JP2008227789A - Transmitter/receiver system, transmitter, receiver and keyless entry system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter/receiver system capable of improving the receiving sensibility of a receiver, even when the ambient environments of a transmitter and the receiver differ, and to provide the transmitter and the receiver. <P>SOLUTION: The transmitter 1 is constituted of a temperature sensor 2, a temperature detecting section 3, a ciphering keyless information transmitting section 4, a switch 5, a carrier-frequency signal transmitting section 6 and a transmitting antenna 7. The temperature detecting section 3 detects the ambient temperature of the transmitter 1 by using the temperature sensor 2. The ciphering keyless information transmitting section 4 transmits a ciphering keyless information signal, containing temperature information detected by the temperature detecting section 3 and keyless control information. The switch 5 is used for locking and unlocking a door of a car. The carrier-frequency signal transmitting section 6 inputs the ciphering keyless information signal as a base band signal, and converts the ciphering keyless information signal into an FSK-modulated carrier-frequency signal. The transmitting antenna 7 radiates the carrier-frequency signal into air. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission / reception system, a transmission device, and a reception device, and is particularly suitable for a keyless entry system used for locking / unlocking a door of a vehicle.

In recent years, a so-called keyless entry system that can lock and unlock a vehicle door with a single button without inserting a key into a key cylinder has become widespread.
For the keyless entry system, for example, a transmission / reception system using weak radio waves is used. In such a keyless entry system, when a switch provided on a vehicle key is pressed, an encrypted keyless information signal is transmitted from a transmitter. When the encrypted keyless information signal is received by the receiver provided in the vehicle body, the door of the vehicle is locked and unlocked if it is decrypted and the predetermined keyless information is obtained.

FIG. 7 is a diagram showing a configuration example of a conventional keyless entry system.
The conventional keyless entry system shown in FIG. 7 includes a transmitter 101 provided in a vehicle key and a receiver 102 provided in a vehicle body.
The transmitter 101 includes an encryption keyless information transmission unit 103, a switch 104, a carrier frequency signal transmission unit 105, and a transmission antenna 106.
On the other hand, the receiver 102 includes a receiving antenna 107, a carrier frequency signal receiving unit 108, an encryption keyless information decrypting unit 109, and a control signal sending unit 110.
In the conventional keyless entry system configured as described above, when the driver depresses the switch 104 provided in the key, for example, when opening and closing the door of the vehicle, the encrypted keyless information signal is transmitted to the encrypted keyless information transmission unit. 103. The encrypted keyless information signal is modulated by the carrier frequency signal transmission unit 105 and then radiated to the space via the transmission antenna 106.

  On the other hand, the receiver 102 provided in the vehicle body receives the carrier frequency signal via the receiving antenna 107, and the carrier frequency signal receiving unit 108 converts the inputted carrier frequency signal into an intermediate frequency signal. And then demodulated. The demodulated signal decrypts the keyless information signal in the encrypted keyless information decrypting unit 109, compares the decrypted keyless information with predetermined keyless information specific to the vehicle, and if they match, the control signal sending unit A control signal is sent from 110 to lock or unlock the door.

Next, the detailed configuration of the carrier frequency signal receiving unit 108 will be shown and the problem will be described.
FIG. 8 is a block diagram showing a configuration of a carrier frequency signal receiving unit provided in a conventional receiver.
The carrier frequency signal receiving unit 108 shown in FIG. 8 includes a reception band filter 111, a reception amplifier 112, a local oscillator 113, a mixer unit 114, an intermediate frequency band filter 115, and an FSK demodulation unit 116.
In such a carrier frequency signal receiving unit 108, the carrier frequency signal modulated by FSK via the receiving antenna 107 is input to the reception band filter 111 to remove unnecessary noise components. The carrier frequency signal from which unnecessary noise components have been removed is input to the reception amplifier 112 and amplified to a desired level. The amplified carrier frequency signal is mixed with the frequency signal output from the local oscillator 113 by the mixer unit 114 and converted to an intermediate frequency signal.
The intermediate frequency band filter 115 receives the converted intermediate frequency signal, extracts only components necessary for demodulation, and inputs the extracted intermediate frequency signal to the FSK demodulator 116. The FSK demodulator 116 demodulates the intermediate frequency signal into a keyless information signal that is a baseband signal. Note that there are Patent Literature 1 and Patent Literature 2 as the prior literature.
Japanese Patent Laid-Open No. 11-348732 JP 2006-33590 A

By the way, in the keyless entry system as described above, the ambient temperature environment is often different between the transmitter provided on the vehicle key side and the receiver provided on the vehicle body.
For example, when the vehicle is parked outdoors, the ambient temperature of the receiver provided on the vehicle body side is substantially equal to the outside air temperature. On the other hand, since the transmitter provided on the key side is carried by the user, it becomes almost equal to the ambient temperature of the user. For this reason, when the parking environment of the vehicle and the environment where the user stays are greatly different, the ambient temperature of the receiver and the ambient temperature of the transmitter may be significantly different. For this reason, in the transmission / reception system used for the keyless entry system, even if the temperature on the transmitter side and the temperature on the receiver side are greatly different, the predetermined performance of the intermediate frequency band filter 115 of the receiver is maintained. The pass band was widened.
However, when the intermediate frequency band filter 115 of the receiver has a wide pass band, the S / N on the receiver side deteriorates, the receiver sensitivity of the receiver is lowered, and the transmittable distance is shortened. There was a point.

Moreover, the method shown in patent document 1 and patent document 2 is disclosed as a means to improve the above-mentioned reduction in receiving sensitivity. In Patent Document 1, an intermediate frequency bandpass filter is narrowed to improve reception sensitivity, while a reception level detection circuit having a wideband bandpass filter is provided, so that the reception level is maximized. To control the output frequency. Then, the reception sensitivity is improved by controlling the output frequency of the local oscillator so that the frequency of the obtained intermediate frequency signal matches the center frequency of the narrow band intermediate frequency band filter.
Further, in Patent Document 2, an automatic frequency control (AFC) circuit is provided on the receiver side, an AFC signal is applied to a resonance circuit provided in a demodulation circuit, and the resonance frequency of the resonance circuit is changed according to the AFC signal. The bandwidth of the intermediate frequency signal that can be detected for the signal is expanded. Further, since the output frequency of the local oscillator is changed in accordance with the AFC signal, the signal that can be received without changing the signal bandwidth of the intermediate frequency converter without impairing the signal reception sensitivity of the intermediate frequency converter. More bandwidth.

However, the receivers disclosed in Patent Document 1 and Patent Document 2 have a problem that the circuit of the receiver is complicated, resulting in degradation of stability of reception performance and cost increase.
The present invention has been made to solve the above-described problems, and is a transmission / reception system capable of improving the reception sensitivity of a receiver even when the ambient environment between the transmitter and the receiver is different, An object is to provide a transmitter and a receiver.

In order to achieve the above object, a transmission / reception system of the present invention includes a temperature detection unit that detects ambient temperature and outputs temperature information, and predetermined information that includes temperature information detected by the temperature detection unit when a predetermined operation is performed. A transmitter comprising: an information sending unit for sending a signal; and a transmitter for sending predetermined information output from the information sending unit by modulating with a predetermined modulation method; and a local oscillator, and the received received signal is intermediate An intermediate frequency converter that converts the signal into a frequency signal; a broadband filter that extracts a component necessary for demodulation from the intermediate frequency signal in a wide band; a first demodulator that demodulates the intermediate frequency signal that has passed through the broadband filter; A temperature information acquisition unit that acquires temperature information from information demodulated by one demodulation unit, and a frequency that generates a control voltage for the output frequency of the local oscillator based on the temperature information acquired by the temperature information acquisition unit. A number control voltage generator, a narrowband filter that extracts a component necessary for demodulation from the intermediate frequency signal in a narrower band than the wideband filter, and a second that demodulates the intermediate frequency signal that has passed through the narrowband filter And a demodulator.
According to such a transmission / reception system of the present invention, the transmitter is provided with a function of detecting the ambient temperature, and the detected temperature information is transmitted to the receiver side. On the other hand, in the receiver, the output frequency of the local oscillator provided in the intermediate frequency converter is controlled based on the temperature information from the transmitter, and even if the carrier frequency signal transmitted from the transmitter fluctuates, the receiver The intermediate frequency signal can be maintained at a predetermined value. In this way, since the intermediate frequency filter can be narrowed, the S / N on the receiver side can be improved and the reception sensitivity can be improved.

The transmission / reception system of the present invention further includes a second temperature detection unit that detects ambient temperature and outputs temperature information to the receiver, and the frequency control voltage generation unit includes the temperature information from the transmitter and the second temperature detection. The control voltage of the output frequency of the local oscillator is generated based on the temperature information detected by the unit.
According to such a transmission / reception system of the present invention, since the receiver is also configured to detect the ambient temperature, it is transmitted from the transmitter side when controlling the output frequency of the local oscillator provided in the intermediate frequency conversion unit. Frequency control with high accuracy can be performed based on the temperature information detected and the temperature information detected on the receiver side.

In the transmitter / receiver system of the present invention, the transmitter includes a frequency control voltage signal generator that generates control voltage information of the output frequency of the local oscillator based on the temperature information detected by the temperature detector, and the receiver includes the transmitter The output frequency of the local oscillator is controlled based on the frequency control voltage information transmitted from.
According to such a transmission / reception system of the present invention, in the transmitter, the frequency necessary for setting the output frequency of the local oscillator provided on the receiver side to the optimum frequency based on the temperature information detected by the temperature detection unit. The control voltage value was determined and the frequency control voltage information signal was sent to the receiver. Therefore, by adopting such a method, it is not necessary to determine the frequency control voltage for optimizing the output frequency of the local oscillator based on the received temperature information on the receiver side, and the frequency control voltage information signal Immediately after receiving the signal, the output frequency of the local oscillator can be set to a predetermined value.

In the transmission / reception system of the present invention, the local oscillator is constituted by a voltage controlled piezoelectric oscillator.
According to such a transmission / reception system of the present invention, when the output frequency of the local oscillator is controlled to the optimum value, the frequency can be easily controlled by varying the control voltage.

The transmitter of the present invention also includes a temperature detection unit that detects ambient temperature and outputs temperature information, and an information transmission that transmits predetermined information including temperature information detected by the temperature detection unit when a predetermined operation is performed. And a transmission unit that modulates predetermined information output from the information transmission unit with a predetermined modulation scheme and transmits the modulated information.
According to such a transmitter of the present invention, by providing an ambient temperature detection function, it becomes possible to grasp the ambient temperature on the transmission side in the receiver that receives information from the transmitter. Control according to the ambient temperature of the transmitter becomes possible.

Further, the receiver of the present invention includes a local oscillator, an intermediate frequency converter that converts a received signal received into an intermediate frequency signal, a broadband filter that extracts a component necessary for demodulation from the intermediate frequency signal in a wide band, and a broadband A first demodulator that demodulates the intermediate frequency signal that has passed through the filter, a temperature information acquisition unit that acquires temperature information from information demodulated by the first demodulator, and the temperature information acquired by the temperature information acquisition unit A frequency control voltage generator for generating a control voltage for the output frequency of the local oscillator based on the frequency, a narrow band filter for extracting a component necessary for demodulation from the intermediate frequency signal in a narrow band from the wide band filter, and a narrow band filter And a second demodulator that demodulates the intermediate frequency signal that has passed through the device.
According to such a receiver of the present invention, the output frequency of the local oscillator provided in the intermediate frequency converter is controlled based on the temperature information transmitted from the transmitter. And even if the carrier frequency signal transmitted from the transmitter fluctuates, the intermediate frequency signal can be maintained at a predetermined value in the receiver. Thereby, since the intermediate frequency filter can be narrowed, the S / N on the receiver side is improved, and the reception sensitivity can be improved.

The keyless entry system of the present invention includes the transmission / reception system of the present invention.
According to such a keyless entry system of the present invention, the transmittable distance between the transmitter and the receiver can be increased, and a great effect is exhibited in using the keyless entry system.

Hereinafter, the present invention will be described in detail based on the illustrated embodiments.
In the present invention, the transmitter is provided with a temperature sensor, and the ambient temperature information on the transmitter side is transmitted to the receiver. In the receiver, on the basis of the received temperature information, the local oscillator included in the intermediate frequency converter is provided. The output frequency was made variable. And even if the carrier frequency signal transmitted from the transmitter fluctuates due to changes in ambient temperature conditions, the frequency of the intermediate frequency signal is maintained at a predetermined value by changing the output frequency of the local oscillator in the receiver. . Therefore, even if the intermediate frequency band filter is set to a narrow band, the intermediate frequency signal is reliably received, and the reception sensitivity at the receiver can be improved.

Hereinafter, a keyless entry system to which the transmission / reception system of the present invention is applied will be described as this embodiment. The keyless entry system includes a transmitter provided on a vehicle key and a receiver provided on a vehicle body.
FIG. 1 is a block diagram showing the configuration of the transmitter of the keyless entry system according to the first embodiment.
The transmitter 1 includes a temperature sensor 2, a temperature detection unit 3, an encryption keyless information transmission unit 4, a switch 5, a carrier frequency signal transmission unit 6, and a transmission antenna 7.
The temperature detection unit 3 detects the ambient temperature of the transmitter 1 using the temperature sensor 2. The encryption keyless information transmission unit 4 generates and transmits an encryption keyless information signal including the temperature information detected by the temperature detection unit 3 and the keyless control information. The switch 5 is a switch for locking and unlocking the door of the vehicle. The carrier frequency signal transmission unit 6 receives an encrypted keyless information signal that is a baseband signal, and converts it into, for example, an FSK modulated carrier frequency signal. The transmitting antenna 7 radiates a carrier frequency signal into the air.

The encryption keyless information sending unit 4 includes a temperature information signal generation unit 8, a keyless control signal generation unit 9, and an encryption keyless information signal generation unit 10.
The temperature information signal generator 8 converts the temperature information detected by the temperature detector 3 into a predetermined digitized binary signal. The keyless control signal generation unit 9 generates a keyless control signal uniquely assigned to the vehicle. The encrypted keyless information signal generation unit 10 receives the temperature information signal and the keyless control signal, and generates an encrypted keyless information signal having an encrypted predetermined frame configuration.
The carrier frequency signal transmission unit 6 includes an FSK modulation unit 11 and a transmission amplifier 12.
The FSK modulation unit 11 performs FSK modulation on the input baseband signal. The transmission amplifier 12 adjusts the FSK-modulated encrypted keyless information signal to a predetermined level and emits it to the space via the transmission antenna 7.

Next, the operation of the transmitter of the keyless entry system of the first embodiment will be described.
In the transmitter 1, the temperature detection unit 3 detects the ambient temperature of the transmitter 1 using the temperature sensor 2 and inputs temperature information to the encryption keyless information transmission unit 4. In the encryption keyless information signal transmission unit 4, the temperature information signal generation unit 8 inputs temperature information indicating the ambient temperature of the transmitter 1 detected by the temperature detection unit 3, and converts it into a digital signal having a predetermined number of bits. . The keyless control signal generator 9 generates a keyless control signal having a predetermined number of bits including unique keyless information assigned to the vehicle. The encrypted keyless information signal generation unit 10 receives the input temperature information signal and the keyless control signal uniquely assigned to the transmitter 1 to generate a keyless information signal having a predetermined frame configuration. Further, the encryption keyless information signal generation unit 10 encrypts the keyless information signal with a predetermined algorithm, and generates an encrypted keyless information signal (baseband signal) of binary information including “0” and “1” signals. Then, when the switch 5 is pressed, an encrypted keyless information signal is output to the carrier frequency signal transmitter 6.

  The carrier frequency signal transmission unit 6 uses the voltage control piezoelectric oscillator or the like in the FSK modulation unit 11 to input a baseband signal as a control voltage, and performs control corresponding to “1” and “0” signals of the baseband signal. An FSK modulation signal in which the output frequency of the voltage controlled piezoelectric oscillator is shifted to the center frequency ± Δf is generated by the voltage. In this case, the FSK-modulated shift frequency signal becomes the carrier frequency signal. The transmission amplifier 12 has a function of adjusting the level of the carrier frequency signal output from the FSK modulator 11, and after adjusting to a predetermined level, the transmission antenna 7 is terminated with a predetermined impedance.

Next, an encryption keyless information signal having a predetermined frame configuration will be described.
FIG. 2 is a diagram illustrating a frame configuration example of an encrypted keyless information signal.
In the encrypted keyless information signal shown in FIG. 2, a bit string of a temperature information signal including temperature information is arranged at the head of the frame, a signal transmission stop time is provided for a predetermined time, and then a bit string including a keyless control signal is provided. It is arranged. The signal transmission stop time is a time required until the temperature information signal encrypted on the receiver side is decrypted and the oscillation frequency of the local oscillator is varied. It is preferable that the encrypted keyless information signal is repeatedly transmitted a plurality of times so that the encrypted keyless information can be reliably decrypted in the receiver.

Next, the receiver of the keyless entry system according to the present embodiment will be described.
FIG. 3 is a block diagram showing the configuration of the receiver of the keyless entry system according to the first embodiment.
The receiver 13 includes a receiving antenna 14, an intermediate frequency converter 15, a broadband filter 16, a first FSK demodulator 17, an encrypted temperature information decryption unit (temperature information acquisition unit) 18, and a frequency control voltage. The generator 19, the narrow-band filter 20, the second FSK demodulator 21, the encryption keyless control information decryptor 22, and the control signal transmitter 23 are configured. A portion surrounded by a dotted line in FIG. 3 constitutes the carrier frequency signal receiving unit 24.
The receiving antenna 14 receives a carrier frequency signal radiated into space. The intermediate frequency converter 15 converts the received carrier frequency signal into an intermediate frequency signal. The broadband filter 16 extracts components necessary for demodulation from the intermediate frequency signal converted by the intermediate frequency converter 15.

The first FSK demodulator 17 performs FSK demodulation on the intermediate frequency signal input from the broadband filter 16 and outputs it as a baseband signal. The encrypted temperature information decrypting unit 18 decrypts the encrypted baseband signal and acquires temperature information.
The frequency control voltage generator 19 generates a control voltage for varying the output frequency of the local oscillator provided in the intermediate frequency converter based on the temperature information obtained by the encrypted temperature information decryptor 18.
The narrow band filter 20 is narrower than the wide band filter 16 and improves the S / N ratio when FSK demodulation is performed. The second FSK demodulator 21 FSK-demodulates the intermediate frequency signal input from the narrowband filter 20 and outputs it as a baseband signal.
The encryption keyless control information decrypting unit 22 decrypts the encrypted baseband signal and acquires keyless control information.
The control signal sending unit 23 collates the decoded keyless control information with predetermined keyless control information unique to the vehicle, and sends a control signal for locking and unlocking the door when they match.

The intermediate frequency conversion unit 15 includes a reception band filter 25, a reception amplifier 26, a local oscillator 27, and a mixer 28.
The reception band filter 25 removes unnecessary components such as noise from the received carrier frequency signal. The reception amplifier 26 amplifies the received carrier frequency signal to a predetermined level.
The local oscillator can output a frequency signal for converting the received carrier frequency signal into an intermediate frequency signal, and can vary the oscillation frequency by a control voltage output from the frequency control voltage generator 19. The mixer 28 mixes the received carrier frequency signal with the frequency signal output from the local oscillator 27.

Next, the operation of the receiver of the keyless entry system of the first embodiment will be described.
In the receiver 13, the carrier frequency signal received by the receiving antenna 14 is input to the intermediate frequency conversion unit 15. The intermediate frequency converter 15 receives a carrier frequency signal composed of an FSK modulated signal via the receiving antenna 14 and inputs it to the reception band filter 25 to remove unnecessary noise components. The carrier frequency signal is then input to receive amplifier 26 and amplified to a desired level. The amplified carrier frequency signal is mixed with the frequency signal output from the local oscillator 27 by the mixer 28 and converted into an intermediate frequency signal. The carrier frequency signal is, for example, 312 to 315 MHz, and the band necessary for FSK modulation is about 10 to 100 kHz. Since the intermediate frequency signal is generally 455 kHz, when the carrier frequency signal and the frequency signal output from the local oscillator are mixed, the center frequency of the received FSK modulated wave is 455 kHz. The output frequency of the oscillator 27 is determined.
Further, the local oscillator 27 is constituted by, for example, a voltage-controlled piezoelectric oscillator or the like, and is frequency-controlled by a control voltage output from a frequency control voltage generation unit 19 to be described later, and the ambient temperature information on the transmitter side received from the transmitter An optimal frequency signal is output based on

Next, the encryption keyless information signal converted into the intermediate frequency signal is extracted by the broadband filter 16 and only the necessary components are extracted, and then demodulated in the first FSK demodulator 17 to be a baseband signal. Keyless information signal.
The encrypted temperature information decrypting unit 18 decrypts the encrypted keyless information signal, acquires temperature information contained in the keyless information signal having a predetermined frame structure, and inputs it to the frequency control voltage generating unit 19.
Next, the frequency control voltage generator 19 estimates the frequency shift of the carrier frequency signal output from the transmitter based on the input temperature information indicating the ambient temperature of the transmitter, and the local portion corresponding to the shift A control voltage for changing the oscillation frequency of the oscillator 27 is generated. When the received carrier frequency signal fluctuates, the frequency of the intermediate frequency signal fluctuates from 455 kHz. A narrowband filter 20 that receives an intermediate frequency signal described later is a narrowband filter having a center frequency of 455 kHz. When the frequency of the intermediate frequency signal fluctuates, the narrowband filter 20 has sufficient frequency components necessary for demodulation. There is a risk that an error may occur during FSK demodulation. Therefore, even if the carrier frequency signal output from the transmitter fluctuates, the oscillation frequency of the local oscillator 27 is varied so that the intermediate frequency signal can always maintain 455 kHz.

Next, the method for correcting the frequency of the intermediate frequency signal will be described in more detail.
FIG. 4A is a diagram illustrating an example of the temperature characteristic of the carrier frequency signal output from the transmitter, and FIG. 4B is a diagram illustrating an example of the output frequency characteristic of the local oscillator with respect to the received temperature information. A 455 kHz signal that is an intermediate frequency signal is generated as Fc−Fif = 455 kHz by mixing the received carrier frequency signal Fc with the frequency signal Fif output from the local oscillator 27 in the mixer unit 28. Therefore, on the transmitter side, as shown in FIG. 4 (a), the carrier frequency signal fluctuates in the case of −20 ° C. (Fc−Δf1) Hz with respect to the frequency Fc Hz at the reference temperature of 20 ° C., and + 60 ° C. It is assumed that the case (Fc + Δf2) Hz fluctuates. At this time, in order to mix the received carrier frequency signal and maintain the frequency of the intermediate frequency signal at 455 kHz on the receiver side, the frequency signal output from the local oscillator 27 as shown in FIG. If the received temperature information is FifHz when the received temperature information is the reference temperature 20 ° C., the temperature information is (Fif−Δf1) Hz if the temperature information is −20 ° C., and (Fif + Δf2) if the temperature information is 60 ° C. What is necessary is just to control so that Hz may be output. Therefore, the frequency control voltage generation unit 19 outputs the control voltage input to the local oscillator 27 configured by a voltage control piezoelectric oscillator or the like so that the output frequency of the voltage control piezoelectric oscillator corresponds to the received temperature information and the frequency described above. The value is such that In the above description, the case where the temperature information is −20 ° C. and 60 ° C. has been described. For example, 9 items may be set as appropriate in consideration of performance and cost required for the keyless entry system.
As described above, the frequency control voltage generation unit 19 inputs an optimum control voltage based on the acquired temperature information to the local oscillator 27 constituted by a voltage control piezoelectric oscillator or the like, and maintains the intermediate frequency signal at 455 kHz. Works like this.

  Next, the narrowband filter 20 extracts only the component necessary for demodulation from the intermediate frequency signal output from the intermediate frequency converter 15 and inputs the extracted component to the second FSK demodulator 21. The second FSK demodulator 21 performs FSK demodulation on the input intermediate frequency signal to convert it into a baseband signal composed of encrypted keyless information, and inputs the baseband signal to the encrypted keyless control information decryption unit 22. The encrypted keyless control information decrypting unit 22 decrypts the encrypted keyless information signal, acquires keyless control information included in the keyless information signal having a predetermined frame structure, and inputs the keyless control information to the control signal sending unit 23. Therefore, the control signal sending unit 23 collates the acquired keyless control information with the keyless information uniquely assigned to the vehicle, and outputs a control signal for locking or unlocking the door of the vehicle if they match.

  As described above, in the keyless entry system of the first embodiment, the ambient temperature information is transmitted from the transmitter 1 to the receiver 13, and the receiver 13 uses the local oscillator based on the transmitted temperature information. By controlling the oscillation frequency, the intermediate frequency signal was always maintained at 455 kHz. Therefore, the bandpass filter that receives the keyless control information can be narrowed, and the S / N on the receiving side can be improved. In addition, when performing FSK demodulation for acquiring temperature information, a bandpass filter having a relatively wide band similar to the conventional method is used as a bandpass filter for receiving an intermediate frequency signal, and the received carrier frequency varies. The FSK modulated signal can be received reliably. In this case, the S / N and thermal noise power on the receiving side is somewhat deteriorated because the band-pass filter that receives the intermediate frequency signal becomes a wide band, but the amount of temperature information is small, so the temperature data can be simplified. By using a coding scheme that is resistant to noise, it is possible to reliably acquire temperature information.

Next, a modification of the first embodiment of the keyless entry system according to the present invention will be described. In this modification, in addition to the temperature information sent from the transmitter, the ambient temperature information is also detected in the receiver. Then, the frequency of the local oscillator is controlled based on the temperature information on the transmitter side and the receiver side, so that the intermediate frequency signal is maintained at 455 kHz with higher accuracy.
FIG. 5 is a diagram illustrating a configuration of a modification of the keyless entry system according to the first embodiment. FIG. 5 shows the configuration of the receiver and describes the parts necessary for explaining the modified components. Other components not described are the same as those of the receiver of the keyless entry system shown in FIG.
In the receiver 29 shown in FIG. 5, the ambient temperature of the receiver 29 is detected by the temperature sensor 30 and the temperature detector 31, and is input to the frequency control voltage generator 32. The frequency control voltage generation unit 32 determines the oscillation frequency of the local oscillator 27 based on the temperature information of the transmitter acquired from the encrypted temperature information decoding unit 18 and the temperature information of the receiver 29 acquired from the temperature detection unit 31. When the received carrier frequency signal and the frequency signal output from the local oscillator 27 are mixed, the frequency of the intermediate frequency signal is accurately maintained at 455 kHz. For this purpose, the frequency control signal generation unit 32 inputs an optimal control voltage to the local oscillator 27 based on two pieces of temperature information. Therefore, when performing frequency control of the local oscillator 27, more accurate frequency control is possible, and reception sensitivity is improved.

Next, a second embodiment of the present invention will be described.
In the first embodiment described above, the ambient temperature information of the transmitter is sent from the transmitter to the receiver. In the second embodiment, the receiver side is connected to the receiver from the transmitter. The frequency control voltage information for controlling the output frequency of the local oscillator provided in the system is transmitted. Based on the temperature information detected by the temperature detector, the transmitter determines the frequency control voltage value necessary to make the output frequency of the local oscillator provided on the receiver side the optimum frequency, and the frequency control voltage information Is sent to the receiver. Therefore, by adopting such a method, it is not necessary to select a frequency control voltage for optimizing the output frequency of the local oscillator on the receiver side based on the received temperature information, and the frequency control voltage information Immediately after receiving the signal, the output frequency of the local oscillator can be set to a predetermined value. Therefore, the transmission stop time of the signal having the frame structure of the encryption keyless signal described above is not necessary.

FIG. 6 is a block diagram showing a second embodiment of the keyless entry system according to the present invention. FIG. 6 describes the parts necessary for explaining the features of the second embodiment, and other components not described are the same as those of the keyless entry system shown in FIGS. 1 and 3. It is. In the transmitter 33, the encryption keyless information transmission unit 34 includes a frequency control voltage signal generation unit 35, a keyless control signal generation unit 9, an encryption keyless information signal generation unit 36, and a switch 5.
In the encryption keyless information sending unit 34 configured in this way, temperature information indicating the ambient temperature of the transmitter detected by the temperature detection unit 3 is input to the frequency control voltage signal generation unit 35, and the numerical value of the temperature information is used. Then, a frequency control voltage signal for setting the output frequency of the local oscillator provided in the receiver to a predetermined value is generated. The frequency control voltage signal is a signal composed of a digital signal having a predetermined number of bits.
The keyless control signal generator 9 generates a keyless control signal having a predetermined number of bits including unique keyless information assigned to the vehicle. The encryption keyless information signal generator 36 receives the frequency control voltage signal and the keyless control signal and generates a keyless information signal having a predetermined frame configuration. Furthermore, the encryption keyless information signal generation unit 36 encrypts the keyless information signal with a predetermined algorithm and encrypts the keyless information signal when the switch 5 is pressed as a baseband signal of binary information including “0” and “1” signals. The keyless information signal is output to the carrier frequency signal transmitter 6.

Next, in the receiver 37, the encrypted frequency control voltage information decrypting unit 38 inputs the encrypted keyless information signal composed of the baseband signal demodulated by the first FSK demodulating unit 17. Then, the input encryption keyless information signal is decrypted to acquire the frequency control voltage, and the acquired frequency control voltage is input to the local oscillator 27. Accordingly, the local oscillator 27 is controlled in its output frequency and outputs a frequency signal corresponding to the ambient temperature of the transmitter 33, and thus operates to maintain the intermediate frequency signal at 455 kHz as described above.
In the above description of the keyless entry system, the FSK modulation method has been described as an example of the means for modulating the encrypted keyless information signal. However, this is merely an example, and the ASK (amplitude shift) modulation method may be used. Good.
In the present embodiment, the case where the transmission / reception system of the present invention is applied to a keyless entry system has been described as an example. However, this is only an example, and can be applied to various transmission / reception systems such as an RFID system. Needless to say.

It is the block diagram which showed the structure of the transmitter of the keyless entry system which concerns on 1st Embodiment. It is the figure which showed the example of a frame structure of the encryption keyless information signal. It is the block diagram which showed the structure of the receiver of the keyless entry system which concerns on 1st Embodiment. (A) is a figure which shows the temperature characteristic example of the carrier frequency signal which a transmitter outputs, (b) is a figure which shows the output frequency characteristic example of the local oscillator with respect to the received temperature information. It is a figure which shows the structure of the modification of the keyless entry system which concerns on 1st Embodiment. It is a block diagram which shows 2nd Embodiment of the keyless entry system which concerns on this invention. It is the figure which showed the structural example of the conventional keyless entry system. It is the block diagram which showed the structure of the carrier frequency receiving part with which the conventional receiver was equipped.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 33 ... Transmitter, 2, 30 ... Temperature sensor, 3, 31 ... Temperature detection part, 4, 34 ... Encryption keyless information transmission part, 5 ... Switch, 6 ... Carrier frequency signal transmission part, 7 ... Transmission antenna, DESCRIPTION OF SYMBOLS 8 ... Temperature information signal generation part, 9 ... Keyless control signal generation part, 10, 36 ... Encryption keyless information signal generation part, 11 ... FSK modulation part, 12 ... Transmission amplifier, 13, 29, 37 ... Receiver, 14 ... Receiving antenna, 15 ... intermediate frequency converter, 16 ... wideband filter, 17 ... first FSK demodulator, 18 ... encrypted temperature information decoder, 19,32 ... frequency control voltage generator, 20 ... narrowband filter , 21 ... second FSK demodulator, 22 ... encryption keyless control information decryption unit, 23 ... control signal transmission unit, 24 ... carrier frequency signal reception unit, 25 ... reception band filter, 26 ... reception amplifier, 27 ... local Oscillator, 28 ... Miki Chromatography, 35 ... frequency control voltage signal generating section, 38 ... encryption frequency control voltage information decoder

Claims (7)

A temperature detection unit that detects ambient temperature and outputs temperature information; an information transmission unit that transmits predetermined information including the temperature information detected by the temperature detection unit when a predetermined operation is performed; and the information transmission unit A transmitter comprising: a transmission unit that modulates and transmits predetermined information output from a predetermined modulation scheme;
An intermediate frequency converter that includes a local oscillator, converts the received signal to an intermediate frequency signal, a broadband filter that extracts a component necessary for demodulation from the intermediate frequency signal in a wide band, and the broadband filter that has passed through the broadband filter Based on a first demodulator that demodulates the intermediate frequency signal, a temperature information acquisition unit that acquires the temperature information from information demodulated in the first demodulator, and the temperature information acquired in the temperature information acquisition unit A frequency control voltage generation unit that generates a control voltage of an output frequency of the local oscillator, a narrowband filter that extracts a component necessary for demodulation from the intermediate frequency signal in a narrower band than the wideband filter, and the narrowband filter A second demodulator that demodulates the intermediate frequency signal that has passed through the bandpass filter;
A transmission / reception system comprising:   The receiver includes a second temperature detector that detects ambient temperature and outputs temperature information, and the frequency control voltage generator detects the temperature information from the transmitter and the second temperature detector. The transmission / reception system according to claim 1, wherein a control voltage of an output frequency of the local oscillator is generated based on the temperature information. The transmitter includes a frequency control voltage signal generation unit that generates control voltage information of an output frequency of the local oscillator based on the temperature information detected by the temperature detection unit,
The transmission / reception system according to claim 1, wherein the receiver controls an output frequency of the local oscillator based on frequency control voltage information transmitted from the transmitter.   The transmission / reception system according to any one of claims 1 to 3, wherein the local oscillator includes a voltage-controlled piezoelectric oscillator. A temperature detector that detects ambient temperature and outputs temperature information;
An information sending unit for sending predetermined information including the temperature information detected by the temperature detecting unit when a predetermined operation is performed;
A transmission unit that modulates and transmits predetermined information output from the information transmission unit by a predetermined modulation method;
A transmitter comprising: An intermediate frequency converter that includes a local oscillator and converts the received signal received into an intermediate frequency signal;
A broadband filter for extracting a component necessary for demodulation from the intermediate frequency signal in a wide band;
A first demodulator that demodulates the intermediate frequency signal that has passed through the broadband filter;
A temperature information acquisition unit that acquires temperature information from the information demodulated in the first demodulation unit;
A frequency control voltage generation unit that generates a control voltage of an output frequency of the local oscillator based on the temperature information acquired by the temperature information acquisition unit;
A narrowband filter for extracting a component necessary for demodulation from the intermediate frequency signal in a narrower band than the wideband filter;
A second demodulator that demodulates the intermediate frequency signal that has passed through the narrowband filter;
A receiver comprising:   A keyless entry system comprising the transmission / reception system according to any one of claims 1 to 4.

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