JP2778564B2 - Takan equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
N; TACtic Air Air Navigation
The present invention relates to a system, and more particularly, to a TACAN system that provides navigation assistance by transmitting a response pulse to an inquiry pulse from an onboard device.

[0002]

2. Description of the Related Art This type of Takan device is disclosed in Japanese Utility Model Laid-Open No. 3-17.
No. 585 and the well-known document "Avionics (revised version)"
[Min. Okada, Nikkan Kogyo Shimbun (published January 30, 1978)], pp. 33-42. This takan device is composed of an on-board takan device and a ground takan device, and the ground takan device transmits a response pulse to an interrogation pulse from the on-board takan device. This is a configuration for calculating the distance to the device.

[0003] Here, the interrogation pulse is a distance measuring pulse (about 125 [pulse pairs / second] at the time of search, about 25 [pulse pairs / second] at the time of tracking.) The pulse is a pulse that the ground Takan device receives and decodes the interrogation pulse from the on-board Takan device, gives a certain delay time, and fires the ground Takan device. It also emits random pulses (squitter pulses) generated from bursts, station identification codes and receiver noise.

[0004] Distance measurement in a conventional takan device is performed as follows. That is, first, an interrogation pulse (a pair of pulses composed of 12 [μs] in the X mode and 36 [μs] in the Y mode) emitted from the on-board Takan device is received by the ground Takan device. The ground TAKAN device delays the signal with a constant response delay time (X mode 50 [μs], Y mode 56 [μ
s]), and (X mode 12 [μ
s], Y mode 30 [μs]) as a response pulse to the onboard machine. The onboard TAKAN device receives this response pulse and calculates the distance in accordance with the principle of radar.

Here, assuming that the time from when the onboard Takan device receives the inquiry pulse to the response pulse is T, the distance from the onboard Takan device to the ground Takan device is R, and the speed of light is C, T = 2R / C + (Response delay time) Since the following relationship is obtained, by obtaining T, the distance R
Can be requested.

A method in which the on-board Takan device detects its own response pulse from the transmission pulses 2700 ± 90 [pulse pairs / second] of the ground Takan device uses a gate (for example, 16 [μs]) of the response pulse to the interrogation pulse. Distance 0 [nautical miles] (hereinafter, “nautical miles” is represented by symbol NM) to 300
The shift is performed at a constant speed up to [NM], and if the number of response pulses is obtained, for example, 50% or more with respect to the number of interrogation pulses, it is recognized as its own response pulse.

[0007] Normally, the transmission pulse 270 of the ground Takan device
0 ± 90 [pulse pairs / second] is a random pulse since it is generated from the decode pulse generated from the receiver noise. Accordingly, the probability of a pseudo response pulse of noise with respect to the interrogation pulse (the probability of making a random pulse a response pulse with respect to the interrogation pulse) is small, and does not reach “50%” recognized as a response pulse. The permissible value of the response delay time of the ground takan equipment related to the distance accuracy is ± 1.
Since the time is specified within [μs], the monitoring control device 4 monitors this. The monitoring method by the monitoring control device 4 is performed by a method of inputting an inquiry signal similar to the inquiry signal from the on-board takan device to the transponder device as a monitor signal. Then, the distance 0 [NM], that is, the response delay time is measured. If the response delay time exceeds an allowable value, an alarm is generated and the TAKAN device is stopped.

Meanwhile, a receiver of a terrestrial takan device that satisfies the coverage area 200 [NM] has a receiving sensitivity of -95 [dBm] or less and decode pulse (random pulse) from mixer noise.
Has been generated. With the recent technological progress, personal radios and the like have become easily available, and rare radios (defective spectrums) have been rarely used, and the reception frequency band (1024 to 1150 [MH]
z]) may be mixed with a signal (corresponding to -73 [dBm] at the maximum) to saturate the receiver of the terrestrial Takan device.
For this reason, the decoding pulse due to the noise disappears, and the ground-side takan device becomes abnormal. Further, since there is no response pulse to the interrogation pulse, an alarm is generated by the monitoring and control device 4, which causes the ground TAKAN device to stop.

FIG. 4 is a block diagram showing a basic configuration of a conventional takan system, and FIG. 5 is a block diagram showing a basic configuration of a receiver for a ground takan device. FIG. 6 is a timing chart showing a waveform diagram relating to the signal processing. FIG. 6A shows a case in which an interference radio wave is mixed, and FIG. Time).

[0010] First, referring to FIG.
The transponder device 2 includes a transponder device 2 that transmits and receives signals, an antenna that captures an interrogation signal and emits a response pulse, and a monitoring control device 4 that monitors and controls the transponder device 2.

The interrogation signal C from the on-board device 5 captured from the antenna 3 and the interrogation signal b from the monitoring and control device 4 are input to the duplexer 21 via the directional coupler 41. The receiver 22 encodes a decode pulse obtained by each process described later with respect to the receiver input signal e output from the duplexer 21, and transmits the coded code pulse q to the transmitter 23. The receiver output signal r from the transmitter 23 is emitted from the antenna 3 through the duplexer 21. The receiver 22 has a reception sensitivity in which a random decoding pulse is generated from the reception noise by using a control voltage i described later according to a receiver input signal e including the reception noise and the interrogation pulse.

Referring to FIG. 5, the receiver 22 includes a preselector 201 and a mixer 203 on the input first stage side. The intermediate frequency amplifier 204 is an amplifier whose gain is controlled by a control voltage i, has a narrow band detection circuit of 260 [KHz], and outputs a video output g.

More specifically, a decoder circuit 205 having a video output g of the intermediate frequency amplifier 204 as an input receives an X mode 12 [μs], Y from the video output g (including the receiver noise and the interrogation pulse). It has a function of decoding a pair pulse in mode 36 [μs] and generating a decode pulse h. The decode pulse h output from the decoder circuit 205 is composed of both a random pulse generated from receiver noise and an interrogation pulse. Decode pulse h
AGC (Auto Gain Controller) to which is input
ol) The circuit 206 determines that the decode pulse h is 2700 ± 9
AGC control voltage i (for example, +5 [V] D) for controlling the gain of intermediate frequency
C).

The coder circuit 208 has a function of generating a pair pulse (code pulse q) of X mode 12 [μs] and Y mode 30 [μs] from the decode pulse h.

The operation of each part of the takan device having such a configuration will be described with reference to a time chart of FIG. FIG. 7A shows an operation waveform when an obstacle radio wave is mixed, and FIG. 7B shows an operation waveform at a normal time (when there is no obstacle radio wave).

In both figures, the interrogation pulse a output from the pulse generator 46, the interrogation signal b output from the transmission unit 47, the interrogation signal c from the on-board device 5, the radio signal generating radio 6 , A receiver input signal e, a video output g of the IF amplifier 204, a decode pulse h,
An AGC control signal i and a code pulse q are shown.

First, referring to FIG. 1B, an interrogation signal b of a paired pulse is transmitted in response to an interrogation trigger pulse a of the paired pulse of the first pulse P1 and the second pulse P2 from the pulse generator 46. In addition, the on-board device 5
Also sends a pair pulse interrogation signal c. At this time,
Since the signal d from the radio wave generating radio 6 does not exist,
The interrogation signals b and c become the receiver input signal e as they are. Therefore, a paired pulse corresponding to each pulse of the interrogation signals b and c appears also in the video output g in the receiver 22.

The video output g includes noise in addition to the paired pulses corresponding to the respective pulses of the interrogation signals b and c, and the decoder circuit 20 to which these paired pulses and the noise are input.
5 outputs a single decode pulse h as shown. The decode pulse h is input to the coder circuit 208, and the coder circuit 208 outputs a code pulse q of a counter pulse.

The decode pulse h is supplied to the AGC circuit 206.
From the AGC circuit 206, the level of which changes around +5 [V] in accordance with the decode pulse h.
The control signal i is output, and the gain of the intermediate frequency amplifier 204 is controlled. In this case, the gain decreases when the level of the AGC control signal i increases, and conversely, the gain increases when the voltage level decreases.

As described above, when the signal level of the signal d applied as a disturbance from the radio wave generating radio 6 to the receiver 22 is -90 [dBm] or less, the AGC circuit 206 suppresses the normal operation of the takan device. It works. At this time, the receiver noise is reduced by the amount suppressed by the AGC control voltage i. The decoder circuit 205 applies a reverse bias of about -0.5 [V] to the video output g so that the circuit operation is stabilized. Therefore, if the receiver noise is smaller than the reverse bias, decoding cannot be performed.

For this reason, like the signal d in FIG.
Disturbance signal stronger than 90 [dBm] (for example, -80 [dB]
m], the receiver noise becomes smaller than the reverse bias voltage and decoding becomes impossible, and the pulse partially disappears like the decode pulse h in FIG. When there is no more pulse in the decode pulse h, the AGC circuit 206
Operates to lower the AGC control voltage i to 0 [V] and increase the gain of the intermediate frequency amplifier 204. For this reason, as shown in FIG. 3A, the video output g is saturated, and the decoding pulse h in that portion disappears, and an abnormal state occurs.

As a result, the respective pairs of pulses by the interrogation signals b and c are not decoded together, and the monitoring controller 4 detects an abnormality. Then, the control to stop the transponder device 2 is performed by the occurrence of this alarm, and the ground takan device is in a stopped state.

Next, the input level of the interference radio wave into the receiver 22 will be considered.

The gain (antenna gain and feeder loss) of the terrestrial equipment 1 is almost 0 [dB], and the output Pt of the disturbance wave is 1
0 [W], its spurious level is -40 [dB], the closest distance R is 100 [m], and the wavelength is λ, Pr = Pt · 10 ^(−40/20) · (λ / 4πR) ² Given by When this is expressed in logarithm, Pr = 10
logPt-40 + 20log (λ / 4πR).
Therefore, the wavelength λ = 0.2757 [m] (frequency 1088
[MHz]), Pr = −73 [dBm].

The limit value at which the receiver 22 becomes abnormal is set to -90.
[DBm], the maximum distance Rmax to receive the disturbance is:
Rmax = 10 ^{[{-73-(-90)} / 20]} × 100 [m] = 708
[M].

[0026]

The above-described receiver of the ground-based takan device stops radio waves when the radio wave generating radio (FM wave or continuous wave) is at a relatively short distance (within 800 [m]). Would. When the radio wave of the ground takan device stops, it is no longer possible to give the azimuth and distance to the ground takan device (generally an airfield) to the navigating aircraft using it, which is important for navigation safety. It has the disadvantage of being problematic.

In addition, the ground Takan device is operated continuously (24
However, when a failure occurs, it is necessary to take an urgent action and a maintenance person is called at night. That is, since the radio wave generating radio 6 is rarely present, if the ground takan device is interrupted by this, the maintenance guard thinks that the equipment has failed and goes to the Takan station for repair. Disadvantage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to enable operation without interruption even when a radio wave generating radio is relatively close,
An object of the present invention is to provide a Takan device capable of giving information on the distance and direction of a ground Takan device to an aircraft within a short distance (equivalent to 200 NM).

[0029]

According to the present invention, there is provided a takan device for generating monitor signal for generating a monitor signal equivalent to an external interrogation signal, and for generating a response signal in response to the interrogation signal and the monitor signal. A response signal generating means for generating the monitor signal, and a monitoring means for determining that the apparatus itself is abnormal when a response signal to the monitor signal is not generated within a predetermined time after the monitor signal is generated by the monitor signal generating means. The device, wherein the state where the reception intensity of the signal from the outside is equal to or higher than a predetermined value has continued for a predetermined time or more
An attenuator for attenuating a received signal in accordance with the reception intensity is provided, and the interrogation signal is input to the response signal generator via the attenuator.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention is as follows.

Since the mixed FM wave or continuous wave is reduced to a level equivalent to the receiver noise by the variable attenuator, the saturation of the mixer and the intermediate frequency amplifier is eliminated, and the decoding pulse can be generated by the receiver noise. Become.
At this time, the interrogation signal from the supervisory control device is similarly reduced, so that the interrogation pulse cannot be detected by the conventional circuit, but the interrogation signal of the supervisory control device is supplied instead by supplying the interrogation trigger pulse through the gate circuit. A response pulse to the pulse can be transmitted.

During the period in which the FM wave or the continuous wave mixed as described above exists (generally, for 2 to 5 minutes), the reception sensitivity to the aircraft is reduced, but the aircraft located at a short distance within 20 [NM]. Hetakan information can be provided.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a main part of a first embodiment of a takan device according to the present invention, and shows a configuration of a receiver in the takan device. 5, the receiver 22 includes a mixer 209 and a LOG amplifier for detecting the reception intensity of the mixed FM wave or continuous wave, and a timer circuit 211 for detecting the duration of the mixed FM wave or continuous wave in the configuration of FIG. A switch circuit 212 that is controlled to open and close according to the detection result of the timer circuit 211, a driver circuit 213 that outputs a control signal k corresponding to the reception intensity when the switch circuit 212 is closed, The generated reference voltage generation circuit 214, a comparator 215 for comparing the generated reference voltage with the reception intensity, a gate circuit 217 controlled to open / close according to the comparison result, and a query trigger pulse from the monitoring control device 4. And a adding circuit 207 for adding the pulse h and the pulse n. That is, in the receiver 22, first, the output of the preselector 201 is distributed, and one is supplied to the newly provided variable attenuator 202 and the other is supplied to the newly provided mixer 209. Variable attenuator 2
02 from the mixer 203 connected to the decoder circuit 205
Since the configuration up to this point is basically the same as that described with reference to FIG. 5, the same components are denoted by the same reference numerals, and description thereof will be omitted. Only different portions will be described.

In such a configuration, the mixer 209 and the LOG amplifier 210
, And its duration is detected by the timer circuit 211.

This detection is performed as follows. That is,
The output of the LOG amplifier 210 is generally a detection signal, and the same applies to the present circuit. Therefore, the timer circuit 211 counts the duration of the detection signal. Specifically, the detected signal is compared with a fixed voltage, and a signal having the fixed voltage or more is set to “1”. In this case, "1110111"
Even if "0" is included in the middle as described above, filtering is performed so that "1111111" is counted.

The reason why the LOG amplifier is used instead of the linear amplifier is that the LOG amplifier has a wider timing range.

When the detected duration exceeds a predetermined time (for example, 10 [ms] or more), the switch circuit 2
12 is closed, and a control signal k corresponding to the mixed reception intensity is output from the driver circuit 213 to the variable attenuator 202. As a result, the mixed FM wave or continuous wave is reduced to a level corresponding to the noise level.

Further, when the mixed FM wave or continuous wave exceeds the reference voltage, the gate circuit 217 is opened (enabled), and the decode pulse of the decoder circuit 216 and the output pulse of the decoder circuit 205 are output. The addition is performed by the addition circuit 207. That is, the gate circuit 217
, The decode pulse of the decoder circuit 216 is input as a pulse n to the adder circuit 207, and is added to the decode pulse h output from the decoder circuit 205. The added pulse p is sent to the coder 208 and also to the AGC circuit 206.

The operation of each part of the takan device of this embodiment having the above-described configuration will be described with reference to the time chart of FIG. FIG. 7A shows an operation waveform when an obstacle radio wave is mixed, and FIG. 7B shows an operation waveform at a normal time (when there is no obstacle radio wave).

In both figures, an interrogation trigger pulse a output from the pulse generator 46, an interrogation signal b output from the transmitter 47, a receiver input signal e, and an output signal f of the variable attenuator 202 are shown. The video output g of the intermediate frequency amplifier 204
, Decode pulse h, AGC control signal i, and LOG
The LOG video signal j from the amplifier 210 and the comparator 21
5, a control signal m to the gate circuit 217, a decode pulse n input to the addition circuit 207 when the gate circuit 217 is opened, an output pulse p of the addition circuit 207, and a code pulse output from the coder circuit 208. q is shown.

First, referring to FIG. 3B, a paired pulse interrogation signal b is transmitted in response to an interrogation trigger pulse a by a paired pulse of the first pulse p1 and the second pulse p2. Also, an interpulse interrogation signal is transmitted from the on-board device. At this time, since there is no interference radio wave,
Both interrogation signals become receiver input signals e as they are.

The receiver input signal e is input as it is to the intermediate frequency amplifier 204 via the mixer 203 as the output signal f of the variable attenuator 202. Intermediate frequency amplifier 204
The video output g includes noise in addition to the paired pulses corresponding to the respective interrogation signals, and the decoder circuit 205 to which the paired pulses and the noise are input outputs a single-pulse decode pulse h as shown in the figure. Is output. This decode pulse h is input to the addition circuit 207 and is added to the pulse n.

In FIG. 6B, since no obstacle radio wave is input, the LOG video signal j from the LOG amplifier 210 continues only for a short time. Therefore, the switch circuit 212 does not close. Therefore, the comparator 215
Does not open the gate circuit 217 in response to the control signal m, and no pulse exists in the pulse n. Therefore, the output pulse p of the adder circuit 207 remains unchanged from the decode pulse h.
Becomes The output pulse p is input to the coder circuit 208,
The coder circuit 208 outputs a code pulse q of a counter pulse.

The decode pulse h is supplied to the AGC circuit 20.
6 whose level changes from +5 [V] in response to the decode pulse h from the AGC circuit 206.
The C control signal i is output, and the gain of the intermediate frequency amplifier 204 is controlled. Also in this case, the gain decreases when the voltage level of the AGC control signal i increases, and conversely, the gain increases when the voltage level decreases.

Next, referring to FIG. 6A, as a result of the interfering radio waves, the input signal e of the receiver has the same waveform as that of FIG. This receiver input signal e is input to the variable attenuator 202 and
The signal is input to the G amplifier 210. And LOG amplifier 2
10 outputs a LOG video signal j.

The timer circuit 211 has a reception intensity of a mixed fault wave of a predetermined level or more (for example, -90 [dBm] or more) and a duration of a predetermined time or more (for example, 10 [m]).
s] or more), the switch circuit 212 is closed. As a result, the driver circuit 213 applies a control voltage k of a level corresponding to the LOG video signal j to the variable attenuator 202.
Therefore, the interfering wave is mixed by the variable attenuator 202.
It is attenuated to the reception noise level. This is the output signal f in FIG. Therefore, the conventionally provided mixer 203 and intermediate frequency amplifier 204 operate normally and can generate the decode pulse h from the noise received by the decoder circuit 205.

However, since the interrogation signal b from the monitoring and control device 4 is also attenuated to a level corresponding to noise, it is slightly decoded but does not reach the specified response rate of 50 [%]. Therefore, if the interference radio wave is mixed, the apparatus may be detected as abnormal, and it is necessary to compensate the decoding pulse h for the interrogation pulse of the monitoring and control apparatus 4. The following describes this compensation operation.

The comparator 215 compares the voltage levels of the fault wave j detected by the timer circuit 211 and the reference voltage 1 of the reference voltage generation circuit 214 (corresponding to a reception input level of -90 [dBm]). . As a result of the comparison, when the fault wave is higher than the reference voltage l, the control signal m for opening the gate circuit 217 is output from the comparator 215.

The interrogation trigger pulse a of the monitoring control device 4 is
The signal is also input to the decoder circuit 216 of the receiver 22, and the decoder circuit 216 generates a single pulse (equivalent to the decode pulse h) from the pulse a that is the counter pulse. The generated pulse is applied to the gate circuit 217. Here, when the control signal m for opening the gate circuit 217 is applied as described above, a single pulse n is output, and the addition circuit 207 adds the single pulse n to the decode pulse h of the decode circuit 5. One of the output pulses p of the adding circuit 207 is
The pulse is applied to the AGC circuit 206 for feedback and is controlled so that the total pulse becomes 2700 ± 90 [pulses / second]. The other of the output pulses p is transmitted to a coder circuit 208 that generates a pair of response pulses. The code pulse q output from the coder circuit 208 is
3 is input.

In short, when the attenuator 202 attenuates the reception gain, a signal equivalent to an external interrogation signal is input to the coder circuit 208 as a monitor signal. In this way, even when the radio wave generating radio is at a relatively short distance, the monitoring control device 4 does not determine that the radio wave is abnormal. Therefore, even if the radio wave generating radio equipment is relatively close, it can be operated without stopping, and information on the distance and direction can be given to a short-range aircraft.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram showing a configuration of a receiver in a takan device according to a second embodiment of the present invention. 1 is basically the same as the configuration shown in FIG. 1, and therefore, the same components are denoted by the same reference characters, and the description thereof will not be repeated. Only different points will be described.

The configuration of FIG. 3 differs from the configuration of FIG.
An intermediate frequency amplifier 220 and a disturbance determination circuit 221 are provided, and a signal from a pulse generator 46 in the monitoring control device 4 is input to a gate circuit 217.

In this example, the reason why the intermediate frequency amplifier 220 is provided instead of the LOG amplifier is that although the amount of change of the mixed signal is about 20 [dB], even if a linear amplifier is used, it is slightly saturated. This is because the intensity of the input signal can be detected.

The basic operation of the disturbance determination circuit 221 is similar to that of the timer circuit 211 and the reference voltage generation circuit 214 shown in FIG.
And the operation by the comparator 215. That is,
It is determined that the signal is a disturbance signal based on the level of the mixed signal and its duration. By integrating the timer circuit 211, the reference voltage generation circuit 214, and the comparator 215, an integrated circuit can be formed, and the size of the receiver 22 can be reduced. If the disturbance determination circuit 221 determines that a disturbance has occurred, the gate circuit 217 is activated in the same manner as in FIG.
A control signal m for opening the gate is transmitted.

Although the interrogation trigger pulse a of the monitoring control device 4 is a paired pulse, in this example, only a single pulse is sent from the pulse generator 46 (the transmission timing is the position of the second pulse p2).
Is transmitted, the decoder circuit 216 in FIG. 1 can be omitted. Thereby, the entire receiver 22 can be made smaller.

Incidentally, the radio wave generating radio equipment is a mobile personal radio equipment or the like, and has a radius of 80 m
Obstacles only when approaching within 0 [m] (generally 2 to
5 minutes). Therefore, if the obstacle radio is farther away, it will continue to operate normally. Therefore, according to the present takan device, even if the radio wave generating radio equipment is at a relatively short distance, the radio wave does not stop and the safety of the aircraft during navigation can be ensured.

Further, an aircraft at a long distance can receive the service of another station, even if the ground takan device at the destination becomes abnormal. However, short-distance aircraft are less likely to receive services other than the destination ground takan device, and have less time to spare. Even in this case, according to the present Takan apparatus, takan information (distance and direction) is given to an aircraft having a signal stronger than the interfering radio wave signal (-70 [dBm] or more: within 20 [NM] in distance). You can do it.

[0060]

As described above, according to the present invention, the signal reception gain is attenuated when the reception intensity of an external signal is equal to or higher than a predetermined value for a predetermined period of time. Even if the apparatus is relatively close, it is not determined that the apparatus itself is abnormal, so that the apparatus can be operated without interruption.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiver in a Takan device according to a first embodiment of the present invention.

FIG. 2 is a time chart showing waveforms at various parts in FIG.

FIG. 3 is a block diagram showing a configuration of a receiver in a Takan device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional takan device.

FIG. 5 is a block diagram showing a configuration of a receiver in the Takan device of FIG. 4;

FIG. 6 is a time chart showing waveforms at various parts in FIGS. 4 and 5;

[Explanation of symbols]

 201 Preselector 202 Variable attenuator 203, 209 Mixer 204, 220 Intermediate frequency amplifier 205, 216 Decoder circuit 206 AGC circuit 207 Addition circuit 208 Coder circuit 210 LOG amplifier 211 Timer circuit 212 Switch circuit 213 Driver circuit 214 Reference voltage generation circuit 215 Comparison 217 Gate circuit 221 Disturbance determination circuit

Claims (3)

(57) [Claims] 1. A monitor signal generating means for generating a monitor signal equivalent to an external inquiry signal, a response signal generating means for generating a response signal in response to the inquiry signal and the monitor signal, and the monitor signal Monitoring means for determining that the apparatus is abnormal when a response signal to the monitor signal is not generated even after a predetermined time has elapsed after generation of the monitor signal by the generation means; Attenuating means for attenuating a received signal in accordance with the received intensity when a state where the intensity is equal to or more than a predetermined value continues for a predetermined time or more , and generating the response signal through the attenuating means, A takan device characterized in that the input is made to a means. 2. The apparatus according to claim 1, further comprising signal control means for directly inputting said monitor signal to said response signal generating means without passing through said attenuating means when said received signal is attenuated by said attenuating means. The takan device according to claim 1. 3. The signal control unit includes a gate unit that is enabled when the reception signal is attenuated, and the monitor signal is input to the response signal generation unit via the gate unit. The takan device according to claim 2, characterized in that: