JP2006109390A - Surface acoustic wave resonator and electronic device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave resonator of arbitrary bandwidth and a filter. <P>SOLUTION: Electrodes having width of λ/4 and cord electrodes having gap of λ/4 are set to +1, -1, -1, +1 or the like instead of +1, -1, +1, -1 as in the conventional method. In this way, a structure in which the conversion efficiency and the reflective coefficient are reduced by decreasing the apparent electromechanical coupling factor or the width of resonance and antiresonance is reduced by decreasing the number of reflectors per unit length is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resonator using surface acoustic waves and an electronic device using the same, and has a structure in which the conversion efficiency of the interdigital electrode is reduced, or by providing a dielectric film on the substrate surface, thereby providing an electromechanical coupling coefficient. The present invention relates to a surface acoustic wave resonator having a structure in which the above-described structure is lowered.

A normal surface acoustic wave resonator has a structure of only a regular interdigital electrode of λ / 4 electrode width, or a structure in which reflectors of λ / 4 electrode width are provided at both ends of a regular interdigital transducer. The frequency width of anti-resonance is almost determined by the electromechanical coupling coefficient (k ² ) of the substrate used. Therefore, a large k ² substrate was not used for a relatively narrow bandwidth filter.

Problems to be solved by the invention

  The present invention has been made to remove the defects of the conventional surface acoustic wave resonator as described above, and by devising the apparent electromechanical coupling by devising the electrode structure, the conversion efficiency and the reflection coefficient are reduced. The present invention relates to a surface acoustic wave resonator having a structure in which the width of resonance and anti-resonance is reduced by reducing the number of reflectors per unit length or by reducing the number of reflectors per unit length. Is to provide.

Means for solving the problem

  In order to solve the above-described problems, a surface acoustic wave resonator according to the present invention includes a resonator in which interdigital electrodes are disposed on the surface of a piezoelectric / electrostrictive material substrate having a large electromechanical coupling coefficient or on a piezoelectric thin film substrate, Alternatively, in a resonator having a structure in which reflectors are arranged on both sides thereof, the polarity of the λ / 4 width electrode connected to the extraction electrode is alternately connected to positive and negative electrodes adjacent to the conventional +1, −1, +1, −1. For example, +1, -1, -1, -1, etc. are used to reduce the excitation efficiency, reduce the reflection efficiency of the reflector, or attach a dielectric thin film on the piezoelectric substrate. Resonance of the resonator by adopting a structure in which interdigital electrodes and reflectors are provided on the substrate, or a structure in which a dielectric is attached to the surface of the surface acoustic wave resonator and a conductor film is further attached thereon. And control the width of anti-resonance Than it is.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
As shown in FIG. 1, the first embodiment is a surface acoustic wave resonance having a structure in which interdigital electrodes are formed on the surface of a piezoelectric / electrostrictive material substrate 1 or a piezoelectric thin film substrate, or a structure in which reflectors are arranged on both sides thereof. The wavelength at the basic operating frequency is λ, the width of the positive electrode is λ / 4, the width of the negative electrode is λ / 4, the gap is λ / 4, and the extraction electrodes are arranged on both sides of the electrodes. In the interdigital electrode, the sign of the λ / 4 width electrode connected to the positive extraction electrode is +1, the sign of the λ / 4 width electrode connected to the negative extraction electrode is -1, and +1, −1, −1, The structure of −1, or the structure of +1, +1, +1, −1, −1, −1 as shown in FIG. 2, or the number of signs of the λ / 4 width electrode connected to the positive extraction electrode is ( 2K + 1) (K: positive integer including zero), of λ / 4 width electrode connected to negative extraction A surface acoustic wave resonator having a structure in which the number of codes is (2L + 1) (L: a positive integer including zero) interdigital electrodes and these electrodes are configured in N pairs, and one resonator A resonator having a structure in which the values of K and L are combined, a surface acoustic wave resonator having a structure in which reflectors are arranged on both sides of these resonators, and an electronic apparatus using these resonators.
In Example 2, the width of the electrode is λ / 4, the interdigital electrode having the structure of the cap λ / 4, and the electrode width of (5λ / 4) K and the gap is (λ / 4). A surface acoustic wave resonator having a structure in which interdigital electrodes are combined in one interdigital resonator, a surface acoustic wave resonator having a structure in which reflectors are arranged on both sides of these resonators, and these resonators. The electronic device used.
In Example 3, the period between adjacent electrode centers is λ / 2 or an integral multiple of λ / 2 in claims 1 and 2, and the width and gap of the electrodes are as described above. A surface acoustic wave resonator having a value of ± 50% and an electronic device using the resonator.
Example 4 is a surface acoustic wave resonator having a structure in which interdigital electrodes and reflectors are arranged on both sides thereof in claims 1, 2, and 3 of the claims. Where λ is the wavelength of the reflector, the width of the reflector is (λ / 2) × M (M: positive integer) and the gap is (λ / 2) × N (N: positive integer), or the width of the electrode is ( (λ / 4) × (2M−1), the gap is (λ / 4) × (2N−1), or the width is ± 50% of the above value, and the distance between these electrodes is ( A surface acoustic wave resonator having a short-circuited reflector of λ / 2) × K (K: integer) and an electronic device using these resonators.
5 embodiment, the piezoelectric-electrostrictive material the surface of the substrate 1 or the surface acoustic wave resonator with attached dielectric thin film H ₁ to the piezoelectric thin film on a substrate, and after producing the acoustic wave resonators thereon, the A resonator having a structure in which a metal film is deposited thereon, or a surface acoustic wave resonator having a structure in which a dielectric thin film is further deposited on the resonator, and the above metal film are deposited only on a reflector. A surface acoustic wave resonator having a structure and an electronic device using the same.
In Example 6 of the surface acoustic wave resonator according to claim 5, the wavelength at the fundamental operating frequency is λ, the film thickness of the thin film is H ₁ , and the film thickness H ₁ / λ is , A surface acoustic wave resonator in the range of 0.001 to 0.02 and an electronic device using the same.
In Example 7, the positive, negative electrodes and the metal film as Al, Cu, Mo, Au in the claims, the first, second, third, fourth, fifth, and sixth claims are used. , Ag, W, Ti, etc., or alloys thereof, and as the piezoelectric substrate 1, quartz, langasite single crystal, Li ₂ B ₄ O ₇ single crystal, BGO single crystal, BSO single crystal, LiNbO ₃ single crystal, LiTaO Interdigital electrode surface acoustic wave resonators using structures such as ZnO, AlN, LiTaO ₃ , LiNbO ₃ , KNbO ₃ , Ta ₂ O ₅ , and PZT as piezoelectric thin films, such as _three single crystals, KNbO ₃ single crystals, and PZT And an electronic device using these resonators.
In Example 8, the SiO ₂ thin film is formed on the surface acoustic wave resonator according to claims 1, 2, 3, 4, 5, 6, 7. Alternatively, an interdigital electrode surface acoustic wave resonator having a structure in which a dielectric film such as glass having a positive frequency temperature characteristic is attached, and an electronic device using the same.
In the ninth embodiment, the surface acoustic wave resonator according to the claims, the first, second, third, fourth, fifth, sixth, seventh, and eighth aspects is a ladder. A surface acoustic wave filter configured in a type and a lattice type, and an electronic device using the filter.

The invention's effect

As an example of calculation results of the above resonator, in FIG. 3, with the resonator structure of Figure 1, zero temperature ^{characteristic,} the _{SiO 2/5 ° Y-X} LiNbO 3 substrate having k 2 = 0.22 The characteristic of the ladder type filter used is shown. A ladder filter using a normal λ / 4 width electrode and a reflector has a bandwidth of 360 MHz (Δf / f ₀ = 0.18) at a center frequency of 2 GHz and a wideband characteristic. It ’s too wide to use. On the other hand, in the structure having the reflector of λ / 4 electrode width on both sides of the interdigital electrode of FIG. 1, the center frequency is 2 GHz and the bandwidth is 100 MHz (Δf / f ₀ = 0.05) as shown in FIG. Thus, it is possible to obtain a filter having an optimum band for a current cellular phone filter and having a zero temperature characteristic. In this patent, a resonator and a filter having an arbitrary bandwidth can be obtained by using a substrate having a large k ² .

An electrode configuration of a surface acoustic wave resonator according to the present invention having a period of +1, -1, -1, -1 as the interdigital electrode connection having an electrode width of λ / 4 and a gap of λ / 4. It is a top view and sectional drawing. The surface acoustic wave resonator according to the present invention has a period of +1, +1, +1, -1, -1, -1 as the interelectrode connection of the interdigital electrode having an electrode width of λ / 4 and a gap of λ / 4. It is the top view and sectional drawing of this electrode structure. A frequency characteristic of the ladder-type filter using the resonator of _{SiO 2/5 ° Y-X} LiNbO 3 in Figure 1 on the substrate structure according to the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Interdigital electrode, 3 ... Positive take-out electrode, 4 ... Negative take-out electrode, 5 ... Lambda / 4 electrode connected to positive take-out electrode, +1 electrode by sign, 6 ... Negative Λ / 4 electrode connected to the take-out electrode, denoted by -1 electrode, 7 ... reflector, 8 ... frequency characteristic of the ladder filter [GHz], 9 ... insertion loss of the frequency characteristic of the ladder filter [ dB]

Claims (9)

In a surface acoustic wave resonator having a structure in which interdigital electrodes are formed on the surface of a piezoelectric / electrostrictive material substrate 1 or a piezoelectric thin film substrate, or a structure in which reflectors are arranged on both sides thereof, the wavelength at the fundamental operating frequency is λ. In the interdigital electrode in which the width of the positive electrode is λ / 4, the width of the negative electrode is λ / 4, the gap is λ / 4, and the extraction electrodes are arranged on both sides of these electrodes, the positive electrode is connected to the positive electrode. The sign of the λ / 4 width electrode to be connected is +1, the sign of the λ / 4 width electrode connected to the negative take-out electrode is -1, and the structure is +1, -1, -1, -1, or the positive take-out electrode The number of signs of λ / 4 width electrodes to be connected is (2K + 1) (K: positive integer including zero), and the number of signs of λ / 4 width electrodes to be connected to negative extraction is (2L + 1) (L: zero) A positive integer) interdigital electrode, and these electrodes are divided into N pairs. A surface acoustic wave resonator having a structured structure, a resonator having a combination of K and L values in one resonator, and a surface acoustic wave resonance having a structure in which reflectors are arranged on both sides of these resonators. And electronic devices using these resonators. In claim 1, the interdigital electrode having the structure of λ / 4 electrode width and gap λ / 4 and the interdigital electrode having the electrode width of (5λ / 4) K and the gap of (λ / 4) are combined into one. A surface acoustic wave resonator having a structure combined among interdigital resonators, a surface acoustic wave resonator having a structure in which reflectors are arranged on both sides of these resonators, and an electronic device using these resonators. In claims 1 and 2, the period between adjacent electrode centers is λ / 2 or an integral multiple of λ / 2, and the width and gap of these electrodes are ± 50% of the above values. Some surface acoustic wave resonators and electronic devices using these resonators. In the first, second, and third claims, in the surface acoustic wave resonator having the structure in which the interdigital electrode and the reflectors are arranged on both sides thereof, the wavelength at the fundamental operating frequency is λ, The width of the reflector is (λ / 2) × M (M: positive integer) and the gap is (λ / 2) × N (N: positive integer) or the width of the electrode is (λ / 4) × ( 2M-1), the gap is (λ / 4) × (2N-1), or the width is ± 50% of the above value, and the distance between these electrodes is (λ / 2) × K A surface acoustic wave resonator having a short-circuited and open-type reflector (K: integer), and an electronic device using these resonators. The piezoelectric-electrostrictive surface of a material substrate 1 or the surface acoustic wave resonator with attached dielectric thin film H ₁ to the piezoelectric thin film on a substrate, and on after manufacturing the elastic wave resonators thereon, depositing a metal film thereon Or a surface acoustic wave resonator having a structure in which a dielectric thin film is further deposited on the resonator, and a surface acoustic wave resonance having a structure in which the metal film is deposited only on a reflector. And electronic device using the same. In the surface acoustic wave resonator according to claim 5, the wavelength at the fundamental operating frequency is λ, the film thickness of the thin film is H ₁ , and the film thickness H ₁ / λ of the thin film is 0.001 to 0 .02 surface acoustic wave resonator and electronic device using the same. In Claims, 1st, 2nd, 3rd, 4th, 5th and 6th, as positive and negative electrodes and metal film, Al, Cu, Mo, Au, Ag, W, Ti Or an alloy thereof, and the piezoelectric substrate 1 include quartz, langasite single crystal, Li ₂ B ₄ O ₇ single crystal, BGO single crystal, BSO single crystal, LiNbO ₃ single crystal, LiTaO ₃ single crystal, KNbO ₃ Interdigital electrode surface acoustic wave resonator having a structure using ZnO, AlN, LiTaO ₃ , LiNbO ₃ , KNbO ₃ , Ta ₂ O ₅ , PZT, etc. as a piezoelectric thin film such as single crystal or PZT, and the like Electronic equipment. An SiO ₂ thin film or a positive frequency temperature on the surface acoustic wave resonator according to claims 1, 2, 3, 4, 5, 6, 7. An interdigital electrode surface acoustic wave resonator having a structure in which a dielectric film such as glass having characteristics is attached, and an electronic device using the same. The surface acoustic wave resonators according to claims 1, 2, 3, 4, 5, 6, 7, and 8 are configured in a ladder type and a lattice type. Surface acoustic wave filter and electronic device using this filter.

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