JPH0631222U - Surface acoustic wave resonator - Google Patents

Abstract

(57) [Abstract] [Purpose] Suppressing spurious due to higher-order modes of a surface acoustic wave resonator with weighted IDT electrodes. [Structure] A ridge line 7 showing a weighted shape of an IDT electrode 8 and a cutting line of an electrode finger 5 are substantially aligned with each other to reduce disturbance of a surface wave due to an electrode finger gap 6 for weighting. [Effect] The frequency jump phenomenon when used as an oscillation element of a VCO was suppressed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surface acoustic wave resonator in which a interdigital transducer is formed on a piezoelectric substrate, and more particularly to a surface acoustic wave resonator in which the interdigital transducer is weighted.

[0002]

[Prior art]

As a typical example, a Love wave (SH wave) type surface acoustic wave resonator whose electromechanical coupling coefficient (K ² ) is significantly larger than that of a Rayleigh wave type surface acoustic wave (P + SV wave) will be described. FIG. 3 (a) is a plan view showing an example of a conventional structure of a rhombic weighted Love wave type surface acoustic wave resonator, and FIGS. 3 (b) and 3 (c) are partially enlarged views of a circled portion 4A of FIG. It is a figure. In FIG. 3, 1 is a piezoelectric substrate, 2 is a interdigital transducer (hereinafter abbreviated as IDT), 3 and 4 are connection terminals, 5 is electrode fingers, and 6 is for weighting. A gap (hereinafter referred to as GAP) obtained by cutting the electrode finger 5, and a and b are cutting lines thereof. Reference numeral 7 indicates a weighted edge line. By attaching a heavy metal IDT electrode 2 such as gold (Au), silver (Ag) or platinum (Pt) onto a piezoelectric substrate 1 such as a LiNbO ₃ (lithium niobate) rotating Y plate as shown in FIG. A pseudo-surface acoustic wave with large propagation attenuation existing on the substrate surface is used as a non-attenuated Love wave type surface wave, and a surface acoustic wave resonator without a reflector is constructed. In the example of FIG. 3, in order to improve the impedance characteristics of the surface acoustic wave resonator, diamond-shaped weighting is applied to the IDT electrode.

[0003]

[Problems to be solved by the device]

 However, as shown in FIG. 3C, the cutting lines a and b of the GAP 6 do not coincide with the weighting ridge line 7, and the weighting accuracy is locally deteriorated, and the IDT electrode is anharmonic. It is thought that they combine with and cause a spurious response. Generally, when a surface acoustic wave resonator is used to form a voltage controlled oscillator (VCO), even if there is a very small spurious in the resonator, it causes frequency skipping, and therefore it is required that there be no spurious. . An object of the present invention is to solve the above problems and provide a surface acoustic wave resonator with suppressed spurious responses.

[0004]

[Means for Solving the Problems]

 The surface acoustic wave resonator of the present invention is a surface acoustic wave resonator in which a weighted interdigital transducer is formed on a piezoelectric substrate, and the weighted interdigital transducer is applied to the interdigital transducer. It is characterized in that a gap between the electrode fingers is provided so that the ridgeline showing the shape and the cutting line for cutting the electrode finger are substantially coincident with each other.

[0005]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the drawings. As a typical example, a Love wave type surface acoustic wave resonator will be described. FIG. 1A is a plan view showing the electrode structure of a rhombus-weighted surface acoustic wave resonator according to a first embodiment of the present invention, and FIG. 1B is enclosed by a circle in FIG. It is a partially enlarged view of 1A. In FIG. 1, reference numeral 1 is a piezoelectric substrate, 8 is an IDT in which a ridge line 7 for diamond weighting and a cutting line of an electrode finger are aligned with each other to form a GAP, and 3 and 4 are connection terminals.

FIG. 2A is a plan view showing an electrode structure of a Love wave type surface acoustic wave resonator which is weighted in a COSINE manner according to a second embodiment of the present invention, and FIG. It is a partially expanded view of a circle 3A. Illustration of the piezoelectric substrate is omitted. In FIG. 2, reference numeral 11 denotes an IDT in which a CO SINE-shaped weighting ridgeline 12 and a cutting line of an electrode finger are aligned to form a GAP, and reference numerals 3 and 4 denote connection terminals.

[0007]

[Effect of device]

 As described in detail above, according to the present invention, the electrode structure is such that the cutting line of GAP coincides with the ridge of weighting, so that the weighting accuracy is improved and the spurious response suppression is extremely effective in practice.

[Brief description of drawings]

FIG. 1 is an electrode configuration example diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of an electrode structure showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example of a conventional rhombus-weighted surface acoustic wave resonator.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 IDT 3,4 Connection Terminal 5 Electrode Finger 6 Gap 7 Ridge Line 8,11 IDT 12 Ridge Line

Claims (1)

[Scope of utility model registration request] 1. A surface acoustic wave resonator in which a weighted interdigital transducer is formed on a piezoelectric substrate, and a ridge line indicating the weighted shape applied to the interdigital transducer, A surface acoustic wave resonator, characterized in that a gap between the electrode fingers is provided so that a cutting line for cutting the electrode fingers substantially coincides with the cutting line.