JPH04371002A - Polarized dielectric filter - Google Patents

Abstract

PURPOSE:To improve the performance of a filter by connecting plural capacities such as coupling capacities and additional overcoupling capacities in series and realizing a set value with a high precision even in the case of combination of various set values of capacities. CONSTITUTION:Plural rectangular parallelepiped-shaped dielectrics 1 are unified into a dielectric resonator. Conductive metallized layers are formed on respective faces of these dielectrics 1 except pattern faces 9 by plating or the like as shown by oblique lines in the figure to hold the zero potential. A pattern face 2 is provided with hole parts 3-1 to 3-4 functioning as center conductors of the resonator and patterns 4-1 to 4-4 for frequency adjustment of the resonator. Hole parts 3-1 to 3-4 are inserted to terminals 5-1 to 5-4 for the purpose of obtaining the coupling capacity for coupling between the resonator and an external circuit and the the capacity of an overcoupling for formation of an attenuation pole in a limited frequency. Hole parts 8-1 to 8-4, a pattern 9-1 for terminal connection interposed between hole parts 8-1 and 8-2, a pattern 9-2 for terminal connection interposed between hole parts 8-3 and 8-4, and input/ output terminals (not shown in the figure) are formed on an upper face 7 of a printed wiring board 6 forming the external circuit.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a dielectric filter having a dielectric resonator in the microwave band, and in particular to a receiving filter for a branching filter of a mobile phone device or a car phone device that communicates at a frequency in the microwave band. The present invention relates to a dielectric filter used for.

0002

[Prior Art] This type of dielectric filter consists of a block-shaped dielectric material made of a homogeneous single body, such as a ceramic, in which a plurality of center conductors are provided approximately parallel to each other, each having a predetermined resonant frequency. A device is known in which desired frequency characteristics are obtained by forming a resonator. However, with the recent rapid increase in communication capacity, even higher performance is required of such dielectric filters. For this reason, in the attenuation characteristics of a dielectric filter, the amount of attenuation on the high frequency side with respect to its center frequency,
Dielectric filters are often required to have asymmetric attenuation characteristics, in which the amount of attenuation on the low frequency side is significantly different from each other.

[0003] This asymmetric attenuation characteristic can be easily achieved by a polarized dielectric filter, and is disclosed in Japanese Patent Application Laid-Open No. 1-318.
An example is disclosed in Japanese Patent No. 401. FIG. 2 is a perspective view showing the polarized dielectric filter. In the same figure, 1
1 is a rectangular parallelepiped (hereinafter referred to as a dielectric) having a length W, a width L, and a height H, and is made of an integral dielectric, for example, ceramic. In the illustrated position, the front of the dielectric 11,
On the back, left and right sides and bottom, as shown by diagonal lines,
For example, a conductive metallized layer is formed by plating.

Further, on the upper surface of the dielectric 11, conductive patterns 12-1 to 12-7 are arranged in order from the left side.
3-1 to 13-6. Dielectric 11
The patterns 12-1, 12-3, 12-5, 12-
Center conductors (hereinafter referred to as dielectric resonators) 14-1 to 14-4 that penetrate through the dielectric resonators 14-1 to 14-4 and function as dielectric resonators, and an external circuit 15 adjacent to the dielectric resonators 14-1 to 14-4. −
1 to 15-4 are provided embedded therein.

The external circuits 15-1 to 15-4 are connected between the dielectric resonator 14-1 and the dielectric resonator 14-2, and between the dielectric resonator 14-3 and the dielectric resonator 14-4. The pins 16-1 to 16-4 and the pins 16-1 to 16-4 are used to form attenuation poles by providing coupling capacitance between the pins 16-1 to 16-4.
Cylinders 17-1 to 17-4 having a radius D (>d) surrounding the cylinder and made of a dielectric material such as glass epoxy,
between pin 16-1 and pin 16-2, and between pin 16-1
and conductive wires 18-1 and 18-2 that electrically connect between the pin 16-2 and the pin 16-2.

Patterns 12-2, 12-4, 12-6 are similar to patterns 12-1, 12-3, 12-5 in operation.
, 12-7, and is provided as a capacitance adjustment electrode for adjusting the capacitance.

FIG. 3 is an equivalent circuit of the polarized dielectric filter shown in FIG. In FIG. 3, l1 is the inductance of the dielectric resonator 14-1, and C1 is the inductance of the dielectric resonator 14-1.
-1 capacitance, l2 is the inductance of the dielectric resonator 14-2, C2 is the capacitance of the dielectric resonator 14-2, l3
is the inductance of the dielectric resonator 14-3, C3 is the capacitance of the dielectric resonator 14-3, and l4 is the dielectric resonator 14.
-4 inductance, C4 is dielectric resonator 14-4
capacity.

Co1 connects pin 16-1 and dielectric resonator 14
-1, Co2 is the capacitance between pin 16-4 and dielectric resonator 14-4, and C12 is the capacitance between dielectric resonator 14-1 and dielectric resonator 14-2. C23 is the capacitance between the dielectric resonators 14-2 and 14-3, and C34 is the capacitance between the dielectric resonators 14-3 and 14-4. This is the capacity that exists in between.

CP1 connects pin 16-1 and dielectric resonator 14
-1 and the capacitance between pin 16-2 and dielectric resonator 1
4-2, Cp2 is the combined capacitance between pin 16
-3 and the dielectric resonator 14-3, and the capacitance between pin 1
This is the combined capacitance of the capacitance between the dielectric resonator 6-4 and the dielectric resonator 14-4.

lp1 is the inductance of the conductor 18-1 connecting pins 16-1 and 16-2, lp2
is the inductance of the conducting wire 18-2 connecting between pin 16-3 and pin 16-4.

[0011] Here, in general, |ωlp1|≪|1/ω
Since lp1 and Cp1 and lp2 and Cp2 are determined so as to satisfy Cp1| and |ωlp2|<<|1/ωCp2|, lp1 and lp2 may be ignored. Therefore, it is sufficient to consider an equivalent circuit including Cp1, Co1, C12, C1 and l1.

As can be seen from this equivalent circuit, in the above-mentioned polarized dielectric filter, a frequency where the amount of attenuation is almost infinite occurs on the low side of the passband, and the amount of attenuation on the low side of the passband increases. To achieve desired frequency characteristics with a filter having a small number of stages even if the amount of attenuation is larger than that on the high frequency side and severe attenuation is imposed on the low frequency side.

FIG. 4 shows an example of the attenuation characteristic when a reception filter for a duplexer of a car telephone device is constructed using the above-mentioned polarized dielectric filter. This duplexer reception filter is a 4-stage dielectric filter with polarity, but the AMP
S (Advanced Mobile Phone
This fully satisfies the specifications required for a reception filter for a duplexer of a car telephone device based on the System) system.

[0014]

However, in the polarized dielectric filter having the configuration shown in FIG. 2, in order to form an attenuation pole at a finite frequency, the capacitance value (Cp1 ) and the capacitance value (Cp2) of the third stage dielectric resonator is 0.7PF or less, and the length of the terminal inserted into the dielectric resonator is 1.80 mm or less. For this reason, it is virtually impossible to satisfy the required accuracy (0.7PF±0.1PF), which is a serious obstacle to improving the performance of dielectric filters.

[0015] The present invention provides the above capacitance values (Cp1, Cp
2) becomes smaller, and as a result, the terminal length becomes shorter, making it impossible to obtain the required accuracy and causing variations in the position of the attenuation pole frequency, making it impossible to obtain a high-performance dielectric filter. We aim to provide a high-performance dielectric filter in which the capacitance value is divided, the length of the terminal inserted into the problematic dielectric resonator is made as long as possible, and the other divided parts are made of a material with a low dielectric constant. purpose.

[0016]

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a plurality of dielectric resonators in a single dielectric, and connects a first stage dielectric resonator and a second stage dielectric resonator. By creating a coupling capacitance between the pre-final stage dielectric resonator and the final stage dielectric resonator through external circuits, a coupling capacitance and an additional overcoupling capacitance are formed, and the frequency is peaked at a finite frequency. In a polarized dielectric filter with
The coupling capacitor or the additional overcoupling capacitor is composed of a plurality of capacitors connected in series.

[0017]

[Operation] The capacitance value of each of the plurality of series-connected capacitors constituting the coupling capacitor or additional overcoupling capacitor can be made larger than the capacitance value of the coupling capacitor or additional overcoupling capacitor. Even if the set value of the coupling capacitor or additional overcoupling capacitor is small, the capacitance of the set value can be achieved with high precision, and a high-performance polarized dielectric filter can be obtained.

[0018]

Embodiment FIG. 1 is a perspective view showing an embodiment of the present invention. In FIG. 1, 1 is a rectangular parallelepiped dielectric with length W, width L, and height H, and has a structure in which multiple dielectric resonators (FIG. 1 shows the case of four) are integrated. . As shown by diagonal lines, each surface of the dielectric 1 except the pattern surface 2 has a conductive metallized layer formed thereon by, for example, plating, so that it can be maintained at zero potential. The pattern surface 2 of the dielectric 1 also has holes 3-1 to 3-4 that function as center conductors of the dielectric resonator, and frequency adjustment patterns 4-1 to 4-4 of the dielectric resonator. and is provided. 5-1 to 5-4 are terminals, and the dielectric 1 is used to obtain a coupling capacitance for coupling the dielectric resonator and an external circuit and an overcoupling capacitance for forming an attenuation pole at a finite frequency. are inserted into the holes 3-1 to 3-4. 6 is a printed wiring board forming an external circuit, and the upper surface 7 has holes 8-1 to 8-4, holes 8-1 and 8-2.
The connection pattern 9-1 electrically connects the terminals 5-1 and 5-2 through the holes 8-3 and 8-4, and the terminal 5-
connection pattern 9-2 for electrically connecting 3 and 5-4;
Input and output terminals are formed, and one ends of terminals 5-1 to 5-4 are inserted and fixed into the holes 8-1 to 8-4. Note that this printed wiring board 6 will be explained in detail later.

FIG. 5 shows the input and output capacitances (C0
1, C02) and overcoupling capacity (Cp1
, Cp2) and the terminal length for obtaining the set value. As shown in FIG. 5, the set values of each capacitance are small, so in order to accurately realize this polarized dielectric filter, the problem is how to accurately realize these small capacitance values.

For example, set value Cp1=0.
In order to obtain 56PF, the terminal length must be l=1.53mm, but the tolerance range of Cp1 is ±0.
Since it is 05PF, the error in this terminal length is ±0.13m.
It is necessary to keep it within the range of m. However, in reality, in addition to this error in the terminal length, there are errors due to variations in the dimensions and dielectric constant of the dielectric material filled between the terminal and the inner wall of the dielectric resonator hole, so Cp1 It is extremely difficult to keep the error range within ±0.05PF. By the way, if the capacitor (C0) is composed of two capacitors (C1, C2) connected in series, then (
1) The formula holds true.

CO = C1 C2 / (C1 + C2)
(1) As is clear from equation (1), the capacitance value C1
, C2 all take values larger than the capacitance value C0 of the composite capacitance. Therefore, a small capacitor can be divided into two large capacitors connected in series.

This embodiment focuses on this point, and as shown in FIG. 6, Cp1 = 0.56PF is realized by connecting capacitors having capacitance values of C1 = 2.71PF and C2 = 0.71PF in series. Similarly, Cp2 = 0.66PF is determined by C1 = 2.71PF and C2 = 0.87PF, and C01 is determined by C1 = 2.71PF and C2 = 4.22P.
These are realized by F. And each C
C1 of p1, Cp2, C01 = 2.71PF and C02
This is achieved by changing the terminal length as before. In this case, the terminal length is l=7.40 mm, which is within a range that can be realized with relatively high accuracy. On the other hand, C2 of Cp1 and Cp2 =0.
71PF and 0.87PF are realized by forming patterns as shown in FIG. 7 on the front and back surfaces of the printed wiring board 6 shown in FIG. That is, a glass epoxy substrate (εs = 4
．． 5, substrate thickness = 0.8 mm), C2 of Cp1
For =0.71PF, square patterns 21-1 and 21-2 having an area of 3.8 mm x 3.8 mm are formed on one side 19 and the other side 20 of the substrate, and square patterns 21-1 and 21-2 are formed facing each other on one side 19 and the other side 20 of the substrate. Similarly, for C2 = 0.87PF, one side 19 of the board and the other side 20 are 4.2 mm x 4.
．． Square pattern 21-3, 2 with an area of 2 mm
This is realized by forming 1-4 facing each other. Note that a chip capacitance of 23 is used for C2 = 4.22PF of C01.

By the method explained above, the overcoupling capacitance (Cp1, Cp2) and the input and output capacitance (C0
1, C02), the capacitance of short terminal lengths is eliminated, and the terminal length l = 7.4 mm (C1 = 2.71
PF), making it possible to realize a higher performance polarized dielectric filter.

8 and 9 show the input and output capacitance (C
01, C02) and overcoupling capacity (Cp1
, Cp2) is realized by another method. That is, as shown in FIG. 8, Cp1=0.
56PF is C1 = 1.65PF and C2 = 0.85PF
By connecting capacitors having a capacitance value in series, Cp
2=0.66PF is C1=1.65PF and C2=1
．． This is realized by connecting capacitors having a capacitance value of 10PF in series. Then, C1 = 1.65PF of each Cp1, Cp2 and C01, C02 are realized by the terminal length, Cp1
C2 of C2 = 0.85PF and C2 of Cp2 = 1.10P
For F, chip capacitors 24 and 25 are used. The chip capacitors 24 and 25 are mounted on a substrate as shown in FIG.
-4. As a result, each C1 due to the terminal length of Cp1 and Cp2 and each C2 due to the chip capacitance of Cp1 and Cp2 are connected in series.

Even with this method, even when the terminal length is short, l=4.51 mm, which is within the range that can be achieved with relatively high accuracy. Furthermore, the terminal lengths for C01, Cp1, and Cp2 can be unified, making it possible to realize a high-performance polarized dielectric filter.

[0026]

As described above in detail, according to the present invention, the coupling capacitor or additional overcoupling capacitor is realized by a plurality of capacitors connected in series. Even when the set value of the coupling capacitance is small, the set value can be achieved with high accuracy by combining capacitors with relatively large capacitance values. Therefore, a high-performance polarized dielectric filter can be realized.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional polarized dielectric filter.

FIG. 3 is an equivalent circuit diagram of the polarized dielectric filter shown in FIG. 2;

FIG. 4 is an attenuation characteristic diagram of a polarized dielectric filter.

5 is a perspective view showing an example of capacitance setting values and terminal lengths of the polarized dielectric filter shown in FIG. 1; FIG.

FIG. 6 is an explanatory diagram of a method (1) for realizing the capacitance setting value shown in FIG. 5;

FIG. 7 is a diagram of a board realizing the capacitance value shown in FIG. 6;

FIG. 8 is an explanatory diagram of a method (2) for realizing the capacitance setting value shown in FIG. 5;

9 is a diagram of a board realizing the capacitance value shown in FIG. 8. FIG.

[Explanation of symbols]

1 Dielectric 2 Pattern surfaces 3-1 to 3-4 Holes 4-1 to 4-4 Frequency adjustment patterns 5-1 to 3-4
5-4 Terminals 8-1 to 8-4 Terminal fixing holes 9-1 to 9-2
Connection patterns 21-1 to 21-4 Patterns 23 to 25 forming capacitance Chip capacitance

Claims (1)

[Claims] Claim 1: A plurality of dielectric resonators are formed in a single dielectric material, and a plurality of dielectric resonators are formed between a first stage dielectric resonator and a second stage dielectric resonator, and between a pre-final stage dielectric resonator and a final stage dielectric resonator. In a polarized dielectric filter that has a pole at a finite frequency by forming a coupling capacitance and an additional overcoupling capacitance by creating a coupling capacitance between the body resonator and the body resonator through an external circuit, the coupling 1. A polarized dielectric filter comprising a plurality of capacitors connected in series, each of which is an overcoupling capacitor or an additional overcoupling capacitor.