CA1202385A - Electrical resonators - Google Patents
Electrical resonatorsInfo
- Publication number
- CA1202385A CA1202385A CA000451963A CA451963A CA1202385A CA 1202385 A CA1202385 A CA 1202385A CA 000451963 A CA000451963 A CA 000451963A CA 451963 A CA451963 A CA 451963A CA 1202385 A CA1202385 A CA 1202385A
- Authority
- CA
- Canada
- Prior art keywords
- resonator
- conductor
- dielectric
- electrical
- ground plane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P7/00—Resonators of the waveguide type
- H01P7/10—Dielectric resonators
Landscapes
- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
Abstract of the Disclosure A dielectric resonator consists of a body of dielectric material mounted in close proximity to a microstrip line with which a high frequency electrical signal is coupled. The resonance frequency of the resonator is altered and adjusted by varying the level of a d.c. bias voltage applied to two varactor diodes which form part of an inductive closed circuit mounted adjacent to the end of the body which is remote from the microstrip line. By varying the bias level, the resulting change in inductance causes the resonance frequency to alter in a controlled manner over an appreciable frequency range.
Description
~z~
This invention relates to electrical resona-tors and is specifically concerned with resonators which comprise one or more bodies of a shaped dielectric material. Resonators of this kind are usually mounted adjacent to a ground plane and are arranged to operate at very high frequencies, typically of the order of a Gigahertz or more. It is, at present, customary to operate a resonator at a single predetermined centre frequency which is determined by the shape and size of the dielectric body and the housing in which it is mounted. The present invention seeks to provide an electrical resonator which can be readily and rapidly adjusted so as to operate at a variable resonant fre-quency.
According to this invention a frequency selective resonator includes a body of dielectric material which is mounted on an electrical insulator which serves to space it apart from a ground plane, an electrical conductor haviny a variable inductance associated therewith located adjacent to said body but spaced apart therefrom so as to influence the external electromagnetic field of said body, and means for receiving an electrical signal which is utilized to vary said inductance so as to adjust and control the resonant frequency of said resonator.
Typically, a frequency selective resonator which is Eormed out of a body of dielectric material is mounted upon one surface of an electrically in-sulating plate, the opposite surface of which is in contact with a ground plane. Conveniently an electri-cal signal is communicated to said dielectric resonator by means of a microstrip line formed upon the upper surface of said dielectric plàte. I'he resonant fre-quency of said dielectric resonator is dependent on the characteristics of its external electromagnetic field. In practice the electric field is almost r~
entirely confined to the physical surface of the resonator and the external field is largely due to the magnetic contribution.
Tuning is achieved by placing an electrical conductor adjacent to one surface of the resonator, and altering its effective inductance, preferably by vary-ing the bias applied to a diode which is connected to said conductor. Preferably the conductor and one or more diodes form a closed electrical path around which current can circulate under the influence of the external electromagnetic field. The electrical con-ductor is preferably positioned adjacent to an end face of the dielectric resonator which is remote from the ground plane. Because of the presence of the ground plane the magnetic field lines tend to extend through those end faces which ar~ parallel with the ground plane and the magnetic field can be greatly influenced by positioning the tuning means so as to intercept these field lines. ~he electrical conductor can be provided ~0 in several sections which are lin]ced by respective diodes to form the closed electrical path~
The invention is further described by way of example with reference to the accompanying drawing in which:-Figure 1 shows a sectional perspective view of a frequency selective resonator, and Figure 2 is an explanatory diagram.
Referring to Figure 1, a frequency selective resonator comprises a solid cylindrical body 1 of dielectric material which is mounted upon a microstrip circuit assembly comprising an electrically insulating alumina substrate 2, having an electrical groundplane 3 on its lower surface. An elongate electrically con- ;
ductive track 4 is formed upon its upper surface and in operation a signal is applied from an external source to the track 4 to generate an electromagnetic field which couples into the body 1. Dielectric materials for this purpose are now well known, and a range of suitable materials is available. Fre-quently the materials are composed of ceramic mixtures containing titanium dioxide, various titanates or zirconates. The resonance frequency of the resonator is determined primarily by the physical size and shape of the body 1. These devices are further described in a Paper by J.K. Plourde, IEEE Transactions on Microwave Theory and Techniques, page 754, Volurne MTT/29, No. 8, August, 1981.
. Although the frequency characteristics of a dielectric resonator are generally fixed by its physical shape and size, the invention permits its resonant frequency to be varied over an appreciable range. Typically, in this example, the centre frequency of resonance of the dielectric resonator is of the order of 7 GHz and the invention permits that value to be readily altered over a range of typically 50 MHz. The resonance properties of the dielectric resonator are also stron~ly affected by the characteristics of any conductive housing within which it is situated. In this example, the microstrip circuit is mounted on the base-plate 5 of a container having walls 6 and 7 and a top plate 8. In practice all four walls will be provided to constitute a sealed chamber having a removable lid, and in some applications more than just a single dielectric resonator may be provided within the same housing.
Conveniently, the top plate 8 is detachable sa that access is available to the interior of the chamber.
Electrical tuning of the dielectric resonator is achieved by the provision of two semicircular annular conductive tracks 9 and 10, formed of gold, which have a diameter conforming with that of the cylindrical dielectric body 1. However the tracks are spaced apart from the top surface 11 of the di-J3~35 electric material by means of a quartz spacer 12. Anadditional very thin electrically insulating spacer disc 13 is positioned above the quartz spacer 12 so as to support and secure the conductive tracks 9 and 10. In practice, the spacer disc 13 may not be necessary, in which case the yold tracks are bonded directly on to the quartz. Small gaps are left between the ends of the tracks 9 and 10 and these are electric-ally bridged by a pair of varactor diodes 14 and 15.
Small recesses can be formed in the supporting spacer 13 so as to accommodate the electrical connections which are made to these varactor diodes. If the spacer 13 is not provided, the varactor diodes are mounted directly on the gold tracks, so the recesses may not be necessary. It is necessary to provide the quartz spacer so that the presence of the electrically conductive tracks and the varactor diodes do not adversely affect the resonance mode of oscillation within the dielectric body itself. A variable d.c. voltage bias is applied to the varactor diodes via leads 16, 17 which are attached to the gold tracks 9, 10.
In operation, a high frequency electrical signal is applied to the microstrip conductor ~ from an external source, not shown, and the electromagnetic field which it produces couples into the dielectric body 1 to induce resonance. When in resonance, the body 1 produces an external electromagnetic field, but in practice the electric component of the field is almost entirely confined to the interior of the body, whilst the external magnetic com~onent is significant.
This magnetic component is believed to couple with the conductive tracks 9 and 10, to cause induced currents to flow around the closed loop which is formed with the varactor diodes 14 and 15. The conductive tracks are very thin, but are formed of gold so as to exhibit an extremely low electrical resistance.
~zJ~s The presence of the varactor diodes intro-duces an inductive component into the circuit so formed, and this inductance modifies the electro-magnetic field associated with the dielectric resona-tor, thereby altering its resonance frequency.
It has been found that the effect can be quite appreciable, and Figure 2 shows the e~Efect on the resonance frequency by altering the d.c. bias which is applied to the two varactor diodes. It will be seen that a small reverse bias of -1 volt produces the lowest resonance frequency and that increasing the bias progressively to about 15 volts produces a corresponding increase in resonance frequency. The variation of resonance frequency with voltage bias is not linear but is steepest in the area in which the applied bias is near to zero. Typically the frequency of resonance can be altered from f0 to fl, where the difference between these two frequencies is of the order of about 50 MEIz.
Although two varactor diodes 14 and 15 are illustrated in combination with two semicircular conductive tracks 9 and 10, the other configurations are possible. For example a circular annular conductor can be provided having only a single break which is bridged by one varactor diode but an extra capacitive break is needed to avoid shorting out the varactor diode~ On the other hand, additional breaks can be provided as desired, each of which is bridged by an appropriate diode or other device by means of which the inductance associated with the loop can be altered and controlled.
This invention relates to electrical resona-tors and is specifically concerned with resonators which comprise one or more bodies of a shaped dielectric material. Resonators of this kind are usually mounted adjacent to a ground plane and are arranged to operate at very high frequencies, typically of the order of a Gigahertz or more. It is, at present, customary to operate a resonator at a single predetermined centre frequency which is determined by the shape and size of the dielectric body and the housing in which it is mounted. The present invention seeks to provide an electrical resonator which can be readily and rapidly adjusted so as to operate at a variable resonant fre-quency.
According to this invention a frequency selective resonator includes a body of dielectric material which is mounted on an electrical insulator which serves to space it apart from a ground plane, an electrical conductor haviny a variable inductance associated therewith located adjacent to said body but spaced apart therefrom so as to influence the external electromagnetic field of said body, and means for receiving an electrical signal which is utilized to vary said inductance so as to adjust and control the resonant frequency of said resonator.
Typically, a frequency selective resonator which is Eormed out of a body of dielectric material is mounted upon one surface of an electrically in-sulating plate, the opposite surface of which is in contact with a ground plane. Conveniently an electri-cal signal is communicated to said dielectric resonator by means of a microstrip line formed upon the upper surface of said dielectric plàte. I'he resonant fre-quency of said dielectric resonator is dependent on the characteristics of its external electromagnetic field. In practice the electric field is almost r~
entirely confined to the physical surface of the resonator and the external field is largely due to the magnetic contribution.
Tuning is achieved by placing an electrical conductor adjacent to one surface of the resonator, and altering its effective inductance, preferably by vary-ing the bias applied to a diode which is connected to said conductor. Preferably the conductor and one or more diodes form a closed electrical path around which current can circulate under the influence of the external electromagnetic field. The electrical con-ductor is preferably positioned adjacent to an end face of the dielectric resonator which is remote from the ground plane. Because of the presence of the ground plane the magnetic field lines tend to extend through those end faces which ar~ parallel with the ground plane and the magnetic field can be greatly influenced by positioning the tuning means so as to intercept these field lines. ~he electrical conductor can be provided ~0 in several sections which are lin]ced by respective diodes to form the closed electrical path~
The invention is further described by way of example with reference to the accompanying drawing in which:-Figure 1 shows a sectional perspective view of a frequency selective resonator, and Figure 2 is an explanatory diagram.
Referring to Figure 1, a frequency selective resonator comprises a solid cylindrical body 1 of dielectric material which is mounted upon a microstrip circuit assembly comprising an electrically insulating alumina substrate 2, having an electrical groundplane 3 on its lower surface. An elongate electrically con- ;
ductive track 4 is formed upon its upper surface and in operation a signal is applied from an external source to the track 4 to generate an electromagnetic field which couples into the body 1. Dielectric materials for this purpose are now well known, and a range of suitable materials is available. Fre-quently the materials are composed of ceramic mixtures containing titanium dioxide, various titanates or zirconates. The resonance frequency of the resonator is determined primarily by the physical size and shape of the body 1. These devices are further described in a Paper by J.K. Plourde, IEEE Transactions on Microwave Theory and Techniques, page 754, Volurne MTT/29, No. 8, August, 1981.
. Although the frequency characteristics of a dielectric resonator are generally fixed by its physical shape and size, the invention permits its resonant frequency to be varied over an appreciable range. Typically, in this example, the centre frequency of resonance of the dielectric resonator is of the order of 7 GHz and the invention permits that value to be readily altered over a range of typically 50 MHz. The resonance properties of the dielectric resonator are also stron~ly affected by the characteristics of any conductive housing within which it is situated. In this example, the microstrip circuit is mounted on the base-plate 5 of a container having walls 6 and 7 and a top plate 8. In practice all four walls will be provided to constitute a sealed chamber having a removable lid, and in some applications more than just a single dielectric resonator may be provided within the same housing.
Conveniently, the top plate 8 is detachable sa that access is available to the interior of the chamber.
Electrical tuning of the dielectric resonator is achieved by the provision of two semicircular annular conductive tracks 9 and 10, formed of gold, which have a diameter conforming with that of the cylindrical dielectric body 1. However the tracks are spaced apart from the top surface 11 of the di-J3~35 electric material by means of a quartz spacer 12. Anadditional very thin electrically insulating spacer disc 13 is positioned above the quartz spacer 12 so as to support and secure the conductive tracks 9 and 10. In practice, the spacer disc 13 may not be necessary, in which case the yold tracks are bonded directly on to the quartz. Small gaps are left between the ends of the tracks 9 and 10 and these are electric-ally bridged by a pair of varactor diodes 14 and 15.
Small recesses can be formed in the supporting spacer 13 so as to accommodate the electrical connections which are made to these varactor diodes. If the spacer 13 is not provided, the varactor diodes are mounted directly on the gold tracks, so the recesses may not be necessary. It is necessary to provide the quartz spacer so that the presence of the electrically conductive tracks and the varactor diodes do not adversely affect the resonance mode of oscillation within the dielectric body itself. A variable d.c. voltage bias is applied to the varactor diodes via leads 16, 17 which are attached to the gold tracks 9, 10.
In operation, a high frequency electrical signal is applied to the microstrip conductor ~ from an external source, not shown, and the electromagnetic field which it produces couples into the dielectric body 1 to induce resonance. When in resonance, the body 1 produces an external electromagnetic field, but in practice the electric component of the field is almost entirely confined to the interior of the body, whilst the external magnetic com~onent is significant.
This magnetic component is believed to couple with the conductive tracks 9 and 10, to cause induced currents to flow around the closed loop which is formed with the varactor diodes 14 and 15. The conductive tracks are very thin, but are formed of gold so as to exhibit an extremely low electrical resistance.
~zJ~s The presence of the varactor diodes intro-duces an inductive component into the circuit so formed, and this inductance modifies the electro-magnetic field associated with the dielectric resona-tor, thereby altering its resonance frequency.
It has been found that the effect can be quite appreciable, and Figure 2 shows the e~Efect on the resonance frequency by altering the d.c. bias which is applied to the two varactor diodes. It will be seen that a small reverse bias of -1 volt produces the lowest resonance frequency and that increasing the bias progressively to about 15 volts produces a corresponding increase in resonance frequency. The variation of resonance frequency with voltage bias is not linear but is steepest in the area in which the applied bias is near to zero. Typically the frequency of resonance can be altered from f0 to fl, where the difference between these two frequencies is of the order of about 50 MEIz.
Although two varactor diodes 14 and 15 are illustrated in combination with two semicircular conductive tracks 9 and 10, the other configurations are possible. For example a circular annular conductor can be provided having only a single break which is bridged by one varactor diode but an extra capacitive break is needed to avoid shorting out the varactor diode~ On the other hand, additional breaks can be provided as desired, each of which is bridged by an appropriate diode or other device by means of which the inductance associated with the loop can be altered and controlled.
Claims (8)
1. A frequency selective resonator including a body of dielectric material which is mounted on an electrical insulator which serves to space it apart from a ground plane, an electrical conductor having a variable inductance associated therewith located adjacent to said body but spaced apart therefrom so as to influence the external electromagnetic field of said body; and means for receiving an electrical signal which is utilized to vary said inductance so as to adjust and control the resonant frequency of said resonator.
2. A resonator as claimed in claim 1 and wherein said body of dielectric material is mounted upon one surface of an electrically insulating plate, the opposite surface of which is in contact with a ground plane.
3. A resonator as claimed in claim 2 and wherein said plate and ground plane form part of a microstrip circuit, by means of which an electrical signal is coupled to said dielectric body.
4. A resonator as claimed in claim 3 and wherein the microstrip circuit includes a conductive track formed upon that surface of said plate which supports said body, with the track being spaced apart from the body itself.
5. A resonator as claimed in claim 2 and wherein said conductor is positioned adjacent to an end face of the dielectric resonator which is remote from said ground plane.
6. A resonator as claimed in claim 5 and wherein said electrical conductor is associated with a diode, the bias of which is variable so as to vary its effective inductance.
7. A resonator as claimed in claim 6 and wherein the conductor is spaced apart from the body of dielectric material by a quartz spacer.
8. A resonator as claimed in claim 5, 6 or 7 and wherein said electrical conductor consists of two semicircular portions, with two varactor diodes respectively positioned to bridge the two gaps in the conductor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8316637 | 1983-06-18 | ||
| GB08316637A GB2141880B (en) | 1983-06-18 | 1983-06-18 | Electrical resonators |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1202385A true CA1202385A (en) | 1986-03-25 |
Family
ID=10544449
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000451963A Expired CA1202385A (en) | 1983-06-18 | 1984-04-13 | Electrical resonators |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1202385A (en) |
| GB (1) | GB2141880B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2153598B (en) * | 1984-01-26 | 1987-04-08 | British Telecomm | Microwave resonator device |
| FR2565438B1 (en) * | 1984-05-30 | 1989-09-22 | Cepe | DIELECTRIC FILTER WITH VARIABLE CENTRAL FREQUENCY. |
| US4683447A (en) * | 1986-12-01 | 1987-07-28 | Eaton Corporation | Varactor tuning circuit for dielectric resonator stabilized oscillator |
| GB9002120D0 (en) * | 1990-01-31 | 1990-03-28 | Marconi Co Ltd | Dielectric resonant oscillator |
| JP2897117B2 (en) * | 1995-09-19 | 1999-05-31 | 株式会社村田製作所 | Variable frequency dielectric resonator |
-
1983
- 1983-06-18 GB GB08316637A patent/GB2141880B/en not_active Expired
-
1984
- 1984-04-13 CA CA000451963A patent/CA1202385A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2141880A (en) | 1985-01-03 |
| GB2141880B (en) | 1986-08-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |