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AssigneeToyo Communication Equipment Co., Ltd.
InventorsYuzo Nakazawa, Kazuo Ono, Masaki Tanaka, Takao Morita, Takefumi Kurosaki
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A high frequency narrow-band pass multi-mode filter in constructed in such manner that SAW of SSBW resonators are closely disposed to each other on a single piezo-electric substrate to generate different vibration modes of different resonance frequencies, conditions that the resonators are acoustically coupled to each other to cause these vibration modes, are experimentally found, and the above conditions are satisfied by the filter. In order to reduce the ohmic loss of a very narrow common bus bar, the number of strip pairs of electrode in both interdigital transducers (hereinafter referred to as IDT) is minimized and instead reflectors are provided on the both sides of said TDTs to compensate for the reduction of its Q value. A part of the bus bar for the IDT electrodes is formed integral with some or all of gratings of the reflectors, whereby the connecting positions of the grating electrodes with respect to lead terminals can be positioned with a high freedom.
A high-frequency narrow-band pass multi-mode filter comprising first and second resonators arranged adjacent to each other, each of said resonators having the same resonance frequency and comprising a pair of comb-type interdigital transducer electrode arrays, the electrodes of said arrays being interleaved with each other, and a common bus bar provided between said first and second resonators, said first and second resonators being arranged in directions perpendicular to the propagation directions of waves excited by said resonators and in close proximity to each other on a piezoelectric substrate so that acoustic coupling between said first and second resonators is attained, thereby causing first and second resonance frequencies of different vibrating modes, the overlap of the electrodes of said respective pairs of electrode arrays of said first and second resonators defining respective first and second acoustic aperatures of width w and the distance between said first and second acoustic aperatures defining a gap g, said filter utilizing said first and second resonance frequencies of different vibration modes generated by the acoustic coupling, wherein said width w and gap g satisfies the relation w.ltoreq.20.lambda. and g.ltoreq.6.lambda., where .lambda. is the wavelength of the wave excited by said resonators.
Dependencies are inferred from the claim text.