KR100451080B1 - Resonator Type Surface Acoustic Wave Filter - Google Patents

Abstract

The present invention relates to a resonant surface acoustic wave filter, wherein the input and output electrodes are meshed with corresponding sides facing each other so that the size of the overall filter chip can be reduced while maintaining the same distance between the input and output electrodes of the resonant surface acoustic wave filter. Each of the grooves in the shape of a square wave is formed so that the inter-digital transducer (hereinafter referred to as an IDT) part is spaced apart from the groove to form a pattern to reduce the size of the resonant surface acoustic wave filter, particularly the IF surface acoustic wave filter. It has the effect of making it possible.

Description

Resonator Type Surface Acoustic Wave Filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonant surface acoustic wave filter, and more particularly, to a resonant surface acoustic wave filter capable of reducing the size of a chip when designing a filter and miniaturizing the overall filter.

In general, surface acoustic wave (SAW) represents a state of the wave transmitted along the surface of the substrate and has a characteristic of rapidly attenuating in the depth direction. Surface acoustic wave (SAW) filters apply these features as frequency selective devices.

In other words, the SAW device temporarily forms a metal electrode on a highly insulating substrate and applies a piezoelectric twist to the substrate surface. This action causes a physical wave. Since the wave speed passing through the SAW device surface is slower than electromagnetic waves, it is used as a filter to temporarily delay an electric signal or pass only a specific frequency signal.

For example, an inter-digital transducer (IDT), which converts an electrical signal into a mechanical signal when it is recognized during the intermediate frequency filter process, is installed at the input and output terminals, respectively. When a signal is applied, it is converted into a mechanical signal, and the output is converted into an electrical signal and output, thereby passing the desired frequency band and blocking the remaining band.

1 illustrates a pattern formed on a general resonant surface acoustic wave filter chip. That is, the IDT unit 2 for forming a pattern on the chip substrate 1, the input / output electrodes 3a and 3b for inputting and outputting signals to and from the IDT unit 2, and both sides of the IDT unit 2, respectively. And a reflector 4 formed to cause resonance in the chip 1.

However, the resonant surface acoustic wave filter chip as described above has a problem in that it is difficult to miniaturize the filter size because the size of the input / output electrode 3 cannot be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide an overall chip by forming grooves corresponding to the input / output electrodes for inputting and outputting signals to the IDT portion of the surface acoustic wave filter when designing a resonance surface acoustic wave filter. To provide a resonant surface acoustic wave filter capable of miniaturizing the size of the.

1 is a view showing a pattern of a conventional resonant surface acoustic wave filter chip,

2 is a diagram illustrating a pattern of a resonant surface acoustic wave filter chip according to the present invention.

<Description of Symbols Regarding Main Parts of the Drawing> 11: IDT Parts 12a and 12b: Input and Output Electrodes

According to a characteristic of the resonant surface acoustic wave filter according to the present invention for solving the above problems, an IDT unit formed on a substrate to filter and output an input signal, and the IDT unit to input and output a signal to the IDT unit. In the resonant surface acoustic wave filter including input and output electrodes formed parallel to the upper and lower sides of the IDT portion along the direction in which the signal is transmitted, the input and output electrodes are grooves are formed in the shape that the input electrode and the output electrode are engaged with each other. The IDT unit is formed in a pattern such that the grooved input / output electrode is spaced apart from each other.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the resonant surface acoustic wave filter according to the present invention forms an pattern on the substrate 10 of the chip so that an input signal is filtered and an IDT unit 11 of the IDT unit 11. Input and output electrodes 12a and 12b formed in parallel with the direction in which the signal is transmitted from the IDT unit on the upper and lower sides, and the reflection unit 13 reflecting the signal transmitted from the IDT unit to both sides of the IDT unit 11. It consists of.

Here, the input / output electrodes 12a and 12b and the IDT unit 11 are electrically connected to each other, and the input / output electrode 12 and the IDT unit 11 are configured to transmit and receive mutual electrical signals.

In addition, the reflector 13 causes a signal transmitted between the IDT unit 11 from both sides of the IDT unit 11 to be reflected from both sides, and the signal is repeatedly reflected by the reflector 13. As the resonance occurs, the resonance type surface acoustic wave chip operates as a filter.

That is, according to the resonance principle, only the filtered signal among the signals input through the input electrode 12a to the IDT unit 11 is output to the outside through the output electrode 12b.

The above operation principle is a general operation principle of the resonant surface acoustic wave filter, and in the case of the resonant filter using the resonant principle, it is installed in a device using a filter having a high frequency and a wide pass band.

In particular, in the present invention, as shown in the figure, the input and output electrodes 12a and 12b are formed to form a square wave groove so as to engage with each other facing each other, so that the formed groove and the IDT portion 11 are spaced apart from each other.

Accordingly, the grooves formed in the input / output electrodes 12a and 12b have inverted shapes. The IDT unit 11 is electrically connected to the protrusions corresponding to the grooves of the input / output electrodes 12a and 12b. By being connected, the distance A between the input and output electrodes 12a and 12b may be reduced.

Here, the distance A between the input and output electrodes 12a and 12b is an important factor in determining the pass band of the filter. Accordingly, in the case of the conventional resonant surface acoustic wave filter, even if the distance A is reduced, the filter can be miniaturized. It was not true.

In the present invention, the grooves are formed in the input / output electrodes 12a and 12b, and the grooved portions are formed such that the ends of the IDT portions are spaced apart from each other, so that the distance A between the input and output electrodes 12a and 12b is conventionally resonated. At the same time as the type filter, only the size of the resonant surface acoustic wave filter chip can be reduced.

Therefore, the size of the resonant surface acoustic wave filter chip according to the present invention can be miniaturized without changing the passband characteristics.

The resonant small acoustic wave filter of the present invention configured as described above can reduce the size of the overall filter chip while maintaining the same distance between the input and output electrodes of the IDT unit determining the pass band, which is an important characteristic of the resonant surface acoustic wave filter. Since the input / output electrode forms a groove having a square wave shape on a corresponding side facing each other and is patterned to be spaced apart from the groove, the size of the resonant surface acoustic wave filter, especially IF surface acoustic wave filter, can be reduced.

Claims (1)

An IDT unit formed on a substrate to filter and output an input signal, and an input / output electrode formed parallel to the upper and lower sides of the IDT unit along a direction in which the signal is transmitted from the IDT unit to input and output a signal to the IDT unit. In the resonance type surface acoustic wave filter, The input and output electrodes are each formed with grooves in the shape that the input electrode and the output electrode are engaged with each other, The IDT unit is patterned so that the grooved input and output electrodes are spaced apart from each other, and the resonant surface acoustic wave filter is configured to be electrically connected to the protrusions corresponding to the grooves of each of the input and output electrodes.