JP6693831B2 - Receiver, spatial transmission system, reception control method, and reception control program - Google Patents

Description

  The present invention relates to a technique for transmitting a signal by propagating a modulated wave in the atmosphere.

  With the increase in communication speed and the increase in capacity, it is required to increase the capacity of wireless access networks. An optical space transmission system is drawing attention as a method for increasing the capacity of a wireless access network.

  In the optical free space transmission system, for example, a transmitter outputs an optical signal obtained by electro-optical conversion of an electric signal using a laser diode or the like into the atmosphere. Then, the receiving device photoelectrically converts the received optical signal using a photodiode or the like.

  An example of the optical space transmission technology is disclosed in Patent Document 1. The optical space transmission device of Patent Document 1 includes a transmitter, a receiver, and a transmission failure determination device. The transmitter sends the optical signal to free space. The receiver receives the optical signal transmitted by the transmitter from the free space. The transmission failure determination device determines a cause of a transmission failure that occurs in optical space transmission in free space. The transmission failure determination device includes a deterioration factor determination means and an alarm means. When the light receiving level at the receiver falls below the reference level, the decrease factor determining means determines whether the light receiving level is reduced to a predetermined recovery level or not by the decrease rate of the light receiving level and a certain period thereafter. Is monitored, and the cause of the decrease in the received light level is determined based on the result. Further, the reduction factor determination means determines that the light reception level has decreased due to the weather when the light reception level fluctuates up and down a predetermined number of times or more within a predetermined fluctuation period within a predetermined monitoring period. The alarm means issues an alarm when the light reception level at the receiver has not recovered to the return level or higher within a certain period after the light reception level falls below the reference level.

  As a result of the above configuration, the optical space transmission device of Patent Document 1 makes a detailed determination of a factor causing a decrease in the light-receiving level, and when a disconnection occurs, determines the factor causing a decrease in a short time before the disconnection. Issue only the necessary alerts.

  In the spatial transmission system, since the level of the received signal varies depending on the communication distance, it is necessary to amplify the signal with low noise and low distortion in a wide receiving level range from the minimum receiving level to the maximum receiving level. Therefore, in a spatial transmission system, an automatic gain control (AGC: Automatic Gain Control) function is generally used. The AGC function is a function for automatically adjusting the gain of amplification according to the level of the input signal.

  Patent Document 2 discloses an example of a spatial transmission technique having an AGC function. The receiving device of Patent Document 2 includes a gain control unit and a control unit. The gain control unit includes a first pilot signal transmitted as a signal having the same polarity through different transmission paths, and a second pilot signal transmitted as a signal having opposite polarities through different transmission paths. Adjust the signal power. The control unit controls the gain tracking characteristic of the gain control unit according to whether the data transmission method is MISO (Multiple Input Single Output) or SISO (Single Input Single Output).

  As a result of the above configuration, the receiving device of Patent Document 2 controls the gain so as not to follow the bias of the power even when the bias of the power appears due to the data transmission performed by MISO.

JP, 2004-172741, A JP 2012-191431 A

  In the optical space transmission device of Patent Document 1, the lowering factor determination unit lowers the light receiving level due to the weather when the light receiving level fluctuates up and down a predetermined number of times within a predetermined monitoring period with a fluctuation width of a certain value or more. To determine. However, for example, when precipitation is assumed as the weather, the fluctuation range and the number of fluctuations of the received light level are large, such as precipitation amount, type and size of water droplets, presence or absence of fog or cloud, change of wind direction, wind speed, etc. It is considered that it depends on the factor of, and it is difficult to determine the constant fluctuation range and the predetermined number of times under the combination of various factors. Therefore, the optical space transmission device of Patent Document 1 has a problem that precipitation detection accuracy is low.

  The present invention has been made in view of the above problems, and outputs a failure signal indicating the occurrence of a failure when a non-transient reduction of the reception level in the receiving device occurs, while accompanying a change in atmospheric conditions. The main purpose is to suppress the output of a failure signal with high accuracy when a temporary decrease in the reception level occurs.

  In one embodiment of the present invention, a receiving device receives a modulated wave transmitted by a transmitting device including a transmitting portion that transmits a modulated wave, the modulated wave being propagated in the atmosphere, and the received modulated wave, the received modulated wave. Receiving means for converting to an electric signal indicating the reception level of the wave and outputting the electric signal, and detecting a decrease in the receiving level based on the time series of the electric signal output by the receiving means, and receiving level based on the time series of the electric signal The fluctuation frequency component of is derived, and based on the reception level and the fluctuation frequency component, it is estimated whether or not the decrease in the detected reception level is transient, and it is estimated that the decrease in the reception level is not transient. In this case, a monitoring unit that outputs a failure signal indicating a failure and that suppresses the output of the failure signal when the decrease in the reception level is estimated to be transient.

  In one aspect of the present invention, a spatial transmission system includes a transmitter including a transmitter that transmits a modulated wave, and a receiver that receives the modulated wave transmitted by the transmitter in the atmosphere. In the space transmission system, the receiving device receives the modulated wave propagated through the atmosphere, the received modulated wave, a receiving means for converting and outputting to an electrical signal indicating the reception level of the received modulated wave, Detecting a decrease in the reception level based on the time series of the electric signal output by the receiving means, deriving a fluctuation frequency component of the reception level based on the time series of the electric signal, based on the reception level and the fluctuation frequency component , It is estimated whether the decrease in the detected reception level is transient, and if the decrease in the reception level is not transient, a failure signal indicating a failure is output and the decrease in the reception level is detected. Passing If it is estimated to be, and a monitoring means for inhibiting the output of the fault signal.

  In one aspect of the present invention, a reception control method receives a modulated wave that has propagated through the atmosphere, converts the received modulated wave into an electric signal indicating a reception level of the received modulated wave, and outputs the electric signal. A decrease in the reception level is detected based on the time series of the output electric signal, a fluctuation frequency component of the reception level is derived based on the time series of the electric signal, and it is detected based on the reception level and the fluctuation frequency component. It is estimated whether the decrease in reception level is transient, and if it is estimated that the decrease in reception level is not transient, a failure signal indicating a failure is output and the decrease in reception level is transient. If it is estimated that the output of the failure signal is suppressed.

  In one embodiment of the present invention, a reception control program or a recording medium in which the reception control program is stored is a modulation wave in which a modulation wave transmitted by a transmission device including a transmission unit that transmits a modulation wave is propagated in the atmosphere. Receiving the received modulated wave, converting the received modulated wave into an electric signal indicating the received level of the received modulated wave and outputting the electric signal, and detecting a decrease in the received level based on the time series of the output electric signal, The fluctuation frequency component of the reception level is derived based on the time series of the electric signal, and based on the reception level and the fluctuation frequency component, it is estimated whether the decrease in the detected reception level is transient or not, and the reception level If it is estimated that the decrease in the signal level is not transient, a failure signal indicating a failure is output, and if the decrease in the reception level is estimated to be transient, a monitoring process is performed to suppress the output of the failure signal. The con To be executed by the Yuta.

  According to the present invention, when a non-transient decrease in the reception level occurs in the receiving device, a failure signal indicating the occurrence of a failure is output, while a transient decrease in the reception level occurs due to a change in atmospheric conditions. There is an effect that the output of the failure signal can be suppressed with high accuracy when it occurs.

It is a block diagram which shows an example of a structure of the space transmission system in the 1st Embodiment of this invention. It is a block diagram which shows an example of a structure of the monitoring part in the 1st Embodiment of this invention, an AC coupling part, and an automatic gain control part. It is a flowchart which shows an example of operation | movement of the receiver in the 1st Embodiment of this invention. It is a block diagram which shows an example of a structure of the space transmission system in the 2nd Embodiment of this invention. It is a block diagram which shows an example of a structure of the space transmission system in the 3rd Embodiment of this invention. It is a block diagram which shows an example of the hardware constitutions which can implement | achieve the receiving apparatus in each embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, the same components are designated by the same reference numerals, and the description will not be repeated.
(First embodiment)
The configuration of this embodiment will be described.

  FIG. 1 is a block diagram showing an example of the configuration of a space transmission system according to the first embodiment of the present invention.

  The spatial transmission system 500 includes a transmitting device 100 and a receiving device 200. The transmitter 100 outputs an optical signal obtained by converting an electric signal into an electric light into the atmosphere. The receiving device 200 converts an optical signal received from the atmosphere into an electric signal.

  The transmitter 100 includes a light modulation driver 110 and a laser diode 120.

  The optical modulation driver 110 modulates an electric signal to be transmitted using transmission data.

  The laser diode 120 converts the modulated electric signal into an optical signal and outputs the optical signal to the atmosphere.

  The receiving device 200 includes a photodiode 210, a photovoltage converter 220, an amplifier 230, a high-speed analog-digital converter 240, a monitor 250, a transimpedance amplifier 260, an AC coupler 270, and an automatic gain controller. 280 and.

  The photodiode 210 converts an optical signal received from the atmosphere into a current.

  The photovoltage converter 220 converts the current output by the photodiode 210 into a voltage.

  The amplifier 230 amplifies the voltage output by the photovoltage converter 220.

  The high-speed analog-to-digital converter 240 samples the voltage amplified by the amplifier 230 at predetermined intervals and digitizes it. The digital signal output by the high-speed analog-digital converter 240 represents a time series of the reception level of the optical signal received by the photodiode 210.

  The monitoring unit 250 monitors the reception level of the optical signal received by the photodiode 210 based on the digital signal output by the high-speed analog-digital conversion unit 240. When the reception level decreases, the monitoring unit 250 determines the magnitude of the frequency component on the high frequency side in the fluctuation of the reception level (hereinafter, referred to as “variation frequency component”) based on the time series representing the reception level of the optical signal. ) Is derived, and whether or not the decrease in the reception level is transient is estimated based on the reception level and the fluctuating frequency component. For example, when the optical axis shift of the optical signal occurs between the transmitting device 100 and the receiving device 200, the decrease in the receiving level of the optical signal is not transient. In this case, the reception level of the optical signal decreases, but the frequency of fluctuations in the reception level hardly increases. Alternatively, for example, when precipitation occurs, the decrease in the reception level of the optical signal is transient. In this case, the reception level of the optical signal may decrease as in the case where the optical axis shift occurs, but the frequency of the change in the reception level due to the change with time of precipitation etc. Compared with the above, it is significantly increased. Therefore, the monitoring unit 250 determines that the decrease in the reception level is transient when, for example, the reception level of the optical signal decreases below a predetermined threshold and the fluctuation frequency component exceeds a predetermined threshold. presume.

  When it is estimated that the decrease in the reception level is not transient, the monitoring unit 250 outputs a failure signal indicating a failure of the spatial transmission system 500. On the other hand, when it is estimated that the decrease in the reception level is transient, the monitoring unit 250 suppresses the output of the failure signal, and the “AC coupling time constant” (described later) and the “AGC time constant” (described later). ) Decrease. In the latter case, the monitoring unit 250 may output a signal indicating a temporary decrease in the reception level in the spatial transmission system 500.

  The transimpedance amplifier 260 converts the current signal output from the photodiode 210 into a voltage signal and amplifies the voltage signal.

  The AC coupling unit 270 holds a changeable AC coupling time constant. The AC coupling unit 270 is controlled by the monitoring unit 250.

  The automatic gain control unit 280 holds a changeable AGC time constant. The automatic gain controller 280 is controlled by the monitor 250.

  That is, the transimpedance amplifier 260 can be regarded as an amplifier in which the output follow-up characteristic with respect to the input depends on the AC coupling time constant held by the AC coupling unit 270 and the AGC time constant held by the automatic gain control unit 280. You can

  The AC coupling time constant and the AC coupling time constant will be described.

  In general, a space transmission system is more susceptible to fluctuations in scattering or absorption due to particles in the atmosphere, fluctuations in the temperature distribution of the atmosphere, fluctuations in the propagation path of electromagnetic waves, etc., as compared with transmission systems using optical fibers. ..

  It is desirable that the spatial transmission system be able to cope with variations in the reception level of electromagnetic waves caused by these variations. Therefore, in a space transmission system, for example, it is possible to reduce the beam diameter of the electromagnetic wave on the transmitting side and increase the output of the electromagnetic wave on the transmitting side so as to secure a sufficient margin with respect to the minimum receiving level on the receiving side. Be seen. By these measures, in the space transmission system, the disconnection of the line due to the decrease of the reception level of the electromagnetic wave is suppressed.

  However, the above-mentioned measures have a problem that the reception device mistakenly recognizes that the reception level of the reception device is attenuated to the minimum reception level or less when the precipitation (fog, rainfall, snowfall) occurs as a failure.

  During precipitation, high frequency fluctuating frequency components at the reception level increase due to scattering or absorption by water particles in the atmosphere. Therefore, it is possible to highly accurately estimate whether or not the decrease in the reception level is transient due to precipitation, based on the high-frequency fluctuation frequency component in the reception level.

  In addition, the above-mentioned measures have a problem that the receiving device cannot follow the fluctuation of the receiving level due to the precipitation during the rain and the line is disconnected.

  Generally, in a receiving device, there are two parameters that determine the output follow-up characteristic with respect to the input, one is a time constant related to the low-frequency cutoff characteristic, and the other is a time constant related to the AGC function.

  The low-frequency cutoff characteristic includes the characteristic of a high-pass filter formed by alternating current (AC) coupling between a transimpedance amplifier (TIA) and an AGC circuit. A transimpedance amplifier is an amplifier that converts current into voltage. The transimpedance amplifier is connected to the output side of, for example, a photodiode. The AGC circuit is connected to the output side of the transimpedance amplifier, for example.

  The time constant related to the low-frequency cutoff characteristic is a time constant (AC coupling time constant) that defines the low-frequency cutoff frequency in the above-described high-pass filter. The AC coupling time constant is a time constant that determines the “homologous continuous proof strength” characteristic and the “level fluctuation proof strength” characteristic. The homo-code continuity proof strength and the level fluctuation proof strength are in a trade-off relationship. That is, the smaller the AC coupling time constant, the higher the homo-code continuity proof strength, but the lower the level fluctuation proof strength at high frequencies. Conversely, as the AC coupling time constant increases, the level fluctuation resistance at high frequencies improves, but the homo-code continuity resistance decreases.

  The time constant related to the AGC function is a time constant (AGC time constant) that defines the cutoff frequency in the above AGC circuit. In the AGC circuit, a relatively small AGC time constant is required for instantaneous response to the burst signal. On the other hand, in the AGC circuit, a relatively large AGC time constant is required to realize a low bit error rate (BER) in a continuous signal. That is, there is a trade-off relationship between the response to the burst signal and the low bit error rate in the continuous signal.

  As described above, in the space transmission system, it is desirable that the AC coupling time constant and the AGC time constant are optimized according to the state of the atmosphere. Therefore, in the spatial transmission system 500 of the present embodiment, the AC coupling time constant can be changed in the AC coupling section 270. Further, in the spatial transmission system 500 of the present embodiment, the automatic gain control unit 280 can change the AGC time constant.

  FIG. 2 is a block diagram showing an example of the configurations of the monitoring unit, the AC coupling unit, and the automatic gain control unit according to the first embodiment of the present invention.

  The monitoring unit 250 includes a fluctuation frequency monitoring unit 251, a time constant determination unit 252, a fluctuation level monitoring unit 253, a change necessity determination unit 254, and a time constant selection determination unit 255.

  The fluctuating frequency monitoring unit 251 monitors the fluctuating frequency component in the fluctuation of the reception level of the optical signal. Specifically, for example, the fluctuating frequency monitoring unit 251 collects the time series of the reception level of the optical signal for a predetermined time at predetermined time intervals. Then, the fluctuating frequency monitoring unit 251 derives the fluctuating frequency component in the predetermined frequency range from the collected reception level time series using the fast Fourier transform. In addition, at the time of precipitation, the fluctuating frequency component increases due to the change with time of the precipitation amount and the like.

  The time constant determination unit 252 determines whether or not to change the AC coupling time constant and the AGC time constant (hereinafter, also simply referred to as “time constant”) based on the fluctuating frequency component, and is optimal when the change is necessary. Select a time constant.

  The fluctuation level monitoring unit 253 monitors the absolute value of the reception level of the optical signal (hereinafter, referred to as “variation level”).

  The change necessity determination unit 254 confirms the margin with respect to the minimum reception level of the receiving device 200 based on the variation level, and determines whether the time constant needs to be changed.

  The time constant selection determination unit 255 determines the time constant based on the determination results by the time constant determination unit 252 and the change necessity determination unit 254.

  The AC coupling unit 270 can hold a plurality of AC coupling time constants 271, AC coupling time constants 272, ..., AC coupling time constants 27N (N is a natural number of 2 or more).

  The automatic gain control unit 280 can hold a plurality of AGC time constants 281, AGC time constants 282, ..., AGC time constants 28M (M is a natural number of 2 or more).

  The operation of this embodiment will be described.

  FIG. 3 is a flowchart showing an example of the operation of the receiving device according to the first embodiment of the present invention. Specifically, FIG. 3 is a flowchart showing an example of the operation of the monitoring unit 250. Note that the flowchart shown in FIG. 3 and the following description are examples, and the order of processing, the processing may be returned, or the processing may be repeated depending on the processing to be appropriately obtained.

  First, the monitoring unit 250 monitors the reception level of the optical signal received by the photodiode 210, the photovoltage conversion unit 220, the amplifier 230, and the high-speed analog-to-digital conversion unit 240 with respect to the optical signal propagated in the atmosphere (step). S110).

  Next, the monitoring unit 250 detects a decrease in the reception level based on the time series of the reception level of the received optical signal (step S120). When the decrease in the reception level is not detected (step S120: No), the reception device 200 returns to the process of step S110. When a decrease in the reception level is detected (step S120: Yes), the reception device 200 proceeds to the process of step S130.

  Subsequently, the monitoring unit 250 derives the variable frequency component of the reception level based on the time series of the reception level (step S130).

  Subsequently, the monitoring unit 250 estimates whether or not the detected decrease in the reception level is transient based on the reception level and the fluctuating frequency component (step S140). When the decrease in the reception level is not transient (step S140: No), the monitoring unit 250 outputs a failure signal (step S150) and ends the process. When the decrease in the reception level is transient (step S140: Yes), the monitoring unit 250 reduces the time constants in the AC coupling unit 270 and the automatic gain control unit 280 (step S160), and the process ends. To do.

  As described above, in the spatial transmission system 500 of the present embodiment, the monitoring unit 250 estimates whether or not the detected decrease in the reception level is transient based on the reception level and the fluctuating frequency component. .. Since high-frequency fluctuation frequency components in the reception level increase during precipitation, it is possible to highly accurately estimate whether or not the decrease in reception level is transient due to precipitation. Then, the monitoring unit 250 outputs a failure signal when the decrease in the reception level is not transient. On the other hand, the monitoring unit 250 does not output the failure signal when the decrease in the reception level is transient, such as during rainfall. Therefore, the spatial transmission system 500 of the present embodiment outputs a failure signal indicating the occurrence of a failure when the reception level of the receiving device is not transiently decreased, while the reception level is changed according to the change in atmospheric conditions. The effect of being able to suppress the output of the failure signal with high accuracy when a temporary decrease occurs

Further, in the spatial transmission system 500 of the present embodiment, the monitoring unit 250 estimates whether or not the detected decrease in the reception level is transient based on the reception level and the fluctuating frequency component. Then, the monitoring unit 250 reduces the time constant in the AC coupling unit 270 and the automatic gain control unit 280 when the decrease in the reception level is transient, such as during rainfall. By reducing the time constants in the AC coupling unit 270 and the automatic gain control unit 280, the distortion of the output electric signal is reduced, so that the occurrence of bit errors during precipitation is suppressed. Therefore, the space transmission system 500 of the present embodiment has an effect of suppressing the occurrence of a bit error when the reception level is temporarily reduced due to the change in atmospheric conditions.
(Second embodiment)
Next, a second embodiment of the present invention based on the first embodiment of the present invention will be described. In this embodiment, the validity verification result in the output signal of the automatic gain control unit is fed back to the monitoring unit.

  FIG. 4 is a block diagram showing an example of the configuration of the space transmission system according to the second embodiment of the present invention. The spatial transmission system 506 of this embodiment includes a transmitter 100 (not shown in FIG. 4) and a receiver 300.

  The reception device 300 includes a clock extraction circuit 310, an amplifier 320, a high-speed analog-to-digital conversion unit 330, and a validity verification unit 340 in addition to the components of the first embodiment. However, in the receiving device 300, the monitoring unit 250 in the first embodiment is replaced with the monitoring unit 256. Further, in the receiving device 300, the automatic gain control unit 280 in the first embodiment is replaced with the automatic gain control unit 286.

  The output of the automatic gain control unit 286 is balanced-transmitted using the positive polarity signal and the negative polarity signal. A signal on one side (a signal on the “(+)” side in FIG. 4) of the output of the automatic gain control unit 286 is branched by using a voltage dividing resistor. Hereinafter, the branched signal will be referred to as a “branch signal”. The other configuration of the automatic gain control unit 286 is the same as the configuration of the automatic gain control unit 280 in the first embodiment.

  The amplifier 320 amplifies the voltage of the branch signal.

  The high-speed analog-digital conversion unit 330 digitizes the voltage of the branch signal amplified by the amplifier 320 by sampling at a predetermined interval.

  The monitoring unit 256 monitors the state of the signal output by the automatic gain control unit 286 based on the digital signal output by the high speed analog-digital conversion unit 330.

  The clock extraction circuit 310 extracts the reception clock from the output of the automatic gain control unit 286. The voltage division ratio is determined according to the ratio between the resistance value of the voltage dividing resistor and the termination resistance component of the clock extraction circuit 310. Therefore, in order to reduce the influence on the received data, the resistance value of the voltage dividing resistor is preferably about 1/10 of the termination resistance component of the clock extraction circuit 310.

  The validity verification unit 340 verifies the validity of the branch signal. Specifically, the validity verification unit 340 verifies whether or not the selection of the AC coupling time constant or the AGC time constant is appropriate by measuring the duty ratio, the distortion, etc. of the branch signal, and the verification result is obtained. Output.

  The monitoring unit 256 optimizes the AC coupling time constant or the AGC time constant based on the verification result by the validity verification unit 340. The other configuration of the monitoring unit 256 is the same as the configuration of the monitoring unit 250 in the first embodiment.

  Other configurations in this embodiment are the same as the configurations in the first embodiment.

  As described above, the spatial transmission system 506 of this embodiment is the first embodiment of the present invention except that the validity verification result in the output signal of the automatic gain control unit 286 is fed back to the monitoring unit 256. It is the same as that of the spatial transmission system 500. Therefore, the spatial transmission system 506 of this embodiment has the same effect as the spatial transmission system 500 of the first embodiment of the present invention.

Further, in the spatial transmission system 506 of the present embodiment, the validity verification result in the output signal of the automatic gain control unit 286 is fed back to the monitoring unit 256. Therefore, the spatial transmission system 506 of the present embodiment has an effect that the receiving device 300 can output an electric signal with an optimized time constant.
(Third Embodiment)
Next, a third embodiment of the present invention, which is the basis of the first and second embodiments of the present invention, will be described.

  FIG. 5: is a block diagram which shows an example of a structure of the space transmission system in the 3rd Embodiment of this invention. The spatial transmission system 509 of this embodiment includes a transmitter 109 and a receiver 209.

  The transmission device 109 includes a transmission unit 119.

  The transmitter 119 transmits the modulated wave into the atmosphere. The modulated wave is a wave that propagates in the atmosphere and has straightness. The modulated wave is, for example, light, an electromagnetic wave having a short wavelength, or a sound wave.

  The receiving device 209 includes a receiving unit 229 and a monitoring unit 259.

  The reception unit 229 receives the modulation wave transmitted from the transmission device 109 and propagated in the atmosphere, converts the received modulation wave into an electric signal indicating the reception level of the received modulation wave, and outputs the electric signal. ..

  The monitoring unit 259 detects a decrease in the reception level based on the time series of the electric signal output by the receiving unit 229.

  Then, the monitoring unit 259 derives the fluctuating frequency component of the reception level based on the time series of the electric signal.

  Then, the monitoring unit 259 estimates whether or not the detected decrease in the reception level is transient based on the reception level and the fluctuating frequency component.

  Then, when it is estimated that the decrease in the reception level is not transient, the monitoring unit 259 outputs a failure signal indicating a failure of the spatial transmission system 509.

  On the other hand, when it is estimated that the decrease in the reception level is transient, the monitoring unit 259 suppresses the output of the failure signal.

  As described above, in the spatial transmission system 509 of the present embodiment, the monitoring unit 259 estimates whether or not the detected decrease in the reception level is transient based on the reception level and the fluctuating frequency component. .. Since high-frequency fluctuation frequency components in the reception level increase during precipitation, it is possible to highly accurately estimate whether or not the decrease in reception level is transient due to precipitation. Then, the monitoring unit 259 outputs a failure signal when the decrease in the reception level is not transient. On the other hand, the monitoring unit 259 does not output the failure signal when the decrease in the reception level is transient, such as during rainfall. Therefore, the spatial transmission system 509 of the present embodiment outputs a failure signal indicating the occurrence of a failure when the reception level of the receiving device is not transiently decreased, while the reception level is changed according to the change of the atmospheric condition. The effect of being able to suppress the output of the failure signal with high accuracy when a temporary decrease occurs

  The function of each unit of the receiving device 209 in the present embodiment may be implemented by being divided into a plurality of elements.

  Further, similarly to the receiving device 200 in the first embodiment, the receiving device 209 in the present embodiment causes the receiving level to be transiently decreased when it is estimated that the decrease in the receiving level is transient. A signal indicating that there is may be output.

  Further, the receiving device 209 in the present embodiment may further include an amplifying unit that amplifies and outputs the electric signal output by the receiving unit 229, similarly to the receiving device 200 in the first embodiment. Further, the amplification unit may have a changeable time constant regarding the output tracking characteristic with respect to the input. Furthermore, the monitoring unit 259 may decrease the time constant regarding the tracking characteristic when it is estimated that the decrease in the reception level is transient.

  In addition, the receiving device 209 according to the present exemplary embodiment, like the receiving device 206 according to the second exemplary embodiment, has an amplification unit that amplifies and outputs the electric signal output by the receiving unit 229, and the validity of the output of the amplification unit. It may further include a validity verification unit for verifying. Furthermore, the amplification section may have a changeable time constant regarding the output tracking characteristic with respect to the input. Furthermore, the monitoring unit 259 may decrease the time constant regarding the tracking characteristic when the decrease in the reception level is estimated to be transient. Further, the validity verification unit may feed back the validity verification result to the monitoring unit 259, and the monitoring unit 259 may optimize the time constant based on the fed back validity verification result.

  FIG. 6 is a block diagram showing an example of a hardware configuration capable of realizing the communication device according to each embodiment of the present invention.

  The receiving device 907 includes a storage device 902, a CPU (Central Processing Unit) 903, a keyboard 904, a monitor 905, and an I / O (Input / Output) 908, which are connected by an internal bus 906. .. The storage device 902 stores an operation program of the CPU 903 such as the monitoring unit 259. The CPU 903 controls the receiving device 907 as a whole, executes an operation program stored in the storage device 902, and executes a program such as the control unit 156 and transmits / receives data via the I / O 908. The internal configuration of the receiving device 907 described above is an example. The receiving device 907 may have a device configuration in which a keyboard 904 and a monitor 905 are connected as necessary.

  The receiving device in each of the embodiments of the present invention described above may be realized by a dedicated device, but may also be realized by a computer (information processing device). In this case, the computer reads out the software program stored in the storage device 902 to the CPU 903, and executes the read out software program in the CPU 903. In the case of each of the above-described embodiments, the software program concerned includes, as described above, a function of each unit of the receiving device 200 shown in FIG. 1 or 2, a function of each unit of the receiving device 300 shown in FIG. It suffices if the description that enables the functions of the respective units of the receiving apparatus 209 shown in FIG. 5 is realized. However, each of these units may include appropriate hardware. In such a case, the software program (computer program) can be regarded as constituting the present invention. Further, a computer-readable storage medium that stores the software program can be regarded as constituting the present invention.

  The present invention has been exemplarily described above with reference to the above-described embodiments and their modifications. However, the technical scope of the present invention is not limited to the scope described in each of the above-described embodiments and modifications thereof. It is obvious to those skilled in the art that various modifications and improvements can be added to the embodiment. In such a case, new embodiments with such changes or improvements may be included in the technical scope of the present invention. This is apparent from the matters described in the claims.

  INDUSTRIAL APPLICABILITY The present invention performs a process during precipitation in a spatial transmission system that uses spatial propagation of waves having straightness (light, electromagnetic waves of short wavelength, sound waves, etc.) and a transmission system that uses both spatial transmission and wired transmission. It can be used for various purposes.

100 transmitter 110 optical modulation driver 120 laser diode 200 receiver 210 photo diode 220 optical voltage converter 230 amplifier 240 high-speed analog-to-digital converter 250 monitor 251 fluctuating frequency monitor 252 time constant judging unit 253 fluctuation level monitor 254 change required Rejection determination unit 255 Time constant selection determination unit 260 Transimpedance amplifier 270 AC coupling unit 271 AC coupling time constant 1
272 AC coupling time constant 2
27N AC coupling time constant N
280 Automatic gain control unit 281 AGC time constant 1
282 AGC time constant 2
28M AGC time constant M
500 spatial transmission system 300 receiver 256 monitoring unit 286 automatic gain control unit 310 clock extraction circuit 320 amplifier 330 high-speed analog-to-digital converter 340 validity verification unit 506 spatial transmission system 109 transmitter 119 transmitter 209 receiver 229 receiver 259 monitor Part 509 Spatial transmission system 902 Storage device 903 CPU
904 keyboard 905 monitor 906 internal bus 907 receiver 908 I / O

Claims (8)

An electric signal indicating the reception level of the received modulated wave, the received modulated wave being received by the transmitting apparatus having a transmitting unit for transmitting the modulated wave Receiving means for converting to and outputting
Detecting a decrease in the reception level based on the time series of the electric signal output by the receiving means,
Deriving a variable frequency component of the reception level based on the time series of the electrical signal,
Based on the reception level and the fluctuating frequency component, it is estimated whether the detected decrease in the reception level is transient,
When it is estimated that the decrease in the reception level is not transient, a failure signal indicating a failure is output,
A receiving device comprising: a monitoring unit that suppresses the output of the failure signal when the decrease in the reception level is estimated to be transient. The monitoring unit estimates that the decrease in the reception level is transient when the reception level decreases below a first threshold value and the fluctuating frequency component exceeds a second threshold value. 1. The receiving device according to 1. Further comprising amplification means for amplifying and outputting the electric signal output by the receiving means,
The amplifying means has a changeable time constant regarding the output follow-up characteristic with respect to the input,
The receiving device according to claim 1, wherein the monitoring unit reduces the time constant related to the tracking characteristic when the decrease in the reception level is estimated to be transient. The amplifying means has a variable time constant for AC coupling,
The receiving device according to claim 3, wherein the time constant relating to the tracking characteristic includes a time constant relating to the AC coupling in the amplifying means. The amplifying means has a variable time constant for automatic gain control,
The receiving device according to claim 3 or 4, wherein the time constant regarding the tracking characteristic includes a time constant regarding the automatic gain control in the amplifying means. A transmitter having a transmitter for transmitting a modulated wave;
A spatial transmission system comprising: a receiving device that receives the modulated wave that has been transmitted through the atmosphere by the modulated wave transmitted by the transmitting device,
The receiving device is
Receiving means for receiving the modulated wave propagated through the atmosphere, converting the received modulated wave into an electric signal indicating the received level of the received modulated wave, and outputting the electric signal.
Detecting a decrease in the reception level based on the time series of the electric signal output by the receiving means,
Deriving a variable frequency component of the reception level based on the time series of the electrical signal,
Based on the reception level and the fluctuating frequency component, it is estimated whether the detected decrease in the reception level is transient,
When it is estimated that the decrease in the reception level is not transient, a failure signal indicating a failure is output,
A spatial transmission system comprising: a monitoring unit that suppresses the output of the failure signal when it is estimated that the decrease in the reception level is transient. Receiving a modulated wave propagated through the atmosphere, converting the received modulated wave into an electric signal indicating the received level of the received modulated wave, and outputting the electric signal;
Detecting a decrease in the reception level based on the time series of the output electric signal,
Deriving a variable frequency component of the reception level based on the time series of the electrical signal,
Based on the reception level and the fluctuating frequency component, it is estimated whether the detected decrease in the reception level is transient,
When it is estimated that the decrease in the reception level is not transient, a failure signal indicating a failure is output,
A reception control method of suppressing the output of the failure signal when it is estimated that the decrease of the reception level is transient. An electric signal indicating the received level of the received modulated wave, the received modulated wave being received by the transmitting apparatus having a transmitting unit for transmitting the modulated wave Receiving process to convert to and output
Detecting a decrease in the reception level based on the time series of the output electric signal,
Deriving a variable frequency component of the reception level based on the time series of the electrical signal,
Based on the reception level and the fluctuating frequency component, it is estimated whether the detected decrease in the reception level is transient,
When it is estimated that the decrease in the reception level is not transient, a failure signal indicating a failure is output,
A reception control program for causing a computer to execute a monitoring process for suppressing the output of the failure signal when it is estimated that the decrease in the reception level is transient.

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