JPH10145109A - Dielectric filter - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide a low-cost dielectric filter that improves the attenuation characteristics of harmonics without deteriorating the filter characteristics and does not increase the number of components. SOLUTION: A plurality of resonator through-holes 12 are provided in the longitudinal direction of a dielectric block 11, and input / output terminal through-holes 13 are provided at both ends thereof, and a conductor layer F is formed on an inner surface of each through-hole and an outer surface of the block. Further, one end surface conductor of the resonator through hole is removed to form λ / 4 resonators 12a and 12b, and the upper and lower surface conductors of the input / output terminal through hole are removed to form input / output electrodes 13a and 13b. In the integrated multi-stage dielectric filter described above, the length D of at least one of the internal conductors of the through hole for the input / output terminal is set to a required length that resonates at λ / 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to radio equipment using microwaves, for example, cellular phones, car phones, GPs, and the like.
S, or a dielectric filter used for a cordless telephone or the like.

[0002]

2. Description of the Related Art Conventionally, as this kind of dielectric filter,
The structure shown in FIGS. 8 to 10 is known. As shown in FIG. 10, the dielectric filter denoted by reference numeral 1 in these figures is provided with a plurality of resonator through-holes 3 from the top surface in the longitudinal direction to the bottom surface of the dielectric block 2 having a rectangular parallelepiped shape. Input / output terminal through holes 4 are provided at both ends in the block longitudinal direction, a conductor layer F is formed on the inner surface of each through hole 3 and the outer surface of the block 2, and one end surface conductor of the resonator through hole 3 is formed. By removing the λ / 4 resonators 3a and 3
b, and the conductors at the upper and lower end surfaces of the input / output terminal through hole 4 are removed (the portion from which the conductor layer is removed is denoted by C
), Input / output electrodes 4a and 4b are formed, and
The input / output electrodes 4a and 4b are connected to input / output terminals 5 and 6, which also serve as mounting terminals for the dielectric filter 1, respectively.

The illustrated dielectric filter 1 is of a comb line type in which the removed portions C of the conductor layers of the resonators 3a and 3b are located on the same side of the dielectric block 1.
There is also an interdigital type in which the removal portions C of the resonators 3 are alternately formed on a pair of parallel surfaces of the dielectric block 1.

In the conventional dielectric filter 1 configured as described above, the input / output electrodes 4a and 4b and the resonators 3a and 3b, and the resonators 3a and 3b are capacitively coupled to each other.
The resonators 3a and 3b resonate in a predetermined frequency band with respect to a high frequency input from one input / output electrode 4a, and this frequency band is output from the other input / output electrode 4b. Because of its advantages such as light weight and little influence on temperature change, it is widely used in portable communication devices, in-vehicle communication devices, and the like.

[0005]

Although such a conventional dielectric filter 1 has the various advantages described above, it still has the following problems to be improved.

[0008] That is, the attenuation characteristics of the dielectric filter 1 described above are as shown in FIG. In this example, an example is shown in which a frequency band having a fundamental wave of 1575 MHz is set to be extracted. However, as shown by a region A in this figure, in a high frequency region, a third harmonic of the fundamental wave, namely, The third harmonic is generated, and this third harmonic is output from the dielectric filter 1. It has been confirmed that such a phenomenon occurs not only in the third harmonic but also in the fifth harmonic.

As one method for solving such a problem, conventionally, a low-pass filter is connected to the dielectric filter 1 to attenuate unnecessary harmonics such as the third and fifth harmonics described above. However, the insertion loss of the filter characteristics of the dielectric filter 1 is deteriorated, the impedance mismatch is caused by the connection method, and the insertion loss and the return loss are further deteriorated. However, a new problem arises in that the size of the device increases and the cost of the device rises.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to improve a harmonic attenuation characteristic without deteriorating a filter characteristic and to provide a low-cost dielectric material without increasing the number of parts. It is intended to provide a body filter.

[0009]

According to a first aspect of the present invention, there is provided a dielectric filter for solving the above-mentioned problems.
A plurality of resonator through-holes are provided in the longitudinal direction of the dielectric block, and input / output terminal through-holes are provided at both ends thereof, a conductor layer is formed on the inner surface of each through-hole and the block outer surface, and one of the resonator through-holes is formed. In the dielectric filter having an integrated multi-stage structure, the end face conductors are removed to form a λ / 4 resonator, and the upper and lower end face conductors of the input / output terminal through holes are removed to provide input / output electrodes. The length of at least one of the internal conductors of the through hole is set to a required length that resonates at λ / 2.

According to a second aspect of the present invention, in the dielectric filter according to the first aspect, the portion where the through hole for the input / output terminal is formed has a length corresponding to the length of the conductor layer inside the through hole for the input / output terminal. It is characterized in that it is formed to a length substantially equal to

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

The dielectric filter according to the present embodiment, which is denoted by reference numeral 10 in FIG. In addition to providing the holes 12, through holes 13 for input / output terminals are provided at both ends in the longitudinal direction of the dielectric block 11, and a conductor layer F is formed on the inner surface of each through hole 12 and the outer surface of the dielectric block 11. Further, one end face conductor of the through hole for resonator 12 is removed to form λ / 4 resonators 12a and 12b,
The conductors at the upper and lower end surfaces of the input / output terminal through-hole 13 are removed (the portion from which the conductor layer F is removed is indicated by reference character C) to form input / output electrodes 13a and 13b.
The configuration is such that the length D of the conductor layer F formed on at least one electrode 13a of the electrode 13b is set to a required length that resonates at λ / 2.

The dielectric block 11 is formed, for example, by compacting barium titanate powder into a predetermined shape and then sintering it at a predetermined temperature. Four parallel through holes are formed.

The conductor layer F is formed by baking silver paste or plating with copper, silver, or the like, and has a thin film over the entire surface of the dielectric block 11 and the entire inner surface of all the through holes. It is formed in a shape.

A conductor layer F formed on the inner surfaces of two through holes located inside both ends of the dielectric block 11 in the longitudinal direction of the four through holes has a tapered reamer at one open end thereof. And the like, the one open end is an open part where the conductor layer F on the inner surface and the conductor layer F on the outer surface of the dielectric block 11 are separated, and the other open end is formed. However, a short-circuit portion is formed in which the inner tail conductor layer F and the conductor layer F on the outer surface of the dielectric block 11 are continuous, thereby forming the pair of λ / 4 resonators 12a and 12b as described above. ing.

Further, the conductor layers F formed on the inner surfaces of the two through holes located on the outside are removed by taper reamers or the like at both open ends, and are formed on the outer surface of the dielectric block 11. An independent conductive layer F that is not conductive with the conductive layer F is formed, and thereby,
Two input / output electrodes 13a and 13b are formed.

Further, in this embodiment, the conductor layer F forming the one input / output electrode 13a is removed from the other opening end side over a predetermined distance by means such as cutting. The length D of the conductor layer F of the input / output electrode 13a is about 2/3 of the length L of the through hole as described above.

The input / output electrodes 13a and 13b
Are electrically connected to input / output terminals 14 and 15 formed of a metal having excellent conductivity, thereby forming a comb-line type dielectric filter 10. In the present embodiment, the dielectric filter 10 Reference numeral 10 denotes a bandpass filter having a fundamental wave of 1575 MHz and a pass band of a frequency band in the vicinity thereof.

The dielectric filter 10 according to the present embodiment having such a configuration has one input / output terminal 14 (15).
Attenuates the frequency region outside of the pass band of the high frequency input from the device, and outputs the high frequency within the pass band. However, the length D of the conductor layer F of the input / output electrode 13a is reduced as described above. Because it is about 2/3 of the length L,
The resonance frequency corresponding to the length of the input / output electrode 13a is:
The frequency is three times the fundamental wave, whereby the third harmonic (third harmonic) of the fundamental wave is attenuated.

Here, when the filter characteristics of the dielectric filter 10 according to the present embodiment were measured, the results shown in FIG. 7B were obtained. As shown by a region B in this figure, the third harmonic of the fundamental wave (1575 MHz) is greatly attenuated, and the influence on other bands is hardly observed. It can be seen that no insertion loss has occurred due to the insertion of.

As described above, according to the dielectric filter 10 according to the present embodiment, the harmonics are attenuated in the dielectric filter 10 itself, and the harmonic characteristics are improved without newly adding a low-pass filter. .

Therefore, the harmonic characteristics can be improved without deteriorating the filter characteristics such as deterioration of insertion loss and return loss and mismatch of impedance.

In addition, since the above-described action is obtained by the internal processing of the dielectric block 11 such as the adjustment of the length of the input / output electrodes 13a and 13b, the dielectric filter 10 is not increased in size. There is no need to add other equipment, and the cost does not rise.

The various shapes, dimensions, and the like of the respective components shown in the above embodiment are merely examples, and can be variously changed based on required performance, design requirements, and the like.

For example, in the above embodiment, the length D of one input / output electrode 13a is set to 2/3 of the length L of the through hole.
However, as shown in FIG. 2, the other input / output electrode 13b may have a length of 2L / 3. With such a configuration, a more reliable harmonic attenuation characteristic can be obtained by obtaining a harmonic attenuation function at two points on the input side and the output side of the dielectric filter 10.

Further, by setting D = 2L / 5, the fifth harmonic can be attenuated.
As shown in FIG. 3, one input / output electrode 13a has a length of 2L / 3 for attenuating the third harmonic, and the other input / output electrode 13a has a length of 2L / 3.
By setting b to be a length of 2L / 5 for the attenuation of the fifth harmonic, it is possible to simultaneously improve the attenuation characteristics of both the third harmonic and the fifth harmonic. .

On the other hand, when the length of the input / output electrode 14 is adjusted, a method of removing the conductive layer F formed on the inner surface of the through hole by cutting is exemplified. May be applied to a predetermined length and baked, or the masking may be applied to a portion corresponding to a region to be removed, and the masking may be removed after the formation of the conductor layer F. The length of the input / output electrodes 13a and 13b can be adjusted.

Further, as shown in FIGS. 4 to 6, the portions of the dielectric block 11 where the input / output electrodes 13a and 13b are formed are previously set in the input / output electrodes 13a and 13b.
b is formed to have a length substantially equal to the length of the conductor layer F,
After the conductor layer F is formed on all of the outer surface of the dielectric block 11 and the inner surface of the through hole, the conductor layer F at each opening end of the through hole is removed, so that the input / output electrode 13
It is also possible to set the length of a · 13b to a predetermined length.

With such a configuration, the input / output electrodes 13a and 13b having the conductor layer F of a predetermined length can be formed by a simple operation such as cutting of the opening end of each through hole.
Is obtained.

[0030]

As described above, according to the first aspect of the present invention,
According to the dielectric filter according to the above, the length D of at least one conductor layer of the input / output electrodes formed on the dielectric block is
Is set to a length that resonates at λ / 2, so that the resonance frequency corresponding to the entire length of the input / output electrode whose length has been adjusted is
The frequency is set to 2 to 5 times the fundamental wave of the pass frequency band set in the dielectric filter, whereby the 2nd harmonic (2nd harmonic) to 5th harmonic (5th harmonic) of the fundamental wave is ensured. Can be attenuated.

Further, since the harmonics are attenuated by the dielectric filter itself, it is not necessary to newly add a low-pass filter, and not only can a small and inexpensive dielectric filter be obtained, but also insertion loss and the like can be reduced. It is possible to obtain a dielectric filter having significantly improved harmonic attenuation characteristics without deteriorating filter characteristics such as deterioration of return loss or impedance mismatch.

Further, according to the dielectric filter of the second aspect of the present invention, the portion of the dielectric block where the input / output terminal through-hole is formed is the length of the input / output terminal through-hole internal conductor layer. The input / output electrodes of a predetermined length can be formed by a simple operation such as removal of the conductor layer at the opening end of the input / output terminal through-hole. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a dielectric filter according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a dielectric filter showing a modification of the present invention.

FIG. 3 is a longitudinal sectional view of a dielectric filter showing a modification of the present invention.

FIG. 4 is a longitudinal sectional view of a dielectric filter showing a modification of the present invention.

FIG. 5 is a longitudinal sectional view of a dielectric filter showing a modification of the present invention.

FIG. 6 is a longitudinal sectional view of a dielectric filter showing a modification of the present invention.

FIG. 7 is a diagram showing attenuation characteristics of a conventional dielectric filter and attenuation characteristics of a dielectric filter according to an embodiment of the present invention.

FIG. 8 is an external perspective view showing one structural example of a conventional dielectric filter.

9 is an external perspective view showing a state where the dielectric filter shown in FIG. 8 is viewed from the opposite side.

FIG. 10 is a longitudinal sectional view of a conventional dielectric filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Dielectric filter 11 Dielectric block 12 Resonator through-hole 12a ・ 12b λ / 4 resonator 13 I / O terminal through-hole 13a ・ 13b I / O electrode 14.15 I / O terminal C Conductor layer removal part F Conductor layer

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Hirofumi Nishizawa 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd.

Claims (2)

[Claims] A plurality of resonator through holes (12) are provided in the longitudinal direction of a dielectric block (11) and input / output terminal through holes (13) are provided at both ends thereof. A conductor layer (F) is formed on the inner surface and the outer surface of the block (11), and one end face conductor of the resonator through-hole (12) is removed to form a λ / 4 resonator (12a, 12b). In a dielectric filter having an integrated multi-stage structure in which conductors at the upper and lower ends of the through holes for input / output terminals (13) are removed to form input / output electrodes (13a and 13b), at least one of the through holes for input / output terminals (13) is provided. Length of internal conductor D
Is set to a required length that resonates at λ / 2. 2. The dielectric filter according to claim 1, wherein a portion where the input / output terminal through-hole (13) is formed is substantially equal to a length D of the input / output terminal through-hole internal conductor layer. A dielectric filter formed to have a length of