JPH04326082A - Ultrasonic wave receiving and phasing circuit - Google Patents

Abstract

PURPOSE:To realize the title circuit suppressing the generation of a large side lobe and simultaneously forming a plurality of beams in relatively reduced apparatus cost. CONSTITUTION:The receiving signals of arranged elements e0-e9 are selected by switches w0-w9, w10-w19 to be connected to signal bundling circuits 1, 2 at every groups mutually having overlap. Delay distribution is imparted to the outputs respectively set to single signals by the bundling circuits 1, 2 in delay part 4, 5 and the signals after delay processing are mutually added in adder parts 6, 7 to form two receiving beams bm2, bm3 mutually different in polarizing direction. The directional side lobe of the element group itself bundled by the signal bundling circuits can be shifted from the directional side lobe due to the delay processing between bundling outputs and the side lobe of the receiving beam determined by the product of both directivities can be suppressed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic scanning ultrasonic diagnostic apparatus and an ultrasonic imaging apparatus, and more particularly to an ultrasonic receiving phasing circuit that simultaneously forms a plurality of ultrasonic beams.

0002

[Prior Art] Conventionally, an electroacoustic transducer emits an ultrasonic signal toward the inside of the body, and the electroacoustic transducer receives the returned ultrasonic signal after being reflected at tissue boundaries. The ultrasonic beam was formed by delaying it using a phase circuit. JP-A-62-12852 discloses that a certain beam forming process is performed on each group of received signals obtained from each of the arrayed electroacoustic transducer elements, and delay processing is applied to the signals of each group to simultaneously generate signals. Receive beams in multiple directions
A method for forming a system is described.

0003

In the prior art described above, when a plurality of received signals are divided into a plurality of groups, one received signal belongs to only one group. Furthermore, weighting cannot be performed when dividing the received signal into groups. As a result, there is a problem in that unnecessary responses (ie, side lobes) occur strongly. This will be explained using figures. FIG. 2 is a diagram showing the configuration of a device according to the prior art in which received signals are bundled, a phasing process is performed on the bundled signals, and a plurality of beams are simultaneously formed. In Figure 2, eight signals (s1 to s8) are
The case of dividing into groups (A1, A2) is shown. In FIG. 2, 1 and 2 are signal bundling circuits, 3 is an addition section, 4 and 5 are delay sections, and 6 and 7 are addition sections. For example, assume that eight signal lines are divided into two groups (A1, A2) by bundling four signal lines each. At this time, the bundled signals are considered to be the same signal,
After that, processing will be performed on two signals. As a result, 8
Since the device size of the signal delay section is reduced to 1/4 compared to the case where real signals are handled independently, the device can be made compact.

In the apparatus shown in FIG. 2, an adding section 3 forms an ultrasonic beam bm1 having directivity in the front direction. In addition, in this example, since a frontal ultrasound beam is formed from two signals from two groups of conversion elements, only two
Add signals without any delay time difference. However, in general,
Since an ultrasonic beam is formed that converges within a finite distance from the received signals of three or more conversion element groups, it is necessary to give a delay time difference to the beam formation in the front direction. In some cases, a delay section is provided in the section. At this time, the directivity of bm1 is determined by the directivity corresponding to each group divided according to the multiplier law, and the point sound source array (strictly speaking, the point-shaped array of wave receiving elements) placed at the midpoint of each group. It is found as the product of the directivity when focusing in the direction. At this time, the directivity corresponding to each group is the directivity of a line sound source having an element width equal to the number of bundled signals. Here A1
, A2, since four signals are bundled together, this is the directivity of a line sound source with a width of four elements, and this width is set as D. Furthermore, the point sound source array placed at the midpoint of each group refers to the point sound source array placed at the center position of the element group corresponding to the signal bundled in each group. There are two point sound sources lined up. The directivity corresponding to each divided group is R1, and the directivity when focusing in the front direction by a point sound source array placed at the midpoint of each group is R2.
Then, R1=｜sinx/x｜・・・・・・・・・
・・・・・・・・・・・・(1) R2=｜sin2x
/2sinx｜=｜cosx｜ ・・・・・・・・・
...(2). However, x=πDsinγ/λ, λ
is the wavelength, and γ is the angle from the front direction.

The characteristics of R1 in the above equation are shown in FIG. 4, and the characteristics of R2 are shown in FIG. Note that the directivity is normalized with the front direction as 1, and the horizontal axis is sin γ. bm1 directivity to R3
Then, R3=R1×R2=｜sin2x/2x｜...
......(3). The characteristics of R3 are shown in FIG. In FIG. 6, M is a main lobe and G is a side lobe which is an unnecessary response, and G needs to be made sufficiently smaller than M. At this time, the biggest cause of sidelobes is the maximum value in R2 other than the front direction (sin γ = 0), but when forming an ultrasonic beam on bm1, R
The local maximum values other than those in the front direction of R2 are all canceled because they coincide with the zero point of R1, and as a result, no large side lobe is generated in R3. Meanwhile, at the same time, the delay units 4, 5 and addition units 6, 7 in FIG.
make. That is, when the receiving element is located at the center point of each group described above, the delay units 4 and 5 give a delay time difference to the two signals so as to obtain respective directivities. Focusing on the directivity of bm2, from the multiplier law, the directivity corresponding to each divided group and the point sound source array placed at the midpoint of each group connect the focus to the right at an angle δ from the front. It can be found as the product of the directivity when At this time, the directivity corresponding to each divided group is equal to R1 shown above. Furthermore, when the point sound source array placed at the midpoint of each group is focused from the front to the right at an angle δ, the directivity R4 is obtained by shifting R2 to the right by sin δ, as shown in Figure 7. Equal to gender. In other words, R4=|cos(x−πDsinδ
/λ) | ・・・・・・・・・・・・・・・(4). Therefore, if the directivity of bm2 is R5, then R5=
R1×R4 = | (sinx/x)cos(x−πDs
inδ/λ) | (5). For example, if δ=0.2 (deg), frequency is 3.5 MHz, and diameter is 30 mm, sin δ≈λ/4D, and R5 becomes as shown in FIG. 8. R5 has larger side lobes than R3. This is because the local maximum value of directivity in R4 is shifted to the right compared to R2, so that it is no longer canceled out at the zero point of R1. Even when the beam is made into BM3, the same thing holds true for left-right symmetry. In this way, in simultaneous formation of a plurality of beams, side lobes become a major problem when forming beams bm2 and bm3.

Furthermore, as an apparatus configuration for simultaneously forming a plurality of beams, a configuration as shown in FIG. 3 is also known. In FIG. 3, 8 is a first delay section a, and 9 is a first delay section b. At this time, bm2 and bm3 are generated by the two first delay sections.
Two ultrasonic beams are created simultaneously. In this case b
No ultrasonic beam is formed on m1, but bm2
The directivity is still R5, and large side lobes occur. The purpose of the present invention is to
The object of the present invention is to realize an ultrasonic wave receiving phasing circuit that suppresses the occurrence of beams and simultaneously forms a plurality of beams at a relatively low device cost.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the ultrasonic wave reception phasing circuit of the present invention has the following features: (a) A plurality of reception signals from individual array elements are bundled and divided into a plurality of groups. When doing so, the ultrasonic reception phasing circuit is characterized in that it can assign the reception signal of one element to any one or more groups. Specifically, (b) it has a signal bundling circuit that bundles individual received signals from arrayed element groups into multiple received signal groups from element groups that overlap with each other, and further includes a signal bundling circuit that bundles individual received signals from arrayed element groups into multiple received signal groups from element groups that overlap each other, and Another feature of the ultrasonic reception phasing circuit is that it is provided with a plurality of sets of delay units and addition units that add a delay time distribution to the ultrasonic reception beams, and simultaneously obtains reception beams with different directivity from the respective addition outputs. Furthermore, (c) a weighting circuit that performs weighting corresponding to the element arrangement for each group of multiple received signals, a signal bundling circuit that bundles the weighted received signal groups, and a delay for the multiple bundled signals. Another feature is the configuration that includes multiple sets of delay units and addition units that add time distributions.

[0008]

In the present invention, in order to bundle received signals from a plurality of elements into groups of received signals, the received signals of one element are made to belong to one or more arbitrary groups. In this way, when forming an ultrasonic beam (receiving beam) that gives a delay time distribution to each bundled output and converges in a desired direction away from the front, a point can be placed at the center of each group. Assuming that there is a sound source (a point-like receiving element), the side-low of the directionality caused by the above delay time distribution is
The beam can be aligned with the trough of the directivity of each element group, and unnecessary responses (side lobes) of the ultrasonic beam determined by the product of both directivities can be reduced. Therefore, in order to simultaneously obtain a plurality of ultrasonic beams having different directions, it is possible to realize an ultrasonic phasing device with small unnecessary responses (side lobes) while reducing the device size of the delay part by bundling. In addition, in a configuration in which a weighting circuit is provided for each group, the directivity side-lower of each element group itself is
Since the lobes can be made smaller, it is also possible to obtain an ultrasonic phasing device with small unnecessary responses (side lobes).

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the configuration of an ultrasonic receiving phasing circuit which is an embodiment of the present invention. Here, a case is shown in which 10 signals are divided into two groups. In Figure 1, e
0 to e9 are electroacoustic transducer elements to be arranged, s0 to s9 are received signals obtained individually from each element, w0 to w19 are switches, 1 and 2 are signal bundling circuits, A1 and A2 are bundling circuits 1 and 2, respectively. Name of the received signal group bundled by 4
and 5 are delay units, and 6 and 7 are adder units. In FIG. 1, first, the signals to be input to the two signal bundling circuits 1 and 2 are determined by selectively closing the switches w0 to w19. Therefore, the received signals of each element are A1, A2
You can enter either. Signal bundling circuit 1 is a switch w
After amplifying the received signals selected in 0 to w9 individually, the received signals are combined into one signal by current addition. The signal bundling circuit 2 similarly bundles the received signals selected by the switches w10 to w19. The delay units 4 and 5 form ultrasonic beams bm2 and bm3 in different directions from the outputs of the signal bundling circuits 1 and 2, respectively. That is, in the delay unit 4, the ultrasonic beam bm2 is generated from the received signals of the two dot-like elements located at the center of the element group corresponding to the signal group A1 and the element group corresponding to the signal group A2. As much delay time difference as can be obtained is given to the outputs of the signal bundling circuits 1 and 2. An adding section 6 adds the signals that have passed through the delay section 4 to form an ultrasonic beam bm2. Further, the delay unit 5 also provides the outputs of the signal bundling circuits 1 and 2 with a delay time difference sufficient to obtain the ultrasonic beam bm3 from the two point-like elements, and furthermore, the adder 7 applies a delay time difference sufficient to obtain the ultrasonic beam bm3 from the two point elements. get. Note that bm2 and bm3 are ultrasonic beams deflected to the right and left by a small angle δ from the front direction (bm1). From here on, we will focus on the directivity of bm2. Based on the multiplier law, the directivity of bm2 is based on the directivity corresponding to each group divided by the switch, and the point sound source array placed at the midpoint of each group, which connects the focus to the right by an angle δ from the front. It can be found as the product of the directivity when

Now, the switches w0 to w5 are turned on, the switches w6 to w13 are turned off, and the switches w14 to w19 are turned on. In other words, among the element arrays e0 to e9, the received signals from e0 to e5 are bundled by the signal bundling circuit 1, and e4 to e9
The received signals are bundled by the signal bundling circuit 2, and as a result, e4 and e5 are made to overlap in two element groups. Then, the directivity of bm2 at this time is determined. First, since the number of signals input to each signal bundling circuit 1 or 2 is six, the directivity corresponding to each group becomes the directivity of a line sound source having a width of six elements. In FIG. 2, the width of four elements is set as D, so in this case of FIG. 1, the directivity is that of a line sound source with a width of 3D/2. If this is designated as R6, the characteristics of R6 will be as shown in FIG. 9, and the formula is R6=|sin(3x/2)/(3x/2)|
・・・・・・・・・・・・(6). Next, since the distance between the center points of each element group is the width D of four elements as in the case of FIG. The directivity when it is set is R4 shown above. Therefore, if the directivity of bm2 is set as R7, R7=R6×R4 =|(sin(3x/2)/(3x/2)
)cos(x−πDsinδ/λ)｜・・・・・・(7
). x=πDsinγ/λ, where λ is the wavelength and γ is the angle from the front direction.

The characteristics of R7 are shown in FIG. The directivity is normalized with the front direction as 1, and the horizontal axis is sinγ.
And so. Moreover, sin δ=λ/4D. R4 and R6
, there is little overlap between the side lobes, and as a result, R7
It can be seen that the side lobe indicated by G is smaller than that of R5. This reduction in side lobes is caused by
This can also be seen with the ultrasonic beam bm3, which is focused at an angle deflected to the left by δ from the front.In the end, two ultrasonic beams with less unnecessary responses (side lobes) can be formed at the same time, resulting in high High-quality ultrasound images can be obtained. In the above embodiment, two signal bundling circuits are used to bundle the received signals from the element groups into two groups, but three or more signal bundling circuits are used to bundle the received signals from the element groups. It is also possible to have a configuration in which each bundled circuit is bundled. On the other hand, the number of ultrasonic beams simultaneously obtained by using the outputs of these signal bundling circuits, that is, the number of delay sections provided in parallel, may also be three or more. In any case, the above effect can be obtained by bundling received signals from a plurality of elements into a plurality of groups that overlap with each other. However, the optimum group width or the width of the overlap of the bundles changes depending on the deflection angle δ of the ultrasonic beam to be formed. The embodiment of FIG. 1 has the advantage that by employing the switches w0 to w19, the optimum group width or bundle overlap width can be selected in accordance with the deflection angle δ.

FIG. 11 is a diagram showing an ultrasonic receiving phasing circuit according to another embodiment of the present invention. In this embodiment, the received signals s1 to s8 of the eight array elements e1 to e8 are bundled by four signal bundle circuits 1 and 2 each. In other words, there is no overlap in the bundling of each group. Instead, the received signals s1 to s4 are input to the signal bundling circuit 1 via the weighting circuit 10, and the received signals s
5 to s8 are configured to be input to the signal bundling circuit 2 via the weighting circuit 11. The configuration after the delay section is the same as that in FIG. Weighting circuits 10 and 11 each apply triangular weights to the received signal group. The triangular weight is the first
As shown in Figure 2, this is a weight that is largest at the center and decreases linearly toward the ends. In FIG. 12, received signals from five elements are shown for ease of understanding. The delay units 4 and 5 give a delay time difference sufficient to focus the two outputs of the signal bundling circuits 1 and 2 at angles deflected left and right by δ, respectively, as shown in FIG.
The same is true for . Therefore, the directivity due to the point sound source array located at the midpoint of each group is R4 (
Figure 7). However, by giving triangular weights to each received signal, the directivity corresponding to each group of bundled signals is determined by the directivity R1 of a line sound source with an element width equal to the bundled signal (Fig. 4). It becomes the square of In other words, the directivity R8 of each group
is, R8=R12=|(sinx/x)2| ・
(8), and as shown in FIG. 13, the side lobe is lower than R1. The directivity R9 of the ultrasonic beam bm2 obtained by the adder 6 is determined by the multiplier law: R9=R8×R4 =|(sinx/x)2cos(x−
πDsinδ/λ) | (9), and the side lobe G is smaller than the directivity R5 of the ultrasonic beam obtained without giving triangular weights as shown in FIG. . However, sin δ=λ/4D. In this way, weighting multiple signal groups to be bundled to reduce side lobes due to beam deflection is not limited to triangular weighting, but also by reducing the weight of the signals at the ends of the bundle. Other shapes of weighting can also be effective.

FIG. 15 is a diagram showing yet another embodiment of the present invention. This embodiment uses both the overlapping bundling employed in FIG. 1 and the weighting circuit employed in FIG. 11. That is, the received signals of the elements e0 to e5 are bundled by the signal bundling circuit 1 via the weighting circuit 10. Further, the received signals of the elements e4 to e9 are bundled by the signal bundling circuit 2 via the weighting circuit 11. In this way, the signal groups A1 and A2 overlap and are given weight distributions respectively. In this case as well, the directivity of the ultrasonic beam bm2 obtained by the adder 6 is determined by the multiplier law. First, when a point sound source array placed at the midpoint of each group is focused at an angle deflected to the right by δ from the front, the directivity is R4. Directivity corresponding to each group (R1
0) is the square of the directivity R6 of a line sound source with a width of 3D/2, which is the directivity of each group when no triangular weight is applied.
R10=R62=|(sin(3x/2)/(3x
/2))2| ......(10). Therefore, the directivity of bm2 (set as R11) is R11=R1
0xR4 = | (sin(3x/2)/(3x/
2))2cos(x-πsinδ/λ) | ・・・・
-(11). The characteristics of R10 are shown in Figure 16, and the characteristics of R1
The characteristics of No. 1 are shown in FIG. Here, sin δ=λ/4
It was set as D. In this way, the strength of the side lobe G can be significantly reduced by combining the configuration of bundling into signal groups that overlap with each other and applying a predetermined weight to each signal group.

[0014] In the above embodiments, the methods used to reduce the side lobes are common to each group (
By changing the directivity corresponding to A1, A2), the maximum value of the directivity (however, Maximum value of the side lobe near the main lobe)
It means canceling out. Note that the number of signal lines, dividing groups, delay sections, addition sections, and simultaneously formed beams are not limited to the numbers shown in the embodiments. Furthermore, the weights given by the weighting section are not limited to triangular weights, but may also be Hanning weights or the like.

[0015]

[Effects of the Invention] As described above, according to the present invention, a plurality of received signals are divided into a plurality of groups by bundling them, and a plurality of received signals are subjected to delay processing on these bundled received signals. In an ultrasonic receiving phasing circuit that is equipped with a delay section and forms ultrasonic beams in multiple directions simultaneously, it is possible to suppress increases in side lobes due to signal bundling and beam deflection. It becomes possible to obtain high-quality ultrasound images with a small circuit scale.

[0016]

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ultrasonic receiving phasing circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional ultrasonic receiving phasing circuit.

FIG. 3 is a block diagram showing another example of a conventional ultrasonic receiving phasing circuit.

FIG. 4 is a characteristic diagram showing the directivity of each element group in a conventional example.

FIG. 5 is a characteristic diagram showing the directivity of the adder 3 in the conventional example.

[Fig. 6] Frontal ultrasound beam bm obtained by conventional example
FIG. 1 is a characteristic diagram showing the directivity of No. 1;

FIG. 7 is a characteristic diagram showing the directivity of a conventional delay unit 4;

[Fig. 8] Deflected ultrasonic beam bm2 obtained by conventional example
FIG.

9 is a characteristic diagram showing the directivity of each element group in the embodiment of FIG. 1. FIG.

10 is a characteristic diagram showing the directivity of the deflected ultrasonic beam bm2 obtained by the embodiment of FIG. 1. FIG.

FIG. 11 is a block diagram of an ultrasonic receiving phasing circuit according to another embodiment of the present invention.

FIG. 12 is a characteristic diagram showing the weight distribution of the weighting circuit in the embodiment of FIG. 11;

FIG. 13 is a characteristic diagram showing the directivity of each element group in the embodiment of FIG. 11;

14 is a characteristic diagram showing the directivity of the deflected ultrasonic beam bm2 obtained by the embodiment of FIG. 11. FIG.

FIG. 15 is a block diagram of an ultrasonic receiving phasing circuit according to still another embodiment of the present invention.

16 is a characteristic diagram showing the directivity of each element group in the embodiment of FIG. 15. FIG.

17 is a characteristic diagram showing the directivity of the deflected ultrasonic beam bm2 obtained by the embodiment of FIG. 15. FIG.

[Explanation of symbols]

bm1 to bm3: ultrasonic beam, s0 to s9: signal line,
w0 to w19: Switch, A1, A2: Name of divided received signal group, G: Side lobe, M: Main lobe, T
: Element that performs beam formation, 1, 2: Signal bundling circuit, 4,
5: delay section, 6, 7: addition section, 10, 11: weighting circuit

Claims (4)

[Claims] 1. An ultrasonic receiving phasing circuit that gives a delay distribution to a plurality of received signals from a plurality of arranged electroacoustic transducing elements to form an ultrasonic beam having directivity in a predetermined direction, comprising: a plurality of signal bundling circuits that bundle the plurality of received signals into a plurality of groups into a single signal; Connecting means comprising a plurality of sets of delay units and adder units for forming ultrasonic beams, and capable of simultaneously connecting each of the plurality of received signals to any one or more of the plurality of bundling circuits. An ultrasonic receiving phasing circuit featuring: 2. An ultrasonic receiving phasing circuit that provides a delay distribution to a plurality of received signals from a plurality of arranged electroacoustic transducing elements to form an ultrasonic beam having directivity in a predetermined direction. a plurality of signal bundling circuits that bundle a plurality of received signals into groups that overlap each other to form a single signal; An ultrasonic receiving phasing circuit comprising a plurality of sets of delay sections and adder sections that form ultrasonic beams with different directivities. 3. An ultrasonic receiving phasing circuit that provides a delay distribution to a plurality of received signals from a plurality of arranged electroacoustic transducing elements to form an ultrasonic beam having directivity in a predetermined direction. a plurality of weighting circuits that give predetermined weight distributions to each of the plurality of groups of the plurality of received signals; a plurality of signal bundling circuits that bundle the signal groups that have passed through the respective weighting circuits into a single signal; An ultrasonic receiving waveform generator comprising a plurality of sets of delay sections and addition sections that give different delay distributions to the outputs of the signal bundling circuits and add them to form ultrasonic beams each having a different directivity. phase circuit. 4. The plurality of received signals are inputted to the plurality of weighting circuits in groups having mutual overlap, thereby forming a bundle of signal groups having respective overlaps. The ultrasonic receiving phasing circuit according to item 3.