JPH07249958A - Multiple surface acoustic wave filter and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a filter including plural surface acoustic wave filters in its inside and allowed to reduce its size, weight and price by providing each of plural surface acoustic wave resonators having respectively different frequency bands with pairs of comb electrodes and reflectors. CONSTITUTION:Plural surface acoustic wave resonators 4 having respectively independent I/O electrodes and allowed to be connected to plural circuits having respectively different frequency bands are formed on a substrate 3 consisting of piezoelectric crystal. Each resonator 4 is provided with reflectors 42 on both the sides of exciting and receiving comb electrodes 41. Electrode digits of the electrode 41, insulating bands between the electrode digits and an insulating band between the electrode 41 and the reflector 42 are formed so that all of their width are set up to lambda/4. When plural resonators 4 having the different width of insulators are formed on the same piezo-electric substrate 3, a compact and light-weight multiple surface acoustic wave filter including plural surface acoustic wave filters in its inside can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonator type surface acoustic wave filter having a one-terminal pair surface acoustic wave resonator (hereinafter referred to as a surface acoustic wave resonator), and more particularly, to a frequency band on the same piezoelectric substrate. The present invention relates to a compound surface acoustic wave filter formed by forming a plurality of different surface acoustic wave resonators.

A mobile communication device such as a mobile phone in which the frequency bands of the transmitter and the receiver are different requires two surface acoustic wave filters. However, in such a portable device, the weight and the mounting space of components are restricted, and the surface acoustic wave filter is also required to be small and lightweight and low in cost.

Therefore, there is a demand for the development of a double surface acoustic wave filter which has a plurality of surface acoustic wave filters built therein and which can be reduced in size, weight and cost.

[0004]

2. Description of the Related Art FIG. 3 is a perspective view showing a conventional surface acoustic wave filter. An ordinary resonator type surface acoustic wave filter corresponding to a single frequency band has a comb-shaped electrode for excitation and reception on a substrate 1 made of a piezoelectric crystal as shown in Fig. 3 (a).
The surface acoustic wave resonator 2 is formed of the reflectors 21 disposed on both sides of the interdigital transducer 21 and the comb-shaped electrode 21.

A plurality of electrode fingers 23 of each pair of comb-shaped electrodes 21 are combined so that one electrode finger 23 is inserted between the other electrode fingers 23, and reflectors arranged on both sides of the comb-shaped electrode 21.
22 is composed of an open type or short type comb-shaped electrode, a strip array-shaped electrode, or the like.

If the wavelength of the surface acoustic wave is λ, all electrode fingers 23 in the conventional resonator type surface acoustic wave filter are λ / 4.
The insulating band interposed between the respective electrode fingers 23 and the insulating band interposed between the comb-shaped electrode 21 and the reflector 22 also have a width of λ / 4.

That is, when the frequency band in which such a surface acoustic wave filter is used is determined, from the wavelength λ of the surface acoustic wave corresponding to the frequency band, the conductor width of the electrode finger 23 constituting the comb-shaped electrode 21 and the distance between the electrode finger 23 are The width of the insulating strip and the insulating strip between the comb-shaped electrode 21 and the reflector 22 is determined.

In the conventional double surface acoustic wave filter, a plurality of substrates 1 are incorporated in the same package as shown in FIG. 3 (b), and the plurality of substrates 1 correspond to different frequency bands. A surface acoustic wave resonator 2 having an electrode finger 23 and an insulating band is formed.

[0009]

However, when a normal surface acoustic wave filter capable of supporting a single frequency band is used in a mobile communication device such as a mobile phone, two surface acoustic waves are printed on a printed wiring board. There is a problem in that the filter cannot be implemented to reduce the size and weight of the device and reduce the cost.

Further, by adopting a conventional double surface acoustic wave filter for such an apparatus, it is possible to reduce the size and weight of the apparatus and to reduce the cost. However, since two substrates are incorporated in the same package, it is small and lightweight. Insulation is not sufficient, and manufacturing cost reduction can hardly be expected.

An object of the present invention is to provide a multiple surface acoustic wave filter which has a plurality of surface acoustic wave filters built therein and which can be made smaller, lighter and less expensive.

[0012]

FIG. 1 is a perspective view showing a double surface acoustic wave filter according to the present invention. Note that the same object is denoted by the same symbol throughout the drawings.

The above problem comprises a plurality of surface wave resonators 4 formed on the same piezoelectric substrate 3 and having different frequency bands, and each surface wave resonator 4 is provided with a plurality of electrode fingers 43 and independently. And a pair of comb-shaped electrodes 41 having input / output electrodes 44, one electrode finger 43 being inserted between the other electrode fingers 43, and reflectors 42 arranged on both sides of the comb-shaped electrodes 41. This is achieved by the double surface acoustic wave filter of the present invention.

[0014]

In FIG. 1, a plurality of surface acoustic wave resonators having different frequency bands are formed on the same piezoelectric substrate, each surface acoustic wave resonator having a plurality of electrode fingers, and input / output electrodes independently provided. And a double surface acoustic wave filter of the present invention comprising at least a pair of comb-shaped electrodes combined so that one electrode finger is placed between the other electrode fingers, and reflectors arranged on both sides of the comb-shaped electrodes. Thus, it is possible to realize a multiple surface acoustic wave filter that incorporates a plurality of surface acoustic wave filters and can be reduced in size, weight and cost.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a diagram showing a method of manufacturing the surface acoustic wave filter according to the present invention.

The compound surface acoustic wave filter according to the present invention has independent input / output electrodes 44 on one substrate 3 made of a piezoelectric crystal such as LiNbO ₃ or LiTaO ₃ as shown in FIG. A plurality of surface wave resonators 4 that can be connected to circuits having different bands are formed.

The surface acoustic wave resonator 4 has a pair of exciting and receiving comb-shaped electrodes 41 and reflectors 42 arranged on both sides of the comb-shaped electrode 41, and has an electrode finger 43 for exciting and receiving. The comb-shaped electrodes 41 are combined so that one electrode finger 43 is inserted between the other electrode fingers 43.

Further, reflectors arranged on both sides of the comb-shaped electrode 41.
Reference numeral 42 is an open or short-circuit type comb-shaped electrode, a strip array-shaped electrode, or the like. / 4
Is formed.

That is, a plurality of surface acoustic wave resonators 4 having different widths of the electrode fingers 43, the insulating band between the electrode fingers 43 and the insulating band between the comb-shaped electrode 41 and the reflector 42 are formed on the same piezoelectric substrate 3. By doing so, it is possible to form a multiple surface acoustic wave filter having a plurality of surface acoustic wave filters built therein.

Therefore, as shown in FIG. 2, a plurality of surface wave resonators 4 having different frequency bands formed on the same piezoelectric substrate 3 are defined as one block 5, and a plurality of blocks 5 are predetermined on a wafer 6 made of a piezoelectric material. The blocks 5 are formed at intervals and are cut into regions including the blocks 5.

As described above, a plurality of surface acoustic wave resonators having different frequency bands are formed on the same piezoelectric substrate, each surface acoustic wave resonator having a plurality of electrode fingers, and input / output electrodes independently provided. A surface acoustic wave filter of the present invention comprising at least a pair of comb-shaped electrodes combined so that one electrode finger is inserted between the other electrode fingers, and reflectors arranged on both sides of the comb-shaped electrodes. Thus, it is possible to realize a multiple surface acoustic wave filter that incorporates a plurality of surface acoustic wave filters and can be reduced in size, weight and cost.

[0022]

As described above, according to the present invention, it is possible to provide a multiple surface acoustic wave filter which has a plurality of surface acoustic wave filters built therein and which can be reduced in size, weight and cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a compound surface acoustic wave filter according to the present invention.

FIG. 2 is a diagram showing a method of manufacturing a surface acoustic wave filter according to the present invention.

FIG. 3 is a perspective view showing a conventional surface acoustic wave filter.

[Explanation of symbols]

 3 Piezoelectric Substrate 4 Surface Wave Resonator 5 Block 6 Wafer 41 Comb Electrode 42 Reflector 43 Electrode Finger 44 Input / Output Electrode

Claims (2)

[Claims] 1. A plurality of surface wave resonators (4) having different frequency bands formed on the same piezoelectric substrate (3), each of the surface wave resonators (4) having a plurality of electrode fingers (43). ), And an independently provided input / output electrode (44), and at least one pair of comb-shaped electrodes (41) combined so that one electrode finger (43) is inserted between the other electrode fingers (43). A composite surface acoustic wave filter comprising reflectors (42) arranged on both sides of the comb-shaped electrode (41). 2. One block of a plurality of surface wave resonators (4) formed on the same piezoelectric substrate (3) and having different frequency bands.
(5), and after forming a plurality of the blocks (5) arranged at a predetermined interval on a wafer (6) made of a piezoelectric material, the wafer (6) is formed for each region including each block (5). A method for manufacturing a double surface acoustic wave filter, comprising: