JPH05129974A - Receiver - Google Patents

Abstract

PURPOSE:To prevent the distortion of plural degrees caused when plural transmitters approach a booster antenna by discriminating a reception level of a signal from the transmitters thereby automatically switching the gain of a variable gain amplifier. CONSTITUTION:Reception level detection means 21, 22 of a receiver 17 detect a reception level of a signal from transmitters 11, 12, and when a discrimination means 23 discriminates it that the detected reception level is a preset means reception level or over, the means 23 sends a control signal through a control signal superimposition means 24 to decrease the gain of a variable gain amplifier means 16. Thus, even when the transmitters 11, 12 approach a booster antenna 13, distortion of plural degrees caused in the booster antenna is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver paired with a transmitter used for loud sound in schools, halls, television stations and the like.

[0002]

2. Description of the Related Art FIG. 9 shows the structure of a conventional receiving apparatus. In FIG. 9, reference numerals 1 and 2 denote microphone-integrated transmitters that convert voices input from the microphones 1a and 2a and emit transmission radio waves from the transmission antennas 1b and 2b. Reference numeral 3 denotes a booster antenna main body that receives radio waves transmitted from the transmitters 1 and 2. The booster antenna main body 3 includes an antenna element 4, a high frequency filter 5 for extracting high frequency components induced in the antenna element 4, and a variable gain. A gain changeover switch 9 for changing the gains of the amplifying means 6 and the variable gain amplifying means 6 is provided. 7 is a receiver main body connected to the booster antenna main body 3,
It has a reception demodulation means 8.

The operation of the receiving apparatus configured as above will be described. In FIG. 9, when a plurality of transmitters 1 and 2 are used in the vicinity of the booster antenna main body 3, distortion having a sum and difference component of frequencies of the transmitters 1 and 2 occurs in the booster antenna main body 3. , This distortion causes problems such as interference. In such a case, the gain changeover switch 9
The gain of the variable gain amplifying means 6 is lowered by switching between the above and the above to suppress the occurrence of distortion.

[0004]

However, in the above conventional receiving apparatus, it is necessary to predict the reception condition of the signal from the transmitter and set the gain changeover switch in advance. If all transmitters are expected to be used in the vicinity of the booster antenna and the gain of the booster antenna is reduced, unexpectedly the transmitters are used farther apart and there is sufficient reach. Absent. Conversely, when all transmitters are expected to be used away from the booster antenna and the gain is increased, distortion will occur in the booster antennas when multiple transmitters approach the booster antenna. However, there is a problem that the distortion causes interference with a desired wave.

The present invention solves such a conventional problem by determining the reception status of a signal from a transmitter,
An object of the present invention is to provide an excellent receiving device capable of preventing distortion when a plurality of transmitters approach a booster antenna by automatically changing the gain of the variable gain amplifying means.

[0006]

In order to achieve the above object, a receiving apparatus according to the invention of claim 1 receives and amplifies a radio wave from a transmitter, and the gain to be amplified is varied by a control signal. A booster antenna having a variable gain amplifying means capable of, and a receiver that is connected to the booster antenna via a coaxial cable and demodulates a received signal, and the receiver receives the signal from the transmitter. Detecting means for detecting the level, determining means for comparing the average value of the detected reception level with a preset specified value to determine whether or not it is a specified value or more, and the booster antenna based on the result of the determination. Control signal superimposing means for superimposing a control signal for varying the gain on the coaxial cable.

According to a second aspect of the present invention, there is provided a receiving device, which includes a booster antenna having variable gain amplifying means capable of receiving and amplifying a radio wave from a transmitter and varying the gain to be amplified by a control signal. The booster antenna is connected to a booster antenna and includes a receiver for demodulating a received signal. The booster antenna includes a detection unit that detects a reception level of a signal from the transmitter, and an average value of the detected reception levels and a preset value. The determination means is provided to compare with the specified value thus determined to determine whether or not the value is equal to or more than the specified value, and to determine the gain of the variable gain amplifying means based on the result of the determination.

According to a third aspect of the present invention, a receiving device includes a booster antenna having variable gain amplifying means capable of receiving and amplifying radio waves from a plurality of transmitters and varying the gain to be amplified by a control signal. A receiver for distributing the received signal from the booster antenna, and a plurality of receivers connected to the distributor through a coaxial cable for respectively receiving and demodulating the distributed signals. The detecting means for detecting the reception level of the signal from the transmitter and the judging means for comparing the average value of the detected reception level with a preset specified value to determine whether or not the value is equal to or more than the specified value. And a control signal superimposing means for superimposing a control signal for varying the gain of the booster antenna on the coaxial cable based on the determination result, and the reception level at each receiver. A cable for connecting between the input end of the specific determination means and the output end of the determination means of the other receiver or the reception level detection means in order to input the determination result or the detection result to the determination means of the specific one receiver. Have
Further, an output terminal for judging whether or not the cable is connected to the output terminal of each receiver judging means or the receiving level detecting means, and prohibiting the output operation of the corresponding control signal superimposing means only when the connection of the cable is judged. The connection determination means is provided in each receiver.

According to a fourth aspect of the present invention, there is provided a receiving device, which includes a booster antenna having variable gain amplifying means capable of receiving and amplifying a radio wave from a transmitter and varying the gain to be amplified by a control signal. A receiver connected to the booster antenna via a coaxial cable for demodulating a received signal is provided, and the receiver has an S / N detecting means for detecting an S / N ratio of the demodulated signal, and the detected signal. Judgment means for comparing the S / N ratio with a preset prescribed value to decide whether or not it is equal to or larger than the prescribed value, and a control signal for varying the gain of the booster antenna on the basis of the result of the decision. And a control signal superimposing means for superimposing on the control signal.

A receiving apparatus according to a fifth aspect of the present invention includes a booster antenna having variable gain amplifying means capable of receiving and amplifying a radio wave from a transmitter and varying the gain to be amplified by a control signal. The booster antenna is connected via a coaxial cable and includes a receiver that demodulates a received signal, and the receiver includes an intermediate frequency level detection unit that detects an intermediate frequency level of the receiver, and the detected intermediate frequency level in advance. Judgment means for comparing with a set specified value to judge whether or not it is a specified value or more, and a control signal superposition for superposing a control signal for varying the gain of the booster antenna on the coaxial cable based on the result of the judgment. Means are provided.

[0011]

According to the invention of claim 1, it is judged by the judging means whether or not the detection result from the receiving level detecting means is equal to or more than a predetermined value, and the receiving levels of the signals from all the transmitters are judged. If is equal to or more than a specified value, the control signal superimposing means can send a control output to the variable gain amplifying means of the booster amplifier to lower the gain so that the signal is not distorted by the booster amplifier.

According to the second aspect of the present invention, the booster amplifier is provided with the reception level detecting means and the determining means, and the gain is variably controlled by determining the reception level of the signal from the transmitter inside the booster amplifier. Therefore, the same effect can be obtained when used in combination with the conventional receiver.

According to the third aspect of the present invention, when the number of transmitters used increases and one receiver cannot handle it, the output terminals of the judgment means or the reception level detection means of a plurality of receivers are specified. When the cable is connected to the judging means of one receiver and the output terminal connection judging means judges that the cable is connected to the output end, the control signal superimposing means is prohibited from sending the control signal. Then, the final determination of the reception level and the control of the gain of all the transmitters can be performed based on the determination result of one specific receiver and the determination result of the other receiver, and reception confusion can be prevented.

According to the fourth aspect of the present invention, the S / N after demodulation is used to detect the reception level, so that the reception level can be accurately determined even when there is an interfering wave near the desired wave.

According to the fifth aspect of the present invention, by using the RSSI signal, which is a signal obtained by converting the intermediate frequency level for the level meter into a direct current, for the reception level detection, it can be realized at a low cost with a small number of parts.

[0016]

(Embodiment 1) FIG. 1 shows the configuration of a first embodiment of the present invention. In FIG. 1, 11 and 12 are transmitters, 13 is a booster antenna main body, and this booster antenna main body 13 includes an antenna element 14 and
A high frequency filter 15 for extracting a high frequency signal induced in the antenna element 14 and a variable gain amplifying means 16 for amplifying the received signal passing through the high frequency filter 15 and varying the gain of the amplified signal.

Reference numeral 17 denotes a receiver main body connected to the variable gain amplifying means 16 of the booster antenna main body 13 via the coaxial cable 18. This receiver main body 17 is the transmitter 1
Reception demodulation means 19 and 20 respectively corresponding to 1 and 12
And reception level detection means 21 and 22 for detecting the reception level from the signals demodulated by the reception demodulation means 19 and 20, and the reception levels detected by the reception level detection means 21 and 22 and preset. The determination unit 23 that determines whether or not it is equal to or greater than the specified value by comparing the determined specified value with the specified value, and the control signal for changing the gain of the booster antenna main body 13 based on the result of the determination from the judgment unit 23 is the coaxial cable. A control signal superimposing means 24 for superimposing on 18 is provided.

Next, the operation of the first embodiment will be described. Transmitter 1 arriving at antenna element 14
The radio waves from 1 and 12 are selectively amplified by the high frequency filter 15 and the variable gain amplifying means 16 and sent to the corresponding receiving and demodulating means 19 and 20 in the receiver main body 17. The reception demodulation means 19 and 20 demodulate each reception signal and output it to the low frequency amplification means (not shown) from the output terminals 19a and 20a.

On the other hand, each reception level detecting means 21, 22
Detects the reception levels of the transmitters 11 and 12 from the signals demodulated by the corresponding reception demodulation means 19 and 20, respectively,
It is sent to the determination means 23.

When there are two or more transmitters, reception demodulation means and reception level detection means are prepared by the number corresponding to the number of transmitters, and the determination means 23 is provided with an input port corresponding to the number. .. On the contrary, when the number of transmitters is one, the number of the corresponding receiving demodulating means and the corresponding receiving level detecting means is one.

Next, the operation procedure of the judging means 23 will be described with reference to the flow chart shown in FIG. First, in the initial setting, two prescribed values A and B are set in the determination means 23. The specified value A is the reception level when it is sufficiently saturated with the S / N (to such an extent that it does not affect the S / N even if the reception level is lowered to some extent), and the specified value B is for amplifying the demodulated output as it is. Is a limit reception level when S / N deteriorates to an unsuitable level. The SQ level is preferably used as the specified value B (specified value A> specified value B).
When the level signals detected by the reception level detecting means 20 and 21 are input to the determining means 12, first, step S1.
In n, monitoring is performed for n seconds, and if the reception levels from all the reception level detecting means during that time are equal to or higher than the preset specified value A, the process proceeds to step S2 and the variable gain amplifying means 16 of the booster antenna body 13 is A control signal is sent from the control signal superposing means 13 so as to reduce the gain.
(The reason why the reception level for n seconds is monitored is to prevent erroneous determination due to Ted points caused by fading).

If either one of the transmitters 11 and 12 falls below the specified value A, the process proceeds to step S3, and it is determined whether the reception level of the detecting means is the specified value B or more. When it is determined that the value is equal to or larger than the specified value B, it is determined that the booster antenna is being used at a position away from the booster antenna body 13, and the processing of steps S1 and S3 is repeated without lowering the gain in order to obtain a sufficient reaching distance. If it is determined in step S3 that the prescribed value B is not exceeded, the process proceeds to the next step S4, and it is determined whether or not the prescribed value B has been exceeded even after n seconds, and m seconds later. If it has not exceeded even once, it is determined that the transmitter is not in use, and the transmitter is excluded from the determination targets, and the process proceeds to step S5, where a control signal is sent to lower the gain. On the contrary, if the specified value B is exceeded even once, it is judged that the device is used and the process returns to step S1 to repeat the processes of steps S1, S3 and S4 without lowering the gain.

As described above, according to the first embodiment, the gain of the booster antenna main body 13 can be automatically changed according to the reception condition of the signal from the transmitter, and the gain can be used when the transmitter is far away. The effect that the gain can be automatically lowered so as to secure the reaching distance when it is being used, and to suppress the distortion when being used in the vicinity is obtained.

(Embodiment 2) FIG. 3 shows a block diagram of a second embodiment of the present invention. 3 is different from the first embodiment shown in FIG. 1 in that the booster antenna main body 13 is provided with the reception level detecting means and the determining means. That is, the receiving level detecting means 25 for detecting the receiving level of the high frequency output signal output from the variable gain amplifying means 16 is connected, and the receiving level detected by the receiving level detecting means 25 and the preset specified value are set. A judging means 26 for judging whether or not the value is equal to or more than a specified value by comparison is provided, and the variable gain amplifying means 16 is judged by a judging signal from this judging means
Control directly.

In the second embodiment as described above, the same effect as that of the first embodiment can be obtained.

(Third Embodiment) FIG. 4 shows the configuration of a third embodiment of the present invention.

In FIG. 4, elements common to those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, the description thereof will be omitted, and portions different from FIG. 1 will be mainly described.

That is, the third embodiment is different from the first embodiment in that when the number of transmitters used is increased and one receiver cannot handle it, a plurality of receivers are connected in cascade. In addition, a priority function is provided so that final determination and control can be performed by one specific receiver.

For this reason, in the third embodiment, the distributor 27 is connected to the booster antenna main body 13 and the distributor 27 is connected to the first receiver 17A and the second receiver via the coaxial cables 18A and 18B. Machine 17B is connected. The distributor 27 includes a distributor 27a for distributing the signals from the plurality of transmitters selectively amplified by the booster antenna body 13 to the receivers 17A and 17B.

First and second receivers 17A, 17B
Is the same as in the case shown in FIG.
0, the reception level detecting means 21 and 22, the judging means 23 and the control signal superimposing means 24, and each judging means 23 is provided with an input terminal 23a and an output terminal 23b for connecting receivers in cascade. Further, it is determined whether or not a cable 29 for cascading both receivers is connected to each output terminal 23b, and when the cable is connected to the output terminal 23b, control of the output terminal 23b is performed. Output terminal connection determining means 28A, 28B for controlling the signal superimposing means 24 to stop the transmission of the control signal are provided.

The operation of the third embodiment will be described below. The high frequency output signal selectively amplified by the booster antenna main body 13 is distributed by the distribution means 27a of the distributor 27 and sent to the first and second receivers 17A and 17B. Receiving this signal, the receivers 17A and 17B determine the reception level of the corresponding transmitter according to the processing procedure shown in FIG. 2, and control the gain of the booster antenna body 13 according to the determination result.

When the output terminal 23b of the receiver 17A and the input terminal 23a of the receiver 17B are connected by the cable 29 as shown in FIG. 4, the output terminal 23b is used.
The output terminal connection determination means 28A on the side of the receiver 17A that has determined that the cable 29 is connected to the control signal superimposition means 24 of the receiver 17A outputs the determination signal to the control signal superposition means 24 of the receiver 17A. Hold the control output in the stopped state. As a result, the determination means 2 on the receiver 17A side
The determination signal of No. 3 is input to the determination means 23 on the receiver 17B side through the output terminal 23b and the cable 29. Therefore, the receiver 17B finally determines the reception levels of the signals from all the transmitters based on the determination result from the receiver 17A and the determination result from the receiver 17B itself.

As described above, according to the third embodiment, even when a plurality of receivers are connected, the final judgment and control of the reception level can be performed by one receiver, and each receiver can be determined. It is possible to prevent confusion caused by the receiver arbitrarily performing level determination and control.

(Fourth Embodiment) FIG. 5 shows the configuration of a fourth embodiment of the present invention.

The fourth embodiment differs from the third embodiment in that the third embodiment outputs the determination result of the determining means, whereas the fourth embodiment outputs the receiving level detecting means. It is in the place where the detection result is output.

Hereinafter, elements common to the constituent elements of the third embodiment shown in FIG. 4 will be assigned the same reference numerals and explanations thereof will be omitted, and a description will be given focusing on parts different from the third embodiment. The reception level detecting means 21 and 22 of the first and second receivers 47A and 47B are provided with output terminals 21a and 22a for extracting the reception level signals, and further, the receivers 47A and 47.
The B determination means 48 is provided with a pair of input terminals 23c and 23d. Then, the detection signal output terminal 21a of the receiver 47A
2 between the judgment input terminal 23c of the receiver and the receiver 47B
9a, and the detection signal output terminal 22a of the receiver 47A and the determination input terminal 23d of the receiver 47B.
The cables 29b are connected to each other. Also, each receiver 4
Output terminal connection determination means 49A, 49B for determining whether or not the cables 29a, 29b are connected to the detection signal output terminals 21a, 22a of 7A, 47B are provided.

In the fourth embodiment, the receiver 47
A cable 29 is connected to the detection signal output terminals 21a and 22a of A.
Since a and 29b are connected, the output terminal connection determining means 49A that determines this state prohibits the control signal superimposing means 24 from outputting the control signal. Then, the reception level signals detected by the reception level detection means 21 and 22 of the receiver 47A are input to the determination means 23 of the receiver 47B through the cables 29a and 29b. as a result,
The determination means 23 on the side of the receiver 47B receives the reception level signal detected by the reception level detection means 21 and 22 of its own, and the receiver 4
By executing the processing flow shown in FIG. 2 based on the reception level signal from 7A, the reception level of the transmitter is determined. As a result, the same effect as that of the third embodiment can be obtained.

(Embodiment 5) FIG. 6 shows the configuration of a fifth embodiment of the present invention, in which the S / N ratio after the reception signal demodulation by the reception demodulation means is detected, and this S / N ratio is detected. It is characterized in that a gain control command is generated from.

In FIG. 6, reference numeral 30 denotes a receiver main body for inputting a high frequency signal from the booster antenna main body through an input terminal 31a and outputting a demodulated signal through an output terminal 31b, and a high frequency filter 32 for passing a high frequency component. High frequency amplifier 33 for amplifying the high frequency signal that has passed through, mixer 35 for mixing the oscillation signal from local oscillator 34 and the high frequency signal from high frequency amplifier 33, intermediate frequency filter 36 for extracting the intermediate frequency, intermediate frequency amplifier 37 and demodulation And a container 38. Further, 39 is an S / N detecting means 37 for detecting the S / N ratio from the demodulated signal of the demodulator 38, and 40 is a determining means for judging whether the S / N is equal to or more than a preset actual value. , 41 are control signal superimposing means for outputting a control signal for varying the gain of the booster antenna main body based on the determination result.

According to the fifth embodiment thus constructed, the reception level can be accurately detected even when the interfering wave exists near the desired wave.

The interior of the demodulator 38 may be a diversity reception system. In this case, the S / N detecting means may be taken out after the divitivity switching.

(Embodiment 6) FIG. 7 shows the configuration of a sixth embodiment of the present invention. In FIG. 7, the same elements as those of the sixth embodiment shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

That is, the difference from FIG. 6 is that the intermediate frequency level detecting means 42 for detecting the level of the intermediate frequency amplified by the intermediate frequency amplifier 37 is provided, and this intermediate frequency level is compared with a preset specified value. However, there is provided a judging means 43 for judging whether or not it is equal to or more than a specified value, and a control signal superposing means 41 for outputting a control signal for changing the gain of the booster antenna main body based on the judgment result.

According to the sixth embodiment, the automatic gain control of the variable gain amplifying means can be realized at a low cost with a small number of parts by using the RSSI signal for the signal meter.

(Embodiment 7) FIG. 8 shows the configuration of a seventh embodiment of the present invention. In this seventh embodiment,
Instead of changing the gain of the booster antenna main body, variable gain amplifying means is provided in the main body of the receiver so that the gain control according to the reception level from the transmitter is made variable.

In FIG. 8, the same elements as those of the fifth embodiment shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

That is, the difference from FIG. 6 is that the variable gain amplifying means 44 is provided between the high frequency filter 32 and the mixer 35, and the receiving level detecting means 45 for detecting the receiving level from the signal demodulated by the demodulator 38. And the reception level and a preset specified value are compared to determine whether or not the value is equal to or larger than the specified value, and based on the determination result, the variable gain amplifying means 4
The determination means 46 for outputting a control signal for varying the gain of No. 4 is provided.

According to the seventh embodiment as described above, it is possible to obtain the same effects as those of the first embodiment even in the receiving system which does not use the booster antenna.

In each of the above embodiments, the method of providing the receiving level detecting means, the judging means, the control signal superimposing means and the like in the receiver and the booster antenna main body has been described.
A dedicated device in which these means are collectively housed in a single housing may be used.

[0050]

As is apparent from the first embodiment, the present invention is used at a remote place by automatically changing the gain of the booster antenna according to the reception status of the signal from the transmitter. In this case, the gain can be increased to secure a sufficient reaching distance, and the gain can be reduced to prevent distortion when used in a close place.

Further, as is apparent from the second embodiment, the present invention has an effect that the conventional receiver can be used as it is by providing the booster antenna with the function shown in the first embodiment.

Further, in the present invention, as is apparent from the third and fourth embodiments, the number of transmitters used is increased,
When one receiver cannot handle, connect multiple receivers in cascade and give specific receiver one priority.
Since the final judgment and control of the reception level are performed by other receivers, even if multiple receivers are used, the gain control of the booster antenna according to the reception status of the signal from each transmitter becomes possible, It has the effect of preventing confusion.

Further, as is apparent from the fifth embodiment, the present invention uses the S / N ratio after demodulation to detect the reception level, so that even if an interfering wave exists near the desired wave, reception There is an effect that the level can be accurately detected.

Furthermore, according to the present invention, as is apparent from the sixth embodiment, by using the intermediate frequency level for detecting the reception level, the automatic gain control can be performed with a small number of parts by using the RSSI signal for the signal meter. It has an effect that can be realized at low cost.

Further, as is apparent from the seventh embodiment, the present invention provides a receiving system which does not use a booster antenna by providing a variable gain amplifying means and a judging means for varying the gain inside the receiver. Also, there is an effect that the reception level of the signal from the transmitter can be determined and the gain of the amplifying means can be controlled according to the reception condition of the transmitter.

[Brief description of drawings]

FIG. 1 is a block diagram of a receiving device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a determination procedure in the first embodiment.

FIG. 3 is a block diagram of a receiving device according to a second embodiment of the present invention.

FIG. 4 is a block diagram of a receiving device according to a third embodiment of the present invention.

FIG. 5 is a block diagram of a receiver according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram of a receiver according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram of a receiver according to a sixth embodiment of the present invention.

FIG. 8 is a block diagram of a receiver according to a seventh embodiment of the present invention.

FIG. 9 is a block diagram of a conventional receiving device.

[Explanation of symbols]

 11, 12 transmitter 13 booster antenna body 14 antenna element 15 high frequency filter 16 variable gain amplifying means 17, 17A, 17B, 47A, 47B receiver 18 coaxial cable 19, 20 reception demodulating means 21, 22 reception level detecting means 23 judging means 24 control signal superimposing means 25 reception level detecting means 26 judging means 27 distributor 27a distributing means 28A, 28B judging means 29, 29a, 29b cable 30 receiver body 31a input terminal 31b output terminal 32 high frequency filter 33 high frequency amplifier 34 local oscillator 35 Mixer 36 Intermediate frequency filter 37 Intermediate frequency amplifier 38 Demodulator 39 S / N detection means 40 Judgment means 41 Control signal superposition means 42 Intermediate frequency level detection means 43 Judgment means 44 Variable gain amplification means 45 Reception level Detecting means 46 Judging means

Claims (5)

[Claims] 1. A booster antenna having variable gain amplifying means capable of receiving and amplifying radio waves from a transmitter and varying the gain to be amplified by a control signal, and a booster antenna via a coaxial cable. A receiver that is connected and demodulates a received signal, wherein the receiver has a detection unit that detects a reception level of a signal from the transmitter;
Determination means for comparing the average value of the detected reception level with a preset preset value to determine whether or not it is a preset value or more;
A control signal superimposing means for superimposing a control signal for varying the gain of the booster antenna on the coaxial cable based on the result of the determination. 2. A booster antenna having variable gain amplifying means capable of receiving and amplifying a radio wave from a transmitter and varying the gain to be amplified by a control signal, and a booster antenna connected to the booster antenna and receiving signal. A receiver that demodulates the booster antenna, and the booster antenna detects a receiving level of a signal from the transmitter, and compares an average value of the detected receiving levels with a preset specified value. The receiving device is characterized in that it is provided with a judging means for judging whether or not the gain of the variable gain amplifying means is variable according to the judgment result. 3. A booster antenna having variable gain amplifying means capable of receiving and amplifying radio waves from a plurality of transmitters and varying the gain to be amplified by a control signal.
Distribution means for distributing the received signal from the booster antenna, and is connected to this distribution means via a coaxial cable,
A plurality of receivers for respectively receiving and demodulating the distributed signals, each of the receivers detecting means for detecting the reception level of the signal from the transmitter, the average value of the detected reception level And a preset predetermined value to determine whether or not it is a preset value or more, and a control signal for varying the gain of the booster antenna based on the determination result is superimposed on the coaxial cable. A control signal superimposing means is provided, and an input end of a specific judging means and other receivers for inputting the judgment result or the detection result of the reception level at each receiver to the judging means of one specific receiver. Whether or not the cable is connected to the output terminals of the judging means or the receiving level detecting means of each receiver. Determined, the receiving device, characterized in that the output terminal connection determining means for inhibiting the output operation of the corresponding control signal superimposing means only when it is determined the cable connections provided in each receiver. 4. A booster antenna having variable gain amplifying means capable of receiving and amplifying a radio wave from a transmitter and varying the gain to be amplified by a control signal, and the booster antenna via a coaxial cable. A receiver that is connected and demodulates a received signal is provided, and in the receiver, an S / N detecting unit that detects the S / N ratio of the demodulated signal, and the detected S / N ratio are preset. And a control signal superimposing means for superimposing a control signal for varying the gain of the booster antenna on the coaxial cable based on the result of the determination. A receiving device characterized by being provided. 5. A booster antenna having variable gain amplifying means capable of receiving and amplifying a radio wave from a transmitter and varying the gain to be amplified by a control signal, and the booster antenna via a coaxial cable. And a receiver that is connected and demodulates a received signal, wherein the receiver has an intermediate frequency level detecting means for detecting an intermediate frequency level thereof,
Judgment means for comparing the detected intermediate frequency level with a preset specified value to determine whether or not it is a specified value or more, and a control signal for varying the gain of the booster antenna based on this judgment result. A receiving device comprising a control signal superimposing means for superimposing on a coaxial cable.