Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Tsutomu Igaki

Ken Matsunami

Kazunori Nishimura

Shigeru Tsuzuki

Hiroyuki Nakamura

Kazuo Ikeda

Toru Yamada

Toshio Ishizaki

Shun-ichi Seki

Akio Tsunekawa

Kazuki Nishimura

A surface acoustic wave resonator has a piezoelectric substrate (), an IDT () formed of a plurality of electrode fingers () disposed on piezoelectric substrate (), and reflectors () disposed near the opposite ends of IDT (). The IDT () has a gradation region where the electrode finger pitch of the plurality of electrode fingers () at the opposite ends is different from the electrode finger pitch near the center of the IDT (). In this gradation region, the electrode finger pitches are sequentially varied in the range from the electrode finger at the farthest end that is one end of the gradation region to the electrode finger lying at the other end of the gradation region. The electrode finger pitch of the electrode fingers at the farthest end that is one end of the gradation region is set to be 1 through 5% smaller than the electrode finger pitch near the center of the IDT ().

Surface acoustic wave resonator, and surface acoustic wave filter

A Q-factor of a resonator at a high frequency is improved. An insertion loss of a filter using such a resonator and steepness of the filter are improved. A plurality of surface acoustic wave resonators including an interdigital transducer and reflecting electrodes provided on both sides thereof are connected in parallel on a piezoelectric substrate. Resonance frequencies of the surface acoustic wave resonators are rendered equal among all the resonators connected in parallel. In this way, the Q-factor of the resonance can be improved. A surface acoustic wave filter using such surface acoustic wave resonators is formed in order to improve the insertion loss and the steepness.

Surface acoustic wave resonator and surface acoustic wave filter using the same

A SAW filter is configured by forming a first IDT and a second IDT on a piezoelectric substrate, and the first IDT is arranged between one terminal of input/output terminals and another terminal of the input/output terminals, i.e., serially in a signal path, and the second IDT is arranged in parallel to a signal path from a portion between one terminal of the input/output terminals and the first IDT. The first IDT and the second IDT are arranged in proximity to each other and on the same propagation path of surface acoustic waves which are excited by each of the resonators.

Surface acoustic wave filter

A saw filter of the invention has a piezoelectric substrate (), plural numbers of IDT electrodes () arranged on a surface of the piezoelectric substrate () as well as on a first surface acoustic wave propagation path, reflector electrodes () arranged at least at both ends of a first electrode pattern formed including the plural IDT electrodes (), one or more IDT electrodes () arranged on the surface of the piezoelectric substrate () as well as on a second surface acoustic wave propagation path which is different from the first surface acoustic wave propagation path and reflector electrodes arranged at least at both sides of a second electrode pattern formed including the IDT electrode (), in which the IDT electrodes () on the first surface acoustic wave propagation path are electrically connected in series by connecting wirings () and the IDT electrode () on the second surface acoustic wave propagation path is connected between the connecting wirings () and the ground (), which are arranged between the first electrode pattern and the second electrode pattern. According to this, the chip size can be made small.

Surface acoustic wave filter and communications apparatus using the same

A saw device comprises input/output interdigital transducer (IDT) electrodes( ) provided on piezoelectric substrates ( ), a first reflector electrode ( ) following the input IDT electrode ( ), and a second reflector electrode ( ) preceding the output IDT electrode ( ). The device satisfies the following inequality ( ) to provide preferable characteristics in a pass band: 2(&thgr;&minus;5)&lE;tan (D/L)&lE;2(&thgr;&plus;5) where &thgr;: the inclination (in degree, except zero) of the first or second reflector electrode of the input and output IDT electrodes with respect to a plane perpendicular to the direction in which surface acoustic waves travel. D: the pitch (in micron) of the input and output IDT electrodes in the direction in which surface acoustic waves travel. L: the pitch (in micron) of the first and second reflector electrodes.

SAW device with inclined reflectors and communication device using SAW device

A SAW filter comprising a piezoelectric substrate and at least two filter tracks formed on the substrate, each having at least two IDT electrodes for input and output. The two filter tracks have substantially the same phase within a pass band, while it is substantially inverse-phased outside the pass band. For realizing the above-described conditions, input IDT electrode of one filter track is connected in parallel with input IDT electrode of the other filter track, while output IDT electrode of one filter track is connected in parallel with output IDT electrode of the other filter track. Furthermore, frequency values of said two filter tracks substantially coincide at a point dB lower from the peak transfer function value. Thus the above-configured SAW filter of the present invention is smaller in the overall size and offers a broad pass band and a steep attenuation characteristic.

A surface acoustic wave (SAW) filter is disclosed which comprises a piezoelectric substrate and at least two Interdigital Transducers (IDTs) having four fingered electrodes in a region corresponding to one-wavelength of SAW excited on the piezoelectric substrate. At least one IDT is formed of at least one pair of fingered electrodes having different electrode widths. By provision of the pair of fingered electrodes being different in electrode width, the IDT can be given unidirectionality. Thus, a SAW filter producing a low insertion loss and having good amplitude and phase characteristics in the pass-band can be realized. Further, by using such SAW filter, a high-performance and low-cost communication apparatus, such as a CDMA-system mobile telephone, can be realized.

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Hyogo, Japan

Tsutomu Igaki