JPH0531303U - Dielectric filter - Google Patents

Abstract

(57) [Abstract] [Purpose] The size of the filter is reduced and the block is cracked by using the increase and decrease of the frequency change rate and the change of the bandwidth depending on the position of the coupling groove formed on the bonding surface of the dielectric block. To provide a dielectric filter that is hard to do. A coupling groove 5 is formed in each of the dielectric resonators 1a and 1b in a direction orthogonal to the through hole 2 to form a plurality of dielectric resonators 1a and 1b.
In the dielectric filter in which the coupling groove 5 of b is abutted so as to face each other, the coupling groove 5 has the center thereof at the dielectric resonator 1
It was formed so as to be located closer to the short-circuit end face side than the center in the length direction of the joint surface of a and 1b.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a dielectric filter used for a microwave band filter, and more particularly to a structure for increasing the coupling degree between adjacent resonators.

[0002]

[Prior art]

 2. Description of the Related Art Conventionally, dielectric filters are often used in devices such as personal radios and car phones that utilize microwaves because of their small size and high selectivity.

In a conventional dielectric filter, a single dielectric block is used to form a plurality of through holes on its upper surface (open end surface) and bottom surface (short circuit end surface), and further on the inner surface of the through hole. The conductive film (hereinafter referred to as the inner conductor) is formed on the outer peripheral surface of the single dielectric block except the open end surface, respectively. Furthermore, a groove having a predetermined depth from the open end face (hereinafter referred to as a coupling groove) is formed in each through hole. As a result, the portion partitioned by the coupling groove acts as a resonator around the through hole, and each resonator is coupled through the coupling groove.

However, in a dielectric filter in which a resonator is formed in a block of a single dielectric as described above, it is necessary to change the number of resonators according to frequency characteristics, and according to each characteristic. , I had to prepare many types of dielectric blocks.

Therefore, the present applicant previously proposed a dielectric filter in which a resonator is formed in advance and the resonator to be coupled can be freely set according to the frequency characteristic.

In the structure, a dielectric block corresponding to one resonator is formed, and a coupling groove having a predetermined size is formed on a side surface (hereinafter, referred to as a joint surface) where two resonators come into contact with each other according to a filter characteristic. They were formed, and their joint surfaces were brought into contact with each other to be connected.

FIG. 5 shows a specific structure of the dielectric filter 50 in which two resonators are in contact with each other. In one resonator 51a, a through hole 52 is formed in a single block body obtained by press molding and firing a dielectric ceramic material, and an inner conductor 53 and the through hole are formed on the inner surface of the through hole 52. The outer conductor 54 was formed on the outer peripheral surface of the dielectric block except for one exposed open end surface. In addition, the coupling groove 55 having a predetermined size is formed on the junction end face of the dielectric resonator 51b in the direction directly intersecting with the through hole 52. As a result, when the two resonators 51a and 51b come into contact with each other, the two coupling grooves 55 are brought together to form the coupling hole 56 in a direction directly intersecting with the through hole 52.

The degree of coupling is determined by the width and depth in the length direction of the coupling groove 55 having the above-described structure, that is, the depth in the through hole 2 direction from the joint surface.

[0009]

[Problems of conventional technology]

 However, no consideration is given to the formation position of the coupling groove 55 of the above-mentioned resonator junction type dielectric filter, and the center in the longitudinal direction of the joint surface and the center of the width in the longitudinal direction of the coupling groove 55 are not considered. It was formed to match.

If the width of the coupling groove 55 is adjusted and the coupling groove 55 is enlarged in accordance with the characteristics of such a dielectric filter, the center frequency rises. It was necessary to increase the height. Therefore, there is a problem that the size of the entire dielectric filter is slightly increased.

Further, in order to obtain a wide band (large coupling degree) filter characteristic, it is necessary to widen the width of the coupling groove 55 in the length direction. This shifts the capacitive coupling and the inductive coupling between the two resonators, whereby the even-mode resonant frequency and the odd-mode resonant frequency are deviated, and a filter with a wide pass band is achieved. In this case, since the width of the coupling groove 55 with respect to the joint surface is widened, there is a problem that the strength of the dielectric block is reduced and the possibility of cracks in the block body increases.

The object of the present invention was devised in view of the above-mentioned problems, and the increase / decrease in the rate of frequency change and the change in bandwidth depending on the position of the coupling groove formed on the junction surface of the dielectric block. The purpose of this is to provide a dielectric filter in which the size of the filter is reduced and the block is less likely to crack.

[0013]

[Concrete means for solving the problem]

 In order to achieve the above-mentioned object of the present invention, the present invention provides a through hole penetrating from the top surface to the bottom surface of the dielectric block, and the inner surface of the through hole has an inner conductor and an outer peripheral surface excluding the top surface of the dielectric block. A dielectric filter in which a conductor is provided and a coupling groove is formed in a joint surface where two dielectric blocks contact each other in a direction orthogonal to the through hole, and the joint surfaces of a plurality of dielectric blocks are in contact with each other, The coupling groove was formed such that its center was located closer to the bottom surface side than the center in the length direction of the contact surface of the dielectric block.

[0014]

[Action]

 As described above, the center of the width in the longitudinal direction of the coupling groove formed on the joint surface of the two resonators is closer to the short-circuit end face side, which is the bottom surface of the resonator, than the center of the longitudinal direction of the joint surface of the resonator. The resonance frequency is reduced by forming the resonator in the length direction, and in order to set the resonance frequency to a predetermined value, it is sufficient to lower the length direction of the resonator. Therefore, miniaturization of the dielectric filter can be achieved. Become.

Further, since the pass band width of the filter is increased, it is not necessary to increase the width in the length direction of the coupling groove as in the conventional case, and a simple and robust wide band dielectric filter can be achieved. Will be.

In a filter having a center frequency of a predetermined value and a pass band of a predetermined value, the center of the width in the length direction of the coupling groove is closer to the bottom surface of the resonator than the center of the joint surface of the resonator in the length direction. By forming it on the side of a certain short-circuited end face, the degree of coupling increases and becomes wider than the predetermined pass band. The width of the coupling groove may be reduced to obtain a pass band having a predetermined value.

At that time, if the width of the coupling groove is reduced, the center frequency becomes smaller than a predetermined value. For this reason, the length of the resonator (the straight direction of the through hole) may be reduced in order to obtain a predetermined value.

This makes it possible to achieve a small-sized dielectric filter in which the length direction of the resonator is shortened. Also, the degree of coupling can be easily increased, and a wide band dielectric filter can be achieved.

In the above operation, the reason why the pass band width of the filter is increased is that the two resonators are electromagnetically coupled by capacitive coupling and inductive coupling. The capacitive coupling largely acts on the open end face side of the resonator, and the inductive coupling largely acts on the short-circuited end face side of the resonator. Therefore, in order to increase the degree of coupling, it is necessary to increase the difference between capacitive coupling and inductive coupling at the position where the coupling groove is formed.

By forming the coupling groove on the side close to the short-circuited end face, inductive coupling does not change, but capacitive coupling is further weakened because the dielectric block is cut off by the coupling groove, resulting in inductive coupling. The difference between the capacitive coupling and the capacitive coupling becomes large, and electromagnetic coupling with a high degree of coupling is achieved. That is, a wide band dielectric filter having a high degree of coupling can be obtained without increasing the width of the coupling groove.

[0021]

【Example】

 Hereinafter, the dielectric filter of the present invention will be described in detail with reference to the drawings. FIG. 1 is an external perspective view of a dielectric filter of the present invention, and FIG. 2 is a sectional view showing a state where two resonators are in contact with each other.

The dielectric filter 10 of the present invention is constructed by abutting two dielectric resonators 1a and 1b.

The dielectric resonator, for example 1a, has a through hole 2 penetrating from the upper surface (open end surface) to the bottom surface (short circuit end surface) of the dielectric block body 1, and the inner conductor is formed on the inner surface of the through hole 2. 3 is formed. An outer conductor 4 is formed on the outer peripheral surface of the dielectric block body 1 excluding the open end surface. Further, a coupling hole 6 is formed in a joint surface where the two dielectric resonators 1a and 1b abut each other in a direction orthogonal to the through hole 2. In one induction body resonator 1a, a coupling groove 5 forming a coupling hole 6 is formed on the surface of the dielectric resonator 1b which is joined to the dielectric resonator 1b.

The dielectric block body 1 includes a BaO—TiO ₂ system, a ZrO ₂ —SnO ₂ —TiO ₂ system, a BaO—Sm ₂ O ₃ —TiO ₂ system, a BaO—Nd ₂ O ₃ —TiO ₂ system, or a CaO— system. It is made of TiO ₂ —SiO ₂ system ceramic with a predetermined dielectric constant, and is set to a predetermined length h according to the resonance frequency. The dielectric block body 1 is formed by press-molding the above-mentioned materials and further firing. Through-holes 2 are formed during this press-molding, and if necessary, coupling grooves 5 are formed by post-processing.

An inner conductor 3 made of silver, copper or the like is formed on the inner surface of the through hole 2 of the dielectric block body 1, and the outer surface of the dielectric block body 1 excluding the open end surface where the opening of the through hole 2 appears. Is formed with an outer conductor 4 such as silver or copper. The outer conductor 4 is also formed on the short end face of the block body 1 facing the open end face so as to be electrically connected to the inner conductor 3.

The inner conductor 3 and the outer conductor 4 described above are formed by depositing silver, copper, or the like by a method such as printing, coating, or transferring, and firing.

As a result, the dielectric resonator 1 is determined by the capacitance component of the dielectric portion sandwiched between the inner conductor 3 and the outer conductor 4 and the length of the current path between the inner conductor 3 and the outer conductor 4. The inductive component constitutes the LC resonance circuit.

In the dielectric filter, the two resonators 1a and 1b having the above-described structure are bonded to each other at their bonding surfaces via solder or a conductive adhesive, and in a pressure contact state. The two resonators 1a and 1b are electromagnetically coupled through the coupling hole 6 formed by the coupling groove 5 formed on the joint surface, and a dielectric filter having a predetermined pass band width and a predetermined center frequency is formed. To be achieved.

According to the present invention, the coupling groove 5 is formed such that the center of the width w in the longitudinal direction of the dielectric resonator 1 is shorter than the center of the length h of the joint surface of the two resonators 1a and 1b. It is formed by displacing to the side. For example, when the height h of the joint surface of the resonators 1a and 1b is set to 9 mm and the width w of the coupling groove 5 is set to 3 mm, the center point of the joint surface in the longitudinal direction is from the open end side. It becomes 4.5 mm, and the center of the width w of the coupling groove 5 in the length direction of the dielectric resonator 1 is set to 4.5 mm or more from the open end face side.

In this way, the center of the width w of the coupling groove 5 formed on the joint surface of the two resonators 1a and 1b is set closer to the resonator 1a than the center of the height of the joint surface of the resonators 1a and 1b. By forming it on the short-circuited end face side of 1b, the resonance frequency is reduced and the pass band width of the filter is increased.

The height of the resonator can be reduced, and a small dielectric filter can be achieved as compared with a dielectric filter having the same characteristics.

The coupling between the two resonators 1a and 1b is electromagnetically coupled by capacitive coupling and inductive coupling. The capacitive coupling largely acts on the electromagnetic field coupling on the open end face side of the resonators 1a and 1b, and the inductive coupling largely acts on the electromagnetic field coupling on the short circuit end face side of the resonators 1a and 1b. If the difference between the capacitive coupling and the inductive coupling at the position where the coupling hole 6 of the resonators 1a and 1b is formed is large, a dielectric filter having a large coupling degree, that is, a wide band can be realized. To form a broadband filter, the degree of inductive coupling should be further increased and / or the degree of capacitive coupling should be reduced. In the present invention, when the coupling hole 6 is formed on the short-circuited end face side, a part of the dielectric block body 1 is cut out at the same time, so that the capacitance component of that part is reduced. That is, by forming the coupling hole 6 on the short-circuited end face side, the degree of inductive coupling does not substantially change, but the degree of capacitive coupling is further reduced, and as a result, a broadband dielectric filter can be easily achieved. become.

On the contrary, to describe the open end face side, capacitive coupling greatly affects the electromagnetic field coupling on the open end face side. At this time, if the coupling hole 6 is formed on the open end face side, a part of the dielectric block body 1 is cut out, and the capacitance component of that part is reduced, which acts to weaken the degree of capacitive coupling. .. That is, the difference between the degree of capacitive coupling and the degree of inductive coupling tends to decrease, and as a result, the degree of coupling in the coupling hole 6 decreases, so that a broadband dielectric filter cannot be achieved.

The inventors measured the state of frequency change, the pass band width, and the center frequency at the formation position of the coupling hole 6, respectively.

As the dielectric filter used for the measurement, the width w of the coupling groove 5 formed on the bonding surface was set to 3 mm, which was in contact with the entire bonding surface of the two resonators having the length h9 mm. Sample 1 has the upper end of the coupling groove 5 2 mm from the open end face side (the displacement between the center of the joint surface and the center of the coupling hole is 1 mm on the open end face side), and for sample 2, the upper end of the joint groove 5 is the open end face side. From 3 mm (the center of the joint surface and the center of the joint hole are coincident), the sample 3 has the upper end of the joint groove 5 4 mm from the open end surface side (displacement between the center of the joint surface and the center of the joint hole on the short-circuit end surface side). The sample 4 has the upper end of the coupling groove 5 formed 5 mm from the open end face side (the displacement between the center of the joint surface and the center of the joint hole is 2 mm on the short-circuited end face side).

The even-mode resonance frequency, odd-mode resonance frequency, center frequency, and pass band width of these filters were measured and calculated. The results are shown in Table 1, FIG. 3 shows the relationship between the formation position of the coupling groove 5 and the resonance frequency, and FIG. 4 shows the relationship between the formation position of the coupling groove 5 and the degree of coupling.

[0037]

[Table 1]

As is clear from Table 1 above, when the center of the coupling groove 5 is formed closer to the short-circuit end face side than the center of the width in the longitudinal direction of the joint surface, the center frequency is decreased and the bandwidth is increased (coupling Can be understood).

Here, considering miniaturization in a dielectric filter having a center frequency of 901 MHz and a bandwidth of 26 MHz, when the center of the coupling groove is displaced 1 mm from the center of the joint surface to the short-circuit end face side, the passage The bandwidth increases to 50 MHz and the center frequency decreases to 897 MHz. In order to make the pass band width 26 MHz, the width of the coupling groove 5 may be 3 mm to 2.5 mm. Further, in order to increase the center frequency from 897 MHz to 901 MHz, the length direction of the resonator may be reduced from 9 mm to 8.95 mm.

Therefore, when obtaining filters having the same characteristics, the width of the coupling groove can be reduced and the size of the entire resonator can be reduced, so that a small dielectric filter can be achieved.

Further, considering the pass band, by displacing the center of the coupling groove from the center of the joint surface to the short-circuit end face side, a wide band dielectric filter with a high degree of coupling can be easily achieved, and the pass band width can be increased. Since the center frequency is corrected at the same time by reducing the center frequency, a small dielectric filter can be achieved.

As a result, a wide band dielectric filter having a large degree of coupling can be obtained by keeping the width of the coupling groove constant. Conventionally, the band width of the coupling groove is simply widened to obtain a wide band dielectric filter. However, the width of the coupling groove can be substantially reduced, and the strength of the dielectric block is increased.

In particular, in the present invention, since the filter is formed by abutting a plurality of resonators, the coupling groove forming the coupling hole can be easily manufactured.

In the above-mentioned embodiment, the dielectric filter is composed of two resonators 1a and 1b, but three or more resonators may be joined to form a filter. Resonators having different heights may be used. In addition, it can be widely used for polarized dielectric filters and dielectric filters for antennas.

[0045]

【effect】

 As described above, according to the present invention, the height of the joint surface in the length direction of the dielectric filter can be reduced, and a miniaturized dielectric filter can be achieved.

Further, it is possible to easily achieve a wide band dielectric filter in which the strength of the dielectric block is improved.

[Brief description of drawings]

FIG. 1 is an external perspective view of a dielectric filter of the present invention.

FIG. 2 is a cross-sectional view of the dielectric filter of the present invention before two resonators are brought into contact with each other.

FIG. 3 is a characteristic diagram showing a relationship between a formation position of a coupling groove and a resonance frequency.

FIG. 4 is a characteristic diagram showing the relationship between the formation position of a coupling groove and the degree of coupling.

FIG. 5 is an external perspective view of a conventional dielectric filter.

[Explanation of symbols]

 10, 50 ... Dielectric filter 1a, 1b, 51a, 51b Dielectric resonator 2, 52 ... Through hole 3, 53 Inner conductor 4, 54 ... Outer conductor 5 ... Connection groove 6 ... Connection hole

Claims (1)

[Scope of utility model registration request] 1. A through hole penetrating from a top surface to a bottom surface of a dielectric block is provided, and an inner conductor is provided on an inner surface of the through hole.
An outer conductor is provided on the outer peripheral surface excluding the upper surface of the dielectric block, and a coupling groove is formed on the outer peripheral surface in a direction orthogonal to the through hole. In the body filter, the coupling groove is formed such that the center of the coupling groove is located closer to the bottom surface side than the center in the length direction of the joint surface of the dielectric block.