CN1476186A - Method of eliminating noise of digital audio frequency device during modulating signal - Google Patents
Method of eliminating noise of digital audio frequency device during modulating signal Download PDFInfo
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- CN1476186A CN1476186A CNA021345791A CN02134579A CN1476186A CN 1476186 A CN1476186 A CN 1476186A CN A021345791 A CNA021345791 A CN A021345791A CN 02134579 A CN02134579 A CN 02134579A CN 1476186 A CN1476186 A CN 1476186A
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Abstract
The device comprises tuner, PCM modulator, digital autio signal processor, low-pass filter, amplitron, loudspeaker, clock generator, frequency converter and controller. The method to clear off noise at time of signal modulation is as follows. The switch frequency of PWM digital autio conversion is regulated at least to the second high harmonic frequency when AM radio set broadcast frequency band is at receiving of synchronous tuning in order to let it not be contained in AM frequency band and to carry on down-regulation by using frequency which is lower than the set-switch frequency to effectively clear off its noise for exporting high quality of digital audio.
Description
(1) technical field
The method of the removing noise when the present invention relates to modulation signal in a kind of digital audio device, refer in particular to, when the channel signals that receives at broadcast receiver is varied to digital signal, the method for high-frequency noise being eliminated according to the audio modulation signal that frequency switching took place.
(2) background technology
Recently, the digital audio that picture is read from the CD of DVD or CD etc., as, after PCM (pulse modulation sign indicating number) digital audio modulation is PWM (pulse width modulation) digital audio, the PWM digital audio is carried out digital audio and video signals handle operation, the digital audio device that the digital audio of high tone quality is reproduced output with expectation develops and commercialization.
Referring to Fig. 1, shown in Figure 1 is the structure chart of existing digital audio device.
The device of Fig. 1 comprises: will adjust the tuner 10 of reception by the radio receiver signal that antenna receives, will be transformed to A/D by the radio receiver signal that above-mentioned tuner is adjusted reception; By PCM modulator 11 above-mentioned signal is become pcm digital audio signal; Described pcm digital audio signal is carried out with the PWM digital audio modulation be modulated into the PWM digital audio and video signals after the Digital Signal Processing operation of relevant PWM digital audio through digital audio signal processor 12 again; The digital signal of described PWM digital audio is passed through low pass filter 15 with the digital audio of audio band; The digital audio that above-mentioned filtered device 15 filtering are passed through is carried out the amplifier 16 of amplification; Above-mentioned signal by amplification is outputed to loud speaker, export with sound transmission; Decide the clock generator 14 of the clock pulse of frequency for taking place; Decide the frequency clock impulse transfer and be frequency changer 13 above-mentioned with the clock of the necessary switching frequency of said PWM digital audio modulation; Produce the controller 18 of operation but also be included as control with above-mentioned each parts.
Then, possess the user of above-mentioned digital audio-frequency apparatus, select to specify own channel of being ready,, operate and control above-mentioned tuner at above-mentioned controller 18, can the tuning broadcast receiver broadcast channel that receives user's appointment.
Adjust the radio channels of reception by tuner 10, as the AM audio frequency by the reception of AM (amplitude modulation) broadcast receiver frequency band is according to above-mentioned PCM modulator 11A/D frequency conversion, and with the output of PCM digital audio, above-mentioned PCM digital audio becomes the PWM digital audio and video signals through digital audio signal processor 12 with the conversion of PWM digital audio and by Digital Signal Processing.
At this moment, be to consider its audio frequency with the clock frequency of the switching frequency of said PWM digital conversion, in the value between 300KHz and 400KHz, as, get 384KHz.
Is with after the screening of 20KHz audio frequency by said process according to above-mentioned low pass filter 15 by the digital audio of PWM conversion and Digital Signal Processing, because by the voice output of above-mentioned amplifier 16 and loud speaker 17, so the user can listen to the music of AM broadcast receiver broadcasting channel with high tone quality.
But, in the general digital audio device that constitutes aforesaid operations, the clock frequency that is output by said frequencies converter 13, promptly, because for the conversion of PWM digital audio, fixed with the high frequency (FS) of 384KHz toward the switching frequency that above-mentioned digital audio signal processor 12 is introduced, see shown in Figure 2, shown in Figure 2 is the spectrogram of the noise frequency switch on existing digital audio device, the 2nd higher harmonics (2FS) of 768KHz frequency band and the 3rd higher harmonics (3FS) of 1152KHz frequency band etc., all be present in the above AM broadcast receiver of 522KHz and broadcast in the frequency band of radio frequency channel, so be carried out the problem that exists the severe noise effect in the AM radio receiver signal polyphony process that receives of adjusting at above-mentioned tuner 10.
(3) summary of the invention
The present invention creates in order to solve the above-mentioned problem of putting forward, at digital audio device, during with the tuning reception of AM radio channels, for the switching frequency of conversion PWM digital audio at least till the frequency of the 2nd higher harmonics (2FS), in order not allow it be included in above-mentioned AM frequency band, use during adjusting more in advance than the low frequency of switching frequency that is provided with and reduce, provide a kind of for removing the method for noise in removing when the digital audio device modulation signal by the digital audio device of the caused high-frequency noise of switching frequency effectively during modulation signal.
To achieve the above object, the method for removing noise in the digital audio device of the present invention during modulation signal is:
Wherein said digital audio device comprises that digital audio device comprises tuner, PCM modulator, digital audio signal processor, low pass filter, amplifier, loud speaker, clock generator, frequency changer and controller is characterized in that the method for described removing noise comprises the following steps:
Step 2, the used frequency band of user is selected;
Step 3 is confirmed the tuner signal simultaneous tuning frequency band of having set;
Step 4, the tuning frequency band of confirming according to step 3, the switching frequency in the time of will being modulated to the pulse width modulation (PWM) audio frequency from the pulse modulation data pcm audio of the received signals of described PCM modulator output carries out variable adjustment;
Step 5 is modulated to the PWM audio frequency with pcm audio.
Effect of the present invention: digital audio device of the present invention is removed the noise method when modulation signal be when AM (amplitude modulation) broadcast receiver is broadcast frequency band simultaneous tuning reception, to till the frequency of the 2nd higher harmonics, not allow it be included in the AM frequency band at least with the switching frequency of PWM digital audio conversion, and reduce with the frequency lower than decided switching frequency, the high-frequency noise that switching frequency produced is removed its noise effectively in AM radio receiver signal polyphony process, export the digital audio of high tone quality with this, the present invention is the of great value invention of part.
For further specifying above-mentioned purpose of the present invention, design feature and effect, the present invention is described in detail below with reference to accompanying drawing.
(4) description of drawings
Shown in Figure 1 is the structure chart of existing digital audio device;
Shown in Figure 2 is the spectrogram of the switching frequency noise on existing digital audio device;
Be adapted to remove the structure chart of the digital audio device of noise method during shown in Figure 3 is modulation signal of the present invention;
Remove the flow chart of noise method during shown in Figure 4 is modulation signal of the present invention;
The spectrogram of the switching frequency noise on the device of the method according to this invention that shown in Figure 5 is.
(5) embodiment
Below be an embodiment who removes the method for noise in the digital audio device of the present invention during modulation signal, be elaborated with reference to accompanying drawing.
Referring to Fig. 3, simultaneously also referring to Fig. 1 (what the parts label was identical with parts label among Fig. 1 among Fig. 3 is same parts), the removing noise method during shown in Figure 3 is according to the present invention modulation signal, the digital audio device of formation, this device comprises:
The connection of above-mentioned each parts is about basic identical with Fig. 1, and utilize the controller 18 described in the embodiment device of the inventive method, the described frequency changer 13 of operation control, the switch of introducing in digital audio signal processor 12 is carried out variable adjustment, when FM (frequency modulation) broadcast receiver is broadcast the tuning reception of frequency band, the switching frequency that maintains 384 KHz that have been set up in the switching frequency of described digital audio signal processor 12 will be introduced, when AM broadcast receiver broadcasting frequency band is carried out tuning reception, with introducing, reduce with the 196KHz switching frequency in the switching frequency of above-mentioned digital audio signal processor 12.
Then, frequency (3FS) according to the 3rd higher harmonics of the frequency (2FS) of the 2nd higher harmonics of the 768KHz frequency band of the switching frequency of 384KHz and 1152KHz frequency band is present in the above AM broadcast receiver broadcast channel of 522KHz, can prevent that it from noise phenomenon occurring the polyphony process of the AM radio receiver signal that receives from above-mentioned tuner 10 simultaneous tunings.The method of such switch audio frequency being removed noise is described in detail as follows.
During shown in Figure 4 is according to the present invention relevant digital audio device modulation signal, remove the operational flowchart of noise method, step following (simultaneously referring to Fig. 3):
S10 according to user's operation keys input, is provided with present mode of operation in described controller 18 with the broadcast receiver receive mode;
When S11, user import the broadcast receiver broadcast channel of extraordinary frequency, control 10 operations of described tuner, and receive radio receiver signal according to the channel simultaneous tuning of user's selection;
S12, the frequency tuning frequency band of the broadcast receiver broadcast channel that is provided with according to above-mentioned user's needs is identified the frequency band that whether is suitable for AM broadcast receiver broadcast channel;
S13, the affirmation result of above-mentioned S12, be when being suitable for the frequency band of AM broadcast receiver broadcasting, operation control frequency converter 13 in described controller 18, for with the conversion of PCM numerical frequency, the switching frequency that is incorporated in numerical frequency signal processor 12 is lowered to 196KHz (384KHz/2) from 384KHz;
S14, the affirmation result of above-mentioned S12, it or not the frequency band that is suitable for AM broadcast receiver broadcasting channel (Channel), promptly, but be suitable for the situation of the high frequency band of FM broadcasting channel (Channel) frequency band, in above-mentioned controller 18, for the conversion of PWM digital audio, with the switching frequency of introducing described digital audio signal processor 12 still keep specific 384KHz;
S15, after the switching frequency of the described digital audio signal processor 12 of the introducing of above-mentioned S12 or S13 mixed up, the PCM digital audio of according to above-mentioned PCM modulator 11 the A/D conversion in described digital audio signal processor 12 utilized described switching frequency to modulate with the PWM digital audio;
S16 carries out signal processing with the PCM digital audio of that modulation with digital audio;
S17 passes through described amplifier 16 and loud speaker 17 with digital audio and video signals by the digital audio of described low pass filter 15 filtered voiced bands, with voice output.
Clock frequency by 13 outputs of said frequencies converter, be with the conversion of PWM digital audio, be incorporated in the switching frequency of above-mentioned digital audio signal processor 12, timing under frequency (FS) direction of 196KHz, as shown in Figure 5, the frequency (2FS) of the 2nd higher harmonics of 384KHz channel is not present in the frequency band of the above AM broadcast receiver broadcasting channel of 522KHz.
Has only the 588KHz frequency band, the frequency (3FS) of the 3rd faint higher harmonics is present in the frequency band of the above AM broadcast receiver broadcast channel of 522KHz, can prevent the effect of its caused noise the AM radio receiver signal polyphony process that receives synchronously from described tuner 10.
Those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating the present invention, and be not to be used as limitation of the invention, as long as in connotation scope of the present invention, all will drop in the scope of claims of the present invention variation, the modification of the above embodiment.
Claims (5)
1, the method for the removing noise during modulation signal in a kind of digital audio device, described digital audio device comprises tuner, the PCM modulator, digital audio signal processor, low pass filter, amplifier, loud speaker, clock generator, frequency changer and controller is characterized in that the method for described removing noise comprises the following steps:
Step 1, described tuner receive mode is provided with;
Step 2, the used frequency band of user is selected;
Step 3 is confirmed the tuner signal simultaneous tuning frequency band of having set;
Step 4, the tuning frequency band of confirming according to step 3, the switching frequency in the time of will being modulated to the pulse width modulation (PWM) audio frequency from the pulse modulation data pcm audio of the received signals of described PCM modulator output carries out variable adjustment;
Step 5 is modulated to the PWM audio frequency with pcm audio.
2, the method for the removing noise during modulation signal in the digital audio device as claimed in claim 1 is characterized in that the simultaneous tuning frequency band in the described step 3 is meant AM (amplitude modulation) or FM (frequency modulation) frequency band.
3, the method for the removing noise during modulation signal in the digital audio device as claimed in claim 1, it is characterized in that in the described step 4 that when the tuning frequency band that is identified was AM (amplitude modulation) frequency band, the adjusting of switching frequency was the frequency downconverts with 1/2 value of the switching frequency of apparatus settings.
4, the method for the removing noise during modulation signal in the digital audio device as claimed in claim 3 is characterized in that 1/2 value of the switching frequency of described apparatus settings is, with at least till the 2nd higher harmonic frequencies, does not allow it be included in the AM frequency band in design.
5, the method for the removing noise during modulation signal in the digital audio device as claimed in claim 3 is characterized in that the switching frequency of described apparatus settings is meant the value that possesses between 300KHz～400KHz.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 02134579 CN1219368C (en) | 2002-08-16 | 2002-08-16 | Method of eliminating noise of digital audio frequency device during modulating signal |
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| CN 02134579 CN1219368C (en) | 2002-08-16 | 2002-08-16 | Method of eliminating noise of digital audio frequency device during modulating signal |
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| CN1476186A true CN1476186A (en) | 2004-02-18 |
| CN1219368C CN1219368C (en) | 2005-09-14 |
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| CN 02134579 Expired - Fee Related CN1219368C (en) | 2002-08-16 | 2002-08-16 | Method of eliminating noise of digital audio frequency device during modulating signal |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100586034C (en) * | 2005-08-29 | 2010-01-27 | 索尼株式会社 | Electronic device |
| CN1750573B (en) * | 2004-09-03 | 2015-12-02 | 纽昂斯通讯公司 | Adopt the noise decrease of combination and the Speech processing of echo cancellation |
| WO2024040621A1 (en) * | 2022-08-24 | 2024-02-29 | 深圳市江楠实业有限公司 | Method and system for adaptively adjusting frequency of switching power source, and electronic device |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI505661B (en) * | 2013-09-09 | 2015-10-21 | Elite Semiconductor Esmt | Amplitude modulation interference avoidance method, device, and amplitude modulation receiver |
-
2002
- 2002-08-16 CN CN 02134579 patent/CN1219368C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1750573B (en) * | 2004-09-03 | 2015-12-02 | 纽昂斯通讯公司 | Adopt the noise decrease of combination and the Speech processing of echo cancellation |
| CN100586034C (en) * | 2005-08-29 | 2010-01-27 | 索尼株式会社 | Electronic device |
| WO2024040621A1 (en) * | 2022-08-24 | 2024-02-29 | 深圳市江楠实业有限公司 | Method and system for adaptively adjusting frequency of switching power source, and electronic device |
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| Publication number | Publication date |
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| CN1219368C (en) | 2005-09-14 |
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