JP2009005028A - Noise eliminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately generate desired waves within a desired frequency band by eliminating pulse noise superimposed on reception signals, relating to a noise eliminating device. <P>SOLUTION: The noise eliminating device for eliminating noise from the reception signals is provided with: a sub reception means provided separately from a main reception means for receiving signals within the desired frequency band among the reception signals, for receiving the signals out of the desired frequency band among the reception signals; a noise detection means for detecting the noise on the basis of the signals out of the desired frequency band received in the sub reception means; and a noise elimination means for eliminating the noise superimposed on the signals within the desired frequency band received by the main reception means on the basis of the noise detected by the noise detection means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a noise removing apparatus, and more particularly to a noise removing apparatus suitable for removing various pulse noises superimposed on a received signal.

2. Description of the Related Art Conventionally, a noise removing device is known that removes noise from a received signal when pulsed noise caused by engine ignition or the like is superimposed on a received signal received by a radio receiver mounted on a vehicle ( For example, see Patent Document 1). A receiving apparatus having the noise removing apparatus has a plurality of receiving units that receive a plurality of frequency bands (AM band and FM band). In the noise removing device, when a signal in one frequency band (AM band) is received, noise is detected using a receiving unit in another frequency band (FM band) different from that frequency band. . When noise is detected, the signal path including the noise pulse is blocked.
JP-A-9-214370

  However, if the signal path is interrupted when noise is detected as in the device of the above-mentioned Patent Document 1, sound containing noise is not output, but the signal path is interrupted. Even if the interruption time is short, there is a time when the received voice is not output at all.

  The present invention has been made in view of the above-described points, and provides a noise removing device capable of accurately generating a desired wave in a desired frequency band by removing pulse noise superimposed on a received signal. The purpose is to provide.

  The above-described object is a noise removing device that removes noise from a received signal, and is provided separately from a main receiving unit that receives a signal within a desired frequency band of the received signal, and is outside the desired frequency band of the received signal. Sub-reception means for receiving a signal; noise detection means for detecting noise based on a signal outside a desired frequency band received by the sub-reception means; and the main signal based on noise detected by the noise detection means. This is achieved by a noise removing device comprising noise removing means for removing noise superimposed on a signal within a desired frequency band received by the receiving means.

  In the invention of this aspect, sub-reception means for receiving signals outside the desired frequency band is provided separately from the main reception means for receiving signals within the desired frequency band of the received signals. Unlike the signal in the desired frequency band, the pulse noise is present over a wide band. Therefore, the noise component is difficult to be manifested in the desired frequency band, but is easily manifested outside the desired frequency band. Accordingly, it is possible to detect pulsating noise based on a signal outside the desired frequency band received by the sub-receiving means. Then, based on the detected noise, if the noise superimposed on the signal in the desired frequency band received by the main receiving means is removed, the desired wave in the desired frequency band where no noise is superimposed is generated. Is possible.

  Further, the above object is a noise removing device that removes noise from a received signal, and is provided separately from a main filter that extracts a signal in a desired frequency band from a received signal received by the receiving means. A sub-filter for extracting a signal outside the desired frequency band from the received signal received, a noise detection unit for detecting noise based on a signal outside the desired frequency band extracted by the sub-filter, and detection by the noise detection unit This is achieved by a noise removal device comprising noise removal means for removing noise superimposed on a signal within a desired frequency band received by the main reception means on the basis of the generated noise.

  In the invention of this aspect, a sub filter for extracting a signal outside the desired frequency band is provided separately from the main filter for extracting the signal within the desired frequency band from the received signal received by the receiving means. Unlike the signal in the desired frequency band, the pulse noise exists over a wide band, so that the noise component is difficult to manifest in the signal in the desired frequency band, but is easily manifested in the signal outside the desired frequency band. Become. Therefore, it is possible to detect pulse noise based on a signal outside the desired frequency band extracted by the sub-filter. Then, based on the detected noise, if the noise superimposed on the signal in the desired frequency band received by the main receiving means is removed, the desired wave in the desired frequency band where no noise is superimposed is generated. Is possible.

  The noise removing device includes a noise generating source specifying unit that specifies a noise generating source based on a property of noise detected by the noise detecting unit, and the noise removing unit includes the noise generating source specifying unit. If the noise is removed by a technique according to the nature of the noise generated by the specified noise generation source, various types of pulse noise superimposed on the signal within the desired frequency band can be obtained by a technique according to the nature. By removing, it is possible to generate a desired wave in a desired frequency band in which noise is not superimposed regardless of the type of noise.

  Moreover, in the above-described noise removing apparatus, if the noise generation source specifying unit specifies the noise generation source based on the noise generation frequency and duration detected by the noise detection unit, It becomes possible to accurately remove pulse noise from the signal.

  Further, the above-described noise removal apparatus further includes a storage unit that stores a relationship between a noise generation source and a noise removal method in advance, and the noise removal unit is determined based on the relationship stored in the storage unit. The noise may be removed by a method according to the nature of the noise generated by the noise generation source specified by the noise generation source specifying means.

  According to the present invention, a desired wave in a desired frequency band can be generated with high accuracy by removing pulse noise superimposed on a received signal.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration diagram of a noise removing apparatus 10 according to a first embodiment of the present invention. The noise removal device 10 of this embodiment is a device that is applied to a reception device 12 mounted on a vehicle and removes pulse noise from a reception signal received by the reception device 12. The receiving device 12 is an in-vehicle broadcast receiving device that receives radio broadcasts and television broadcasts of AM and FM, and is generated when various on-vehicle electric components (for example, an ignition device, an electric motor, PWM switching, etc.) are operated. It is a device that can be affected by pulse noise.

  As shown in FIG. 1, the receiving device 12 includes a receiving antenna 14. The receiving antenna 14 receives a broadcast wave of the above-described radio broadcast or television broadcast. An RF unit 16 is connected to the receiving antenna 14. The RF unit 16 is a part that amplifies a carrier wave in a radio broadcast band and a television broadcast band.

  The noise removing device 10 includes two receiving units (tuners) 20 and 22 made of a superheterodyne method or the like that constitute the receiving device 12. The output of the RF unit 16 is supplied to each of the two receiving units 20 and 22 as a received signal. The receiving unit 20 has a mixer to which a local oscillation frequency fd is given so as to select a desired wave having a desired center frequency fd. The receiving unit 22 has a mixer to which a local oscillation frequency fd + Δf is given so as to select a signal outside the band different from the desired wave having the desired center frequency fd.

  The receiving unit 20 can receive a signal within the desired frequency band (center frequency fd) among the received signals from the RF unit 16, and filters the noise generated outside the desired desired wave band to obtain the desired signal. Adjust the wave gain. The receiving unit 22 can receive a signal outside the desired frequency band (center frequency fd + Δf) among the received signals from the RF unit 16, and extracts a signal outside the band of the desired wave to adjust the gain. Do. Note that Δf is a frequency at which a frequency outside the desired frequency band and a PWM switching frequency of about 10 kHz or more can be realized. Hereinafter, the reception unit 20 is referred to as a main reception unit 20, and the reception unit 22 is referred to as a sub reception unit 22.

  An IF unit 24 is connected to the main reception unit 20, and an IF unit 26 is connected to the sub reception unit 22. The output of the main receiving unit 20 is supplied to the IF unit 24, and the output of the sub receiving unit 22 is supplied to the IF unit 26. The IF unit 24 converts the signal in the desired frequency band from the main receiving unit 20 to an intermediate frequency (for example, 10.7 MHz). The IF unit 26 converts the signal outside the desired frequency band from the sub-receiving unit 22 to an intermediate frequency.

  The noise removal apparatus 10 also includes an input level detection unit 30, a noise detection unit 32, a noise frequency / duration detection unit 34, a noise cancellation level determination unit 36, and a noise cancellation processing unit (noise canceller) 40. .

  The input level detection unit 30 is connected to the IF unit 24, and the noise detection unit 32 is connected to the IF unit 26. The input level detection unit 30 detects the input level (electric field strength) of the received signal based on the signal within the desired frequency band supplied from the IF unit 24. The noise detection unit 32 detects pulse noise based on a signal outside the desired frequency band supplied from the IF unit 26, and specifically detects the level (electric field strength) of the signal. And it is discriminate | determined whether the detected signal level is more than the threshold value which shows the boundary value of noise presence or absence.

  A noise frequency / duration detector 34 is connected to the noise detector 32. The noise detection unit 32 supplies a signal indicating noise generation to the noise frequency / duration detection unit 34 when the signal level is equal to or higher than the threshold value. Based on the signal supplied from the noise detector 32, the noise frequency / duration detector 34 is a time between when noise of a level higher than a threshold occurs and when noise of a level higher than the threshold immediately occurs. The interval, that is, the time interval when the noise level is equal to or higher than the threshold (that is, the noise cycle or noise occurrence frequency) and the duration of the state where the noise level is equal to or higher than the threshold are detected.

  A noise cancellation level determination unit 36 is connected to the input level detection unit 30, the noise detection unit 32, and the noise frequency / duration detection unit 34 described above. The input level detection unit 30 indicates the input level of the signal within the desired frequency band, the noise detection unit 32 indicates the input level of the signal outside the desired frequency band, and the noise frequency / duration detection unit 34 indicates the noise period and noise duration. Are supplied to the noise cancellation level determination unit 36, respectively.

  The noise cancellation level determination unit 36 determines whether or not pulse noise is generated based on signals from the input level detection unit 30, the noise detection unit 32, and the noise frequency / duration detection unit 34, and the noise is detected. Further, when it occurs, after grasping the nature of the pulse noise, the noise generation source that generated the noise is specified as will be described in detail later. Then, an optimum process (noise cancellation process) for canceling the noise caused by the noise generation source is determined.

  A detection unit 38 is also connected to the IF unit 24 connected to the main reception unit 20. The detector 38 detects a signal in the desired frequency band supplied from the IF unit 24. A noise canceller 40 is connected to the detection unit 38. The noise canceller 40 is also connected to the noise cancellation level determination unit 36. The noise canceller 40 processes the signal in the desired frequency band detected by the detection unit 38 according to the optimum noise cancellation process determined by the noise cancellation level determination unit 36.

  FIG. 2 shows a comparison between noise and a desired wave. FIG. 3 shows a state in which noise is superimposed on a signal in the desired frequency band (FIG. 3A) and a state in which noise is superimposed on a signal outside the desired frequency band (FIG. 3B). A diagram is shown.

  Noise input to the receiving device 12 is caused by on / off of an in-vehicle switch, engine ignition, electric motor driving, PWM switching driving, clock generation, and the like. In this respect, the desired wave in the desired frequency band has a peak power at a specific frequency, but the pulse noise is distributed over a wide band. In addition, the desired wave has a large input level at predetermined time intervals (510 kHz to 1710 kHz in the AM band and 76 MHz to 108 MHz in the FM band), but the pulse noise is generally the time of the desired wave described above. The noise level increases at a time interval longer than the interval (for example, several tens Hz in the engine ignition system, several hundred Hz to several kHz in the electric motor drive system, and several hundred Hz to several tens kHz in the PWM drive system). Further, since the desired wave of broadcasting is always generated, the duration of the high level state is extremely long, but the duration of the noise state is relatively short.

  In this regard, as shown in FIG. 3A, when pulse noise is superimposed on a signal within a desired frequency band, the noise component is desired by combining the noise and a desired wave having a high power level. In the frequency band, it becomes difficult to manifest. On the other hand, as shown in FIG. 3B, when pulsating noise is superimposed on a signal outside the desired frequency band, the noise component is synthesized into a desired wave having a low power level, so that the noise component becomes the desired frequency band. It becomes easy to be manifested outside.

  Therefore, the noise removal apparatus 10 of the present embodiment is characterized in that noise is detected based on a signal outside that band different from the desired frequency band, and based on the nature of the detected noise. Thus, the noise generation source is specified, and the noise corresponding to the noise generation source is appropriately removed from the signal in the desired frequency band. Hereinafter, with reference to FIG. 4 and FIG. 5, the characteristic part of a present Example is demonstrated.

  FIG. 4 shows a flowchart of an example of a control routine executed in the noise removal apparatus 10 of the present embodiment. FIG. 5 shows a table defining the relationship between the nature of noise, the noise generation source, and the optimum noise cancellation processing for removing noise.

  In the receiving device 12 including the noise removing device 10 of the present embodiment, the main receiving unit 20 extracts and outputs a signal of the center frequency fd of the desired wave within the desired frequency band from the received signal from the RF unit 16 ( Step 100). At this time, when pulse noise is generated, the main reception unit 20 outputs a signal having a center frequency fd on which the pulse noise is superimposed.

  The signal of the center frequency fd output from the main reception unit 20 is frequency-converted to an intermediate frequency by the IF unit 24, and then input to the detection unit 38 and further input to the input level detection unit 30. Based on the signal from the main receiver 20, the input level detector 30 detects and records the input level (electric field strength) of the desired wave in the desired frequency band (step 102). The input level of the desired wave within the desired frequency band detected by the input level detection unit 30 is supplied to the noise cancellation level determination unit 36. The noise cancellation level determination unit 36 grasps the input level of the desired wave within the desired frequency band from the input level detection unit 30.

  On the other hand, the sub-reception unit 22 extracts and outputs a signal having a center frequency fd + Δf outside the desired frequency band from the reception signal from the RF unit 16 (step 110). The center frequency fd + Δf is a frequency that is outside the desired frequency band, is a frequency with a low input signal level (electric field strength) due to the desired wave, and is a frequency that is equal to or higher than the PWM switching frequency (up to about 10 kHz). . In addition, the center frequency fd + Δf may be a value that is fixed with respect to the set fd, that is, a value that is set to a constant value, as long as the frequency is outside the desired frequency band. Further, it may be a value irrelevant to fd, that is, a value predetermined outside the desired frequency band (for example, 500 kHz or 1800 kHz if the AM band 510 kHz to 1710 kHz is the target frequency of the desired wave).

  The signal of the center frequency fd + Δf output from the sub receiver 22 is frequency-converted to an intermediate frequency by the IF unit 26 and then input to the noise detector 32. The noise detection unit 32 detects the level of a signal outside the desired frequency band based on the signal from the sub reception unit 22 every predetermined time (for example, several tens of milliseconds), and the level is determined as noise. It is determined whether or not the threshold value is greater than or equal to a threshold value indicating presence or absence, that is, whether or not noise is generated (step 112).

  As a result, when the noise detection unit 32 determines that no noise is generated because the signal level outside the desired frequency band is less than the threshold, the noise frequency / duration detection unit 34 sends a signal indicating noise generation. Without supply, a signal indicating that noise has not occurred is supplied to the noise cancellation level determination unit 36. When receiving a signal indicating that noise has not occurred from the noise detection unit 32, the noise cancellation level determination unit 36 instructs the noise canceller 40 not to perform noise cancellation processing. In this case, the signal in the desired frequency band (detection signal) detected by the detection unit 38 is output without being subjected to noise cancellation processing in the noise canceller 40 (step 114).

  On the other hand, when the noise detection unit 32 determines that noise is generated because the signal level outside the desired frequency band is equal to or greater than the threshold, the noise detection unit 32 records the signal level (noise level) outside the desired frequency band. (Step 116), a signal indicating the occurrence of noise is supplied to the noise frequency / duration detector 34, and the noise level is supplied to the noise cancellation level determiner 36. The noise frequency / duration detection unit 34 detects a noise cycle that is a time interval when the noise level is equal to or higher than a threshold based on the timing at which a signal indicating the occurrence of noise is supplied from the noise detection unit 32, and the noise The duration of the state where the level is equal to or greater than the threshold is detected (step 118). Then, the detection information is supplied to the noise cancellation level determination unit 36.

  The noise cancellation level determination unit 36 grasps the noise level based on the signal from the noise detection unit 32 and the noise period and the noise duration based on the signal from the noise frequency / duration detection unit 34. Then, the nature of noise is detected. Then, based on the nature of the noise, the noise category, that is, the noise source that generated the noise is specified (step 120).

  For example, when the noise period is several kHz or more and there is not much fluctuation (variation) and there is little fluctuation in noise level, it is determined that the noise generation source is PWM switching drive. Further, when the noise period is several hundred Hz to several kHz, the fluctuation is relatively large, and the fluctuation of the noise level is also relatively large, it is determined that the noise generation source is a motor. Further, when the noise characteristics meet conditions other than those described above, it is determined that the noise generation source is an ignition system or a switch system.

  The noise cancellation level determination unit 36 stores a relationship between a predetermined noise generation source and an optimal noise cancellation process as shown in FIG. When the noise cancellation level determination unit 36 identifies the noise generation source as described above, the noise cancellation level determination unit 36 refers to the relationship between the noise generation source and the optimum noise cancellation processing, and performs noise removal corresponding to the specific noise generation source. Select the optimal noise cancellation process.

  For example, when the noise source is PWM switching drive, a signal (radio broadcast) of a noise source harmonic (for example, 520 kHz or 530 kHz when the noise period is 10 kHz) near the center frequency fd (for example, 522 kHz) of the desired wave. In this case, a process of attenuating (attenuating) the sound (hereinafter the same) and setting the operation time for the attenuation to a predetermined time (for example, a time of several tens of microseconds or less) is selected. Further, when the noise generation source is a motor, a process of attenuating a signal having a noise period (for example, 800 Hz to 1200 Hz) and setting an operation time for performing the attenuation to a predetermined time (for example, several tens of μsec or less) Select. Furthermore, when the noise source is an ignition system or a switch system, a signal in a range that does not affect the audibility is attenuated, and the operation time for performing the attenuation is a predetermined time longer than that of the above PWM or motor. A process to be set (for example, several milliseconds) is selected.

  Then, the noise cancellation level determination unit 36 performs the optimum noise cancellation processing selected as described above according to the nature of the noise, the noise generation source, and the input level of the desired wave within the desired frequency band from the input level detection unit 30. The noise canceller 40 is commanded to execute (step 122). In this case, the noise canceller 40 receives a command from the noise cancellation level determination unit 36 and processes a signal in the desired frequency band detected by the detection unit 38 in accordance with an optimal noise cancellation process. That is, the detection signal in the desired wave frequency band detected by the detection unit 38 is subjected to noise cancellation processing in the noise canceller 40 and output (step 124).

  For example, when the noise generation source is PWM switching drive, the noise source harmonic signal near the center frequency fd of the desired wave is attenuated for a predetermined time. When the noise generation source is a motor, the signal having the noise period is attenuated for a predetermined time.

  As described above, in the noise removing apparatus 10 of the present embodiment, the noise of the pulse characteristic is based on the signal level outside the desired frequency band (center frequency fd + Δf) different from the desired frequency band (center frequency fd) of the desired wave. Can be detected, that is, whether or not it has occurred.

  As described above, since the pulse noise is distributed over a wide band, it is also superimposed on the signal in the desired frequency band. However, since the peak power appears at a specific frequency for the desired wave in the desired frequency band, it is difficult for the noise component to be manifested in the desired frequency band, and a signal with the same frequency as the frequency at which the peak power of the desired wave appears is assumed. Even if it is used to detect noise, the extraction of the noise becomes difficult.

  In contrast, pulse noise is superimposed not only on the desired frequency band but also on signals outside the desired frequency band. The desired wave is at a low level outside the desired frequency band. In this respect, the noise component is likely to appear outside the desired frequency band. Therefore, if noise is detected using a signal outside the desired frequency band as in the present embodiment, it is accurately determined whether or not pulse noise is generated, and the level and frequency of the noise are further determined. , Properties such as duration can be extracted and detected with high accuracy.

  Further, in the noise removing apparatus 10 of the present embodiment, a noise generation source that generates noise is specified based on the characteristics of the noise extracted with high accuracy as described above, and an optimum noise corresponding to the specified noise generation source is specified. The cancellation process can be selected and determined according to the relationship shown in FIG. 5 stored in the noise cancellation level determination unit 36 in advance. Then, by executing the optimum noise cancellation processing according to the nature of the noise, the noise generation source, and the desired wave level, it is possible to remove the pulse noise superimposed on the desired wave from the signal within the desired frequency band. .

  According to such optimum noise cancellation processing, various types of pulse noise can be removed by a method corresponding to the property, and appropriate noise removal corresponding to the type of pulse noise can be performed. In this regard, according to the present embodiment, it is possible to extract and generate a desired wave that hardly superimposes noise from a signal in the desired frequency band, and to output the desired wave. It can be realized regardless of.

  In the first embodiment, the main receiving unit 20 is connected to the “main receiving unit” described in the claims, and the sub receiving unit 22 is connected to the “sub receiving unit” described in the claims. The detection unit 32 described in the claims “noise detection means”, the noise canceller 40 described in the claims “noise removal means”, and the noise cancellation level determination unit 36 described in the claims. Each corresponds to “noise generation source specifying means”.

  FIG. 6 shows a configuration diagram of a noise removing apparatus 100 according to the second embodiment of the present invention. The noise removing apparatus 100 according to the present embodiment is configured by removing the sub-receiving unit 22 from the noise removing apparatus 10 according to the first embodiment and forming a single receiving unit, and then performing a bandpass filter (BPF) for signal demodulation. ) And BPF for noise detection are provided with two different filters. In FIG. 6, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 6, the noise removal apparatus 100 includes a single reception unit (tuner) 104 that is a superheterodyne system or the like that constitutes the reception apparatus 102. The output of the RF unit 16 is supplied to the receiving unit 104 as a received signal. The receiving unit 104 has a mixer to which a local oscillation frequency fd is given so as to select a desired wave having a desired center frequency fd. The receiving unit 20 can receive a signal within the desired frequency band (center frequency fd) among the received signals from the RF unit 16, and filters the noise generated outside the desired desired wave band to obtain the desired signal. Adjust the wave gain.

  An IF unit 106 is connected to the receiving unit 104. The output of the receiving unit 104 is supplied to the IF unit 106. The IF unit 106 converts the signal in the desired frequency band from the receiving unit 104 to an intermediate frequency (for example, 10.7 MHz). A signal demodulation BPF 108 and a noise detection BPF 110 are connected to the IF unit 106. The output of the IF unit 106 is supplied to the signal demodulation BPF 108 and the noise detection BPF 110, respectively.

  The signal demodulation BPF 108 can pass a signal having a center frequency (for example, 10.7 MHz) for demodulating a desired wave with respect to the output of the IF unit 106. The noise detection BPF 110 is different from the center frequency (for example, 10.7 MHz) for demodulating the desired wave with respect to the output of the IF unit 106, and is a center for performing noise detection shifted from the center frequency by a predetermined frequency. It is possible to pass a signal of frequency. It should be noted that the predetermined frequency as the amount of deviation is not limited as long as it is possible to extract a frequency outside the desired frequency band and having a low input signal level (electric field strength) due to the desired wave from the received signal. That's fine.

  An input level detector 30 and a detector 38 are connected to the signal demodulation BPF 108. The input level detection unit 30 detects the input level (electric field strength) of the received signal based on the signal in the desired frequency band from the IF unit 106 that has passed through the signal demodulation BPF 108. The detection unit 38 detects a signal in the desired frequency band from the IF unit 106 that has passed through the signal demodulation BPF 108.

  A noise detection unit 32 is connected to the noise detection BPF 110. The noise detection unit 32 detects pulse noise based on a signal outside the desired frequency band from the IF unit 106 that has passed through the noise detection BPF 110, and specifically detects the level of the signal. And it is discriminate | determined whether the detected signal level is more than the threshold value which shows the boundary value of noise presence or absence.

  FIG. 7 shows a flowchart of an example of a control routine executed in the noise removal apparatus 100 of the present embodiment. In FIG. 7, steps for executing the same processing as the routine shown in FIG. 4 are given the same reference numerals and description thereof is omitted.

  That is, in the receiving device 102 including the noise removing device 100 of the present embodiment, the receiving unit 104 extracts the signal of the center frequency fd of the desired wave in the desired frequency band from the received signal from the RF unit 16 and outputs the signal. . The signal of the center frequency fd output from the receiving unit 104 is frequency-converted to an intermediate frequency by the IF unit 106 and then input to the signal demodulation BPF 108 and the noise detection BPF 110. The signal demodulation BPF 108 passes a signal having a center frequency (for example, 10.7 MHz) for demodulating a desired wave in the desired frequency band with respect to the output of the IF unit 106 (step 200).

  The signal output from the signal demodulation BPF 108 is input to the detector 38 and further input to the input level detector 30. Based on the signal from the main receiver 20, the input level detector 30 detects and records the input level (electric field strength) of the desired wave in the desired frequency band (step 102). The input level of the desired wave within the desired frequency band detected by the input level detection unit 30 is supplied to the noise cancellation level determination unit 36. The noise cancellation level determination unit 36 grasps the input level of the desired wave within the desired frequency band from the input level detection unit 30.

  In addition, the noise detection BPF 110 passes a signal having a center frequency for detecting noise from outside the desired frequency band, which is different from the center frequency for demodulating the desired wave, as described above, for the output of the IF unit 106 (step). 202). The signal output from the noise detection BPF 110 is input to the noise detection unit 32. The noise detection unit 32 detects the level of a signal outside the desired frequency band based on the signal from the noise detection BPF 110 every predetermined time (for example, several tens of milliseconds), and the level is determined as noise. It is determined whether or not the threshold value is greater than or equal to a threshold value indicating presence or absence, that is, whether or not noise is generated (step 112).

  As described above, in the noise removal apparatus 100 of the present embodiment, as in the noise removal apparatus 10 of the first embodiment, the desired wave band outside the desired frequency band (center frequency fd) is different from the desired frequency band (center frequency fd). Based on the level of the signal (fd + Δf), it is possible to detect pulse noise, that is, whether or not it occurs. Therefore, it is possible to accurately determine whether or not pulse noise is generated, and to further extract and detect properties such as noise level, frequency of occurrence, and duration.

  Further, in the noise removing apparatus 100 according to the present embodiment, a noise generation source that generates noise is specified based on the characteristics of noise extracted with high accuracy as described above, and an optimum noise corresponding to the specified noise generation source is specified. The cancellation process can be selected and determined according to the relationship shown in FIG. 5 stored in the noise cancellation level determination unit 36 in advance. Then, by executing the optimum noise cancellation processing according to the nature of the noise, the noise generation source, and the desired wave level, it is possible to remove the pulse noise superimposed on the desired wave from the signal within the desired frequency band. . Therefore, various types of pulse noise can be removed by a method according to the nature of the noise, and appropriate noise removal corresponding to the type of pulse noise can be performed. Therefore, it is possible to extract and generate a desired wave that hardly superimposes noise from this signal and to output it, and to generate a desired wave that hardly superimposes noise regardless of the type of the noise.

  Furthermore, the noise removing apparatus 100 of the present embodiment extracts the desired wave from the received signal and detects the noise, so that the noise removing apparatus of the first embodiment using the two receiving units 20 and 22 having different receiving bands is used. Unlike the apparatus 10, a single receiving unit 104 is used, and two filters of a signal demodulation BPF 108 that passes the frequency of the desired wave and a noise detection BPF 110 that passes a frequency other than the desired wave frequency are provided.

  For this reason, in the noise removal apparatus 100 of the present embodiment, the same function as that of the noise removal apparatus 10 of the first embodiment described above, that is, whether pulsating noise is generated, using only one receiver 104. It is possible to achieve accurate determination of whether or not, accurate extraction and detection of properties such as noise level, occurrence frequency, and duration, and optimum noise removal processing corresponding to the noise properties. In this regard, according to the noise removal apparatus 100 of the present embodiment, compared with the noise removal apparatus 10 of the first embodiment described above, the noise detection apparatus that controls noise resistance and the noise removal capacity are maintained while the apparatus itself is maintained. Simplification, miniaturization, and cost reduction are possible, and it is possible to avoid other receivers used for applications such as VICS and FM multiplexing being used for noise removal. It has become.

  In the second embodiment, the receiving unit 104 is included in the “receiving unit” described in the claims, the signal demodulation BPF 108 is included in the “main filter” described in the claims, and the noise detecting BPF 110. Corresponds to the “sub-filter” described in the claims.

  By the way, in said 1st and 2nd Example, although it is supposed that the noise removal apparatus 10 and 100 is applied to the receivers 12 and 102 which receive the broadcast mounted in the vehicle, this invention is limited to this. Rather than being a GPS receiver that receives GPS signals from GPS satellites, so-called smart / keyless receivers that receive signals transmitted from portable devices carried by vehicle users, and cellular phones carried by vehicle users. It is also possible to apply to a radio wave receiving system such as a Bluetooth receiver that receives a signal transmitted from the above, or an in-vehicle communication system that connects between in-vehicle electronic control units.

  Further, in the first and second embodiments described above, when it is detected that pulse noise superimposed on the desired wave is generated, noise cancellation processing for removing the noise from the signal in the desired frequency band However, after that, when it is determined that the generation of the noise is not detected and the noise is no longer generated, the noise canceling process may be stopped. In this case, the noise cancellation processing is executed so that the cancellation of the noise removal from the signal in the desired frequency band is gradually performed over time, for example, the attenuation coefficient for attenuating the signal is increased over time. It is also possible to gradually approach “1” which is non-attenuating.

  Furthermore, in the first and second embodiments described above, noise characteristics such as noise level, noise period, and noise duration are detected in identifying the noise category (noise source). For the detection, the relationship between the noise period and the frequency fd of the desired wave may be considered. For example, it may be considered whether the frequency fd of the desired wave is 1000 times or more with respect to the noise period. When the desired wave frequency fd is 1000 times or more of the noise period, the noise category is a motor system, and when the desired wave frequency fd is less than 1000 times the noise period, the noise category is a PWM system. It may be determined that there is.

It is a block diagram of the noise removal apparatus which is 1st Example of this invention. It is the figure which compared the noise and the desired wave. It is the figure which each represented the mode that a noise was superimposed on the signal in a desired frequency band, and the mode that a noise was superimposed on the signal outside a desired frequency band. It is a flowchart of an example of the main routine performed in the noise removal apparatus of a present Example. It is the table which prescribed | regulated the relationship between the noise property, the noise generation source, and the optimal noise cancellation process which removes noise. It is a block diagram of the noise removal apparatus which is 2nd Example of this invention. It is a flowchart of an example of the main routine performed in the noise removal apparatus of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100 Noise removal apparatus 12,102 Reception apparatus 20 Main reception part 22 Sub reception part 32 Noise detection part 34 Noise frequency / duration detection part 36 Noise cancellation level determination part 40 Noise cancellation process part (noise canceller)
104 Receiver 108 Signal demodulation BPF
110 BPF for noise detection

Claims (5)

A noise removing device for removing noise from a received signal,
A sub-reception unit that is provided separately from a main reception unit that receives a signal within a desired frequency band among received signals, and that receives a signal outside the desired frequency band among received signals;
Noise detecting means for detecting noise based on a signal outside the desired frequency band received by the sub-receiving means;
Noise removing means for removing noise superimposed on a signal in a desired frequency band received by the main receiving means based on noise detected by the noise detecting means;
A noise removing device comprising: A noise removing device for removing noise from a received signal,
A sub-filter that is provided separately from a main filter that extracts a signal in a desired frequency band from a received signal received by the receiving means, and that extracts a signal outside the desired frequency band from a received signal received by the receiving means;
Noise detecting means for detecting noise based on a signal outside the desired frequency band extracted by the sub-filter;
Noise removing means for removing noise superimposed on a signal in a desired frequency band received by the main receiving means based on noise detected by the noise detecting means;
A noise removing device comprising: Comprising noise generation source specifying means for specifying a noise generation source based on the nature of noise detected by the noise detection means;
3. The noise removing apparatus according to claim 1, wherein the noise removing unit removes the noise by a method according to a property of noise generated by the noise generating source specified by the noise generating source specifying unit.   4. The noise removing apparatus according to claim 3, wherein the noise generation source specifying unit specifies a noise generation source based on a frequency and duration of noise detected by the noise detection unit. A storage means for storing a relationship between a noise generation source and a technique for removing noise in advance is provided,
The noise removing unit removes the noise by a method according to a property of noise generated by the noise generation source specified by the noise generation source specifying unit, which is determined based on the relationship stored in the storage unit. The noise removing device according to claim 3 or 4, wherein

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