JPH01254885A - Multi-frequency drive device - Google Patents

Abstract

PURPOSE:To switch the capacity of a capacitor for resonance connected with an object to be driven without using a semiconductor or mechanical switch by connecting or separating the 2nd capacitor to or from the object to be driven by utilizing the variation of the reactance value of an inductor. CONSTITUTION:Assuming that capacitors respectively having capacity values C1 and C2 are required to be connected in parallel with each other in order to cause an object 3 to be driven to resonant with two frequencies. Therefore, the 1st capacitor 8 having the capacity value C1 is connected in parallel with the object 3 directly and the 2nd capacitor 9 having the capacity value C2 is connected in parallel with the object 9 through an inductor 11. The reactance value of the inductor 11 becomes higher or smaller and the electric current flowing through the inductor 11 is limited to a small or increases when the frequency of signals becomes higher or lower, resulting in the magnetic unsaturation or saturation of a magnetic core. As a result, it is considered that the capacitor 8 of capacitors 8 and 9 are equivalently connected in parallel with the object 3 and the capacitor 9 is brought into contact with or separated from the object due to the variation of the reactance value of the inductor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a multi-frequency drive device that can be used, for example, in ultrasonic equipment such as a fish finder, or radio equipment such as an underground radar.

"Prior Art" Figure 4 shows the configuration of a conventional fish finding device. In the figure, 1 indicates an ultrasonic transmitter. For example, an ultrasonic signal of 100 kHz outputted from the ultrasonic transmitter 1 is applied to a driven body 3 such as an ultrasonic transducer through an output transformer 2, and excites the driven body 3 at a frequency of 100 kHz. This excitation time is quite short, for example, on the order of several milliseconds.

When the reflected wave returns after excitation, the driven body 3 converts the reflected wave into an electrical signal and inputs it to the receiver a4. Since the transfer signal obtained by the reflected wave is a weak signal, anti-parallel diode circuits 5A and 5B are connected between the driven body 3 and the output transformer 2 in order to prevent this weak signal from leaking to the transmitter side. is interposed.

Further, a limiter 6 is connected between the receiver 4 and the transducer 3 in order to prevent a large amplitude excitation signal from being input to the receiver 4.

The capacitors 7A and 7B also serve to protect the diodes constituting the limiter 6 from the excitation signal and to tune the resonant frequency of the driven body 3 to the frequency of the excitation signal.

In this way, conventional ultrasonic fish finding devices intermittently transmit ultrasonic waves of a single frequency, capture the reflected waves, and display images of underwater conditions.

However, the propagation characteristics and reflection characteristics of ultrasonic waves in water largely depend on the frequency of the ultrasonic waves, and the intensity of reflected waves varies depending on the size of the fish body, the depth, etc. For this reason, it is known that the detection ability can be improved by switching the frequency of the 81& wave and being able to view images captured by ultrasonic waves of different frequencies. For this reason, conventionally, for example, 50kHz
Equipped with a fish finder using 200kHz ultrasonic waves and a fish finder using 200kHz ultrasonic waves, the f! Judging the type, etc.

Equipped with two fish finding devices in this way is not preferable because it is a heavy economic burden and also takes up a lot of space.

For this reason, it would be convenient to have a fish finding device that alternately emits ultrasonic waves of two frequencies and simultaneously displays images obtained by the ultrasonic waves of each frequency on one display.

Against this background, a transducer has been developed that has a plurality of resonant frequencies and can selectively generate ultrasonic waves of different frequencies by applying a drive signal of each resonant frequency.

By using this multi-frequency transducer, a multi-frequency fish finding device can be obtained.

“Problem to be Solved by the Invention” When constructing a multi-frequency fish finding device using a multi-frequency transducer, the ultrasonic transmitter transmits high-frequency signals several times per second, as shown in Figure 5. The ultrasonic signal F1 and the low frequency ultrasonic signal F2 are alternately transmitted, and the ultrasonic signals having these two frequencies are applied to a multi-frequency transducer to drive it.

When driving the transducer at a certain frequency, resonance capacitors 7A, 7 are used to make the transducer resonate at the driving frequency.
B must be connected in parallel to the circuit.

In FIG. 4, the series capacitance of capacitors 7A and 7B acts as a parallel resonant capacitance.

Therefore, when driving the driven body alternately at different frequencies,
The resonance capacitor must be switched so that the driven object resonates at each frequency.

Since this switching period is approximately several times per second, switching can be easily performed using a semiconductor switching element. However, the amplitude value of the ultrasonic signal applied to the driven object is several k.
The voltage is approximately V, and there are no semiconductor switching elements that can withstand this voltage.

For this reason, it is possible to use a mechanical contact switch such as a relay, but if a 7-inch mechanical contact switch is used, the contacts will wear out quickly if they switch at a frequency of several times per second. There are problems with durability and reliability.

An object of the present invention is to provide a multi-frequency drive device that can switch the capacitance of a resonant capacitor connected to a driven object without using a semiconductor switch or a mechanical switch.

"Means for Solving the Problems" The present invention includes a transmitter that outputs drive signals of different frequencies in a time-divisional manner, a driven object such as an ultrasonic transducer connected to the output side of the transmitter, A first capacitor connected in parallel to the driven object and matching the resonant frequency of the driven object to the highest first frequency of the drive signal output from the transmitter; A second capacitor that causes the driven body to resonate at a second frequency lower than the first frequency due to the combined capacitance value of On the other hand, a multi-frequency drive device is constructed with an inductor that has a characteristic of low impedance due to magnetic saturation of the magnetic core, and.

According to the configuration of the present invention, when driving the driven object at the first frequency, which is the highest frequency of the drive signal, the capacitance of the first capacitor acts as a resonant chamber, and the inductor of the second capacitor acts as a resonator. Since it exhibits a large reactance value with respect to frequency, it is maintained in a state where it is not connected to the driven body.

On the other hand, when the frequency of the drive signal is switched to a second frequency lower than the first frequency, the reactance value first becomes a small value corresponding to the frequency ratio, and the current flowing through the inductor increases. This increase in current causes the magnetic core to become magnetically saturated, and the inductor actance value becomes smaller and smaller.

As a result, the second capacitor is connected in parallel to the first capacitor and the driven body.

Therefore, when driven at the second frequency, the driven body is matched to the resonant frequency by the combined capacitance of the first capacitor and the second capacitor.

As described above, according to the present invention, since the second capacitor is connected to and separated from the driven body by utilizing changes in the inductor actance value, even if the switching cycle is relatively fast,
Also, the applied voltage is large (but the capacitors can be switched and connected without any problems).

Therefore, a multi-frequency fish finding device can be made at low cost.
Further, since no semiconductor switching elements or mechanical contact switches are used, it is possible to provide a highly durable and highly reliable multi-frequency drive device.

"Embodiment" FIG. 1 shows an embodiment of the present invention. This example shows a case where the present invention is applied to a dual-frequency ultrasonic transmitter.

In the figure, 1 is an ultrasonic transmitter, 2 is an output transformer, and 3 is a driven body. This example shows a driven object such as a multi-frequency resonant ultrasonic transducer.

It is assumed that this driven body 3 is made to resonate at two frequencies, for example, 200 kHz and 50 kHz.

As this resonance condition, in order to resonate at the first frequency of 200kHz, the capacitance C3 must be connected in parallel, and the second
In order to resonate at a frequency of 50kllz, it is required to connect the capacitance value C2 in parallel.

8 is the first capacitor with a capacitance value C5, 9 is a capacitance value C3
A first capacitor 8 is directly connected in parallel to the driven body 3 , and a second capacitor 9 is connected in parallel to the driven body 3 via an inductor 11 .

The inductor 1■ is equipped with a magnetic core such as ferrite,
For a signal of the first frequency, for example, 200 kHz, the actance value of the inductor 11 exhibits a sufficiently large value, so that the current flowing through the inductor 11 is limited to a small value, and the magnetic core operates without magnetic saturation.

On the other hand, for a signal of the second frequency, for example, 50kllz, the reactance value of the interminator 11 becomes small,
The current flowing through this increases, and the magnetic core becomes magnetically saturated due to the increase in current, and due to this magnetic saturation, the reactance value of the inductor 11 becomes an increasingly smaller value.

As an example, for a frequency of 200kHz, the reactance value LX! When 110 uses an inductor of 1250Ω, the reactance LXS@ of this inductor at a frequency of 50kHz is approximately 1/4 of the frequency ratio, 312.5Ω.
becomes. In this invention, the reactance value is 17 in terms of frequency ratio.
4, the magnetic core is magnetically saturated by an increase in the current flowing through the inductor 11, and the actance of the inductor 11 can be controlled to an even smaller value by this magnetic saturation.

As an example of the inductor 11, as shown in FIG.
When using an inductor of approximately 1Illl with wire 11c wound 200 times, L, l! . . = 1250Ω1-m5°=31Ω, which can be seen as a frequency ratio of 174 and a damping characteristic of approximately 1/10 obtained due to the magnetic saturation of the magnetic core.

As a result, when a drive signal of the first frequency (200kHz) is given, it can be seen that the first capacitor 8 is equivalently connected in parallel to the driven body 3, and the driven body 3 is driven at the second frequency (50kHz). When this happens, it can be seen that the driven body 3 is equivalently connected to the first capacitor 8 and the second capacitor 9 in parallel.

Therefore, if the capacitance value required to make the driven body 3 resonate at the second frequency (50 kHz) is 02, then the parallel combined capacitance of the first capacitor 8 and the second capacitor 9 is C,+(,
, the second capacitor 9 so that C@ = CI + 03.
It is only necessary to select the capacitance value C1 of .

FIG. 3 shows an embodiment of a three-frequency type fish finding device.

In FIG. 3, parts corresponding to those in FIG. 4 are designated by the same reference numerals.

In this example, the first capacitor is divided into 88 and 8B,
A case is shown in which the two first capacitors 8A and 8B are configured to protect the diode constituting the limiter 6 from the drive signal output from the ultrasonic transmitter 1. Therefore, the capacitance value of each first capacitor is selected to be 2C1 so that the series capacitance of 8A and 8B is CI. On the output side of the limiter 6, there is a receiver 114A that amplifies the received signal of the 200kHz ultrasonic wave that is reflected and returns, and a 5Qkll.
A receiver 4B that amplifies the transmission signal of the ultrasonic wave z is connected.

A second capacitor 9 is connected in parallel to the driven body 3 via an inductor 11 in addition to the first capacitors 88 and 8B. This example shows a case where a series circuit consisting of the second capacitor 9 and an inductor 11 is connected in parallel to the driven body 3 via anti-parallel circuits 5A and 5B of diodes.

The reason why the series circuit consisting of the second capacitor 9 and the inductor 11 is connected to the driven body 3 through the anti-series circuits 5A and 5B of diodes is as follows.

In other words, when transmitting ultrasonic waves, the driving output must be effectively transmitted to the driven body 3 to efficiently generate ultrasonic waves.

For this purpose, first capacitors 8A, 8B and a second capacitor 9 are provided for resonance at the first frequency and the second frequency,
The driven body 3 resonates at a first frequency (200 kHz) and a second frequency (50 kHz) to efficiently generate ultrasonic waves.

On the other hand, during reception, the transfer signal generated by the driven body 3 is weak, so it is necessary to effectively transmit the transfer signal (No. 8) generated by the driven body 3 to the receivers 4A and 4B without attenuation. Therefore, the series circuit consisting of the second capacitor 9 and the reactor 11 is converted into an anti-parallel circuit 5A consisting of a diode during reception.
and 5B, and are separated from the driven body 3 to avoid attenuation of the transfer signal.

"Modified Example" In the above, the second capacitor 9 is set to 1 for the first capacitor.
Although an example in which only one second capacitor 9 is provided has been described, it is also possible to provide two or more second capacitors 9 connected in series with the inductor 11 and to drive the driven body 3 at two or more frequencies.

Further, the present invention can be applied not only to ultrasonic waves but also to radio wave devices such as Ikenaka radar.

"Effects of the Invention" As explained above, according to the present invention, the resonant frequency of the driven body 3 can be switched with a simple circuit configuration, and a multi-frequency fish finder or a multi-frequency underground radar can be used. It can be provided at low cost.

Further, in this invention, since the second capacitor 9 is brought into contact with and separated from the driven body 3 simply by changing the reactance of the inductor 11, there is no need to consider voltage resistance and contact wear. Therefore, it is possible to provide a multi-frequency drive system with high durability and reliability.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an embodiment of this invention, Fig. 2 is a perspective view showing an embodiment of an inductor used in this invention, and Fig. 3 is a case in which a multi-frequency fish finding device is configured according to this invention. FIG. 4 is a connection diagram for explaining the conventional technique, and FIG. 5 is a waveform diagram for explaining an example of a drive signal for multi-frequency fish detection. 1: Ultrasonic transmitter, 2: Output transformer, 3: Driven body,
4.4A, 4B: receiver, 6: limiter, 8: first capacitor, l second capacitor, 11: inductor.

Claims (1)

[Claims] (1) A: a transmitter that outputs drive signals of different frequencies in a time-divisional manner; B: a driven body connected to the output side of this transmitter; and C: a driven body connected in parallel to this driven body. a first capacitor that matches the resonant frequency of the driving body to the high first frequency of the drive signal; A second capacitor that resonates at a second frequency lower than the first frequency; What is claimed is: 1. A multi-frequency drive device, comprising: an inductance that has a low reactance value upon saturation;