KR100315750B1 - The saw filter having a member for eliminating RF feedthrough signals - Google Patents

Abstract

The present invention relates to a surface acoustic wave filter, and more particularly, to a surface acoustic wave generated by an RF feedthrough signal which is applied to an input pad of a surface acoustic wave filter and is transmitted directly to an output pad without passing through the surface acoustic wave member. The present invention relates to a surface acoustic wave filter having a structure for preventing degradation of the stopband characteristics of the filter.

The surface acoustic wave filter provided with the feed-throw removing member of the present invention includes an input IDT portion, a ground bar, and an output IDT portion, and has a plurality of pads electrically connected to each other by a bonding wire on a side thereof, and has a length at a central portion thereof. In the surface acoustic wave filter package in which the SAW member is installed in the direction and the lead is blocked to the outside on the upper side, the ground pads at the opposite positions among the pads are connected by using bonding wires separated from each other to feed through signals. It is characterized by blocking the. According to another feature of the present invention, a pair of ground pads adjacent to the ground bar and opposed to each other in the pad are connected to each other by a metal bar to block the feed through signal. According to still another aspect of the present invention, a dielectric resin material is applied to an inner surface of a lid positioned on an upper side of the surface acoustic wave filter package to block the package from the outside to block the feed through signal.

Description

Surface acoustic wave filter with feed-throw removal element {The saw filter having a member for eliminating RF feedthrough signals}

The present invention relates to a surface acoustic wave filter, and more particularly, to a surface acoustic wave generated by an RF feedthrough signal which is applied to an input pad of a surface acoustic wave filter and is transmitted directly to an output pad without passing through the surface acoustic wave member. The present invention relates to a surface acoustic wave filter having a structure for preventing degradation of the stopband characteristics of the filter.

A surface acoustic wave filter (also called a SAW filter) is a filter which obtains the necessary frequency characteristics by changing the structure and position of a foot-shaped electrode converter provided on a substrate or thin film having piezoelectric characteristics as a transmission medium for surface acoustic waves.

The detailed structure of the surface acoustic wave filter 10 will be described below with reference to FIG. 1. The surface acoustic wave filter 10 generally includes an input IDT portion, a ground bar, and an output IDT portion, and includes a plurality of pads 14, 16, 18, which are electrically connected to each other by a bonding wire 34 on the side in the longitudinal direction. 20, 22, 24, 26, 28, 30, 32 are formed, the SAW member 12 is installed in the longitudinal direction in the center portion, the upper side is provided with a lid 36 covering the entire surface is cut off from the outside Has

In the above, IDT stands for Inter Digital Transducer, and is a plurality of thin band-shaped electrode groups disposed in the shape of a foot on the entire surface of the piezoelectric body and has an electrode structure for generating or receiving surface acoustic waves. Means transducers arranged in crossed state. The pad 14 is used to input a signal from the outside of the input IDT part, and the pad 32 is used to output a signal to the output IDT part. The structure shown in FIG. 1 shows a state in which a surface acoustic wave filter is placed in a package and even wire bonded.

In the conventional surface acoustic wave filter having the above-described configuration, there is a problem in that a feed through signal is generated that deteriorates the characteristics of the stop band at the time of signal input. 2 and 3 illustrate a signal generation state when a signal is applied to the surface acoustic wave filter 10 of FIG. 1. Here, Vin is a continuous wave of constant amplitude and vibration, Z _L is a load impedance, and an arrow is a signal emitted from the input pad 14 as a feedthrough signal.

When an appropriate signal is applied to the pad 14 located in the input IDT of FIG. 1, the surface acoustic wave member 12 operates as a filter passing only a desired signal. At this time, a part of the signal input to the pad 14 of the surface acoustic wave filter 10 is radiated to the air without passing through the surface acoustic wave member 12 to generate a signal that is excited to the output pad 32. This is indicated by the arrow in FIG.

As a result, the excited signal affects the characteristics of the surface acoustic wave filter because it acts as a noise as a signal of an unwanted band. That is, the stopband characteristic of the surface acoustic wave filter 10 is deteriorated, resulting in a failure to remove unwanted signals.

The present invention has been made to solve the above problems, the object of the present invention is applied to the input pad of the surface acoustic wave filter RF signal throw signal that is transmitted directly to the output pad without passing through the surface acoustic wave member The present invention provides a surface acoustic wave filter for preventing degradation of stopband characteristics of the surface acoustic wave filter generated by the method.

Surface acoustic wave filter provided with a feed throw removal member of the present invention for achieving the above object is composed of an input IDT portion, a ground bar, an output IDT portion, a plurality of pads are electrically connected to the side by a bonding wire A surface acoustic wave filter package having a SAW member disposed in a longitudinal direction at a central portion thereof and positioned at an upper side thereof so as to block a lid from the outside, wherein the ground pads at opposite positions of the pads are separated from each other using bonding wires. It is characterized by blocking the feed through signal by connecting. According to another feature of the present invention, a pair of ground pads adjacent to the ground bar and opposed to each other in the pad are connected to each other by a metal bar to block the feed through signal. According to still another aspect of the present invention, a dielectric resin material is applied to an inner surface of a lid positioned on an upper side of the surface acoustic wave filter package to block the package from the outside to block the feed through signal.

1 is a plan view showing the internal structure of a conventional surface acoustic wave filter;

2 is a signal generation diagram in a state where a signal is applied to the surface acoustic wave filter of FIG.

3 is a side cross-sectional view of the surface acoustic wave filter of FIG. 2;

4 is a plan view of a surface acoustic wave filter connected to a bonding wire according to the present invention;

5 is a plan view of a surface acoustic wave filter connected to a metal bar according to the present invention;

6 is a side sectional view of a surface acoustic wave filter coated with a resin according to the present invention.

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

10: surface acoustic wave filter 12: surface acoustic wave member

14,16,18,20,22,24,26,28,30,32: pad

34: bonding wire 36: lid

38: feed through signal 40: bonding wire

42: metal bar 44: dielectric resin

Hereinafter, the surface acoustic wave filter in which the feed throw removing member of the present invention is installed will be described in detail with reference to the accompanying drawings.

The present invention is to improve the stopband characteristics of the surface acoustic wave filter by removing a feed through signal by adding a separate member inside the surface acoustic wave filter.

Figure 4 is an embodiment of a surface acoustic wave filter according to the present invention.

This is characterized in that, as shown in the figure, ground pads in opposite positions of the pads are connected by using bonding wires separated from each other. That is, the pads 16, 18, 20, 22, 24, 26, 28, and 30, except for the pads 14 and 32, which are used for input and output of a conventional signal, are separated from each other using a plurality of bonding wires 40. Connected.

The bonding wires 40 are essentially the same as the bonding wires 34 that were used first. For convenience of description, reference numerals other than the bonding wire 40 are omitted, and the reference numerals that are omitted coincide with the reference numerals of FIG. 1. In this case, the pads electrically connected to each other by the bonding wires 40 are not pads adjacent to the side surfaces, but pads that are opposite to each other. The bonding wires 40 are thus grounded. As such, the bonding wires 40 are intersected so that the feed through signal is interrupted in the process.

When the signal Vin is applied to the pad 14 of the input IDT unit while the plurality of bonding wires 40 are connected as described above, a feedthrough signal is generated as in the related art. The generated feed through signal proceeds in the direction of the arrow as in the prior art. At this time, since the bonding wire 40 is grounded while blocking the middle, the piece throw signals reaching the bonding wire 40 are bonded wire 40. Flows into the ground point.

Therefore, since the feed through signal is almost eliminated while the first, second, and third bonding wires 40 pass in sequence, the signal flowing into the output pad side and causing excitation is eliminated. Since the feed through signal is removed as described above, the stopband characteristic is improved compared to the conventional surface acoustic wave filter.

As another embodiment of the present invention, referring to FIG. 5, pads of a pair of opposing positions positioned at the center of the surface acoustic wave filter 10 package are connected to the metal bars 42. The metal bar 42 is grounded as described above. As such, the metal bar 42 is installed across the surface acoustic wave member 12 to block the feedthrough signal.

When the signal Vin is applied to the pad 14 of the input IDT unit while the metal bar 42 is connected as described above, a feed through signal is generated as in the related art. The generated feed-through signal proceeds in the direction of the arrow as in the prior art. At this time, since the metal bar 42 is grounded, the feed through signal flows to the ground point along the metal bar 42. Since the metal bar 42 has a larger diameter than the bonding wires 40, the metal bar 42 absorbs and removes more feedthrough signals.

Therefore, since the feed through signal is almost eliminated while passing through the metal bar 42, the signal flowing into the output pad side and causing the excitation is eliminated. Since the feed through signal is removed as described above, the stopband characteristic is improved compared to the conventional surface acoustic wave filter.

Another embodiment of the invention is shown in FIG. 6. This shows the side cross-section of the surface acoustic wave filter 10, and unlike the above examples, a special material is attached to the inner surface of the lid 36. The attached material is dielectric resin 44, which absorbs feedthrough signals and blocks them from going to the output pad. Therefore, the feed through signal is removed. At this time, application of the dielectric resin 44 is preferably concentrated in the center portion of the lead 36.

When the dielectric material 44 is applied to the pad 14 of the input IDT in the state where the dielectric resin 44 is applied to the inner surface of the lead 36, a feed through signal is generated as in the prior art. The generated feed through signal proceeds in the direction of the arrow as in the prior art, at which time the feed through signal is removed by the dielectric resin 44.

Therefore, the feed through signal is almost eliminated while passing through the portion where the dielectric resin 44 is applied, so that the signal flowing into the output pad side and causing excitation is eliminated. Since the feed through signal is removed as described above, the stopband characteristic is improved compared to the conventional surface acoustic wave filter.

As described above, according to the present invention, the stop band characteristic of the surface acoustic wave filter generated by the RF feed through signal, which is a signal transmitted directly to the output pad without passing through the surface acoustic wave member after being applied to the input pad of the surface acoustic wave filter, is deteriorated. There is an advantage to avoid.

Although the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that modifications and variations can be made within the spirit and scope of the invention, and such variations or modifications will belong to the appended claims. .

Claims (3)

It consists of an input IDT part, a ground bar, and an output IDT part, and a plurality of pads are formed on the side and electrically connected to each other by bonding wires, and a SAW member is installed in the center in the longitudinal direction, and leads are blocked from the outside on the upper side. In the surface acoustic wave filter package, Surface acoustic wave filter with a feed-through removal member is characterized in that the feed-through signal is blocked by connecting the ground pads in the opposite position of the pad using a bonding wire separated from each other. It consists of an input IDT part, a ground bar, and an output IDT part, and a plurality of pads are formed on the side and electrically connected to each other by bonding wires, and a SAW member is installed in the center in the longitudinal direction, and leads are blocked from the outside on the upper side. In the surface acoustic wave filter package, And a pair of ground pads adjacent to the ground bar in the pads and opposed to each other by a metal bar to cut off the feed throw signal. It consists of an input IDT part, a ground bar, and an output IDT part, and a plurality of pads are formed on the side and electrically connected to each other by bonding wires, and a SAW member is installed in the center in the longitudinal direction, and leads are blocked from the outside on the upper side. In the surface acoustic wave filter package, Surface acoustic wave filter The surface acoustic wave filter provided with a feed throw removing member characterized in that the feed-through signal is blocked by applying a dielectric resin material on the inner surface of the lid that blocks the package from the outside.