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JPH03149997

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DESCRIPTION JPH03149997
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustoelectric transducer, and more particularly to a delivery device that converts underwater
acoustic waves into electrical signals and detects the direction of arrival of acoustic waves.
[Background Art] Conventionally, this type of delivery device has a structure in which an inner
electrode 102 and an outer electrode 103 are provided on a cylindrical piezoelectric vibrator
101 as shown in FIG. 6, and at least one electrode is divided into four. ing. The sound wave is
detected by the respiratory pressure of the cylindrical piezoelectric vibrator 101 due to the
sound pressure (the zeroth order vibration in the circumferential direction in which the diameter
increases and decreases), and at this time, the internal electrode 102 and the external electrode It
utilizes the fact that a voltage proportional to the sound pressure is generated between it and
103. Also, in order to detect the direction of arrival of the sound wave, the primary longitudinal
vibration generated in the circumferential direction when the wavelength of the sound is longer
than the outer diameter of the cylindrical piezoelectric vibrator 101 is used. That is, the quadrant
is determined from the difference in amplitude between the outputs of the 2 m electrodes facing
each other and the internal electrodes 1020 divided into four and the phase difference between
the two outputs and the output car obtained by shorting the four electrodes. [Problems to be
Solved by the Invention] The conventional acoustoelectric converter converts the stress
generated by the respiratory vibration of the cylindrical piezoelectric vibrator 101 into an
electric signal by the piezoelectric effect. In this case, the delivery sensitivity (conversion
coefficient between sound pressure and output voltage) M is M = g3! ??????????
Here, gst is a piezoelectric constant, and a is an average half of the cylindrical piezoelectric
vibrator 101. Therefore, if the outer diameter of the cylindrical piezoelectric vibrator 101 is
reduced in order to miniaturize the delivery device, the delivery sensitivity is lowered, which
makes it difficult to detect the sound wave. In addition, since the outer surface electrode 103 is
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provided on the outer surface of the cylindrical piezoelectric vibrator 101, a waterproof structure
such as covering a rubber boot or applying a mold prevents corrosion of the electrode and has a
problem that insulation must be maintained. there were. Furthermore, in order to draw the lead
wire from the outer surface electrode 103 inward, it is necessary to carry out work such as 9
providing an introduction hole at the upper and lower ends of the cylindrical piezoelectric
vibrator 101 and drawing a part of the outer surface electrode 103 inward. There was a problem
that. [Means for Solving the Problem] In order to solve such problems, the acoustoelectric
converter according to the present invention comprises a cylindrical vibrator and at least one of
the inner surface and the outer surface of the vibrator. Surface acoustic wave resonators are
provided at divided positions. 6) In the present invention, the sound pressure and the direction of
arrival of the incoming sound wave are determined from the frequency change of the surface
acoustic wave oscillator. Sixth Embodiment Next, the present invention will be described with
reference to the drawings.
FIG. 1 is a cross-sectional view of an acoustoelectric transducer according to an embodiment of
the present invention. In the figure, surface acoustic wave resonators (hereinafter referred to as
SAW resonators) 12 * and 12 ? -12 g-124 are provided at positions obtained by equally dividing
the inner surface of the cylindrical vibrating body 11 closed at both ends and having a watertight
structure. ing. These four SAW resonators 121.12x, 12g. As shown in FIG. 2, the SAW resonators
121, 141, 14g and 144 are configured by providing amplifiers 131 ░ 13 ? = 13s and 13a as
shown in FIG. 2, and four of chl, ch2, eh3 and eh4 are formed. Get the oscillator output. In such a
configuration, the cylindrical vibrator 11 vibrates in response to underwater acoustic waves. The
respiratory vibration of the cylindrical vibrator 11 has an enlarged diameter as shown by a
dotted line in FIG. The point-symmetrical mode to be reduced is excited by the sound wave
coming from any direction of the radial direction of the cylindrical vibrator 11. When the outer
diameter of the cylindrical vibrating body 11 is smaller than the wavelength of the sound wave, a
pressure difference occurs between the surface in the direction of the arrow A in the drawing
where the sound wave arrives and the surface on the opposite side. At this time, as shown by
dotted lines in FIG. 4, axisymmetric vibration (a first order vibration of the circumferential
direction) is excited with the propagation direction of the sound wave as an axis. In the steady
state where no sound wave arrives, each vibrator 14! The oscillation frequency fo of ~ 144 is
constant and is f = 2d. Here, ma is the propagation velocity of surface acoustic waves. d is the
center-to-center distance of the interdigital transducer. When a sound wave arrives and the
cylindrical vibrator 11 vibrates in the breathing mode, the electrode spacing changes according
to the sound pressure and frequency of the sound wave, and the outputs of the respective
oscillators undergo frequency modulation with the same phase. If this is demodulated and the
four outputs are averaged, the sound pressure signal of the sound wave can be reproduced. The
direction of the incoming sound wave is determined by comparing the phase of the signal
obtained by demodulating the oscillation output of each of the oscillators 141 to 144 with the
phase of the output of the respiratory vibration. That is, as shown in FIG. 5, the cylindrical
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vibrator 11 is divided into four quadrants according to the positions where the SAW vibrators
12z, 12 ?, 12g and 124 are provided. When the phases of the demodulated signals of the
oscillators 141 to 144 are compared based on the output obtained in the breathing mode, as
shown in Table 1 below, the phase state changes according to the direction in which the sound
wave has arrived. It becomes possible. Table 11 Quadrant 1 fo l f 1 f 3 ? f 0 If 4 k 111 1 1 1 1
? 1 ? 1 Note that, in the embodiment described above, the case where the SAW resonators 121
to 124 are provided on the inner surface of the cylindrical vibrating body 11 is shown. However,
they may be provided on the outer surface or both.
Further, any elastic body can be used as the cylindrical vibrator 11. Also, the oscillation
frequencies f of the four SAW oscillators 141 to 144 in the steady state are respectively different
frequencies, these outputs are collectively multiplexed and transmitted by wire or wireless,
transmitted to a remote place, and then transmitted in the same manner as above. It is also
possible to perform reproduction of the sound pressure signal and discrimination of the direction
by demodulation. [Effects of the Invention] As described above, according to the present
invention, the SAW resonator is provided at at least one of four equally divided positions on the
inner surface or the outer surface of the cylindrical vibrator, so that the frequency change of the
SAW oscillator can be Since the sound pressure and the direction of arrival can be determined,
the material and thickness of the cylindrical vibrator can be freely selected as long as it
withstands the water pressure used. Since it does not depend on the outer diameter of the
cylindrical vibrator, it is possible to obtain the effect that it is possible to miniaturize it with the
same receiving sensitivity. Furthermore, in the case where the SAW resonator is provided only on
the inner surface of the cylindrical vibrator, there is obtained an effect that there is no need to
protect the electrode such as covering or molding a rubber boot on the outer surface.
[0002]
Brief description of the drawings
[0003]
Fig. 1 is a cross-sectional view of the embodiment of the present invention, Fig. 2 is an
explanatory view showing a configuration of a SAW oscillator, Fig. 5g is an explanatory view of
respiratory vibration of a cylindrical vibrating body, and Fig. 4 is an explanation of line
symmetrical vibration. FIG. 5 is an explanatory view showing the relationship between the SAW
oscillator and the quadrant, and FIG. 6 is a cross-sectional view showing a conventional
acoustoelectric transducer.
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11 иии Cylindrical vibrator, 121.12 z, 123 ░ 124 и и и Surface acoustic wave (SAW) resonator, 13
?. 13z, 133. 134 ? ? ? Amplifier, 14t, 14 ?. 14g, 144 и и и surface acoustic wave (SAW)
oscillator, 101 и и и piezoelectric vibrator, 102 и и и inner surface electrode, 103 и и и outer surface
electrode.
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