JPH03254515A - Band pass filter - Google Patents

Abstract

PURPOSE:To make a single pole at a frequency lower than a center frequency closer to the center frequency by forming a coupling coupled inductor prolonged from a capacitor electrode of a 1st resonator to an inductor electrode of a 2nd resonator onto a dielectric layer. CONSTITUTION:Capacitor electrodes 2a, 3a and 2b, 3b are opposed to each other respectively while a dielectric layer 1 is held therebetween respectively in a couple of left U-shaped electrode patterns 2, 3 and inductor electrodes 2c, 3c are formed not to be opposed to each other. Since the capacitor electrodes 2a, 3a and 2b, 3b have the dielectric layer 1 inbetween, they act like a capacitor and the inductor electrode 2c, 3c not opposed to each other act like an inductor. Then the two U-shaped electrode patterns 2, 3 form a resonator A, which consists of a series connection of two each of alternately arranged capacitors and inductors. Another couple of right U-shaped electrode patterns 4, 5 constitute a resonator B, which consists of a series connection of two each of alternately arranged capacitors and inductors.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bandpass filter, and in particular to a novel bandpass filter that can bring a pole that occurs at a frequency lower than the center frequency closer to the center frequency in the filter characteristics. Regarding the provision of filters.

As a conventional bandpass filter, one shown in FIG. 4 is known. This filter has a common dielectric layer 20
Two resonators Ql and Q2 are arranged in a magnetically coupled state along A pair of U-shaped electrode patterns 21 and 22 (23
24), patterned pairs of capacitor electrodes 21a and 22a, 21b and 22b (23a and 23a and 22b) with the dielectric layer 20 in between.
4a, '23b and 24b) are arranged facing each other. However, in order to generate a ball in the cutoff region in the filter characteristic, the two resonators Ql and Q2 are connected by an inductor connecting electrode 2-J). still,
In the figure, the electrode patterns 21 and 23 indicated by solid lines are the dielectric layer 2.
Electrode patterns 22 and 24 indicated by broken lines are formed on the upper surface of the electrode 0 and the lower surface thereof.

The circuit configuration of such a filter includes each electrode pattern pair 21.
Dielectric JiN20 between 22 and 23.24
Capacitor electrodes 21a and 22a, 21 facing each other with
b and 22b, etc., form a capacitor, while the inductor electrodes 21C, 22c, etc. that do not face each other form an inductor, and the input terminal 27 is connected to the A2 part.
An output terminal 28 is connected to the fourth section, and a ground terminal 29 is connected between the A2 section and the A4 section. Here, between capacitor electrodes 21a and 22a, between 21b and 22b, 23
capacitors C1l, C12, C13, C14 between 23b and 24b, respectively, and inductors Lll, L12 .
L13. When Li2 and Li2 are used, this circuit becomes as shown in FIG. Note that L16 in the figure is the inductance generated at the ground terminal when this filter is mounted, C6 is the capacitance between capacitors C11 and C13, and M is the capacitance between Lll and Li2. shows magnetic coupling.

However, in the case of the above filter, the frequency characteristics are such that the balls PI and P2, which determine the ends of the usage band, occur symmetrically with respect to the center frequency, as shown in Figure 6. Therefore, it is not possible to adjust the bandwidth of the passband by changing the frequency of one ball alone.

As a technique for changing the bandwidth, as shown in Figure 7, the frequency characteristics can be changed by moving the position of the ground terminal from ■ to ■ or ■ while leaving the input/output terminals as they are. As shown in FIG. 8, the inventor of the present invention has confirmed a technique that can change the width of the used band by changing from ■ to ■ to ■. I can't.

The present invention has been made in view of this problem, and an object of the present invention is to provide a bandpass filter that can independently bring a ball lower than the center frequency closer to the center frequency.

In the present invention, a pair of U-shaped electrode patterns in which two capacitor electrodes are connected by one inductor electrode are arranged with the U-shaped electrodes facing each other with a dielectric layer in between. A first resonator consisting of a resonator and a second resonator consisting of a pair of U-shaped electrode patterns similar to the first resonator were magnetically coupled on a common dielectric layer. The bandpass filter is characterized in that a coupled inductor extending from the capacitor electrode of the first resonator and reaching the inductor electrode of the second resonator is formed on the dielectric layer.

In the present invention, since the capacitor electrode of the first resonator and the inductor electrode of the second resonator are connected by the coupled inductor, as shown in FIG. Only the ball P1 on the side lower than the frequency F is in a state close to the center frequency.

FIG. 1 is a plan view showing a bandpass filter according to the present invention. This filter has a dielectric layer 1 made of a ceramic substrate or the like, and a pair of U-shaped electrode patterns 2 and 3 are formed on the left half of the dielectric layer 1 with a dielectric layer l in between. Similarly, there is a pair of U-shaped electrode patterns 4 on the right side.
5 is formed with a dielectric layer 1 in between, and each U-shaped electrode pattern 2, 3, 4.5 has two capacitor electrodes 2.
It has a U-shape in which a, 2b, 3a, 3b, 4a, 4b, 5a, and 5b are connected by one inductor electrode 2c, 3c, 4c, and 5c, respectively.

A pair of U-shaped electrode patterns 2 and 3 on the left side have capacitor electrodes 2a and 3a facing each other and 2b and 3b facing each other with a dielectric layer l in between, and an inductor electrode 2c,
It is a formality that 3c is not facing. The capacitor electrodes 2a and 3a that face each other and the capacitor electrodes 2b and 3b that face each other function as a capacitor because the dielectric layer 1 is interposed between them, and the inductor electrodes 2c and 3c that do not face each other function as an inductor. Therefore, these two U-shaped electrode patterns 2 and 3 constitute a resonator A in which capacitors and inductors are connected alternately and two each in series.

The other pair of U-shaped electrode patterns 4°5 on the right side are
The capacitor electrodes 4a, 5a and 4b, 5b are opposed to each other with the dielectric layer 1 in between, and the inductor electrode 4c
, 5c are formed so as not to face each other. Since the capacitor electrodes 4a and 5a and 4b and 5b which face each other have the dielectric layer 1 interposed therebetween, they function as a capacitor, and the inductor electrodes 4c and 5c which do not face each other function as an inductor. Therefore, these two U-shaped electrode patterns 4.5 have capacitors and inductors alternately.
In addition, a resonator B is formed by connecting two of them in series.

These two resonators A and B are connected to the capacitor electrode 3b of the lower U-shaped electrode pattern 3 constituting one resonator A.
and the inductor electrode 5C of the lower U-shaped electrode pattern 5 constituting the other resonator B are connected by a coupled inductor 6 formed on the lower surface side of the dielectric layer 1.
This coupled inductor 6 functions as an inductor.

Therefore, the bandpass filter having such a structure has a circuit configuration in which the capacitor of one resonator A and the coil of the other resonator B are connected by a coupled inductor 6. Note that input terminal 7. The output terminal 8 and the ground terminal 9 shall be installed at the conventional positions. Further, the coupled inductor 6 may be formed so as to extend from the inductor electrode 5C and reach the upper capacitor electrode 2b forming the capacitor together with the capacitor electrode 3b via a through hole penetrating the dielectric layer 1. good.

Here, the capacitor formed by capacitor electrodes 2a and 3a is called CI, and capacitor electrode 2b.

The capacitor formed by the capacitor electrodes 4a and 5a is called 02, and the capacitor formed by the capacitor electrodes 4a and 5a is called C3.
The capacitor formed by 4b and 5b is designated as 04,
Inductor electrodes 2c, 3c.

The inductor formed by 4c and 5c is Ll, L2゜L3
．． L4, and the inductor of coupled inductor 6 is L5.
Then, the bandpass filter having the above configuration becomes an equivalent circuit shown in FIG. Note that L6 in the figure is the inductance generated at the ground terminal when this filter is mounted, C8 is the capacitance between capacitors C1 and 03, and M is the magnetic field between Ll and L3. Indicates a bond.

FIG. 3 is a graph showing the frequency characteristics of the bandpass filter having the above configuration. As you can understand from this graph,
The ball P1, which is lower than the center frequency, is in a state where it approaches the center frequency alone. The degree to which they approach each other varies depending on the position where both ends of the coupled inductor 6 are connected to the inductor electrode 5c or the capacitor electrode 2b or 3b, so when manufacturing one with desired characteristics,
Align both ends of the coupled inductor 6 at appropriate positions.

In the above embodiment, the capacitor C2 of one resonator A and the coil L3 of the other resonator B are connected by the coupled inductor 6, but in the present invention, the input/output terminals and the ground terminal are placed at appropriate positions. For example, between L3 and C1, L4 and C
1 or C2, or between Ll and 03 or C4,
It is also possible to connect L2 and C3 or C4, and to connect the human/output terminal and the ground terminal so as to form the equivalent circuit shown in FIG.

As described in detail above, in the case of the present invention, the capacitor electrode of the first resonator and the inductor electrode of the second resonator are connected by the coupled inductor. As such, there is an excellent effect that only the pole P1 on the side lower than the center frequency F can be brought close to the center frequency.

[Brief explanation of drawings]

Fig. 1 is a plan view showing a band pass filter according to the present invention, Fig. 2 is an equivalent circuit diagram thereof, Fig. 3 is a frequency characteristic diagram thereof, Fig. 4 is a plan view showing a conventional band pass filter, and Fig. 5 is a plan view showing a band pass filter according to the present invention. Figure 6 is an equivalent circuit diagram of the filter, Figure 6 is a frequency characteristic diagram of the filter, Figure 7 is a plan view of the filter shown in Figure 4 with the ground terminal installed in a different position, and Figure 8. is a frequency characteristic diagram based on the change. 1... Dielectric layer, 2, 3, 4.5... U-shaped electrode pattern, 2a, 2b, 3a, 3b, 4a, 4b. 5a, 5b-+ capacitor electrode, 2C, 3c, 4c. 5C...Inductor electrode, 6...Coupled inductor.

Claims (1)

[Claims] (1) A pair of U-shaped electrode patterns in which two capacitor electrodes are connected by one inductor electrode are arranged with the two U-shaped electrodes facing each other with a dielectric layer in between.
and a second resonator formed of a pair of U-shaped electrode patterns like the first resonator are magnetically coupled on a common dielectric layer. A bandpass filter characterized in that a coupled inductor extending from a capacitor electrode of the first resonator and reaching an inductor electrode of the second resonator is formed on the dielectric layer.