JP5460524B2 - Digital receiver - Google Patents

Description

  The present invention relates to a digital receiver.

  2. Description of the Related Art Conventionally, there has been known a digital receiver that receives a desired wave signal (wireless signal) modulated from a portable device possessed by a user and demodulates the received signal into a digital signal. The demodulated digital signal is output to a control target such as a vehicle. Thereby, the contents of the desired wave signal are recognized in the controlled object. Here, the digital receiving apparatus receives not only a desired wave signal from the portable device but also a noise signal. The desired signal may not be properly recognized by the noise signal, and communication between the portable device and the control target may be hindered. Various countermeasures have been taken in the digital receiver for such noise signals.

  For example, the digital reception device disclosed in Patent Document 1 includes an adaptive filter, and the filter coefficient is set so that the adaptive filter removes the noise signal according to the received noise signal. Specifically, as illustrated in FIG. 4, the digital reception device includes a signal determination unit 101 that determines whether the received signal is a desired wave signal or a noise signal, in addition to the adaptive filter 102. . The signal determination unit 101 determines whether or not the received signal is the desired wave signal in a standby state waiting for reception of the desired wave signal, and outputs the determination result to the filter control unit 103.

  When the filter control unit 103 recognizes that the signal is not a desired wave signal, that is, a noise signal based on the determination result from the signal determination unit 101, the filter control unit 103 calculates a filter coefficient for removing the noise signal and adapts to the calculated filter coefficient. The filter 102 is updated. Thereby, even if the frequency of the noise signal changes, the noise signal can be removed by setting the adaptive filter 102 to a filter coefficient corresponding to the noise signal.

  Here, when a noise signal in the same frequency band as the desired wave signal is received, the filter control unit 103 removes the noise signal by updating the filter coefficient as described above. However, in this case, since the noise signal and the desired wave signal are in the same frequency band, not only the noise signal but also the desired wave signal is removed.

  In order to solve such a problem, for example, the following configurations have been studied. That is, as shown in FIG. 4, the digital reception device includes a notch frequency determination unit 104. The notch frequency determination unit 104 calculates a notch frequency based on the calculation result of the filter coefficient from the filter control unit 103 and outputs the calculation result to the filter control unit 103. Here, the notch frequency is a frequency at which the attenuation amount of the signal level is maximum in the adaptive filter 102 to which the filter coefficient is applied. The filter control unit 103 recognizes the notch frequency based on the calculation result from the notch frequency determination unit 104.

  The filter control unit 103 includes a nonvolatile memory 103a, and the center frequency of the desired wave signal is stored in advance in the memory 103a. The filter control unit 103 collates the notch frequency and the center frequency of the desired wave signal. When this collation is established, the filter control unit 103 resets the filter coefficient through the adaptive filter 102, assuming that a filter that removes even the desired wave signal is formed. When the filter coefficient is reset, no noise signal is removed, but at least the desired wave signal is not removed. Therefore, according to this configuration, it is possible to suppress the removal of the desired wave signal through the update of the filter coefficient.

  Here, in general, a plurality of portable devices are registered in a control target including a vehicle. Each portable device is designed so that the desired signal from them is transmitted at the same center frequency. However, in practice, the center frequency of the desired wave signal varies among portable devices. Thus, for example, when two portable devices are registered, the memory 103a stores the center frequencies fka and fkb of the desired wave signal corresponding to both portable devices. Then, the notch frequency is compared with the center frequencies fka and fkb stored in the memory 103a.

JP-A-2005-73163

  By the way, even if a plurality of portable devices are registered, the frequency of use thereof varies. For example, it is also conceivable that only the main portable device is used and the sub portable device is stored at home. Even in such a case, the center frequency fkb corresponding to the sub portable device is collated with the notch frequency. If the notch frequency coincides with the center frequency fkb corresponding to the sub portable device, the filter coefficient is reset even though the sub portable device is not used. Thereby, since the noise signal is not removed, it is impossible to temporarily remove the noise signal included in the desired wave signal from the main portable device. As a result, the reception sensitivity of the digital reception device may be reduced, and communication between the vehicle and the control target may not be established.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a digital receiving apparatus capable of appropriately removing a noise signal even if a plurality of portable devices are registered.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
According to the first aspect of the present invention, a desired wave signal transmitted at a different frequency from each of a plurality of portable devices is received, and a non-regular desired wave signal is received in order to remove a noise signal contained in the desired wave signal When it is determined that the normal signal is received, a filter having a stop band for removing the non-normal signal is formed by updating the filter coefficient, and the frequency of each desired wave signal stored in advance is set to the stop band. In the digital receiver that resets a filter coefficient when it is determined that the frequency of each desired wave signal is included in the stop band, a specific mobile device among the plurality of mobile devices is determined. If it is determined that the frequency of use of the device is low, the determination whether the stop band includes the frequency of the desired signal corresponding to the specific portable device is omitted. It is a fact.

  According to this configuration, for a specific portable device that is determined to be less frequently used among a plurality of portable devices, it is determined whether or not the stopband includes the frequency of the desired signal corresponding to the specific portable device. Omitted. Therefore, it is suppressed that the filter coefficient is reset accidentally including the frequency of the desired wave signal corresponding to a specific portable device whose use band is less frequently used, and that the noise signal removal function is canceled. . Thereby, the reception sensitivity of the digital receiver can be maintained even when a plurality of portable devices are registered.

  According to a second aspect of the present invention, in the digital receiving device according to the first aspect, when the number of continuous use of the portable device exceeds a threshold value, it is determined that the frequency of use of portable devices other than the portable device is low. That is the gist.

  According to this configuration, the frequency of use of the portable device is determined based on the number of continuous use of the portable device. Thereby, it is possible to easily determine the frequency of use simply by counting the number of continuous use of the portable device.

  According to a third aspect of the present invention, in the digital receiver according to the first or second aspect, the determination as to whether or not the frequency of each desired wave signal stored in advance is included in the stop band is the block The gist of the present invention is to determine whether or not the notch frequency of the filter that maximizes the attenuation of the signal level in the band matches the center frequency of each desired wave signal stored in advance.

  According to the same configuration, the notch frequency of the filter and the center frequency of each desired wave signal stored in advance coincide with each other in determining whether the stopband includes the frequency of each desired wave signal stored in advance. It is determined whether or not to do so. Then, the determination as to whether or not the center frequency of the desired wave signal corresponding to the portable device determined to be low in use frequency matches the notch frequency of the filter is omitted.

  ADVANTAGE OF THE INVENTION According to this invention, even if a some portable apparatus is registered in a digital receiver, a noise signal can be removed appropriately.

The block diagram of a digital receiver. The frequency characteristic figure of a notch filter. The flowchart which shows the process sequence of a control program. The block diagram of the conventional digital receiver.

  Hereinafter, an embodiment in which a digital receiver according to the present invention is embodied in an electronic key system will be described with reference to FIGS. The digital receiver in this example is mounted on a vehicle and receives a radio signal for requesting locking / unlocking of a vehicle door from an electronic key.

  As shown in FIG. 1, the electronic key 2 includes a nonvolatile memory 2a, and an ID code unique to the electronic key 2 is stored in the memory 2a. The electronic key 2 transmits a radio signal (desired wave signal Sk1) of a predetermined frequency band including an ID code stored in its own memory 2a by a switch operation. In this example, the desired wave signal Sk1 is FSK (Frequency Shift Keying) modulated. The predetermined frequency band is an RF (Radio Frequency) band. Further, in this example, there is a sub electronic key 3 in addition to the master electronic key 2 described above. Similarly to the master electronic key 2, the sub electronic key 3 also transmits a desired wave signal Sk2 including an ID code. Hereinafter, only the master electronic key 2 will be described as a representative unless otherwise specified, but the same applies to the sub electronic key 3.

  The digital receiver 1 demodulates the desired wave signal Sk 1 from the electronic key 2 and outputs it to the vehicle control unit 50. In the vehicle control unit 50, verification of the ID code included in the desired wave signal Sk1 is executed, and when the verification of the ID code is established, the vehicle door is locked and unlocked.

  The digital receiver 1 is intermittently turned on / off, enters a reception operation mode when the power is turned on, and enters a sleep mode when the power is turned off. In the reception operation mode when the power is turned on, there are a standby state in which the desired wave signal Sk1 is received from the electronic key 2 and a reception state in which the desired wave signal Sk1 is received. Therefore, in the standby state, the desired wave signal Sk1 is not input and only the noise signal Sn is received. In the reception state, the noise signal Sn is received together with the desired wave signal Sk1.

Next, the digital receiver 1 will be described in detail.
As illustrated in FIG. 1, the digital reception device 1 includes a reception antenna 10, a preprocessing unit 20, a noise removal unit 30, a demodulation unit 41, and a normal signal determination unit 42.

The receiving antenna 10 receives the desired wave signal Sk 1 transmitted from the electronic key 2 and outputs the received signal to the preprocessing unit 20.
The pre-processing unit 20 frequency-converts the input signal to generate a so-called intermediate frequency signal, which is the difference between the frequency of the signal and the frequency of the local oscillator. Then, the preprocessing unit 20 performs analog / digital conversion on the intermediate frequency signal to generate a baseband signal, and outputs a band-limited signal to the noise removal unit 30.

  The noise removing unit 30 includes a filter unit 31, an adder 32, a filter control unit 33, and a notch frequency determination unit 34. The signal from the preprocessing unit 20 is output to the demodulation unit 41 through the adder 32. The filter unit 31 causes the adder 32 to pass the desired wave signal Sk1 out of the signal S1 before noise removal and remove the noise signal Sn to generate a signal S3 after noise removal. The signal S3 after noise removal is output to the demodulation unit 41, the filter control unit 33, and the normal signal determination unit 42.

  The normal signal determination unit 42 determines whether the signal S3 after noise removal from the adder 32 is the desired signal Sk1, Sk2 or the non-normal signal. The non-regular signal includes not only the noise signal Sn but also a signal that has a relatively strong signal level of the noise signal Sn mixed with the desired wave signals Sk1 and Sk2 and is not recognized as the normal desired wave signals Sk1 and Sk2. The regular signal determination unit 42 outputs the determination result to the filter control unit 33 as a result signal S4.

  The filter control unit 33 monitors the noise removal status through the filter unit 31 based on the signal S3 after noise removal. The filter control unit 33 includes a counter 33b that counts the number of times the electronic keys 2 and 3 are continuously used.

  The filter control unit 33 includes a non-volatile memory 33a, which stores the center frequencies fka and fkb of both desired wave signals Sk1 and Sk2. Here, as described in the background art, and as shown in FIG. 2, the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 are different for the electronic keys 2 and 3, respectively.

  When the filter control unit 33 recognizes that the signal is a non-normal signal through the result signal S <b> 4, the filter control unit 33 calculates a new filter coefficient for removing the non-normal signal, and reflects the calculated filter coefficient in the filter unit 31. Here, it is assumed that the non-regular signal is the noise signal Sn. As a result, as shown in FIG. 2, the filter unit 31 attenuates the signal level in the stop band LF <b> 1 centered on the center frequency fn of the noise signal Sn to zero through the adder 32. Thereby, the noise signal Sn in the stop band LF1 is removed. That is, the filter unit 31 and the adder 32 constitute a notch filter that removes the noise signal Sn in the stop band LF1.

  The frequency at which the attenuation amount in the stop band LF1 is maximum is referred to as a notch frequency fc. In this example, the notch frequency fc takes a median value in the stop band LF1 and coincides with the center frequency fn of the noise signal Sn. As described above, when the filter coefficient, and thus the notch frequency fc (stop band LF1) is updated according to the noise signal Sn, the frequency of the noise signal Sn mixed with the desired wave signal Sk1 varies depending on the surrounding environment. Even if it exists, noise signal Sn can be removed more reliably.

  Further, the filter control unit 33 outputs the calculation result of the filter coefficient to the notch frequency determination unit 34. The notch frequency determination unit 34 calculates the notch frequency fc based on the filter coefficient calculation result, and outputs the calculation result to the filter control unit 33. The filter control unit 33 collates the notch frequency fc based on the calculation result from the notch frequency determination unit 34 with the center frequencies fka and fkb stored in the memory 33a. When the notch frequency fc and the center frequencies fka and fkb stored in the memory 33a do not coincide with each other and the collation is not established, the filter control unit 33 stores the latest filter coefficient calculated this time in the memory 33a. Update the coefficient.

  The filter control unit 33 resets the filter coefficient reflected through the filter unit 31 when it is determined that the notch frequency fc coincides with one of the center frequencies fka and fkb and collation is established. For example, when the notch frequency fc coincides with the center frequency fka, the stop band LF2 is set around the notch frequency fc having the same value as the center frequency fka, as shown by the broken line in FIG. In this case, the center frequency fka of the desired wave signal Sk1 is within the stop band LF2, and even the normal desired wave signal Sk1 may be removed. In this regard, in this example, when the notch frequency fc matches the center frequency fka, the stop band LF2 is erased by resetting the filter coefficient. Thus, although the noise signal Sn is not removed through the notch filter, at least the desired wave signals Sk1 and Sk2 are not removed.

  The center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 stored in the memory 33a are updated when the ID verification of the vehicle control unit 50 is established. Specifically, the vehicle control unit 50 transmits a signal S5 for notifying the filter control unit 33 when the ID code verification is established. Upon receiving the signal S5, the filter control unit 33 compares the center frequencies fka and fkb stored in the memory 33a with the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 received this time. When collation is not established, the filter control unit 33 updates the center frequencies fka and fkb stored in the memory 33a to the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 received this time. That is, after erasing the center frequencies fka and fkb stored in the memory 33a, the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 received this time are stored. As a result, even if the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 change due to a change in temperature or the passage of time, the center frequencies fka and fkb corresponding to the change in the center frequencies fka and fkb are changed to the above notches. It can be used as a reference for comparison with the frequency fc. Further, the filter control unit 33 determines that the center frequencies fka and fkb need not be updated when collation is established, and uses the current center frequencies fka and fkb stored in the memory 33a as a reference for collation with the notch frequency fc. To do.

  Here, as described in the background art above, even when a plurality of electronic keys 2 and 3 are registered, their usage frequency varies. For example, it is possible to store only the main electronic key 2 and keep the sub electronic key 3 at home. Therefore, in this example, the processing mode is switched according to the usage frequency of the electronic key.

  Specifically, after receiving the signal S5, the filter control unit 33 determines whether or not it is the same as the previously used electronic key. Here, the desired wave signals Sk1 and Sk2 include a code for identifying the key type. Therefore, the vehicle control unit 50 can recognize which one of the master and sub electronic keys 2 and 3 is based on the demodulated desired wave signals Sk1 and Sk2. The vehicle control unit 50 includes the information related to the key type in the signal S5 and transmits the information to the filter control unit 33. Thereby, the filter control part 33 can recognize the electronic keys 2 and 3 used for communication. When the filter control unit 33 determines that the electronic key is the same as the previously used electronic key, the filter control unit 33 increments the counter 33b (increases the count value by one). When the filter control unit 33 determines that the electronic key is not the same as the previously used electronic key, the filter control unit 33 resets the counter 33b. Thereby, the number of continuous use of the same electronic key can be counted. Then, the filter control unit 33 determines whether or not the number of continuous use of the electronic key is equal to or greater than a threshold value. This threshold value is set to a value at which a continuously used electronic key is expected to be used continuously in the future. When the filter control unit 33 determines that the number of times of continuous use of the electronic key is less than the threshold value, the filter control unit 33 sets its own processing mode to the normal processing mode. In the normal processing mode, as described above, the filter control unit 33 compares the notch frequency fc recognized through the notch frequency determination unit 34 with the center frequencies fka and fkb stored in the memory 33a.

  On the other hand, the filter control unit 33 enters the simple processing mode when it is determined that the number of continuous use of the electronic key is equal to or greater than the threshold. In the simple processing mode, the center frequency of the desired wave signal corresponding to the electronic key that is not used is not verified. For example, as described above, when only the master electronic key 2 is used, the number of continuous use of the electronic key 2 is equal to or greater than a threshold value. Then, the filter control unit 33 enters the simple processing mode, and collates the notch frequency fc recognized through the notch frequency determination unit 34 with the center frequency fka stored in the memory 33a. At this time, collation between the center frequency fkb and the notch frequency fc is not executed. Thereby, it is suppressed that the notch frequency fc coincides with the center frequency fkb and the filter coefficient is reset and the noise signal Sn is not removed. Further, when the verification of the center frequency fkb and the notch frequency fc is omitted, power consumption related to the processing can be reduced.

  Next, a control program related to processing mode switching executed by the filter control unit 33 will be described. The control program is executed according to the flowchart shown in FIG.

  First, it is recognized through the normal signal determination unit 42 whether or not the signals are the normal desired wave signals Sk1 and Sk2 (S101). When it is recognized that the desired desired wave signals Sk1 and Sk2 are recognized (YES in S101), when it is recognized that the ID code verification is established through the signal S5 (S102), the received desired wave signals Sk1 and Sk2 are received this time. Center frequencies fka and fkb are recognized (S103). Then, collation between the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 received this time and the center frequencies fka and fkb stored in the memory 33a is executed (S104). When the verification is not established (NO in S104), the center frequencies fka and fkb stored in the memory 33a are updated to the center frequencies fka and fkb of the desired wave signals Sk1 and Sk2 received this time (S105). Then, it is determined whether or not the electronic key is the same as the electronic key when the previous ID code collation was established (S106). When collation is established (YES in S104), the center frequencies fka and fkb are not updated, and it is determined whether or not the electronic key is the same as the electronic key when the previous ID code collation was established. (S106).

  When it is determined that the electronic key is not the same as the previous electronic key (NO in S106), the count value of the counter 33b, that is, the number of continuous use of the electronic key is reset (S107). If it is the simple processing mode at the start of the control program, the mode is shifted to the normal processing mode, and if it is the normal processing mode at the start of the control program, the mode is maintained (S108). Then, the control program is terminated.

  If it is determined that the electronic key is the same as the previous electronic key (YES in S106), it is determined whether the processing mode is the simple processing mode (S109). When it is determined that the processing mode is the simple processing mode (YES in S109), the control program is terminated while the simple processing mode is maintained. When it is determined that the processing mode is not the simple processing mode, that is, the normal processing mode (NO in S109), the count value of the counter 33b is incremented (S110). Then, it is determined whether or not the count value, that is, the number of continuous use is equal to or greater than a threshold value (S111). When it is determined that the number of times of continuous use is equal to or greater than the threshold (YES in S111), the normal processing mode is shifted to the simple processing mode (S112), and the control program is terminated. When it is determined that the number of times of continuous use is less than the threshold value (NO in S111), the control program is terminated while being maintained in the normal processing mode.

  On the other hand, when the normal signal determination unit 42 recognizes that the signal is not the normal desired signal Sk1, Sk2, that is, the non-normal signal (NO in S101), the filter coefficient corresponding to the non-normal signal is calculated. The filtered filter coefficient is reflected in the filter unit 31 (S113). Then, the notch frequency fc corresponding to the non-regular signal is recognized through the notch frequency determination unit 34 (S114). Next, it is determined whether or not it is a simple processing mode (S115).

  When it is determined that the processing mode is not the simple processing mode, that is, the normal processing mode (NO in S115), does the notch frequency fc recognized through the notch frequency determination unit 34 match the center frequency fka stored in the memory 33a? It is determined whether or not (S116). If this does not match (NO in S116), it is determined whether or not the notch frequency fc recognized through the notch frequency determination unit 34 matches the center frequency fkb stored in the memory 33a (S117). If this also does not match (NO in S117), the calculated filter coefficient is stored in the memory 33a (S118), and the control program is terminated.

  When it is determined that the notch frequency fc recognized through the notch frequency determination unit 34 matches the center frequency fka or the center frequency fkb stored in the memory 33a (YES in S116 or S117), the reflected filter The coefficient is reset (S119), and the control program is terminated. Thereby, it is possible to prevent not only the noise signal Sn but also the desired wave signals Sk1, Sk2 from being removed.

  If it is determined that the processing mode is the simple processing mode (YES in S115), it is determined whether or not the notch frequency fc recognized through the notch frequency determination unit 34 matches the center frequency stored in the memory 33a. (S120). The center frequency stored in the memory 33a at this time is the center frequency of the desired wave signal corresponding to the electronic key for which the number of continuous uses is equal to or greater than the threshold. That is, when only the master electronic key 2 is used, the center frequency is fka.

  When the notch frequency fc recognized through the notch frequency determination unit 34 and the center frequency stored in the memory 33a do not match (NO in S120), the calculated filter coefficient is stored in the memory 33a (S118), and the control is performed. The program is terminated. When the notch frequency fc matches the notch frequency fc stored in the memory 33a (YES in S120), the reflected filter coefficient is reset (S119), and the control program is terminated. As described above, in the case of the simple processing mode, the two determination processes in steps S116 and S117 in the normal process mode may be one determination process in step S120.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) For an electronic key that is determined to be less frequently used among the plurality of electronic keys 2 and 3, the determination as to whether or not the notch frequency fc matches the center frequencies fka and fkb of the electronic key is omitted. . Therefore, the filter coefficient is reset because the notch frequency fc coincides with the center frequencies fka and fkb of the desired wave signal corresponding to the electronic key that is not used, and the noise signal Sn removing function is canceled. Is suppressed. Thereby, the receiving sensitivity of the digital receiver 1 with respect to the electronic key with high use frequency is maintained. Further, when the determination is omitted, the power consumption related to the determination process can be reduced.

  (2) The usage frequency of the electronic keys 2 and 3 is determined based on the number of times of continuous use of the electronic keys 2 and 3. Thereby, it is possible to easily determine the frequency of use only by counting the number of times of continuous use of the electronic keys 2 and 3.

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
In the above embodiment, there are two electronic keys 2 and 3 in total, a master and a sub. However, it may be three or more. As the number of electronic keys increases, the number of verifications between the notch frequency and the center frequency in the normal processing mode increases, and the effect of reducing the number of verifications in the simple processing mode becomes more remarkable.

  In the above embodiment, when the number of times of continuous use of the electronic key (count value of the counter 33b) is equal to or greater than the threshold value, the use frequency of the electronic keys other than the electronic key is low and the simple processing mode is set. However, any method other than the above-mentioned continuous use number may be used as long as the use frequency of the electronic key can be recognized. For example, the usage rate of each electronic key in a certain period is calculated, and when the usage rate of any electronic key exceeds a predetermined rate, the usage frequency of the electronic key other than the electronic key is assumed to be low and the simple control mode is set. Is done. Conversely, when the usage rate of any electronic key falls below a predetermined rate, the simple control mode may be set as the usage frequency of the electronic key is low.

  In the above embodiment, whether or not to reset the filter coefficient by determining whether or not the notch frequency fc recognized through the notch frequency determination unit 34 matches the center frequencies fka and fkb stored in the memory 33a. Was decided. However, the determination method is not limited to this if it is determined that there is a possibility that the normal desired wave signals Sk1 and Sk2 may be removed through the stop band corresponding to the non-normal signal. For example, when it is determined that the stop band includes at least a part of the frequency bands of the desired wave signals Sk1 and Sk2, the filter coefficient may be reset.

  In the embodiment described above, a wireless key system in which the vehicle door is locked and unlocked based on the desired wave signals Sk1 and Sk2 transmitted from the electronic keys 2 and 3 to the vehicle in a single direction is employed as the electronic key system. However, if it is an electronic key system, what is called a key operation free system which performs two-way communication between the electronic keys 2 and 3 and a vehicle may be sufficient. In this system, a response request signal is transmitted around the vehicle. When receiving the response request signal, the electronic key transmits a desired wave signal Sk1 including an ID code. Thereafter, the vehicle door can be locked and unlocked on condition that ID code verification is established as in the wireless key system.

  In the above embodiment, locking / unlocking is performed through verification of the ID code included in the desired wave signal Sk1, but control performed through verification of the ID code is not limited to this. For example, when the collation of the ID code included in the desired wave signal Sk1 from the electronic key 2 existing in the vehicle is established, the engine start permission state may be set. In this state, the engine is started when a switch provided near the driver's seat is operated.

  In the above embodiment, the digital receiver 1 is applied to a vehicle electronic key system. However, as long as it is a digital receiver that communicates with a portable device, it is not limited to a vehicle electronic key system, and may be a residential electronic key system, for example. Furthermore, the present invention can be applied not only to the key system.

Next, the technical idea that can be grasped from the embodiment will be described together with the effects.
(A) The digital receiver according to claim 3, wherein the center frequency of each desired wave signal stored in advance is updated based on the received desired wave signal.

  According to this configuration, the center frequency of each desired wave signal stored in advance is updated. Therefore, even if the center frequency of the desired wave signal actually transmitted from the portable device changes due to a change in temperature or the passage of time, the center frequency of the stored desired wave signal can be made accurate.

  (B) In the digital receiver according to item (a), the digital receiver is provided in a control target that executes control when the validity of the desired wave signal from the portable device is confirmed, The center frequency is updated when the validity of the desired wave signal is confirmed in the controlled object.

  DESCRIPTION OF SYMBOLS 1 ... Digital receiver, 2, 3 ... Electronic key, 30 ... Noise removal part, 31 ... Filter part, 32 ... Adder, 33 ... Filter control part, 34 ... Notch frequency determination part, 41 ... Demodulation part, 42 ... Regular Signal determination unit.

Claims (3)

Receives desired wave signals transmitted at different frequencies from multiple portable devices and determines that a non-regular signal that is not a regular desired signal is received in order to remove the noise signal contained in the desired signal A filter having a stop band for removing the non-normal signal is formed by updating the filter coefficient, and it is determined whether the frequency of each desired wave signal stored in advance is included in the stop band. In the digital receiver that resets the filter coefficient when it is determined that the frequency of each desired wave signal is included in the stop band,
Digital in which determination of whether or not the use frequency of a specific portable device among the plurality of portable devices is low includes determination of whether or not the stop band includes a frequency of a desired wave signal corresponding to the specific portable device Receiver device. The digital receiver according to claim 1.
A digital receiver that determines that the frequency of use of a portable device other than the portable device is low when the number of continuous uses of the portable device exceeds a threshold value. The digital receiver according to claim 1 or 2,
The determination as to whether or not the frequency of each desired wave signal stored in advance is included in the stop band is stored in advance as the notch frequency of the filter that maximizes the signal level attenuation in the stop band. A digital receiver that determines whether or not the center frequency of each desired wave signal matches.

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