B.D. Zajtsev - Dr. Sc. (Phys.-Math.), Professor, Head of Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: zai-boris@yandex.ru I.A. Borodina - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: borodinaia@yandex.ru A.A. Teplykh - Ph. D. (Phys.-Math.), Senior Research Scientist, Laboratory of Physical Acoustics, Saratov branch of Kotel\'nikov IRE of RAS. E-mail: teplykhaa@mail.ru I.E. Kuznetsova - Dr. Sc. (Phys.-Math.), Associate Professor, Leading Research Scientist, Laboratory of Electronic Processes in Semiconductor Devices, Kotel\'nikov IRE of RAS (Moscow). E-mail: kuziren@yandex.ru

It is known the elementary bandpass filter on surface acoustic wave (SAW) represents the delay line with interdigital transducers (IDTs) which contains required quantity of fingers. The filters on SAW have the lower limit frequency about ~ 40 MHz. Further lowering the frequency leads to the need of use the waveguides of significant thickness that complicates their development and use in practice. For example, for frequency of ~ 3,5 MHz and wavelength of 1,5 mm acoustic wave has the surface nature for the plate thickness of ~ 15 mm. At present there exists the need in bandpass filters operating on frequencies 1 - 20 MHz. It is apparent that acoustic filters of the pointed frequency range keeping all technological advantages of SAW may be realized on acoustic waves propagating in piezoelectric plates. However there is no any information about similar developments in literature. The present paper firstly describes the results of the investigation of the band-pass filter based on acoustic wave in piezoelectric plate. The filter using shear horizontal acoustic wave of zero order (SH0) propagating in plate of Y - X lithium niobate plate was developed and studied. The initial plate had shear dimensions of 48×40 mm2 and thickness of 500 µm. Two pairs of IDTs were deposited on this plate by means of photolithography. One channel contains 13 pairs of non-split fingers with spatial period of 1,18 mm, and other one contains 13 pairs of split fingers with spatial period of 1,12 mm. For both channels the distance between IDTs was equal 10 mm. It has been found that the best characteristics are ensured by filter with the split fingers. It has been shown that for operation on the fundamental harmonics with the central frequency of 3,5 - 3,7 MHz with plate thickness of 200 - 500 µm the minimum insertion loss in the pass band lies in the range 10 - 11 dB with amplitude pulse less than 2 dB. At that pass band on the level of 3 dB is equal ~ 4% and does not depend on the plate thickness. The signal suppression outside of the pass band exceeds 30 dB. For the operation on the third harmonics the acceptable frequency characteristics exist for plate thickness of 250 - 400 µm. For central frequency of 11,5 - 12 MHz the pass band on the level of 3 dB is equal 3 - 4%. The pulsations in pass band are practically absent and minimum insertion loss does not exceed 10 - 11 dB. At that the signal suppression outside of the pass band is more than 25 dB.

 

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