JPS6240019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phased array sonar that reduces scan time per frame.

In a phased array sonar, a wave energy beam is transmitted and a reflected wave is received each time the azimuth is sequentially changed. Conventionally, in order to obtain one frame of echogram for each sound field being tested, the azimuth was successively changed (scanned) from a predetermined limit on one side to a limit on the other side. It takes time equal to the number of frame beams multiplied by the transmission/reception time per time to obtain an echogram signal. The time for one transmission and reception is a fixed value based on the propagation speed of wave energy in the medium, so if you try to shorten the frame time, you will reduce the number of beams in one frame, but this will reduce the resolution of the echogram. make it worse

SUMMARY OF THE INVENTION An object of the present invention is to provide a phased array sonar that reduces scanning time per frame without deteriorating echogram resolution.

The present invention provides, as a beam steering means,
By using two variable delay line groups exhibiting mutually complementary phase shift characteristics and operating them simultaneously, waves are transmitted and received simultaneously at two azimuthal angles that are symmetrical to each other.

The present invention will be explained below with reference to the drawings. The diagram is
1 is a conceptual configuration diagram of an embodiment of the present invention. In the figure, TD is an array transducer, consisting of, for example, 16 to 32 elements. AM is a bidirectional amplifier group, DL ₁ and DL ₂ are a pair of variable delay line groups, PG is a transmit pulse generator, AD ₁ ,
AD ₂ is a pair of summing amplifiers.

A pair of variable delay line groups DL ₁ and DL ₂ are
Corresponding individual delay lines are connected at a common end and are controlled to exhibit mutually complementary phase shift characteristics with respect to this common connection point. Incidentally, such a pair of variable delay line groups can also be realized by selecting the taps of one bidirectional variable delay line group of tap switching type. In that case, the phase shift characteristics should be complementary around the selected tap.

The common connection point of the variable delay line groups DL ₁ and DL ₂ is connected to the array line through the bidirectional amplifier group AM.
Each element of transducer TD is connected. The output signal of the transmission pulse generator PG is commonly applied to the other ends of the variable delay line groups DL ₁ and DL ₂ . The other ends of the variable delay line groups DL ₁ and DL ₂ are also connected to input terminals of summing amplifiers AD ₁ and AD ₂ , respectively.

The operation of the device configured in this way is as follows. When the transmission pulse generator PG applies one transmission pulse to each other end of the variable delay line groups DL ₁ and DL ₂ , the variable delay line group
The common connection point of DL ₁ and DL ₂ has individual delay
A group of pulses appears, each delayed according to the delay time of the line. There are two groups of pulses, one coming from the left and the other coming from the right. The phase shifts of these two groups of pulses are complementary according to the characteristics of the delay lines they have passed through. When such pulse groups are applied to the array transducer TD through the bidirectional amplifier group AM, the array transducer TD emits two wave beams with combined directivity according to each pulse group. do. These two wave beams have azimuthal angles that are symmetrical to each other as shown in the figure due to the complementarity of the phase shift states of the two pulse groups.

When reflected wave signals based on these beams enter each element of the array transducer TD, the input signal of each element is transmitted to a group of bidirectional amplifiers.
Through the AM, it is guided to the common connection point of the delay line groups DL ₁ and DL ₂ , where it branches to the left and right,
The signals are transferred according to the characteristics of each delay line group, and summed and amplified by summing amplifiers AD ₁ and AD ₂ , respectively. As a result, the reception of the two reflected wave signals is performed by adjusting the reception directionality to the azimuth angle of the two beams at the time of wave transmission. These received signals are applied to the next stage of circuitry, such as a buffer memory for display.

Next, the distribution of delay times in the variable delay line groups DL ₁ and DL ₂ is changed to set new azimuth angles that are symmetrical to each other, and the same operation as above is performed. Thereafter, wave transmission and reception are repeated while sequentially switching the azimuth angle in this manner.

In such a device, two symmetrical directions are scanned at once, so the scan time required to obtain one frame of echogram is
Comparing the same exploration area, the time is half that of the conventional method, and there is no drop in resolution.

In this way, the present invention uses two variable delay line groups exhibiting mutually complementary phase shift characteristics as beam steering means, and by operating these groups simultaneously, the transmitted and received waves are controlled by two symmetrical delay line groups. It is now possible to do this at the same time in azimuth.
Therefore, the scan time per frame can be shortened without reducing the resolution of the echogram.

[Brief explanation of the drawing]

The figure is a conceptual configuration diagram of an embodiment of the present invention. TD...Array transducer, AM...
Bidirectional amplifier, DL ₁ , DL ₂ ...Variable delay line group, PG...Transmission pulse generator, AD ₁ , AD ₂
...Summing amplifier.

Claims (1)

[Claims] 1. A wave energy beam is transmitted by driving an array transducer through a variable delay line group, and when the array transducer receives a reflected wave, the variable delay line is - In a phased array sonar that performs beam steering by receiving waves through a line and transmitting and receiving waves by changing the distribution of delay times of a variable delay line group, the variable delay line group A variable delay line that has an intermediate tap to which each element of the array transducer is connected, uses a plurality of variable delay lines each having the same total delay time, and is divided into two by the intermediate tap.・The other ends of the lines are connected in common, and the two delay line groups exhibit mutually complementary phase shift characteristics at the commonly connected point,
and a pair of variable delay line groups configured such that the transmitting pulses are simultaneously applied to the commonly connected points during wave transmission, and the pair of variable delay line groups are operated substantially simultaneously. This is a phased array sonar that transmits and receives waves at two azimuth angles that are symmetrical about the center.