JPH06314901A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain the comparatively small sized and light weight dielectric filter even with a narrow pass band width by arranging planer resonance elements side by side so that end faces in the longitudinal direction are opposite to each other. CONSTITUTION:The filter is provided with two resonance elements 10 and a couple of metallic cases 21, 22. Each resonance element 10 is a tri-plate type resonance element in which a conductor electrode 14 is put between thin and long dielectric materials 11, 12 whose length is equivalent to a 1/4 wavelength with respect to the resonance frequency and only the upper and lower faces of the dielectric materials 11, 12 are covered by ground conductors 13a, 13b and the conductor electrode 14 in the middle and the upper and lower ground conductors 13a, 13b are short-circuited by a short-circuit conductor 13c provided to one end of the dielectric materials 11, 12. Then the two resonance elements 10 are supported by the metallic cases 21, 22 from the upper and lower sides and connected to ground while the short-circuit, end faces in the longitudinal direction are opposite to each other. Furthermore, a static coupling element 30 is provided in the vicinity of the open end on the side face of both the resonance elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed constant type dielectric filter used in a high frequency band such as a microwave band.

[0002]

2. Description of the Related Art The applicant of the present application has disclosed in Japanese Patent Application No. 4-220056 that a conductor electrode is sandwiched between elongated dielectrics having a length corresponding to a quarter wavelength of a resonance frequency. A plurality of quarter-wave resonator elements, each of which is covered with a ground conductor, is short-circuited with the conductor electrode in the center and the ground conductors above and below each other by a short-circuit conductor provided at one end of the dielectric, We proposed a dielectric filter in which the opposite ends, open ends, are arranged in parallel so that they are alternately arranged. As an example, FIG. 5 shows an example using two resonant elements.

In FIG. 5, two resonant elements 10 sandwich a conductor electrode 14 between elongated dielectrics 11 and 12 each having a length corresponding to a quarter wavelength of the resonance frequency. Only the upper and lower surfaces are covered with the ground conductors 13a and 13b, respectively, and the central conductor electrode 14 and the upper and lower ground conductors 13a and 13b are covered with the dielectric 1.
The short-circuit conductors 13c provided at one end of the first and the second terminals 12 are short-circuited to each other.

This type of resonance element is called a triplate type because it has a central conductor electrode 14 and three upper and lower ground conductors 13a and 13b.

The length L of the dielectric elements 11 and 12 in the resonance element 10 in the longitudinal direction is 1 / the resonance frequency.
It is set to correspond to four wavelengths. For example, in FIG.
The resonance element 10 shown in (1) has a resonance frequency of 1.5 GHz and a length L of 7 mm. The width W is 1.4m
m and the thickness T are set to 2.8 mm.

Here, for convenience, in the following description,
The end surface of the resonant element on which the short-circuit conductor 13c is formed is referred to as a short-circuit end surface, and is represented by reference numeral s in the figure, while the end surface on which the short-circuit conductor is not formed is referred to as an open end surface and is represented by reference numeral o in the figure.

The resonance elements 10 are arranged in parallel with each other on the metal case 21 with their lower surface side grounding conductors 13b in contact with the metal case 21 serving as a grounding substrate and with their open ends facing away from each other. It is arranged. In addition, the metal case 22 is the upper ground conductor 1 of the resonance element 10.
It is covered so as to be in contact with 3a. Further, the metal cases 21 and 22 are electrically connected to each other. Electrostatic coupling elements 30 are provided in the vicinity of the open ends of the side surfaces of the resonance elements 10 arranged in parallel opposite to each other. Each electrostatic coupling element 30 has a conductor 31 formed on a dielectric plate 32. Thus, the dielectric filter is constructed.

If the input terminal is connected to one of the conductors 31 of the dielectric filter constructed as described above and the output terminal is connected to the other, the vicinity of the resonance frequency of the resonance element 10 is passed between the both terminals. A band-pass filter can be configured.

FIG. 6 is an equivalent circuit diagram of this dielectric filter. Referring also to FIG. 6, the parallel circuit portion of the inductor L ₁ and the capacitor C ₁ is equivalent to the resonant element 10, and the capacitor C ₃ is equivalent to the coupling dielectric 30. The capacitor C ₂ is due to electromagnetic coupling between the two resonant elements 10. It should be noted that a resonator is formed by providing the above-mentioned one resonance element and similarly an electrostatic coupling element on its side surface. The equivalent circuit in that case is the capacitor C _{2 of} FIG. 6 and the inductor L ₁ connected to it.
It is shown by one LC parallel resonant circuit consisting of a capacitor C ₁ and a capacitor C ₁ .

Further, as the resonance element, a double plate type is known in which one conductor electrode and one earth conductor are respectively formed on the upper and lower surfaces of the dielectric, instead of the triplate type.

Such triplate-type and double-plate-type resonance elements are collectively referred to as a planar-type resonance element to distinguish them from the coaxial-type resonance element. That is, the planar resonance element is a dielectric resonance element having a conductor electrode and a ground conductor with a dielectric material sandwiched therebetween.

By the way, the pass band width of this type of dielectric filter is generally proportional to the strength of electromagnetic coupling between the resonant elements, and the same can be said for the dielectric filter shown in FIG. This will be described with reference to FIG. FIG. 7 is a diagram showing the pass band width of the dielectric filter. In the figure, the horizontal axis represents frequency and the vertical axis represents loss. In FIG. 7, the relatively wide pass band width indicated by the broken line around the center frequency f ₀ is when the electromagnetic coupling between the resonant elements 10 is relatively strong, while the relatively narrow pass band indicated by the solid line is shown. Bandwidth is when electromagnetic coupling is relatively weak.

[0013]

In the above-mentioned dielectric filter, the strength of electromagnetic coupling between adjacent resonant elements is
It has been found that while it is approximately inversely proportional to the distance, it is approximately proportional to the facing area. For example, in the dielectric filter shown in FIG. 5, the electromagnetic coupling increases in inverse proportion to the square of the distance d between the two resonant elements 10, while the dielectrics 11 and 12 which are the facing areas of the two resonant elements 10 are opposed to each other. It has been found that it increases in proportion to the product of the thickness T and the length L.

Conventionally, in this type of dielectric filter,
When the pass band width is set narrow, the juxtaposition interval is increased so as to weaken the electromagnetic coupling. For example, in FIG.
In the dielectric filter shown in FIG. 7, when the pass band shown by the solid line in FIG.
Was set to 1.5 mm. This value is a relatively large value in consideration of the size of the entire dielectric filter.

As described above, in the conventional dielectric filter, when the pass band width of the filter is set to be narrow, the arrangement interval of the planar resonant elements is increased,
There is a problem that the entire dielectric filter becomes large and heavy.

The object of the present invention is to provide a narrow pass band,
An object is to provide a dielectric filter that is relatively small and lightweight.

[0017]

According to the present invention, a plurality of planar resonant elements having a conductor electrode and a ground conductor sandwiching an elongated dielectric are arranged at intervals. In the filter, a dielectric filter is obtained, in which the adjacent planar resonance elements are arranged so that their end faces in the longitudinal direction face each other.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A dielectric filter according to an embodiment of the present invention will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 is an exploded perspective view showing a dielectric filter according to Embodiment 1 of the present invention. In FIG. 5, the same or similar parts as in the conventional example are shown in FIG.
The same reference numerals are given. In FIG. 1, this dielectric filter has two resonant elements 10 and a pair of metal cases 21 and 22. Each of the resonant elements 10 has a conductor electrode 14 sandwiched between elongated dielectrics 11 and 12 each having a length dimension corresponding to a quarter wavelength of the resonance frequency, and only the upper and lower surfaces of the dielectrics 11 and 12 are grounded by a ground conductor 13a. , 13b, and the central conductor electrode 1
4 and the upper and lower ground conductors 13a and 13b to the dielectric 11,
This is a triplate-type resonant element configured by short-circuiting each other with a short-circuiting conductor 13c provided at one end of 12.

The two resonant elements 10 are vertically supported by the metal cases 21 and 22 and are grounded with their short-circuited end faces facing each other. Electrostatic coupling elements 30 are provided in the vicinity of the open ends of the side surfaces of the vertically arranged resonant elements 10, respectively. Each electrostatic coupling element 30 has a conductor 3 on a dielectric plate 32.
1 is formed. Further, a lead wire 40 for connecting to the outside is connected to each conductor 31. Thus, the dielectric filter is constructed.

[Embodiment 2] FIG. 2 is an exploded perspective view showing a dielectric filter according to Embodiment 2 of the present invention. Note that, also in this figure, the same or similar parts as those of the conventional example are denoted by the same reference numerals as those in FIG. 5, and will not be described in detail. In FIG. 2, the present dielectric filter has two resonance elements 10 that are triplate resonance elements and a pair of metal cases 21 and 22. The resonant element 10 has a resonant frequency of 1.5 GHz, a length L of 7 mm, a width W of 1.4 mm, and a thickness T of 2.8 mm as a quarter wavelength, similarly to the conventional example shown in FIG. It is set.

The two resonant elements 10 are vertically supported by the metal cases 21 and 22 and are grounded with their open end faces facing each other. In addition, the electromagnetic coupling element 5 is provided on the inner surface of the metal case 21 so as to face the short-circuited end surfaces of the two resonance elements 10.
0 is arranged, one end of which is connected to the metal case 21, and the other end of which is a lead wire for external connection.

FIG. 4 is an equivalent circuit diagram of the present dielectric filter constructed as described above. In FIG. 4, the parallel circuit portion of the inductor L ₁ and the capacitor C ₁ is the resonance element 10
In addition, the inductor L ₃ corresponds to the electromagnetic coupling element 50 equivalently. The capacitor C ₂ is due to electromagnetic coupling between the two resonant elements 10.

Next, as a result of measuring the pass band width with respect to the distance d between the resonance elements 10 in the dielectric filter according to Example 2, a pass band width of 30 MHz was obtained when the distance d was set to 0.5 mm. From this, it can be seen that the dielectric filter according to the second embodiment can obtain the same pass band width at the interval of the resonant element of ⅓ of the dielectric filter of FIG. Further, in this embodiment, since the electromagnetic coupling by the coil is used for the input and output, the impedance increases as the frequency becomes high, and the spurious suppression effect is obtained.

In the first and second embodiments described above, the short-circuit end faces of the adjacent resonators or the open end faces of the resonators face each other. However, in the present invention, the open end face of one adjacent resonator and the other end face of the other resonator are opposed to each other. You may oppose the short-circuited end surface of a resonator.

[Embodiment 3] Embodiment 3 is an example in which the present invention is applied to a dielectric filter having a half-wavelength type planar resonant element. In the half-wavelength type planar resonant element, the length of the dielectric is set to half the resonant frequency.

FIG. 3 is an exploded perspective view showing a dielectric filter according to the third embodiment. In this figure, the same or similar parts as those in the conventional example are designated by the same reference numerals as those in FIG. In FIG. 3, the present dielectric filter has two resonant elements 110 and a pair of metal cases 21 and 22. Each of the resonant elements 110 has an elongated dielectric body 1 having a length dimension corresponding to ½ wavelength of the resonant frequency.
The conductor electrode 114 is sandwiched between 11, 112, and only the upper and lower surfaces of these dielectrics 111, 112 are grounded respectively.
It is a triplate-type resonant element which is formed by coating with 3a and 113b and whose both ends are both open end faces.

The two resonant elements 110 are placed in the metal case 21 with their short-circuited end faces facing each other.
And 22 are supported from above and below and are grounded. Electrostatic coupling elements 30 are provided in the vicinity of the open end sides of the side surfaces of the vertically arranged resonant elements 110, respectively. Each electrostatic coupling element 30 has a conductor 31 formed on a dielectric plate 32. Further, a lead wire 40 for connecting to the outside is connected to each conductor 31. Thus, the dielectric filter is constructed.

Also in the third embodiment, the distance between the two resonance elements 110 can be set to a value smaller than that in the case where the side surfaces are opposed to each other.

As described above, the present invention can be applied to a dielectric filter having a half-wavelength type planar resonant element. In addition, in the half-wavelength type planar resonant element, there are not only those in which both ends are open end surfaces but also those in which both ends are short-circuited end surfaces, but it goes without saying that the present invention can be applied to any of them. Absent. Also, open both ends and short both ends.
In the case of the dielectric filter in which the / 2 wavelength type planar resonant elements are mixed, the open end of one resonant element and the short-circuited end of the other resonant element may face each other.

[0031]

In the dielectric filter according to the present invention, a plurality of planar resonant elements arranged at intervals are arranged so that the adjacent planar resonant elements face each other in their longitudinal end faces. Therefore, the arrangement interval can be reduced, and even if the pass band width is narrow, it is relatively small and lightweight.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a dielectric filter according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a dielectric filter according to a second embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a dielectric filter according to a third embodiment of the present invention.

FIG. 4 is an equivalent circuit diagram of the dielectric filter shown in FIG.

FIG. 5 is an exploded perspective view showing a conventional dielectric filter.

6 is an equivalent circuit diagram of the dielectric filter shown in FIG.

FIG. 7 is a diagram for explaining a pass band width of a dielectric filter.

[Explanation of symbols]

 10 Resonance Element 11, 12 Dielectric 13a, 13b Earth Conductor 13c Shorting Conductor 14 Conductor Electrode 21, 22 Metal Case 30 Electrostatic Coupling Element 50 Electromagnetic Coupling Element

Front page continuation (72) Inventor Shigekazu Ishikawa 398, Komokuchi, Takatsu-ku, Kawasaki, Kanagawa, Ltd., Tokin Co., Ltd.

Claims (1)

[Claims] 1. A dielectric filter configured by arranging a plurality of planar resonance elements having a conductor electrode and an earth conductor with a long and narrow dielectric sandwiched therebetween at intervals, the planar resonance elements being adjacent to each other. Is a dielectric filter characterized in that the respective end faces in the longitudinal direction are arranged so as to face each other.