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Description 1, title of the invention
Ultrasonic transducer
3. Detailed Description of the Invention The present invention relates to an ultrasonic transducer
used in a fish finder, a scanner and the like, and more particularly to an improvement in the
arrangement of transducers. In general, the principle of detecting underwater objects with a
scanning scanner or the like is as shown in FIG. 1 when considered on a plane. That is, at first the
home ultrasound transducer or l? Corrected acoustic waves are transmitted in all directions 360.
Fig. 1 (a)-). When receiving '', a sharp single beam is formed and this beam is sequentially
switched at high speed (Fig. 1 (b). A method of scanning all directions and determining the
distance and direction from the reflected signal to the underwater object is taken. Therefore, it is
necessary to emit sound waves in all directions at the time of emission, and at the time of
reception, to form a sharp beam without side lobes in order to improve the orientation accuracy.
Conventionally, in this type of transducer, as shown in FIG. 2 (a), 平面), a large number of
elements are arranged in order on a certain plane or cylinder, and when transmitting, part or all
of them are arranged. The transmission ultrasonic signal is supplied to the elements of S, and the
reception signals obtained by those elements are added and synthesized at the time of reception
to create a reception signal, in which case a desired beam width and side rope can be obtained. In
many cases, "weighting" or the like is performed on the signal obtained from each element. Here,
the directivity of the sound wave will be described. FIG. 3 is a diagram showing the directivity
characteristic when two transducers are arranged on a straight line, and the center distance of
the transducers is λ / 2EndPage: 1 (λ is a wavelength) It is clear that when the directivity is the
best in terms of sidelobe suppression. When a plurality of transducers are arranged to obtain a
desired beam width, the optimal spacing of the transducers can take various values. Therefore, in
the present case, the element spacing is as follows for the arrangement of the transducers as an
example. As described above, in the arrangement of the transducers, it is preferable to use the
use frequency in terms of sidelobe suppression, but since the element size of the ultrasonic
transducer is generally larger than λ / 2, the element spacing is λ If it was reduced to 2/7, etc.,
7 could not be obtained, and it could not but compromise with the side lobe ratio obtained by a
certain appropriate weighting given to each element, or had to make a special oscillator whose
radiation surface dimension is λ / 2. However, in the former case, it is difficult to obtain a
sidelobe attenuation of 20 dB or more for the main beam, which is a design target for ordinary
sonar etc. In the latter case, even if an element of λ / 2 is made There was a drawback of being
very expensive. Furthermore, when arranging these elements in a cylindrical shape, the number
of elements that must be arranged on the circumference is determined from the required beam
width, not only the side lobe point but also the equipment point to the ship In consideration of
the above, it is desirable to make the required number of elements per stage correspond to each
stage and to make the radius of the cylinder as small as possible.
However, in this case, of course, in the case of an element having a large height (such as a
general ferrite vibrator or a Langevin type vibrator), as shown in the enlarged cross-sectional
view of (1) in FIG. However, even in the case of a relatively low-height one such as a ring
oscillator, the elements will collide with each other when placed on a small radius cylinder
(hatched portion in FIG. 2 (c)), the radius of the cylinder There was a drawback such as having to
make the In order to eliminate these drawbacks, the present invention arranges the elements in a
staggered manner and interpolates the gaps in an electric circuit, which will be described in
detail below with reference to the drawings. FIG. 4 is a view showing an embodiment of a
cylindrical array of transducers according to the present invention, in which white circles and
black circles are both ultrasonic transducers of the same type, and the radiation surface
dimension is at least λ / 2. . In the case of such a cylindrical array, it is often used for scanning
scanners, so here 'is considered the case of omnidirectional transmission with 360 degrees
horizontal transmission, and reception forms a sharp single beam It explains as a thing. The
figure shows eight steps alternately (that is, in a staggered manner) so as to fill the gaps of the
cylinders. As a result, it is equivalent to the case of acoustically arranging 36 elements on the
circumference and 8 steps in the longitudinal direction, in which case the element spacing can be
λ / 2. First, considering the dimension, as apparent from the longitudinal direction 7 shown in
the enlarged view (a) of FIG. 5 and the circumferential direction view shown in (b), the radiation
surface dimension is λ / 2 or more It is possible to arrange the elements together at a spacing of
λ / 2, so that the radius of the cylinder can also be made significantly smaller than in the prior
art. Next, the directivity of sound waves is considered. (1) Directionality of transmission (a) Since
the same number (four each) of white circle elements and black circle elements are vertically
aligned in the vertical direction, the directivity is lined up with eight element lines at λ / 2
intervals It can be considered identical to (B) As shown in FIG. 4, in the horizontal direction, the
directivity of each stage is transmitted in a non-directional manner, so there is no difference from
the case where 36 elements are arranged on the circumference for each stage. As described
above, the directivity of transmission is acoustically equivalent to the case where the elements
are arranged every λ / 2 around the entire circumference of one cylinder. (Ii) Reception
directivity As described above, the directivity of reception needs to form a sharp beam to
determine the direction. (A) As shown in FIG. 6 (a), the vertical direction is symmetrical with
respect to the base reference axis in order to interpolate the black circle mark element gap (the
element position corresponding to the ▪ mark in the figure) when considered on the reference
axis in the figure. If the weights of the bars are added to the received signals from two white
circle elements and added, the delay amount (phase amount ■) given for Beam-8 j: eering in the
vertical direction is EndPage: 2 white circles, black circles are Since they are the same, they are
equivalent to directivity in which eight elements are linearly arranged at λ / 2 intervals.
(B) As is clear from FIG. 6 (1), the directivity in the horizontal direction is different in the
horizontal phase compensation amount {circle over (4)} given to each element lined up on the
circumference, but as shown in FIG. When the signals received by elements on the left and right
sides with respect to the axis being considered are also on-axis one, the weight of the rod is given
and added to the received signal by the on-axis element Since the elements can be interpolated,
the calculation can be performed by considering the output of the adder 1 after this interpolation
as the directivity of a single unit in the normal case. If the beam width is wider than desired, the
product array method or sum difference may be weighted. Two or more have been described in
the case where the staggered arrangement is applied to the cylindrical arrangement, but this
applies not only to the number of elements arranged, but also to the arrangement in the
cylindrical arrangement, and applies to the planar arrangement with exactly the same idea There
is nothing to be able to do. In addition, although only omnidirectional transmission and single
beam reception have been described in the description, it is easy to create a single beam or a
plurality of beams having directivity both in transmission and reception without being limited
thereto. '' In Figure 6 It is needless to say that the '+, -g calculator 1 may be synthesized using
another small stage such as a transformer, etc., not limited to an adder such as an operational
amplifier. As described above, if the elements are arranged in a staggered pattern and
interpolation is performed by an electric circuit at the time of reception, the elements can be
arranged at intervals smaller than the element width emitting surface size, which is excellent in
point of. Furthermore, when placed on a cylinder, its radius can be made extremely small, the
number of elements used can be reduced by half, and it is economical, and acoustically large
elements can be arranged at a distance smaller than the element size. Equivalent characteristics
can be obtained.
4. Brief description of the drawings. 1 FIG. 1 shows sonar scanning, FIG. 2 shows a conventional
arrangement of transducers, FIG. FIG. 5 is a diagram showing the arrangement of transducers
according to the present invention, FIG. 5 is a partially enlarged view of FIG. 4, and FIG. 6 is a
diagram showing the state of interpolation at reception. 1 ... Adder 0 Patent applicant Japan
Radio Inc. EndPage: 3 Fig. 1 Fig. 2 Fig. 4 Fig. 5 Fig. 6 Fig. End Page: 4