JPH03205907A - Multi-electrode type surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain a satisfactory characteristic being excellent in an out-band suppression degree by providing the device with a grounding electrode pattern being formed separately in a closing mode between each input electrode and each output electrode. CONSTITUTION:On a piezoelectric substrate 1, an input electrode 2 and an output electrode 3 are placed alternately, and the input electrode 2 and the output electrode 3 are connected to an input electrode connecting pad 4 and an output electrode connecting pad 5, respectively, and connected to an input stem lead pin 6 and an output stem lead pin 7 by a wire 8, respectively. Also, in a closing mode between each input electrode 2 and each output electrode 3, a grounding common electrode pattern 12 is formed separately from them, and it is grounded to the metallic stem surface 11. In such a way, a mutual induction action by a leakage magnetic field between the input and the output electrodes, and an induction action by the capacity coupling are reduced, therefore, the influence of a direct wave drops, and the out-band suppression degree of a frequency characteristic is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides surface acoustic waves that are generated between input and output electrodes due to electromagnetic coupling (direct waves) between the two electrodes without being converted into surface acoustic waves. Is it designed to suppress electrical noise? We developed a multi-electrode surface acoustic wave device.

[Conventional technology]

In a surface acoustic wave device, a part of the input signal is not converted into a surface acoustic wave between the input and output electrodes, but propagates as a so-called IS wave due to Sat-like coupling and capacitive coupling between the two IE electrodes.
Various countermeasures have been proposed in the past to deal with the phenomenon that deteriorates the degree of suppression outside the belt.

For example, in Japanese Patent Publication No. 54-35478, 5"
In a surface acoustic wave device with a one-electrode configuration, a loop 7' flows to two output electrodes located symmetrically to a central input electrode.
A method is described in which the directions of XlO are mutually reversed and the magnetic fields generated by this loop current are made to be in mutually opposite directions on the central input electrode, thereby mutually absorbing the magnetic fields.
JP-A-57-162816 discloses a method of subdividing the current loop into a plurality of pieces using wiring and three-dimensionally intersecting electrode patterns to reduce the loop current that is the source of the magnetic field, thereby canceling out the five-field effect. ing. Also,
National technical report
Tachrbica Ljtaport VoL. 3
0 A I Fah. 1984) Volume 30, No. 1 (
(February 1984) Other 3'i articles on pages 166-174
! A countermeasure technique using polar type pI emission is described.

[Problem to be solved by the invention]

The above-mentioned conventional countermeasure technology is for the deterioration of the out-of-band suppression degree due to electromagnetic coupling and capacitive coupling between input and output electrodes. In multi-electrode surface acoustic wave devices used at high frequencies, due to the increase in the number of input electrodes and output electrodes, sufficient consideration has not been given to the grounding method used at high frequencies. At the same time, the input and output electrodes are grounded on the electrode pattern, but the results of investigating the actual characteristics show that the grounding of the electrode pattern is insufficient and out-of-band suppression occurs. There was a problem that the quality was deteriorating.

It is an object of the present invention to solve the problems of the conventional countermeasure techniques described above and to provide a multi-electrode surface acoustic wave device for high frequencies that has excellent characteristics with excellent out-of-band suppression. [Means for Solving the Problems] In order to achieve the above object, in the present invention, two or more input rods and three or more output electrodes that mutually transmit and receive surface acoustic waves are placed on the same propagation path. The wiring of the ground electrode for the output electrode (single-pole sparse and long part) is connected to the metal stem surface on the input stem lead pin side of the input electrode. In a high-frequency multi-camera surface acoustic wave device in which the motherboard or its extension) is connected to the metal stem surface on the output stem lead pin side of the output electrode and grounded, these points are connected between each input electrode and each output electrode. A separate grounding electrode pattern is provided between the electrodes, and this grounding electrode pattern is electrically connected on a piezoelectric substrate to form a common grounding electrode pattern, or this grounding electrode The pattern was divided into a certain number of electrode cycles and grounded to the metal stem surface. Furthermore, the connection pad patterns of the ground electrodes for each input and output electrode are divided and connected at regular intervals, and each of the connected ground electrode patterns for the input and output electrodes is photographed on the metal stem surface using independent κ wiring. Ground, one pole pattern for the input electrode and one dormitory for the output electrode!
5. The polar patterns are adjacent to each other and parallel to each other with a grounding electrode pattern provided separately between the input and output electrodes.
tx structure.

[For production]

By using the above-described structures alone or in combination, it is possible to reduce the influence of direct waves due to mutual induction due to leakage magnetic fields and capacitive coupling between input and output electrodes, which are problematic especially at high frequencies. In other words, a grounding electrode pattern is separately formed between each input and output electrode, threaded between these electrodes, and this separately formed grounding electrode pattern is placed on a piezoelectric substrate. The magnetic field generated between the input and output electrodes can be reduced by electrically connecting them to each other, or by connecting them in sections at a fixed number of electrode cycles, and directly grounding each of the divided grounding electrode patterns independently to the metal stem surface. It is possible to reduce the mutual induction effect between the two electrodes, and also to reduce the capacitive coupling between the input and output electrodes.

〔Example〕

FIG. 1 is a plan view of a first embodiment of the present invention. The compact substrate 1 is a lithium tammelate single crystal substrate (LETαOS) with 36° rotation, Y-axis cutting, and X-axis propagation.

In the electrode structure, the human-powered electrodes 2 and the output electrodes 3 are arranged alternately, and the number of input and output electrodes is 41a for both the human-powered electrodes and the output electrodes. The input electrode 2 and the output electrode 3 are connected to the human sword electrode 4 and the output 1L microconnection pad 5, respectively, and to the input stem lead pin 6 and output stem lead pin 7 of the package stem. , respectively, 25μ diameter fake M wire 8 or Au
Connected by wire. In addition, at high frequencies, deterioration of out-of-band suppression due to direct waves becomes a problem.
The metal stem surface has a structure in which the electrode pattern is pulled back so that the grounding of the grounding pad 9 of the grounding electrode for the input electrode is connected to the input stem lead pin 6 side, and the grounding of the grounding pad 10 of the grounding electrode for the output electrode is connected to the output stem lead pin 79A. 11
At the same time, a common electrode pattern 12 for grounding is sewn between each manual electrode 2 and each output electrode 30, and is separately connected to the grounding common electrode pattern 12.
It has a structure in which it is grounded to the metal stem surface 11. The center frequency of this multi-electrode surface acoustic wave device is 8r30MHz, and the electrode MA width of the input and output electrodes is 1.
．． The width of the common ground electrode pattern is 100μ. M-Ti alloy is used as the electrode material, and the electrode film thickness is 10
A film was formed using a DC magnet sputtering method, and an electrode was formed through a photolithography process.
The pad part has a 600% wing thickness.

FIG. 2 shows the loss-frequency characteristics of the first embodiment. As you can see from this figure, the filling of traps, which seems to be the effect of Takagi's direct technique, has also been changed, and compared to before, the number of traps has been reduced by about 5%.
The degree of etE out-of-band suppression was improved, and good frequency characteristics could be obtained.

FIG. 3 is a plan view of a second embodiment of the present invention, and the reference numerals are the same as in FIG. 1. The feature of the electrode pattern of this embodiment is that the grounding electrode pattern 12 formed separately between the input and output electrodes is divided into two electrodes, each of which is grounded to the metal stem surface. %, at high frequencies, even if you think it is grounded, in reality, the above-mentioned ground electrode pattern 1
If 2 are connected together to reduce the number of ground points, the capacitance will adversely affect the out-of-band characteristics. Figure 4 shows the relationship between the division period (number of poles) of the grounding electrode board of the input and output electrode panels and the degree of out-of-band suppression. It is easy to understand that the degree of out-of-band suppression deteriorates with each step. Based on this result,
Considering the number of wiring lines, the optimum dividing period for the grounding electrode pattern provided separately between the input and output electrodes is 2 (Figure 5 is a schematic diagram for the case where the number of divisions is 2). Compared to the first embodiment without division, the degree of out-of-band suppression is improved by about 5 ctE.

FIG. 6 shows a plan view of a third embodiment of the present invention. In this embodiment, the grounding electrode pattern 12 separately provided between the input and output electrodes is divided into two electrode periods, and the grounding electrode connection pad pattern 12 for each input and output electrode is They are connected to each other on a piezoelectric substrate. Each has a common ground electrode pattern 13 for each input electrode and a common ground electrode pattern 14 for each output electrode, and is in parallel contact with each other with the ground electrode pattern 12 separately provided between the input and output electrodes sandwiched therebetween. Shape 4. The degree of out-of-band suppression was about 13 dB compared to the conventional one.

FIG. 7 is a plan view of a fourth embodiment of the present invention. In this embodiment, the 35th! The common ground electrode patterns for input electrodes and output electrodes used in the example are each divided into two electrode periods.

From the relationship between the out-of-band suppression degree and the electrode division period shown in Figure 8, it can be seen that by dividing the division period into two, the out-of-band suppression degree is improved by about 3 dB compared to the case where no division is made.

〔Effect of the invention〕

As explained above, according to the present invention, especially in the case of a high frequency, multi-electrode type surface acoustic wave device, the mutual induction effect due to leakage magnetic field between input and output poles and the induction effect due to capacitive coupling can be reduced. , the influence of direct waves is reduced, and the degree of out-of-band suppression of frequency characteristics is improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of the first embodiment of the present invention, FIG. 2 is a diagram of the loss per cycle skill characteristic of the first embodiment, FIG. 3 is a plan view of the second embodiment of the present invention, and FIG. FIG. 5 is an explanatory diagram of the electrode division period, FIG. 6 is a plan view of the third embodiment of the present invention, and FIG. FIG. 8, a plan view of the fourth embodiment of the present invention, is a diagram showing the relationship between the electrode division period and the degree of out-of-band suppression in the fourth embodiment. 1...Piezoelectric substrate 2...
・・・・・・・・・Input turtle balance 3・・・・・・・・・・・・
Output 'Turtle pole 4...1...Input pole connection pad 5...1...Output pole connection pad 6...
・・・・・・・・・Custom lead pin 7・・・・
・・・・・・Output stem lead pin 8・・・・・・
...Wire 9... Grounding pad 10 for input electrode grounding electrode... Grounding pad 11 for output electrode grounding electrode...・・・・・・Metal stem surface

Claims (3)

[Claims] 1. Two or more input electrodes and three or more output electrodes that transmit and receive surface acoustic waves from each other are arranged on the same propagation path on the piezoelectric substrate, and the wiring of the ground electrode for the input electrodes is connected to the input stem of the input electrode. In a multi-electrode surface acoustic wave device, the wiring of the ground electrode for the output electrode is connected to the metal stem surface of the output stem lead pin side of the output electrode for grounding. A separate electrode pattern is provided between the output electrodes, and the electrode patterns provided separately between the input and output electrodes are electrically connected to each other on the piezoelectric substrate for grounding. A multi-electrode surface acoustic wave device characterized by being grounded as a common electrode pattern. 2. A claim in which an electrode pattern is separately provided between each input and output electrode, and is formed by dividing it at a period of no more than two electrodes, and each of these divided electrode patterns is independently grounded to the metal stem surface by wiring. 2. The multi-electrode surface acoustic wave device according to item 1. 3. The connection pad patterns of the ground electrodes for each input and output electrode are electrically connected to each other on the piezoelectric substrate at a period of two electrodes or less, and the connection pad pattern of the ground electrode for the input and output electrodes connected in this way is are individually grounded to the metal stem surface by wiring, and the connection pad pattern of the ground electrode for the input electrode and the connection pad pattern of the ground electrode for the output electrode are separately provided between the input and output electrodes. 3. The multi-electrode surface acoustic wave device according to claim 1, wherein the multi-electrode surface acoustic wave device is arranged adjacent to each other with a pattern in between and parallel to each other.