JP4807588B2 - Noise removal device - Google Patents

Description

  The present invention relates to a noise removing device, and more particularly to a noise removing device that removes pulse noise and demodulates a received signal.

  In Patent Document 1, pulse noise included in a signal to be processed is detected, a threshold value is generated based on the detected pulse noise, and a period during which the detected pulse noise exceeds the threshold is processed. There is disclosed a noise removal device that inhibits signal output and complements and outputs a signal during the period.

According to the noise removal device disclosed in Patent Document 1, when pulse noise is temporarily input, output of the signal to be processed is prohibited during the period in which the pulse noise is input. When pulsed noise is continuously input, the output of the signal to be processed is initially prohibited during the period in which the pulsed noise is input. The output of the processed signal is not prohibited even during the period in which the noise is input. Thereby, when pulse noise is continuously input, it is possible to prevent the output signal such as the audio signal from being interrupted.
JP 2005-197813 A

  However, the noise removal device disclosed in Patent Document 1 is effective in preventing an output signal such as an audio signal from being interrupted when pulsed noise is continuously input. Is output with pulse noise included, and is not suitable for applications where it is desired to completely remove pulse noise.

  An object of the present invention is to effectively remove pulse noise included in a received signal when demodulating the received signal.

  In order to achieve the above object, the present invention employs the following configuration. The reference numerals in parentheses show an example of the correspondence relationship with the drawings, and do not limit the scope of the present invention.

  The noise removal apparatus of the present invention includes a noise detection circuit (119), a demodulation processing unit (118), and a threshold control unit (13). The noise detection circuit detects pulse noise included in the received signal using a noise detection threshold. The demodulation processing unit demodulates the received signal by removing the pulse noise during a period when the pulse noise is detected by the noise detection circuit. The threshold control unit changes the noise detection threshold for detecting pulse noise in the noise detection circuit according to the input level of the received signal.

  The threshold control unit may increase the noise detection threshold when the input level of the received signal is high compared to when the input level of the received signal is low.

  The threshold control unit may lower the noise detection threshold when the input level of the received signal is low than when the input level of the received signal is high.

  Further, the threshold control unit may set the noise detection threshold so that the level is higher by a predetermined amount than the input level of the received signal.

  Further, the demodulation processing unit may remove the pulse noise by thinning out sampling data of the received signal in a period in which the pulse noise is detected by the noise detection circuit.

  Further, the demodulation processing unit may remove the pulse noise by correcting the reception signal in the period in which the pulse noise is detected by the noise detection circuit based on the reception signal immediately before or after the period. Good.

  In addition, the threshold control unit may increase or decrease the noise detection threshold as time elapses.

  According to the present invention, since the noise detection threshold for detecting pulse noise is changed according to the input level of the received signal, the distance between the transmitter and the receiver changes to change the input level of the received signal. Even in this case, pulse noise can be effectively removed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, although the case where the noise removal apparatus of this invention is applied to a vehicle equipment remote control system is demonstrated below, this invention is applicable also to systems other than a vehicle equipment remote control system.

  FIG. 1 is a block diagram showing a configuration of an in-vehicle device remote control system. The in-vehicle device remote control system includes an in-vehicle device 10 and a portable device 30 having a wireless communication function. The in-vehicle device 10 is mounted on a vehicle, and the portable device 30 is carried by the user of the vehicle.

  The in-vehicle device 10 includes a receiving unit 11, a transmitting unit 12, and a control unit 13. The receiving unit 11 has a receiving antenna (111 in FIG. 2). The receiving antenna 111 is disposed, for example, in the vicinity of the rearview mirror and in the pillar. The transmission unit 12 has a transmission antenna. The transmission antenna is disposed, for example, on the outer handle of the door.

  The transmission unit 12 modulates the data binarized into “0” and “1” (AM modulation or FM modulation) in accordance with a command from the control unit 13 and outputs the modulated data. The modulated signal output from the transmission unit 12 is transmitted to the outside via the transmission antenna. In a system that does not need to transmit radio waves from the in-vehicle device 10 to the portable device 30 (for example, a system that simply locks or unlocks the door of the vehicle according to the radio waves from the portable device 30), the in-vehicle device Ten transmitters 12 are unnecessary.

  When receiving the radio wave transmitted from the portable device 30 via the receiving antenna 111, the receiving unit 11 demodulates the received signal into binary data and outputs the demodulated signal. The demodulated signal output from the receiving unit 11 is supplied to the control unit 13.

The control unit 13 is configured around a known microcomputer including a CPU, a ROM, a RAM, and the like. In addition to the receiving unit 11 and the transmitting unit 12, the control unit 13 includes a door lock motor 21 for locking and unlocking the door of the vehicle, and a door lock switch 22 for detecting the locked / unlocked state of the door. A door open / close detection switch 23 for detecting the open / closed state of the door and an ignition switch 24 are connected. An ignition signal indicating the ON / OFF state of the ignition switch 24 is supplied from the ignition switch 24 to the control unit 13. A door lock motor 21, a door lock switch 22, and a door open / close detection switch 23 are provided in each door.

  The outline of the operation of the in-vehicle device remote control system will be described below.

  When the user of the vehicle presses the lock button or the unlock button of the portable device 30, a radio wave including a control code corresponding to the pressed button and an identification code unique to the vehicle is transmitted from the portable device 30.

  A radio wave transmitted from the portable device 30 is received by the receiving unit 11 of the in-vehicle device 10, and a demodulated signal generated based on the radio wave is supplied to the control unit 13. The control unit 13 determines whether or not the identification code included in the demodulated signal matches the identification code unique to the vehicle. If it is determined that the identification code matches, the control unit 13 includes the demodulated signal. The door lock motor 21 is driven according to the control code (lock instruction code or unlock instruction code) to lock or unlock all the doors of the vehicle. Therefore, according to the in-vehicle device remote control system, the vehicle door can be remotely locked or unlocked without contact by communication between the in-vehicle device 10 and the portable device 30.

  Here, an example in which all the doors of the vehicle are locked or unlocked in response to the user pressing the lock button or unlock button of the portable device 30 will be described, but the present invention is not limited to this. For example, the in-vehicle device 10 may detect that the portable device 30 approaches or leaves the vehicle, and all the doors of the vehicle may be unlocked or locked. In this case, when the response request signal is transmitted from the transmission unit 12 of the in-vehicle device 10 at a constant cycle, and the portable device 30 is located within the receivable area of the response request signal, the portable device 30 Then, a response signal including the identification code is transmitted to the in-vehicle device 10. Thereby, the in-vehicle device 10 can detect whether or not the portable device 30 is located in the area where the response request signal can be received, and can detect that the portable device 30 approaches or leaves the vehicle. Can do.

  Note that, as described above, a vehicle-mounted device remote control system that remotely controls the vehicle-mounted device based on the radio wave from the portable device 30 (for example, the door is locked or unlocked in response to the user operating the switch of the portable device 30). Not only a locking system or a system that automatically locks or unlocks a door in response to the user approaching or leaving the vehicle, but also the use of in-vehicle devices based on radio waves from the portable device 30. The present invention can also be applied to an in-vehicle device remote control system capable of controlling availability (that is, permitting or prohibiting use of the in-vehicle device by a user). As an example of such an in-vehicle device remote control system, if the user carries the portable device 30, the door can be locked simply by operating the door unlocking switch or the engine start switch without inserting the key into the key cylinder. There is an in-vehicle device remote control system (for example, a smart ignition device described in Japanese Patent Application Laid-Open No. 2002-29385) that enables unlocking the engine and starting the engine.

  Hereinafter, details of the receiving unit 11 will be described with reference to FIG. 2.

  The receiving unit 11 has a receiving antenna 111. A SAW (Surface Acoustic Wave) filter 112 is connected to the receiving antenna 111. The SAW filter 112 extracts a signal in a band including the carrier frequency of the in-vehicle device 10 and the portable device 30 from the analog reception signal received by the reception antenna 111.

  An amplifier 113 and a noise detection circuit 119 are connected to the SAW filter 112.

The amplifier 113 amplifies the signal output from the SAW filter 112. A mixer 114 is connected to the amplifier 113. The mixer 114 mixes the output signal of the amplifier 113 and the local frequency signal from the local oscillator 115, thereby down-converting the modulation signal received by the reception antenna to an intermediate frequency. An IF (Intermediate Frequency) filter 116 is connected to the mixer 114. IF filter 116 extracts a signal in a desired band from the output signal of mixer 114.

  An amplifier 117 is connected to the IF filter 116. The amplifier 117 amplifies the signal output from the IF filter 116. A demodulation processing unit 118 is connected to the amplifier 117.

  The noise detection circuit 119 detects pulse noise that cannot be removed by the SAW filter 112, and supplies a signal indicating the presence or absence of the pulse noise to the demodulation processing unit 118.

  The demodulation processing unit 118 is supplied with the output signal of the amplifier 117 and the output signal of the noise detection circuit 119. The demodulation processing unit 118 demodulates the output signal of the amplifier 117 to extract binarized data, and outputs the binarized data to the control unit 13 as a demodulated signal. At this time, the demodulation processing unit 118 removes pulse noise detected by the noise detection circuit 119 based on the output signal of the noise detection circuit 119.

  Next, the operation of the noise detection circuit 119 will be described with reference to FIG.

  The noise detection circuit 119 determines that the received signal contains noise when a signal having a level exceeding the noise detection threshold is output from the SAW filter 112. As shown in FIG. 3A, the noise detection threshold is sufficiently large (for example, carrier input) with respect to the carrier input level (that is, the input level of the radio wave transmitted from the portable device 30 in the receiving unit 11). The level is set to twice the level). That is, when a signal significantly larger than the carrier input level is input, the noise detection circuit 119 regards the signal as noise.

  FIG. 3B is an example of a demodulated signal when the received signal does not contain pulse noise. If the received signal contains pulse noise as shown in FIG. If the pulse noise is not removed, the waveform of the demodulated signal is affected by the pulse noise and deteriorates as shown in FIG. 3C, resulting in a communication error. There is.

  In the present embodiment, the noise detection circuit 119 detects pulse noise using the noise detection threshold as described above, and demodulates the signal indicating the detection result (for example, the signal shown in FIG. 3D). 118. The demodulation processing unit 118 removes pulse noise from the received signal based on the output signal of the noise detection circuit 119, and as a result, outputs a demodulated signal as shown in (e) of FIG. As a method for removing pulse noise in the demodulation processing unit 118, for example, a signal in the pulse noise generation period is corrected or interpolated based on the level of the received signal immediately before or immediately after the pulse noise generation period. It is possible to adopt a method or a method of thinning sampling data during the generation period of pulse noise.

  In the example of FIG. 3, the noise detection threshold used in the noise detection circuit 119 is constant (that is, does not change with the passage of time), but a problem arises when the noise detection threshold is always constant. Hereinafter, with reference to FIG. 4 to FIG. 6, a problem that occurs when the noise detection threshold is always constant will be described.

FIG. 4 shows a state in which the user carrying the portable device 30 approaches the vehicle (moves from the position P1 to the position P2). In the concentric circles indicated by chain lines in the figure, the distance from the receiving unit 11 is farther toward the outer circle. At this time, the carrier input level decreases as the distance between the portable device 30 and the receiving unit 11 increases, and the carrier input level increases as the distance between the portable device 30 and the receiving unit 11 decreases. Over time (ie as the user approaches the vehicle).

  Here, it is assumed that pulse noise A and pulse noise B as shown in FIG. 5 are generated while the user is approaching the vehicle. As a virtual example, when noise detection is performed using the noise detection threshold shown in FIG. 5 in the noise detection circuit 119, the pulse noise B can be detected as noise, but the pulse noise A is detected as noise. I can't. Therefore, as another hypothetical example, if the noise detection threshold is lowered so that not only the pulse noise A but also the pulse noise B can be detected, not only the pulse noise A but also the pulse noise as shown in FIG. B can also be detected as noise. However, in this case, when the user moves close to the vehicle, the carrier input level exceeds the noise detection threshold as shown in FIG. 6, and as a result, all the signals from the portable device 30 are regarded as noise. As a result, communication becomes impossible.

  Therefore, in the present embodiment, the noise detection threshold used in the noise detection circuit 119 is made variable by the threshold control signal from the control unit 13 in order to solve the above problem. Specifically, the control unit 13 increases the noise detection threshold as the carrier input level increases, and decreases the noise detection threshold as the carrier input level decreases. As a result, the noise detection threshold fluctuates according to the carrier input level as shown in FIG. 7. As a result, not only the pulsed noise A but also the pulsed noise B can be detected, and the user is in the immediate vicinity of the vehicle. The carrier input level does not exceed the noise detection threshold even when moving up to. Therefore, the accuracy of removing the pulse noise can be increased and the frequency of occurrence of communication errors can be reduced.

  FIG. 7 shows an example of a case where a user carrying the portable device 30 approaches the vehicle. Similarly, when a user carrying the portable device 30 moves away from the vehicle, the user inputs the same according to the carrier input level. It is effective to vary the noise detection threshold. FIG. 8 shows a control example of the noise detection threshold when the user carrying the portable device 30 moves away from the vehicle.

  In order to vary the noise detection threshold according to the carrier input level, the control unit 13 needs to know the current carrier input level. As a method for this, the carrier input level is actually determined from the current received signal. Method of detecting (first method), method of predicting current carrier input level from past received signals (second method), and method of estimating current carrier input level by estimating user behavior (Third method) can be considered. In the present invention, any of these first to third methods may be adopted.

  In the present embodiment, the control unit 13 varies the noise detection threshold by the third method. Specifically, the control unit 13 determines whether or not the user carrying the portable device 30 is approaching the vehicle and whether or not the user carrying the portable device 30 is leaving the vehicle. Judging.

There are various determination methods as to whether or not the user carrying the portable device 30 is approaching the vehicle. For example, as described above, a response request signal is transmitted from the transmission unit 12 of the in-vehicle device 10 at a constant period, and the presence or absence of a response signal from the portable device 30 in response to this response request signal is monitored. It is possible to detect approaching. That is, if the response signal from the portable device 30 cannot be received, it can be understood that the user is approaching the vehicle. As another method, when the unlocking code is received from the portable device 30 when the door is locked (whether the door is locked can be determined by the door lock switch 22), the user gets on You can see that you are approaching the vehicle.

  When it is determined that the user is approaching the vehicle as described above, the control unit 13 gradually increases the noise detection threshold according to the elapsed time from the time when the determination is made. The increase speed of the noise detection threshold may be set in advance based on, for example, a standard user walking speed. Note that the initial value of the noise detection threshold and the increasing speed thereof may be set to optimum values through experiments or the like. In the example of FIG. 7, the increase amount of the noise detection threshold per unit time is constant, but the present invention is not limited to this. Note that the maximum value of the noise detection threshold may be set to an optimum value based on the measurement result obtained by measuring the carrier input level when the portable device 30 is in the immediate vicinity of the receiving unit 11, for example.

  Similarly, there are various determination methods as to whether or not the user carrying the portable device 30 is leaving the vehicle. For example, when the ignition switch 24 is turned “OFF” and then the door open / close detection switch 23 is changed from the “closed” state to the “open” state again to the “closed” state (that is, the user gets off the vehicle) The user is about to move away from the vehicle.

  When it is determined that the user is moving away from the vehicle as described above, the control unit 13 gradually decreases the noise detection threshold value according to the elapsed time from the determination. The reduction speed of the noise detection threshold may be set in advance based on, for example, a standard user walking speed. Note that the initial value of the noise detection threshold and the rate of decrease thereof may be set to optimum values through experiments or the like. In the example of FIG. 8, the reduction amount of the noise detection threshold per unit time is constant, but the present invention is not limited to this.

  As described above, according to the present embodiment, when demodulating a reception signal, pulse noise included in the reception signal can be effectively removed.

  The present invention is useful, for example, as an in-vehicle device remote control system that can effectively remove pulse noise included in a received signal when demodulating the received signal.

The figure which shows the structure of the vehicle equipment remote control system which concerns on one Embodiment of this invention. The figure which shows the structure of the receiving part 11. Diagram showing how to remove pulse noise The figure which shows a mode that a user approaches a vehicle The figure which shows the relationship between the noise detection threshold value in a hypothetical example, pulse noise, and a carrier input level The figure which shows the relationship between the noise detection threshold value in a hypothetical example, pulse noise, and a carrier input level The figure which shows the example of control of the noise detection threshold value when a user approaches a vehicle The figure which shows the example of control of the noise detection threshold when a user leaves | separates from a vehicle

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 In-vehicle apparatus 11 Reception part 12 Transmission part 13 Control part 21 Door lock motor 22 Door lock switch 23 Door open / close detection switch 24 Ignition switch 30 Portable machine 111 Reception antenna 112 SAW filter 113 Amplifier 114 Mixer 115 Local oscillator 116 IF filter 117 Amplifier 118 Demodulation processor 119 Noise detection circuit

Claims (7)

A noise detection circuit for detecting pulse noise included in the received signal using a noise detection threshold;
A demodulation processing unit that removes the pulse noise and demodulates the received signal during a period in which the pulse noise is detected by the noise detection circuit;
A noise detection threshold for detecting pulse noise in the noise detection circuit, and a threshold control unit for changing the threshold according to the input level of the received signal ;
The threshold control unit increases the noise detection threshold when the input level of the received signal is high compared to when the input level of the received signal is low . A noise detection circuit for detecting pulse noise included in the received signal using a noise detection threshold;
A demodulation processing unit that removes the pulse noise and demodulates the received signal during a period in which the pulse noise is detected by the noise detection circuit;
A noise detection threshold for detecting pulse noise in the noise detection circuit, and a threshold control unit for changing the threshold according to the input level of the received signal;
The noise removal apparatus according to claim 1, wherein the threshold control unit lowers the noise detection threshold when the input level of the received signal is low compared to when the input level of the received signal is high. The noise removal apparatus according to claim 1 , wherein the threshold value control unit sets the noise detection threshold value so as to be a level higher by a predetermined amount than an input level of a received signal. A noise detection circuit for detecting pulse noise included in the received signal using a noise detection threshold;
A demodulation processing unit that removes the pulse noise and demodulates the received signal during a period in which the pulse noise is detected by the noise detection circuit;
A threshold control unit for controlling a noise detection threshold for detecting pulse noise in the noise detection circuit;
Determining means for determining whether or not the user is approaching the vehicle,
The threshold control unit gradually increases the noise detection threshold according to an elapsed time from the time when the determination unit determines that the user is approaching a vehicle. . A noise detection circuit for detecting pulse noise included in the received signal using a noise detection threshold;
A demodulation processing unit that removes the pulse noise and demodulates the received signal during a period in which the pulse noise is detected by the noise detection circuit;
A threshold control unit for controlling a noise detection threshold for detecting pulse noise in the noise detection circuit;
Determination means for determining whether or not the user is moving away from the vehicle,
The noise removal apparatus, wherein the threshold control unit gradually decreases the noise detection threshold according to an elapsed time from the time when the determination unit determines that the user is moving away from the vehicle. 6. The demodulation unit according to claim 1, wherein the demodulation processing unit removes the pulse noise by thinning out a sample of the received signal in a period in which the pulse noise is detected by the noise detection circuit . The noise removal device according to item 1 . The demodulation processing unit removes the pulse noise by correcting the reception signal in the period in which the pulse noise is detected by the noise detection circuit based on the reception signal immediately before or after the period. The noise removal device according to any one of claims 1 to 5, wherein the noise removal device is characterized.

Images