Receiving device

Abstract

To provide a receiving device that can obtain sufficient reception intensity for radio waves of a target frequency when desensitization occurs.SOLUTION: A receiving device includes: a tuning circuit connected to an antenna mounted on a mobile body and capable of receiving radio broadcast waves in multiple frequency bands; an amplifier circuit connected to an output side of the tuning circuit; a switch element provided between the antenna and a reference potential point; a first control unit that turns on the switch element when an electric field of the radio waves received by the antenna is equal to or greater than a first threshold; an AGC amplifier connected to the antenna; and a keyed AGC circuit connected to the AGC amplifier. Therein the keyed AGC circuit reduces a gain of the AGC amplifier when the electric field of the radio waves received by the antenna becomes smaller than a second threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a receiving device. [Background technology]

[0002] Conventionally, there has been a mobile receiving terminal device that is mounted on a mobile body and receives broadcast waves to demodulate a desired broadcast signal, characterized by having an AGC circuit that performs AGC on the broadcast waves, and control means that detects whether intermodulation interference has occurred and changes the operation of the AGC circuit when the intermodulation interference is detected (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-129576 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a conventional mobile receiving terminal device, if the gain of the AGC amplifier is increased in a situation where the electric field of radio waves of a frequency different from the target frequency is strong, sensitivity suppression occurs and sufficient reception strength of the radio waves of the target frequency cannot be obtained.

[0005] Therefore, an object of the present invention is to provide a receiving device that can obtain sufficient reception strength of radio waves of a target frequency when sensitivity suppression occurs. [Means for solving the problem]

[0006] A receiving device according to an embodiment of the present disclosure includes a tuning circuit connected to an antenna mounted on a mobile body and capable of receiving radio broadcast waves in multiple frequency bands, an amplifier circuit connected to the output side of the tuning circuit, a switch element arranged between the antenna and a reference potential point, a first control unit that turns on the switch element when the electric field of the radio waves received by the antenna is equal to or greater than a first threshold, an AGC amplifier connected to the antenna, and a keyed AGC circuit connected to the AGC amplifier, and the keyed AGC circuit reduces the gain of the AGC amplifier when the electric field of the radio waves received by the antenna becomes smaller than a second threshold. [Effects of the Invention]

[0007] It is possible to provide a receiving device that can obtain sufficient reception strength of radio waves of a target frequency when desensitization occurs. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a circuit configuration of a receiving device 100 according to an embodiment. [Figure 2] 10 is a flowchart showing an example of processing executed by the receiving device 100. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the receiving device of the present disclosure is applied will be described.

[0010] <Embodiment> 1 is a diagram showing an example of a circuit configuration of a receiving device 100 according to an embodiment. The receiving device 100 is mounted on a vehicle and connected between an antenna 10 and a receiving circuit 20 of the vehicle. The vehicle is, for example, an automobile such as an EV (Electric Vehicle), a PHEV (Plug-in Hybrid Electric Vehicle), an HV (Hybrid Vehicle), or a vehicle powered by an internal combustion engine. The vehicle may also be a train, etc. The vehicle is an example of a moving object.

[0011] As an example, antenna 10 is an antenna capable of receiving AM (Amplitude Modulation) radio broadcast waves and FM (Frequency Modulation) radio waves. In reality, there are separate antennas for receiving AM radio broadcast waves and FM radio broadcast waves, but for simplicity's sake, they are shown as one antenna in Fig. 1. Hereinafter, when there is no particular distinction between AM radio broadcast waves and FM radio broadcast waves, they will simply be referred to as radio broadcast waves.

[0012] In addition, the following describes a configuration in which the receiving device 100 is capable of receiving AM radio broadcast waves and FM radio broadcast waves, but it may also be configured to receive IBOC, DAB (Digital Audio Broadcast), HD-Radio, etc. instead of FM radio broadcast waves.

[0013] The receiving circuit 20 is mounted on the vehicle and extracts and outputs an audio signal from a radio broadcast wave received by the antenna 10. The receiving circuit 20 is connected to a speaker and the like.

[0014] Receiving device 100 includes, as its main components, input terminal 101, output switching unit 102, output terminal 103, tuning circuits 110A and 110B, RF (Radio Frequency) amplifiers 120A and 120B, and response setting units 125A and 125B. Receiving device 100 also includes, as its main components, AGC amplifiers 131A and 131B, AGC detection units 132A and 132B, AGC driving units 133A and 133B, FETs (Field Effect Transistors) 141A and 141B, damping circuits 142A and 142B, keyed AGC circuits 150A and 150B, switching unit 160A, and bus data line 170.

[0015] Of these, components with a subscript A are components for AM (Amplitude Modulation) radio broadcasting, and components with a subscript B are components for FM (Frequency Modulation) radio broadcasting. The RF amplifiers 120A and 120B are an example of an amplifier circuit. The response setting units 125A and 125B are an example of a second control unit. The FETs 141A and 141B are an example of a switch element. The damping circuits 142A and 142B are an example of a first control unit.

[0016] The receiving device 100 includes capacitors C1 and C2, coils L1, L2, and L3 as components other than those described above.

[0017] <Input terminal 101> Input terminal 101 is an input terminal of receiving device 100, and is connected to antenna 10 outside receiving device 100. Inside receiving device 100, input terminal 101 is connected to an input section of a circuit for AM radio broadcast waves (a circuit including coil L4) and an input section of a circuit for FM radio broadcast waves (a circuit including capacitor C2).

[0018] In the circuit for AM radio broadcast waves, input terminal 101 is connected via coil L4 and capacitor C1 to input terminal 111A of tuning circuit 110A, the input terminal of AGC amplifier 131A, and the drain of FET 141A. A capacitor is inserted in series before the input terminal of AGC amplifier 131A.

[0019] Coils L1 and L2 are connected in series to a line branching from between capacitor C1 and input terminal 111A of tuning circuit 110, with coil L2 connected to ground. Ground is an example of a reference potential point.

[0020] In the circuit for FM radio broadcast waves, input terminal 101 is connected via capacitor C2 to input terminal 111B of tuning circuit 110B, the input terminal of AGC amplifier 131B, and the drain of FET 141B. A capacitor is inserted in series before the input terminal of AGC amplifier 131B. One end of coil L3 is connected to a line branching from between capacitor C2 and input terminal 111B of tuning circuit 110B, and the other end of coil L3 is connected to ground.

[0021] <Output Switching Unit 102 and Output Terminal 103> The output switching unit 102 is an output switch having two input terminals connected to the output terminals of the RF amplifiers 120A and 120B, respectively, an input terminal to which a switching signal is input from the bus data line 170, and one output terminal connected to the output terminal 103. The output switching unit 102 outputs the radio broadcast wave input from either the RF amplifiers 120A or 120B to the output terminal 103 in accordance with the switching signal input from the bus data line 170. The output terminal 103 is connected to the receiving circuit 20.

[0022] <Tuning circuit 110A> Tuning circuit 110A has an input terminal 111A, an output terminal 112A, and a plurality of capacitor arrays (CAPs). Tuning circuit 110A is configured with an integrated circuit (IC) and has a plurality of capacitor arrays provided between input terminal 111A and output terminal 112A. The plurality of capacitor arrays are configured with a state machine of a logic circuit, and the capacitance between input terminal 111A and output terminal 112A can be changed by switching a plurality of switchable switches (FETs). Output terminal 112A is connected to the input terminal of RF amplifier 120A.

[0023] <Tuning circuit 110B> Tuning circuit 110B has an input terminal 111B, an output terminal 112B, and a plurality of capacitor arrays (CAPs), and has the same configuration as tuning circuit 110A. Output terminal 112B is connected to the input terminal of RF amplifier 120B.

[0024] <RFアンプ120A> RF amplifier 120A amplifies the AM radio broadcast wave output from tuning circuit 110A and outputs the amplified signal to output switching unit 102. RF amplifier 120A is connected to response setting unit 125A, and the gain of RF amplifier 120A is variably controlled by response setting unit 125A.

[0025] <RFアンプ120B> RF amplifier 120B amplifies the FM radio broadcast wave output from tuning circuit 110B and outputs it to output switching unit 102. RF amplifier 120B is connected to response setting unit 125B, and the gain of RF amplifier 120B is variably controlled by response setting unit 125B.

[0026] <Response setting unit 125A> The response setting unit 125A controls the gain of the RF amplifier 120A by changing the time constant of the RF amplifier 120A based on time constant setting data input from the bus data line 170 or a drive signal input from the AGC drive unit 133A. The time constant setting data is data for setting the time constant of the RF amplifier 120A to suit, for example, the destination of the vehicle. Furthermore, the time constant set by the drive signal differs depending on the attack / release of the damping circuit 142A.

[0027] <Response setting unit 125B> The response setting unit 125B controls the gain of the RF amplifier 120A by changing the time constant of the RF amplifier 120B based on time constant setting data input from the bus data line 170 or a drive signal input from the AGC drive unit 133B. The time constant setting data is data for setting the time constant of the RF amplifier 120A according to, for example, the destination of the vehicle. Furthermore, the time constant set by the drive signal differs depending on the attack / release of the damping circuit 142B.

[0028] <AGCアンプ131A> The input terminal of the AGC amplifier 131A is connected to the input terminal 101 via the capacitor C1 and the coil L4, and the output terminal is connected to the AGC detection unit 132A. Also, the keyed AGC circuit 150A is connected to the AGC amplifier 131A. The AGC amplifier 131A automatically controls the gain according to the intensity of the input signal.

[0029] <AGC amplifier 131B> The input terminal of the AGC amplifier 131B is connected to the input terminal 101 via the capacitor C2, and the output terminal is connected to the AGC detection unit 132B. Also, the keyed AGC circuit 150B is connected to the AGC amplifier 131B. The AGC amplifier 131B automatically controls the gain according to the intensity of the input signal.

[0030] <AGC detection unit 132A> Based on the output of the AGC amplifier 131A, the AGC detection unit 132A obtains the reception level of the radio wave (AM radio broadcast wave) received by the antenna 10 and outputs it to the AGC drive unit 133A. The sensitivity of the AGC detection unit 132A is set by the AMAGC sensitivity setting command input from the bus data line 170 and can be changed by the AMAGC sensitivity setting command. Also, the on / off sensitivity of the AGC is also set by the AMAGC sensitivity setting command.

[0031] <AGC detection unit 132B> Based on the output of the AGC amplifier 131B, the AGC detection unit 132B obtains the reception level of the radio wave (FM radio broadcast wave) received by the antenna 10 and outputs it to the AGC drive unit 133B. The sensitivity of the AGC detection unit 132B is set by the FMAGC sensitivity setting command input from the bus data line 170 and can be changed by the FMAGC sensitivity setting command. Also, the on / off sensitivity of the AGC is also set by the FMAGC sensitivity setting command.

[0032] <AGC drive unit 133A> When the output of the AGC detection unit 132A becomes equal to or higher than the threshold value, the AGC drive unit 133A operates to turn on the AGC, outputs a drive signal for changing the time constant of the RF amplifier 120A to the response setting unit 125A, and outputs a damping drive signal generated based on the output of the AGC detection unit 132A to the damping circuit 142A. The AGC drive unit 133A has a function as an output buffer of the AGC detection unit 132A. Since the output of the AGC detection unit 132A is a small signal and the output impedance is high, the AGC drive unit 133A functions as an output buffer, converts the impedance, and drives (turns on) the AGC with a low impedance.

[0033] Also, the AGC drive unit 133A has a hysteresis characteristic with respect to the output of the AGC detection unit 132A, and the threshold value for the output of the AGC detection unit 132A when turning off the AGC is lower than the threshold value for the output of the AGC detection unit 132A when turning on the AGC. This is to enable stable switching of the on / off state of the AGC.

[0034] <AGC drive unit 133B> When the output of the AGC detection unit 132B becomes equal to or higher than the threshold value, the AGC drive unit 133B operates to turn on the AGC, outputs a drive signal for changing the time constant of the RF amplifier 120B to the response setting unit 125B, and outputs a damping drive signal generated based on the output of the AGC detection unit 132B to the damping circuit 142B. The AGC drive unit 133B has a function as an output buffer of the AGC detection unit 132B. Since the output of the AGC detection unit 132B is a small signal and the output impedance is high, the AGC drive unit 133B functions as an output buffer, converts the impedance, and drives (turns on) the AGC with a low impedance.

[0035] Also, the AGC drive unit 133B has a hysteresis characteristic with respect to the output of the AGC detection unit 132B, and the threshold value for the output of the AGC detection unit 132B when turning off the AGC is lower than the threshold value for the output of the AGC detection unit 132B when turning on the AGC. This is to enable stable switching of the on / off state of the AGC.

[0036] <fet141a> The FET 141A is provided to perform damping of the circuit for AM radio broadcast waves. The FET 141A is, for example, an N-channel FET, and has a drain connected to the input terminal 101 via a capacitor C1 and a coil L4, a source connected to ground, and a gate connected to the damping circuit 142A.

[0037] <fet141b> FET 141B is provided to perform damping of the circuit for FM radio broadcast waves. FET 141B is, for example, an N-channel FET, with its drain connected to input terminal 101 via capacitor C2, its source connected to ground, and its gate connected to damping circuit 142B.

[0038] <Damping circuit 142A> The damping circuit 142A outputs a gate control signal of L (Low) level to the gate of the FET 141A to perform damping based on the damping drive signal generated by the AGC drive unit 133A based on the output of the AGC detection unit 132A. The damping circuit 142A also supplies current to the drain of the FET 141A through a constant current source.

[0039] <Damping circuit 142B> The damping circuit 142B outputs a gate control signal of L (Low) level to the gate of the FET 141B to perform damping based on the damping drive signal generated by the AGC drive unit 133B based on the output of the AGC detection unit 132B. The damping circuit 142B also supplies a current to the drain of the FET 141B through a constant current source.

[0040] <Keyed AGC circuit 150A> The keyed AGC circuit 150A performs a keyed AGC function of lowering the gain of the AGC amplifier 131A when the signal level of the AM radio broadcast wave selected by the tuning circuit 110A is low, and increasing the gain of the AGC amplifier 131A when the signal level of the AM radio broadcast wave selected by the tuning circuit 110A is high.

[0041] <Keyed AGC circuit 150B> The keyed AGC circuit 150B performs a keyed AGC function of lowering the gain of the AGC amplifier 131B when the signal level of the FM radio broadcast wave selected by the tuning circuit 110B is low, and increasing the gain of the AGC amplifier 131B when the signal level of the FM radio broadcast wave selected by the tuning circuit 110B is high.

[0042] <Switching unit 160A> When receiving AM radio broadcast waves, the switching unit 160A switches the tuning frequency of the tuning circuit for AM radio broadcast waves so as to be compatible with frequencies from LF (Low Frequency) to HF (High Frequency). Specifically, the switching unit 160A switches to tune to the capacitor C1, coil L1, and coil L2 when the frequency is from LF to MF (Middle Frequency), and to the capacitor C1 and coil L1 when the frequency is HF.

[0043] The switching unit 160A includes an FET 161A and a switching control unit 162A. The FET 161A is, for example, an N-channel type, and its drain is connected to the switching control unit 162A via a current source and to the connection point between the coils L1 and L2. The source of the FET 161A is connected to ground, and its gate is connected to the switching control unit 162A.

[0044] The input terminal of the switching control unit 162A is connected to the bus data line 170, and based on the data input from the bus data line 170, switches the conductive state of the FET 161A in accordance with the AM radio broadcast wave of the selected broadcast station.

[0045] <Bus data line 170> The bus data line 170 is connected to the control unit of the receiving circuit 20 and transmits RSSI data indicating the RSSI of the radio waves received by the antenna 10, data indicating the frequency, a switching signal indicating switching between AM and FM, etc. The bus data line 170 outputs time constant setting data to the response setting unit 125A and outputs time constant setting data to the response setting unit 125B. The bus data line 170 also outputs RSSI data of the AM radio broadcast waves to the keyed AGC circuit 150A and outputs RSSI data of the FM radio broadcast waves to the keyed AGC circuit 150B. The bus data line 170 also outputs a switching signal input from the control unit to the output switching unit 102.

[0046] <Flowchart> 2 is a flowchart showing an example of processing executed by the receiving device 100. Here, a circuit for FM radio broadcast waves will be used as an example for explanation, but the same applies to a circuit for AM radio broadcast waves. The predetermined threshold TH0, first threshold TH1, second threshold TH2, and third threshold TH3 used in the following explanation take the following values, for example: Assuming that the specified value of RSSI is 55 dBμV to 60 dBμV, the predetermined threshold TH0 is 60 dBμV at the reception level of the AGC detection unit 132B, and the first threshold TH1 is a value greater than 60 dBμV and equal to or less than 70 dBμV at the reception level of the AGC detection unit 132B. The second threshold TH2 is a value equal to or less than 20 dBμV at the RSSI, and the third threshold TH3 is a value equal to or greater than 80 dBμV at the reception level of the AGC detection unit 132B.

[0047] The AGC detector 132B of the receiving device 100 acquires the reception level of the radio waves (FM radio broadcast waves) received by the antenna 10 based on the output of the AGC amplifier 131B (step S1).

[0048] The AGC driver 133B determines whether the reception level is equal to or greater than a predetermined threshold value TH0 (step S2).

[0049] If the AGC driving unit 133B determines that the reception level is equal to or greater than the predetermined threshold TH0 (S2: YES), it checks the reception level and outputs it to the damping circuit 142B (step S3). Note that if the AGC driving unit 133B determines in step S2 that the reception level is not equal to or greater than the predetermined threshold TH0 (S2: NO), it returns the flow to step S1.

[0050] The damping circuit 142B determines whether the reception level input from the AGC driver 133B is equal to or greater than the first threshold value TH1 (step S4). If the damping circuit 142B determines that the reception level is not equal to or greater than the first threshold value TH1 (S4: NO), the flow returns to step S1.

[0051] If the damping circuit 142B determines in step S4 that the reception level is equal to or greater than the first threshold TH1 (S4: YES), it turns on the FET 141B to perform damping (step S5) in order to reduce intermodulation interference and cross modulation interference caused by a strong electric field.

[0052] The receiving device 100 determines whether the reception level of the radio waves (FM radio broadcast waves) acquired by the AGC detection unit 132B is equal to or greater than a third threshold TH3 (step S6). The third threshold TH3 is greater than the first threshold TH1 and is used to determine whether an extremely strong electric field has been detected after damping.

[0053] If the receiving device 100 determines that the reception level is equal to or greater than the third threshold TH3 (S6: YES), it reduces the gain of the RF amplifier 120B to a predetermined gain (step S7). This is because reducing the gain of the RF amplifier 120B reduces intermodulation interference and cross modulation interference caused by extremely strong electric fields. If the receiving device 100 determines in step S7 that the reception level is not equal to or greater than the third threshold TH3 (S6: NO), it returns the flow to step S1.

[0054] The keyed AGC circuit 150B checks the RSSI data of the radio wave (FM radio broadcast wave) input from the bus data line 170 (step S8).

[0055] The keyed AGC circuit 150B determines whether the RSSI indicated by the RSSI data is equal to or greater than the second threshold value TH2 (step S9).

[0056] When the keyed AGC circuit 150B determines that the RSSI is smaller than the second threshold TH2 (S9: NO), it executes the keyed AGC function and reduces the gain of the AGC amplifier 131B (step S9A). This minimizes degradation of reception sensitivity due to sensitivity suppression (blocking by the AGC amplifier 131B), which makes it impossible to receive radio waves from broadcast stations with medium to weak electric fields, and also makes it possible to strike a balance with sensitivity suppression even when intermodulation interference is occurring.

[0057] The keyed AGC circuit 150B increases the gain of the RF amplifier 120B (step S9B).

[0058] Damping circuit 142B turns off FET 141B to turn off damping (step S9C). After completing the process of step S9C, receiving device 100 returns the flow to step S8.

[0059] When the receiving device 100 determines that the RSSI is equal to or greater than the second threshold TH2 (S9: YES), the receiving device 100 increases the gain of the AGC amplifier 131B (step S10).

[0060] The receiving device 100 determines whether the RSSI indicated by the RSSI data is close to a specified value (step S11). If the receiving device 100 determines that the RSSI is not close to the specified value (S11: NO), the flow proceeds to step S9B.

[0061] If the receiving device 100 determines in step S11 that the RSSI is close to the specified value (S11: YES), it sets the gain of the AGC amplifier 131B to a value that is used when the RSSI is close to the specified value (step S12). By the processes of steps S8 to S12, the gain of the AGC amplifier 131B is changed stepwise to set the gain that maximizes the RSSI.

[0062] The AGC detection unit 132B acquires the reception level of the radio waves (FM radio broadcast waves) received by the antenna 10 based on the output of the AGC amplifier 131B (step S13). The AGC detection unit 132B outputs the acquired reception level to the damping circuit 142B.

[0063] The damping circuit 142B determines whether the reception level is lower than the first threshold value TH1 (step S14). If the damping circuit 142B determines that the reception level is not lower than the first threshold value TH1 (S14: NO), the flow returns to step S13.

[0064] If the damping circuit 142B determines in step S14 that the reception level is lower than the first threshold value TH1 (S14: YES), it sets the FET 141B to a non-conductive state to stop damping (step S15).

[0065] The receiving device 100 determines whether the RSSI indicated by the RSSI data is equal to or greater than the second threshold TH2 (step S16). If the receiving device 100 determines that the RSSI is not equal to or greater than the second threshold TH2 (S16: NO), the flow returns to step S13.

[0066] When receiving device 100 determines in step S16 that RSSI is equal to or greater than second threshold TH2 (S16: YES), it increases the gain of AGC amplifier 131B (step S17). This is because the reception level is high, and the gain of AGC amplifier 131B is increased to reduce the strength of the radio waves input to tuning circuit 110B. Through the processing of steps S13 to S17, the gain of AGC amplifier 131B is changed in stages to set the gain that maximizes RSSI.

[0067] After completing the process of step S17, the receiving device 100 returns the flow to step S1. The receiving device 100 repeatedly executes the above series of processes.

[0068] <Effects> The receiving device 100 includes tuning circuits 110A, 110B connected to an antenna 10 mounted on a mobile object and capable of receiving radio broadcast waves in multiple frequency bands, RF amplifiers 120A, 120B connected to the output sides of the tuning circuits 110A, 110B, FETs 141A, 141B provided between the antenna 10 and a reference potential point, damping circuits 142A, 142B that cause the FETs 141A, 141B to conduct when the electric field of the radio waves received by the antenna 10 is equal to or higher than a first threshold, AGC amplifiers 131A, 131B connected to the antenna 10, and keyed AGC circuits 150A, 150B connected to the AGC amplifiers 131A, 131B, and the keyed AGC circuits 150A, 150B reduce the gain of the AGC amplifiers 131A, 131B when the electric field of the radio waves received by the antenna 10 becomes smaller than a second threshold.

[0069] Therefore, it is possible to provide the receiving device 100 that can obtain sufficient reception strength of the radio wave of the target frequency even when desensitization occurs.

[0070] Furthermore, the antenna 10 may further include a response setting unit 125A or 125B that reduces the gain of the RF amplifier 120A or 120B when the electric field of the radio waves received by the antenna 10 is equal to or higher than a third threshold value while the damping circuit 142A or 142B is causing the FET 141A or 141B to conduct. In the case of a strong electric field where the reception level (electric field of the radio waves) is high even with damping, the reception level of the radio broadcast waves of the selected channel can be set to an appropriate level by reducing the gain of the RF amplifier 120A or 120B.

[0071] Furthermore, when the electric field of the radio waves received by the antenna 10 becomes smaller than the first threshold while the FET 141A or 141B is conductive, the damping circuit 142A or 142B may switch the FET 141A or 141B to a non-conductive state. When damping is no longer necessary, the damping can be switched off, thereby setting the reception level of the radio broadcast waves of the selected channel to an appropriate level.

[0072] Furthermore, the receiving circuit 20 is connected to the output side of the RF amplifier 120A or 120B, and the keyed AGC circuit 150A or 150B may acquire RSSI, which indicates the field strength of the radio waves received by the antenna 10, from the receiving circuit 20, and may lower the gain of the AGC amplifier 131A or 131B when the field strength indicated by the acquired RSSI becomes equal to or greater than a second threshold. A configuration can be realized in which the keyed AGC circuit 150A or 150B can lower the gain of the AGC amplifier 131A or 131B based on the RSSI data acquired from the receiving circuit 20.

[0073] Furthermore, the tuning circuit 110A or 110B may be configured as an integrated circuit. The tuning circuit 110A or 110B can be controlled based on a digital signal.

[0074] The above describes a receiving device according to an exemplary embodiment of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims. [Explanation of symbols]

[0075] 10 Antennas 20 Receiving circuit 100 receiving device 101 Input terminal 102 Output switching unit 103 Output terminal 110A, 110B tuning circuit 120A, 120B RF Amplifiers 125A, 125B Response setting section 131A, 131B AGC amplifier 132A, 132B AGC detector 133A, 133B AGC drive unit 141A, 141B FETs 142A, 142B damping circuit 150A, 150B Keyed AGC circuit 160A switching unit 161A FET 162A Switching control unit 170 bus data lines

Claims

1. a tuning circuit connected to an antenna mounted on the mobile object and capable of receiving radio broadcast waves in a plurality of frequency bands; an amplifier circuit connected to the output side of the tuning circuit; a switch element provided between the antenna and a reference potential point; a first control unit that turns on the switch element when the electric field of the radio wave received by the antenna is equal to or greater than a first threshold; an AGC amplifier connected to the antenna; a keyed AGC circuit connected to the AGC amplifier; Including, The keyed AGC circuit reduces the gain of the AGC amplifier when the electric field of the radio wave received by the antenna becomes smaller than a second threshold.

2. 2. The receiving device according to claim 1, further comprising a second control unit that reduces a gain of the amplifier circuit when the electric field of the radio wave received by the antenna is equal to or greater than a third threshold value while the first control unit is turning on the switch element.

3. 2. The receiving device according to claim 1, wherein the first control unit switches the switch element to a non-conductive state when the electric field of the radio waves received by the antenna becomes smaller than the first threshold while the switch element is conductive.

4. A receiving circuit is connected to the output side of the amplifier circuit, 4. The receiving device according to claim 1, wherein the keyed AGC circuit acquires an RSSI representing the field strength of the radio waves received by the antenna from the receiving circuit, and reduces the gain of the AGC amplifier when the field strength represented by the acquired RSSI becomes equal to or greater than the second threshold.

5. 2. The receiving device according to claim 1, wherein the tuning circuit is configured as an integrated circuit.

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