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The present invention relates to a variable resonance type underwater transmitter-receiver
capable of changing a resonance frequency. Among the conventional underwater transducers of
this type, an example using the magnetostrictive effect is shown in FIG. In the figure, reference
numeral 1 denotes a vibrator, which is mainly composed of nickel oxide, copper oxide, iron oxide
or the like, and made of a ferrite material sintered after compression molding. A winding 2
generates a magnetic field by applying a signal current to cause the vibrator 1 to generate a
magnetostriction phenomenon. However, the vibrator 1 is merely extended regardless of its
polarity if it only applies the signal current, but by providing the bias magnet 3, it is to be used in
addition to a constant static elongation. Therefore, by applying a signal current from the winding
2 that gives an alternating magnetic field that is sufficiently smaller than the magnetic field
provided by the bias magnet 3, the vibrator 1 generates minute vibrations. The vibrator 1 is
bonded to a so-called acoustic window 4 made of a material having good acoustic transparency,
and the generated nine vibrations pass through the acoustic window 4 and are emitted as sound
waves to water as a sound field medium. . In addition, 5 is a cylindrical watertight case. The
resonance frequency of this underwater transducer, ie the frequency with the highest acoustic
radiation efficiency, is uniquely determined by the shape of the vibrator 1, mainly by the length,
and it is impossible to electrically change the frequency. there were. Next, the resonant frequency
f. The range of good radiation efficiency around the center, the width of the ring is generally
around nineteen. In the field of underwater acoustics, it is most common to use several tens of
kilohertz as the sound wave frequency, but when transmitting sound waves at the resonance
frequency of the underwater transmitter-receiver, the bandwidth is 2k when the resonance
frequency is 20kH2. When transmitting a signal having a bandwidth greater than or equal to that
of the reed), the waveform of the sound wave is distorted in a form different from that of the
electric signal. Therefore, for example, in the case of an underwater telephone in which an audio
signal is AM-modulated and transmitted, there is a problem that it can not be said from the
viewpoint of faithful transmission. Furthermore, for applications that transmit signals requiring a
wide bandwidth, such as FM modulation, conventional underwater transducers are unsuitable.
There was no way to solve those problems. The present invention eliminates such conventional
defects, and some amorphous alloys show magnetostrictive effects, and pay attention to the
property that they change depending on the magnitude of the sonic air DC magnetic field among
them. Windings are applied to a vibrator using a magnetic body made of an amorphous alloy so
that direct current and low frequency current are applied. Hereinafter, an embodiment of the
present invention will be described in detail with reference to the drawings.
FIG. 2 is a partially cutaway plan view showing an embodiment of the variable resonance type
underwater transducer according to the present invention. In the figure, 21 is a vibrator made of
an amorphous alloy, in which thin plates of amorphous amorphous alloy mainly composed of
iron and conor + are laminated and heat-treated in a magnetic field @ 22 is a direct current And a
winding for applying a low frequency current, 23 is a winding for transmitting and receiving
signals, 24 is an acoustic window, 25 is a cylindrical watertight casing ◎ the oscillator 21 made
of this amorphous alloy is a vibration made of a ferrite material As in the case of the daughter, no
vibration proportional to the signal current is generated unless a bias magnetic field is applied.
Therefore, a direct current is applied by the winding 22 to apply a bias magnetic field. Although
the resonance frequency of the vibrator 21 is determined by the speed of sound in the
amorphous alloy and the shape of the vibrator, the speed of sound changes depending on the
strength of the DC magnetic field, so the resonance frequency also changes depending on the
strength of the bias magnetic field. Therefore, if the direct current applied to the winding 22 is
minutely changed to give a direct current bias magnetic field, the resonance frequency changes,
and therefore, a low frequency alternating current having a relatively small magnitude is added
to the direct current. The resonant frequency of the vibrator 21 changes in accordance with the
low frequency current. Since it is most efficient if signals are sent and received at the resonance
frequency, signals having the same frequency as the resonance frequency are sent and received
via the winding 23. The vibrator 21 is bonded to the acoustic window 24, and the generated nine
vibrations pass through the acoustic window 24 and are emitted as sound waves to water as a
sound field medium. The inside of the case is kept waterproof by the Z watertight casing 25. FIG.
3 is a diagram for explaining the operation of the transducer according to the present invention,
in which the vertical axis is the resonance frequency, the horizontal axis is the bias current, and a
low frequency current of frequency fp is superimposed on the direct current to change the
resonance frequency. Is shown. FIG. 4 is a diagram for explaining how the resonance frequency
reciprocates between the point A and the point B due to the effect of the low frequency current.
The vertical axis represents transmission sensitivity, and the horizontal axis represents
frequency. Therefore, when the resonance frequency is at point A, the most efficient transmission
can be carried out by applying an alternating current of the frequency at point A as a signal. The
same is true for point B (5), and it is most efficient to transmit an acoustic wave at that frequency
in response to changes in the resonance frequency. Thus, assuming that the resonance frequency
is not added electrically through the winding 22 and the resonance frequency when only a
certain level of DC current is added is fo, the frequency cos 2πf of the low frequency current is
converted to the DC current. When superimposed and added, the resonance frequency is in the
form of 10 + k cosz π / t.
It is to be noted that k is the most efficient if it is a proportionality constant and the signal
frequency is also the instantaneous frequency f + k cos 2π / p 1. This 10 + 5 c cos 2π /, 1 has
the same form as an instantaneous frequency of a frequency modulation signal where 10 is a
carrier frequency and jp is a modulation wave), to transmit and receive at this frequency means
to transmit and receive as a frequency modulation signal, For example, an underwater telephone
with a feature of frequency modulation such as applying low frequency current proportional to
voice signal and transmitting the same voice signal as frequency-modulated signal efficiently and
without distortion and excellent noise resistance Can transmit waves. In this case, since the
frequency 7O-1-k cos 2πfpt of the transmission signal and the (6) resonance frequency always
coincide with each other, there is no restriction due to the narrowness of the bandwidth as in the
conventional example. FIG. 5 is a block diagram of an example in which the underwater receiver
according to the present invention is applied to an underwater telephone. That is, the audio
signal detected by the microphone 51 is amplified by the preamplifier 52, is added to the direct
current I0 by the direct current adder 53, is amplified by the knock angle 54, and becomes a
current giving the bias magnetic field of the transmitter 55. Meanwhile, the frequency! The
carrier wave from the oscillator 56 oscillating at Lf 0 is modulated by the modulation wave from
the preamplifier 52 in the frequency modulator 57, amplified by the power amplifier 58, and
applied as a transmission signal to the transmitter 55, transmission The unit 55 transmits the
signal into water without distortion as described above. 59 is a normal-idrophone. Usually, since
the idrophone is broadband, it converts the received sound waveform into an electrical signal
without distortion. After being appropriately amplified by the pre-amplifier 60, the carrier
frequency signal from the local oscillator 61 is demodulated by the frequency demodulator 62, is
amplified by the amplifier 63, and is transmitted to the human ear through a single force 64.
Although a one-way block diagram is shown in this embodiment, it is needless to say that mutual
communication can be made by communicating in the same block diagram in the reverse
direction. In FIG. 2, although direct current and low frequency current are applied by one
winding, windings may be separately provided, or may be superimposed and applied to windings
for transmitting and receiving signals. Even if it produces the same effect. Also, since direct
current provides a bias magnetic field, it can be replaced by using a bias magnet as in the prior
art. Although the shape of the vibrator is shown as a so-called NA type, the same effect can be
obtained with a π type, a cylindrical type, a rod shape or the like. As described above in detail,
the present invention can change the resonance by applying a low frequency current to the
vibrator made of amorphous alloy, so that it can transmit the frequency modulation wave
efficiently, and hence it can be used for underwater communication etc. Have a great effect.
Brief description of the drawings
FIG. 1 is a partially cutaway plan view showing a conventional magnetostrictive effect
underwater transducer, and FIG. FIG. 4 is a diagram for explaining the operation of the present
invention, FIG. 4 is a diagram for explaining the effect of the same, and FIG. 5 is a ten-diagram
showing an underwater communication system using the underwater transducer according to the
present invention.
21: amorphous alloy vibrator, 22: winding for applying direct current and low frequency current,
23: winding for transmitting and receiving a signal, 24: acoustic window, 25: water casing (9)
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