JP2016158097A - Protection circuit and method of controlling same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a protection circuit capable of suppressing a state where a high-frequency signal with an excessive power is made to flow to a subsequent stage without complicating a circuit configuration.SOLUTION: A protection circuit is configured to comprise demultiplexing means 1, attenuation means 2, conversion means 3, and output control means 4. The demultiplexing means 1 demultiplexes an inputted high-frequency signal into a first signal and a second signal. The attenuation means 2 attenuates the second signal. The conversion means 3 converts the attenuated second signal into DC and outputs it as a third signal. The output control means 4 controls an output state of the first signal on the basis of a voltage of the third signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a protection circuit, and more particularly, to a protection circuit that operates only with passive elements in the previous stage of a circuit to be protected.

  Signal processing in a communication apparatus is also performed at high speed due to increased communication speed. For this reason, the signal processing circuit of the communication apparatus operates with a high clock. In a signal processing circuit of a communication device, the operating voltage is being lowered to prevent heat generation and to save power associated with an increase in clock.

  When the operating voltage of the signal processing circuit or the like of the communication device is lowered and miniaturization is performed for higher performance, the voltage resistance of the signal processing circuit or the like of the communication device is lowered. For example, when a high-power signal is input to a wireless communication device or the like, there is a possibility that a failure may occur in a signal processing circuit that configures the wireless communication device. In order to suppress such a failure, the reception circuit of the communication apparatus is often provided with a protection circuit for protecting each element of the reception circuit when an excessive power signal is input. When such a protection circuit is used, it is desirable that the configuration of the protection circuit be as simple as possible because the circuits used for downsizing of communication devices and the like are also being miniaturized.

  For example, when a high-power signal is input, the protection circuit protects the subsequent circuit by preventing current from flowing to the signal processing circuit provided in the subsequent stage. For example, a protection circuit as disclosed in Patent Document 1 is disclosed as a protection circuit that protects a subsequent circuit by preventing a current from flowing through the subsequent circuit.

  Patent Document 1 relates to a limiter device having a function of measuring the power of a received wave and attenuating the power based on the measurement result. The limiter device of Patent Literature 1 includes a directional coupler, a power measurement unit, an attenuator control unit, and a variable attenuator. In the limiter device of Patent Document 1, the power measurement unit measures the power of the received signal demultiplexed by the directional coupler, and calculates the power value. The control unit calculates the amount of attenuation based on the power value calculated from the measurement result, and controls the amount of attenuation of the variable attenuator so as to obtain the optimum power for the subsequent circuit. In Patent Literature 1, it is possible to suppress transmission of an excessive power signal to a subsequent circuit by controlling the variable attenuator based on the measurement result of the power value of the received wave.

JP2012-195676

  However, the technique of Patent Document 1 is not sufficient in the following points. In Patent Document 1, a received signal input to a limiter device is demultiplexed, power is measured, and a power value is calculated. Further, an optimal control amount corresponding to the power value is set by the control unit, and the received signal is attenuated by the variable attenuator. Therefore, the limiter device of Patent Document 1 requires processing for measuring power and calculating a value, and arithmetic processing for setting an attenuation amount based on the calculation result. In order to perform such processing, the limiter device of Patent Document 1 requires an arithmetic processing circuit and a power source for driving. For this reason, the limiter device of Patent Document 1 may be complicated in the configuration of the device.

  In addition, since it is necessary to calculate the power value based on the measurement result and to set the attenuation amount, it takes time until the reception signal is attenuated after the reception signal is input. For this reason, when a high-power high-frequency signal that requires protection is input to the protection circuit, the start of attenuation by the variable attenuator may be delayed and a high-power signal may be temporarily transmitted to the subsequent circuit. Therefore, the technique of Patent Document 1 is not sufficient as a technique for protecting a subsequent circuit when a high-power high-frequency signal is input without complicating the configuration of the apparatus.

  An object of the present invention is to obtain a protection circuit that can suppress a state in which a high-frequency signal of excessive power flows to the subsequent stage without complicating the circuit configuration.

  In order to solve the above problem, the protection circuit of the present invention includes a demultiplexing unit, an attenuation unit, a conversion unit, and an output control unit. The demultiplexing unit demultiplexes the input high-frequency signal into a first signal and a second signal. The attenuation means attenuates the second signal. The converting means converts the attenuated second signal into a direct current to form a third signal. The output control means controls the output state of the first signal based on the voltage of the third signal.

  According to the protection circuit control method of the present invention, the input high-frequency signal is demultiplexed into the first signal and the second signal, the second signal is attenuated, and the attenuated second signal is converted into a direct current. And the output state of the first signal is controlled based on the voltage of the third signal.

  According to the present invention, it is possible to suppress a state in which a high-frequency signal with excessive power flows to the subsequent stage without complicating the circuit configuration.

It is the figure which showed the outline | summary of the structure of the 1st Embodiment of this invention. It is the figure which showed the outline | summary of the structure of the 2nd Embodiment of this invention. It is the figure which showed the example of the structure of a part of circuit of the 2nd Embodiment of this invention. It is the figure which showed the example of the signal in the 2nd Embodiment of this invention. It is the figure which showed the example of the structure contrasted with this invention. It is the figure which showed the example of the signal in the structure contrasted with this invention. It is the figure which showed the outline | summary of the structure of the 3rd Embodiment of this invention.

(First embodiment)
A first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an outline of the configuration of the protection circuit of this embodiment. The protection circuit of this embodiment includes a demultiplexing unit 1, an attenuation unit 2, a conversion unit 3, and an output control unit 4. The demultiplexing unit 1 demultiplexes the input high-frequency signal into a first signal and a second signal. The attenuating means 2 attenuates the second signal. The conversion means 3 converts the attenuated second signal into a direct current to form a third signal. The output control means 4 controls the output state of the first signal based on the voltage of the third signal.

  In the protection circuit of the present embodiment, the second signal demultiplexed by the demultiplexing unit 1 is attenuated by the attenuating unit 2 and then converted into a direct current by the converting unit 3 to generate a third signal. Further, the output control means 4 controls the output state of the first signal based on the voltage of the third signal. In the protection circuit of the present embodiment, the output is controlled based on the third signal that has been subjected to only the attenuation and direct current processing after the demultiplexing of the input signal. Therefore, complicated signal processing is required to control the output. do not do. Therefore, in the protection circuit of this embodiment, the response of the change in the output intensity based on the third signal with respect to the change in the input signal does not deteriorate. Therefore, since the protection circuit of this embodiment can control the output state without causing a delay time, it is possible to avoid a state in which a high-power signal is sent to the subsequent circuit. Further, in the protection circuit of this embodiment, complicated signal processing is not required for the operation of attenuating the high-frequency signal, so that the circuit complexity can be suppressed. As a result, the protection circuit of this embodiment can suppress a state in which a high-power high-frequency signal flows to the subsequent stage without complicating the circuit configuration.

(Second Embodiment)
A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an outline of the configuration of the protection circuit of the present embodiment. The protection circuit 10 according to this embodiment includes a directional coupler 11, a limiter circuit 12, a fixed attenuator 13, and a power detection unit 14. The directional coupler 11, the limiter circuit 12, the fixed attenuator 13, and the power detection unit 14 of the present embodiment are all passive elements and do not require external power supply.

  The directional coupler 11 has a function of demultiplexing the input high frequency signal. The directional coupler 11 branches the high frequency signal input as the input signal S11 into two paths. The directional coupler 11 sends one of the signals demultiplexed into two to the limiter circuit 12 as a first demultiplexed signal S12. The first demultiplexing signal S12 is a signal for transmitting a high-frequency signal to a subsequent apparatus. Further, the directional coupler 12 sends the other signal to the fixed attenuator 13 as the second demultiplexed signal S14. The directional coupler 11 corresponds to the demultiplexing unit 11 of the first embodiment. In the present embodiment, a directional coupler is used as a high-frequency signal demultiplexing element, but other elements may be used as long as they can demultiplex a high-frequency signal.

  The limiter circuit 12 has a function of keeping the power of the signal output from the protection circuit 10 below a predetermined power. The limiter circuit 12 includes a diode whose anode is connected to the transmission path side of the high-frequency signal. The limiter circuit 12 may include a plurality of diodes. The cathode side of the diode is grounded. As the diode of the limiter circuit 12 of the present embodiment, a PIN (p-intrinsic-n) diode is used.

  In the limiter circuit 12 of this embodiment, a DC voltage is applied to the anode side of the PIN diode so that a high-frequency signal can pass through the PIN diode, so that the power output from the circuit is kept below a predetermined power. It is. The application of the DC voltage to the anode side of the PIN diode is performed by the DC voltage of the signal sent from the power detection unit 14 as the signal detection signal S16.

  The limiter circuit 12 of the present embodiment controls the intensity of the first demultiplexed signal S12 sent from the directional coupler 11 by the voltage of the signal detection signal S16, and outputs it as a protection circuit output signal S13. To do. That is, in the limiter circuit 12, the power of the signal output as the protection circuit output signal S13 is controlled by changing the current of the high-frequency signal flowing on the diode side by the voltage of the signal detection signal S16. The limiter circuit 12 corresponds to the output control means 4 of the first embodiment.

  FIG. 3 is a diagram illustrating an example of a circuit used as the limiter circuit 12. The limiter circuit shown in FIG. 3 includes two diodes. A transmission line is formed between the two diodes so as to have a predetermined impedance according to the circuit design. The diode is connected to a high-frequency signal transmission line on the anode side. The cathode side of the diode is grounded. The first demultiplexed signal S12 is input from the directional coupler 11 to the limiter circuit of FIG. Further, a protection circuit output signal S13 is output from the limiter circuit of FIG. A DC voltage sent from the power detector 14 as the signal detection signal S16 is applied to the anode side of the diode. When a current flows through the diode according to the magnitude of the DC voltage, the power of the protection circuit output signal S13 changes. Although FIG. 3 shows an example in which the signal detection signal S16 is input between two diodes, the number of diodes may not be two, and the input position of the signal detection signal S16 may be another location.

  The fixed attenuator 13 has a function of attenuating the input high frequency signal. The fixed attenuator 13 includes a resistance element having a predetermined resistance value. The fixed attenuator 13 attenuates the signal transmitted from the directional coupler 11 as the second demultiplexed signal S14 by the resistance element, and transmits the attenuated signal S15 to the power detector 14. The protection circuit 10 of the present embodiment suppresses complication of the circuit and delay in response speed by attenuating the input signal using a fixed attenuator. Since the fixed attenuator can be configured by connecting a resistance element, resistance variation is small. Therefore, the fixed attenuator can obtain a stable attenuation characteristic. Moreover, since it is comprised only with a resistive element, when an input voltage changes in a fixed attenuator, an output voltage also changes substantially simultaneously. The fixed attenuator 13 of this embodiment corresponds to the attenuating means 3 of the first embodiment.

  The power detection unit 14 has a function of converting an input AC signal into a direct current and outputting it. The power detection unit 14 of the present embodiment includes a PIN diode. The anode of the diode of the power detector 14 is connected to the directional coupler 11 side. The cathode of the diode of the power detection unit 14 is connected to the limiter circuit 12. That is, a DC voltage corresponding to the power of the AC signal input to the power detection unit 14 is applied to the limiter circuit 12.

  The characteristics of the diode used in the power detection unit 14 are set in consideration of the voltage value when the high-frequency signal of the upper limit power allowed in the subsequent circuit is attenuated by the fixed attenuator 13 and further converted into a direct current. The That is, the characteristics of the diode of the power detection unit 14 are set so that the diode of the limiter circuit 12 flows a current when a high-frequency signal with an upper limit power allowed in the subsequent circuit is input. Since the protection circuit of the present embodiment attenuates with the fixed attenuator 13, a diode that can obtain a predetermined output voltage with a high-frequency signal with lower power than that without the fixed attenuator 13 is used. Therefore, a diode having a characteristic that is sensitive to a change in a high-frequency signal can be used for the power detection unit 14 of the present embodiment.

  The power detection unit 14 converts the high-frequency signal sent from the fixed attenuator 13 as the attenuation signal S15 into a direct current, and sends it to the limiter circuit 12 as the signal detection signal S16. The power detection unit 14 corresponds to the conversion unit 3 of the first embodiment.

  Further, although the PIN diode is used for the power detection unit 14 of the present embodiment, a Schottky diode may be used instead of the PIN diode.

  The operation of the protection circuit 10 of this embodiment will be described. The high-frequency signal input to the protection circuit 10 as the input signal S11 is demultiplexed by the directional coupler 11, and the limiter circuit 12 and the fixed attenuator 13 are demultiplexed as the first demultiplexed signal S12 and the second demultiplexed signal S14. Each is entered.

  The high-frequency signal input from the directional coupler 11 to the limiter circuit 12 as the first demultiplexed signal S12 passes through the limiter circuit 12 as it is when the normal power allowed by the subsequent circuit or the like passes through the protection circuit 10 as it is. Is output as a protection circuit output signal S13. The high-frequency signal output from the protection circuit 10 as the protection circuit output signal S13 is input to a reception circuit or the like provided at the subsequent stage of the protection circuit 10.

  The high-frequency signal input as the second demultiplexed signal S14 from the directional coupler 11 to the fixed attenuator 13 is attenuated according to the magnitude of the signal power. The fixed attenuator 13 has an attenuation characteristic that satisfies the withstand voltage characteristic of the power detector 14 when a signal of power assumed as the maximum is input to the fixed attenuator 13. The fixed attenuator 13 is a voltage that causes the voltage value of the attenuated and DC signal to pass a current to the diode of the limiter circuit 12 when a high-frequency signal having an upper limit power value allowed by a subsequent device is input. It has an attenuation characteristic that becomes a value. The fixed attenuator 13 sends the attenuated high frequency signal to the power detector 14 as an attenuation signal S15.

  The high-frequency signal input to the power detector 14 as the attenuation signal S15 is converted into a direct current by the PIN diode provided in the power detector 14 and output. The signal output from the power detector 14 is sent to the limiter circuit 12 as a signal detection signal S16. The diode of the power detector 14 outputs a signal having a voltage value corresponding to the power of the high-frequency signal input to the power detector 14 and the characteristics of the diode.

  The DC voltage of the signal sent from the power detector 14 to the limiter circuit 12 as the signal detection signal S16 is applied to the diode of the limiter circuit 12. The DC voltage of the signal detection signal S16 is applied to the diode of the limiter circuit 12 so as to be a forward bias.

  The diode of the limiter circuit 12 causes a current to flow from the transmission path side of the high-frequency signal to the ground side when the forward bias, that is, the DC voltage value of the signal sent from the power detector 14 reaches a predetermined level. become. That is, the diode of the limiter circuit 12 functions as a conductive switch, and the high-frequency signal flows to the ground side.

  When the power of the input high-frequency signal is increased, the DC voltage applied to the limiter circuit 12 is increased and the diode flows more current, so that the power of the signal output from the limiter circuit 12 is decreased. . For this reason, when a high-power high-frequency signal is input, the limiter circuit 12 outputs almost no high-frequency signal or weakens the power. The diode of the limiter circuit 12 is designed so that the output current is very small up to the vicinity of the predetermined voltage value Vth, and the current value increases rapidly when Vth is exceeded.

  The high-frequency signal whose power has been attenuated by the limiter circuit 12 is output as the protection circuit output signal S16. The protection circuit output signal S16 output from the limiter circuit 12 is output from the protection circuit 10 and sent to a receiving circuit of a communication device provided with the protection circuit 10 or the like. Through the operation as described above, the protection circuit 10 of the present embodiment functions as a protection circuit for a communication device or the like at the subsequent stage.

  FIG. 4 is a diagram schematically showing the magnitude of signal power in the protection circuit 10 of the present embodiment. The uppermost “input signal power” in FIG. 4 indicates the magnitude of the power of the input signal S11 in the vertical direction. The “operation of the limiter circuit” in the second stage from the top in FIG. 4 schematically shows a change in the voltage applied to the limiter circuit 12, that is, the voltage of the signal detection signal 16. In the lower part of FIG. 4, “output signal power” indicates the magnitude of the power of the output signal from the protection circuit 10, that is, the protection circuit output signal S13, with the vertical direction being the power. The horizontal direction in FIG. 4 indicates time. In the example of FIG. 4, when the power of the input signal increases, the voltage applied to the limiter circuit 12 is also in the high state at the same time. Therefore, the power of the output signal is suppressed following the operation of the input signal and the limiter circuit 12.

  FIG. 5 is a diagram showing an example of a protection circuit having a structure compared with this embodiment. The protection circuit 50 shown in FIG. 5 includes a directional coupler 51, a limiter circuit 52, an analog / digital converter 53, and a signal processing circuit 54. The configurations and functions of the directional coupler 51 and the limiter circuit 52 are the same as those of the protection circuit 10 of the present embodiment. The analog-digital converter 53 converts the high-frequency signal input from the directional coupler 51 into a digital signal and sends it to the signal processing circuit 54. The signal processing circuit 54 determines whether the power of the high-frequency signal is higher than a predetermined threshold based on the value of the signal sent as a digital signal from the analog / digital converter 53. When the power of the high frequency signal is higher than the predetermined threshold value, the signal processing circuit 54 sends a signal in the high state to the limiter circuit 52 in order to apply a DC bias to the diode. When the limiter circuit 52 receives the signal in the high state, the high-frequency signal flows to the ground side through the diode, and the power of the high-frequency signal output to the subsequent stage is suppressed.

  FIG. 6 is a diagram schematically showing the strength of the protection circuit 50 configured as shown in FIG. The “input signal power” at the top of FIG. 6 indicates the magnitude of the power of the input signal with the vertical direction being the power. The “operation of the limiter circuit” in the second stage from the top in FIG. 6 schematically shows a change in the voltage applied to the limiter circuit 52, that is, the power of the output signal of the signal processing circuit 54. In the lower part of FIG. 6, “output signal power” indicates the magnitude of the power of the output signal from the protection circuit 50 in the vertical direction. The horizontal direction in FIG. 6 indicates time.

  In the example of FIG. 6, after the power of the input signal is increased, the voltage applied to the limiter circuit 52 is in a high state with a slight delay. For this reason, the power of the output signal is suppressed after a while after the input signal increases. As a result, in the protection circuit 50 in the example of FIG. 5, a time that cannot be protected, that is, a time during which a high-frequency signal with high power flows to the subsequent stage occurs. Therefore, in the protection circuit 50 of the example of FIG. 5, there is a possibility that a high-frequency signal with high power is input to the subsequent device and the element is destroyed. In the protection circuit 10 of the present embodiment, when the power of the input signal increases, the power of the protection circuit output signal S16 is immediately suppressed, so that a high-frequency signal with high power is not input to the subsequent device.

  The protection circuit 10 according to the present embodiment attenuates one of the high-frequency signals that has been demultiplexed by the directional coupler 11 and demultiplexed by the fixed attenuator 13. In addition, the protection circuit 10 of the present embodiment converts the high-frequency signal attenuated by the power detector 14 into a direct current and applies a direct-current voltage to the diode of the limiter circuit 12, thereby preventing the high-frequency signal input to the limiter circuit 12 side. The output is controlled. That is, the output is controlled using a DC voltage generated based on the input high-frequency signal. By adopting such a configuration, the protection circuit of the present embodiment can suppress the delay time until the output suppression starts, and therefore, when a high-power high-frequency signal is input, A state where a high power signal is output can be avoided.

  Since the fixed attenuator 13 is provided in front of the protection circuit and the detection unit 14 of the present embodiment, it is possible to suppress the occurrence of an abnormality in the diode of the detection unit 14 even when a high power high frequency signal is input. it can. In addition, since the protection circuit 10 of the present embodiment is composed of passive elements, no power supply is required when performing the above operation. Since the protection circuit 10 according to the present embodiment does not require an arithmetic element, a power supply, or the like, the circuit configuration can be simplified. As described above, the protection circuit according to the present embodiment can suppress a state in which a high-frequency signal with high power flows to the subsequent stage without complicating the circuit configuration.

(Third embodiment)
A third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 7 shows an outline of the configuration of the receiving apparatus of this embodiment. In the second embodiment, only the protection circuit is shown, but in the present embodiment, a wireless communication reception device including the protection circuit and the reception circuit will be described.

  The receiving device 20 of this embodiment includes a protection circuit 21, a receiving circuit 22, and an antenna 23.

  The protection circuit 21 includes a directional coupler 31, a limiter circuit 32, a fixed attenuator 33, and a power detector 34. The configurations and functions of the directional coupler 31, the limiter circuit 32, the fixed attenuator 33, and the power detector 34 of the present embodiment are the same as the parts having the same names in the second embodiment. Further, the input signal S31, the first demultiplexing signal S32, the protection circuit output signal S33, the second demultiplexing signal S34, the attenuation signal S35, and the signal detection signal S36 of the present embodiment have the same names as those of the second embodiment. It has the same function as the signal. In the protection circuit 21 of the present embodiment, the signal detection signal S36 output from the power detector 34 is branched and sent to the receiving circuit 22 in addition to the limiter circuit 32.

  The reception circuit 22 includes an analog / digital conversion circuit 41, a signal processing circuit 42, and a reception level detection circuit 43.

  The analog digital conversion circuit 41 has a function of converting a high-frequency signal input from the protection circuit 21 into a digital signal. The analog-digital conversion circuit 41 converts the high-frequency signal input as the protection circuit output signal S36 from the protection circuit 21 into a digital signal and outputs the digital signal to the signal processing circuit 42 as the conversion signal S41.

  The signal processing circuit 42 has a function of performing processing such as decoding of an input signal. Further, the signal processing circuit 42 has a function of determining the state of the communication path based on information on the strength of the received signal transmitted from the reception level detecting circuit 43.

  The signal processing circuit 42 performs processing such as distortion correction, error correction, and decoding of the signal input as the converted signal S41, and generates a signal in a format that is used in a device subsequent to the receiving circuit 22. Further, the signal processing circuit 42 refers to the information on the power of the reception signal transmitted as the reception level signal S42 from the reception level detection circuit 43 when the signal cannot be decoded. When the power of the reception signal indicated as a voltage value in the reception level signal S42 is higher than a predetermined threshold value, the signal processing circuit 42 determines that the signal power is suppressed by the protection function of the protection circuit 21. The predetermined threshold is set as a threshold for determining the higher power side of the signal. When the power of the received signal is low, the signal processing circuit 42 determines that there is no received signal or that the power of the radio signal is low. Based on the determination result of the signal state, the signal processing circuit 42 performs processing by changing a threshold for identifying the signal, a filter condition, and the like.

  The signal processing circuit 42 may output information based on the determination result. For example, when the signal strength is too strong and the protection function is working, information indicating that the signal power is high is output. The communication device can request adjustment of the power of the radio wave transmitted to the communication device on the transmission side based on the information.

  The reception level detection circuit 43 has a function of sending information on the power value of the radio signal to the signal processing circuit 42. The reception level detection circuit 43 converts the voltage value sent from the protection circuit 21 as the signal detection signal S36 into the power value of the signal input to the antenna 23. The reception level detection circuit 43 stores in advance information on the characteristics of each element of the protection circuit 21. The reception level detection circuit 43 sends information on the calculated power value of the radio signal to the signal processing circuit 42 as a reception level signal S42.

  The antenna 23 has a function of receiving a radio signal and converting it into an electrical signal. When the antenna 23 receives a radio signal, it converts it into an electrical signal and sends it to the protection circuit 21 as an input signal S31.

  The operation of the receiving apparatus of this embodiment will be described. When receiving a high-frequency radio signal, the antenna 23 converts it into an electrical signal and sends it to the protection circuit 21 as an input signal S31. The high-frequency signal input to the protection circuit 21 is demultiplexed by the directional coupler 31, and is input to the limiter circuit 32 and the fixed attenuator 34 as the first demultiplexed signal S31 and the second demultiplexed signal S34, respectively. .

  The high-frequency signal input from the directional coupler 31 to the limiter circuit 32 as the first demultiplexed signal S31 passes through the limiter circuit 32 as it is when the power is at a normal height, and is output from the protection circuit 21 to the protection circuit output signal. Output as S33. The protection circuit output signal S33 output from the protection circuit 21 is input to the reception circuit 22. The protection circuit output signal S33 input to the reception circuit 22 is sent to the analog-digital conversion circuit 41. The analog-digital conversion circuit converts the input high-frequency signal into a digital signal and sends it to the signal processing circuit 42 as a conversion signal S41. When the converted signal S41 is input, the signal processing circuit 42 performs processing such as distortion correction, error correction, and decoding of the input signal. When the signal processing circuit 42 performs decoding or the like of the signal, the signal processing circuit 42 sends the signal generated by performing the decoding or the like to another circuit of the receiving apparatus.

  The high-frequency signal input as the second demultiplexed signal S34 from the directional coupler 31 to the fixed attenuator 33 is attenuated according to the power level of the signal. The fixed attenuator 33 sends the attenuated high frequency signal to the power detector 34 as an attenuation signal S35. The high-frequency signal input to the power detector 34 as the attenuation signal S35 is converted into a direct current. When the power detector 34 converts the input signal into a direct current, the power detector 34 sends the signal to the limiter circuit 32 and the reception level detection circuit 42 as a signal detection signal S36.

  The diode of the limiter circuit 32 is forward biased, that is, when the DC voltage value of the signal sent from the power detector 34 as the signal detection signal S36 becomes a predetermined magnitude, the high-frequency signal transmission path side is changed to the ground side. Current will flow. When the DC voltage applied to the limiter circuit 32 is increased, the diode causes a current to flow, so that the power of the signal output from the limiter circuit 32 is reduced and the function as a protection circuit is exhibited.

  The signal detection signal S36 is also sent to the reception level detection circuit 42. The reception level detection circuit 42 measures the voltage of the signal detection signal S36 received from the power detector 34 to calculate the power value of the reception signal, and sends information about the calculated power value of the signal to the signal processing circuit 42. Send as S42.

  The signal processing circuit 42 refers to the information on the power value of the reception signal sent as the reception level signal S42 from the reception level detection circuit 43 when the signal cannot be decoded. When the power of the received signal is higher than the predetermined threshold, the signal processing circuit 42 determines that the signal level is suppressed by the protection function of the protection circuit 21. The predetermined threshold value is set as a threshold value for determining the higher power side. When the power of the received signal is low, the signal processing circuit 42 determines that there is no received signal or that the power of the radio signal is low.

  Based on the determination result of the signal state, the signal processing circuit 42 performs processing by changing a threshold for identifying the signal, a filter condition, and the like. For example, when the power of the signal of the reception level signal S21 is low, the signal processing circuit 42 prioritizes signal detection over processing speed by performing processing that lowers the signal detection threshold or processing that changes the filter condition. Perform the action. For example, when the power of the signal is high, the signal processing circuit 42 performs an operation giving priority to noise reduction.

  Since the receiving circuit 22 of the receiving apparatus of this embodiment includes the protection circuit 21 in the previous stage, even when a high-power high-frequency signal is input to the antenna 23, a signal with high power is not input. . Therefore, in the receiving apparatus of this embodiment, the receiving circuit 22 can be protected without causing abnormalities in the elements of the protection circuit 21 and the receiving circuit 22. That is, also in the receiving apparatus of the present embodiment, it is possible to suppress a state in which a high-power high-frequency signal flows to the receiving circuit 22 at the subsequent stage without causing element abnormality or the like.

  In addition, since the receiving circuit 22 receives a signal generated based on the power of the high-frequency signal from the power detector 34 of the protection circuit 21, whether the reception circuit 22 is caused by the protection circuit 21 when the input signal becomes weak. It can be determined whether it depends on the state of the radio signal. As a result, the receiving circuit 22 can perform signal processing according to the state.

  Further, since the protection circuit 21 of the present embodiment is also composed of only passive elements, the device configuration is not complicated. As described above, the receiving apparatus of this embodiment can suppress a state in which a high-frequency signal with excessive power flows through the receiving circuit without complicating the configuration of the protection circuit.

DESCRIPTION OF SYMBOLS 1 Splitting means 2 Attenuating means 3 Conversion means 4 Output control means 10 Protection circuit 11 Directional coupler 12 Limiter circuit 13 Fixed attenuator 14 Power detector 21 Protection circuit 22 Reception circuit 23 Antenna 31 Directional coupler 32 Limiter circuit 33 Fixed attenuator 34 Power detector S11 Input signal S12 First demultiplexing signal S13 Protection circuit output signal S14 Second demultiplexing signal S15 Attenuation signal S16 Signal detection signal S31 Input signal S32 First demultiplexing signal S33 Protection circuit output Signal S34 Second demultiplexing signal S35 Attenuation signal S36 Signal detection signal S41 Conversion signal S42 Reception level signal

Claims (10)

Demultiplexing means for demultiplexing an input high-frequency signal into a first signal and a second signal;
Attenuating means for attenuating the second signal;
Conversion means for converting the attenuated second signal into a third signal by direct current;
A protection circuit comprising: output control means for controlling an output state of the first signal based on a voltage of the third signal.   The protection circuit according to claim 1, wherein the attenuation unit attenuates the second signal with a fixed attenuator.   The converting means generates the third signal having a voltage value corresponding to the intensity of the second signal by inputting the attenuated second signal to the diode from the anode side. The protection circuit according to claim 1 or 2.   The output control means applies the voltage of the third signal to the anode side of a diode whose anode side is connected to the transmission path side of the first signal and whose cathode side is grounded. The protection circuit according to any one of 1 to 3. A protection circuit according to any one of claims 1 to 4;
Signal processing means for performing signal processing using the first signal output from the protection circuit as a received signal;
A communication apparatus comprising:   6. The communication apparatus according to claim 5, further comprising reception control means for controlling the signal processing based on the third signal. The input high-frequency signal is demultiplexed into a first signal and a second signal,
Attenuating the second signal;
The attenuated second signal is converted to a direct current as a third signal,
A control method of a protection circuit, wherein an output state of the first signal is controlled based on a voltage of the third signal.   The method for controlling a protection circuit according to claim 7, wherein the second signal is attenuated by a fixed attenuator.   9. The third signal having a voltage value corresponding to the intensity of the second signal is generated by inputting the attenuated second signal to the diode from the anode side. The control method of the protection circuit in any one.   A voltage of the third signal is applied to an anode side of a diode whose anode side is connected to the transmission path side of the first signal and whose cathode side is grounded, thereby controlling an output state of the first signal. A method for controlling a protection circuit according to any one of claims 7 to 9.

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