JP2008187290A - Radio equipment for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide radio equipment for automobile that can receive and detect a radio wave from an external communication device by automatically avoiding the influence of a disturbing radio wave even when there exists the one in a specified frequency band. <P>SOLUTION: The radio equipment 1 for automobile which selectively receives and detects a first radio wave and a second radio wave differing in frequency includes a peak detecting circuit 27 which detects the intensity of the received first radio wave or second radio wave, a detecting circuit 21 which detects a base band signal from a signal of the received first radio wave or second radio wave, and a switching control unit 28 which switches a radio wave to be received to the second radio wave when receiving the first radio wave and judging that the signal intensity is larger than predetermined intensity and the detection of the base band signal ends in failure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an automobile radio that selectively receives and detects radio waves having different frequencies.

  An automotive radio communication system has been put into practical use in which an automobile radio device mounted on an automobile and a transmitter outside the automobile perform wireless communication to control equipment on the automobile side from the outside of the automobile. For example, a keyless entry system and a tire pressure monitoring system have been put into practical use.

  In the keyless entry system, the transmitter is built in the key, and when the lock / unlock button of the key is pressed, the transmitter transmits information unique to the automobile by radio waves of 315 MHz. When the radio for an automobile receives the radio wave transmitted from the transmitter and succeeds in authentication, the automobile radio locks or unlocks the door of the automobile.

  In the tire pressure monitoring system, a tire pressure detector is provided on each wheel of an automobile, and a transmitter transmits the tire pressure detected by each tire pressure detector using a 310 MHz radio wave. And the radio | wireless machine for motor vehicles mounted in the motor vehicle can monitor the air pressure of a tire by receiving the electromagnetic wave transmitted from the transmitter.

  On the other hand, a radio for an automobile that can receive a radio wave for a keyless entry system and a radio wave for a tire pressure monitoring system having a frequency different from the radio wave and can be used for each system has been proposed (for example, Patent Document 1).

FIG. 9 is a block diagram showing the configuration of the automobile radio device according to Patent Document 1. As shown in FIG. The automobile radio device according to Patent Document 1 includes two antennas 11 and 12 and an antenna changeover switch 13 for receiving radio waves for a keyless entry system and a tire pressure monitoring system, and selectively receives each radio wave. Is configured to do. The received radio wave signal is amplified by the amplifier 15 and converted into an intermediate frequency signal of the same frequency by the frequency mixing circuit 16. Two oscillators 25 a and 25 b having different transmission frequencies are connected to the frequency mixing circuit 16 via a frequency changeover switch 24. The frequency mixing circuit 16 generates an intermediate frequency signal having the same frequency by switching the oscillators 25a and 25b according to the frequency of the radio wave. The intermediate frequency signal passes through the bandpass filter 118 and is detected by the detection circuit 21. The detected baseband signal passes through the low-pass filter 122, is waveform-shaped by the waveform shaping circuit 23, and is output as a demodulated signal.
The antenna switch 13 and the frequency switch 24 can be switched by turning on / off the ignition switch.

The automobile radio device configured as described above can be used for a plurality of systems having different operating frequencies.
JP 2006-21151 A

  However, in the conventional keyless entry system or tire pressure monitoring system, since the frequency of the used radio wave is fixed, if there is an interfering radio wave in the same frequency band as the used radio wave, the automotive radio device There was a problem that it could not be received and communication was impossible.

  In addition, in the radio | wireless machine for motor vehicles based on patent document 1, since it is comprised so that a receiving frequency may be switched by ON / OFF of an ignition switch, the above-mentioned problem cannot be solved.

  The present invention has been made in view of such circumstances, and by determining the presence or absence of interfering radio waves and, when there are interfering radio waves, the configuration is such that the frequency of the received radio waves is switched, It is an object of the present invention to provide an automobile radio device that can automatically avoid the influence of jamming radio waves and receive and detect radio waves from an external transmitter even in some cases.

  Another object of the present invention is to convert each radio wave signal having a different frequency into an intermediate frequency signal having a different frequency and selectively receive the signal, thereby having the same frequency band as the received radio wave and the intermediate frequency signal. An object of the present invention is to provide an automotive radio that can receive and detect radio waves even when there are jamming radio waves.

  According to a first aspect of the present invention, there is provided an automotive radio device including a baseband signal, wherein the first radio wave or the second radio wave having different frequencies is selectively received and detected. Detecting means for detecting the intensity of the signal of the second radio wave; signal intensity determining means for determining whether or not the intensity detected by the detecting means is equal to or greater than a predetermined intensity; and the received first radio wave or second radio wave A detection circuit for detecting a baseband signal from the received signal, a success / failure determination means for determining success / failure of detection by the detection circuit, a first radio wave (or second radio wave), and the signal intensity determination means When it determines with it being more than intensity | strength and the said success / failure determination means determines with no, it is provided with the switching means which switches the radio wave to receive to a 2nd radio wave (or 1st radio wave), It is characterized by the above-mentioned.

In the first invention, the first radio wave or the second radio wave can be selectively received, and the presence / absence of an interfering radio wave in the frequency band of the first radio wave and the second radio wave can be determined.
Specifically, the signal strength determination unit determines whether or not the strength of the signal of the first radio wave or the second radio wave detected by the detection circuit is equal to or higher than a predetermined strength. On the other hand, the success / failure determination means determines whether the detection of the baseband signal by the detection circuit is successful. If the signal strength determination means determines that the signal strength is equal to or higher than the predetermined strength and the success / failure determination means determines NO, it is considered that the received radio wave includes an interfering radio wave.
Therefore, the switching means switches the received radio wave from the first radio wave to the second radio wave when the first radio wave is received and it is determined that there is an interfering radio wave as described above. Similarly, when the second radio wave is received and it is determined that there is an interfering radio wave, the received radio wave is switched from the second radio wave to the first radio wave.
Therefore, it is possible to select the first radio wave or the second radio wave that can avoid the influence of the jamming radio wave, and acquire the baseband signal with the selected radio wave.
The first invention does not exclude the case where three or more radio waves having different frequencies are received, and may be a configuration that receives at least two radio waves having different frequencies.

  According to a second aspect of the present invention, there is provided an automotive radio device comprising a first antenna for receiving a first radio wave and a second antenna for receiving a second radio wave, wherein the switching means receives a signal of the first radio wave or the second radio wave. An antenna changeover switch for selectively connecting the detection circuit to be input to the detection circuit is provided.

In the second invention, the switching means includes an antenna switch. The antenna selector switch selectively connects the first antenna that receives the first radio wave or the second antenna that receives the second radio wave to the detection circuit.
When it is determined that the first radio wave is received and there is an interfering radio wave, the antenna changeover switch connects the second antenna and the detection circuit, and detects the baseband signal from the second radio wave signal.
When it is determined that the second radio wave is received and there is an interfering radio wave, the antenna changeover switch connects the first antenna and the detection circuit, and detects the baseband signal from the first radio wave signal.

  According to a third aspect of the present invention, there is provided an automotive radio device that converts a received first radio wave signal into a first low frequency band signal and a second radio wave signal into a second low frequency band signal, A first filter that transmits a signal in the first low frequency band, a second filter that transmits a signal in the second low frequency band, and a frequency-converted signal are input to the first filter or the second filter. A filter changeover switch for selectively connecting the conversion circuit, and the detection circuit detects a baseband signal from a signal transmitted through the first filter or the second filter. Features.

In the third invention, the switching means includes a filter switch. The filter changeover switch selectively connects the first filter or the second filter to a conversion circuit that converts a radio wave signal into a lower frequency signal, a so-called intermediate frequency signal.
When it is determined that the first radio wave is received and there is an interfering radio wave, the switching means switches the received radio wave from the first radio wave to the second radio wave, and the filter changeover switch connects the second filter to the conversion circuit. Therefore, in this case, the second radio wave is converted into a signal of the second low frequency band, transmitted through the second filter, and then detected by the detection circuit.
Similarly, when the second radio wave is received and it is determined that there is an interfering radio wave, the switching means switches the received radio wave from the second radio wave to the first radio wave, and the filter changeover switch connects the first filter to the conversion circuit. Connecting. Therefore, in this case, the first radio wave is converted into a signal of the first low frequency band, passes through the first filter, and then detected by the detection circuit.
Accordingly, it is possible to switch the receivable frequency and also switch the frequency band of the intermediate frequency signal. Moreover, unnecessary noise can be reliably removed by switching to the first filter or the second filter suitable for the frequency band of the intermediate frequency signal. Therefore, it is possible to receive the signal of the first radio wave or the second radio wave more reliably avoiding the influence of the jamming radio wave.

  According to the first and second inventions, when the jamming radio wave is detected, it is possible to automatically avoid the influence of the jamming radio wave and to receive and detect the radio wave from the external transmission device by changing the reception frequency. .

  According to the third invention, not only when there is a jamming radio wave in the same frequency band as the received radio wave, but also when there is a jamming radio wave in the same frequency band as the intermediate frequency signal, avoid the influence of the jamming radio wave, Radio waves from an external communication device can be received and detected.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram showing a configuration of an automotive radio 1 according to an embodiment of the present invention. The superheterodyne automotive radio device 1 according to the embodiment of the present invention is configured to be able to receive and detect radio waves and intermediate frequency signals of different frequencies.

The vehicle radio device 1 includes a first antenna 11, a second antenna 12, and an antenna changeover switch 13 for selectively receiving first or second radio waves having different frequencies.
For example, the first antenna 11 is configured to receive a 315 MHz radio wave transmitted from the portable wireless device 3, and the second antenna 12 is configured to receive a 310 MHz radio wave (see FIG. 3).
The antenna changeover switch 13 includes a first antenna side changeover end 13a connected to the output end of the first antenna 11, a second antenna side changeover end 13b connected to the output end of the second antenna 12, and a common end 13c. Yes. The input end of the band pass filter 14 is connected to the common end 13c. The antenna changeover switch 13 is a monostable type, and is stable when the first antenna side changeover end 13a and the common end 13c are connected.

  The bandpass filter 14 is a filter that transmits signals in the frequency bands of the first radio wave and the second radio wave, and the input terminal of the amplifier 15 is connected to the output terminal of the bandpass filter 14.

  The amplifier 15 is a circuit that amplifies an input signal, and one input terminal of the frequency mixing circuit 16 is connected to the output terminal of the amplifier 15.

  An oscillator 25 and a frequency conversion circuit 26 are connected to the frequency mixing circuit 16 via a frequency changeover switch 24, and either the oscillator 25 or the frequency conversion circuit 26 is selectively connected. .

  The frequency changeover switch 24 includes a common end 24 c connected to the other input end of the frequency mixing circuit 16, an oscillator side changeover end 24 a connected to the oscillator 25, and a frequency conversion connected to the output end of the frequency conversion circuit 26. And a circuit-side switching end 24b. The frequency changeover switch 24 is a monostable type, and is stable when the oscillator side changeover end 24a and the common end 24c are connected.

  The oscillator 25 is a circuit that transmits a signal of 304.3 MHz, for example, and outputs the signal to the frequency changeover switch 24 and the frequency conversion circuit 26.

  The frequency conversion circuit 26 converts the frequency of the signal output from the oscillator 25 to 31/32 times, and outputs a signal having a frequency of 294.8 = 304.3 × 31/32 Hz to the frequency changeover switch 24. The frequency conversion circuit 26 includes a multiplier circuit, a frequency divider circuit, and the like.

The frequency mixing circuit 16 mixes the signal of the first radio wave or the second radio wave input to the input terminal with the signal from the oscillator 25 or the frequency conversion circuit 26, thereby making each signal an intermediate frequency signal having a different frequency band. And the converted intermediate frequency signal is output from the output end.
Specifically, when the common end 24c and the oscillator side switching end 24a are connected by the frequency changeover switch 24, the frequency mixing circuit 16 receives the 304.3 MHz signal from the oscillator 25 and the 315 MHz signal of the first radio wave. And an intermediate frequency signal of 315-304.3 = 10.7 MHz is output.
Similarly, when the common end 24c and the frequency conversion circuit side switching end 24b are connected, the frequency mixing circuit 16 mixes the 294.8 MHz signal from the frequency conversion circuit 26 with the 310 MHz signal of the second radio wave. Then, an intermediate frequency signal of 310 MHz-294.8 MHz = 15.2 MHz is output.

  A first band-pass filter 18 and a second band-pass filter 19 are connected to the output end of the frequency mixing circuit 16 via a filter changeover switch 17, and the first band-pass filter 18 or the second band-pass filter 19 is connected. Either one is configured to be selectively connected.

  The filter changeover switch 17 includes a common end 17 c connected to the output end of the frequency mixing circuit 16, a first filter side changeover end 17 a connected to the input end of the first bandpass filter 18, and a second filter side changeover end. 17b end. The filter changeover switch 17 is a monostable type and is stable when the first filter side changeover end 17a and the common end 17c are connected.

  The first bandpass filter 18 is a filter that transmits a signal in a first low frequency band, for example, 10.7 MHz band, and the second bandpass filter 19 is a signal that transmits a signal in a second low frequency band, for example, 15.2 MHz. It is a filter to be made.

  A detection circuit 21 is connected to the first bandpass filter 18 and the second bandpass filter 19 via a filter changeover switch 20, and the first bandpass filter 18 and the second bandpass filter 19 are connected to the detection circuit 21. Either one is configured to be selectively connected.

  The filter changeover switch 20 includes a first filter side switching end 20a connected to the output end of the first bandpass filter 18, a second filter side switching end 20b end connected to the output end of the second bandpass filter 19, and A common end 20 c connected to the input ends of the detection circuit 21 and the peak detection circuit 27 is provided. The filter changeover switch 20 is a monostable type and is stable when the first filter side changeover end 20a and the common end 20c are connected.

  The peak detection circuit 27 includes a diode, a capacitor, a voltage follower circuit, and the like for holding the voltage of the intermediate frequency signal transmitted through the first band pass filter 18 or the second band pass filter 19. Detect peak value. Then, the peak detection circuit 27 gives an RSSI (Received Signal Strength Indicator) signal corresponding to the magnitude of the detected peak value, that is, a received signal strength display signal to the switching control unit 28.

  The detection circuit 21 is a circuit that detects a baseband signal from the intermediate frequency signal, and outputs the detected baseband signal to the low-pass filter 22 connected to the output terminal of the detection circuit 21.

  The low-pass filter 22 removes a frequency component equal to or higher than a predetermined cutoff frequency from the baseband signal output from the detection circuit 21 and outputs the baseband signal from which the frequency component has been removed to the waveform shaping circuit 23.

  The waveform shaping circuit 23 shapes the baseband signal into, for example, a rectangular wave, and outputs the waveform-shaped signal to the outside and the switching control unit 28 as a demodulated signal. The information processing circuit in the subsequent stage, for example, the control circuit 4 (see FIG. 3), determines whether the demodulated signal is high level or low level, the bit “1” and the bit “0” depending on the interval between edges. It is converted into digital data and various information processing is performed.

The switching control unit 28 is configured by a microcomputer, for example.
FIG. 2 is a block diagram illustrating a configuration of the switching control unit 28. The switching control unit 28 includes a CPU 27a. The CPU 27a includes a ROM 27b, a RAM 27c, a timing unit 27d, a first input / output unit 27e, a second input / output unit 27g, and an output unit 27f via a bus 27h. Yes. The switching control unit 28 is configured to determine the presence or absence of jamming radio waves by developing and executing a computer program stored in the ROM 27b in the RAM 27c, and to control switching of each switch according to the determination result. ing. A peak detection circuit 27 is connected to the first input / output unit 27e, and a waveform shaping circuit 23 is connected to the second input / output unit 27g. Further, the antenna changeover switch 13, the frequency changeover switch 24, and the filter changeover switches 17 and 20 are connected to the output unit 27f.

FIG. 3 is a block diagram showing an automobile radio communication system including the automobile radio device 1 and the portable radio device 3.
The automobile radio communication system includes an automobile radio 1, a portable radio 3, and a control circuit 4.

  The control circuit 4 is, for example, a microcomputer including a CPU, and a ROM, a RAM, a timer, an input / output unit, and the like are connected to the CPU. Connected to the input / output unit are in-vehicle devices such as the automobile radio 1 and the door locking / unlocking motor 5.

  The control circuit 4 controls the operation of the door locking / unlocking motor 5 by developing and executing a computer program stored in the ROM on the RAM. Specifically, the control circuit 4 drives the door locking / unlocking motor 5 to lock or lock the door of the automobile when the demodulated signal output from the automobile radio 1 includes information specific to the automobile. Unlock.

  The portable wireless device 3 is built in, for example, a car key, and the key is provided with a push-button type first door locking / unlocking button and a second door locking / unlocking button. Yes. When the first door locking / unlocking button is pressed, the portable wireless device 3 transmits information specific to the vehicle using radio waves of 315 MHz, and when the second door locking / unlocking button is pressed, The unique information is transmitted by 310 MHz radio waves.

  4 and 5 are flowcharts showing the processing procedure of the switching control unit 28 related to switch switching, and FIG. 6 is a block diagram showing the configuration of the automobile radio device 1 in which each switch is switched. The switching control unit 28 receives the RSSI signal (step S11), and determines whether or not the signal level of the RSSI signal is equal to or higher than a predetermined signal level (step S12).

  When it determines with it not being beyond a predetermined signal level (step S12: NO), the switching control part 28 returns a process to step S11. When it is determined that the signal level is equal to or higher than the predetermined signal level (step S12: YES), the switching control unit 28 receives the signal from the waveform shaping circuit 23 (step S13) and succeeds in the detection, that is, the reception of the baseband signal. It is determined whether or not (step S14).

  If it is determined that the baseband signal has been successfully received (step S14: YES), the switching control unit 28 ends the process. When it is determined that the reception of the baseband signal has failed (step S14: NO), the switching control unit 28 outputs the switching signal to the antenna switching switch 13 so that the antenna switching switch 13 is turned on as shown in FIG. The second antenna side switching end 13b is switched (step S15).

  Next, the switching control unit 28 outputs the switching signal to the frequency switching switch 24, thereby switching the frequency switching switch 24 to the frequency conversion circuit 26 side as shown in FIG. 6 (step S16).

  Next, the switching control unit 28 outputs a switching signal to the filter switching switches 17 and 20, thereby switching the filter switching switches 17 and 20 to the second filter side switching ends 17b and 20b, respectively, as shown in FIG. (Step S17).

  When the process of step S17 is completed, the switching control unit 28 receives the RSSI signal (step S18), and determines whether or not the signal level of the RSSI signal is equal to or higher than a predetermined signal level (step S19).

  When it determines with it not being more than a predetermined signal level (step S19: NO), the switching control part 28 returns a process to step S18. When it is determined that the signal level is equal to or higher than the predetermined signal level (step S19: YES), the switching control unit 28 receives a signal from the waveform shaping circuit 23 (step S20) and determines whether or not the baseband signal has been successfully received. Determination is made (step S21).

  If it is determined that the baseband signal has been successfully received (step S21: YES), the switching control unit 28 ends the process. When it is determined that the reception of the baseband signal has failed (step S21: NO), the switching control unit 28 outputs the switching signal to the antenna switching switch 13 so that the antenna switching switch 13 is turned on as shown in FIG. Switch to the first antenna side switching end 13a (step S22).

  Next, the switching control unit 28 outputs a switching signal to the frequency switching switch 24, thereby switching the frequency switching switch 24 to the oscillator 25 side as shown in FIG. 1 (step S23).

Next, the switching control unit 28 outputs a switching signal to the filter switching switches 17 and 20, thereby switching the filter switching switches 17 and 20 to the first filter side switching ends 17a and 20a, respectively, as shown in FIG. (Step S24), the process returns to Step S11.
The above-described processing is executed every time ΔT. ΔT is, for example, 1 to 11 seconds.

  Hereinafter, operations and effects of the vehicle radio device 1 and the portable radio device 3 according to the embodiment will be described.

FIG. 7 is a timing chart showing received signals, RSSI signals, and the like. In FIG. 7, the horizontal axis represents time, and FIG. 7A shows the timing at which the above-described processing is executed and the reception state is monitored, and the frequency of the radio wave received at the timing. A white bar indicates that a first radio wave having a frequency f1 = 315 MHz is received, and a hatched bar indicates that a second radio wave having a frequency f2 = 310 MHz is received.
FIG. 7B is a timing chart showing the signal level of the RSSI signal. The vertical axis represents the signal level of the RSSI signal.
FIG. 7C is a timing chart showing success or failure of reception of the baseband signal. A white bar indicates a state in which the baseband signal is successfully received.

  At time 0, ΔT, and 2ΔT, neither the radio wave transmitted from the portable wireless device 3 nor the jamming radio wave is present, and the signal level of the RSSI signal is less than the predetermined signal level. Executed. In this case, the antenna selector switch 13, the frequency selector switch 24, and the filter selector switches 17 and 20 are in the state shown in FIG.

  At time 3ΔT, since the signal level of the RSSI signal is equal to or higher than the predetermined signal level and the information related to the baseband signal can be acquired, the switches are not switched. Therefore, the vehicle radio device 1 can receive the signal of the first radio wave of 315 MHz, convert it to an intermediate frequency signal of 10.7 MHz and detect it, and acquire information related to the detected baseband signal. Can do.

  However, at time 4ΔT, although the signal level of the RSSI signal is equal to or higher than the predetermined signal level, information on the baseband signal cannot be acquired. That is, the information transmitted from the portable wireless device 3 cannot be acquired due to the jamming radio wave.

  FIG. 8 is a schematic diagram showing the intensity spectrum of radio waves in the vicinity of the radio tower. In the vicinity of such a radio tower, as shown by hatching in FIG. 8, there are jamming radio waves in the 315 MHz band and the 0 to 11 MHz band, and the radio wave from the portable wireless device 3 cannot be received and detected. That is, the 315 MHz interfering radio wave interferes with the reception of the first radio wave, and the 0-11 MHz interfering radio wave interferes with the detection and demodulation of the baseband signal from the intermediate frequency signal.

However, since the portable radio device 3 and the vehicle radio device 1 according to the embodiment can transmit and receive 310 MHz radio waves and convert the second radio wave signals into 15.2 MHz intermediate frequency signals, The influence can be avoided.
Specifically, when it is determined that there is an interfering radio wave in the frequency band of the first radio wave by the process of step S11 to step S14, the vehicle radio device 1 performs the antenna changeover switch 13 by the process of step S15 to step S17. The frequency switch 24 and the filter switches 17 and 20 can be switched as shown in FIG.
On the other hand, when the second locking / unlocking button is pressed, the portable wireless device 3 can transmit information unique to the automobile using 310 MHz radio waves.
Therefore, the vehicle radio device 1 is in a state where it can receive the second radio wave of 310 MHz, convert it to an intermediate frequency signal of 15.2 MHz and detect it, and avoid the influence of the jamming radio wave. Information from the portable wireless device 3 can be acquired.

Similarly, at time 6ΔT, when it is determined that there is an interfering radio wave in the frequency band of the second radio wave by the process of step S18 to step S21, the vehicle radio device 1 performs the antenna changeover switch by the process of step S22 to step S24. 13, the frequency changeover switch 24 and the filter changeover switches 17 and 20 are switched as shown in FIG.
By this processing, at time 7ΔT, the vehicle radio 1 is in a state where it can receive the first radio wave of 315 MHz, convert it to an intermediate frequency signal of 10.7 MHz, and detect the interference radio wave. The information from the portable wireless device 3 can be acquired.

  In the automobile radio device 1 according to the embodiment configured as described above, even when there is a jamming radio wave in the same frequency band as the received radio wave and the intermediate frequency signal, by detecting the jamming radio wave, The frequency of the received radio wave and the intermediate frequency signal can be automatically switched, and the radio wave can be received and detected.

  In addition, selective reception of the first radio wave and the second radio wave and switching of the frequency band of the intermediate frequency signal can be easily realized by the antenna switch 13, the frequency switch 24, and the filter switches 17 and 20. .

  Furthermore, not only when there are jamming radio waves in the same frequency band as the received radio wave, but also when there are jamming radio waves in the same frequency band as the intermediate frequency signal, by switching both the frequency of the received radio wave and the intermediate frequency signal, By avoiding the influence of jamming radio waves, radio waves from the portable wireless device 3 can be received and detected.

  Furthermore, unnecessary noise can be reliably removed by switching to the first band-pass filter 18 or the second band-pass filter 19 suitable for the frequency band of the intermediate frequency signal. Therefore, it is possible to receive the signal of the first radio wave or the second radio wave more reliably avoiding the influence of the jamming radio wave.

  In addition, although embodiment which applied this invention to the keyless entry system was shown, you may apply this invention to another radio | wireless communications system for motor vehicles, for example, a tire pressure monitoring system, a smart key, etc.

  Further, the first radio wave and the second radio wave having different frequencies are received, but it may be configured to selectively receive three or more radio waves having different frequencies.

  Further, the first and second band pass filters are configured to pass through to remove noise from the intermediate frequency signal. However, if noise can be removed, a low pass filter is provided. Also good.

It is a block diagram which shows the structure of the radio | wireless machine for motor vehicles based on embodiment of this invention. It is a block diagram which shows the structure of a switching control part. It is a block diagram which shows the radio | wireless communications system for motor vehicles comprised with the radio | wireless machine for cars, and the portable radio | wireless machine. It is a flowchart which shows the process sequence of the switching control part which concerns on switch switching. It is a flowchart which shows the process sequence of the switching control part which concerns on switch switching. It is a block diagram which shows the structure of the radio | wireless machine for motor vehicles in which each changeover switch was switched. It is a timing chart which shows a received signal, an RSSI signal, etc. It is a schematic diagram which shows the intensity spectrum of the electromagnetic wave in the vicinity of the radio tower. It is a block diagram which shows the structure of the radio | wireless machine for motor vehicles based on patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Car radio device 3 Portable radio device 4 Control circuit 5 Door locking / unlocking motor 11 First antenna 12 Second antenna 13 Antenna changeover switch 14 Band pass filter 15 Amplifier 16 Frequency mixing circuit 17 Filter changeover switch 18 First band pass Filter 19 Second band pass filter 20 Filter change-over switch 21 Detection circuit 22 Low-pass filter 23 Waveform shaping circuit 24 Frequency change-over switch 25 Oscillator 26 Frequency conversion circuit 27 Peak detection circuit 28 Switching control unit

Claims (3)

In an automobile radio that includes a baseband signal and selectively receives and detects first and second radio waves having different frequencies,
Detecting means for detecting the intensity of the received first radio wave or second radio wave signal;
Signal intensity determination means for determining whether or not the intensity detected by the detection means is equal to or greater than a predetermined intensity;
A detection circuit for detecting a baseband signal from the received first radio wave signal or second radio wave signal;
Success / failure determination means for determining success / failure of detection by the detection circuit;
When the first radio wave (or the second radio wave) is received and the signal strength determination unit determines that the signal strength is greater than or equal to a predetermined strength and the success / failure determination unit determines that the radio wave is not, Switching means for switching to the first radio wave). A first antenna for receiving a first radio wave;
A second antenna for receiving the second radio wave,
The switching means is
The vehicle radio device according to claim 1, further comprising an antenna changeover switch that selectively connects the detection circuit so that a signal of the first radio wave or the second radio wave is input to the detection circuit. A conversion circuit for converting the received first radio wave signal into a first low frequency band signal and converting the second radio wave signal into a second low frequency band signal;
A first filter that transmits a signal in the first low frequency band;
A second filter that transmits the second low frequency band signal;
A filter changeover switch that selectively connects the conversion circuit so that a frequency-converted signal is input to the first filter or the second filter;
The detection circuit includes:
The automobile radio device according to claim 1 or 2, wherein a baseband signal is detected from a signal transmitted through the first filter or the second filter.

Images