Coating processes – Electrical product produced – Metallic compound coating
Reexamination Certificate
1997-04-01
2001-05-22
Pascal, Robert (Department: 2817)
Coating processes
Electrical product produced
Metallic compound coating
C427S282000, C333S206000
Reexamination Certificate
active
06235341
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a high frequency dielectric filter device having a plurality of coaxial dielectric resonators arranged in parallel with each other.
There have been proposed various high frequency dielectric filter devices in which a dielectric substrate is provided with a plurality of through-holes which are formed in parallel with each other, each of the through-holes has a conductor layer arranged on its inner surface, and the dielectric substrate has an outer surface provided with an outer conductor which is connected with the inner conductor layers of the through-holes on one end surface of the dielectric substrate thereby to form a short-circuit surface, while the other end surface of the dielectric substrate is used as an open-circuit end surface. The high frequency dielectric filter devices having such an arrangement as stated above are used as a filter for a high frequency band. In this structure, a coaxial dielectric resonator is provided for each through-hole and thus a plurality of such resonators are arranged in parallel with each other.
An example of such conventional high frequency dielectric filter is shown in
FIG. 1
of the accompanying drawings in which a dielectric substrate A is provided with two coaxial dielectric resonators B which are juxtaposed to each other. Each dielectric resonator B comprises a through-hole extended from an open-circuit end surface C to a short-circuit surface (not shown) of the dielectric substrate A and provided with a conductor layer D. In order to couple coaxial dielectric resonators B with each other, a conventional means can be used as by, for example, forming a hole E or a slit penetrating from the open-circuit end surface C to the short-circuit surface of the dielectric substrate A as shown in
FIG. 1
or providing a counter-bore on the end portion of the formed coupling hole to enlarge the diameter of the portion.
With this kind of coupling, after the dielectric substrate is firstly formed to have a predetermined shape and inner and outer conductor layers are formed therein. Such a hole E or counter-bore should be formed at a high accuracy, with their widths and depths being decided, so that the production yield is low and difficulties are encountered in the manufacture of filters having equal characteristics. Further, the degree of coupling cannot be easily adjusted if it widely vary. In addition, there is another problem that the mechanical strength is deteriorated if the coupling hole is formed in the manner as stated above.
Meanwhile, in a case where a high frequency dielectric filter is adapted to telecommunications equipment such as portable wireless telephone or automobile telephone, it is often required that an attenuation pole should be provided at a frequency zone or position which is outside the intended frequency band and is apart from the center frequency by a predetermined frequency for isolating a transmitting signal from a receiving signal. To this ends, various arrangements have been attempted to satisfy this requirement. However, conventional means rely mainly on an external means such as a reactance element or the like for coupling coaxial dielectric resonators with each other and causes a problem in that the number of components is increased.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a high frequency dielectric filter device having means by which coupling of coaxial dielectric resonators with each other and polarization thereof can be achieved easily and simultaneously.
According to the present invention there is provided a high frequency dielectric filter device having a dielectric substrate in which a plurality of through-holes are formed in parallel with each other, each of the through-holes has an inner surface provided with a conductor layer, an outer surface of the dielectric substrate is provided with an outer conductor layer which is connected with the inner conductor layers of the through-holes on one end surface of the dielectric substrate thereby to form a short-circuit surface, and the other end surface of the dielectric substrate has no conductor layer and forms an open-circuit end surface, wherein the outer surface of the dielectric substrate is provided with a portion having no conductor layer which extends in a direction traverse to the through-holes and is arranged close to the short-circuit end surface.
In general, in a conventional high frequency dielectric filter device having coaxial dielectric resonators each including a through-hole are connected with each other through an electric field on the side of an open-circuit end surface, and are connected with each other through a magnetic field on the side of a short-circuiting end surface.
With the high frequency dielectric filter device according to the present invention, however, since the portion having no conductor layer is formed to be extended in the direction traverse to the through-holes on the outer peripheral surface close to the short-circuit end surface, the magnetic field does not tend to spread away toward the outer conductor layer, thereby intensifying the coupling through the magnetic field. Therefore, the coupling of the resonators through the magnetic field as a whole is stronger than the coupling through the electric field, and the resonators adjacent to each other are coupled by the magnetic field, thereby forming inter-stage coupling.
Further, the coupling of the resonators through the magnetic field has a strength equal to the coupling through the electric field in the high band side of center frequency. Therefore, an attenuation pole is formed in the high band side of the center frequency.
With the high frequency dielectric filter device according to the present invention, the portion having no conductor layer on the outer surface of the dielectric substrate is provided by forming a slit extending in the widthwise direction on the outer surface of the dielectric substrate by means of a dicing saw or the like so as to remove the outer conductor layer thereon. Such a slit may also be formed simultaneous with the press-processing of the dielectric substrate. In that case, the outer conductor layer can be prevented from sticking to the inside of the slit, by applying the outer conductor layer only onto the circumferential outer surface of the dielectric substrate. In this way, the portion having no conductor layer may be provided on the outer surface of the dielectric substrate. Alternatively, the portion having no conductor layer may be formed by partially removing the outer conductor layer arranged on the outer surface of the dielectric substrate in a strip-like shape by means of laser-trimming, sand-blasting or the like. Further, the portion having no conductor layer may be formed on the top surface of the dielectric substrate by means of patterning according to a screen printing method or the like while the outer conductor layer is formed.
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Larson & Taylor PLC
NGK Spark Plug Co. Ltd.
Pascal Robert
Summons Barbara
LandOfFree
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