JPH0744367B2 - Input / output coupling structure of dielectric filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dielectric filter mainly used in a microwave band, and more specifically, it forms a groove without a conductive film on a longitudinal end face of a dielectric resonator. The present invention relates to an input / output coupling structure in which the coupling position can be freely changed by inserting the electrode part of the input / output terminal.

This filter is used in fields such as mobile communications such as car telephones and satellite communications.

[Prior Art] As a dielectric filter, a plurality of resonator holes are arranged side by side in the longitudinal direction of a substantially rectangular parallelepiped dielectric block, and one of the surfaces (open surface) where the resonator holes are open There is one using a λ / 4 type dielectric coaxial resonator in which a conductor film is formed on the surface and the inner wall surface of the resonator hole.

There are various input / output coupling structures of such a dielectric filter. A coupling capacitor is attached to the open ends of the resonator holes located at both ends, and a conductor is inserted inside the resonator hole via another dielectric. There is a method, a method in which another hole is provided at a position apart from the resonator hole and a conductor rod is inserted. Other,
In the part of the dielectric block in the longitudinal direction near the open surface,
There is a method in which an island-shaped input / output electrode pattern separated from the outer conductor is formed and capacitive coupling is performed with the resonant element via a dielectric.

[Problems to be Solved by the Invention] Most of the conventional input / output coupling structure is formed on the open surface side of the dielectric resonator. However, if the input and output are formed on the same surface, the following drawbacks occur. Since a capacitance is formed between the input and output and coupling occurs, a part of the input is combined with the filtered signal and appears at the output. Further, since the input / output terminals are pulled out in the same direction, the arrangement of parts is restricted.

The method of forming the input / output electrode pattern on the end surface of the dielectric block can solve the above problems by how to draw out the lead wire, but it is necessary to form an accurate electrode pattern on the end surface by screen printing, etc. The sex is bad. Further, since the input / output coupling characteristic is determined by the electrode pattern, a complicated work such as cutting the pattern is required for the later adjustment, and even if the adjustment is possible, the range is limited to an extremely narrow range.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to easily draw out the lead portion in a direction other than the open surface, to freely change the input / output coupling characteristics, and to assemble the assembly. An object of the present invention is to provide an input / output coupling structure of a dielectric filter that is easy to perform.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a groove extending from the open surface to the short-circuit surface is formed on the longitudinal end surface of the dielectric coaxial resonator. This dielectric resonator is a 1/4 wavelength type in which a plurality of resonator holes are arranged in parallel in the longitudinal direction of a dielectric block, and a conductor film is formed on the inner surface of the resonator hole and the outer surface of the dielectric block.
No conductor film is formed in the groove. Then, the electrode portion of the input / output terminal is inserted into the groove and fixed at an appropriate position.
The present invention is the input / output coupling structure of the dielectric filter configured as described above.

[Operation] The resonant element constituted by the resonator holes located at both ends of the dielectric block and the electrode portion of the input / output terminal on the end face face each other via the dielectric and are coupled with each other with capacitance. The electrode portion is movable in the groove, and when the position changes from the open surface side to the short circuit surface side, the capacitance component and the inductance component of the coupling change, and the coupling characteristics (impedance and phase) change. Therefore, by changing the insertion position of the electrode portion in the groove, the coupling position can be selected and the coupling characteristic can be adjusted.

Since the electrode portion is housed in the groove on the end face, the lead portion can be easily pulled out in the direction perpendicular to the end face through the gap between the grooves.

[Embodiment] FIG. 1 is a perspective view showing an embodiment of the present invention. The basic structure of the dielectric resonator may be the same as that of the related art except the end face structure. Two resonator holes 12 are formed at intervals in the longitudinal direction of a rectangular parallelepiped dielectric block 10 made of a sintered body of a high dielectric constant material such as barium titanate, and a connector is provided between them. A hole 14 is provided. Then, one of the surfaces where the resonator holes 12 are opened is an open surface (upper surface in FIG. 1) and the other is a short-circuit surface (lower surface in FIG. 1), and most of the outer surface of the dielectric block except the open surface is used. A conductor film is formed on the inner wall surface of the resonator hole (12). In the same figure, the shaded portion represents the surface having the conductor film, and the portion having the fine dots represents the surface having no conductor film and the base of the dielectric being exposed. The conductor film may be a very thin layer of conductive material, for example by baking a silver paste.

Now, in the present invention, in such a dielectric resonator, a groove 16 having no conductor film extending from the open surface to the short-circuit surface is formed on the end face in the longitudinal direction, and the electrode portion 20 of the input / output terminal 18 is formed in the groove 16. It is inserted and fixed to form an input / output coupling structure.

In this embodiment, the input / output terminal 18 has an electrode portion 20 that fits in the groove.
It is a punched-molded product of a metal plate in which a lead portion (22) for external connection is integrated. The lead portion 22 is bent at a right angle to the electrode portion 20 and is drawn out from the groove 16. The groove 16 has a cross-sectional shape in which the end surface side is narrow and the back side is wide. Here, it is in the shape of a "dove." The electrode part 20
Fits in the wide portion of the groove 16 and can slide within the groove along the groove.

The insertion position of the electrode part 20 becomes the coupling position, and the resonator hole
The resonance element formed by 12 and the electrode section 20 have a capacitance and are coupled to each other through a dielectric material therebetween. An appropriate bonding position is selected and fixed at that position with an adhesive or the like. This provides the desired input / output coupling characteristics.

2A to 2C show other examples of input / output terminals. If the electrode portion is provided with a spring-like protrusion as in each example, the springiness can be used to temporarily fix the groove in the groove, and the workability of assembly and adjustment is improved.

FIG. 3 shows another embodiment of the present invention. Since the basic structure of the dielectric resonator is the same as that in FIG. 1, corresponding parts are designated by the same reference numerals, and description thereof will be omitted. In this embodiment, the groove 26 has an Ω shape and the input / output terminal 28
The electrode part 30 of is also in the shape of a cylinder with slits matching it. Even with such a shape, the capacity can be obtained, so that the input and output can be coupled. The slits give it elasticity. The electrode part 30 and the lead part 32 are integrated,
The lead portion 32 can be pulled out to the open surface side or can be pulled out laterally from the gap of the bending groove 26 at a right angle.

The groove and the electrode portion are not limited to a flat plate shape or a cylindrical shape, and may have any shape such as a polygonal cylinder or a polygonal pillar as long as a predetermined capacity can be obtained.

4 to 6 show surface mounting examples of the dielectric filter according to the present invention. The dielectric resonator 40 is placed horizontally on the circuit board 42, and the strip line 44 is connected to the input / output terminal 46.
Therefore, the tip 48 of the lead portion of the input / output terminal 46 is formed so as to coincide with the substrate surface. In FIG. 6, the dielectric resonator 40 is covered with a grounding metal fitting 50 to prevent radio wave leakage from the open surface. An elongated hole 52 is formed in the upper surface of the grounding metal fitting 50, and solder is flowed to electrically and mechanically connect to the conductor film of the internal dielectric resonator. The tongue pieces 50a at the lower four corners of the earth metal fitting 50 are connected to the earth of the circuit board and fixed. In this way, surface mounting becomes possible.

7 and 8 show other input / output coupling positions.
When the electrode portion 54 of the input / output terminal 46 is close to the short-circuited surface and becomes 1/3 or less of the resonator hole length from the short-circuited surface, the capacitive coupling component and the inductance component cancel each other out to weaken the input / output coupling. In that case, it is also effective to connect the end portion of the electrode portion 54 and the short-circuited surface by soldering 56.

Next, the experimental results will be described. The dimensions of the dielectric resonator 60 used for the measurement are shown in FIGS. 9A and 9B, and the measurement jig 62 is shown in FIG. 9C.
Shown in. In the experiment, the spring pin 64 was used as the electrode part and was inserted into the groove, and the 0.25 mmφ tin-plated copper wire 66 was used for the connector part.
Connected to 68. On the input side, change the insertion position of the 4 mm pin,
The output side was inserted from the open side up to the middle of the 9mm pin.
The measurement results are shown in FIGS. In each figure, A is the position of the pin, B is the filter characteristic (the horizontal axis is 20 MHz per scale)
z) and C are Smith charts. Markers 1 to 3 are attached to the three corresponding positions in B and C. The data for each marker is shown in the table below.

In the experiment, since the length of the spring pin is longer than the height of the dielectric resonator, the phase rotation is averaged. Therefore, depending on the balance with the required capacity, it is actually desirable to use a slightly shorter electrode portion. However, this experimental result shows that the impedance of the coupling changes and the phase changes depending on the insertion position of the electrode portion.

Although all of the above embodiments have two resonator holes, it goes without saying that the present invention can be applied to the case of three or more holes.

[Effect of the Invention] As described above, according to the present invention, a groove having no conductor film extending from the open surface to the short-circuit surface is formed on the end surface of the dielectric resonator, and the electrode portion of the input / output terminal is inserted and fixed in the groove. Since the coupling is performed, the positions of the input / output terminals, the coupling impedance, and the phase can be changed even with the same resonator structure. These adjustments can be performed very easily by only shifting the position of the electrode portion in the groove. For this reason, when connecting to a stripline as a surface-mounted component, restrictions on component placement are alleviated. Further, by utilizing the groove, the lead portion of the input / output terminal can be freely pulled out in the direction perpendicular to the end face, and the coupling of the input / output which does not pass through the filter can be prevented.

Further, in the present invention, since the coupling impedance and the phase can be adjusted, when performing phase combination as a duplexer, the phase of the filter can be matched with the given wiring length without changing the line length and the strip line width. This makes it possible to manufacture an inexpensive filter without lowering the reliability of the product.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a dielectric filter according to the present invention, FIG. 2 is a perspective view showing an example of input / output terminals, and FIG. 3 is an exploded perspective view showing another embodiment of the present invention. FIG. 4 is a perspective view showing a surface mounting example of the dielectric filter of the present invention, FIG. 5 is a plan view thereof, FIG. 6 is a perspective view showing a state in which a ground metal fitting is attached, and FIG. A perspective view showing another embodiment,
FIG. 8 is a partial sectional view thereof. FIG. 9 is an explanatory view of the dielectric resonator and the measuring jig used in the experiment, FIG. 10, FIG. 11 and FIG.
FIG. 12 is an explanatory diagram showing the experimental results. 10 ... Dielectric block, 12 ... Resonator hole, 14 ... Coupler hole, 16 ... Groove, 18 ... Input / output terminal, 20 ... Electrode section, 22 ...
… Lead.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanobu Mitarai 5-36-11 Shinbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. (56) Reference JP-A-1-223802 (JP, A) JP Shown 60-165103 (JP, A) Shown 59-42607 (JP, U) Shown 57-133101 (JP, U) Shown

Claims (5)

[Claims] 1. A 1/4 wavelength type dielectric coaxial resonator is provided with a groove having no conductor film extending from an open surface to a short circuit surface on an end face in a longitudinal direction, and an electrode portion of an input / output terminal is inserted and fixed in the groove. Input-output coupling structure of dielectric filter. 2. The input / output coupling structure according to claim 1, wherein the input / output terminal is a molded product of a metal plate in which an electrode portion housed in the groove and a lead portion for external connection are integrated. 3. The input / output coupling structure according to claim 1, wherein the electrode portion is provided with a spring property and is temporarily fixed in the groove by the spring property. 4. The input / output coupling structure according to claim 1, wherein the groove has a cross-sectional shape in which the end surface side is narrow and the back side is wide. 5. The input / output coupling structure according to claim 1, wherein
An input / output coupling adjustment method for a dielectric filter, which adjusts the coupling characteristics by changing the electrode insertion position in the groove.