JPH0695602B2 - Dielectric filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dielectric filter having an integral structure for use in a high frequency band such as microwaves, and more specifically, in the vicinity of a lead wire connecting a coupling capacitor and a terminal portion. The present invention relates to a dielectric filter in which a dielectric member is arranged to facilitate adjustment of impedance.

[Prior Art] A multistage resonator type filter using a dielectric ceramic such as barium titanate has a small loss and therefore a so-called high Q, and has a large permittivity, so that it can be miniaturized. It is widely used in mobile radio equipment for wave bands and satellite communication equipment.

As a conventional technique relating to a dielectric filter, a plurality of resonator holes and connector holes are alternately provided at predetermined intervals in the longitudinal direction of a substantially rectangular parallelepiped dielectric block, and the resonator holes of the dielectric block are provided. There is an integrated multi-stage structure in which a metallized layer (for example, a conductor layer baked with silver paste or the like) is formed on the entire outer surface except one of the open surfaces and the inner surface of the resonator hole.

Here, one of the surfaces where the resonator holes are opened and where the metallized layer is not formed is called an open surface, and is usually housed in a metal case with the open surface facing upward.

There are various methods for connection with an external circuit, but a typical one is a structure using a coupling capacitor. In the prior art, a structure is employed in which a coupling capacitor is mounted and fixed at the open ends of the resonator holes located at both ends of the dielectric block, and the input / output terminals attached to the housing are connected by lead wires.

In a dielectric filter having such a structure, each resonator hole corresponds to one resonance element, and the desired degree of filter characteristics can be obtained by providing an appropriate degree of coupling by means of the connector holes located between the resonator holes. Is causing.

[Problems to be Solved by the Invention] However, in the above-described conventional dielectric filter, since the coupling capacitor and the terminal portion are connected by the lead wire, the impedance is high due to the L component (inductance component). In addition, since there are variations in the length of the lead wire, the forming of the wiring, and the like, there is a drawback that adjusting the impedance with respect to the input signal is complicated and the characteristics tend to be unstable, and the adjustment takes time. In particular, if the lead wire becomes long, the impedance may become too high and adjustment may not be possible.

The object of the present invention is to eliminate the drawbacks of the prior art as described above, the impedance can be easily adjusted in a short time,
Moreover, it is to provide a dielectric filter having stable characteristics.

[Means for Solving the Problems] In the present invention that can achieve the above object, a plurality of resonator holes are arranged in the longitudinal direction of a dielectric block having a substantially rectangular parallelepiped shape, and the dielectric block is provided. Of one of the surfaces where the resonator hole is opened as an open surface, a metallization layer is formed on the outer surface other than the open surface and the inner surface of the resonator hole, and the metallized layer is formed at the open end of the resonator hole located at the end. A dielectric filter having a lead wire connected between the attached coupling capacitor and a terminal portion, wherein a dielectric member different from the dielectric block is arranged near the lead wire.

Here, the dielectric member may have any shape such as a cylindrical shape or a cylindrical shape with a slit. Examples of the material thereof include barium titanate having a dielectric constant of about 36 to 90. These dielectric members are fixed to the housing or the dielectric block.

INDUSTRIAL APPLICABILITY The present invention is suitable for, for example, a transmission side filter of a dielectric duplexer.

[Operation] If a dielectric member is placed near the lead wire connecting the coupling capacitor and the terminal part, stray capacitance can be collected and a C component (electrostatic capacitance component) can be provided, and the impedance can approach 50Ω. Adjustment becomes easy.

This impedance adjustment can be performed by exchanging the dielectric member, shifting the position, or scraping.

After the adjustment is completed, the dielectric member may be fixed at that position with an adhesive.

Since the lead wire is held by the dielectric member in the middle part,
It is difficult to deform and move, and stable characteristics can be obtained.

[Embodiment] FIG. 1 is a perspective view showing an embodiment of a dielectric filter according to the present invention, excluding a housing, and FIG. 2 is a partial vertical sectional view thereof. This embodiment is an example of a four-stage structure used as a transmission side filter of a dielectric demultiplexer.

The basic structure of the dielectric filter is the same as that of the above-mentioned conventional technique.

The dielectric filter has four resonator holes 12 formed at intervals in the longitudinal direction of a substantially rectangular parallelepiped dielectric block 10 made of a sintered body of a high dielectric constant ceramic material such as barium titanate. A coupler hole 14 is provided between the resonator holes 12, and a metallization layer 16 is further formed on all side surfaces and the bottom surface of the dielectric block 10 and on the inner surface of each resonator hole 12, and a metal casing (Fig. (Not shown). Here, the upper surface of the dielectric block 10 is an open surface and the lower surface is a short circuit surface.

At the open ends of the resonator holes located at both ends of the dielectric block 10, coupling capacitors 18 and 19 are provided with rivet-shaped mounting hardware 17
The input terminal 20 and the output terminal 21 are attached to the housing 30 by being mounted and fixed via. And coupling capacitors 18,19
The input terminals 20 and the output terminals 21 are electrically connected by lead wires 22 and 23.

The present invention is significantly different from the prior art in that the dielectric member 24 is provided in the vicinity of the lead wire 22 connecting the coupling capacitor 18 and the input terminal 20.

In this embodiment, the dielectric member 24 has a cylindrical shape. Then, the lead wire 22 covered with the insulating tube 26 is inserted through the inside of the cylindrical dielectric member 24, and the dielectric member 24 is fixed to the inner wall of the metal housing 30 with an adhesive.

In addition, in the accompanying drawings, in order to make the drawings easy to understand, the portions where the base material of the dielectric is exposed as it is without metallization are shown with fine dots. Although the metallized layer 16 is drawn to have a considerable thickness in these drawings, it is actually an extremely thin layer formed by baking silver paste as described above.

When the dielectric member 24 is present in the vicinity of the lead wire 22 connecting the coupling capacitor 18 and the input terminal 20 as described above, the C component (capacitance component) increases and the L component (inductance component) of the lead wire 22. Is canceled out and the impedance becomes close to 50Ω system, and the adjustment becomes easy.

Moreover, the impedance can be adjusted by exchanging the dielectric member 24, shifting the mounting position, or cutting a part of the dielectric member 24. Therefore, the adjustment becomes much easier than the conventional configuration using only lead wires.

After completion of the adjustment, if the lead wire 22 and the dielectric member 24 are fixed with an adhesive, the lead wire is maintained in shape and its characteristics are stable. The dielectric member 24 is fixed to the inner wall of the housing or the dielectric block with an adhesive or the like.

Here, the dielectric member 24 is preferably made of a material having a dielectric constant of about 36 to 90, such as barium titanate. This is because if the dielectric constant is too small, the impedance adjustment will be insufficient and the shape of the dielectric member will be large, and if the dielectric constant is too large, the dielectric member will be too small to be practical.

The coupling capacitor 19 and the output terminal 21 are connected only by the lead wire 23 as in the conventional case.

FIG. 3 shows an example of another dielectric member used in the present invention. This embodiment shows a cylindrical dielectric member 34 having a slit 32 formed in the axial direction. Providing such a slit 32 makes it extremely easy to insert the lead wire.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to such a configuration.
The shape of the dielectric member, the number of attached dielectric members, and the like may be appropriately changed. Therefore, for example, one or a plurality of small dielectric beads may be arranged in series.

Although the above embodiment is a case of a four-stage filter, the present invention can be applied to a two-stage or three-stage filter and a multi-stage filter having five or more stages. Further, in the above-mentioned embodiment, the connector holes are provided between the resonator holes, but it is also possible to generate desired filter characteristics by forming an appropriate conductor pattern on the open surface without providing the connector holes. Needless to say, the present invention can be applied to such a filter.

The dielectric member may be installed at any place where impedance adjustment is required. Therefore, not only one side of the dielectric block but also the input and output sides may have such a connection structure. The present invention can be applied to other than the filter on the transmission side of the dielectric duplexer.

[Effects of the Invention] The present invention connects the coupling capacitor attached to the open end of the resonator hole located at the end of the dielectric block with the lead wire as described above, and the dielectric member in the vicinity thereof. Since the dielectric filter is arranged, the impedance is close to the 50Ω system and adjustment is easy, and the impedance of the input signal can be reduced by exchanging the dielectric member, shifting it from the mounting position, or cutting a part. Since adjustment is possible, it is much easier to adjust compared to the conventional connection using only lead wires, and the characteristics are stable because it is easy to maintain a constant shape, and the adjustment work time is shortened and the yield is improved. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a dielectric filter according to the present invention, excluding a housing, and FIG. 2 is a partial vertical cross-sectional view thereof.
The figure is a perspective view showing another example of the dielectric member. 10 ... Dielectric block, 12 ... Resonator hole, 14 ... Coupler hole, 16
… Metallization layer, 18… Coupling capacitor, 20… Input terminal,
22 ... Lead wire, 24 ... Dielectric member.

Claims (3)

[Claims] 1. A dielectric block having a substantially rectangular parallelepiped shape is provided with a plurality of resonator holes in the longitudinal direction, and one surface of the dielectric block in which the resonator holes are opened is defined as an open surface, and the resonator block is opened. A dielectric filter in which a metallized layer is formed on the outer surface other than the surface and the inner surface of the resonator hole, and a lead wire connects between the coupling capacitor attached to the open end of the resonator hole located at the end and the terminal. 2. A dielectric filter, wherein a cylindrical dielectric member different from the dielectric block is arranged, and the lead wire is inserted through the inside of the cylindrical dielectric member. 2. The dielectric member has a cylindrical shape and is fixed to an inner wall of a housing which houses the dielectric block.
The dielectric filter described. 3. The dielectric filter according to claim 1 or 2, wherein the dielectric filter is a transmitting filter of the dielectric duplexer, and the terminal portion is an input terminal thereof.