JPH06260808A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain a dielectric filter of a small type with low insertion loss and high attenuation quantity by forming a coupling circuit by providing plural sheets of electrode film and slits on both planes of a dielectric substrate, joining them with plural dielectric resonators, and forming an impedance matching element and an attenuation electrode. CONSTITUTION:The dielectric resonators 1a, lb of parallelopiped consisting of dielectric ceramics and provided with a through hole 2a in the center, and the tip of an element 6 fitted in the inside of the through hole 2a are connected to a coupling circuit substrate 3. The coupling circuit substrate 3 is formed by providing the plural sheets of electrode film 4 on both planes of the dielectric substrate 3 and the slits S between the electrode film 4, and they form the impedance matching element and the attenuation electrode, and electrodes 4c, 4e at both terminals on an input/output terminal 5 side form the input/output terminals by soldering with a set substrate. The periphery of the filter is covered with a case 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter suitable for application to a high frequency filter for radio equipment such as a mobile phone.

[0002]

2. Description of the Related Art A high-frequency filter used in a wireless device such as a mobile phone is required to have the same performance and a smaller volume as various other parts are miniaturized.

There are three types of high frequency filters used in these devices: a SAW filter (surface acoustic wave filter), a dielectric laminated LC filter, and a filter using a dielectric resonator, depending on the frequency band used. Among these, the two types have the advantage that they are small and can be easily mounted on the surface, but they are unsatisfactory because there are limits to the insertion loss and attenuation that are important characteristics of the filter.

On the other hand, the dielectric resonance filter has the advantages of low insertion loss and high attenuation. Further, since the low insertion loss of the filter leads to the miniaturization of the battery mounted in the radio device, that is, the miniaturization of the set, the size of the dielectric resonance filter itself is large compared to the two types of filters due to its structure. However, it is often used as a filter for wireless devices.

As shown in FIG. 12, the dielectric resonance filter has a through hole 32a at the center of a rectangular parallelepiped dielectric ceramic, and electrodes 32b are provided on all surfaces except one surface facing the through hole 32a. This center through hole 32a is provided.
In order to couple the plurality of rectangular parallelepiped dielectric resonators 31a and 31b in which the terminal 36 of the resonator is inserted to the stages of the dielectric substrate 33a and the plurality of dielectric resonators 31a and 31b, the substrate 3
3a, a coupling circuit board 33 having electrodes 34 for forming capacitance and inductance, and this coupling board 33.
It is composed of an input / output terminal 35 attached to, a metal case upper surface 37a and a lower surface 37b which cover the dielectric filter.

Here, in order to miniaturize the dielectric filter, the dielectric resonator 31a occupying 1/2 to 2/3 of its volume,
The miniaturization of 31b and the miniaturization of the coupling circuit board 33 can be considered. Since the length of the resonator is uniquely determined by the resonance frequency and the relative permittivity of the dielectric material, a material having a high permittivity may be used, but at present, a material having a high Q and a good temperature coefficient of the resonance frequency is available. The relative permittivity is around 100, which is the highest, and has not been dramatically reduced in size.

Therefore, the realization of a filter with a smaller insertion loss is relatively relevant to the purpose of downsizing the dielectric filter. For this purpose, it is necessary to widen the bandwidth of the pass band, but on the other hand, a filter having a wide bandwidth cannot provide sufficient attenuation. Therefore, in general, one dielectric resonator is added as a band elimination filter to form an attenuation pole. However, if such measures are taken, it is against the purpose of downsizing the dielectric filter. Therefore, a method of forming an attenuation pole without using a dielectric resonator is used.

13 to 15 show coupling circuit boards 33, 43 and 53 for a bandpass filter using a dielectric resonator.
Indicates. FIG. 13 shows a comb-shaped electrode 34 on a dielectric substrate 33a.
By forming the, the capacity can be finely adjusted. FIG. 14 shows a combined circuit board 43 formed by mounting a chip capacitor 44 on a glass epoxy printed board 43a.
The characteristics can be finely adjusted. Further, FIG. 15 shows a dielectric substrate 53.
The coupling circuit board 53 is shown in which electrodes 54 are provided on both sides of a to form a necessary capacitance, and it is used by taking advantage of the fact that a large capacitance can be formed.

[0009]

However, the comb-shaped electrode 34 requires a relatively large substrate area and is not suitable for a small filter. When the chip capacitor 44 is used,
In order to obtain a capacitance of 0.5 pF or less, a number of chip capacitors are used in series, which makes it difficult to reduce the size and increases the number of parts and the number of assembly steps. When the electrodes 54 are formed on both sides of the dielectric substrate 53a, it is difficult to control a small capacitance.

In view of the above points, the present invention has an object to realize a filter having a low insertion loss and a high attenuation amount and a small size.

[0011]

As shown in FIGS. 1 to 7, a dielectric filter of the present invention includes a plurality of dielectric resonators 1a and 1b and a plurality of dielectric resonators 1a and 1b.
In a dielectric filter having a coupling circuit board 3 formed of a dielectric substrate 3a provided with an input / output terminal 5 while capacitively coupling b, those provided adjacent to each other on the same main surface of the coupling circuit board 3 First and second electrode patterns 4a and 4b to which the terminals 6 of the dielectric resonators 1a and 1b are connected, and the first and second electrode patterns 4a and 4
All of b are arranged so as to be opposed to each other with the coupling circuit board 3 interposed therebetween, and the third electrode pattern 4d and the third electrode pattern 4d which are separated from each other via the slit portions S ₂ and S ₃ . , And fourth electrode patterns 4c and 4e connected to the input / output terminal 5.

Further, according to the present invention, in the above-mentioned dielectric filter, the fourth electrode patterns 4c and 4e are formed into bent and / or curved shapes 4h and 4k, and the fourth electrode patterns 4h and 4k are formed into the same shape. There are portions 4f 'and 4g' having no electrode pattern on the opposing surface of the coupling circuit board 3.

[0013]

According to the dielectric filter of the present invention, a plurality of dielectric resonators 1a and 1b and a predetermined number of dielectric resonators 1a and 1b formed on both sides of the dielectric substrate 3a connected to the terminals 6 of the dielectric resonators 1a and 1b are provided. Patterned electrode film 4 and further slits S ₁ , S
A small high-frequency filter with an attenuation pole, a low insertion loss, and a high attenuation amount can be obtained by using only one coupling circuit board 3 having a minute capacitance formed by ₂ and S ₃ . Further, since the coupling circuit board 3 is formed without waste, the surface mounting can be performed as it is, the input / output terminals can be omitted, and the size can be further reduced.

Further, according to the dielectric filter of the present invention, bent and / or curved electrode patterns are provided at both ends of the same surface of the dielectric substrate 3a, and these electrode patterns are provided on opposite surfaces of the dielectric substrate 3a. An electrode film formed so as to have a portion having no electrode pattern, and a coupling circuit board formed by further forming a minute capacitance by the slits S ₁ , S ₂ and S ₃ form an attenuation pole on the high frequency side of the pass band, Further slit S ₂
And by adjusting the S _3, so as to be formed at the position of the second harmonic of the pass band attenuation pole, it is also possible miniaturization and harmonic characteristic improvement.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the dielectric filter of the present invention will be described in detail below with reference to FIGS.

In FIG. 1, reference numerals 1a and 1b denote dielectric resonators each having a rectangular parallelepiped (cylinder or hexagonal column) columnar shape using a dielectric ceramic material such as barium titanate, magnesium titanate, or calcium titanate. A through hole 2a is formed at the center of one surface, and electrodes other than the one surface facing the through hole 2a are provided with electrodes made by baking silver or electroless plating of copper. Terminal 6
The cylindrical portion 6a is the through hole 2 of the dielectric resonators 1a and 1b.
The tip tongue 6b is inserted into the inside of a, and the tip tongue 6b is projected from the through hole 2a.

In the coupled circuit board 3, electrode films 4 are formed on both surfaces of a dielectric substrate 3a having a relative permittivity of about several tens. These electrode films 4 are usually formed with a predetermined electrode pattern by screen printing, photolithography, or the like. The electrode patterns 4a and 4b are formed on one surface of the electrode film 4, and the electrode pattern is formed on the other surface, that is, the surface on the input / output terminal side. 4c, 4d and 4e are formed.

A slit S ₁ is provided between the electrode patterns 4a and 4b, a slit S ₂ is provided between the electrode patterns 4c and 4d on the other surface, and a slit S ₃ is provided between the electrode patterns 4d and 4e. These slits S ₁ , S ₂ and S ₃ have small gaps and have respective capacities.

The above components are assembled inside the case 7, which is made of phosphor bronze or the like and has a plate thickness of 0.1.
The size is about 100 mm, and the overall size is 100 mm ³ or less. The rear part is covered with the upper surface and the side surface, but the front surface is provided with the front plate 7a at the center, but the left and right corners are the upper surface. It is open including.

FIG. 1B shows an assembled perspective view. In the coupled circuit board 3, the electrode patterns 4a and 4b are the dielectric resonator 1.
The dielectric resonator 1 is disposed so as to face and closely face a and 1b.
tongue 6b of terminal 6 inserted in through hole 2a of a and 1b
Are connected. Electrode pattern 4 on one input / output terminal 5 side
d is covered with the case 7 so as to keep a gap from the case front plate 7a. Here, although the electrode patterns 4c and 4e are exposed from the case 7, they are directly soldered to a set substrate such as a mobile phone to which the present dielectric filter is attached so as to also serve as the input / output terminal 5. A dielectric filter having a compact and efficient coupling circuit board 3 having no wasteful parts is formed.

The operation of the dielectric filter of this example having the above structure will be described below. 2 is a configuration diagram and a cross-sectional view of the dielectric resonator side and the input / output terminal side of the coupling circuit board 3, and FIG. 3 is an equivalent circuit diagram of the coupling circuit board 3 forming an attenuation pole on the low frequency side of the pass band. Indicates.

Shaped by the electrode patterns 4a and 4c of FIG.
The capacity created is C in Figure 3.₁Equivalent to. Similarly, the electrode pattern
The capacitance due to turns 4a and 4d is C₂And electrode pattern
The capacitance due to pins 4b and 4d is C₃, And electrode pattern
The capacity due to 4b and 4e is C _FourEquivalent to. Where C₁
And C_FourIs between the dielectric resonators 1a and 1b and the input / output terminal 5.
It is a capacitance for impedance matching.

Further, the slit S ₂ provided on the dielectric substrate 3a
The capacity due to S ₁ corresponds to C ₅ , the capacity due to the slit S ₃ corresponds to C ₆ , and the capacity due to S ₁ is ₂ in parallel with C ₂ and C _3.
It exists between the two dielectric resonators 1a and 1b (not shown). Since C ₅ and C ₆ have smaller capacities than C _{1 to} C ₄ , they form attenuation poles without increasing insertion loss. The electrode pattern on the dielectric substrate 3a is usually formed by screen printing or photolithography. By these methods, the capacitance values of C ₅ and C ₆ are determined by the original plate and cannot be adjusted, but a groove is formed between 4c, 4d and 4e, and the capacitance values of C ₅ and C ₆ are finely adjusted by the depth. It will be possible.

FIG. 4 shows the filter characteristics, but the dielectric circuit coupling circuit board 3 having the filter characteristics shown in FIG. 4A.
Capacitors C ₅ and C ₆ are formed at the low frequency side to provide an attenuation pole on the low frequency side of the pass band to obtain the filter characteristic shown in 4B.

Another embodiment of the present invention will be described with reference to FIGS. The above-mentioned embodiment refers to the electrode film 4 of the coupling circuit board 3.
The configuration is the same except that the configuration pattern of is changed.

Electrode films 4 are provided on both sides of the dielectric substrate 3a, and a special pattern is partially formed by screen printing or the like. As shown in FIG. 5, the dielectric resonators 1a, 1
Compared with 4a and 4b described above, the electrode film on the b side only has a part of the upper part left and right sides left, and 4f 'and 4g' parts are removed, and the area becomes about half less than 4f and 4g. . Through holes 4l and 4m reaching the opposite surface are provided at both ends of the left and right upper electrode strips.

Electrode patterns 4h, 4j, and 4k are provided on the opposite surface, that is, the input / output terminal 5 side. Here, the central portion 4j is the same as the above-mentioned 4d, but 4c and 4 on both sides are
On the surface opposite to the part corresponding to e, where 4f ′ and 4g ′ of the electrode film are removed, a bent or curved electrode film 4 is formed.
h and 4k are formed, also between the respective electrodes, slits S _4, S ₅ and S ₆ are provided.

FIG. 6 shows an equivalent circuit diagram of the coupling circuit board 3 forming an attenuation pole on the high frequency side of the pass band. Here, the capacitance formed by the electrode patterns 4f and 4j in FIG. 5 corresponds to C ₂ in FIG. Similarly, the capacitance of the electrode patterns 4g and 4j corresponds to C ₃ . The bent or curved electrode films 4h and 4k correspond to L ₁ and L ₂ , respectively, and are provided to obtain an impedance matching inductance between the dielectric resonators 1a and 1b and the input / output terminal 5.

Slits S ₅ and S ₆ are provided between the electrode patterns 4h, 4j and 4K, and the capacity of the slit S ₅ corresponds to C ₅ , and the capacity of S ₆ corresponds to C ₆ . The capacitances C ₅ and C ₆ are smaller than the capacitances C ₂ and C ₃ and form attenuation poles without an increase in insertion loss. If the electrode in the slit part is likely to be short-circuited, take measures to cover that part with insulating resin or glass, but since the capacitance of the slit part changes depending on the dielectric constant of the insulator, that part should be included in the design. Need to be kept. In any case, the capacitances C ₅ and C ₆ are finely adjusted.

FIG. 7 shows the filter characteristic. Capacitors C ₅ and C ₆ are formed on the coupling circuit board 3 of the dielectric filter having the filter characteristic shown in 7A to provide an attenuation pole on the high frequency side of the pass band, and 7B. The filter characteristics shown in are obtained.

Further, by adjusting the position of the attenuation pole by the capacitances C ₅ and C ₆ , the attenuation pole is formed at the position of the frequency twice the pass band as shown in 8B of FIG. It is also possible to improve the harmonic characteristics of.

The above-described high-frequency filter capacitively couples the dielectric resonators 1a and 1b with a plurality of electrode films 4 formed on both surfaces of one dielectric substrate 3a.
A slit is provided between these electrodes to allow dielectric resonators 1a, 1
A high-frequency filter with a small insertion loss and a high attenuation amount without adding a dielectric resonator, while achieving impedance matching between b and the input / output terminal 5 and forming an attenuation pole on the low frequency side or high frequency side of the pass band. Was realized.

In the above-described embodiment, the coupling circuit board 3 is placed vertically and is arranged face-to-face in front of the dielectric resonators 1a and 1b. However, as shown in FIG. In this case, the dielectric resonators 1a and 1b are arranged so as to be developed in front of the through holes 2a, so that filters having three or more dielectric resonators can be compactly assembled. That is, the dielectric filter having four dielectric resonators shown in FIG. 10 can be a compact dielectric filter having the equivalent circuit configuration shown in FIG.

The present invention is not limited to the above-mentioned embodiments, and various modifications and changes can be made without departing from the gist of the present invention.

[0035]

As described above, the present invention is a high-frequency filter that capacitively couples a plurality of dielectric resonators, and by separating the electrodes on the coupling circuit board with slits, it is possible to realize a minute capacitor that cannot be realized by a chip capacitor alone. The effect of realizing a small dielectric filter that has a high attenuation characteristic with low insertion loss without adding a dielectric resonator by forming a capacitance and forming an attenuation pole on the low frequency side or high frequency side of the pass band by this capacitance. Raised.

Further, according to the present invention, a plurality of electrodes are formed on both surfaces of one dielectric substrate to form a combined circuit board, which can be surface-mounted as it is, and the input / output terminals can be omitted. The number of parts has been reduced by increasing the number of parts and simplifying the structure, resulting in labor saving in assembly. As a side effect of the present invention, by adjusting the bandwidth of the pass band and the frequency of the attenuation pole,
A filter with improved harmonic characteristics can be obtained.

[Brief description of drawings]

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

FIG. 2 is a partial configuration diagram and a sectional view of an embodiment of a dielectric filter of the present invention.

FIG. 3 is an equivalent circuit diagram of an example of a dielectric filter of the present invention.

FIG. 4 is a filter characteristic diagram of an example of a dielectric filter of the present invention.

FIG. 5 is a partial configuration diagram of another embodiment of the dielectric filter of the present invention.

FIG. 6 is an equivalent circuit diagram of another embodiment of the dielectric filter of the present invention.

FIG. 7 is a filter characteristic diagram of another embodiment of the dielectric filter of the present invention.

FIG. 8 is a filter characteristic diagram of another embodiment of the dielectric filter of the present invention.

FIG. 9 is a partial configuration perspective view of another embodiment of the dielectric filter of the present invention.

FIG. 10 is a partial configuration diagram of another embodiment of the dielectric filter of the present invention.

FIG. 11 is an equivalent circuit diagram of another embodiment of the dielectric filter of the present invention.

FIG. 12 is an exploded perspective view of a conventional dielectric filter.

FIG. 13 is a partial configuration perspective view of a conventional dielectric filter.

FIG. 14 is a partial configuration perspective view of a conventional dielectric filter.

FIG. 15 is a partial perspective view of a conventional dielectric filter.

[Explanation of symbols]

1, 1a, 1b Dielectric resonator 2a Through hole 2b Electrode 3 Coupling circuit board 3a Dielectric substrate 4 Electrode film 4a, 4b, 4c, 4d, 4e Electrode pattern 5 Input / output terminal 6 Terminal 7 Case S, S ₁ , S ₂ , S ₃ slit

Claims (2)

[Claims] 1. A coupling filter in a dielectric filter, comprising: a plurality of dielectric resonators; and a coupling circuit board which is capacitively coupled to the plurality of dielectric resonators and comprises a dielectric board provided with input / output terminals. First terminals connected to the same main surface of the substrate and adjacent to each other, to which terminals of the dielectric resonator are connected
And a second electrode pattern, a third electrode pattern provided to face both the first and second electrode patterns with the coupling circuit board interposed therebetween, the third electrode pattern and the slit portion. An electrode pattern connected to the input / output terminal, which is separately disposed via the dielectric filter, is provided. 2. The dielectric filter according to claim 1, wherein the fourth electrode pattern has a bent and / or curved shape, and an electrode pattern is provided on a surface of the fourth electrode pattern facing the coupling circuit board. A dielectric filter characterized by having a portion which does not have.