JPS58141023A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain a surface acoustic wave device which has less insertion loss and a wide band, by forming cross finger electrodes of at least one surface wave transducer in such a way that the surface wave propagation distance between surface wave transducers for energizing and reception is not constant. CONSTITUTION:On the piezoelectric substrate 3 of the surface acoustic wave device, the transducers 4 and 5 are at such distance l that nL/2<b<(n+1)L/2. The shape of cross electrodes of the transducer is made different from those of the transducer 4 and the propagation distance l of a surface wave energized by the transducer 4 is varied by two stages. Thus, insertion loss is reduced and band width is increased.

Description

[Detailed description of the invention] The present invention relates to a surface acoustic wave device.

As shown in FIG. 1, this type of surface acoustic wave device is composed of a piezoelectric substrate 3 and excitation and reception surface wave transducers 1 and 2 provided on this substrate. The distance l between the electrode finger centers at the ends of surface wave transducers 1 and 2 is -L
(L: electrode finger period, n: integer). However, in such a surface device, the resonance frequency at which the loss of one surface wave converter itself is minimized and the resonance frequency at which the loss between the excitation and reception image converters is minimum do not match. This has the disadvantage that the loss due to damage increases. Nineteenth, it has the disadvantage of a narrow band.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a surface acoustic wave device ff1l with a small insertion loss and a wide band.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a configuration diagram showing an embodiment of the present invention.

The transducers 4 and 5 are arranged on the piezoelectric substrate 3 so as to correspond to the same. The shape of the interdigitated electrodes of the transducer 5 is configured to be different from the electrode fingers of the transducer a4.

The propagation distance 1 (l satisfies the above-mentioned conditions) of the surface waves captured by the converter 4 is changed in two steps.

With such a configuration, insertion loss can be reduced and bandwidth can be increased.

FIGS. 3 and 4 are diagrams illustrating loss reduction when the shapes of the converters 4 and 5 are the same. FIG. 3 shows the characteristic resonance characteristics A of transducers 4 and 5 of a surface wave device having aluminum interdigital electrodes 2500 angstroms thick formed on a quartz plate.

The electrode spacing l is 0.4L (L=11.3 microns) IO,
The interelectrode resonance characteristics B to L determined by the transducers 4 and 5 are shown when the value is changed to 47Ly0.5L.

At the 31st threshold, the characteristic person is co-imaging frequency, wave number FO = 277
．． It shows the minimum loss at 6228MHz, but
(electrode spacing 1=0.5LF) Characteristic D (2) The minimum loss is smaller than that of Characteristic B. For this reason, the conventional surface device with l=0.5L has a large insertion loss of 2.5 dB as a surface acoustic wave device, as shown by characteristic d in Figure 84.

In addition, the electrode finger period at this time is the surface wave velocity V±315
4m/st common frequency Fv =277.6228MHz
Z), it is 11.3 microoy (μm).

On the other hand, if l is selected to be 0.47L so that the minimum loss is smaller than 0.5L as in the device of the present invention, the characteristic C shown in Fig. 4
(Break 41) As shown in K f, the insertion loss can be reduced to 1ri1.15dB. In addition, by selecting l to 0.4 L, the maximum interelectrode resonance characteristic can be obtained, and the insertion loss can be further reduced to 0.2 dB as shown in the characteristic b in Figure 4 (two points @I). can.

A comparison is shown between the loss and the significant loss when l is chosen as -LK as in the conventional case. As is clear from Table 1, the structure of the present invention has a smaller loss in any case of n. The distance l=- shows the resonance characteristics between the surface wave transducers 4 and 5. As is clear from this figure, the band is as narrow as n, 3 MHz. On the other hand, the 6th
The figure shows the book M#Il composition CX=0.44L, Y shown in FIG.
=0.422L)K, the band can be widened to 0.4MHz, as is clear from the characteristics shown in FIG. 't. Insertion loss can also be reduced from the conventional 0.55 dB to 0.2 dB. Note that the center frequency 'O is 281.29
It is 80MHz.

Figures 8g7 and 8 show the logarithms of converters 4 and 5 as 33
The characteristics of the conventional configuration and the characteristics of the configuration of the present invention when set to 0 pairs and 360 pairs are shown, and as is clear from FIG. 8, the configuration of the present invention can widen the band.

FIG. 9 shows another embodiment of the present invention, in which the electrode fingers of the reception surface wave transducer 5 are made oblique.

Continuously changing while satisfying all. Even in such a configuration, the band can be widened as in the configuration shown in FIG.

As described above, according to the present invention, a surface acoustic wave device with low loss and a wide band can be easily realized compared to conventional surface acoustic wave devices.

[Brief explanation of the drawing]

It! Figure 1 is a diagram showing a conventional surface acoustic wave device, Figure 2 is a diagram showing an embodiment of the present invention, Figure 3 is a diagram showing resonance characteristics of a surface acoustic wave transducer, and Figure 4 is a diagram showing a surface acoustic wave transducer. FIGS. 5 to 8 are diagrams showing the frequency characteristics of the device, FIGS. 5 to 8 are ninth characteristic diagrams explaining the present invention in detail, and FIG. 9 is a diagram showing another embodiment of the present invention. In FIG. 2 and FIG. 9, 3...piezoelectric substrate. 4.5...Surface wave converter. Hayabusa I figure

Claims (1)

[Scope of Claims] An excitation surface wave transducer consisting of a plurality of rows of interdigitated finger electrodes each having an electrode period of L, and a plurality of pairs of intersecting finger electrodes each having an electrode period of n. L is a piezoelectric device arranged at a distance from the receiving surface wave transducer at a distance of (-L < l <-!L-!-L L : 2 n=o, 1t2...) In a surface acoustic wave device having a substrate, intersecting finger electrodes of at least one of the excitation and reception surface wave transducers are connected to a surface wave propagation distance between the excitation and reception surface wave transducers. 1. A surface acoustic wave transducer characterized in that the surface acoustic wave transducer is formed so that the angle is not constant.