JPS60114011A - Comb line filter - Google Patents

Abstract

PURPOSE:To attain low cost and small size by using input/output transducers of an ultrasonic wave delay line as one, splitting electrodes at front and rear sides of the transducer into two at a part not overlapped in the broadwise direction and arranging the input and output terminals to an electrode pair having frong and rear counter parts respectively. CONSTITUTION:Parts of an input/output transducer 11 corresponding to electrodes 12 and 16 act as a function transmitting and receiving an ultrasonic wave propagated in a delay medium 21 as the input and output transducers and a counter part 18 couples input and output electrodes 13, 15 in terms of capacitance. Thus, an input signal is converted into an ultrasonic wave, which is propagated in the delay medium 12 and converted again into an electric signal, outputted with a prescribed time of delay and a bypass signal is also outputted by the capacitive coupling, a comb line filter acting like that is obtained. The electrode 13 is deleted or added by a part of a separation slit 14 so as to change the static capacitance between the input and output electrodes, and the bypass signal level is adjusted so as to be made coincident with a delay signal level.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a comb filter used in video equipment.

Conventional configurations and their problems In recent years, video equipment such as video tape recorders and color television receivers have become smaller and cheaper. It is widely used in 17 components that promote the miniaturization and non-adjustment of video equipment. A conventional comb filter will be described below with reference to the drawings. FIG. 1 shows the configuration of a general comb filter.

Reference numeral 1 denotes an ultrasonic delay line, which delays the entire input signal by a certain period of time.

Reference numeral 2 denotes an impedance element for obtaining a bypass signal, and the impedance value is selected so that a bypass signal having the same level as the delayed signal can be obtained. In this way, the output signal B obtained by adding the delayed signal and the bypass signal exhibits a comb filter characteristic in which a pass band and an attenuation band appear alternately, and the ultrasonic delay line 1 and the impedance element 2 are integrated. Type 3 is called a comb filter. Here, one more resistor or capacitor is used as the impedance element 2.

Figure 2 shows the structure of a conventional comb filter.
Ultrasonic delay line 6 and input lead 6 located above. The output lead wires 7 are connected to each other, and these lead wires 6.7 are connected to the input terminals 8. Output terminal 9
Connect to each.

Further, an impedance element 10 is connected between the input terminal 8 and the output terminal 9 with a solder or the like, and the whole is covered with a case (not shown).

However, in the above configuration, compared to the conventional ultrasonic delay line assembly, the work of connecting the impedance element 1o is added, the work efficiency is reduced, and the price is increased, and the shape is changed by the addition of the impedance element 10. OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a small-sized comb filter at a low price.

Structure of the Invention In order to achieve this object, the comb filter of the present invention has a single input/output transducer for an ultrasonic delay line, and the front and back electrodes of this transducer are formed in portions that do not overlap in the thickness direction. 2
By dividing the circuit and arranging the input terminal and the output terminal in pairs of electrodes having opposing portions on the front and back sides, a bypass signal is obtained along with a delayed signal by the capacitance of the opposing portions. Here, in order to obtain a bypass signal of the same level as the delayed signal, it is also possible to adjust the capacitance by removing or adding electrodes to the area of the opposing portion. As a result, since the impedance element is integrated with the input/output converter, it is possible to improve work efficiency by removing the work of connecting the impedance element, and to make it possible to reduce the size.
In addition, the impedance value can be easily selected by adjusting the area of the facing electrode, making it possible to reduce the cost.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. As shown in the figure, electrodes 12 and 13 on the front side of the input/output transducer 11 made of piezoelectric elements are divided by a separation band 14, and electrodes 15 and 16 on the back side are divided into separation bands 17. Since the separation bands 16 and 17 are provided in portions that do not overlap in the thickness direction, they have opposing portions 18. Here, the electrode 16 on the back side of the input/output electrode space 11 is connected to an electrode 19 provided on the delay medium 21, and similarly, the electrode 16 is connected to the electrode 2o and led out to the outside.

The electrode 13 and electrode 16 having opposing portions are each connected to an input/output terminal, and the other electrode 12 and electrode 16 are connected to a ground terminal. With this configuration, the portions of the input/output transducer 11 corresponding to the electrodes 12 and 16 function as input and output transducers to transmit and receive ultrasonic waves propagating through the delay medium 21, and the opposing portion 18 functions as an input and output transducer. Input and output electrodes 13 and 16 are capacitively coupled. From this, the input signal is converted into an ultrasonic wave, transmitted through the delay medium 21, converted back to an electric signal, and output after a certain time delay while being capacitively coupled. A bypass signal is also output, and a comb-shaped filter can be obtained.
The capacitance between the input and output electrodes can be changed by deleting or adding the signal level to the delay signal level. According to the comb-shaped filter of the present invention configured as above, the impedance element that was attached to the conventional input/output terminal by the inverter attachment is no longer necessary, and the workability is improved and the cost can be realized. At the same time, downsizing can be realized. In addition, the impedance value can be easily adjusted and the cost can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a comb filter, FIG. 2 is a perspective view of a main part of an example of a conventional comb filter, and FIG. 3 is a perspective view of a main part of an embodiment of a comb filter according to the present invention. It is a diagram. 11... Input/output converter, 12, 13, 15゜1
6...Transducer electrode, 14.17...
Electrode separation band, 18...Input/output electrode opposing part, 19
．． -20... Electrode on delay medium -21...
...delay medium. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 2 Figure 3

Claims (1)

[Claims] It comprises an ultrasonic delay medium and a single input and output transducer bonded to one side of the ultrasonic delay medium, and the front and back electrodes of this transducer overlap in the thickness direction. It is divided into two parts by the part that does not exist. A comb-shaped filter in which an input terminal and an output terminal are arranged in a pair of electrodes each having a front and back facing portion.