JP2613194B2 - Ceramic trap element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic trap element, in which three resonators are connected in a π shape between input and output terminals, thereby eliminating an external inductor and reducing the number of components. Together with
It is intended to simultaneously increase the amount of attenuation in the trap characteristics and improve the shoulder characteristics.

2. Description of the Related Art A ceramic trap element is used for a circuit element for removing an audio signal included in a video signal, for example, in a television receiver. 10 and 11 show a conventional ceramic trap element. Two pairs of electrodes (2, 4) and (3, 5) are arranged at opposing positions on both sides in the thickness direction of the piezoelectric ceramic substrate 1. The resonator A is formed by the electrode pair (2, 4) and the resonator B is formed by the electrode pair (3, 5). The electrodes 4 and 5 are electrically connected by the conductive portion 6. The electrodes 2, 3 are led out to the same edge side of the piezoelectric ceramic substrate 1 by lead electrodes 2a, 3a, and an input terminal 7 and an output terminal 8 are fixed to the lead electrodes 2a, 3a by soldering. Also, a common terminal 9 that is drawn out in the same direction as the input terminal 7 and the output terminal 8 is fixed to the conductive portion 6 by soldering.

FIG. 12 is a circuit symbol of the conventional ceramic trap element shown in FIGS. 10 and 11, and includes a resonator A composed of the electrode pair (2, 4) and a resonator B composed of the electrode pair (3, 5). To
A two-element type in which the electrodes 4 and 5 are electrically connected by a conductive part 6 for conducting the electrodes 4 and 5 and a common terminal 9 soldered to the conductive part 6, and the electrodes 2 and 3 are made independent of an input terminal 7 and an output terminal 8. A three-terminal trap circuit is formed. In an actual trap circuit, an inductor L is connected between an input terminal 7 and an output terminal 8 for use. This inductor L is an external component.

Fig. 13 shows the trap characteristics, with the horizontal axis representing the frequency (MHz).
And the vertical axis indicates the trap amount (dB). The audio intermediate frequency (hereinafter referred to as SIF) contained in the video signal is
Since 4.5MHz and the video intermediate frequency (hereinafter referred to as PIF) are 4.5MHz or less, when configuring a trap circuit to remove the SIF signal using a ceramic trap element, the trap characteristics are as follows in SIF (4.5MHz). The trap amount is large, the attenuation in the PIF region is small, and the SI
It is important that the attenuation characteristic toward F (4.5 MHz) is sharp, that is, the droop of the shoulder (a) is steep and the shoulder characteristic is sharp.

Problems to be Solved by the Invention However, in the conventional ceramic trap element, since the inductor L must be externally connected between the resonators A and B in actual use, the number of parts increases accordingly.
This is an obstacle to downsizing the circuit configuration, and also reduces usability.

When the inductor L is used, if the inductance value is low, the trap attenuation decreases as shown in FIG. 14, and if the inductance value increases, the trap attenuation decreases as shown in FIG. 15 and FIG. The amount of attenuation increases. However, as apparent from the comparison between FIG. 15 and FIG. 16, when the inductance value is increased to increase the trap attenuation, there arises a problem that the shoulder characteristics deteriorate.

As a result, in the conventional ceramic trap element using the inductor L, it is difficult to obtain a ceramic trap element having a large trap attenuation and a sharp shoulder characteristic.

The characteristics shown in FIGS. 14 to 16 are obtained by the measurement circuit shown in FIG. In FIG. 17, the following resonators A and B constituting the ceramic trap element were used.

Resonance frequency Fr = 4.5MHz Anti-resonance frequency Fa = 5.2MHz Resonance resistance Rφ = 16Ω Capacitance Cd = 65PF And, for the above ceramic trap element, as inductor L, inductance value L = 0.1μH, 10μ
H, 30 μH were externally attached. The input resistance is 330Ω, and the resistance connected to the output side is 1KΩ. 10 is a signal source.

Means for Solving the Problems In order to solve the conventional problems described above, a ceramic trap element according to the present invention includes a first resonator, a second resonator, and a third resonator. . Each of the first resonator, the second resonator, and the third resonator has a pair of electrodes formed on the front and back of a piezoelectric substrate. In the first resonator, one of the pair of electrodes is connected to one input terminal. In the second resonator, one of the pair of electrodes is connected to the one output terminal. The other of the pair of electrodes of the first resonator and the second resonator is commonly connected to a common terminal. The third resonator is inserted between the input terminal and the output terminal,
The pair of electrodes are connected to the input terminal and the output terminal, respectively.

Further, the resonance frequency of the first resonator is Fr1, the anti-resonance frequency is Fa1, and the resonance frequency of the second resonator is Fr.
2. When the anti-resonance frequency is Fa2, the resonance frequency of the third resonator is Fr3, and the anti-resonance frequency is Fa3, Fr3 ≦ Fr1, Fr2 Fr1, Fr2 ≦ Fa3 + 0.2 (Fa3−Fr3) .

Operation As described above, the first resonator connected to the input terminal, the second resonator connected to the output terminal, and the third resonator connected between the input terminal and the output terminal With such a configuration, the third resonator functions similarly to the inductor between the resonance frequency (Fr ₃ ) and the anti-resonance frequency (Fa ₃ ), so that an external inductor is not required.

Also, unlike the case of an external inductor, the inductance component of the third resonator can be easily increased to several hundred μH, so that the attenuation in the trap characteristic can be increased, and the resonance frequency (Fr ₃ ) Anti-resonance frequency (Fa ₃ )
Except during the period, it does not act as an inductor, so that the shoulder characteristics are not deteriorated.

Further experiments show that the resonance frequency of the first resonator is
Fr _1, the anti-resonant frequency and Fa _1, wherein the resonant frequency of the second resonator Fr _2, the anti-resonance frequency and Fa _2, wherein the third resonator Fr ₃ the resonance frequency of the antiresonance frequency Fa ₃ and the time, when chosen to satisfy the _{Fr 3 ≦ Fr 1, Fr 2} Fr 1, Fr 2 ≦ Fa 3 +0.2 (Fa 3 -Fr 3), the trap attenuation is 70 to 10
It has been found that the trap attenuation reaches about 0 dB, which is about twice that of the conventional external inductor, and that an extremely sharp shoulder characteristic can be obtained.

Embodiment FIG. 1 is a plan view of a ceramic trap element according to the present invention, and FIG. 2 is a bottom view of the same. In this embodiment, electrode pairs (12, 14) and (13, 15) facing each other on both sides in the thickness direction are provided on both sides of the piezoelectric ceramic substrate 11,
Resonators A and B are formed by these electrode pairs (12, 14) and (13, 15), and are located at substantially intermediate positions of the electrodes 12-13 on one surface of the piezoelectric ceramic substrate 11 having the electrodes 12, 13. An electrode 18 electrically connected to the electrode 12 and the conductive portion 17 is formed, and at a substantially intermediate position between the electrodes 14 and 15 on the other surface of the piezoelectric ceramic substrate 11, the electrode 18 and the conductive portion 19 face the electrode 18. An electrically conductive electrode 20 is formed, and this electrode 1
The third resonator C is formed by 8 and 20.

Then, the input terminal 21 is connected and fixed to the lead electrode 12a extended from the electrode 12, and the common terminal 22 is connected to the lead electrode 14a led from the electrode 14 and the lead electrode 13a led from the electrode 13. A lead electrode 15a connected in common on the front and back sides of the piezoelectric ceramic substrate 11 and further led from the electrode 15.
The output terminal 23 is connected and fixed.

FIG. 3 is a circuit symbol of the ceramic trap element shown in the above embodiment, in which a first resonator A connected to the input terminal 21 and a second resonator B connected to the output terminal 23 are
Π connected in common by a common terminal 22 and a third resonator C is connected between the input terminal 21 and the output terminal 23.
A ceramic trap circuit of the type is obtained. In comparison with the related art, the circuit configuration is such that the external inductor is replaced by the third resonator C.

Plan view in Figure 4 another embodiment, Figure 5 is also a bottom view thereof, FIG. 6 is a cross-sectional view in Figure 4 A ₁ -A ₁ line. In this embodiment, a first resonator A and a second resonator B are formed on a first piezoelectric ceramic substrate 11a, and a second piezoelectric ceramic substrate 11b is formed on the first piezoelectric ceramic substrate 11a. Are laminated, and the third resonator C is formed using the second piezoelectric ceramic substrate 11b. The first resonator A comprises an electrode pair (12, 14) formed at opposing positions on the front and back of the piezoelectric ceramic substrate 11a.
An input terminal 21 is connected and fixed to a lead electrode 12a extended from 12. The second resonator B is a piezoelectric ceramic substrate 11a.
The electrode terminal (13, 15) is formed at the opposing position on the front and back of the electrode 13 and the output terminal 23 is connected to the lead electrode 13a extended from the electrode 13.
Is fixedly connected. The electrode 14 of the first resonator A and the second
The electrodes 15 of the resonator B are commonly connected by a conductive portion 25,
The common terminal 22 is connected and fixed to a lead electrode 25a extended from the conductive portion 25. The third resonator C includes an electrode 20 formed on the lower surface of the second piezoelectric ceramic substrate 11b so as to be electrically connected to the electrode 13 by a conductive portion 26.
And an electrode 18 formed on the upper surface of the second ceramic substrate 11b so as to oppose the above. The electrode 18 is electrically connected to the electrode 12 of the first resonance section A by the conductive section 27.

Next, the effect of the present invention will be specifically described with reference to measurement data. FIG. 7 is a measurement circuit diagram. Samples 1 and 2 having the following characteristics were used as ceramic trap elements.

[Sample 1] First resonator A Resonant frequency Fr ₁ = 4.5 MHz Anti-resonant frequency Fa ₁ = 5.2 MHz Resonant resistance Rφ = 16Ω Capacitance Cd = 65PF Second resonator B Resonant frequency Fr ₂ = 4.5 MHz Resonance frequency Fa ₂ = 5.2MHz Resonance resistance Rφ = 16Ω Capacitance Cd = 65PF Third resonator C Resonance frequency Fr ₃ = 4.5MHz Anti-resonance frequency Fa ₃ = 4.5MHz Resonance resistance Rφ = 16Ω FIG. This is a trap characteristic diagram of Sample 1 in which the attenuation at 4.5 MHz is remarkably large at about 96 dB, and an extremely sharp shoulder characteristic is obtained.

[Sample 2] First resonator A Resonant frequency Fr ₁ = 4.5 MHz Anti-resonant frequency Fa ₁ = 5.2 MHz Resonant resistance Rφ = 16Ω Capacitance Cd = 65PF Second resonator B Resonant frequency Fr ₂ = 4.5 MHz resonance frequency Fa ₂ = 5.2 MHz resonance resistance R [phi] = 16ohms capacitance Cd = 65 pF third resonator C resonance frequency Fr ₃ = 4.5 MHz antiresonant frequency Fa ₃ = 4.55MHz resonance resistance R [phi] = 16ohms capacitance Cd = 50 pF FIG. 9 is a graph showing the trap characteristics. Also in this characteristic diagram, the attenuation at 4.5 MHz is remarkably large at about 80 dB, and an extremely sharp shoulder characteristic is obtained.

8 and FIG. 8 are obtained under the following conditions: Fr ₃ ≦ Fr ₁ , Fr ₂ Fa ₃ +0.2 (Fa ₃ −Fr ₃ ) ≧ Fr ₁ , Fr ₂ A high trap attenuation of 70 dB or more has been obtained.

Effect of the Invention As described above, according to the present invention, an external inductor is omitted, the number of components is reduced, and at the same time, an increase in attenuation in trap characteristics and an improvement in shoulder characteristics are simultaneously satisfied. An element can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view of a ceramic trap element according to the present invention, FIG. 2 is a bottom view thereof, FIG. 3 is a circuit symbol diagram thereof, FIG. 4 is a plan view of another embodiment, and FIG. also a bottom view thereof, FIG. 6 is a cross-sectional view in Figure 4 a ₁ -A ₁ line, FIG. 7 is Test circuit, Figure 8 and Figure 9 is trapped characteristics obtained by the measurement circuit of Figure 7 Fig. 10,
FIG. 11 is a plan view of a conventional ceramic trap element, FIG. 11 is a bottom view thereof, FIG. 12 is a circuit symbol diagram of the conventional ceramic trap element shown in FIGS. 10 and 11, and FIG. 13 is a trap characteristic. FIGS. 14 to 16 are trap characteristic diagrams when the inductance value of an external inductor is changed in a conventional ceramic trap element, and FIG. 17 is a characteristic measurement circuit diagram thereof. A: first resonator, B: second resonator C: third resonator 11: piezoelectric ceramic substrate 12 to 15, 18, 20 ... electrode 21: input terminal, 22 ... Common terminal 23 ... Output terminal

Claims (3)

(57) [Claims] 1. A ceramic trap element including a first resonator, a second resonator, and a third resonator, wherein the first resonator, the second resonator, and the second Each of the three resonators has a pair of electrodes formed on the front and back of a piezoelectric substrate, and the first resonator has one of the pair of electrodes connected to one input terminal. In the second resonator, one of the pair of electrodes is connected to the one output terminal, and the other of the pair of electrodes of the first resonator and the second resonator is The third resonator is inserted between the input terminal and the output terminal, and the pair of electrodes is connected to the input terminal and the output terminal, respectively. The resonance frequency of the first resonator is Fr1, and the anti-resonance frequency is F1.
a1, the resonance frequency of the second resonator is Fr2, the antiresonance frequency is Fa2, and the resonance frequency of the third resonator is Fr.
3. A ceramic trap element that satisfies Fr3 ≦ Fr1, Fr2Fr1, and Fr2 ≦ Fa3 + 0.2 (Fa3−Fr3) when the anti-resonance frequency is Fa3. 2. The ceramic trap element according to claim 1, wherein the first resonator, the second resonator, and the third resonator are formed on the same piezoelectric ceramic substrate. . 3. The first resonator and the second resonator are formed on a first piezoelectric ceramic substrate, and the third resonator is formed on the first piezoelectric ceramic substrate. The ceramic trap element according to claim 1, wherein the ceramic trap element is formed by using a laminated second piezoelectric ceramic substrate.