JPS61202510A - Comb-line filter - Google Patents

Abstract

PURPOSE:To save the cost and man-hour and to attain miniaturization by adhering an input piezoelectric element onto an output piezoelectric element and providing it to an input/output slope of an ultrasonic wave delay medium so as to omit the use of an impedance element. CONSTITUTION:The input piezoelectric element 1 is adhered overlappinly onto the output piezoelectric element 2 and provided to the input/output slope of the ultrasonic wave delay medium 3. For example, an earth electrode is provided to the input/output slope of the ultrasonic wave delay medium 3, the output piezoelectric element 2 having an output electrode on the surface is provided thereupon, the input piezoelectric element 1 having an electrode on both faces is adhered overlappingly, the input electrode of the input piezoelectric element 1 and a terminal 4' are connected by a lead 5, the output electrode of the output piezoelectric element 2 and the terminal 4' are connected by a lead 6 and the earth electrode and a terminal 4'' are connected by a lead 7. Thus, an impedance element is saved, the cost and man-hour with it are saved and the comb-line filter is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a comb filter in which a pass band and an attenuation band are alternately repeated at a constant wave number interval with frequency characteristics, and is particularly useful for removing dot interference in color television receivers. The present invention relates to a comb filter used for improving the image quality of video equipment such as cross color removal of VTRs and VTRs.

2. Description of the Related Art The main parts of a conventional comb filter of this type are shown in FIG. As shown in FIG. 2, in a conventional comb filter, an input piezoelectric element 1 that converts an electrical signal into mechanical vibration and an output piezoelectric element 2 that converts mechanical vibration into an electrical signal are connected to the input and output slopes of an ultrasonic delay medium 3. are installed in parallel. A ground electrode (not shown) is provided on the surface where these input/output piezoelectric elements 1 and 2 are attached to the ultrasonic delay medium 3, and electrodes for input/output are also provided on the surfaces of the input/output piezoelectric elements 1 and 2, respectively. (not shown) is provided.

The input/output electrodes of the input/output piezoelectric elements 1 and 2 described above have terminals 4 and leads 1 for electrical connection with the outside.
a5 and 6, and the ground electrode is also connected to another terminal 4 by lead s7. In such a comb filter, the leads s5 and 6 are coupled through an impedance element 8 such as a resistor. In FIG. 2, 9 is a case for keeping the ultrasonic delay medium 3 and the terminal 4 constant.

The configuration of such a comb filter is shown in an electrical circuit diagram in FIG. At k in Figure 3, an electrical signal is input from terminal A, impedance element 8 and ultrasonic delay element 1.
o and is synthesized again at terminal B. Ultrasonic delay element 1
Since the signal transmitted through the impedance element 8 is delayed by a certain period of time than the signal transmitted through the impedance element 8, a phase difference occurs between the signal transmitted through the impedance element 8 and the signal transmitted through the impedance element 8.

Signals at frequencies with a phase difference of 18oO are added together at terminal B and are attenuated, while signals at frequencies with a phase difference of 0 degrees are strengthened at terminal B. The frequency characteristic is such that an attenuation region appears at a frequency interval expressed by the reciprocal of the delay time of the cooled ultrasonic delay element 10.

Problems to be Solved by the Invention In the conventional comb filter described above, after forming the ultrasonic delay element, the impedance element 8 is connected to the input/output leads m5 and 6 by soldering. The cost of the impedance element 8 and the man-hours for attaching it are added to the manufacturing cost of the comb filter, which increases the cost, and the comb filter has the disadvantage that the shape of the comb filter becomes larger at least by the volume occupied by the impedance element 8. Ta.

Accordingly, an object of the present invention is to provide a comb-shaped filter that can omit the use of the impedance element, thereby reducing costs and man-hours, and is further miniaturized by eliminating the space occupied by the impedance element.

Means for Solving the Problems The present invention provides a comb filter using an ultrasonic delay line as described above, in which an input piezoelectric element is laminated on top of an output piezoelectric element to form an input/output slope of the ultrasonic delay medium. It is located in the comb-shaped filter installed in the section.

According to the present invention, with the above-described configuration, an input signal is converted into mechanical vibration by the input piezoelectric element, and the vibration is transmitted to the output piezoelectric element laminated below, and a part of the vibration is is converted into an electrical signal by the output piezoelectric element. This is called a through signal. Vibrations transmitted to the output piezoelectric element that are not converted into electrical signals are transmitted to the ultrasonic delay medium, reach the output piezoelectric element after a certain fixed time delay, and are converted into electrical signals there. When the phase difference between this delayed signal and the through signal is 180°, the through signal and the delayed signal cancel each other out at the output piezoelectric element and are attenuated, and when the phase difference is 0°, the delayed signal and the through signal are attenuated at the output piezoelectric element. They strengthen each other and become an output signal.

Example FIG. 1 shows an example of a comb filter according to the present invention.

In FIG. 1, according to the present invention, a ground electrode (not shown) is provided on the input/output slope portion of the ultrasonic delay medium 3, and an output piezoelectric element 2 having an output electrode (not shown) on its surface is provided thereon. Then, the input piezoelectric elements 1 having electrodes on both sides are laminated together, the input electrodes (not shown) of the input piezoelectric elements 1 and the terminals 4'' are connected with lead wires 5, and the output electrodes of the output piezoelectric elements 2 ( (not shown) and a terminal 41 are connected by a lead wire 6, and a ground electrode (not shown) and a terminal 41 are connected by a lead wire 7. In FIG.
This is a case for fixing ", 4', 4".

According to the present invention, by laminating the input piezoelectric element 1 and the output piezoelectric element 2 in an overlapping manner, the comb-shaped filter can be formed without using the impedance element 6 (see FIGS. 2 and 3) as described above. Can be configured.

Effects of the Invention According to the present invention, in a comb-shaped filter, it is possible to omit a conventional impedance element, thereby reducing costs and man-hours, and making it possible to downsize the comb-shaped filter.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a comb filter according to the present invention, FIG. 2 is a diagram showing a conventional comb filter, and FIG. 3 is a circuit diagram of the conventional comb filter. 1 is an input piezoelectric element, 2 is an output piezoelectric element, 3 is an ultrasonic delay medium, 4, 4", 4", 41" are terminals, 5, 6° 7 are lead wires, 8 is an impedance element, and 9 is a case.

Claims (1)

[Claims] 1. In a comb filter using an ultrasonic delay line,
A comb-shaped filter characterized in that an input piezoelectric element is laminated on top of an output piezoelectric element and provided on the input/output slope of an ultrasonic delay medium.