Dielectric resonator device

Abstract: A dielectric heat-radiator of a thin plate form is pressed against a dielectric resonator on the side remote from a surface to which a dielectric support is bonded and supported elastically with nuts and springs by support columns each fixed to a metal baseplate at one end thereof, so as to adjust the frequency by processing the electromagnetic energy transmitted through the dielectric heat-radiator. In consequence, heat generated in the dielectric resonator upon receiving a high-power high-frequency signal is allowed to propagate efficiently to the dielectric heat-radiator having a high heat conductivity through the wide contact surface.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a dielectric resonator device used mainly in high-power high-frequency radio equipments. 2. Description of the Prior Art Heretofore, the dielectric resonator device has been often used in high-frequency radio equipments as a resonator which has a high Q factor not only in the microwave band but also in the UHF band. A conventional dielectric resonator device is constructed such that a cylindrical dielectric resonator to which a dielectric support is bonded with the use of glass is fixed within a metal case provided with a loop-like electrode through which high-frequency signals are received and delivered, by screwing the dielectric support, and an opening of the metal case is closed by a metal cover having a tuning screw so as to shield the device. The dielectric resonator is magnetically combined with the loop-like electrode so as to resonate at a specific frequency determined by the dielectric constant, the shape and the type of resonance mode to be used for the resonator. Adjustment of the resonance frequency is performed by moving the tuning screw to and away from the dielectric resonator. It is possible to reduce the size of the dielectric resonator device by increasing the dielectric constant of the resonator. On the other hand, it is possible to make the dielectric resonator device operate as a band-pass filter by providing two electrodes which serve as input/output terminals, respectively. The filter of such construction is widely used as the channel filter of the transmitter multiplexer equipped in the mobile radio base station as shown in the literature, for example (K. Wakino, et al., "800 MHz band miniaturized channel dropping filter using low loss dielectric resonator", Denshi Tokyo No. 24, 1985, pp. 72-75). In the dielectric resonator device, electromagnetic energy for resonation is stored inside the dielectric resonator and in the vicinity thereof. For this reason, when a metal conductor is brought close to the dielectric resonator, high-frequency current flows on the surface of the conductor so as to cause a loss in electromagnetic energy due to resistance, thereby deteriorating the characteristics of the resonator. Therefore, it is necessary to consider that the internal structure of the metal case of the dielectric resonator device is so designed as not to allow any metal to approach the dielectric resonator to cause the loss of electromagnetic energy. Further, part of the electromagnetic energy stored inside and in the vicinity of the dielectric resonator is converted into heat within the dielectric resonator and the dielectric support due to a dielectric loss. The dielectric support is made of a material which has a small dielectric constant and causes less high-frequency loss, and it is designed that most of the electromagnetic energy is stored in the dielectric resonator which exhibits a large dielectric constant so that the dielectric loss is almost caused in the dielectric resonator. Heat generated in the dielectric resonator is radiated by way of the following two routes. One of them is to radiate heat from the dielectric support due to heat conduction, and the other one is to radiate heat from the surface of the dielectric resonator through the air within the metal case. However, in addition to the above conditions, there is a certain condition in selecting the material of the dielectric support such that the coefficient of thermal expansion of the material must be identical with that of the dielectric resonator because they are bonded to each other by use of glass. Any of the dielectric materials of high heat conductivity which are known at present cannot satisfy these conditions. In consequence, in the dielectric resonator of the conventional structure, the amount of heat radiated from the dielectric support was very small. Further, in such a case that the dielectric resonator is reduced in size while the dielectric constant or working frequency thereof is increased, it becomes difficult to radiate heat from the surface of the dielectric resonator since the surface area thereof is small. In the dielectric resonator device of such construction, when a high-power high-frequency signal is fed thereto, the temperature of the dielectric resonator rises to cause the problems including an increase in high-frequency loss and a drift of resonance frequency of the dielectric resonator. In order to solve the above-mentioned problems, there has hitherto been proposed a method in which bar dielectrics are inserted into a drum dielectric resonator from above and below and fixed thereto so as to radiate heat as disclosed in Japanese patent Unexamined publication No. 1-109802. This method, however, has the problems that dimensional accuracy of the drum dielectric resonator and the bar dielectrics and the roughness of the contact surface make it difficult to reduce the contact thermal resistance and that it is impossible to extend the frequency variable range since the tuning mechanism and the resonator cannot be opposed to each other from the viewpoint of structure, in addition to the problem that it is not applicable to the cylindrical dielectric resonator. US-PS-4,580,116 teaches a dielectric resonator comprising a dielectric resonator element as well as a dielectric disc member on the top thereof, said dielectric disc member serving as a support for a pattern of metalization. What is known from FR-A-2284200 is a dielectric resonator comprising a dielectric resonator element as well as a wafer between said resonator element and the head of a screw of fixing said resonator element. Said wafer has a diameter smaller than that of said dielectric resonator element. US-A-4,667,172 teaches a construction including a resonator and two compensating discs on the top and the bottom thereof. Said discs are on the one hand thicker than said resonator and have, on the other hand, a diameter which is the same as that of the resonator. EP-A-0351 840 discloses two dielectric discs each having a central aperture, between which discs a dielectric cylinder is interposed. Said dielectric discs serve for supporting purposes. The upper and lower surfaces of the dielectric resonator are not made into press-contact with said dielectric discs, except their peripheral edges. An object of the present invention is to provide a small type dielectric resonator device which can be used at a high power and radiate heat with a high degree of efficiency from a dielectric resonator without deteriorating high-frequency characteristics of the resonator device when it receives a high-power high-frequency signal. According to the invention, the above object is achieved by a dielectric resonator device comprising a metal casing incorporating electrodes through which high frequency signals are transmitted; a dielectric resonator having first and second surfaces which are opposite to each other, and incorporated in said metal casing so as to be bonded, at said first surface, to a dielectric support attached to said metal casing and a thin disc-like dielectric heat-radiator having a diameter lager than that of said dielectric resonator and a thickness thinner than that of said dielectric resonator, and being pressed against said second surface of said dielectric resonator. Preferably, a tuning member is attached to said metal casing so as to be opposed to said dielectric heat-radiator whereby said tuning member is adapted to act upon electromagnetic energy passing through said dielectric heat-radiator so as to adjust frequencies. According to a further preferred embodiment, the metal casing is composed of a bottom plate and a cover, said dielectric support being made into contact with said bottom plate, and support columns are planted at their proximal ends on said bottom plate and are provided at their distal ends with springs by which said dielectric heat-radiator is pressed against said bottom plate. Finally, it is preferred that the dielectric heat-radiator is made of a dielectric material containing alumina or magnesia as a main component. With the arrangement according to the invention, heat generated from the dielectric resonator propagates through the wide contact surface to the dielectric heat-radiator of high heat conductivity, resulting in that a temperature rise of the dielectric resonator can be retained. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a sectional view illustrating a dielectric resonator device according to a first embodiment of the present invention; Figure 2 is a sectional view illustrating a dielectric resonator device according to a second embodiment of the invention; and DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 is a sectional view of a dielectric resonator device in a first embodiment of the present invention. Referring to Figure 1 loop-like electrodes 21 through which a high-frequency signal is received and delivered are disposed within a metal case (of cylindrical form) 12, and a dielectric resonator (of cylindrical form) 23 is bonded to a dielectric support 24 by use of glass and, then, the dielectric support 24 is fixed within the metal case 12 by fastening a screw 29. A disc-like dielectric heat-radiator 25 pressed against a surface of the dielectric resonator 23 on the side remote from the surface to which the dielectric support 24 is bonded and, then, fixed by means of elements 26a, 26b or the like. An opening in the metal case 12 is closed by a metal cover 28 attached with a tuning screw 27, 27a so as to shield the inside of the case in its entirety. Heat generated caused by a dielectric loss of the dielectric resonator 23 upon delivery of a high-power high-frequency signal is radiated through the contact surface between the dielectric resonator 23 and the dielectric heat-radiator 25 due to heat conduction. with the above construction, it is easy to obtain a large area of the contact surface between the dielectric resonator 23 and the dielectric heat-radiator 25 as well as to reduce the thermal contact resistance by polishing the contact surfaces. Since the force by which the dielectric heat-radiator 25 is pressed against the dielectric resonator 23 is not applied as tensile force but as pressing force to the glass-bonded portion between the dielectric resonator 23 and the dielectric support 24, there is no possibility of damage of the glass-bonded portion even if the pressing force is increased. In consequence, it is possible to stably maintain a small thermal contact resistance between the dielectric resonator 23 and the dielectric heat-radiator 25 and the mechanical strength can be increased as well. In Figure 1, loop-like electrodes 21 through which a high-frequency signal is received and delivered are disposed within the metal case (of cylindrical form) 12, and columnar dielectric resonator 23 is bonded, to columnar dielectric support 24 by use of glass and, then the dielectric support 24 is fixed within the metal case 12 by fastening screw 29, as explained above. Dielectric heat-radiator 25 of a thin plate form (or a disc form) is pressed against a surface of the dielectric resonator 23 on the side remote from the surface to which the dielectric support 24 is bonded and, then, fixed by means of screws 26a and attachment 26b. An opening in the metal case 12 is closed by a metal cover 28 attached thereto with a tuning screw 27 having an end plate (disc-shaped) 27a, so as to shield the inside of the case in its entirety. The tuning screw 27 is so arranged as to be opposed to the contact surface between the dielectric heat-radiator 25 and the dielectric resonator 23 for serving to adjust the frequency by processing the electromagnetic energy transmitted through the dielectric thin plate heat-radiator 25. In this embodiment, as explained above, since the frequency is adjusted by processing the electromagnetic energy transmitted through the dielectric thin plate heat-radiator 25, it is possible to obtain a large area through which the plate end 27a of the tuning screw 27 faces the dielectric resonator 23. It is therefore possible to have a very large frequency variable range. The fundamental principle of the frequency adjusting method of this embodiment, that is, the idea of processing the electromagnetic energy transmitted through the dielectric plate has been already disclosed in the U.S. Patent (USP 4628283) as a method of shielding an oscillator using a dielectric resonator. However, the method of fixing the dielectric resonator has offered a critical problem in the high-power dielectric resonator device, which is solved by the present invention, the above-mentioned U.S. Patent neither discloses nor suggests the method of fixing the dielectric resonator which is available at a high electric power. For example, a method of bonding the dielectric resonator and the dielectric plate to each other by a resinous adhesive cannot be used because the resin of the adhesive is deteriorated by the high-frequency signal, and therefore, the above mentioned U.S. Patent cannot solve this problem. In the present invention, the above-described principle is applied to the original fixing method that the dielectric plate heat-radiator is pressed against a surface of the dielectric resonator on the side remote from the surface to which the dielectric support is bonded. Further, in the present embodiment, since the dielectric heat-radiator which is to be pressed against the dielectric resonator is formed in the shape of a thin plate and hence has a small volume, a part of the electromagnetic energy expected to be stored in the dielectric resonator, that is, the electromagnetic energy expected to exist within the dielectric heat radiator, can be made small in capacity. As a result, a loss of dielectromagnetic energy due to a dielectric loss of the electric heat-radiator can be kept small and, at the same time, the difference between the resonance frequency obtained when the dielectric resonator is used alone and the resonance frequency obtained when the dielectric resonator is used in contact with the dielectric heat-radiator as well as the difference between the temperature coefficients of the resonance frequencies of the respective cases can be kept small and therefore, it is possible to facilitate the design of the dielectric resonator. In addition, although the dielectric heat radiator is small in size since it is formed in the shape of plate, the area of the contact surface which is one of factors determining the thermal contact resistance between the dielectric heat-radiator and the dielectric resonator remains unchanged, and therefore, the radiation characteristic is not deteriorated. In consequence, the thickness of the dielectric heat-radiator can be made thin so far as the thermal resistivity does not become a problem. Figure 2 is a sectional view of a dielectric resonator device according to a second embodiment of the present invention. Referring to Figure 2, a loop-like electrode 31 through which a high-frequency signal is transmitted is attached to a metal baseplate 32, and a dielectric resonator (of cylindrical form) 33 is bonded to a dielectric support 34 by use of glass and, then, the dielectric support 34 is set on the metal baseplate 32 with a concave 34a thereof being fitted on a positioning protrusion 32a formed on the metal baseplate 32. A dielectric heat-radiator 35 of a thin plate form (or disc form) is pressed against the dielectric resonator 33 from a surface thereof on the side remote from the surface to which the dielectric support 34 is bonded. The dielectric heat-radiator 35 is fixed to support columns 36 by means of nuts and springs 38, one end of each support column 36 being fixed to the metal baseplate 32. A metal case (of cylindrical form) 40 attached with a tuning screw 39 having a plate (disc-shaped) end 39a is mounted on the metal baseplate 32 so as to cover and shield the inside of the case in its entirety. The tuning screw 39 is so arranged that the plate end 39a is opposed to the contact surface between the dielectric heat-radiator 35 and the dielectric resonator 33, for adjusting the frequency by processing the electromagnetic energy transmitted through the dielectric thin plate heat-radiator 35. The result of experiments shows that the dielectric thin plate heatradiator 35 is preferably made of alumina, magnesia and the like. In the first embodiment, since the difference between the thermal expansion of the dielectric resonator and the dielectric support and the thermal expansion of the support columns is absorbed through the deflection of the dielectric heat-radiator, the strength thereof is not high. However in this second embodiment, since the difference in thermal expansion is absorbed by using the springs 38, the dielectric heat-radiator can be completely prevented from being damaged. Further, according to this embodiment, since attaching of the dielectric heat-radiator can be carried out in the state where the metal case is removed, it is possible to eliminate defective in manufacturing by visibly confirming the state of contact between the dielectric resonator and the dielectric heat-radiator.

Claims: A dielectric resonator device comprising a metal casing (12, 28; 32, 40) incorporating electrodes (21; 31) through which high frequency signals are transmitted; a dielectric resonator (23; 33) having first and second surfaces which are opposite to each other, and incorporated in said metal casing (12, 28; 32, 40) so as to be bonded, at said first surface, to a dielectric support (24; 34) attached to said metal casing (12; 32) and a thin disc-like dielectric heat-radiator (25; 35) having a diameter larger than that of said dielectric resonator (23; 33) and a thickness thinner than that of said dielectric resonator (23; 33), and being pressed against said second surface of said dielectric resonator (23; 33). A dielectric resonator device as set forth in claim 1, characterized in that a tuning member (27; 39) is attached to said metal casing (28; 40) so as to be opposed to said dielectric heat-radiator (25; 35), whereby said tuning member (27; 39) is adapted to act upon electromagnetic energy passing through said dielectric heat-radiator (25; 35) so as to adjust frequencies. A dielectric resonator device as set forth in claim 1 or 2, characterized in that said metal casing is composed of a bottom plate (32) and a cover (40), said dielectric support (34) being made into contact with said bottom plate (32), and support columns (36) are planted at their proximal ends on said bottom plate (32) and are provided at their distal ends with springs (38) by which said dielectric heat-radiator (35) is pressed against said bottom plate (32). A dielectric resonator device as set forth in any preceding claim, characterized in that said dielectric heat-radiator (25; 35) is made of a dielectric material containing alumina or magnesia as a main component.

Inventors: HATANAKA MASAMI, ISHIZAKI TOSHIO, HATANAKA, MASAMI, ISHIZAKI, TOSHIO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1991
Main classification: H01P7
IPC codes: H01P7