JPH0556682B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a dielectric filter having a configuration in which a plurality of adjacent dielectric resonators are coupled electromagnetically or via a coupling element, and in particular to a bandpass type filter having a pole in the attenuation region. Regarding proposals for dielectric filters. BACKGROUND OF THE INVENTION Regarding bandpass filters, orders are sometimes received from users on the condition that the amount of attenuation at frequencies a predetermined frequency away from the center frequency is greater than or equal to a predetermined value. As a means to meet such requirements, the present applicant previously proposed in Japanese Patent Application No. 60-218753 that in the above-mentioned dielectric filter, at least one dielectric resonator is skipped and the dielectric resonators existing before and after it are directly connected. We proposed a technology to connect using reactance elements. To explain with a specific example, for example, when the second stage dielectric resonator A2 and the fifth stage dielectric resonator A5 are directly coupled as shown in FIG. The columnar bodies 40, 40 made of an insulating material are inserted into the through hole 33, and the columnar bodies 40, 4
The structure is such that each end of the lead wire 41 is inserted into the hole to an appropriate depth. According to this configuration, since capacitances C1 and C2 are equivalently formed between the tip of the lead wire 41 and the inner conductor 34, the two dielectric resonators A2 and A5 are connected to the capacitance elements C1 and C2. It will be directly coupled by C2. In addition, 31 in the figure is a dielectric block;
2 is an outer conductor formed on the four outer sides of the block;
35 is a short-circuit conductor formed on the bottom surface of the dielectric block 31 to short-circuit the inner conductor 34 and the outer conductor 32, and 36 is a coupling hole for electromagnetically coupling the adjacent dielectric resonators A1, A2... be. As mentioned above, if at least one dielectric resonator is skipped and the dielectric resonators located before and after it are directly connected with a reactance element, the pole P1 in the attenuation region, as shown by the solid line in FIG. P2 occurs and the filter characteristics suddenly deteriorate. Therefore, as a result, the amount of attenuation at a predetermined frequency away from the center frequency can be set to a predetermined value or higher, thereby satisfying the user's requirements. In the figure, the broken line indicates the frequency characteristics of a filter with the same number of resonator stages and no poles. Problems to be Solved by the Invention By the way, the technology related to the above proposal, as explained in the specific example (Fig. 13), uses lead wires etc. to route the space to connect two dielectric resonators. This causes the following problems. That is, if the space is routed using lead wires or the like, the distance between the lead wire and the dielectric block is likely to change because it is susceptible to mechanical vibration. Therefore, there is a problem in that the capacitance formed between the lead wire and the dielectric block changes based on this, and as a result, the frequencies 1 and 2 that generate the poles P1 and P2 change in height. In addition, there is also the problem that many components are necessary for polarization, such as the lead wire 41 and the insulating columnar bodies 40, 40, resulting in high cost. In view of the above problems, it is an object of the present invention to provide a dielectric filter with a polar structure that is strong against mechanical vibration, has a stable frequency at which a pole is generated, and is simple in structure. . Means for Solving the Problems In order to achieve the above object, the present invention provides a dielectric filter in which a plurality of dielectric resonators configured in a dielectric block are coupled to each other electromagnetically or via a coupling element. , the protrusion of an insulating substrate having at least two protrusions on one side thereof and on which a conductive pattern is formed is inserted into a hole in which an inner conductor of a dielectric resonator is disposed, and the protrusion of the resonator is The dielectric filter is characterized in that at least two dielectric resonators are coupled by capacitance coupling between the inner conductor and the conductive pattern. The operation of the above configuration will be described in the following embodiment. Embodiment FIG. 1 shows a dielectric filter as an embodiment of the present invention. Reference numeral 1 denotes a dielectric block made of a titanium oxide ceramic dielectric, etc., and outer conductors made of metal films are provided on the four sides of the block 1. 2 are formed, and through holes 3 are formed at appropriate intervals in the dielectric block 1.
...is formed. An inner conductor 4 made of a metal film is formed on the inner surface of the through hole 3, and is short-circuited to the outer conductor 2 by a conductive film (not shown) formed on the bottom surface of the dielectric block 1. The inner conductors 4..., the outer conductors 2, and the dielectric block 1 existing therebetween create dielectric resonators A1, A2...
(hereinafter simply referred to as a resonator) is configured.
A coupling hole 6 serving as a means for coupling the resonators to each other is coupled between the resonators A1, A2..., and adjacent resonators A1, A2... are electromagnetically coupled. When the respective resonators are coupled through the coupling holes 6..., the coupling is inductive. Reference numeral 7 denotes an insulating substrate made of Bakelite or the like, which is fixed in an upright position on the upper surface 1a of the dielectric block using an adhesive or the like. This insulating substrate 7 has two protrusions 7a and 7b formed on one side thereof, and an inverted U-shaped conductive pattern 8 is formed on the surface of the substrate across these protrusions 7a and 7b. ing. Since the two convex portions 7a and 7b are inserted into the through holes 3 and 3 of the dielectric resonators A2 and A5, both the resonators A2 and A5 are connected to the inner conductors 4 and 4 and the tips 8a and 8a of the conductive pattern 8. are coupled by the capacitance formed between them. FIG. 2 shows an equivalent circuit of a dielectric filter in which two dielectric resonators A2 and A5 are directly coupled by capacitance. In the figure, X is the tip 8a of the conductive pattern,
K is the combined reactance value of the two capacitances formed between 8a and the inner conductors 4, 4 and the inductance of the conductive pattern 8 itself, and K is the value of each resonator A1, A.
This is a coupling element equivalent to the coupling hole 6 that electromagnetically couples the two.... The characteristics of the filter represented by such an equivalent circuit have poles P1 and P2 in the upper and lower attenuation regions, as shown in FIG. Poles P1, P2
The frequencies 1 and 2 at which . In general, the larger the impedance value, the more the pole will have a center frequency _{of 0.}
There is a tendency to move away from The impedance value is determined by the length of the conductive pattern, that is, the conductive pattern tip 8a,
This can be changed by varying the length of the penetration of the 8b into the through hole 3. Note that if the impedance value of X is too small, the pole will enter the passband, which is not preferable. The poles can be placed above or below depending on the number of resonators to be blown by connecting reactance X, the type of reactance element (capacitive or inductive) and the type of coupling element (capacitive or inductive). It can be selectively formed in one or both of the attenuation regions. The table below lists some representative examples.

[Table] FIG. 3 shows another embodiment of the present invention. In this embodiment, the conductive pattern 8 includes a plurality of branch portions 8c,
8d, and both ends 8a, 8b of the conductive pattern and each branch part 8c, 8d are connected to the dielectric resonator A of each stage.
2, A3, A4, and A5. According to this configuration, the dielectric resonators A2 to A5 in each stage can be multi-coupled, and by selecting each coupling, upper or lower Only the poles of can be moved. FIGS. 4 to 12 each show other embodiments of the present invention. 4 and 5 show an example in which the insulating substrate 7 is extended and an external coupling capacitor Ce is formed in the extended portion 7l. That is, in FIG. 4, an external coupling capacitor is formed by electrodes 9a and 9b formed opposite to each other on both sides of the extension portion 7l of the insulating substrate.
On the other hand, in FIG. 5, a chip capacitor 10 forms an external coupling capacitor Ce. In FIG. 4, one electrode 9a extends from the upper end of the inner conductor 4 to form a dielectric block upper surface 1a.
It is connected by solder to the extraction electrode 11 formed in the. Due to this solder connection structure, the insulating substrate 7
It also serves as fixation to the dielectric block 1. still,
Although not shown, the external coupling capacitor Ce can also be formed by two comb-shaped electrodes. In that case, it is advantageous in terms of manufacturing because it is only necessary to form the electrode on one main surface of the insulating substrate 7. FIG. 6 shows an example in which comb-shaped electrode portions 12 and 13 are formed in the center portion of the conductive pattern 8. As shown in FIG. Since the comb-shaped electrode parts 12 and 13 have capacitance,
As shown in FIG. 7, the two dielectric resonators have the capacitance Ci and the capacitance C formed between the conductive pattern tips 8a and 8b and the inner conductor of the dielectric resonators.
1 and C2 are coupled by a series composite capacitance. By cutting the comb-shaped electrode portions 12 and 13, the capacitance Ci changes and the strength of the coupling between the two resonators changes, so that the position of the pole generated in the filter characteristics can be varied. FIG. 8 shows the comb-shaped electrode section 1 in the above embodiment.
2 and 13, the capacitance Ci is formed at the opposing portions of the conductive patterns 14 and 15 formed on both sides of the insulating substrate 7.
An example of forming a . In this embodiment as well, the capacitance Ci can be adjusted by cutting one of the conductive patterns. FIG. 9 shows an example in which an inductance L is equivalently formed as shown in FIG. 10 by forming a plurality of thin linear patterns 16a, 16b, . . . in the central portion of the conductive pattern 8. According to this embodiment, the two dielectric resonators are coupled by a reactance that is a combination of the inductance L and capacitances C1 and C2. The impedance value is smaller compared to the case of composite reactance with only capacitance,
Therefore, the position of the upper pole of the filter characteristic approaches the center frequency. The value of the inductance L can be varied by removing one or more of the thin linear patterns 16a, 16b.... FIG. 11 shows an example in which, unlike the embodiment shown in FIG. 9, the central part of the conductive pattern 8 is formed thick and the inductance L is varied by cutting the width of this part. FIG. 12 shows a modification of the embodiment shown in FIG. 5, in which one electrode 17 to which the chip capacitor 10 is connected and the part of the insulating substrate 7 on which it is formed are cut, and an external coupling pin 18 is inserted into this part. An example in which one end is fixed with solder or the like is shown. A hermetic stem 20 is provided at the portion where the external coupling pin 18 passes through the case 19 covering the dielectric block 1. In the above embodiments, adjacent dielectric resonators are coupled by coupling holes, but it goes without saying that they can be coupled by other coupling elements such as coupling capacitors and coils. Effects of the Invention As explained above, the dielectric filter of the present invention has at least two convex portions on one side thereof, and the convex portion of the insulating substrate on which the conductive pattern is formed is located inside the dielectric resonator. At least two dielectric resonators are coupled by being inserted into a hole in which a conductor is arranged, and the inner conductor of the resonator and the conductive pattern are capacitively coupled. Similar to the dielectric filter previously proposed in Japanese Patent Application No. 60-218753, it is possible to generate a pole in the attenuation region and obtain a filter with the desired bandwidth and steep rise characteristics. In addition, it is very resistant to mechanical vibrations and therefore at least 2
This has the advantage that the reactance value for coupling the two dielectric resonators is stable, and there is no possibility that the frequency at which a pole is generated will fluctuate due to mechanical vibration. Furthermore, the present invention also has the following effects. That is, in the present invention, at least two
Since two protrusions are formed and a conductive pattern is formed on this insulating substrate, by inserting the protrusions into the hole in which the inner conductor of the dielectric resonator is arranged, it is possible to easily connect the inner conductor of the resonator with static electricity. In addition to being able to perform capacitive coupling, the insulating substrate can be positioned at a predetermined position on the dielectric body by the simple operation of inserting the convex portion into the hole of the dielectric resonator. At the same time, since the convex portion serves to temporarily fix the insulating substrate to the dielectric block during the manufacture of the dielectric filter, it is possible to further improve assembly workability. Furthermore, in the present invention, by varying the length of the coil pattern formed on the convex portion of the insulating substrate,
Since the capacitance of electrostatic coupling with the conductor inside the resonator can be changed, there is also the effect that the frequency characteristics can be easily adjusted.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a dielectric filter as an embodiment of the present invention, Fig. 2 is an equivalent circuit diagram thereof, Fig. 3 is a diagram showing another embodiment of the invention, Figs.
Fig. 6, Fig. 8, Fig. 9, Fig. 11, Fig. 12
Figures 7 and 7 show still other embodiments of the present invention, respectively.
6 is an equivalent circuit diagram of FIG. 6, FIG. 10 is an equivalent circuit diagram of FIG. 9, FIG. 13 is a sectional view showing a conventional dielectric filter, and FIG. 14 is a diagram showing filter characteristics. 1... Dielectric block, 7... Insulating substrate, 8...
...Dielectric pattern.

Claims (1)

[Scope of Claims] 1. A dielectric filter in which a plurality of dielectric resonators configured in a dielectric block are coupled to each other electromagnetically or via a coupling element, and at least two convex portions are provided on one side of the filter. and the convex portion of the insulating substrate on which a conductive pattern is formed is inserted into a hole in which an inner conductor of a dielectric resonator is arranged, and the inner conductor of the resonator and the conductive pattern have a capacitance. A dielectric filter characterized in that at least two dielectric resonators are coupled by being coupled.