Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
2000-08-24
2003-03-04
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S219100, C333S234000
Reexamination Certificate
active
06529094
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dielectric resonance device including a cavity and a dielectric core disposed therein, as well as to a dielectric filter, a composite dielectric filter device, a dielectric duplexer, and a communication apparatus, each of which utilizes the dielectric resonance device.
2. Description of the Related Art
The applicant of the present application has filed Japanese patent application Nos. 10-220371 and 10-220372 for inventions in relation to dielectric resonators which are compact and facilitate formation of a multi-stage resonator. In the dielectric resonators of these applications, a substantially parallelepipedic dielectric core is disposed within a substantially parallelepipedic cavity, and the dielectric core is resonated in multiple modes.
Dielectric resonance devices in which a dielectric core is disposed within a cavity in an isolated manner typically employ a structure such that the dielectric core is supported at a predetermined position within the cavity via a support base.
FIGS. 16 and 17
shows an example of the structure, wherein
FIG. 16
is an exploded perspective view of a dielectric resonance device, and
FIG. 17
is a vertical cross section of the dielectric resonance device at the center thereof. In these drawings, reference numeral
3
denotes a parallelepipedic dielectric core, which is fixed to the bottom surface of a cavity body
1
via a support base
4
of low dielectric constant. A cavity lid
2
is placed on the top opened surface of the cavity body
1
.
When the dielectric core
3
of the dielectric resonance device resonates in a TM01&dgr;
−x
mode or in a TM01&dgr;
−y
mode, the resonance frequency varies with the capacitance which is present between inner walls of the cavity which face end surfaces of the dielectric core
3
, as indicated by a symbol of a capacitor in FIG.
17
. Therefore, if the linear expansion coefficients of the dielectric core and the support base differ from that of the cavity, the capacitance present between the peripheral surface of the dielectric core and the inner wall of the cavity will vary with temperature, with resultant variation in resonance frequency. The resonance frequency also varies in accordance with the temperature coefficient of the dielectric core.
FIGS. 18A and 18B
are graphs showing such variation in resonance frequency. In
FIG. 18A
, the horizontal axis represents time, and the vertical axis represents variation in resonance frequency relative to the resonance frequency at 25° C. In
FIG. 18B
, the horizontal axis represents temperature, and the vertical axis represents variation in resonance frequency relative to the resonance frequency at 25° C. In this example, when the temperature of the dielectric resonance device is lowered to −30° C., the resonance frequency of the TM01&dgr;
−x
mode and the resonance frequency of the TM01&dgr;
−y
mode decrease by 0.5 to 0.6 MHZ, and when the temperature of the dielectric resonance device is raised to +85° C., the resonance frequencies of these two modes increase by 0.7 to 0.8 MHZ.
Although the above-described temperature characteristics of the resonance frequencies can be improved through employment of a material of low linear expansion coefficient, such as invar or 42%-nickel iron alloy, this increases cost. Further, when in addition a TE01&dgr; mode of the dielectric core is utilized in a dielectric resonance device having a structure as shown in
FIGS. 16 and 17
, the temperature characteristic of this mode raises another problem. That is, the resonance frequency of the TE01&dgr; mode does not relate directly to the capacitance between the peripheral portion of the dielectric core and the inner wall of the cavity but depends on the size of the cavity and the temperature coefficient of the dielectric core. In the example case shown in
FIG. 18
, the resonance frequency of the TE01&dgr; mode increases by about 0.3 MHZ as a result of a temperature decrease to −30° C. and decreases by about 0.4 MHZ as a result of a temperature increase to +85° C. The directions of these variations are completely opposite those in the case of the TM01&dgr;
−x
mode and the TM01&dgr;
−y
mode. Accordingly, the above-described TM01&dgr; modes differ from the TE01&dgr; mode in terms of temperature characteristic of the resonance frequency, thereby raising a different problem, that the overall frequency characteristic of the resonance device varies with temperature.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention provides a dielectric resonance device which has a stabilized temperature characteristic of a TM-mode resonance frequency, which would otherwise vary due to differences in linear expansion coefficient among a dielectric core, a support base, and a cavity.
The invention further provides a dielectric filter, a composite dielectric filter device, a dielectric duplexer, and a communication apparatus, each of which utilizes the dielectric resonance device.
The present invention also provides a dielectric resonance device with reduced variation in the frequency characteristic with temperature in a multi-mode operation utilizing TM and TE modes, as well as a dielectric filter, a composite dielectric filter device, a dielectric duplexer, and a communication apparatus, each of which utilizes the dielectric resonance device.
The present invention provides a dielectric resonance device comprising: an electrically conductive cavity; a dielectric core fixedly disposed within the cavity via a support base, the dielectric core being capable of resonating in a TM mode; and a capacitance-generation electrode having the same electrical potential as that of the cavity and provided at a predetermined position between an inner wall surface on which the support base is fixed and a support-base attachment surface of the dielectric core through which the dielectric core is attached to the support base, such that a capacitance is produced between the electrode and the support-base attachment surface of the dielectric core.
As a result of employment of this structure, when temperature varies, the size of a gap between the peripheral surface of the dielectric core and the inner wall surface of the cavity and the size of a gap between a circumferential portion of the support-base attachment surface of the dielectric core and the electrode change in directions opposite each other. Therefore, variation in the capacitance between the dielectric core and the cavity is suppressed, so that the resonance frequency of the TM mode is stabilized.
The electrode may be a stepped portion which is provided inside the cavity such that a surface of the stepped portion faces a circumferential portion of the support-base attachment surface of the dielectric core.
In this case, since the stepped portion provided inside the cavity serves as an electrode which faces a circumferential portion of the support-base attachment surface of the dielectric core, the characteristics can be improved without increase in the number of components.
Alternatively, the electrode may be an electrically conductive member, for example a plate, attached to the inner wall surface of the cavity such that the conductive member or plate faces a circumferential portion of the support-base attachment surface of the dielectric core.
In this case, since the electrode is provided through attachment of the conductive member or plate, the structure of the cavity before attachment of the conductive member or plate is simple, and therefore the cavity can be fabricated with ease. Further, the characteristics can be switched or adjusted by selectively changing the shape of the conductive member or plate and/or the manner or location of its attachment.
Alternatively, the electrode may be a member such as a screw which projects toward the interior of the cavity.
In this case, the temperature characteristic of the dielectric resonance device can be optimized with ease through adjustment of
Kubo Hiroyuki
Nakatani Yukihiro
Dickstein , Shapiro, Morin & Oshinsky, LLP
Jones Stephen E.
Murata Manufacturing Co. Ltd.
Pascal Robert
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