KR20200054628A - Remote fishing gear monitoring system with optimized active pingers - Google Patents

Abstract

The present invention relates to a remote fishing gear monitoring system with optimized active pingers, capable of reducing power consumption of active pingers. The remote fishing gear monitoring system of the present invention includes an array tracker provided on a managing ship, and active pingers provided on the fishing gear for ultrasonic communication with the array tracker, wherein an ultrasonic signal received by the active pingers from the array tracker is modulated such that digital information corresponds to a time interval between two or more pulses.

Description

REMOTE FISHING GEAR MONITORING SYSTEM WITH OPTIMIZED ACTIVE PINGERS}

The present invention relates to a remote fishing gear monitoring system including an active finger and an array tracker, and more particularly, to a remote fishing gear monitoring system capable of reducing power consumption of an active finger.

Fishermen install fishing gear such as whole nets and nets in the sea to obtain fish and other fishery products. Since these fishing gears are not fixed but are moved by the current, the fishing gears are connected in a row to the buoys floating on the water surface, and fishermen collect the fishing gears by checking the position of the buoys. However, it is not easy to find the buoy as the buoy is not in a fixed position but also moves along the current.

According to published patent publication No. 10-2017-0098572 shown in FIG. 1, an IOT buoy installed on the sea equipped with a GPS, an IOT communication modem, a battery, etc., and an IOT master communication modem for communication with the IOT buoy A phrase monitoring system including a gateway buoy having a communication server and a monitoring server communicating with the gateway buoy through a public network to perform monitoring on the status of a phrase is published.

However, the phrase monitoring system shown in FIG. 1 has a problem in that a communication modem can be installed only on a buoy floating on the surface of the water, so that when the line connecting the fishing net in the water is broken and lost, there is no method to recover the fishing net.

Recently, a system has been devised to detect the underwater position by beamforming in an underwater receiver. However, these systems have excessive signal processing on the underwater transmitter, and there is a problem in that the electrical survival time of the underwater transmitter is shortened.

The present invention is to solve the above problems, it is possible to directly monitor the state of the fish installed in the water and track and recover the location even when the fishing gear is lost, and it is possible to use it for a long time by minimizing the power consumption of active fins. It is an object of the present invention to provide a remote phrase monitoring system.

In order to achieve the above object, a remote fishing phrase monitoring system having an optimized active fin according to the present invention includes an array tracker provided on a management line and an agricultural tracker provided on a fishing gear for ultrasonic communication with the array tracker. And, the ultrasonic signal received by the active fin from the array tracker is characterized in that it is modulated such that digital information corresponds to a time interval between two or more pulses.

In addition, in the embodiment, the signal transmitted by the active fin to the array tracker has digital information in an up-chirp signal in which the frequency is increased or a down-chirp signal in which the frequency is reduced. It is a signal modulated to correspond.

In addition, in the embodiment, the active fins are provided with ultrasonic transducers for transmitting and receiving ultrasonic signals to one side and the other, respectively.

In addition, in the embodiment, the array tracker has a plurality of receiving sensors arranged in a circle, and extracts the orientation of the active fin using the signal size and phase of the ultrasonic signal received from the active fin.

In addition, in the embodiment, the active fin includes a transducer that converts the received ultrasonic signal into an electrical signal, and a modulator that modulates the frequency of the electrical signal to an intermediate frequency by using a local oscillation signal. It is characterized by 455 kHz.

In addition, in the embodiment, the array tracker, a receiving sensor for converting the received ultrasonic signal into an electrical signal, and a first intermediate frequency located in the pass band of the band pass filter using the local oscillation signal to the frequency of the electrical signal It includes a first modulator for modulating to.

In an embodiment, the array tracker further includes a second modulator that modulates the signal modulated at the first intermediate frequency to a second intermediate frequency suitable for analog / digital conversion.

According to the present invention, the transducers for ultrasonic communication are provided on both sides of the active fins, and thus there is an advantage that ultrasonic communication can be performed even if one side of the sensor is buried on the bottom of the sensor due to loss of the phrase.

Further, according to the present invention, the downlink method used in the present invention can drastically reduce the amount of power consumed in the active ping with a demodulator implemented in a simple configuration. Therefore, the survival time of active fins can be extended.

In addition, according to the present invention, since the active fin and array tracker of the present invention use 455 kHz as an intermediate frequency, there is an advantage that a ceramic band pass filter that is not bulky and easy to band-filter can be used.

1 is a view showing a phrase monitoring system according to the prior art.
2 is a view showing a remote phrase monitoring system according to an embodiment of the present invention.
FIG. 3 is a diagram briefly showing the configuration of the active fin shown in FIG. 2.
FIG. 4 is a diagram briefly showing the configuration of the array tracker illustrated in FIG. 2.
FIG. 5 is a block diagram schematically showing some components of the digital signal processor shown in FIG. 4.
FIG. 6 is a block diagram briefly showing the configuration of the received signal amplifier shown in FIG. 4.
7 is a waveform diagram of an electrical signal for explaining a downlink ultrasonic communication method of an active finger used in a remote phrase monitoring system according to an embodiment of the present invention.
8 is a waveform diagram of an electrical signal for explaining an uplink ultrasonic communication method of an active finger used in a remote phrase monitoring system according to an embodiment of the present invention.
9 is a view for explaining the direction tracking method of the array tracker according to the present invention.
10 is a view for explaining a method of measuring the distance of an active finger according to the present invention.
11 is a view for explaining an active ping disposed in a phrase.

The configuration and operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing a remote phrase monitoring system according to an embodiment of the present invention.

Referring to FIG. 2, the remote phrase monitoring system according to the present invention includes an active fin 100, an array tracker 200, a management line 300, and a fishing net 400.

The active fin 100 is a device that can be coupled to the fishing net 400 to transmit and receive ultrasonic signals underwater, and the array tracker 200 is provided under the management line 300 to use the active fin 100 and ultrasonic signals. It is a device that can communicate.

The active fin 100 receives a signal from the array tracker 200 and transmits an ultrasonic signal corresponding thereto. The active pink 100 is sealed by a watertight case to prevent water from leaking into the water.

FIG. 3 is a diagram briefly showing the configuration of the active fin shown in FIG. 2.

Referring to FIG. 3, the active fin 100 includes a transmitter / receiver 110, a transmitting / receiving switching unit 120, a receiving module 130, a transmitting module 140, and a digital signal control unit 150.

The transducer 110 converts the ultrasonic signal from the array tracker 200 into an electrical signal, or converts an electrical signal into an ultrasonic signal. As the ultrasonic signal from the array tracker 200, ultrasonic waves of a specific frequency band having a certain bandwidth are used. For example, the ultrasonic signal may have a low frequency band between 28kHz and 31kH.

The transmission / reception switching unit 120 may select one of the transmission mode and the reception mode of the active fin 100.

The receiving module 130 includes a low noise amplifier 131, a modulator 132, an intermediate frequency amplifier 133, a passband filter 134, a detector 135, and a level comparator 136.

The low noise amplifier 131 amplifies the electric signal strength from the transmitter / receiver 110 that has passed through the transmission / reception switching unit 120. Since the ultrasonic signal received from the transmitter 110 is attenuated underwater, the intensity of the electrical signal converted by the transmitter 110 is also small. Accordingly, amplification of electric signal strength is required for accurate demodulation. The low-noise amplifier 131 provided in the receiving module 130 amplifies the strength of the electrical signal. For example, the low-noise amplifier 131 can amplify the received signal to about 40db.

The modulator 132 modulates the frequency of the received signal into a signal having an intermediate frequency located in the passband of the bandpass filter using the local oscillation signal 137. For example, the modulator 132 may modulate an input signal having a frequency of 28 kHz to 31 kH into a signal having an intermediate frequency of 455 kHz using the local oscillation signal 137 having an intermediate frequency of 455 kHz. Accordingly, the active fin 100 can use a ceramic band pass filter having a pass band of 455 kHz as the pass band filter 134.

The intermediate frequency amplifier 133 amplifies the signal modulated at the intermediate frequency. For example, the intermediate frequency amplifier 133 may amplify a signal modulated at an intermediate frequency by up to 60 dB.

The passband filter 134 filters the amplified signal. The amplified signal is a signal modulated by the modulator 132 to correspond to the passband frequency of the passband filter. Therefore, a ceramic band pass filter may be used as the pass band filter 134. The ceramic band pass filter can block electrical signals having a frequency outside the frequency band within a certain range based on the center frequency of 455 kHz. The ceramic bandpass filter is not bulky and is suitable for miniaturization of the active fin 100, and has excellent band-blocking effect.

The detector 135 detects the envelope of the modulated signal, and the level comparator 136 detects the pulse based on the preset level based on the detected envelope.

In relation to the reception module 130, the digital signal control unit 150 converts the digital information into digital information using a time interval between two or more detected pulse signals or a pulse width of each of the two or more pulse signals. The downlink method of the present invention is similar to the amplitude shift keying (ASK) method, but in the downlink method of the present invention, information is included in at least one of a time interval and a signal pulse width between two or more signal pulses. It is different from the conventional ASK method in which information is included in each pulse. The downlink method of the present invention can transmit more accurate information than the ASK method.

In addition, the downlink method according to the present invention consumes a lot of power in the modulator of the array tracker 200, but in the active pinker 100 which receives and demodulates the modulated signal, the time intervals or pulse widths of the signal pulses Since only signal processing for sensing is necessary, excessive signal processing is unnecessary, thereby saving battery.

Detailed description of the uplink and downlink ultrasonic communication methods will be described later.

The transmission module 140 includes a power control unit 141, a battery unit 142, a transmission energy storage unit 143, and a transmission power generation unit 144.

The power control unit 141 may supply or cut off the power of the battery unit 142 under the control of the digital signal control unit 150. That is, when the digital signal control unit 150 detects a signal from the array tracker 200, the power control unit 141 supplies power to the battery unit 142. Therefore, power can be selectively supplied without always supplying power, thereby reducing power consumption.

The battery unit 142 stores electrical energy. The battery unit 142 may be composed of at least one battery. The transmission energy storage unit 143 amplifies electrical energy from the battery unit 142. The transmission energy storage unit 143 may be formed of a capacitor.

The transmission power generating unit 144 combines an output signal in the form of an up-chirp type in which the frequency is increased or an output signal in the form of a down-chirp type in which the frequency is decreased by switching signals having two or more frequencies. . That is, the signal transmitted from the active fin to the array tracker is an up-chirp signal in the form of increasing frequency or a down-chirp signal in the form of decreasing frequency, and the Digital information 0 and 1 correspond respectively.

The digital signal control unit 150 controls all components of the active fin 100. It determines whether the power supply of the battery unit 142 of the power control unit 141 is supplied, converts the signal pulse input through the level comparator 136 into digital information, and operates the entire operation of the active pinker 100 based on the digital information. Control.

Since a plurality of active fins 100 are combined in a row for each phrase, an identification code for identifying each of the plurality of active fins 100 is required, and an identification code for grouping and managing a plurality of active fins into a plurality of groups is also required. Do. Signals transmitted in the downlink and uplink include such identification code information.

Specifically, the identification code is a code for distinguishing each individual active fin, and the identification code includes a region ID, a phrase ID, and a group ID. The region ID is an ID for identifying a jurisdiction of a phrase and can be expressed in 4 bits. The phrase ID is an ID for identifying a phrase and can be expressed in 16 bits, and the phrase ID is managed by the land integrated control center. The Joe ID is a phrase divided into smaller units and can be expressed in 4 bits. In particular, the signal on the uplink may further include information on the amount of battery.

The digital signal control unit 150 may analyze the identification code included in the received signal to determine whether it matches the identification code. If the identification code included in the received signal matches its identification code, a channel is formed between the active pinker 100 and the array tracker 200, and underwater communication starts. On the other hand, if the identification code included in the received signal does not match its own identification code, power supply can be cut to minimize power consumption.

FIG. 4 is a diagram briefly showing the configuration of the array tracker shown in FIG. 2, and FIG. 5 is a block diagram briefly showing some components of the digital signal processor shown in FIG. 4. And FIG. 6 is a block diagram briefly showing the configuration of the received signal amplifier shown in FIG. 4.

Referring to FIG. 4, the array tracker 200 includes a sensor module 210, a received signal amplifier 220, and a digital signal processor 230.

The sensor module 210 includes a plurality of receiving sensors arranged in a circle to face different directions capable of transmitting and receiving ultrasonic signals. The sensor module 210 may be provided with, for example, eight receiving sensors. The received signal amplifier 220 amplifies the received signal and processes it in a form suitable for signal processing of the digital signal processor. The digital signal processor 230 restores digital information included in the signal using the processed signal.

5, the received signal amplifier 220, the low-noise amplifier 221, the primary modulator 222, the primary intermediate frequency amplifier 223, 1 so as to correspond to each channel of the plurality of receiving sensors The second pass band filter 224, the second modulator 225, the second intermediate frequency amplifier 226, and the second pass band filter 227 may be provided for each channel. The sensor module 210 includes a plurality of ultrasonic sensors. The plurality of ultrasonic sensors receives ultrasonic signals transmitted in various directions and converts them into electrical signals, and the low-noise amplifier 221 amplifies the intensity of the converted electrical signals.

The low-noise amplifier 221 amplifies the intensity of the electrical signal from the sensor 210.

The primary modulator 222 modulates the electrical signal to the first intermediate frequency using the local oscillation signal having the first intermediate frequency. For example, the first intermediate frequency may be set to 455 kHz. Accordingly, a ceramic filter having 455 kHz as the center frequency can be applied to the first passband filter. The signal modulated at the first intermediate frequency is amplified by the first intermediate frequency amplifier 223.

The first pass band filter 224 removes noise of the amplified signal to maximize the signal-to-noise ratio. For example, the first pass band filter may be a ceramic pass band filter having 455 kHz as the center frequency.

The secondary modulator 225 modulates the second intermediate frequency using a local oscillation signal, thereby facilitating analog / digital (A / D) conversion. For example, the second intermediate frequency may be 20 kHz that facilitates A / D conversion. The signal modulated at the second intermediate frequency is amplified by the second intermediate frequency amplifier 226, and is output through a second pass band filter and a buffer 227 with an improved signal-to-noise ratio.

Referring to FIG. 6, the digital signal processor 230 includes an A / D conversion unit 231 and a matched filter unit 232. The signal amplified from the received signal amplifier 220 is processed by the A / D converter 231 into a digital stream. The matched filter unit 232 includes a first matched filter for matching up-chirp signals and a second matched filter for matching down-chirp signals, and uses the first and second matched filters. Noise can be eliminated. The digital signal processor 230 may restore digital information using a signal from which noise has been removed.

7 is a waveform diagram of an electrical signal for explaining a downlink ultrasonic communication method of an active finger used in a remote phrase monitoring system according to an embodiment of the present invention, and FIG. 8 is a remote phrase monitoring system according to an embodiment of the present invention It is a waveform diagram of an electrical signal for explaining the uplink ultrasonic communication method of the active finger used in.

The uplink is a signal transmission direction from the active tracker 100 to the array tracker 200, and the downlink means a signal transfer direction from the array tracker 200 to the active tracker 100.

The array tracker 200 receives power from the management line 300, but the active fin 100 receives power from a battery. Therefore, the survival life of the active fin 100 is determined by the electrical energy stored in the battery. In general, more batteries are consumed in the process of demodulating a received signal that requires complex signal processing than the process of modulating a transmitted signal. In order to increase the survival life of the active fin 100, it is necessary to avoid complicated signal processing in the demodulation process of the received signal. The downlink method of the present invention does not require complicated signal processing in the demodulation process of the received signal.

Referring to FIG. 7, the downlink method of the present invention is based on an amplitude shift keying (ASK) method, but the downlink method of the present invention includes digital information in a time interval or a pulse width between two or more pulses. In, it is different from the conventional ASK method in which information is included depending on the presence or absence of a pulse every period.

Meanwhile, the ASK method may be used for the downlink method of the present invention.

Assuming that the second received signal s2 is received after the first received signal s1, in the downlink method of the present invention, the pulse between the first received signal s1 and the second received signal s2 is Digital information is included in the time difference dt.

A case in which information is included in a time difference dt between the pulse of the first received signal s1 and the pulse of the second received signal s2 will be described as follows.

When t1 and t2 are preset to set values corresponding to digital information 1 and 0, respectively, when the time difference dt between the first and second received signals s1 and s2 is t1, it is converted to 1, and t1 + t2 In case it can be converted to 0.

In consideration of the delay in the signal processing process or the reception process, a preset error range t3 may be applied. For example, when the time difference dt is t1-t3 <dt <t1 + t3, it can be converted to 1, and when the time difference dt is t1 + t2-t3 <dt <t1 + t2 + t3, 0 Can be converted to Here, t1 is a setting value corresponding to information 1, and t2 is a setting value corresponding to information 0. And t3 is for indicating the error range. t1 and t3 may be positive and t2 may be positive or negative.

In addition, as well as the time difference dt between the pulse of the first received signal s1 and the pulse of the second received signal s2, the pulse width dW of each of the pulses of the first and second received signals s1 and s2 ) May contain information.

The case where information is included in the pulse width dW is as follows.

When W1 and W2 are preset to set values corresponding to digital information 1 and 0, respectively, the pulse width dW may include information of 1 when dW is w1 and 0 information of w2.

Considering the error in the signal processing or receiving process, the information of 1 is included when w1-w3 <dW <w1 + w3, and the information of 0 when w1 + w2-w3 <dW <w1 + w2 + w3 It can contain. Here, w1 is a setting value corresponding to information 1, and w2 is a setting value corresponding to information 0. And w3 is for indicating the error range. W1 and W3 are positive numbers, and w2 can be positive or negative numbers.

Also, it may be determined whether the signal is a pulse based on the pulse width dW. That is, if the pulse width of the signal pulse does not exist within a certain range, it is determined that it is not a signal having information. If the pulse width of the signal pulse is within a certain range, it may be determined as a signal having information.

Since the downlink method only needs to detect the time interval or pulse width of the signal pulse, excessive signal processing is not required, and thus, the amount of power consumed by the active fin can be drastically reduced.

Referring to FIG. 8, the uplink method of the present invention is based on a frequency shift keying (FSK) method, but includes information of 1 when the frequency is increased from F1 to F4 (up-chirp). When is F4 to F1 is reduced (down-chirp) can be set to include the information of 0. The opposite is also possible.

To this end, a signal having a frequency of at least two or more is generated from the digital signal control unit 150, and the generated two or more frequency signals are generated in combination in an up-chirp form or a down-chirp form by being switched in the transmission power generator 144. It is output through the transmitter 110.

The uplink method described above can generate an up-chirp type or down-chirp type output signal only by switching, so that the structure is simple, so that the amount of power consumed by the active fin having the modulator can be reduced.

On the other hand, it is common to use the same method for uplink and downlink of a typical transceiver. However, the remote phrase monitoring system of the present invention significantly reduces the survival time of the active pinger by setting the downlink method and the uplink method differently to reduce power consumption during signal reception of the active pinger and for accurate data transmission during signal transmission. Can be increased and accurate data transmission is possible.

9 is a view for explaining the direction tracking method of the array tracker according to the present invention.

Referring to FIG. 9, in the array tracker 200, receiving sensors S1 to S8 constituting a sensor module for receiving a plurality of ultrasonic signals are arranged in a circular frame at the same angle difference. The arrangement tracker 200 is an arrangement structure having a simple structure and a mechanically robust arrangement. The array tracker is preferably installed on the bottom of the water box.

In this embodiment, a tone filter sensor having a use frequency of 28 to 31 KHz is used, but is not limited thereto.

The eight receiving sensors of the array tracker 200 receive ultrasonic signals transmitted from active fins, and the control unit compares the signal size of each receiving sensor. The signal size is arranged in the order of the largest, and the control unit calculates the phase difference of each receiving sensor centering on the receiving sensor having the largest signal size. A more precise fine direction can be estimated by the calculated phase difference.

For example, if S8 represents the maximum signal size, the phase difference between adjacent S1 and S7 can be calculated to fine-tune the direction in which the phase difference is small.

The control unit may be configured as a terminal separate from the array tracker. At this time, the controller transmits and receives signals to and from the array tracker.

When the array tracker transmits a signal including specific identification code information underwater, an active pinger having specific identification code information may transmit a signal corresponding thereto. Meanwhile, a relaying fish may be included in the fishing net 400 between the plurality of active fishes 100. The relaying fin is intended to assist the surrounding plurality of active fins 100, and the relaying fins may use the same method as the downlink and uplink schemes of the active fins 100. The relaying pin may have a plurality of identification code information for identifying a plurality of adjacent active pins. Accordingly, when a signal including specific identification code information is received from the array tracker, an active pair having specific identification code information and a relay pair including the specific identification code information may transmit a signal corresponding thereto. At this time, in order to prevent interference between signals, the relay pinger may transmit the signal and then the relay pinger may transmit the signal. Meanwhile, the signal transmitted from the specific active fin to the array tracker includes identification code information of the specific active fin, and the signal transmitted from the relay anchor to the array tracker may include identification code information of the relay anchor itself. Accordingly, it is possible to distinguish whether the array tracker is a signal of an active finger or a relay finger. The relaying fins are prepared in case the surrounding active fins are exhausted or have a failure. Since the number of signal transmissions of the relaying fins may be greater than the number of signal transmissions of the active fins, the relaying fins have a larger capacity than the batteries installed in the active fins. It is preferable that the battery is mounted on the relay pin.

10 is a view for explaining a method of measuring the distance of an active finger according to the present invention.

Referring to FIG. 10, the distance between the active fin 100 and the array tracker 200 is calculated through a time difference dt between a transmission signal and a reception signal.

Specifically, the array tracker 200 calculates the distance between the array tracker and the active fin using the time difference between the transmission signal and the reception signal. The distance can be calculated as follows.

R = dt * v / 2

(R is the distance between the array tracker and the active fin, dt is the time difference between the transmitted and received signals, and v is the ultrasonic velocity of the water)

11 is a view for explaining an active ping disposed in a phrase.

Referring to (a) of FIG. 11, when the phrase is not lost, both the transmitter L sensor and the transmitter R sensor are in a position to transmit and receive ultrasonic signals. FIG. 11 (b) is a diagram showing when the phrase is lost and the active fin 100 is buried on one side of the seabed. Even if one side of the active fin 100 is buried under the sea floor, the transducer L sensor provided on the other side can transmit an ultrasonic signal.

According to the present invention, the transducers for ultrasonic communication are provided on both sides of the active fins, and thus there is an advantage that ultrasonic communication can be performed even if one side of the sensor is buried on the bottom of the sensor due to loss of the phrase.

Further, according to the present invention, the downlink method used in the present invention can drastically reduce the amount of power consumed in the active ping with a demodulator implemented in a simple configuration. Therefore, the survival time of active fins can be extended.

In addition, according to the present invention, since the active pinger and array tracker of the present invention include a modulator that modulates to an intermediate frequency located in the passband of the bandpass filter, a ceramic bandpass filter that is not bulky and easy to bandpass can be used. It has the advantage of being able to.

Although described above with reference to the embodiments of the present invention, those skilled in the art can variously modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can change it.

100: Active pink 110: Transmitter
120: transmitting and receiving switching unit 130: receiving module
131: low-noise amplifier 132: modulator
133: intermediate frequency amplifier 134: pass band filter
135: detector 136: level comparator
140: transmission module 141: power control unit
142: battery unit 143: transmission energy storage unit
144: transmission power generation unit 150: digital signal control unit
200: Array tracker 210: Sensor module
220: received signal amplifier 221: low-noise amplifier
222: 1st modulator 223: 1st intermediate frequency amplifier
224: 1st pass band filter 225: 2nd modulator
226: 2nd intermediate frequency amplifier 227: 2nd pass band filter
230: digital signal processor

Claims (7)

Array tracker provided on the management ship; And
It is provided on a phrase, and includes a farming smelt for ultrasonic communication with the array tracker,
A remote phrase monitoring system, characterized in that the ultrasonic signal received by the active fin from the array tracker is modulated such that digital information corresponds to a time interval between two or more signal pulses. According to claim 1,
The signal transmitted by the active fin to the array tracker is modulated so that digital information corresponds to an up-chirp signal in the form of increasing frequency or a down-chirp signal in the form of decreasing frequency. Remote phrase monitoring system. According to claim 1,
The active fin,
Remote phrase monitoring system, characterized in that each comprises an ultrasonic transducer for transmitting and receiving ultrasonic signals to one side and the other side. The method according to any one of claims 1 and 2,
In the array tracker, a plurality of receiving sensors are arranged in a circle,
Remote phrase monitoring system, characterized in that by extracting the orientation of the active fin using the signal size and phase of the ultrasound signal received from the active fin. According to claim 1,
The active fin,
A transducer that converts the received ultrasonic signal into an electrical signal.
And a modulator for modulating the frequency of the electrical signal to an intermediate frequency using a local oscillation signal,
The intermediate frequency is a remote phrase monitoring system, characterized in that located in the pass band of the band pass filter. According to claim 1,
The array tracker,
Receiving sensor for converting the received ultrasonic signal to an electrical signal,
And a first modulator for modulating the frequency of the electrical signal to a first intermediate frequency located in the passband of the bandpass filter using a local oscillation signal. The method of claim 6,
The array tracker,
And a second modulator for modulating the signal modulated at the first intermediate frequency to a second intermediate frequency suitable for analog / digital conversion.

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