JP5363402B2 - Receiver reference voltage setting device - Google Patents

Description

  The present invention relates to a receiver reference voltage setting device for setting a reference voltage of a receiver.

  2. Description of the Related Art Conventionally, vehicles are equipped with an electronic key system (see Patent Document 1 or the like) that performs ID verification using an ID code transmitted wirelessly from an electronic key. In this electronic key system, there is a key operation free system in which an electronic key automatically responds to a request signal from a vehicle and returns an ID signal, and ID verification is performed using an ID code included in the ID signal. In addition, this electronic key system includes a wireless key system that remotely operates a vehicle device using an electronic key by operating various buttons on the electronic key to skip an ID signal from the electronic key.

  By the way, in communication (smart communication) of a key operation free system, a radio wave (for example, an ACK signal) transmitted from an electronic key to a vehicle is transmitted in a single time and in a short time. Therefore, as shown in FIG. 9, at the time of smart reception in which the vehicle receiver receives a response radio wave from the electronic key, it is necessary to reliably demodulate the reception signal Rx from the first bit. The reference voltage Vref serving as a reference for L determination needs to rise rapidly.

  Here, if the reference voltage Vref is rapidly raised in order to ensure the reception accuracy of smart reception, the fluctuation of the reference voltage Vref becomes large. However, since smart communication is a communication in a relatively narrow range in which the communication distance is in the vicinity of the vehicle, it can be said that noise is difficult to ride on radio waves and the S / N ratio is good. Therefore, the received signal Rx can be normally demodulated even if the reference voltage Vref is rapidly raised.

  On the other hand, the wireless key system communication (wireless communication), radio waves are transmitted from the electronic key for a long time by a plurality of frames having the same content, and the beginning of the frame in the middle of the transmission radio waves is acquired by the receiver of the vehicle, Radio waves from the electronic key are received by the receiver. Therefore, as shown in FIG. 10, at the time of wireless reception in which the vehicle receives a radio wave transmitted from the electronic key, the receiver only needs to be able to determine the received signal Rx from the middle, so the reference voltage Vref does not need to rise rapidly.

  By the way, wireless communication has a longer distance than smart communication, such as a communication distance of several meters from the vehicle. Therefore, the radio wave of wireless communication has a low S / N ratio because the radio wave intensity is low and noise is easily applied to the radio wave. Therefore, in order to ensure the reception accuracy of wireless reception, if the rise of the reference voltage Vref is delayed, the reference voltage Vref does not react to noise with high sensitivity, so that erroneous determination is unlikely to occur during radio wave reception.

JP 2008-255665 A

  However, the time constant that determines the rising speed of the reference voltage Vref is not prepared for each communication in one receiver, and is usually one in one receiver. Therefore, one time constant of the reference voltage Vref is shared by smart communication and wireless communication. In this case, if the rising speed of the reference voltage Vref is satisfied at the time of smart reception, wireless reception is also established regardless of the communication range. Therefore, the smart reception time constant is prioritized at present.

  However, as described above, if the reference voltage Vref rises rapidly, the fluctuation of the reference voltage Vref increases as a contradiction. Therefore, since there is a fact that the S / N ratio is poor in wireless communication, if the fluctuation of the reference voltage Vref is large in this way, there is a high possibility that an error will occur in demodulation determination during wireless reception. For this reason, there is a problem that the sensitivity at the time of wireless reception is not good.

  An object of the present invention is to provide a reference voltage setting device for a receiver capable of ensuring reception sensitivity in both the first wireless communication and the second wireless communication.

In order to solve the above problems, in the present invention, a radio wave is received from either a first radio communication or a second radio communication from a communication terminal, and a received radio wave received from the communication terminal is generated by a reference voltage generation unit. In the reference voltage setting device of the receiver that demodulates the received radio wave, the time constant of the reference voltage is set to a different value for each of the first wireless communication and the second wireless communication The reference voltage setting means , the reference voltage setting means comprising: a time constant setting element for the reference voltage; a monitoring means for measuring an elapsed time since the receiver started radio wave reception; and By switching the setting element based on the monitoring result, the receiver can set the reference voltage by itself. And gist that a value setting means.

  According to this configuration, since the time constant of the reference voltage during the first wireless communication and the time constant of the reference voltage during the second wireless communication can be set to different values, the first wireless communication and the second wireless communication can be set to different values. It is possible to set the time constant of each reference voltage for wireless communication to a value suitable for the received signal. Therefore, while improving the receiving sensitivity of the receiver at the time of the first wireless communication, the receiving sensitivity of the receiver at the time of the second wireless communication is also improved. For this reason, it becomes possible to ensure the receiving sensitivity of the receiver in both the first wireless communication and the second wireless communication.

  According to this configuration, the receiver itself determines the current state of the receiver without obtaining a special notification from the outside, and sets the time constant of the reference voltage based on the determination result. Therefore, since it is not necessary to provide a signal line for notification input in the receiver, this kind of signal line can be reduced by one.

  In the present invention, the time constant setting element includes a plurality of time constant setting capacitors, and the voltage value setting means changes the time constant of the reference voltage by sequentially enabling the plurality of capacitors. Is the gist.

  According to this configuration, since the time constant of the reference voltage is changed by a hardware circuit in which a plurality of capacitors are sequentially enabled, the time constant of the reference voltage can be switched more reliably.

  In the present invention, the time constant setting element is software for setting a time constant of the reference voltage, and the voltage value setting means changes the reference voltage digitally by the software. .

  According to this configuration, since the time constant of the reference voltage is changed programmatically by software, the time constant of the reference voltage can be switched without preparing a complicated hardware circuit.

    According to the present invention, it is possible to ensure reception sensitivity in both the first wireless communication and the second wireless communication.

The block diagram which shows the outline | summary of the electronic key system in 1st Embodiment. The timing chart which shows the communication sequence of a key operation free system. The circuit block diagram which shows the structure of a reference voltage setting apparatus. The wave form diagram which shows the relationship between a received signal and a reference voltage. The circuit block diagram which shows the structure of the reference voltage setting apparatus in 2nd Embodiment. The wave form diagram which shows the outline | summary of the time constant increase process by a computing equation. The circuit block diagram which shows the structure of the reference voltage setting apparatus in 3rd Embodiment. The transition diagram which shows the operation | movement aspect of a time constant change. The wave form diagram which shows the relationship between the ideal reference voltage at the time of the smart reception in the past, and a received signal. Similarly, the wave form diagram which shows the relationship between the ideal reference voltage at the time of the wireless reception, and a received signal.

(First embodiment)
A first embodiment of a reference voltage setting device for a receiver embodying the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, the vehicle 1 transmits a wireless inquiry (request signal Srq) from the vehicle 1 to the electronic key 2 and performs ID verification by a response (ID signal Sid) of the electronic key 2 to the inquiry. A key operation free system 3 is mounted. The key operation free system 3 includes an entry function in which door lock locking / unlocking is permitted or executed when ID verification is established outside the vehicle, and a power transition operation of the vehicle 1 and the engine by the engine switch 4 in the vehicle when ID verification is established in the vehicle. There is an engine start function in which the start operation is permitted. The electronic key 2 corresponds to a communication terminal.

  In this case, the vehicle 1 includes a key verification device 5 that performs ID verification with the electronic key 2, a door lock device 6 that manages a door lock operation, and an engine start device 7 that manages the operation of the engine. These are provided and connected by an in-vehicle bus 8. The key verification device 5 is provided with a verification ECU (Electronic Control Unit) 9 as a control unit of the key verification device 5. In the memory (not shown) of the verification ECU 9, the ID code of the electronic key 2 that forms a pair with the vehicle 1 is registered.

  The verification ECU 9 receives an out-of-vehicle transmitter 10 that transmits LF (Low Frequency) band radio waves outside the vehicle, an in-vehicle transmitter 11 that transmits LF band radio waves into the car, and UHF (Ultra High Frequency) band radio waves. The vehicle tuner 12 is connected. The vehicle transmitter 10 and the vehicle transmitter 11 transmit a request signal Srq as an ID reply request to the electronic key 2 by an LF band radio wave, and try to establish so-called smart communication. The smart communication constitutes one of the first wireless communication and the second wireless communication, and the vehicle tuner 12 corresponds to the receiver.

  As shown in FIG. 2, when the vehicle is parked, the wake signal 13 is intermittently transmitted from the outside transmitter 10 to monitor whether or not smart communication outside the vehicle (external communication) is established. At this time, when the electronic key 2 enters the communication area of the wake signal 13, the electronic key 2 is activated by the wake signal 13 and transmits an ACK signal 14 by radio waves in the UHF band. When the verification ECU 9 receives the ACK signal 14 by the vehicle tuner 12, the verification ECU 9 transmits a vehicle ID 15 as a vehicle ID by radio waves in the LF band. When the electronic key 2 receives the vehicle ID 15, the electronic key 2 performs vehicle ID collation. If the vehicle ID collation is established, the electronic key 2 transmits an ACK signal 16 by radio waves in the UHF band.

  Subsequently, the verification ECU 9 transmits the challenge 17 by radio waves in the LF band in order to execute challenge response authentication. The challenge 17 includes a challenge code whose code is different every time it is transmitted, and a key number that represents the registration key of the vehicle 1. When the electronic key 2 receives the challenge 17, it first performs key number verification, and if the key number verification is established, it passes the challenge code through its own encryption key and generates a response code. Then, the verification ECU 9 transmits a response 18 including this response code and its own ID code by radio waves in the UHF band.

  When the verification ECU 9 transmits the challenge 17 to the electronic key 2, the verification ECU 9 also calculates a response code by passing the challenge code through the encryption key that the verification ECU 9 has. Then, when the response ECU 9 receives the response 18 from the electronic key 2, the verification ECU 9 verifies whether the response code included in the response 18 is correct. The verification ECU 9 also performs ID code verification as to whether or not the ID code included in the response 18 is correct. And if collation ECU9 confirms that both collation was materialized, it will process smart collation (verification outside a vehicle) as establishment, and will permit or perform door lock locking / unlocking by door lock device 6.

  Further, when it is detected by the courtesy switch or the like that the driver has boarded, for example, the transmission of the wake signal 13 is started from the in-vehicle transmitter 11 instead of the out-of-vehicle transmitter 10, and the smart communication (in-vehicle communication) ) Is executed. Then, whether or not smart verification (in-vehicle verification) is established in the vehicle is confirmed by the same procedure as that in the vehicle verification, and when the verification in the vehicle is confirmed, power supply transition operation and engine start operation by the engine starting device 7 are permitted. .

  As shown in FIG. 1, the vehicle 1 is provided with a wireless key system 19 capable of switching between locking and unlocking of the door lock by remote operation with the electronic key 2. In this case, the electronic key 2 is provided with a locking button 20 that is operated when the door lock is locked, and an unlocking button 21 that is operated when the door lock is unlocked. When it is detected that the lock button 20 or the unlock button 21 is operated, a wireless signal Swl corresponding to each button is transmitted by radio waves in the UHF band.

  When wireless communication is established by the vehicle tuner 12 receiving the wireless signal Swl from the electronic key 2, the verification ECU 9 performs ID verification (wireless verification) with the ID code in the wireless signal Swl. Then, the door lock is locked and unlocked by the function code that follows. That is, when the verification ECU 9 receives the lock request signal from the electronic key 2, the door lock device 6 locks the door lock if the wireless verification is established. On the other hand, when receiving the unlock request signal from the electronic key 2, the verification ECU 9 unlocks the door lock of the door lock device 6 if the wireless verification is established. Note that the wireless communication constitutes the other of the first wireless communication and the second wireless communication.

  As shown in FIG. 3, the vehicle tuner 12 is provided with a time constant setting device 22 for switching the time constant of the reference voltage Vref between the smart reception operation and the wireless reception operation. As shown in FIG. 4, the reference voltage Vref is a reference voltage for H / L determination when demodulating the received signal Rx of the vehicle tuner 12, and is generated based on the received signal Rx. If the received signal Rx is higher than the reference voltage Vref, it is determined as “H”, and if the received signal Rx is lower than the reference voltage Vref, it is determined as “L”. The reference voltage Vref rises upon reception of the reception signal Rx and takes a waveform so as to follow the reception signal Rx. The time constant of the reference voltage Vref is a parameter that determines the rising speed of the reference voltage Vref. The time constant setting device 22 corresponds to reference voltage setting means.

  By the way, the radio wave transmitted from the electronic key 2 to the vehicle 1 by smart communication is, for example, ACK signals 14 and 16 and the like, which is single-shot and relatively short-time data. Therefore, in order to receive these data without delay, the reference voltage Vref needs to rise quickly. Therefore, in smart communication, it is preferable to reduce the time constant of the reference voltage Vref so that the reference voltage Vref rises quickly.

  On the other hand, in wireless communication, radio waves are transmitted from the electronic key 2 in a plurality of frames for a long time, and communication can be established if any of these frames can be captured, so the reference voltage Vref does not need to rise rapidly. Therefore, in wireless reception, there is no problem even if the time constant of the reference voltage Vref is large. Rather, since the wireless signal Swl has a poor S / N ratio, it is preferable that the reference voltage Vref rises slowly in order to improve the sensitivity of wireless reception.

  Therefore, the time constant setting device 22 of the present example sets the time constant of the reference voltage Vref and sets the rising speed of the reference voltage Vref faster when the vehicle tuner 12 takes smart reception, thereby setting the smart reception sensitivity. Secure. The time constant setting device 22 ensures wireless reception sensitivity by setting a large time constant of the reference voltage Vref and setting a slow rising speed of the reference voltage Vref when the vehicle tuner 12 performs wireless reception. .

  The vehicle tuner 12 is provided with a receiving circuit 24 connected to the receiving antenna 23. The receiving circuit 24 is connected to the verification ECU 9 via the signal line 25. The verification ECU 9 inputs the reception data Sout composed of binary information of H / L from the reception circuit 24 via the signal line 25 and decodes the data content of the reception data Sout.

  The receiving circuit 24 is connected to the verification ECU 9 via a power line 26. By the way, the vehicle tuner 12 is not always activated, and receives power from the verification ECU 9 via the power supply line 26 only at a specific timing in order to reduce power consumption. However, since it is not known when the wireless signal Swl is transmitted, the verification ECU 9 causes the vehicle tuner 12 to perform a reception operation at regular intervals.

  Further, in smart communication, an ACK response from the electronic key 2 must be accepted after transmission of the wake signal 13 and the vehicle ID 15. Accordingly, the verification ECU 9 causes the vehicle tuner 12 to take a reception operation even at the smart communication ACK response timing. Therefore, the verification ECU 9 activates the vehicle tuner 12 every time in accordance with the execution timing of smart reception or wireless reception.

  The reception circuit 24 includes a primary filter 27 that removes noise from the reception signal Rx of the reception antenna 23, an amplifier 28 that amplifies the reception signal Rx after removal of the primary noise, and the amplified reception signal Rx by the Teherodyne method. A mixer 29 for frequency conversion is provided. The receiving circuit 24 is provided with a secondary filter 30 for removing noise from the frequency-converted received signal Rx and a detection circuit 31 for detecting the received signal Rx after removing the secondary noise. The mixer 29 is connected to an oscillator 32 that generates a local oscillation frequency necessary for frequency conversion.

  The reception circuit 24 is provided with a reference voltage generation circuit 33 that generates a reference voltage Vref based on the received signal Rx after detection. In the reference voltage generation circuit 33, as an element for determining the time constant of the reference voltage Vref, a resistor R and a parallel circuit of a plurality (two in this example) of capacitors C1 and C2 are connected in series. The resistor R is for bias. Capacitors C1 and C2 have one end connected to resistor R and the other end grounded to GND. In the case of this example, C1 that is always valid is a permanent capacitor, and C2 that is valid at the time of wireless reception is an additional capacitor. The received signal Rx after detection is converted into a signal having a rising waveform with a time constant determined by the resistor R and the capacitors C1 and C2, and this is output as a reference voltage Vref. The reference voltage generation circuit 33 constitutes a reference voltage generation unit.

  A changeover switch 34 is connected to the extension capacitor C2 for switching whether or not the extension capacitor C2 is connected to the reference voltage generation circuit 33. When the changeover switch 34 is turned off, only the C1 of the capacitors C1 and C2 works in the reference voltage generation circuit 33, and the time constant of the reference voltage Vref is set small. On the other hand, when the changeover switch 34 is turned on, both C1 and C2 are used in the reference voltage generation circuit 33, and the time constant of the reference voltage Vref is set large. The changeover switch 34 constitutes voltage value setting means.

  The receiving circuit 24 is provided with a data forming circuit 35 that outputs received data Sout consisting of binary information of “H” and “L” to the verification ECU 9 by comparing the received signal Rx after detection with the reference voltage Vref. It has been. The data forming circuit 35 receives the received signal Rx after detection, and also receives the reference voltage Vref from the reference voltage generation circuit 33, and compares the magnitude with the reference voltage Vref. The data forming circuit 35 outputs “H” when the received signal Rx is equal to or higher than the reference voltage Vref, and outputs “L” when the received signal Rx is lower than the reference voltage Vref. The reception data Sout consisting of the group “L” is output.

  The verification ECU 9 is provided with a switching notification output unit 36 that notifies the receiving circuit 24 of whether the vehicle tuner 12 is receiving smart reception or wireless reception as a reception operation. By the way, as described above, the verification ECU 9 knows whether the vehicle tuner 12 is performing smart reception or wireless reception. Therefore, the switching notification output unit 36 sends the reception operation execution notification Sk to the reception circuit 24 through the signal line 37 as a notification of whether the vehicle tuner 12 is taking the smart reception or the wireless reception based on the determination result. Output. The switching notification output unit 36 corresponds to the outside, and the reception operation execution notification Sk corresponds to the notification.

  The reception circuit 24 is provided with a notification input unit 38 for inputting the reception operation execution notification Sk from the switching notification output unit 36. The notification input unit 38 is an interface that inputs a reception operation execution notification Sk from the outside of the reception circuit 24, that is, from the verification ECU 9 through the signal line 37. The notification input unit 38 corresponds to a notification input unit.

  The reception circuit 24 is provided with a time constant switching unit 39 for switching the ON / OFF of the changeover switch 34 and setting the time constant of the reference voltage Vref based on the reception operation execution notification Sk input by the notification input unit 38. When the notification input unit 38 inputs the smart reception execution notification as the reception operation execution notification Sk, the time constant switching unit 39 turns off the changeover switch 34 and sets the time constant of the reference voltage Vref to a small value. On the other hand, when the notification input unit 38 receives the wireless reception execution notification as the reception operation execution notification Sk, the time constant switching unit 39 turns on the changeover switch 34 and sets the time constant of the reference voltage Vref to a large value. The time constant switching unit 39 constitutes voltage value setting means.

Next, the operation of the time constant setting device 22 of this example will be described with reference to FIG.
When the communication operation of the vehicle 1 reaches the start timing (start time) of the smart communication, the verification ECU 9 starts transmitting the wake signal 13 from the outside transmitter 10 (in-vehicle transmitter 11). After transmitting the wake signal 13, the verification ECU 9 supplies electric power to the vehicle tuner 12 via the power line 26 and receives it to the vehicle tuner 12 in order to confirm the presence / absence of an ACK response from the electronic key 2 to the wake signal 13. Take action.

  At this time, since the switching notification output unit 36 recognizes that the reception operation of the vehicle tuner 12 conforms to the smart communication, it outputs the smart reception operation execution notification to the reception circuit 24 as the reception operation execution notification Sk. .

  When the time constant switching unit 39 inputs the smart reception operation execution notification from the switching notification output unit 36 via the notification input unit 38, the time constant switching unit 39 recognizes that the reception operation that the vehicle tuner 12 should take is smart reception. Therefore, the time constant switching unit 39 sets the time constant of the reference voltage Vref small by leaving the changeover switch 34 off and enabling only the capacitor C1.

Incidentally, a Vref1 of the reference voltage Vref at the time of the valid only permanent capacitor C1, the reception signal Rx amplitude maximum value and E0, the t ₂ hours elapsed after the voltage of the reference voltage Vref at the time of the valid only capacitor C1 Assuming E1, the reference voltage Vref is calculated by the following equations (A) and (B).

このように、スマート受信時には、リファレンス電圧Ｖrefの時定数が小さく設定されるので、図４に示すように、リファレンス電圧Ｖrefが急速に立ち上がる。よって、スマート通信の受信信号Ｒｘは単発及び短時間で終了するものであるが、これを問題なく受信することが可能となる。そして、以降の通信で車両チューナ１２がスマート受信動作をとる際には、切換スイッチ３４がオフとなって常設コンデンサＣ１のみが有効となり、リファレンス電圧Ｖrefの時定数が小さく設定される。

Thus, at the time of smart reception, the time constant of the reference voltage Vref is set small, so that the reference voltage Vref rises rapidly as shown in FIG. Therefore, although the reception signal Rx of smart communication ends in a single shot and in a short time, it can be received without any problem. When the vehicle tuner 12 performs a smart reception operation in subsequent communications, the changeover switch 34 is turned off, and only the permanent capacitor C1 is enabled, and the time constant of the reference voltage Vref is set small.

  On the other hand, when the communication operation of the vehicle 1 reaches the start timing (start time) of the wireless communication, the verification ECU 9 supplies power to the vehicle tuner 12 via the power line 26 and causes the vehicle tuner 12 to perform a reception operation. .

  At this time, the switching notification output unit 36 recognizes that the reception operation of the vehicle tuner 12 is equivalent to wireless communication, and therefore outputs the wireless reception operation execution notification to the reception circuit 24 as the reception operation execution notification Sk. .

  When the time constant switching unit 39 inputs the wireless reception operation execution notification from the switching notification output unit 36 via the notification input unit 38, the time constant switching unit 39 recognizes that the reception operation to be performed by the vehicle tuner 12 is wireless reception. Therefore, the time constant switching unit 39 switches the changeover switch 34 to ON and effectively switches the expansion capacitor C2. Therefore, both capacitors C1 and C2 are effective, and the time constant of the reference voltage Vref is set large.

Incidentally, the reference voltage Vref at the time of the enable both capacitors C1, C2 and Vref2, when the t ₂ hours elapsed after the voltage of the reference voltage Vref at this time is E2, the reference voltage Vref by the following equation (C), ( D).

このように、ワイヤレス受信時には、リファレンス電圧Ｖrefの時定数が大きく設定されるので、図４に示すように、リファレンス電圧Ｖrefの立ち上がりが遅くなる。よって、ワイヤレス通信の受信信号ＲｘはＳ／Ｎ比が悪いものであるが、これを問題なく受信することが可能となる。そして、車両チューナ１２がワイヤレス受信をとる度に、切換スイッチ３４がオンに切り換えられ、リファレンス電圧Ｖrefの時定数がスマート受信時に比べて大きく設定される。

Thus, during wireless reception, the time constant of the reference voltage Vref is set large, so that the rise of the reference voltage Vref is delayed as shown in FIG. Therefore, the reception signal Rx of the wireless communication has a poor S / N ratio, but can be received without any problem. Each time the vehicle tuner 12 performs wireless reception, the changeover switch 34 is turned on, and the time constant of the reference voltage Vref is set larger than that during smart reception.

  As described above, in this example, at the time of smart reception, only the permanent capacitor C1 is enabled and the time constant of the reference voltage Vref of the vehicle tuner 12 is set to be small, and the wireless receiver has not only the permanent capacitor C1 but also the additional capacitor C2. Is also effective, and the time constant of the reference voltage Vref of the vehicle tuner 12 is set large. Accordingly, the reference voltage Vref rises quickly during smart reception, and the reference voltage Vref rises slowly during wireless reception. Therefore, the reference voltage Vref rises at a suitable value in each reception. Therefore, both the reception sensitivity of smart reception and the reception sensitivity of wireless reception can be ensured.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) A permanent capacitor C1 and an additional capacitor C2 are provided in the reference voltage generation circuit 33, and the time constant of the reference voltage Vref can be changed by switching the connection state of these capacitors C1 and C2. Therefore, the time constant of the reference voltage Vref of the vehicle tuner 12 can be set to a suitable value corresponding to each of smart reception and wireless reception, so that reception sensitivity can be ensured in both smart reception and wireless reception. .

  (2) The verification ECU 9 and the vehicle tuner 12 are connected by the signal line 37, and a reception operation execution notification Sk (smart reception execution notification, wireless reception execution notification) is output from the verification ECU 9 to the vehicle tuner 12 through the signal line 37. Then, the vehicle tuner 12 knows the reception operation currently being executed by the reception operation execution notification Sk obtained from the verification ECU 9, and sets the time constant of the reference voltage Vref to a value corresponding to the reception operation. For this reason, since it is not necessary to incorporate a processing circuit for judging the content of the receiving operation into the vehicle tuner 12, the configuration of the vehicle tuner 12 can be simplified.

  (3) Another extension capacitor C2 is provided in addition to the permanent capacitor C1, and the time constant of the reference voltage Vref is changed by switching the validity of the extension capacitor C2 by the changeover switch 34. Therefore, since the time constant of the reference voltage Vref is changed by a hardware circuit in which the validity / invalidity of the additional capacitor C2 is switched by the changeover switch 34, the time constant of the reference voltage Vref can be switched correctly.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. This example is a technique that allows the time constant switching of the reference voltage Vref to be executed only by the receiving circuit 24, and the other basic configuration is the same as that of the first embodiment. Therefore, the same portions as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different portions are described in detail.

  As shown in FIG. 5, the receiving circuit 24 is provided with a digital reference voltage setting circuit 41 that sets a value corresponding to the time constant of the reference voltage Vref (hereinafter referred to as a time constant equivalent value) by software. . Note that the time constant equivalent value is a calculated value corresponding to the time constant because of setting the time constant by software calculation, and cannot be strictly called a time constant. I will do it.

  The digital reference voltage setting circuit 41 can appropriately set the time constant of the reference voltage Vref by program processing by executing processing of the reference voltage setting software 43 stored in the memory 42. The digital reference voltage setting circuit 41 is composed of, for example, a one-chip IC (Integrated Circuit). The digital reference voltage setting circuit 41 constitutes a reference voltage generation unit, and the reference voltage setting software 43 constitutes a time constant setting element.

  The receiving circuit 24 is provided with a timer circuit 44 that measures an elapsed time T (see FIG. 6) after the vehicle tuner 12 starts receiving radio waves. The timer circuit 44 measures the elapsed time T from the start of radio wave reception by the vehicle tuner 12 without using smart communication or wireless communication, and outputs the elapsed time T to the digital reference voltage setting circuit 41. The timer circuit 44 corresponds to monitoring means.

  The digital reference voltage setting circuit 41 is provided with a time constant setting unit 45 for setting the time constant of the reference voltage Vref based on the reference voltage setting software 43. The time constant setting unit 45 is functionally generated when the CPU (not shown) of the digital reference voltage setting circuit 41 executes the reference voltage setting software 43. The time constant setting unit 45 constitutes voltage value setting means.

  As shown in FIG. 6, when the elapsed time T by the timer circuit 44 reaches the time corresponding to the end of smart communication ACK reception, the time constant setting unit 45 sets the variable N for determining the reference voltage Vref from the initial value Ns. The value is gradually increased, and when the variable N reaches the maximum value Nk, the value increase is stopped at that point. The ACK reception completion equivalent time refers to the time required to finish receiving the ACK signals 14 and 16 transmitted from the electronic key 2 at the time of smart reception. Therefore, at the initial time of radio wave reception, the time constant of the reference voltage Vref is reduced to correspond to smart reception, and is shifted to a time constant suitable for wireless reception as time passes.

  When the vehicle tuner 12 receives radio waves, the timer circuit 44 starts measuring the elapsed time T from the start of reception. At this time, as shown in FIG. 6, since the variable N, which is a setting parameter of the reference voltage Vref, is the initial value Ns, the time constant of the reference voltage Vref is set to a small value. For this reason, since the rising of the reference voltage Vref is fast, if the received radio wave is a radio wave for smart communication, the radio wave can be received without any problem.

  On the other hand, when the received radio wave is the wireless signal Swl, the reference voltage Vref rises quickly at the initial time of radio wave reception, so there is a high possibility that the wireless signal Swl cannot be received correctly. However, in the case of this example, the setting of the reference voltage Vref is gradually changed over time, and the wireless signal Swl can be received if it can capture one frame in the middle of the signal. Even if Swl cannot be received at the initial stage, it can be received later, so there is no problem.

  The time constant setting unit 45 changes the reference voltage Vref according to the following equation (E) when the elapsed time T by the timer circuit 44 becomes the time corresponding to the end of ACK reception. In equation (E), a variable for setting the reference voltage Vref is N, and the amplitude (intensity) of the reception signal Rx is Si.

このため、電波受信初期時には、スマート受信に対応すべくリファレンス電圧Ｖrefの時定数が小さく設定されていたが、時間経過とともに、リファレンス電圧Ｖrefの時定数が徐々に増加していく。よって、リファレンス電圧Ｖrefの時定数が増加するに従って、リファレンス電圧Ｖrefの立ち上がり速度が徐々に遅く設定されていく。

For this reason, at the initial time of radio wave reception, the time constant of the reference voltage Vref is set to be small so as to correspond to smart reception. However, the time constant of the reference voltage Vref gradually increases with time. Therefore, as the time constant of the reference voltage Vref increases, the rising speed of the reference voltage Vref is set gradually slower.

  By the way, the vehicle tuner 12 at the time of smart reception receives the ACK response and increases the time constant of the reference voltage Vref, and then receives the response 18. That is, the response 18 is received in a state where the rise of the reference voltage Vref is slightly delayed. However, even if the rise of the reference voltage Vref is delayed, the speed of fluctuation after the reference voltage Vref becomes near the intermediate value between “0” and “E0” hardly affects the demodulation. 18 can be received without any problem.

  On the other hand, when the received radio wave is the wireless signal Swl, it cannot be received by the vehicle tuner 12 at the beginning of reception, but the time constant of the reference voltage Vref gradually takes a large value, so that the rise of the reference voltage Vref is delayed. Thus, the wireless signal Swl is captured. Therefore, even if the time constant prioritizing smart reception is set at the initial time of radio wave reception, the time constant can be switched to a value suitable for wireless reception as time passes, so that the wireless signal Swl can be received without any problem. .

  As described above, in the case of this example, even when the time constant of the reference voltage Vref is set to be small in response to smart reception at the initial time of radio wave reception, the time constant of the reference voltage Vref eventually becomes large and wireless reception is performed. A suitable value is taken. Therefore, it is possible to ensure reception sensitivity in both smart reception and wireless reception. Further, since the vehicle tuner 12 switches the time constant itself, the signal line 37 described in the first embodiment can be made unnecessary.

According to the configuration of this embodiment, in addition to the same effects as (1) of the first embodiment, the following effects can be obtained.
(4) The time constant of the reference voltage Vref is changed by incorporating the timer circuit 44 in the vehicle tuner 12 and operating the program of the formula (F) according to the elapsed time T obtained by the timer circuit 44. Therefore, the vehicle tuner 12 can determine the content of the reception operation and set the time constant without obtaining a special notification from the outside. For this reason, since it is not necessary to provide the signal line 37 described in the first embodiment in the vehicle tuner 12, one signal line of this kind can be reduced.

  (5) A digital reference voltage setting circuit 41 is provided in the vehicle tuner 12, and the time constant of the reference voltage Vref is changed programmatically by the reference voltage setting software 43 stored in the memory 42 of the digital reference voltage setting circuit 41. . Therefore, since the time constant of the reference voltage Vref can be changed by a software circuit, the time constant of the reference voltage Vref can be switched without preparing a complicated hardware circuit.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. Since this example is also a technique that enables the time constant switching of the reference voltage Vref to be executed only by the receiving circuit 24, only the parts different from the first and second embodiments will be described in detail.

  As shown in FIG. 7, the reference voltage generation circuit 33 is provided with a plurality of additional capacitors such as C3, C4. These extension capacitors C2, C3,... Are connected in parallel, one end is connected to the resistor R, and the other end is grounded to GND. The extension capacitors C2, C3,... In this example are connected to the reference voltage generation circuit 33 one by one when the reference voltage Vref is increased. The extension capacitors C3 and C4 also constitute a time constant setting element.

  The extension switches C2, C3,... Are connected to changeover switches 34a, 34b, 34c,. The switch group 46 of the changeover switches 34a, 34b, 34c,... The changeover switches 34a, 34b, 34c,... Constitute voltage value setting means.

  The receiving circuit 24 is provided with a timer circuit 44 that measures an elapsed time T after the vehicle tuner 12 starts to receive radio waves. The timer circuit 44 measures the elapsed time T from the start of radio wave reception by the vehicle tuner 12 regardless of smart communication or wireless communication, and outputs the elapsed time T to the time constant switching unit 39.

  When the elapsed time T by the timer circuit 44 reaches the time corresponding to the end of ACK reception of the smart communication, the time constant switching unit 39 sequentially connects the additional capacitors C2, C3,... To the permanent capacitors C1 one by one. Therefore, at the initial time of radio wave reception, only the permanent capacitor C1 is used and the time constant of the reference voltage Vref is set to be small. When the additional capacitors are added one by one in order of C2, C3. The time constant of Vref gradually changes to a large value.

  When the vehicle tuner 12 receives radio waves, the timer circuit 44 starts measuring the elapsed time T from the start of reception. At this time, in the reference voltage generation circuit 33, since only the permanent capacitor C1 is effective, the time constant of the reference voltage Vref is set to a small value. Therefore, since the rising of the reference voltage Vref is fast, when the received radio wave is a radio wave for smart communication, it is possible to receive this radio wave without any problem.

  On the other hand, when the received radio wave is the wireless signal Swl, the reference voltage Vref rises quickly at the initial time of radio wave reception, so there is a high possibility that the wireless signal Swl cannot be received correctly. However, in the case of this example, the additional capacitors C2, C3,... Are connected in order, so that the rising of the reference voltage Vref is gradually changed and the wireless signal Swl is received if one frame in the middle of the signal can be captured. Therefore, even if the wireless signal Swl cannot be received at the initial stage, it can be received after a lapse of a certain time, so there is no problem.

  Further, when the elapsed time T by the timer circuit 44 reaches the time corresponding to the end of the ACK reception, the time constant switching unit 39 first turns on the changeover switch 34a of the extension capacitor C2 to enable the extension capacitor C2. As a result, the time constant of the reference voltage Vref takes a value determined from the resistor R and the two capacitors C1 and C2. Therefore, the time constant of the reference voltage Vref increases and the rising speed of the reference voltage Vref is set to be slow.

  Then, a predetermined time after the extension capacitor C2 is turned on, the changeover switch 34b of the extension capacitor C3 is turned on while the changeover switch 34a of the extension capacitor C2 is turned on, and the extension capacitor C3 is also enabled. As a result, the time constant of the reference voltage Vref further increases, and the rising speed of the reference voltage Vref is further slowed down. Then, each time a predetermined time elapses, the extension capacitors C2, C3,... Are turned on one by one in order to gradually increase the time constant.

  As described above, in this example, since the reference voltage Vref is set to be small at the time of initial reception of radio waves, even if the received radio waves are smart communication radio waves, the radio waves can be received without any problem. Further, when the received radio wave is the wireless signal Swl, it is possible to receive the wireless signal Swl without any problem because it can be received at a time point with a high time constant after a certain time. Therefore, it is possible to ensure reception sensitivity in both smart reception and wireless reception.

According to the configuration of this embodiment, the same effects as (1), (3), and (4) of the above embodiment can be obtained, and the effects described below can be obtained.
(6) It is possible to achieve both omission of the signal line 37 described in the first embodiment and reliable switching of the time constant by changing the time constant to a hardware circuit.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
In the first and second embodiments, the time constant change is not limited to the method of sequentially enabling the additional capacitors. For example, the time constant may be switched by providing a plurality of capacitors that function independently and selectively enabling these capacitors.

In the first embodiment, the signal line 37 is not limited to an independent single line, and may be superimposed on the power supply line 26 to form a single line.
In the first and third embodiments, as the changeover switch 34 (34a, 34b, 34c...), For example, a switching element such as a transistor, a microswitch, or the like can be used.

  In the first to third embodiments, the communication system between the vehicle 1 and the electronic key 2 is not limited to the two systems of smart communication and wireless, and other communication systems may be added to these to form three or more systems.

  In the first to third embodiments, the first wireless communication and the second wireless communication are not limited to smart communication and wireless communication. For example, it is good also as immobilizer communication which performs ID collation with the transponder built in the electronic key 2, and short-distance wireless communication. That is, any communication may be employed for the first wireless communication and the second wireless communication.

-In 1st-3rd embodiment, the frequency used for communication is not limited to LF and UHF, For example, you may use other bands, such as HF (High Frequency).
In the first to third embodiments, the key operation free system 3 is not limited to having different frequencies in the forward path and the return path of bidirectional communication, and may be the same.

In the first to third embodiments, the communication terminal is not limited to the electronic key 2 and may be any terminal as long as it can transmit radio waves.
In the first and second embodiments, the time constant setting element is not limited to the capacitor, and for example, a resistor or a coil may be used. Further, a combination of a capacitor, a resistor, and a coil may be used as appropriate.

-In 1st-3rd embodiment, the vehicle tuner 12 is good also as not only what has only a receiving function but a communication apparatus which can be transmitted / received.
-In 2nd Embodiment, the system at the time of the vehicle tuner 12 judging the receiving operation content itself is not limited to making time into an element. For example, the time constant increasing process may be started when the reception strength of the reception signal Rx is used as a determination factor and the reception strength takes a predetermined value.

In the second embodiment, the start of the time constant increasing process is not limited to the ACK reception end time, but may be, for example, a response reception end time.
-In 2nd Embodiment, the calculating formula which increases a time constant is not limited to Formula (F), You may employ | adopt another formula.

In the second embodiment, the reference voltage setting software 43 may be overwritten (changeable) in another program.
In the first to third embodiments, the time constant setting device 22 is not limited to being used in the vehicle 1 and can be applied to other wireless devices and wireless devices.

  2 ... an electronic key as a communication terminal, 12 ... a vehicle tuner as a receiver, 22 ... a time constant setting device as a reference voltage setting means, 33 ... a reference voltage generation circuit constituting a reference voltage generation unit, 34 (34a, 34b) 34c)... Changeover switch constituting voltage value setting means, 36... Switching notification output section as external, 38... Notification input section as notification input means, 39... Time constant switching section constituting voltage value setting means, 41 ... Digital reference voltage setting circuit constituting reference voltage generation unit, 43 ... Reference voltage setting software constituting time constant setting element, 44 ... Timer circuit as monitoring means, 45 ... Time constant setting constituting voltage value setting means Vref (Vref1, Vref2) ... reference voltage, C1, C2, C3, C4 ... time constant setting elements Receiving operation execution notification capacitor, as Sk ... notification.

Claims (3)

By receiving radio waves from both the first wireless communication and the second wireless communication from the communication terminal, and comparing the received radio waves received from the communication terminal with the reference voltage generated by the reference voltage generation unit, the received radio waves are In the reference voltage setting device of the receiver to be demodulated,
Reference voltage setting means for setting the time constant of the reference voltage to a different value in each of the first wireless communication and the second wireless communication ,
The reference voltage setting means includes
A time constant setting element of the reference voltage;
Monitoring means for measuring the elapsed time since the receiver started receiving radio waves;
A reference voltage for a receiver, comprising: voltage value setting means for causing the receiver to set the reference voltage by switching the setting element based on a monitoring result of the monitoring means. Setting device. The time constant setting element includes a plurality of time constant setting capacitors,
The reference voltage setting device for a receiver according to claim 1 , wherein the voltage value setting unit changes a time constant of the reference voltage by sequentially enabling a plurality of the capacitors. The time constant setting element is software for setting a time constant of the reference voltage,
The reference voltage setting device for a receiver according to claim 1 , wherein the voltage value setting means changes the reference voltage digitally by the software.

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