KR20030088991A - Surface acoustic wave filter - Google Patents

Abstract

PURPOSE: A surface acoustic wave filter is provided to reduce the dimension by reducing the size of a grounding region formed between a primary filter and an extended filter. CONSTITUTION: A grounding unit(41a) is formed between a first filter(40) and a second filter(50) and connected to an input IDT(InterDigital Transducer)(41) of the first filter(40). A signal transmitting unit(60) combines two signals divided by output IDTs, which are formed on both sides of the input IDT(41) of the first filter(40), to transmit the combined signal to an input IDT(51) of the second filter(50). An output unit is formed between the second filter(40) and a corner of a substrate(2) and connected to the output IDTs formed on the both sides of the input IDT(51) of the second filter(50) to output the filtered signal to outside.

Description

Surface acoustic wave filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave (SAW) filter. In particular, the SAW filter is reduced in size by reducing the ground area, and a terminal connected to the outside is formed outside the SAW filter to make an electrical connection with the outside. This is an easy SAW filter.

As shown in FIG. 1, the SAW filter according to the related art is formed in a pattern on the substrate 2, and includes a basic filter unit 10 for filtering and outputting a signal input from the outside, and the basic filter unit 10. It is composed of an expansion filter unit 20 is formed in a pattern on the substrate 2 so that the output signal of the input is filtered and output.

Here, the basic filter unit 10 may filter a first input interdigital transducer (IDT) 11 to which an external signal is input, and a signal input to the first input IDT 11. The first and second output IDTs 12 and 13 outputted afterwards, and the absorption unit 14 formed on both sides of the first and second output IDTs 12 and 13 to absorb reflected waves.

Meanwhile, the extended filter unit 20 may include second and third input IDTs 22 and 23 to which output signals of the first and second output IDTs 12 and 13 of the basic filter unit 10 are input, respectively. And a third output IDT 21 through which signals inputted to the second and third input IDTs 22 and 23 are filtered and output, and both sides of the second and third input IDTs 22 and 23. And second and third input IDTs 22 and 23, the first and second output IDTs being transmitted by a signal transmission unit 30 to allow a signal to be transmitted. Output signals of (12, 13) are input, respectively.

In addition, the ground filters 11a and 21b connected to the first input IDT 11 and the third output IDT 21 to prevent noise from occurring when filtering signals are respectively provided with the basic filter unit 10 and The third output IDT 21 is formed between the expansion filter unit 20 and an output unit 21a for outputting the filtered signal is provided in the third output IDT 21 and the substrate of the expansion filter unit 20. (2) is formed between the corners.

However, the SAW filter structure as described above has the ground portion formed on both the first and second filter portions, which increases the size of the SAW filter, and the ground when the probe is connected to the surface acoustic wave filter to measure the characteristics of the SAW filter. The operation is inefficient because the additional base amplifier is located between the basic amplifier and the expansion amplifier, and the ground part is located between the basic amplifier and the expansion amplifier, which makes the process complicated when using a wire bonding or flip chip process. have.

The present invention has been made to solve the above problems of the prior art, the object is to reduce the size of the surface acoustic wave filter by reducing the size of the area occupied by the ground portion formed between the basic filter portion and the expansion filter portion of the surface acoustic wave filter In addition, to provide a surface acoustic wave filter to simplify the process by forming an output portion formed on the extended filter portion outside the surface acoustic wave filter.

1 is a view showing the structure of a surface acoustic wave filter according to the prior art,

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

<Explanation of symbols on main parts of the drawings>

2: substrate 40: first filter portion

41: first input IDT41a: ground portion

42: first output IDT 43: second output IDT

50: second filter unit 51: second input IDT

52: third output IDT 53: fourth output IDT

60: signal transmission unit

According to a feature of the surface acoustic wave filter structure according to the present invention for solving the above problems, an input and output interdigital transducer (hereinafter referred to as IDT) for forming a pattern on a substrate and filtering a signal input from the outside. And a second filter part comprising an input and an output IDT formed in a pattern on the substrate to allow a signal filtered by the first filter part to be input and output to the outside after filtering. In the surface acoustic wave filter, the surface acoustic wave filter includes a ground portion formed between the first filter portion and the second filter portion and connected to an input IDT of the first filter portion, and an output IDT formed on both sides of an input IDT of the first filter portion. A signal transfer unit configured to allow a signal divided by the second unit to be combined and transmitted to an input IDT of the second filter unit; And an output unit formed between a filter unit and an edge of the substrate and connected to an output IDT formed on both sides of an input IDT of the second filter unit so that the filtered signal can be output to the outside.

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

As shown in FIG. 2, the SAW filter structure according to the present invention includes a first filter part 40 formed in a pattern on the substrate 2 and filtering and outputting a signal input from the outside, and the first filter part ( The second filter unit 50, which is filtered at 40), is filtered and output to the outside, and the signal is transmitted from the first filter unit 40 to the second filter unit 50. And a signal transmission unit 60 formed between the first and second filter units 40 and 50.

Here, the first filter unit 40 includes a first input IDT 41 to which a signal is input from the outside, and first and second output IDTs to which a signal input to the first input IDT 41 is filtered. (42, 43) and a first absorbing portion (44) formed on both sides of the first and second output IDTs (42, 43) to absorb reflected waves.

In addition, the first filter part 40 is connected to the first input IDT 41 of the first filter part 40, and between the first filter part 40 and the second filter part 50. And a ground portion 41a formed to allow noise of the signal input from the outside to be removed.

Meanwhile, the second filter unit 50 filters the second input IDT 51 to which the signal filtered by the first filter unit 40 is input, and the signal input to the second input IDT 51 is filtered. The third and fourth output IDTs 52 and 53 and the third and fourth output IDTs 52 and 53 and the edges of the substrate 2 to be outputted to be output. A plurality of output units 52a and 53a formed in the third and fourth output IDTs 52 and 53 and absorbing reflected waves formed on both sides of the third and fourth output IDTs 52 and 53. It consists of two absorption parts 54. As shown in FIG.

In this case, a signal output from the first and second output IDTs 42 and 43 of the first filter unit 40 between the first and second filter units 40 and 50 is transferred to the second filter unit 50. A signal transmission unit 60 is formed so as to be combined with the second input IDT 51.

As a result, in the SAW filter structure according to the present invention, since the ground area is reduced compared to the existing SAW filter structure, the size of the entire device is reduced, and an output portion through which the signal filtered by the SAW filter is output is located outside the SAW filter. Because it is formed, it can be easily connected to the external terminal, and this makes it easy to connect the probe when measuring the filter performance of the surface acoustic wave, thereby enabling accurate filter performance measurement.

The surface acoustic wave filter structure of the present invention configured as described above reduces the size of the entire device by reducing the ground area formed in the plurality of filter parts for filtering signals input from the outside, and is filtered by the plurality of filter parts. The terminal outputting the signal to the outside of the surface acoustic wave filter can be formed to facilitate the flip chip process or wire bonding process, and the probe can be easily measured when measuring the performance of the surface acoustic wave filter. There is.

Claims (2)

A first filter unit including an input and output interdigital transducer (hereinafter referred to as IDT) which is formed in a pattern on a substrate and filters a signal input from the outside, and a signal filtered by the first filter unit is input In the surface acoustic wave filter comprising a second filter portion consisting of an input and an output IDT formed in a pattern on the substrate to be output to the outside after filtering, The surface acoustic wave filter is a signal divided by a ground part formed between the first filter part and the second filter part and connected to an input IDT of the first filter part, and an output IDT formed on both sides of the input IDT of the first filter part. Is coupled between an input IDT of the second filter unit and an output IDT, and is connected between the second filter unit and an edge of the substrate and connected to an output IDT formed on both sides of an input IDT of the second filter unit to be filtered. Surface acoustic wave filter characterized in that it further comprises an output unit for outputting a signal to the outside. The method of claim 1, Surface acoustic wave filters, characterized in that the first absorbing portion and the second absorbing portion is formed on both sides of the output IDT of the first filter portion and the output IDT of the second filter portion to absorb the reflected wave.