JP3816239B2 - Keyless entry receiver and keyless entry control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a keyless entry receiver and a keyless entry control system, and more particularly to improving communication performance.
[0002]
[Prior art]
In general, locking / unlocking of vehicle doors, etc. is performed by inserting a mechanical key common to the ignition key into a key cylinder of the door. For example, a remote operation keyless entry control system that does not use mechanical keys has been adopted. This keyless entry control system transmits a code assigned to each vehicle from the transmitter by the driver's operation to the keyless entry receiver on the vehicle side, demodulates it, and collates it with the code stored on the vehicle side. Then, the operation of the electromagnetic actuator or the like unlocks the vehicle, which has the advantage that the door can be locked / unlocked at night.
[0003]
FIG. 7 shows an example of the configuration of such a keyless entry control system. The transmitter 4b is built in the handle portion of the key 4 held by the driver, and a switch (door lock, door unlock, trunk open, panic) 400 is provided. A storage unit 401 that stores an ID code corresponding to the switch 400, and a control unit 402 that reads the ID code from the storage unit 401 in response to the switch 400. When the driver presses one of the switches 400, The control unit 402 outputs a code signal corresponding to the switch 400 to the oscillation unit 403. The oscillation unit 403 includes a 314.35 MHz crystal oscillator 4032 for generating a carrier signal. A frequency modulation (FM) signal is generated using a code signal composed of a binary FSK signal as a modulation signal and transmitted from an antenna 404. The The transmitter 4b includes a battery 405 and a voltage control unit 406 for supplying power to these units.
[0004]
The keyless entry receiver 5 includes a receiving unit 5a and a control unit 5b. The receiving unit 5a receives a radio wave received by the antenna 500 as a first band pass filter (BPF) 501, a high frequency (RF) amplifier 502, a mixer. 503, a superheterodyne system including a local oscillator 504. The local oscillator 504 has a fixed oscillation frequency using a 313.895 MHz crystal oscillator 5041. The received wave signal is frequency-converted by the mixer 503 into an intermediate frequency signal from the oscillation signal of the local oscillator 504, and the center frequency is 455 kHz. The signal is input to the second bandpass filter (BPF) 505, and the intermediate frequency (IF) signal of 455 kHz is passed through the heterodyne signal. The IF signal is amplified by an IF amplifier 506, and then demodulated by a detection circuit 507, a phase shifter 508, a low-pass filter (LPF) 509, and a waveform shaping circuit 510 to obtain a digitized code signal.
[0005]
The control unit 5b determines whether or not the received signal strength known from the received signal strength detection circuit (RSSI circuit) 511 is sufficient. If the received signal strength is sufficient, the control unit 5b outputs the code signal to the body computer 6 as it is. The determined code is determined and a control signal corresponding to the code is output to the drive circuit of the electromagnetic actuator.
[0006]
[Problems to be solved by the invention]
By the way, the stability of the keyless entry receiver depends on the stability of the transmission / reception frequency, and particularly depends on the performance of the oscillator used in the transmission / reception device. Therefore, it is necessary to use a resonator having a small frequency deviation and good stability, which increases the cost. On the other hand, if the bandwidth of the second BPF is widened, the radio wave from the transmitter can be picked up even if the frequency stability is somewhat poor, but the S / N deteriorates because noise is likely to enter, resulting in sensitivity. Becomes worse.
[0007]
The present invention has been made in view of the above circumstances, and a keyless entry receiver capable of receiving with high sensitivity even when an oscillator having insufficient performance is used as a local oscillator of a transmitter or a local oscillator of a receiver. The purpose is to provide. The present invention also provides a keyless entry control system that allows a receiver to receive with high sensitivity even when an oscillator that does not necessarily have sufficient performance is used as an oscillator of a transmitter or a local oscillator of a receiver. With the goal.
[0008]
[Means for Solving the Problems]
In the invention according to claim 1, the keyless entry receiver has a superheterodyne receiver configured to input an intermediate frequency signal between the received wave signal and the local oscillation signal of the local oscillator to the intermediate frequency filter, A radio wave modulated by the code signal and transmitted from the transmitter is received, the code signal is demodulated, and a control signal corresponding to the code signal is output to the vehicle control unit. The intermediate frequency filter includes a narrow band intermediate frequency filter and a wide band intermediate frequency filter. And the bandwidth switching means for switching the intermediate frequency filter to any one, the sweep means for controlling the local oscillator to sweep the oscillation frequency of the local oscillator within a predetermined range, the received signal strength detecting means for detecting the received signal strength, And sweep control means for controlling the sweep means and the bandwidth switching means. The sweep control means includes a wideband intermediate frequency filter, a received wave search control for searching the received wave signal based on the received signal strength detected by the received signal strength detecting means, and a narrowband intermediate filter when the received wave signal is detected. The frequency filter is set to perform tuning control for determining the tuning of the received wave signal based on the received signal strength and stopping the oscillation frequency sweep at the sweep point determined to be tuned.
[0009]
Since the received wave signal is tuned by sweeping the oscillation frequency of the local oscillator, even if the frequency deviation of the oscillation frequency of the transmitter oscillator or the receiver local oscillator is large and the stability is not good, High sensitivity can be received.
[0010]
Moreover, in the received wave search control, the bandwidth of the intermediate frequency filter is widened to enable fast search of a stable received wave signal without causing loss of the received wave signal due to the response delay of the received wave signal. In the control, the bandwidth of the intermediate frequency filter is narrowed to enable accurate tuning, and the S / N is improved so that weak radio waves can be received.
[0011]
According to a second aspect of the present invention, the sweeping means is configured such that the oscillation frequency of the local oscillator is swept stepwise at a predetermined frequency interval, and the frequency interval is switchable. In the received wave search control, the sweep control means sweeps the oscillation frequency by increasing the frequency interval, and in the tuning control, the frequency interval is decreased, and the oscillation frequency is centered on the oscillation frequency when the received wave signal is detected. And a range including the bandwidth of the broadband intermediate frequency filter is set to be swept, and the bandwidth of the broadband intermediate frequency filter is set to a frequency interval in the substantially received wave search control.
[0012]
In the received wave search control, the frequency interval is large, and the bandwidth of the wideband intermediate frequency filter is substantially the frequency interval in the received wave search control, so it is possible to always sweep at a high speed while covering a wide frequency range. it can.
[0013]
According to a third aspect of the present invention, there is provided a superheterodyne receiver that inputs an intermediate frequency signal between a received wave signal and a local oscillator signal of a local oscillator to an intermediate frequency filter, and is frequency-modulated by a code signal. The radio wave transmitted from the transmitter is received, the code signal is demodulated, and a control signal corresponding to the code signal is output to the vehicle control unit. A sweeping means for controlling the local oscillator to sweep the oscillation frequency of the local oscillator within a predetermined range, a received signal intensity detecting means for detecting the received signal intensity, and a sweep control means for controlling the sweeping means are provided. The sweep control means includes a received wave search control for detecting a received wave signal based on the received signal intensity detected by the received signal intensity detecting means, and a tuning of the received wave signal based on the detected output intensity when the received wave signal is detected. Is set to perform tuning control to stop the sweep of the oscillation frequency at the sweep point determined to be tuned.
[0014]
Since the received wave signal is tuned by sweeping the oscillation frequency of the local oscillator, even if the frequency deviation of the oscillation frequency of the transmitter oscillator or the receiver local oscillator is large and the stability is not good, High sensitivity can be received.
[0015]
Moreover, in the tuning control after the received wave search control is performed and the received wave signal is detected, the tuning is performed based on the detection output intensity that is monotonous with respect to the frequency. Even if is used, the frequency spectrum can be tuned at the center frequency of the received wave signal having a double-headed profile. As a result, the bandwidth of the intermediate frequency filter can be narrowed, and the S / N can be improved to receive even weak radio waves. In addition, since the detection output intensity is not basically saturated in the frequency modulation signal, tuning can be achieved even in a strong electric field.
[0016]
According to a fourth aspect of the present invention, the sweep control means detects saturation of the received signal intensity, and the received wave search control is performed from the received wave signal search based on the received signal intensity to the received wave based on the detected output intensity. Set to switch to signal search.
[0017]
When the received signal strength is saturated, it is difficult to search for a received wave signal based on the received signal strength, and tuning cannot be performed. However, as described above, the received wave signal can be searched by performing the received wave search control based on the detection output intensity that is basically not saturated even if the received signal intensity is saturated. Therefore, it is possible to avoid the state of being unable to be tuned after the radio wave is transmitted from the transmitter, and it is possible to output the control signal to the vehicle control unit with high responsiveness.
[0018]
According to the fifth aspect of the present invention, when the received wave signal cannot be tuned even if the tuning control is continuously performed a predetermined number of times, the received signal strength is determined to be saturated.
[0019]
When tuning is not possible as described above, the received signal strength is abnormally increased regardless of the correct received wave signal from the transmitter, and therefore the received signal strength can be determined to be saturated. By such determination, the saturation of the received signal strength is easily known.
[0020]
In a sixth aspect of the invention, the transmitter for transmitting the radio wave frequency-modulated by the code signal corresponding to the switch operation to the keyless entry receiver transmits the non-modulated radio wave prior to the transmission of the frequency-modulated radio wave. The keyless entry control system is constructed in combination with the keyless entry receiver according to any one of claims 3 to 5.
[0021]
Since the receiver tunes the received wave signal by sweeping the oscillation frequency of the local oscillator, even if the frequency deviation of the oscillation frequency of the transmitter oscillator or the local oscillator of the receiver is large and the stability is not good, the transmitter Can be received with high sensitivity, and good communication can be performed between the transmitter and the receiver.
[0022]
When an unmodulated radio wave is received, the detection output of the keyless entry receiver is constant as long as the reception frequency does not change. Therefore, tuning control and received wave search control can be performed satisfactorily based on such stable detection output.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a configuration of a keyless entry control system to which a keyless entry receiver (hereinafter simply referred to as a receiver) of the present invention is applied. The transmitter 4a built in the ignition key 4 is substantially the same as that described in the prior art except that the oscillator of the oscillation unit 403 uses a SAW 4031 which is inexpensive but slightly less stable in place of the crystal oscillator. Therefore, the description is omitted, and the receiver 1 will be mainly described.
[0024]
The receiver 1 includes a receiver 1a and a controller 1b, and is mounted on the vehicle together with the body computer 3. The receiving unit 1 a has a superheterodyne configuration, and a received wave signal received from the antenna 100 is input to the mixer 103 via the first BPF 101 and the RF amplifier 102. The pass band of the BPF 101 is set so that the transmission radio wave can be felt even if the transmission frequency of the transmitter 4a varies due to drift of the oscillation unit 401 or the like. The mixer 103 constitutes a frequency conversion circuit with a voltage controlled oscillator (VCO) 104 serving as a local oscillator, and generates an intermediate frequency signal between the received wave signal and the oscillation signal of the VCO 104. This intermediate frequency signal is input to the second BPFs 105W and 105N, which are intermediate frequency filters, via a changeover switch 105S, which is a bandwidth switching means. BPFs 105W and 105N are made of ceramic filters or the like and have a center frequency of 455 kHz. The bandwidth of BPF 105W is wide (bandwidth BW (W)), and BPF 105N is narrow (bandwidth BW (N)).
[0025]
The intermediate frequency (IF) signal that has passed through one of the BPFs 105W and 105N is amplified by the IF amplifier 106 and input to the detector 107 and the phase shifter 108. The detector 107 and the phase shifter 108 constitute a frequency discriminating circuit, and converts a frequency change into an amplitude change. The detection output (disclinator output) output from the detector 107 further passes through the LPF 109 and the waveform shaping circuit 110 for removing high frequency components, and the code signal is demodulated, and the code signal is input to the control unit 1b.
[0026]
The receiving unit 1a includes an RSSI circuit 111 serving as received signal strength detecting means, and outputs an RSSI voltage VRSSI. The RSSI voltage VRSSI increases as the input to the IF amplifier 106 increases, and the received signal strength can be detected.
[0027]
The VCO 104 is configured using a SAW 1041 as an oscillator, and the receiving unit 1 a is provided with a scanning circuit 2 that outputs a control voltage for controlling the frequency of the VCO 104. The VCO 104 is configured such that the oscillation frequency is high when the control voltage input from the scanning circuit 2 is high, and the oscillation frequency is low when the control voltage is low.
[0028]
The scanning circuit 2 includes a counter 202 and a DA converter 203 that constitute the sweep means 2b. The counter 202 includes a clock 1 having a different clock frequency from the first and second clocks 208 and 209 via the changeover switch 205. , Clock 2 is input. The counter 202 is configured to repeat counting up / down within a predetermined range by any of the clocks 208 and 209. The counter value to be counted up / down is converted into an analog signal by the DA converter 203, and the oscillation frequency of the VCO 104 is swept (scanned) as a control voltage. This control voltage is an isosceles triangular wave. Here, the resolution of the DA converter 203, that is, the number of bits, is greater than the value obtained by dividing the variable range of the oscillation frequency of the VCO 104 by the frequency at which the oscillation frequency of the VCO 104 is desired to be adjusted. Note that the frequency at which the oscillation frequency of the VCO 104 is desired to be adjusted is the minimum variable of the oscillation frequency. This requires a smaller one as the bandwidth of the narrow band BPF 105N is narrower, and is set smaller than the bandwidth of the narrow band BPF 105N. This is to avoid creating a frequency range that is insensitive to the received wave signal.
[0029]
The clock frequencies of the clocks 208 and 209 are desirably set to a value that is not an integral multiple of 455 kHz, which is the intermediate frequency, so that the clock signal is not mixed into the second BPF 105W or 105N. For example, 455 kHz is multiplied by 8.5 and set to 3.9675 MHz.
[0030]
Here, the range in which the counters 208 and 209 count up / down is such that the oscillation frequency of the VCO 104 varies in the transmission frequency of the transmitter 4a (drift, etc.) and the oscillation frequency of the VCO 104 due to the stability of the SAW 1041 (drift, etc.). ). For example, when the transmission frequency of the transmitter 4a and its variation is 314.35 MHz ± 0.15 MHz and the variation of the oscillation frequency of the VCO 104 is ± 0.15 MHz, the mixer 103 obtains an intermediate frequency signal of 455 kHz. The range of the oscillation frequency of the VCO 104 may be 313.895 MHz ± 0.3 MHz. Accordingly, the count up / down range of the counter 202 is determined so as to be variable within the frequency range.
[0031]
The comparator 200 and the control logic 201 constituting the sweep control means 2a of the scanning circuit 2 controls the operation of the counter 202, and locks the oscillation frequency of the VCO 104 when a received wave signal is sensed. The comparator 200 outputs binary values of “H” and “L” depending on the magnitude of two comparison signals. The RSSI voltage VRSSI output from the RSSI circuit 111 is input as one comparison signal, and the other comparison signal is input. As a result, the reference voltage 1 and the reference voltage 2 higher than the reference voltage 1 are input from the first and second reference voltage generators 206 and 207 through the changeover switch 204.
[0032]
The control logic 201 is composed of a logic operation circuit or the like that executes a control flow to be described later, and controls the counter 202 to control the scanning and stopping of the oscillation frequency of the VCO 104, the scanning speed, and the like.
[0033]
The control logic 201 controls the changeover switch 105S that switches between the BPFs 105W and 105N.
[0034]
The control unit 1b is composed of a microcomputer or the like, compares the demodulated code signal input from the waveform shaping circuit 110 with a pre-stored ID code, and if it matches, switches the transmitter 4a to the body computer 3 as the vehicle control unit. A control signal corresponding to 400 operations is output. The body computer 3 opens and closes the door by driving an actuator for opening and closing the door, for example, according to the control signal.
[0035]
In addition, the control unit 1b operates in the sleep mode by the timer control, performs an intermittent operation that repeats the operation period and the sleep period, and the reception unit 1a performs an intermittent operation that alternately repeats the operation period and the sleep period. It is controlled to reduce the dark current. Since the counter 202 backs up the memory, it is energized for backup even during the sleep period.
[0036]
The operation of the receiver 1 of the present invention will be described. 2 and 3 are timing charts of each part of the receiver 1, and FIGS. 4 and 5 are control flows executed in the control logic 201.
[0037]
In FIG. 2, the first half shows the case where there is no radio wave from the transmitter 4a, and the second half shows the case where the radio wave from the transmitter 4a enters when the switch 400 of the transmitter 4a is operated during the operation period. Yes.
[0038]
First, a case where there is no radio wave will be described. The control flow in FIG. 4 starts when the receiving unit 1a wakes up by the control unit 1b. In the control flow, steps S10 to S33 are received wave search control steps, a received wave is searched at high speed, and steps S40 to S40 are tuning control steps, and the reception frequency is fixed to the tuning frequency of the received wave signal. In step S10, the changeover switches 204, 205, and 105S are switched to set the low-voltage reference voltage 1, the fast clock 1, and the wideband BPF 105W.
[0039]
In step S10, the counter 202 is allowed to sweep (scan) the oscillation frequency of the VCO 104. That is, the output of the counter 202 analogized by the DA converter 203 is up and down at a high speed according to the clock frequency of the clock 1, and becomes an isosceles triangular wave as shown in FIG. As a result, the oscillation frequency of the VCO 104 changes from the low side to the high side within the predetermined range, reverses and changes from the high side to the low side, and this is repeated. The change in the oscillation frequency of the VCO 104 is also an isosceles triangular wave.
[0040]
In the mixer 103, the received wave signal from the RF amplifier 102 and the oscillation signal of the VCO 104 are mixed, and the intermediate frequency signal is input to the wideband BPF 105W to generate the oscillation signal of the VCO 104 and the intermediate frequency signal of 455 kHz. Only pass through the broadband BPF 105W. The oscillation frequency of the VCO 104 is scanned within a predetermined range, and the received wave signal is searched.
[0041]
When scanning is started, it is determined in step S30 whether the output of the comparator 200 is “L” or “H”. If there is no radio wave from the transmitter 4a, the RSSI voltage VRSSI is low, and therefore the output of the comparator 200 remains "H", and the process proceeds to step S31. The output becomes “L”, which will be described later).
[0042]
In step S31, it is determined whether or not the current time T has not exceeded the reference operation time TW from the wake-up time T0. If not, the process returns to step S20, and the VCO 104 continues until the reference operation time TW has elapsed. Scanning of the oscillation frequency continues. In the example shown in the figure, the reference operation time TW is set to a length for which the oscillation frequency is scanned four times if it is not locked in the middle. When the reference operation time TW elapses, the present control routine is ended, and the control unit 1b receives the end of the control routine and causes the receiving unit 1a to sleep again (step S32).
[0043]
Next, the operation when a radio wave enters will be described. It is assumed that after the first scanning is completed, the driver operates the switch 400 of the transmitter 4a and a radio wave of 314.35 MHz is transmitted from the transmitter 4a. When the radio wave from the transmitter 4a is sensed, the RSSI voltage VRSSI exceeds the reference voltage 1 at time T1 during the second scanning and the output of the comparator 200 becomes “L” (step S30), and the counter 202 is activated. Is stopped and the oscillation frequency of the VCO 104 is locked. By using the clock 1 having a high frequency in this way, the scanning of the oscillation frequency of the VCO 104 can be accelerated, and the received wave signal can be detected in a short time.
[0044]
In the next step S33, it is determined whether or not the current time T has passed the standby time TH1 from the detection time T1 of the received wave signal. If not, the process returns to step S30, and the detection state of the received wave signal is on standby. It is determined whether time TH1 lasts. The waiting time TH1 is set to 1 ms, for example. If the output of the comparator 200 returns to "H" before the standby time TH1 has elapsed, it is determined that the detected received wave signal is a noise radio wave, and thus the process proceeds to step S31.
[0045]
Here, the oscillation frequency of the VCO 104 is tuned when it becomes f3 (313.895 MHz) which produces a 314.35 MHz transmission signal from the transmitter 4a and a 455 kHz intermediate frequency signal, but f1 (313) is slightly higher than f3. .900 MHz). This is because the scanning is slightly overshooted by the response delay of the RSSI circuit 111 although it is tuned when the frequency of the intermediate frequency signal falls within the bandwidth of the broadband BPF 105. Since the receiver 1 uses the broadband BPF 105W, the received wave signal is not lost. That is, the output of the comparator 200 maintains “L”.
[0046]
In the present embodiment, the tuning deviation due to the high-speed search can be eliminated by executing the tuning control procedure in step S40 and subsequent steps, and both high-speed search of the received wave signal and high-precision tuning are achieved. Yes. That is, when it is recognized in steps S30 and S33 that there is a high probability that the received wave signal is a transmitted radio wave from the transmitter 4a, first, in S40, the reference voltage 1 is switched from the reference voltage 1 to a higher reference voltage 2, and the clock 1 The clock 2 is switched to a lower frequency. In addition, the broadband BPF 105W is switched to the narrow band BPF 105N.
[0047]
Steps S50 to S52 are procedures for returning the oscillation frequency of the VCO 104 to a constant value. In step S50, the scanning direction at time T1 when the received wave signal is detected is determined by whether the counter 202 is up. If it is down, the process proceeds to step S51, and a constant value CB is added to the current counter C to obtain a return counter C2. If it is up, the process proceeds to step S52, and as shown in the time chart, a constant value CB is subtracted from the current counter C to obtain a return counter C2. Here, the constant value CB is a count value corresponding to half of the bandwidth BW (W) of the wideband BPF 105W. Thus, at the time T2 after the standby time TH1 has elapsed from the received wave signal detection time T1, the oscillation frequency of the VCO 104 returns to f2, which is BW (W) / 2 away from f1. In the illustrated example, f2 is f1−BW (W) / 2.
[0048]
In the subsequent step S60, scanning is performed from the returned oscillation frequency f2 corresponding to the bandwidth end of the broadband BPF 105W at the scanning speed corresponding to the clock 2 and the tuning determination level of the received wave signal corresponding to the reference voltage 2.
[0049]
Steps S70 to S73 are substantially the same as steps S30 to S33, and it is determined whether or not the output of the comparator 200, which is a comparison output of the RSSI voltage VRSSI and the reference voltage 2, is “L”. Scanning (step S60) is continued, and when the elapsed time from the scanning start time (time T2) exceeds the reference operation time TW, this control routine is terminated and the sleep period is entered again (step S72).
[0050]
If the output of the comparator 200 is “L” in step S70, the process proceeds to step S73, and it is determined whether or not the current time T has exceeded the standby time TH2 from the tuning time T3 of the received wave signal. The setting of the waiting time TH2 is the same as the setting of the waiting time TH1, and the length is set to 2 ms, for example. If the elapsed time from the detection time T3 does not exceed the waiting time TH2 in step S73, the process proceeds to step S74, where the current counter C is counted from the counter C2 at the start of scanning to the counter value 2CB corresponding to the bandwidth BW (W) of the wideband BPF 105W. If it does not exceed, it returns to step S70. If the count change from the counter C2 at the start of scanning exceeds 2CB in step S74, it is no longer recognized as the received wave signal detected at time T1, and the process returns to step S10 to return to the reference voltage 1, clock 1, and broadband. The received wave signal is searched again with the BPF 105W setting.
[0051]
If the elapsed time from the detection time T3 exceeds the standby time TH2 in step S73, the process proceeds to step S80, and the code reading permission is given to the control unit 1b. The control unit 1b reads a code from the demodulated signal output from the waveform shaping circuit 110, and outputs a corresponding control signal such as a door open to the body computer 3 if it matches the ID code stored in advance.
[0052]
In step S90, the RSSI voltage VRSSI is compared with the reference voltage VS to check whether it is higher than the reference voltage VS. This is a procedure for determining whether or not the RSSI voltage VRSSI is lowered due to drift of the oscillation frequency or transmission frequency of the VCO 104, and is a procedure for improving the reliability of code reading. If the RSSI voltage VRSSI is higher than the reference voltage VS in step S90, code reading by the control unit 1b is accepted (step S80), and if it is lower than the reference voltage VS, it is determined that it is difficult to read the ID code accurately, and step S100. Proceed to The reference voltage VS is the same as the reference voltage 2, and the RSSI voltage VRSSI is checked based on the output of the comparator 200.
[0053]
The procedure after step S100 is a procedure for re-tuning the reception frequency that has been detuned due to the drift or the like. In the illustrated example, the oscillation frequency of the VCO 104 is changed from f3 to f5 '. In steps S100 to S102, the oscillation frequency of the VCO 104 is returned to a constant value. In step S100, the scanning direction at the tuning completion time (time T3) is determined based on whether the counter is up. If it is down, the process proceeds to step S101, and a constant value CB 'is added to the counter C3 at the time of tuning to obtain a return counter C5. If it is up, the process proceeds to step S102, and as shown in the time chart, a constant value CB is subtracted from the current counter C to obtain a return counter C5. The example shows the case of subtraction, and the oscillation frequency of the VCO 104 is reduced from f5 'to f5. Here, the constant value CB ′ is set based on the amplitude of the oscillation frequency of the VCO 104 and the transmission frequency of the transmitter 4a in advance. If it is too large, it takes time to retune, and if it is small, the received wave signal may be completely lost depending on the magnitude of the drift or the like.
[0054]
Steps S110 to S124 for executing re-tuning are performed in the same procedure as steps S70 to S74. That is, in step S110, the counter 202 starts counting in the counting direction at the tuning completion time (time T3) from the counter C5 returned by the constant value CB '.
[0055]
In step S120, it is determined whether or not the output of the comparator 200, which is a comparison output between the RSSI voltage VRSSI and the reference voltage 2, is “L”. If it is not “L”, scanning (step S110) is continued, and scanning start time (time) When the elapsed time from T5) exceeds the reference operation time TW, this control routine is terminated (step S122) and the sleep period is entered again.
[0056]
If the output of the comparator 200 is “L” in step S120, the process proceeds to step S123, and it is determined whether or not the current time T has exceeded the standby time TH2 from the tuning time T6 of the received wave signal. If the elapsed time from the tuning time T6 does not exceed the waiting time TH2 in step S123, the process proceeds to step S124, and the current counter C is counted from the counter C2 at the start of scanning to the counter value 2CB corresponding to the bandwidth BW (W) of the wideband BPF 105W. If it does not exceed, it returns to step S120. If the count change from the counter C5 at the start of scanning exceeds 2 CB in step S124, it is no longer recognized as a received wave signal to be retuned, and the process returns to step S10, where reference voltage 1, clock 1, The search for the received wave signal is performed again with the setting of the broadband BPF 105W.
[0057]
If the elapsed time from the tuning time T6 exceeds the standby time TH2 in step S123, the process proceeds to step S80, and the code is read again from the time T7 after the standby time TH2 from the tuning time T6.
[0058]
Thus, according to the present embodiment, in the received wave search control, the wideband intermediate frequency filter 105W can be used to search at high speed without losing the received wave detection signal. In the tuning control, since the low scanning speed and the narrow band BPF 105N are used, the tuning can be accurately performed near the center frequency of the received wave signal, and since the narrow band BPF 105N is used, the S / N is improved. Even a weak radio wave can be received.
[0059]
Further, when the control logic 201 shifts to the sleep period in steps S32, S72, and S122, the counter C of the counter 202 at that time, that is, the final value of the oscillation frequency of the VCO 104 during the operation period is stored in the built-in memory. . When the wake-up is performed next time, the stored counter value is set as the initial value of the counter C, and the following effects are obtained.
[0060]
FIG. 3 shows an operation in a situation where there are many unnecessary radio waves such as noise radio waves. The radio wave is transmitted from the transmitter 4a by operating the switch 400 of the transmitter 4a, and the reception frequency is the radio wave from the transmitter 4a. In order to tune to, it is necessary to scan the oscillation frequency of the VCO 104 up to f3 (318.895 MHz). The scanning of the oscillation frequency of the VCO 104 starts from a low frequency. Since the unnecessary radio wave is felt, the RSSI voltage VRSSI is increased by the unnecessary radio wave and the oscillation frequency is locked. However, since the ID code is not recognized from the unnecessary radio wave, scanning is started again. If there are many unnecessary radio waves, such false detections increase, and the time during which the oscillation frequency of the VCO 104 is locked due to the presence of unnecessary radio waves increases. As a result, the oscillation frequency of the VCO 104 does not reach f3 as well as scanning from the upper limit to the lower limit of the variable frequency range of the VCO 104 within the reference operating time TW.
[0061]
Accordingly, if scanning is started from the lowest frequency every time the wake-up is performed, it may be difficult to tune to the transmission radio wave from the transmitter 4a.
[0062]
In the present embodiment, in the wakeup after sleep, the initial value of the counter 202 is set to the final value of the counter C before sleep, and scanning is performed substantially continuously across the sleep period. Even if it cannot be tuned in one operation period, the oscillation frequency of the VCO 104 can be locked to f3 in the operation period after the sleep period (time T1), and thereafter, tuning can be performed in the same manner as the operation in FIG.
[0063]
Note that the initial value of the counter C in the wake-up after sleep is not set strictly to the last counter before sleep, but is a little counter in consideration of the drift of the transmission frequency of the transmitter 4a and the oscillation frequency of the VCO 104. C may be set back. That is, as in steps S50 to S52 in FIG. 4, it is determined whether or not the last counter before sleep is up. If it is up, the counter is decremented. If it is down, the counter is decremented. If it is down, the counter is incremented. .
[0064]
Further, when the influence of unnecessary radio waves such as noise radio waves is small, it is not necessary to provide a standby time after locking the oscillation frequency of the VCO 104 and may be omitted.
[0065]
Further, the control voltage of the VCO 104 is an isosceles triangular wave, but is not necessarily limited to this, and may be any one that can change the oscillation frequency within a predetermined range, such as a sawtooth wave.
[0066]
(Second Embodiment)
FIG. 6 shows the configuration of the scanning circuit of the receiver according to the second embodiment of the present invention. The receiver of this embodiment is the same as that of the first embodiment except that the scanning circuit is changed to the configuration shown in FIG. 6, and the difference from the first embodiment will be mainly described. In addition, the same number is attached | subjected about the part which carries out substantially the same operation | movement as FIG. The scanning circuit 2A of the present embodiment is configured such that the reference voltage defining the step voltage per bit of the DA converter 203 is input from the two reference voltage generation units 211 and 212 via the changeover switch 210. The reference voltage generators 211 and 212 generate two different reference voltages 1 and 2 that are high and low.
[0067]
The control logic 201A constitutes the sweep control means 2aa together with the comparator 200, controls the changeover switch 210 together with the changeover switches 204 and 105S (see FIG. 1), and switches to the high reference voltage 1 in the received wave search control to the VCO 104. In the tuning control, the control voltage is switched to the low reference voltage 2 and the control voltage change speed is lowered.
[0068]
In this embodiment, since the scanning speed is switched by switching the reference voltage of the DA converter 203, the oscillation frequency of the VCO 104 changes more stepwise at wider frequency intervals than in the first embodiment. Will go. The bandwidth of the wideband BPF 105W is set to be approximately the frequency interval, that is, slightly larger than the frequency interval.
[0069]
With this configuration, the scanning speed of the oscillation frequency of the VCO 104 is switched, and the received wave search control for searching the received wave signal at a high speed by the broadband BPF 105W and the tuning control for tuning at a low speed at the narrow band BPF 105N are performed when the received wave signal is detected. .
[0070]
FIG. 7 shows the frequency range where the received wave signal exists and the frequency range where the passbands of the BPFs 105W and 105N exist. (A) is when the received wave search control is performed, (B) is when the received wave is detected, C) is the one during tuning control. In the reception wave search, since the broadband BPF 105W is used, the reception wave signal can be searched for a wide frequency range at a time. When the counter 202 counts up / down, the frequency band where the pass band of the BPF 105W exists is sequentially shifted to the adjacent frequency band. That is, if scanning is increasing, for example, the frequency band “2” in the figure is shifted to the frequency band “4” where the received wave signal exists through the frequency band “3”. If it is descending, it turns back at the lower limit frequency for scanning and shifts to the frequency range “4”. In any case, since the frequency interval at which the frequency shifts is large, the frequency range in which the received wave signal exists is reached in a very short time (FIG. 7B).
[0071]
In the tuning control, the reference voltage of the DA converter 203 is switched to the reference voltage 2 and scanned at a small frequency interval. The oscillation frequency at the start of the tuning control is set to the end of the frequency band where the pass band of the wideband BPF 105W exists, that is, a frequency that is half the bandwidth of the wideband BPF 105W from the current oscillation frequency. The control logic 201 performs this by converting the returned frequency into a count value corresponding to the reference voltage 2 and setting the counter 202 to this count value.
[0072]
As described above, similarly to the first embodiment, by performing scanning from the end of the frequency band where the passband of the wideband BPF 105W exists, the scanning range of the tuning control is substantially within the passband of the wideband BPF 105W.
[0073]
Scanning is performed at a small frequency interval and at a low scanning speed by making the reference voltage of the DA converter 203 low. Since the narrow band BPF 105N is used, the tuning accuracy is improved, and the S / N is improved so that even a weak radio wave can be received ((C) in FIG. 7).
[0074]
In addition, although each said embodiment was applied to the keyless entry control system using FM radio wave, it can be applied to what used other radio wave formats, such as an amplitude modulation radio wave.
[0075]
(Third embodiment)
In each of the above embodiments, the tuning accuracy and reception sensitivity are improved by narrowing the bandwidth of the second BPF during tuning control. As is known from FIG. 7, the FM radio wave has a double-headed frequency spectrum. Therefore, there is a possibility that any peak shifted from the center frequency may be detected, and there is a limit to narrowing the band. In addition, when the RSSI voltage VRSSI is saturated due to the strong electric field, it may be difficult to accurately tune the RSSI voltage. The present embodiment provides a receiver in which this point is improved.
[0076]
FIG. 8 shows a configuration of a keyless entry control system to which a keyless entry receiver according to the third embodiment of the present invention is applied. The keyless entry receiver of this embodiment is the same as the first embodiment except that the second BPF has a single configuration and the scanning circuit is changed to a different configuration. Explained. In addition, the same number is attached | subjected about the part which carries out substantially the same operation | movement as FIG.
[0077]
The receiving unit 1aa of the receiver 1B inputs the intermediate frequency signal from the mixer 103 to the single second BPF 105.
[0078]
The scanning circuit 2 </ b> B receives the detection output (discriminator output) from the detector 107 together with the RSSI voltage VRSSI from the RSSI circuit 111 via the changeover switch 213.
[0079]
The control logic 201B is basically the same as the control logic 201 (FIG. 1) of the first embodiment, and configures the sweep control means 2aaa with the comparator 200, controls the changeover switch 213 with the changeover switches 204 and 205, When the reference voltage 1 and the clock 1 are set, that is, when the received wave search control is performed, the input to the comparator 200 becomes the RSSI voltage VRSSI. When the reference voltage 2 and the clock 2 are set, that is, when the tuning control is performed, the input to the comparator 200 is the discriminator. Output. The control flow executed in the control logic 201B is substantially the same as that shown in FIGS. 4 and 5. However, in step S10, the reference voltage 1, the clock 1, and the RSSI voltage VRSSI are set, and in step S40, the reference flow is set. Voltage 2, clock 2, and discriminator output are set.
[0080]
According to the configuration of the present embodiment, the tuning control is performed based on the discriminator output. The discriminator output is monotonous with respect to the reception frequency and peaks when the reception frequency becomes the center frequency of the reception wave signal. Therefore, as in the case of performing tuning control based on the RSSI voltage VRSSI, There is no risk of detecting such a peak. Therefore, the narrow band of the second BPF 105 can be realized. Further, since the output of the discriminator is basically not saturated even if the RSSI voltage VRSSI is saturated due to a strong electric field, tuning can be achieved.
[0081]
It should be noted that if the discriminator output exceeds the reference voltage, it is not determined as tuning, but the counter value when the discriminator output becomes maximum may be determined as the tuning point.
[0082]
In addition, if a correct received wave signal cannot be obtained in the received wave search and the tuning cannot be performed in the tuning control, the responsiveness of the actual operation such as opening the door is deteriorated with respect to the operation of the switch 400 of the transmitter 4a. In order to prevent this, the control logic 201B may be set as follows. In other words, if tuning control that cannot be tuned is performed a predetermined number of times, for example, twice consecutively, it is determined that tuning is impossible due to saturation of RSSI voltage VRSSI due to a strong electric field, and the comparator 200 is also indiscriminate when the received wave search control is performed. The input of the terminator is input, and the received wave search control is performed based on the output of the discriminator. In this case, since the state of being unable to be tuned does not continue for a long time, the responsiveness to the operation of the switch 400 of the transmitter 4a can be ensured.
[0083]
(Fourth embodiment)
In the third embodiment, the discriminator output is used in tuning control and reception wave search control. However, since the discriminator output includes a modulation signal, the output may not always be constant. In such a case, the transmitter 4a (see FIG. 8) is preferably configured as follows. That is, when a code signal corresponding to the operation of the switch 400 is input to the oscillating unit 403, a carrier wave that is an unmodulated signal is transmitted from the oscillating unit 403 for a predetermined time, and then a normal radio wave frequency-modulated by the code signal is transmitted. Constitute. The time for transmitting the carrier wave is set to a time at which the oscillation frequency of the VCO 104 can be sufficiently scanned, and for example, it is desirable to set it to the same level as the reference operation time TW.
[0084]
According to this configuration, while the carrier wave is transmitted from the transmitter 4a, the receiver can scan the predetermined range of the oscillation frequency of the VCO 104 and capture the received wave based on the stable discriminator output. A keyless entry control system capable of performing good communication between the transmitter and the receiver can be constructed.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a keyless entry control system to which a keyless entry receiver according to an embodiment of the present invention is applied.
FIG. 2 is a first time chart for explaining the operation of the keyless entry receiver.
FIG. 3 is a second time chart for explaining the operation of the keyless entry receiver.
FIG. 4 is a first flowchart for explaining the operation of the keyless entry receiver.
FIG. 5 is a second flowchart for explaining the operation of the keyless entry receiver.
FIG. 6 is a partial configuration diagram of a keyless entry receiver according to another embodiment of the present invention.
FIGS. 7A, 7B, and 7C are first, second, and third schematic diagrams illustrating the operation of the keyless entry receiver, respectively.
FIG. 8 is an overall configuration diagram of a keyless entry control siltem to which a keyless entry receiver according to still another embodiment of the present invention is applied.
FIG. 9 is an overall configuration diagram of a keyless entry control system having a conventional keyless entry receiver.
[Explanation of symbols]
1,1B Keyless entry receiver
1a, 1aa receiver
103 mixer
104 VCO (local oscillator)
105W, 105N, 105 Second band pass filter (intermediate frequency filter)
105S changeover switch (bandwidth changeover means)
111 RSSI circuit (reception signal strength detection means)
1b Control unit
2,2A, 2B scanning circuit
2a, 2aa, 2aaa Sweep control means
200 comparator
201, 201A, 201B Control logic
2b sweeping means
202 counter
203 DA converter
3 Body computer (vehicle control unit)
4 key
4a transmitter
400 switches

Claims (6)

It has a superheterodyne receiver that inputs the intermediate frequency signal between the received wave signal and the local oscillator signal of the local oscillator to the intermediate frequency filter, and the radio wave modulated by the code signal and transmitted from the transmitter In a keyless entry receiver that receives and demodulates a code signal and outputs a control signal corresponding to the code signal to the vehicle control unit, the intermediate frequency filter includes a narrow band intermediate frequency filter and a wide band intermediate frequency. And a bandwidth switching means for switching the intermediate frequency filter to one of them, a sweep means for controlling the local oscillator to sweep the oscillation frequency of the local oscillator within a predetermined range, and reception for detecting the received signal strength A signal strength detecting means; and a sweep control means for controlling the sweep means and the bandwidth switching means. The control means includes a reception wave search control for searching the reception wave signal based on the reception signal strength detected by the reception signal strength detection means with a wide band of the intermediate frequency filter, and a narrow band when the reception wave signal is detected. The keyless entry is characterized in that the tuning of the received wave signal is determined based on the received signal strength, and the tuning control is performed to stop the sweep of the oscillation frequency at the sweep point determined to be tuned. Receiving machine. 2. The keyless entry receiver according to claim 1, wherein the sweeping means is configured such that the oscillation frequency of the local oscillator is swept in a stepped manner at a predetermined frequency interval, and the frequency interval is switchable. The control means sweeps the oscillation frequency by increasing the frequency interval in the received wave search control, and decreases the frequency interval in the tuning control, and the oscillation frequency is a wide band centering on the oscillation frequency when the received wave signal is detected. A keyless entry receiver that is set to sweep over a range that includes the bandwidth of the intermediate frequency filter, and that the bandwidth of the broadband intermediate frequency filter is set to a frequency interval in a substantially received wave search control. It has a superheterodyne receiver that inputs the intermediate frequency signal of the received wave signal and the local oscillator signal of the local oscillator to the intermediate frequency filter, and the radio wave that is frequency-modulated by the code signal and transmitted from the transmitter In a keyless entry receiver that receives and demodulates the code signal and outputs a control signal corresponding to the code signal to the vehicle control unit, the local oscillator is controlled to sweep the oscillation frequency of the local oscillator within a predetermined range. And a sweep control means for controlling the sweep means, wherein the sweep control means is adjusted to the received signal strength detected by the received signal strength detection means. Received wave search control based on the received wave signal, and when the received wave signal is detected, the tuning of the received wave signal is determined based on the detected output intensity. Keyless entry receiver, characterized in that set to perform a tuning control to stop at sweep point is determined to tune the sweep of the oscillation frequency. 4. The keyless entry receiver according to claim 3, wherein the sweep control means detects saturation of the received signal intensity, and the received wave search control is changed from a received wave signal search based on the received signal intensity to a detected output intensity. Keyless entry receiver set to switch to search for received wave signal based. 5. The keyless entry receiver according to claim 4, wherein the received signal strength is determined to be saturated when the tuning control that does not tune the received wave signal is continued a predetermined number of times. 6. A transmitter for transmitting radio waves frequency-modulated by a code signal corresponding to a switch operation, wherein the transmitter is configured to transmit unmodulated radio waves prior to transmission of the frequency-modulated radio waves. A keyless entry control system comprising any one of the keyless entry receivers.

Images