscillations by non-regenerative frequency multiplication or division of a signal from a separate source using uncontrolled rectifying devices, e.g. rectifying diodes or Schottky diodes
    • H03B19/18—Generation of oscillations by non-regenerative frequency multiplication or division of a signal from a separate source using uncontrolled rectifying devices, e.g. rectifying diodes or Schottky diodes and elements comprising distributed inductance and capacitance
    • 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

  • the present invention relates to cavity resonators yfor use in connection with the transmission of microwaves, and more particularly, though not limitatively, to an improved coupling or impedance matching arrangement for the feeding to and extraction of the microwave energy from a cavity resonator serving as an intermediate transmission or circuit element of a microwave system designed especially for operation within the higher frequency range known as the X-band of the microwave spectrum, and beyond.
  • cavity resonators In the transmission of microwave energy it is common practice to utilize cavity resonators as impedance matching devices or transformers.
  • Such resonators consist in a known manner of a hollow space bounded by metallic walls and having a shape and dimension such as to cause the structure, upon excitation through suitable coupling means, to resonate at a desired frequency, whereby to set up a definite electric and magnetic field distribution pattern within the cavity being characteristic of the special type or construction of resonator being used.
  • Coupling between the resonator and the associated input and output circuits or devices is effected -by means of inductive and/ or capacitative coupling elements, such as probe, loop, or slit couplings operably connecting the resonator with the microwave transmission system. Because of the relatively large surface area of the resonators, their transmission losses are relatively small, aside from the advantage of ruggedness of construction and ease of operation, well known to those skilled in the art.
  • the most-common form of cavity resonator utilizes a circular cylindrical resonating space, whereby the field distribution or pattern within the cavity is determined by the cylinder -functions of the structure.
  • the fundamental or so-called B01-mode of oscillation is e-mployed, in which case the electric field is vertical or at right angle to the end walls or cover plates of the cylinder and the magnetic field is circular and coaxial with the cylinder axis of the resonator.
  • suitable tuning means are employed preferably consisting of an adjustable tuning plug of conducting material and mounted in either of the end walls of the resonator, to variably project into the cavity.
  • a cavity resonator of the referred to type represents an intermediate transformer in the manner of an ordinary -four-pole circuit, for the reason that the distributed basic constants, that is, the inductance and capacitance, behave like lumped values as far as the effect on the external circuits is concerned.
  • the coupling elements advantageously consist of magnetic coupling loops for effecting connection with a coaxial transmission line, or of coupling slits or apertures for effecting connection with an input or output cavity.
  • a coupling loop has the special advantage of enabling a simple and effective impedance matching and frequency band Patented Oct. 11, 1966 ICC width control of the resonator to a desired value by the t proper design or size as well as the orientation of the loop.
  • the electrical length of the wire remain at a value below M4 at the highest operating 4frequency for which the resonator is designed to operate.
  • an important object of the present invention is the provision of a cavity resonator of the re-ferred to type embodying an improved coupling arrangement which is substantially devoid of the afore-mentioned and related drawbacks and defects inherent in the prior art arrangements and which is especially suited for operation in the higher range of the microwave Ifrequency spectrum, and beyond.
  • a more specific object of the invention is the provision of an improved coupling arrangement for cavity resonators designed for use in connection with operating frequencies within and beyond the upper range of the microwave frequency spectrum, which arrangement is both devoid of the drawbacks and defects of the previously known coupling devices and which will enable simple and effective impedance matching control within a predetermined operating frequency range and over a substantial range of working resistance variations.
  • Yet another object of the invention is the provision of an improved coupling arrangement for cavity resonators, especially for use in connection with operating frequencies in the higher microwave frequency range and beyond, which arrangement is especially suitable for direct incorporation therein of a diode or the like conversion element, such as a variable capacitance diode as used in harmonic frequency multipliers, parametric converters or amplifiers, or the like systems or devices.
  • a diode or the like conversion element such as a variable capacitance diode as used in harmonic frequency multipliers, parametric converters or amplifiers, or the like systems or devices.
  • FIG. 1 is a longitudinal cross-section through a cavity resonator and improved coupling arrangement constructed in accordance with the principles of the invention
  • FIG. 2 is a plan view of the resonator of FIG. 1, shown with the cover thereof removed;
  • FIG. 3 is a fragmentary view of FIG. l, showing an alternative output coupling of the resonator
  • FIG. 4 illustrates a resonator according to the preceding figures embodying a variable capacitance diode, to act as a harmonic frequency multiplier
  • the invention involves generally the provision of a main cavity being preferably, though not limitatively, of a cylindrical shape and bounded by a pair of opposed end walls connected by a side wall, with a nichelike lateral recess communicating with said main cavity and extending outwardly from said side wall, said recess having a dimension in the direction of the axis of said end walls, or in the direction of the electric eld set up within said cavity, being substantially less than the spacing distance between said end walls, or length of the electric iield lines wit-hin said cavity, to provide an lintermediate coupling space between said main cavity and the associated circuit element or device of a microwave transmission system in which the resonator is connected.
  • coupling with said recess is effected through the inner conductor of a coaxial coupling element extending into the recess in a direction parallel to said axis and at a point relatively remote from the transition region between said cavity and said recess, while the degree of coupling is controlled by the provision of suitable first tuning means within said recess, consisting preferably of a tuning plug disposed at a point within or relatively close to the transition region between the recess and said cavity.
  • microwave energy may be transmitted through said resonator within a predetermined operating Ifrequency range and at high etliciency or optimum impedance matching with the associate transmission circuits or devices, by the proper control and adjustment of the lirst and second tuning means, respectively, in a manner as will become further apparent as the description proceeds.
  • the invention utilizes an auxiliary cavity or space as a transition means to the main cavity, in such a manner as to overcome the ditiiculties involved in the use of a coupling loop according to the prior art arrangements, especially for operation in the higher frequency range of the microwave spectrum and beyond.
  • An ancillary advantage of such arrangement is the possibility of a direct structural embodiment of insertion of a diode or the like solid state conversion element in the coaxial coupling element, to thereby eliminate the prior ditiiculties pointed out when using a loop as a coupling means, as will be further understood from the description of the drawings as follows.
  • the numeral 1 denotes the cavity of a microwave resonator having a pair of end walls and a side wall and comprised, in the example shown, of a circular cylindrical casing 3 closed by a cover 2.
  • a rotatable, threaded tuning plug 4 mounted in the bottom Iwall of and coaxially with the casing 3 is a rotatable, threaded tuning plug 4 the projection of which into said cavity may Abe varied in a known manner for the tuning of the resonator to a desired resonating frequency, said plug being electrically connected with the bottom of the casing through a number of flat or nger-like contact springs 4a.
  • a magnetic coupling loop 5 which serves for the extraction of the microwave energy from the resonator cavity and feeding to a coaxial cable 6, in the example illustrated.
  • any other known coupling means may be employed, such as an aperture or slit coupling 13 feeding a load or output cavity 12, as shown in FIG. 3.
  • a coaxial input coupling 7 having, Ifor instance, a low-ohmic impedance of say less than 50 ohms which it is desired to match with a given load or output impedance, of say 50 ohms, by the resonator acting as an impedance transformer.
  • the cavity 1 is fitted, in accordance with the lpresent invention, with an auxiliary cavity in the form of a relatively flat niche or recess 8 being parallel to the end walls of the cylinder or main cavity and extending laterally outwardly from the casing 3, in the manner shown.
  • the niche or recess 8 is traversed in the axial direction by the inner conductor 9 of the coaxial coupling element 7 being disposed at a point relatively remote from the transition region between the cavity 1 and recess 8.
  • the recess 8 is fitted with a further tuning plug 10 disposed in or near said transition region.
  • a further recess or depression 11 is provided in the bottom of the niche S and in line with the plug 10 for the extension of the adjusting or coupling range of the latter.
  • FIG. 2 is a plan view -of the resonator shown by FIG. 1 with 'the cover 2 removed.
  • the niche 8 may have the form of a semi-circular recess within the casing 3 and, similarly, recess 11 may be of semi-circular shape, as shown in the drawing.
  • the shape of the niche is by no means critical and may be, for instance rectangular, if desirable for fabricating or other reasons.
  • the width of the niche or recess 8 is advantageously about equal to the diameter of the cavity 1, or somewhat less, as 4s-h-own in FIG. 2.
  • the spacing distance between the axes of the coupling conducto-r 9 and -of the tuning plug 10, FIG. l is principally non-critical and determined mainly by practical and design considerations. For ordinary purposes, it has been found advantageous to utilize a spacing distance between elements 9 and 10 of the order of between 4 to M8, where )t represents the operating frequency in free space.
  • the height of the niche 8 may be varied within substantial limits without essentially affecting the transformation or impedance mat-ching characteristics of the device.
  • the height of the niche should be substantially less than the height of the cavity 1, or spacing distance between the end walls of the cavity, its upper limit being about one half of the height of said cavity.
  • the two tuning plugs 4 and 10 mea-ns for the tuning land coupling control of the resonator, respectively, whereby to enable the matching of input and output impedance values diifering by a ratio as large as 20:1 and for operating frequencies varying withi-n a range of 15:1, while maintaining the transmission eiciency substantially constant throughout the operation.
  • the function of the niche 8 may be explained by the circular magnetic field produced by the current through the conductor 9 not only reaching into and faintly directly exciting the main cavity 1, but additionally exciting to a substantially higher degree the plug 10 acting as a series-resonant substitute network or circuit.
  • the magnetic field set up by the plug 10 embraces the conductor 9, on the one hand, as well as the tuning plug 4, on the other hand, in such 'a manner lthat the ensuing interaction between the various fields results in a definite coupling between the conductor 9 and the cavity 1, determined by the -adjusting position, or natural resonance, of the plug 10 in relation to the operating frequency.
  • adjustment may be effected by alternately displaci-ng the tuning plugs 4 .and 10 until the output energy of the resonator assumes a maximum, while the total operating bandwidth of the resonator is determined by the degree of the output coupling, that is, the size and orientation of the loop 5, in the example illustrated by FIG. 1.
  • the resonating frequency proper of the resonator is practically not affected by the presencel of the niche 8, as long as the height of the latter remains less than about one half of the height of the cavity 1, in the manner pointed out.
  • any other suitable shape ⁇ of the resonator may be used for the purposes of the invention, such for instance as a resonator having a rectangular shape or cross-section.
  • a similar recess or niche coupling as shown may be used for the coupling of the resonator with its load or output circuit or device, that is, taking the pla'ce of the coupling loop 5 shown in FIG. 1.
  • the form of Aa conventional P-N junction are reversely biased by a suitable direct current source (not shown), whereby to exhibit a voltage-dependent capacitance effect within a substantial operating range.
  • a suitable direct current source not shown
  • the fundamental frequency or applied input oscillation is dis- Y torted lto produce -a large number of harmonics one or more of which areextracted or segregated by the resonator, in
  • the circular cylindrical cavity 1, consisting of the casing 3 and cover 2 is fitted with a coaxial line 6 as an output device.
  • the coaxial input element 7 serves for applying the fundamental frequency to be multiplied, while a variable capacitance diode 14, in-
  • the frequency multiplier or harmonic generator according to FIG. 4 operates by the fundamental frequency f being applied to the variable capacitance diode 14 via the coaxial line 7 and the capacitance formed by the inner conduetor 15 of said line and the casing 3.
  • the dimension of the inner conductor andof the -air gap, ⁇ or capacitance, are chosen in such -a manner ⁇ as to cause the line 7 and the capacitance to form a transformer resonating at the frequency f, to result in the generation of a mixt-ure of harmonics of said fundamental frequency by the diode 14.
  • a desired 'component of frequency nf, with n representing the multiplication factor, may be extracted by the proper design or adjustment of the tuning plug 4 of the cavity 1, in a manner understood from the foregoing.
  • FIG. 5 illustrates another example of a practical application of the invention as embodied in -a so-called parametric up-converter or frequency transformer.
  • the converter or frequency mixer comprises a pair of adjoining resonating cavities 1 and 1' composed of a common casing 3 and cover 2 and embodying a common variable capacitance diode 14.
  • the cavity 1 is excited via the coupling loop 5 and coaxial line 6 by the microwave oscillation of relatively low frequency f1 to be converted, for which purpose 1 the cavity is tuned to the frequency f1 by means of the tuning plug 4.
  • Output coupling is effected through the niche 8' and by the aid of the tuning or coupling plug 10', said niche being traversed by the variable capacitance diode 14, in the same manner as described hereinbefore.
  • further microwave oscillation having an intermediate frequency f2 by which the input frequency f1 is to be increased is applied through the coaxial line 7, whereby the 1 diode 14, forming part of the inner conductor of the line, causes both oscillations to be intermixed in the manner customary in the operation of parametric converters or amplifiers.
  • the inner conductor of the line 7 and the capacitance formed thereby and the casing 3 act as parts of the transformer resonant to the frequency f2.
  • the diode 14 simultaneously .traverses the niche or recess 5 of the cavity 1 which is -itted with a tuning plug 4.
  • Both niches 8 and 8' in the exampleshown, communicate with one another, to form a common space between the main cavities 1 and 1' centrally traversed by the line 7.
  • output energy at the sum frequency fyi-f2 may be extracted or derived from the cavity 1 by proper adjustment of the plugs 4 and 10 respectively, in a manner readily understood from the foregoing.
  • the composite cavity structure shown by FIGS. 4 and 5 may further be utilized as an input or output circuit or coupling for a multi-section bandpass filter or network.
  • the cavity 1 may be designed for a frequency f and cavity 1 may be designed for twice the frequency or 2f, while the intermediate circuit formed by the output conductor 7 may be short-circuited for high-frequency currents. If in such a case high-frequency energy of frequency 2f ⁇ is fed from a suitable pumping oscillator through the line 6 and if line 6 is connected with .a point of a wel-l-known circulator, the arrangement shown constitutes Ia so-called negative resistance parametric amplifier in respect Ito the input and output ends ⁇ of the circulator, in a manner well known in the art.
  • the multiple cavity arrangement according to FIG. 5 may be advantageously used in connection with a harmonic generator according to FIG. 4, by applying the fundamental frequency to the line 7 and deriving a pair of harmonics from the cavities 1 and 1' by the proper tuning and coupling adjustment, in the manner described.
  • additional cavities may be arranged radially around the ⁇ diode 14 disposed in a common recess, for the utilization of a corresponding number of harmonics derived from the respective cavities.
  • the diode may be directly or closely coupled with Ithe cavity resonator.
  • the transformation losses may be kept below 1 db over .a ran-ge or bandwidth of 50 mc.
  • a cavity resonator comprising in combination:
  • said recess having a dimension in the direction of the axis of said end walls being substantially less than the spacing distance between said end walls
  • a coaxial coupling element having an outer conductor and an inner conductor, said inner conductor extending into said recess in a direction parallel to said axis and located at a point relatively remote from the transition region -between saidcavity and said recess, and
  • adjustable tuning means located in said transition region.
  • a cavity resonator as claimed in claim 1 said tuning means being comprised of a tuning plug mounted in a wall of said recess and adjustable in a direction parallel to said axis.
  • a cavity resonator as claimed in claim 1 the dimension of said recess in the direction of said axis being of the order of from 1/s-l/a of the distance between said end walls.
  • a cavity resonator as claimed in claim 1 including a diode element serially structurally embodied in said inner conductor, to form an input for said cavity, further tuning means for said cavity to adjust the resonating frequency thereof, and output coupling means operably associated with said main cavity.
  • a cavity resonator as claimed in claim 1 including a variable capacitance diode serially structurally embodied in said inner conductor, to form an input for applying thereto a rst frequency, and further tuning means for said cavity for adjusting the resonating frequency thereof, to excite the same at a harmonic of said rst frequency.
  • a multiple cavity resonator comprising a pair of adjoining resonator units as defined by claim 1, each said liits including a cavity and a recess with the recesses of the units communicating with one another and traversed by a common central coaxial conductor, to provide a lirst coupling means for both said cavities, and individual tuning and second coupling means operably associated with each of said cavities.
  • a cavity resonator comprising in combination:
  • a resonant cylindrical cavity having a pair of opposed end walls and a cylindrical side wall
  • said recess having a width substantially equal to the diameter of said cavity and a height substantially less than the spacing distance between said end walls
  • a coaxial coupling element having an outer conductor and an inner conductor spaced therefrom, said inner conductor extending into said recess in a direction parallel to the cylinder axis and located at a point relatively remote from the transition region between said cavity and said recess, and
  • adjustable tuning means located in the transition region between said cavity and said recess.
  • said tuning means consisting of a tuning plug variably extending into said recess in a direction parallel to the cylinder axis.
  • a cavity resonator as claimed in claim 10 said recess having a depression in line with said plug, to extend the adjusting range thereof.
  • a cavity resonator as claimed in claim 12, said further tuning means consisting of a coaxial adjustable tuning plug operably associated with said cavity.
  • a cavity resonator comprising in combination:
  • said recess having a dimension in the direction of said lines being substantially less than the length of said lines
  • a tuning plug substantially parallel to said conductor and adjustably mounted in the wall of said recess, to variably project in-to said region.

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US417367A 1963-12-17 1964-12-10 Cavity resonator Expired - Lifetime US3278868A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1543563A CH404741A (de) 1963-12-17 1963-12-17 Hohlraumresonator für Mikrowellen

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US3278868A true US3278868A (en) 1966-10-11

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US (1) US3278868A (xx)
AT (1) AT245050B (xx)
CH (1) CH404741A (xx)
DE (1) DE1181290B (xx)
FR (1) FR1418716A (xx)
GB (1) GB1035379A (xx)
NL (2) NL146002B (xx)
SE (1) SE304043B (xx)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3351842A (en) * 1964-12-23 1967-11-07 Orest J Hanas Coaxial diode cartridge
US3371264A (en) * 1965-09-01 1968-02-27 Air Force Usa Tuned cavity assembly for harmonic generation of acoustic and electromagnetic waves of gigacycle frequencies
US3546633A (en) * 1966-01-04 1970-12-08 Gen Electric Electrically tunable microwave band-stop switch
US4386326A (en) * 1979-08-07 1983-05-31 Matsushita Electric Industrial Co., Ltd. Dielectric-resonator-tuned microwave solid state oscillator
US20040257073A1 (en) * 2003-04-10 2004-12-23 Helmut Greim Antenna element and antenna arrangement for magnetic resonance applications

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2899647A (en) * 1959-08-11 Frequency selector of microwaves

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2899647A (en) * 1959-08-11 Frequency selector of microwaves

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3351842A (en) * 1964-12-23 1967-11-07 Orest J Hanas Coaxial diode cartridge
US3371264A (en) * 1965-09-01 1968-02-27 Air Force Usa Tuned cavity assembly for harmonic generation of acoustic and electromagnetic waves of gigacycle frequencies
US3546633A (en) * 1966-01-04 1970-12-08 Gen Electric Electrically tunable microwave band-stop switch
US4386326A (en) * 1979-08-07 1983-05-31 Matsushita Electric Industrial Co., Ltd. Dielectric-resonator-tuned microwave solid state oscillator
US20040257073A1 (en) * 2003-04-10 2004-12-23 Helmut Greim Antenna element and antenna arrangement for magnetic resonance applications
US7268550B2 (en) * 2003-04-10 2007-09-11 Siemens Aktiengesellschaft Antenna element and antenna arrangement for magnetic resonance applications

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Publication number Publication date
CH404741A (de) 1965-12-31
SE304043B (xx) 1968-09-16
NL146002B (nl) 1975-05-15
FR1418716A (fr) 1965-11-19
NL7503524A (nl) 1975-07-31
DE1181290B (de) 1964-11-12
AT245050B (de) 1966-02-10
GB1035379A (en) 1966-07-06
NL6412747A (xx) 1965-06-18

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