JP4298027B2 - Keyless entry receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a keyless entry receiver, and more particularly to improvement of reception 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. 15 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 possessed by the driver, and a switch (door lock, door unlock, trunk open, panic) 400 is shown. 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 the code signal as a modulation signal and transmitted from the antenna 404. 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 band pass filter (BPF) 505, and an intermediate frequency (IF) signal of 455 kHz is passed through. The IF signal is amplified by an IF amplifier 506, and then the digitized code signal is demodulated by a detection circuit 507, a phase shifter 508, a low-pass filter (LPF) 509, and a waveform shaping circuit 510.
[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.
[0008]
[Means for Solving the Problems]
  In the invention according to claim 1, the keyless entry receiver comprises:Receive radio waves from the transmitter that transmits the signal modulated by the code signal, and thisHaving a superheterodyne receiver that inputs an intermediate frequency signal of a received wave signal and a local oscillation signal of a local oscillator to an intermediate frequency filter;From the received wave signalThe code signal is demodulated and a control signal corresponding to the code signal is output to the vehicle control unit. Further, it comprises 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. .
  In this basic configuration,The sweep control means includes a received signal intensity detected by the received signal intensity detecting means.When exceeds the tuning reference valueTuning received signalJudgingThe tuning control is set to stop the sweep of the oscillation frequency.Further, the sweep means is configured so that the sweep speed can be switched, and the sweep control means performs reception wave search control for searching the reception wave signal at a high sweep speed, and when the reception wave signal is detected, The tuning control is set to be performed at a low sweep speed.
[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.
  Further, whether or not the reception frequency is tuned to the reception wave signal can be easily determined by binary comparison between the reception signal intensity and the tuning reference value. At this time, the time required to complete the tuning can be shortened by increasing the sweep speed until the received wave signal is detected. In the above tuning control, the received signal intensity detecting means is reduced by reducing the sweep speed. It is possible to tune the received wave signal with high accuracy while suppressing the influence of response delay.
[0010]
  In invention of Claim 2,The local oscillator of the receiver uses an oscillator that is less stable than a crystal oscillator..
[0012]
  In invention of Claim 3,The transmitter includes an oscillating unit that generates a signal modulated by a code signal, and the oscillating unit uses an oscillator that is less stable than a crystal oscillator..
[0014]
According to a fourth aspect of the present invention, the sweep control means temporarily stops the sweep of the oscillation frequency of the local oscillator before shifting from the received wave search control to the tuning control, and receives it within a preset predetermined time. If the wave signal is lost, the setting is made to return to the received wave search control.
[0015]
This avoids the time wasted of demodulating temporarily generated noise radio waves, and shortens the time until the received wave signal is tuned.
[0016]
In the invention according to claim 5, the sweep control means is configured to complete the search when the received signal strength detected by the received signal strength detecting means exceeds a search reference value in the received wave search control, and to perform the tuning. In the control, when the received signal strength detected by the received signal strength detecting means exceeds the tuning reference value, it is determined that the tuning is performed, and the sweep is set to be stopped. The search reference value is set to a value lower than the tuning reference value.
[0017]
After the received wave search control, the received signal is detected by comparing the received signal strength with the tuning reference value that is higher than the search reference value, so the received frequency is precisely tuned to the center frequency at which the received wave signal peaks. Can do.
[0018]
  In invention of Claim 6,In the basic configuration of the first aspect of the present invention, the sweep control means determines that the received wave signal is tuned when the received signal intensity detected by the received signal intensity detecting means exceeds the tuning reference value, and determines the oscillation frequency. Set to perform tuning control to stop the sweep. further,The sweep control means performs a received wave search control for searching the received wave signal at a high sweep speed. When the received wave signal is detected, the sweep is stopped, and the received wave signal isIs not detectedlossState andThen, the sweep speed is set to be low, the sweep direction is reversed, and the tuning control is performed. In addition, the sweep speed in the received wave search control is set to a value that causes the loss of the received wave signal due to the response delay of the received signal strength detecting means, and the sweep speed in the tuning control is received by the response delay of the received signal strength detecting means. Set to a value that does not cause wave signal loss.
[0019]
The sweeping of the oscillation frequency of the local oscillator in the reception wave search control is stopped at a point where the reception wave signal tuning point is slightly passed due to a response delay of the reception signal intensity detection means. In the tuning control, the signal is reversed from the passing point and swept toward the tuning point at a low speed, and the tuning is performed with high accuracy. In the reception wave search control, a value that causes loss of the reception wave signal due to a response delay of the reception signal intensity detection means is set, so that the time until tuning of the reception wave signal can be shortened.
[0020]
  In invention of Claim 7,In the basic configuration of the first aspect of the present invention, the sweep control means determines that the received wave signal is tuned when the received signal intensity detected by the received signal intensity detecting means exceeds the tuning reference value, and determines the oscillation frequency. Set to perform tuning control to stop the sweep. further,When the reception control signal is tuned to the reception wave signal, the sweep control unit stops the sweep of the oscillation frequency and sweeps the oscillation frequency of the local oscillator to a preset value, the oscillation frequency when the reception wave signal is detected. If the direction is an ascending direction, subtraction is performed, and if the oscillation frequency sweep direction is a descending direction, correction is performed so as to perform addition.
[0021]
Such correction eliminates the tuning error due to the response delay of the received signal strength detecting means, and improves the tuning accuracy.
[0022]
According to an eighth aspect of the invention, there is provided an intermittent operation control means for intermittently operating the receiving unit so as to alternately repeat an operation period in which the receiving unit operates and a sleep period in which the receiving unit stops operating. The sweep control means stores the final value of the oscillation frequency of the local oscillator in the operation period, and sets the initial value of the oscillation frequency of the local oscillator in the next operation period as the final value.
[0023]
Even if the reception signal intensity detection means erroneously detects noise radio waves and the above sweep is frequently stopped and the sweep within the predetermined range is not performed within one operation period, the sweep is continuously performed across the sleep period. . Thus, even in an environment with a lot of noisy radio waves, sweeping is performed within a predetermined range, and radio waves from the transmitter can be captured.
[0024]
  In invention of Claim 9,In the basic configuration of the first aspect of the invention, the sweep control means detects the tuning of the received signal based on the received signal intensity detected by the received signal intensity detecting means, and when tuned, the sweep of the oscillation frequency is performed. Set the tuning control to stop. further,The sweep means is configured so that the sweep range can be switched, and the sweep control means is set to perform search control for searching for a received wave signal over a wide sweep range prior to tuning control. In the tuning control, the oscillation frequency of the local oscillator is swept a plurality of times within a narrower range than the search control including the detection point of the received wave signal in the search control, and the average value of the oscillation frequencies in the plurality of sweeps is calculated. The tuning point.
[0025]
In the tuning control, the tuning accuracy is further improved because the tuning point is obtained by averaging by plural oscillation frequency sweeps. In addition, the search control is performed prior to the tuning control to substantially specify the tuning point and the sweep range in the tuning control is narrowed, so that the time until the tuning is completed is not prolonged.
[0026]
According to a tenth aspect of the present invention, the sweep means is configured such that the sweep speed can be switched. When the above-mentioned sweep control means detects a received wave signal, it performs multiple times while narrowing the search range sequentially so as to search the received wave signal in a narrower range including the detection point at that time, and the sweep speed as the search range becomes narrower Set to switch to low speed.
[0027]
In search control, the search range becomes narrower and the sweep speed gradually decreases. Therefore, when search control is completed, the range in which the tuning point exists is narrowed down. In tuning control, the sweep range is further narrowed until tuning is completed. Time can be further reduced.
[0028]
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.
[0029]
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. The second BPF 105, which is an intermediate frequency filter, has a center frequency of 455 kHz, and is composed of a ceramic filter or the like.
[0030]
The intermediate frequency (IF) signal that has passed through the second BPF 105 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 received wave signal output from the detector 107 further passes through the LPF 109 and the waveform shaping circuit 110 that remove high frequency components, and the code signal is demodulated, and the code signal is input to the control unit 1b.
[0031]
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.
[0032]
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.
[0033]
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 VCO 104 is desired to be adjusted is the minimum variable of the oscillation frequency, and the smaller the bandwidth of the second BPF 105 is, the smaller the frequency is required.
[0034]
The clock frequencies of the clocks 208 and 209 are preferably set to values that are not an integral multiple of 455 kHz, which is the intermediate frequency, so that the clock signal does not enter the second BPF 105. For example, 455 kHz is multiplied by 8.5 and set to 3.9675 MHz.
[0035]
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.
[0036]
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 the received wave signal is tuned. 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.
[0037]
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.
[0038]
The control unit 1b compares the demodulated code signal input from the waveform shaping circuit 110 with a pre-stored ID code, and if it matches, the control signal corresponding to the operation of the switch 400 of the transmitter 4a is sent to the body computer 3 as the vehicle control unit. 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.
[0039]
The control unit 1b, which is an intermittent operation control means, is configured to perform start-up control of the reception unit 1a and the like so that the reception unit 1a performs an intermittent operation in which the operation period and the sleep period are alternately repeated by timer control. To reduce the dark current. Since the counter 202 backs up the memory, it is energized for backup even during the sleep period.
[0040]
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.
[0041]
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.
[0042]
First, a case where there is no radio wave will be described. In the control flow of FIG. 4, the control unit 1b starts when the receiving unit 1a wakes up. 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 selector switches 204 and 205 are switched to set the low voltage reference voltage 1 and the fast clock 1.
[0043]
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.
[0044]
In the mixer 103, the reception 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 second BPF 105 to generate the oscillation signal of the VCO 104 and the intermediate frequency signal of 455 kHz. Only the wave signal passes through the BPF 105. The oscillation frequency of the VCO 104 is scanned within a predetermined range, and the received wave signal is searched.
[0045]
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).
[0046]
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).
[0047]
Next, the operation when a radio wave enters will be described. It is assumed that the driver operates switch 503 of transmitter 4a after the end of the first scanning and a radio wave of 314.35 MHz is transmitted from 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, the output of the comparator 200 becomes “L” (step S30), and the counter 201 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.
[0048]
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 elapses, it is determined that the detected received wave signal is a noise radio wave, and the process proceeds to step S31.
[0049]
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 second BPF 105.
[0050]
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.
[0051]
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 of the second BPF 105. 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 / 2 away from f1. In the illustrated example, f2 is f1 -BW / 2.
[0052]
In the subsequent step S60, scanning is performed from the returned oscillation frequency f2 of the VCO 104 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.
[0053]
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).
[0054]
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, and the current counter C obtains the counter value 2CB corresponding to the bandwidth BW of the second BPF 105 from the counter C2 at the start of scanning. It is determined whether it has exceeded, and if not, the process 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, so the process returns to step S10 to set the reference voltage 1 and clock 1 Repeat the search for the received signal.
[0055]
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.
[0056]
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 1, and the RSSI voltage VRSSI is checked based on the output of the comparator 200.
[0057]
The procedure after step S100 is a procedure for re-tuning the reception frequency out of synchronization. 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 oscillation frequency of the VCO 104 and the magnitude of drift of 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 is completely lost.
[0058]
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 '.
[0059]
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.
[0060]
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 obtains the counter value 2CB corresponding to the bandwidth BW of the second BPF 105 from the counter C5 at the time of starting scanning. It is determined whether or not it exceeds, and if not, the process 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 to return the reference voltage 1 and clock 1 Search the received signal again in the settings.
[0061]
When the elapsed time from the detection time T6 exceeds the standby time TH2 in step S123, the process proceeds to step S80, and the code is read again from time T7 after the standby time TH2 from the detection time T6.
[0062]
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.
[0063]
FIG. 3 shows the 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 changed to the radio wave from the transmitter. In order to tune, the oscillation frequency of the VCO 104 needs to be scanned up to f3 (318.895 MHz). Scanning starts from a low frequency of the oscillation frequency of the VCO 104. 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.
[0064]
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.
[0065]
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, so that scanning is performed substantially continuously across the sleep period, For example, the oscillation frequency of the VCO 104 can be locked to f3 in the operation period after the sleep period even if it cannot be tuned in one operation period (time T1), and thereafter the tuning can be performed in the same manner as the operation of FIG. .
[0066]
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. .
[0067]
In the present embodiment, the scanning circuit is configured to switch the scanning speed by switching clocks having different frequencies. However, as in the scanning circuit 2A of FIG. 6, the step voltage per bit of the DA converter 203 is defined. The reference voltage to be input is input from the two reference voltage generators 211 and 212 via the changeover switch 210, and the reference voltage generators 211 and 212 generate two different reference voltages 1 and 2 that are high and low. You may do it. That is, the control logic 201 controls the changeover switch 210 to switch to the high-voltage side reference voltage 1 in the received wave search control to increase the control voltage change speed, and in the tuning control to switch to the low-voltage side reference voltage 2 for control. Reduce the voltage change rate.
[0068]
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.
[0069]
In addition, before the tuning control for adjusting the oscillation frequency of the VCO 104, the received wave search control for searching the received wave signal at a high speed with the reference voltage 1 and the clock 1 is performed. When the range in which the oscillation frequency of the VCO 104 is changed using a relatively accurate oscillator 4031 of the transmitter 4a or the SAW 1041 of the VCO 104 is narrow, the scanning circuit 2 does not have a changeover switch. A configuration including only a voltage generation unit and a clock may be employed, and only a tuning control may be performed.
[0070]
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.
[0071]
(Second Embodiment)
FIG. 7 shows the configuration of the scanning circuit of the keyless entry receiver according to the second embodiment of the present invention. The keyless entry receiver according to the second embodiment is the same as the first embodiment except that the scanning circuit is changed to the configuration shown in FIG. 7, and the differences 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. In the scanning circuit 2B, the reference voltage, which is the other comparison signal of the comparator 200, is input from a single reference voltage generator 213, and the reference voltage is shared between the received wave search control and the tuning control.
[0072]
Since the RSSI circuit 111 causes a response delay as described above, if the scanning speed of the VCO 104 is increased, the output of the comparator 200 becomes “L” and the oscillation frequency of the VCO 104 is locked. The output of the comparator 200 is inverted to “H” again due to the synchronization deviation due to the response delay. In the reception wave search control, the clock frequency of the clock 1 is set high so that the output of the comparator 200 after the lock is inverted.
[0073]
Further, in the tuning control, in addition to the setting to switch from clock 1 to clock 2 after the output of the comparator 200 is inverted, the count direction is set to down if the oscillation frequency of the VCO 104 in the reception wave search control is locked, and to the locked state. If is down, flip it up.
[0074]
FIG. 8 shows the operation of the receiver 1 with the control logic set as described above, and is a time chart showing the control voltage of the VCO 104 (oscillation frequency of the VCO 104) and the RSSI voltage VRSSI output from the DA converter 203. . At time T3, the transmission radio wave from the transmitter 4a and the oscillation frequency f3 of the VCO 104 capable of generating an intermediate frequency signal are passed. At this time, the RSSI voltage VRSSI does not exceed the reference voltage due to a response delay of the RSSI circuit 111 or the like. At time T8, the RSSI voltage VRSSI exceeds the reference voltage, and the output of the comparator 200 becomes “L”. In response to this, the control logic 201 stops the counter 202 and locks the oscillation frequency of the VCO 104.
[0075]
However, since scanning is performed at a high speed, the synchronization is shifted by scanning from time T3 to time T8, and after time T8, the RSSI voltage VRSSI decreases after taking a peak value. At time T9, the output of the comparator 200 changes to "H". When the output of the comparator 200 changes to "H", the clock 2 is switched to the low frequency here, and the count direction (up / down) is reversed (up to down in the example in the figure), and scanning is performed at a low speed toward f3. To do. When the output of the comparator 200 changes to “L” at time T10, the oscillation frequency of the VCO 104 is locked. This is the tuning control itself from time T2 to time T3 in FIG. 2, and precise tuning is possible.
[0076]
In addition, in the present embodiment, the fact that the tuning is shifted if the scanning of the oscillation frequency of the VCO 104 is made too fast is used in reverse, and the time required for the tuning can be further reduced as compared with the first embodiment.
[0077]
(Third embodiment)
In each of the above embodiments, the RSSI response delay is suppressed by reducing the scanning speed in the tuning control. However, if the speed is too low, there is a limit because the time required for tuning becomes longer. In the configuration of each embodiment described above, an embodiment in which the setting of the control logic 201 is partially changed will be described. In the following description, the reference numerals of the respective parts are attached according to FIG. After the control logic 201 locks the oscillation frequency of the VCO 104 in the tuning control (after the time T3 in FIG. 2 and after the time T10 in FIG. 8), the counter C changes by the delay that the counter C changes due to the response delay of the RSSI circuit 111. It is better to set to correct up or down. That is, it is determined whether or not the counter C is up when the oscillation frequency of the VCO 104 is locked. If it is up, the counter C is lowered, and if it is down, the counter C is raised by the deviation. . With this setting, it is possible to eliminate the tuning deviation caused by the response delay of the RSSI circuit 111.
[0078]
Note that this embodiment is not only a receiver configured to switch the sweep speed as in the first and second embodiments, but also a receiver configured with a single reference voltage and scanning speed compared with the RSSI voltage. Is also applicable.
[0079]
(Fourth embodiment)
FIG. 9 shows the configuration of the scanning circuit of the keyless entry receiver according to the fourth embodiment of the present invention. The keyless entry receiver according to this embodiment is the same as the first embodiment except that the scanning circuit is changed to the configuration shown in FIG. In addition, the same number is attached | subjected about the part which carries out substantially the same operation | movement as FIG. The scanning circuit 2C includes a peak timing detection circuit 214 that receives the RSSI voltage VRSSI, a control logic circuit 201 that constitutes the sweep control means 2a together with the peak timing detection circuit 214, a counter 202, and the like.
[0080]
The peak timing detection circuit 214 is configured to issue an output signal to the control logic circuit 201 at a timing when the RSSI voltage VRSSI reaches a peak. In the control logic circuit 201, the timing at which the RSSI voltage peaks is known. . The control logic circuit 201 controls the counter 202 to control the start and stop of the count, the initial value of the count, and the count speed to control the start and stop of the scanning of the oscillation frequency of the VCO 104, the initial value of the scan, and the scanning speed. ing.
[0081]
FIG. 10 is a timing chart showing the oscillation frequency of the VCO 104 and the control voltage output to the VCO 104, and FIG. 11 is a control flow executed in the control logic 201. In the control flow, steps S210 to S250 are received wave search control, and steps S260 to S310 are tuning control. In step S210, the first scanning is performed. In the first scanning, the oscillation frequency of the VCO 104 is swept in the range of 313.895 MHz-0.3 MHz to 313.895 MHz + 0.3 MHz over a period of 4 msec (first sweep). This sweep range is a range that can follow variations in the transmission frequency of the transmitter 4a. When the RSSI voltage VRSSI takes a peak and there is an output from the peak timing detection circuit 214, the control logic 201 stores the counter value Ca at that time in a register.
[0082]
Next, a second scanning is performed. A value Cb obtained by subtracting the offset value Oa from the counter value Ca is loaded (step S230), and a second sweep is performed using the counter value Cb as an initial value (step S240). In this sweep, 1/4 of the count range of the first sweep is performed over a period of 4 msec. That is, the sweep speed is 1/4 that of the first sweep. The offset value Oa is set to about ½ of the second sweep range, for example.
[0083]
When the RSSI voltage VRSSI takes a peak and there is an output from the peak timing detection circuit 214, the counter value Cc at that time is stored in a register (step S250).
[0084]
Next, the third scanning is performed. A value Cd obtained by subtracting the offset value Ob from the counter value Cc is loaded (step S260), and a third sweep is performed using the counter value Cd as an initial value (step S270). This sweep is performed 16 times in total by repeating step S270 and steps S280 and S290 described later. The sixteen sweeps are performed under the same conditions, and are described as the 3-kth (k = 1 to 16) in the order in which they are performed in the following description. Each sweep of the third sweep takes 1/16 of the count range of the first sweep, and thus 1/4 of the count range of the second sweep takes 0.5 msec.
[0085]
When the RSSI voltage VRSSI takes a peak in the third sweep and there is an output from the peak timing detection circuit 214, the counter value Ce1 at that time is stored in the register (step S280). Then, the counter value Cd is loaded again as an initial value (step S290), and steps S270 to S290 are repeated, and from the 3-1st sweep to the 3rd to 3-16th sweep sequentially. Thus, the counter value Cek (k = 1 to 16) when the RSSI voltage VRSSI takes a peak is obtained.
[0086]
When the sweep from the 3-1st to the 3-16th time is completed and the last counter value Ce16 is obtained, the process proceeds to step S300.
[0087]
In step S300, the average of the counter values Cek (k = 1 to 16) stored in the register is calculated and set as Cf. Although this average value Cf is a representative value of the counter value at the time of peak timing detection, since it includes a response delay of the RSSI circuit 111, etc., an offset value Oc corresponding to this response delay is subtracted from the average value Cf to obtain Cg. The counter value Cg is loaded to fix the oscillation frequency of the VCO 104.
[0088]
If there is no output from the peak timing detection circuit 214 during the sweep, the sweep is repeated in the same sweep range until the sleep timing comes in step S210 as in the above embodiments, and in steps S240 and S270, it is a noise radio wave. Determine and start again from step S210.
[0089]
12 and 13 show the results of investigation by the inventors on the relationship between the sweep time and the peak frequency. The sweep range is fixed, and the longer the sweep time, the slower the sweep speed. Further, in the figure, the variation is shown together with the average of the peak frequency at each sweep time, and the variation is expressed by the standard deviation σ and the maximum value and the minimum value.
[0090]
As can be seen from FIG. 12, the variation in the peak frequency becomes smaller as the sweep time becomes longer. In the present embodiment, as described above, the second sweep (step S240) in the low speed narrow range is performed following the first sweep in the wide high speed range (step S210), and the following effects are obtained. In the first sweep, although the error is large, the peak frequency can be substantially specified (count value Cb) by scanning the first sweep range covering the transmission frequency deviation of the transmitter 4 in a short time. In the second sweep, since the peak frequency is substantially specified in the first sweep, the sweep range can be reduced as described above, and the tuning frequency can be further narrowed down by reducing the sweep speed.
[0091]
FIG. 13 shows experimental results in a region where the sweep time is longer than that of the data of FIG. Even if the sweep time is made too long, the variation of the peak frequency does not become small, and cannot be within the range of 10 kHz which is the target range (maximum value−minimum value) of the inventors.
[0092]
In the present embodiment, by performing the third sweep (step S270), the variation in the peak frequency can be within a range of 10 kHz. FIG. 14 shows the results of investigation by the inventors on the relationship between the average value of peak frequencies and the number of sweeps (average number in the figure) when a predetermined number of sweeps are performed as in the third sweep. In the figure, the variation is shown together with the average of the peak frequency average values at each average number of times, and the variation is expressed by the standard deviation σ and the maximum and minimum values. The variation of the average value of the peak frequency is reduced according to the average number of times. In the illustrated example, when the average number is 8 times or more, the variation of the average peak frequency value is in the range of 10 kHz as (maximum value−minimum value).
[0093]
Therefore, the tuning accuracy can be improved by performing the third sweep as described above and fixing the oscillation frequency of the VCO 104 at the count value Cg. In addition, in this embodiment, the tuning frequency is specified to some extent by performing steps S210 to S250 before performing the third sweep. Therefore, the sweep range is considerably narrow in the third sweep, and a plurality of times in the third sweep. Even if the sweep is performed, it does not take a long time to complete the tuning.
[0094]
By performing such control, highly accurate scanning can be performed in a short time.
[0095]
In this embodiment, in the received wave search control, the VCO oscillation frequency sweep is performed step by step while gradually reducing the low-speed narrowing range. However, the number of times is not necessarily limited to this, and Depending on the stability of the transmission frequency, the oscillation frequency of the VCO, etc. (drift amount, variation), it may be increased to 3 times or more, and conversely, it may be decreased to 1 time.
[0096]
In this embodiment, the sweep speed of the third sweep is faster than the sweep speed of the second sweep, but may be slower. In this case, as is known from FIG. 12, the variation in the average peak frequency value becomes smaller as the sweep speed is slower, so the average number of times can be reduced accordingly.
[0097]
As described above, when the configuration of the present embodiment is adopted, the number of sweeps, the sweep range, and the sweep speed in the reception wave search control and the tuning control are such that the tuning is completed in a short time while satisfying the target tuning accuracy. It is better to optimize in advance by experiments or the like. In this case, since the target range of the tuning accuracy is 10 kHz in this embodiment, it is necessary to set the number of sweeps of the third sweep to 8 or more, but of course the number of sweeps varies depending on the target range.
[0098]
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 (AM) radio wave.
[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 a first 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 showing a second embodiment of the present invention.
FIG. 7 is a partial configuration diagram of a keyless entry receiver showing a third embodiment of the present invention.
FIG. 8 is a graph for explaining the operation of the keyless entry receiver according to the third embodiment of the present invention.
FIG. 9 is a partial configuration diagram of a keyless entry receiver showing a fourth embodiment of the present invention.
FIG. 10 is a time chart for explaining the operation of the keyless entry receiver.
FIG. 11 is a flowchart for explaining the operation of the keyless entry receiver.
FIG. 12 is a first graph illustrating the operation of the keyless entry receiver.
FIG. 13 is a second graph illustrating the operation of the keyless entry receiver.
FIG. 14 is a third graph for explaining the operation of the keyless entry receiver.
FIG. 15 is an overall configuration diagram of a keyless entry control system having a conventional keyless entry receiver.
[Explanation of symbols]
1 Keyless entry receiver
1a Receiver
103 mixer
104 VCO (local oscillator)
105 Second bandpass filter (intermediate frequency filter)
111 RSSI circuit (reception signal strength detection means)
1b Control unit (intermittent operation control means)
2,2A, 2B scanning circuit
2a Sweep control means
200 comparator
201 Control logic
2b sweeping means
202 counter
203 DA converter
214 Peak timing detection circuit
3 Body computer (vehicle control unit)
4 key
4a transmitter

Claims (10)

A superheterodyne system that receives radio waves from a transmitter that transmits a signal modulated by a code signal and inputs an intermediate frequency signal between the received wave signal and a local oscillation signal of a local oscillator to an intermediate frequency filter. A keyless entry receiver that demodulates a code signal from the received wave signal and outputs a control signal corresponding to the code signal to the vehicle control unit by controlling the local oscillator Sweeping means for sweeping the oscillation frequency within a predetermined range, received signal strength detecting means for detecting the received signal strength, and sweep control means for controlling the sweeping means, the sweep control means being used for detecting received signal strength. received signal strength detected by means determines the tuning of the received wave signal exceeds the tuning reference value a tuning control to stop the sweeping of the oscillation frequency Set Migihitsuji, and the sweeping means, freely constitute switching the sweep speed, the sweeping control means, performs reception wave search control to search the received wave signal sweep rate in the high speed, the reception wave signal A keyless entry receiver configured to perform the tuning control at a low sweep speed when detected . The keyless entry receiver according to claim 1, wherein the local oscillator of the receiving unit uses an oscillator having a lower stability than a crystal oscillator . 3. The keyless entry receiver according to claim 1, wherein the transmitter includes an oscillating unit that generates a signal modulated by a code signal, and the oscillating unit is less stable than a crystal oscillator. keyless entry receiver you are using. In claims 1 to 3 keyless entry receiver according any one, the sweep control means, the sweep of the oscillation frequency of the local oscillator before migrating to the tuning control from the received wave search control temporarily stops receiving It continues to search for signals, keyless entry receiver received wave signal is set to return to the ing and loss state not detected the reception wave search control the preset within a predetermined time. The keyless entry receiver according to any one of claims 1 to 4, wherein the sweep control means is configured such that when the received signal strength detected by the received signal strength detection means exceeds a search reference value in the received wave search control, The search is completed, and in the tuning control, when the received signal strength detected by the received signal strength detection means exceeds the tuning reference value, the tuning is determined, and the sweep is set to stop, and the search reference value is set. A keyless entry receiver with a value lower than the tuning reference value. A superheterodyne system that receives radio waves from a transmitter that transmits a signal modulated by a code signal and inputs an intermediate frequency signal between the received wave signal and a local oscillation signal of a local oscillator to an intermediate frequency filter. A keyless entry receiver that demodulates a code signal from the received wave signal and outputs a control signal corresponding to the code signal to the vehicle control unit by controlling the local oscillator Sweeping means for sweeping the oscillation frequency within a predetermined range, received signal strength detecting means for detecting the received signal strength, and sweep control means for controlling the sweeping means, the sweep control means being used for detecting received signal strength. If the received signal intensity detected by the means exceeds the tuning reference value, the tuning of the received wave signal is judged to be tuned and the sweep of the oscillation frequency is stopped. Set Migihitsuji, and the sweep control means, the sweep rate in the high speed performs reception wave search control to search the received wave signal, the received wave signal is detected to stop the sweeping, the reception wave signal reversing the sweep direction with the do that the undetected loss condition the sweep rate to the low speed set to perform the tuning control, and the sweep rate in the reception wave search control, the response delay of the received signal strength detecting means A keyless entry receiver characterized in that a reception wave signal loss is set to a value and a sweep speed in tuning control is set to a value that does not cause a reception wave signal loss due to a response delay of the reception signal strength detection means. . A superheterodyne system that receives radio waves from a transmitter that transmits a signal modulated by a code signal and inputs an intermediate frequency signal between the received wave signal and a local oscillation signal of a local oscillator to an intermediate frequency filter. A keyless entry receiver that demodulates a code signal from the received wave signal and outputs a control signal corresponding to the code signal to the vehicle control unit by controlling the local oscillator Sweeping means for sweeping the oscillation frequency within a predetermined range, received signal strength detecting means for detecting the received signal strength, and sweep control means for controlling the sweeping means, the sweep control means being used for detecting received signal strength. If the received signal intensity detected by the means exceeds the tuning reference value, the tuning of the received wave signal is judged to be tuned and the sweep of the oscillation frequency is stopped. Set Migihitsuji, and the sweep control means, when the receiving frequency is tuned to the receiving wave signal, both to stop the sweeping of the oscillation frequency, the value of the oscillation frequency of the local oscillator, set in advance, the received wave signal A keyless entry receiver configured to perform correction for subtraction when the oscillation frequency sweep direction at the time of detection is an upward direction and for addition when the oscillation frequency sweep direction is a downward direction.   8. The keyless entry receiver according to claim 1, wherein the receiving unit is intermittently operated so as to alternately repeat an operation period in which the receiving unit operates and a sleep period in which the receiving unit stops operating. Control means, and the sweep control means stores a final value of the oscillation frequency of the local oscillator in the operation period, and an initial value of the oscillation frequency of the local oscillator in the next operation period is defined as the final value. Keyless entry receiver set to do. A superheterodyne system that receives radio waves from a transmitter that transmits a signal modulated by a code signal and inputs an intermediate frequency signal between the received wave signal and a local oscillation signal of a local oscillator to an intermediate frequency filter. A keyless entry receiver that demodulates a code signal from the received wave signal and outputs a control signal corresponding to the code signal to the vehicle control unit by controlling the local oscillator Sweeping means for sweeping the oscillation frequency within a predetermined range, received signal strength detecting means for detecting the received signal strength, and sweep control means for controlling the sweeping means, the sweep control means being used for detecting received signal strength. The tuning of the received signal is detected based on the received signal intensity detected by the means, and the tuning control is performed to stop the sweep of the oscillation frequency when the tuning is performed. And sea urchin set, and the sweep means, and freely configured switches the sweep range, said sweep control means, prior to the tuning control, it performs a search control for searching the received wave signal sweep range in the wide range, the tuning control Then, the oscillation frequency of the local oscillator is swept several times in a narrower range than the search control including the detection point of the received wave signal in the search control, and the average value of the oscillation frequencies in the multiple sweeps is used as the tuning point. A keyless entry receiver characterized by that .   10. The keyless entry receiver according to claim 9, wherein the sweep means is configured to be able to switch a sweep speed, and when the sweep control means detects a received wave signal, the received wave is received in a narrower range including the detection point at that time. A keyless entry receiver configured to perform multiple times while narrowing the search range sequentially so as to search for a signal, and set the sweep speed to be switched to a lower speed as the search range becomes narrower.

Images