JPS6022744B2 - Frequency shift signal detection device - Google Patents

Description

[Detailed Description of the Invention] The present invention emits ultrasonic waves into the sea from a base installed on the seabed or a ship parked on the sea, and the reflected waves from water masses (reflecting objects that move with water flow, such as plankton) at a predetermined depth are detected. This technology relates to detecting the Doppler component of water and measuring current speed, etc.

Conventionally, this type of measuring device can measure speeds as low as 1 centimeter per second. If present, Doppler components caused by these will act as noise on the original water flow,
The indicated value becomes unstable. The present invention eliminates these drawbacks by measuring only the portion where the reflected wave maintains a constant frequency.

Next, the present invention will be explained with reference to examples.

In Fig. 1, 1' is a high-frequency oscillator that generates continuous waves in the ultrasonic range, and 2 is a high-frequency oscillator that gates the output of the high-frequency oscillator with regular pulses, and periodically generates a pulse signal as shown in Fig. 2a. It is a pulse oscillator that generates.

3 is an intensifier.

4 is a transmitting/receiving sliding door circuit, 5 is an ultrasonic transducer, and 6 is an intensifier for the received wave.

Reference numeral 7 denotes a waveform shaping circuit, which is composed of an intensifier and an oscillation limiter.

8 is a vibration converter that converts a change in frequency into a change in vibration.

For these, an input circuit of a voltage controlled oscillator of a general-purpose PLL oscillator may be used, or a Foster-Seeley circuit or a ratio detector may be used. 9 is a differentiating circuit, and 101 is a monostable circuit, which is composed of a pair of monostable circuits that respond to both positive and negative input signals, and outputs a sum signal of both.

11 is a depth gate wave generator, which is a cascade-connected 2
The first monostable circuit creates a depth pulse (not shown) at a predetermined time delay position by controlling its time constant, and the second monostable circuit creates a depth pulse (not shown) at a predetermined time delay position by controlling its time constant. A rectangular wave g that lasts for a predetermined time T from its generation position
Create.

12 is a sample gate wave generator, which includes a monostable circuit 1
It is constituted by an AND gate of the inverted waveform of the output of 0 and the depth gate wave g.

13 is a gate circuit.

Reference numeral 14 denotes a velocity calculation display which shapes a discontinuous signal into a continuous signal having the same frequency component, and further detects and displays a Doppler component from the difference with the output of the high frequency oscillator 1. Since this is a well-known technique, the details will be omitted.

In the above apparatus, the pulses generated by the pulse oscillator 2 (FIG. 2a) are multiplied by the multiplier 3 and then supplied to the ultrasonic transducer 6 via the transmission/reception switching circuit 4. The transducer emits ultrasonic pulses in the direction of travel and diagonally underwater, receives the reflected waves, converts them into electrical signals, and sends them to the multiplier 8.
supply this. Figure 2b shows the reflected signals sequentially reflected from the microorganisms in the water soul, and has a length corresponding to the power of the ultrasonic pulse.This received signal is processed by the waveform shaping circuit 7 as shown in Figure 2c. The signal is shaped into a constant oscillation signal.
The output b of the intensifier S is converted by the intensifier converter 8 into an anag wave as shown in FIG. 2d.

Here, D] and D2 indicate a frequency fluctuation part where the reflected wave is received from an object that moves differently from the water flow. Next, the output d of the oscillating converter 8 is differentiated by a differentiating circuit 9 as shown in e. In other words, only parts with rapid frequency fluctuations are selected. The output of the differentiating circuit 9 is supplied to a monostable circuit 181,
Here, waveform shaping is performed as shown in FIG. 2f. The output of the monostable circuit quantity 0 is supplied to the sample gate wave generator turtle 2. Based on the output of the depth gate wave generator 1 and the pulse oscillator 2 (Fig. 2 a), after a predetermined period of time t has elapsed, Fig. 2 g
A depth gate wave G shown in is generated. Note that the predetermined time and the duration T of the depth gate wave G are controlled by the time constant of each monostable circuit. This depth gate wave G is supplied to a sample gate wave generator. Since the gate wave generator 12 is constructed so as not to pass the output while the output f of the monostable circuit 10 exists, it ultimately sends out a sample gate output as shown in FIG. 2h. The gate circuit 13 supplies the output c of the waveform shaping circuit 7 to the speed calculation display 14 as shown at i only during the period when the sample gate output h exists. This signal i does not include Doppler components received by moving objects other than water flow, so the calculated display value does not become unstable. In the embodiment, the received wave signal is selected only in the area where the output of the differentiating circuit 9 exists. I tried not to do it, but the depth gate wave G
When there is a differential output in the interval in which According to the invention, since frequency fluctuations received from moving objects other than water flow are removed before the calculation section, highly accurate speed measurements can be made without flickering of the displayed value.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an electrical waveform diagram of the main part thereof. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a device that detects Doppler components included in reflected waves from moving objects such as tidal currents, a circuit that converts the frequency change of the reflected wave into a signal level change, and a circuit that sends out a pulse output when the output fluctuates rapidly. and a gate circuit for stopping detection of Doppler components in the pulse output existence section.