KR100380941B1 - Absorption structure of surface acoustic wave filter - Google Patents

Abstract

The present invention provides a surface acoustic wave filter capable of improving the performance of the filter by minimizing the reflected wave reflected to the IDT side by reabsorbing the reflected wave which is not absorbed by the primary absorbent and absorbed by the secondary absorbent by using the absorbent as a double structure. It is for providing a sound absorbing structure.

The sound absorbing structure of the surface acoustic wave filter includes an input IDT for inputting an external electrical signal and converting it into a mechanical signal, an output IDT for converting the mechanical signal back to an electrical signal, and a ground function disposed between the input IDT and the output IDT. In the sound absorbing structure of the surface acoustic wave filter composed of a ground bar for absorbing the reflected wave reflected from the input and output IDT, the sound absorbing agent is disposed on both sides of the input and output IDT, respectively, and the input and output IDT array direction and angle The first absorbent is formed to be inclined to absorb the reflected waves reflected from both side IDT, and the second absorbent disposed below the both side IDT and reabsorbs the reflected wave reflected from the first absorber.

Description

Absorption structure of surface acoustic wave filter

The present invention relates to a sound absorbing structure of a surface acoustic wave filter, and more particularly, to a sound absorbing structure of a surface acoustic wave that can improve the performance of a filter by improving the absorption rate of reflected waves reflected from an inter digital transducer. will be.

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.

The SAW filter is a ceramic container that protects a semiconductor device or a function, and is formed in a package form that protects an internal circuit from a harmful environment and provides a means for dissipating heat generated therein and connecting it to the outside.

The SAW filter package is formed by a surface mount production technology, and is suitably used for supporting a wide band transmission such as a CDMA cellular telephone, a wireless LAN, and an image device.

For example, interdigital transducers (hereinafter referred to as IDTs) are installed at the input and output stages to convert electrical signals to mechanical signals when they are recognized during the intermediate frequency filter process in mobile communications components such as PCS or CDMA. When an electrical signal is applied to the piezoelectric object, it is converted into a mechanical signal, and then the output is converted into an electrical signal and outputted, thereby passing a desired frequency band and blocking the remaining band.

1 is a block diagram showing a sound absorbing structure of the SAW filter according to the prior art.

The SAW filter includes an input IDT 102 that recognizes an external electrical signal and converts it into a mechanical signal, an output IDT 104 that converts a filtered mechanical signal into an electrical signal so that only a desired frequency band passes, and both sides of the SAW filter. A ground bar 106 disposed between IDTs and performing a grounding operation, and reflected waves reflected from input and output IDTs 104 mounted on both sides of the input IDTs 102 and outputs IDTs 104. It is made of a sound absorbing agent 108 that absorbs and prevents the reflection back to both sides IDT.

As such, the wave reflected by the internal IDT of the SAW filter is absorbed by the sound absorbing agent 108 to improve the performance of the filter.

However, since the sound absorbing structure of the SAW filter according to the prior art as described above is provided on both sides of the input IDTD and the output IDT respectively, the sound absorbing agent is not absorbed by all the reflected waves in the sound absorbing agent, but rather by the discontinuous material called the sound absorbing agent. There is a reflected wave again. The reflected wave reflected by this suction agent is reflected back to the IDT side, which causes a problem of degrading the performance of the filter.

The present invention has been made to solve the above problems, and an object of the present invention is to absorb the reflected wave reflected by the secondary absorbent, which is not absorbed by the primary sound absorbing agent with a double structure of the sound absorbing agent, reflected by the IDT side By minimizing this, to provide a sound absorbing structure of the surface acoustic wave filter that can improve the performance of the filter.

1 is a block diagram showing a sound absorbing structure of the surface acoustic wave filter according to the prior art,

2 is a block diagram showing a sound absorbing structure of the surface acoustic wave filter according to the present invention.

<Explanation of symbols for the main parts of the drawings>

2: input IDT 4: output IDT

6: ground bar 8: the first sound absorbing agent

10: second sound absorbing agent

Sound absorbing structure of the surface acoustic wave filter according to the present invention for realizing the above object is an input IDT for converting an external electrical signal into a mechanical signal, an output IDT for converting the mechanical signal back to an electrical signal, and the input A sound absorbing structure of a surface acoustic wave filter comprising a ground bar disposed between an IDT and an output IDT to perform a grounding function, and a sound absorbing agent absorbing reflected waves reflected from the input and output IDTs. Arranged on both sides and arranged in a direction and an angle of the input and output IDTs; The first absorbent is formed to be inclined to absorb the reflected waves reflected from both side IDT, and the second absorbent disposed under the both side IDT and the second absorbent reabsorbs the reflected wave reflected from the first absorber.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a block diagram showing the structure of the suction agent of the SAW filter according to the present invention.

The SAW filter has an input IDT (2) for inputting an external electrical signal and converting it into a mechanical signal, and an output IDT (4) for converting a filtered mechanical signal back to an electrical signal so that only a desired frequency band passes. A ground bar 6 disposed between the IDT 2 and the output IDT 4 to perform a grounding operation, and a first sound absorbing agent absorbing the reflected waves reflected from the input and output IDTs 2 and 4; 8) and a second absorbent 10 or the like which reabsorbs the reflected wave reflected by the first absorbent 8.

The first sound absorbing agent 8 is disposed on the front side of the input IDT 2 and is disposed on the rear side of the output IDT 4 to absorb reflected waves reflected from both IDTs 2, 4. The first sound absorbing material 8 is not absorbed due to the discontinuity of the sound absorbing material, and the reflected waves which are not reflected back to the two IDTs 2 and 4 are prevented from being reflected back to both IDTs 2 and 4 so that the first sound absorbing agent 8 is arranged at a predetermined angle with the arrangement direction of the two IDTs 2 and 4. ( ) Is installed inclined.

In particular, the first sound absorbing agent (8) and the direction of the arrangement of the two IDT (2,4) The second absorbent 10 is for reabsorbing the reflected wave reflected from the first absorbent 8, and is provided to the input IDT 2 and the output IDT 4 under the filter. It is arranged horizontally with the traveling direction of the reflected wave over. The second sound absorbing material 10 is arranged side by side at a predetermined interval in the lower side of the two IDT (2, 4) in the form of a thread, the first sound absorbing material (8) and a predetermined angle with the second sound absorbing material (10) such as arrow P ( Absorb the reflected wave back to).

In addition, the second sound absorbing agent 10 is formed to be spaced apart a predetermined distance so as not to penetrate the input IDT (2), the output IDT (4) and the ground bar 6. The action of the SAW filter according to the present invention This is described below.

Reflected waves reflected from both the input IDT 2 and the output IDT 4 on both sides are absorbed by the first defect agent 8. At this time, it is not absorbed by the discontinuous nature of the first absorbent 8 and is reflected again, the first absorbent 8 is a certain angle ( Since the reflection wave reflected from the first sound absorbing agent 8 is not reflected to both sides of the IDT (2, 4) side, it is installed at an angle with the second sound absorbing agent 10. ) And reflected. In this way, the reflected waves re-reflected by the first absorbent 8 may be absorbed again by the second absorbent 10 and minimize the reflected waves finally reflected to both IDTs 2 and 4.

Therefore, the sound absorbing structure of the surface acoustic wave filter according to the present invention constructed and acted as described above is arranged at both sides of both side IDTs and at a predetermined angle ( The first absorbent is disposed obliquely, and the second absorbent is disposed below both IDTs in a direction parallel to the traveling direction of the reflected wave, thereby preventing the reflected waves reflected from the first absorbent from being reflected back to the both IDTs. By re-absorbing the reflected reflected wave in the second sound absorbing agent, there is an advantage in that the reflected wave reflected from both IDTs may be absorbed twice to improve the performance of the filter.

Claims (3)

An input IDT for inputting an external electrical signal to convert it into a mechanical signal; An output IDT for converting the mechanical signal back into an electrical signal; A ground bar disposed between the input IDT and the output IDT to perform a grounding function; In the acoustic absorber structure of the surface acoustic wave filter composed of a sound absorbing agent absorbing the reflected wave reflected from the input and output IDT, the sound absorbing agent is disposed on both sides of the input and output IDT, respectively, and the arrangement direction and constant of the input and output IDT Angle( A first absorbent installed at an inclined angle to absorb reflected waves reflected from both IDTs; And a second sound absorbing agent disposed under both side IDTs to re-absorb reflected waves reflected by the first sound absorbing agent. The method of claim 1, The first sound absorbing agent and the array direction of the input and output IDT The acoustic absorber structure of the surface acoustic wave filter, characterized in that the reflection wave is prevented from being absorbed by the first sound absorbing agent due to the discontinuity of the sound absorbing agent is reflected back to both sides IDT. The method of claim 1, The second acoustic absorber is formed in the shape of a screw thread disposed horizontally with the direction of travel of the reflected wave on the lower side of the input IDT and the output IDT to facilitate the absorption of the reflected wave reflected from the first sound absorber. Sound absorbent structure.