CN105530018B - The extended threshold system and method for digital FM receiver - Google Patents
The extended threshold system and method for digital FM receiver Download PDFInfo
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- CN105530018B CN105530018B CN201610045949.2A CN201610045949A CN105530018B CN 105530018 B CN105530018 B CN 105530018B CN 201610045949 A CN201610045949 A CN 201610045949A CN 105530018 B CN105530018 B CN 105530018B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
- H04B1/1036—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
- H04B2001/1054—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal by changing bandwidth
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Abstract
The present invention provides the extended threshold system and method for digital FM receiver, and the system includes analog front-end module, frequency mixing module, the first filtration module, extended threshold module and demodulation module；Wherein, extended threshold module carries out the first filtering signal to postpone to obtain the first postpones signal including the first Postponement module；First postpones signal is carried out frequency spectrum shift and obtains first moving signal by the first frequency spectrum shift module；Second filtration module is moved first signal and is filtered；Second frequency spectrum shift module is moved filtered first signal and is moved to origin-location and obtains extended threshold signal；Computing module receives the first filtering signal and is calculated the signal that counts according to the first filtering signal, and computing module exports the signal to the first frequency spectrum shift module and the second Postponement module that counts.The method is the method for being applied to said system.The present invention can filter more carrier noises, improve the signal to noise ratio of demodulated signal, and will not cause audio distortions.
Description
Technical field
The invention belongs to frequency-shift keying field, and in particular to a kind of tune for digital demodulation shape such as stereo broadcasting signal
The method and apparatus of frequency signal, more particularly to frequency-shift keying（FM）The extended threshold system and method for receiver.
Background technology
The purpose of FM receivers is according to the radio signal for receivingTo restore modulated signals.Frequently
The carrier signal of rate modulation is expressed as
WhereinIt is carrier frequency；D is warble rate, generally 75KHz；It is modulated signals.
The structured flowchart of common digital FM receivers is as shown in figure 1, the FM signals that will receive of analog front-end module 1 at present
RF（Radio Frequency：Radio frequency）It is converted to intermediate frequency（Intermediate Frequency：Intermediate frequency）And
IQ two paths of signals is obtained after filtering, then intermediate-freuqncy signal is sampled by analog-to-digital conversion module 2, then use bandpass filtering modules block
3, i.e. digital band-pass filter RFBPF（Intermediate Frequency Band-Pass Filter）It is filtered,
RFBPF is the complex bandpass filters of the frequency centered on RF, in general, the stereophonic signal of 75KHz modulation degree,
Bandwidth be about ± 100KHz, so in order to ensure that sound is undistorted, the bandwidth of intermediate-frequency filter can not be less than ± 100KHz.
Then it is mixed with frequency mixing module 4 again, is eventually passed the demodulation that demodulation module 5 completes FM signals, demodulation module 5 is CORDIC
（A kind of cartesian coordinate is transformed into polar algorithm）And differential circuit.But when the signal to noise ratio of the carrier signal for receiving is in FM
When below signalc threshold, the signal to noise ratio of FM demodulated signals can drastically deteriorate, so as to cause sensitivity to decline.Therefore thresholding is needed to expand
Art is given full play to one's skill to improve the sensitivity of digital FM receiver.
In the prior art, the method for the signal to noise ratio of common raising FM demodulated signals has following several:
1. reduce modulation degree, reduce signal bandwidth, such that it is able to filter more carrier noises using narrower RFBPF,
So as to improve demodulated signal signal to noise ratio, such as FMFB；But due to reducing modulation degree, the effect of this method is simultaneously bad.
2. as mentioned in the Chinese invention patent application of Publication No. CN1115833 by detecting and removing demodulated signal
Phase jump, so as to improve demodulated signal signal to noise ratio；But this method can only detect the transition of a part, even and if inspection
Measure transition can only also weaken transition can not the correct signal of accurate reproduction, the signal to noise ratio of demodulated signal improves limited.
3. such as the use bandwidth varying mentioned in the Chinese invention patent application of Publication No. CN101420239 and variable decline
The RFBPF for subtracting slope carrys out the different carrier signal to noise ratio of self adaptation, it is to avoid more carrier waves are filtered on the premise of causing audio distortions
Noise, so as to improve demodulated signal signal to noise ratio；But because sound to be avoided is undistorted, so the bandwidth of RFBPF is in reduction
The attenuation slope of RFBPF will also become more slow simultaneously, therefore the final raising to sensitivity is simultaneously little.
The content of the invention
The main object of the present invention is to provide a kind of extended threshold system of digital FM receiver.
It is a further object of the present invention to provide a kind of extended threshold method of digital FM receiver.
To realize above-mentioned main purpose, the extended threshold system of the digital FM receiver that the present invention is provided includes simulation
Front-end module, analog-to-digital conversion module, frequency mixing module, the first filtration module, extended threshold module and demodulation module；AFE(analog front end)
Module receives FM signals and is intermediate-freuqncy signal by FM signal frequency conversions, and analog front-end module exports intermediate-freuqncy signal to analog-to-digital conversion mould
Block；Intermediate-freuqncy signal is carried out analog-to-digital conversion and obtains data signal by analog-to-digital conversion module, and analog-to-digital conversion module output digit signals are extremely
Frequency mixing module；Data signal is mixed to direct current and obtains mixed frequency signal by frequency mixing module, and frequency mixing module exports mixed frequency signal to first
Filtration module；The noise and mirror image that first filtration module filters mixed frequency signal obtain the first filtering signal, and the first filtration module is defeated
Go out the first filtering signal to extended threshold module；The thresholding that extended threshold module extends the first filtering signal is worth to extended threshold
Signal, extended threshold module exports extended threshold signal to demodulation module；Demodulation module demodulation threshold extension signal is demodulated
Signal；Wherein, extended threshold module includes the first Postponement module, the first frequency spectrum shift module, the second filtration module, the second frequency spectrum
Move module and computing module；First Postponement module carries out the first filtering signal to postpone to obtain the first postpones signal, first
Postponement module exports the first postpones signal to the first frequency spectrum shift module；First frequency spectrum shift module carries out the first postpones signal
Frequency spectrum shift obtains first and moves signal, and signal to the second filtration module is moved in the first frequency spectrum shift module output first；Second
Filtration module is moved first signal and is filtered, and signal to the second frequency spectrum is moved in the second filtration module output filtered first
Move module；Second frequency spectrum shift module by filtered first move signal move to origin-location obtain extended threshold letter
Number；Computing module receives the first filtering signal and is calculated the signal that counts, computing module output according to the first filtering signal
Count signal to the first frequency spectrum shift module and the second Postponement module.
From such scheme, the extended threshold module that the present invention is provided is a kind of wink that can accurately track carrier signal
When frequency and narrow bandwidth CTLPF（Carrier Tracking Low Pass Filter：Carrier track formula low pass filter）
To filter more carrier noises, so as to improve the signal to noise ratio of demodulated signal, and audio distortions will not be caused.
One preferred scheme is that extended threshold module includes the second Postponement module, and the second Postponement module receives the signal that counts
The second postpones signal, the second Postponement module output the second postpones signal to the second frequency spectrum shift module are obtained after being postponed.
Therefore, the first Postponement module introduces group delay in the second filtration module；Second Postponement module is compensated second
The group delay that filtration module is introduced.The IQ two paths of signals of the first filtering signal postpones by the first Postponement module, IQ two paths of signals
Sampling number be the second filtration module group delay, so as to guarantee the instantaneous frequency of accurate tracking carrier wave, and afterwards
Group delay can be compensated by the second Postponement module.
One preferred scheme is that computing module includes derivative module, pulse cancellation module, the 3rd filtration module and just
There is module in cosine signal；Derivative module receives and states the first filtering signal and by the first filtering signal process obtaining differential
Signal, derivative module exports differential signal to pulse cancellation module；The disturbing pulse that pulse cancellation module eliminates differential signal is obtained
Signal is eliminated to pulse, the output pulse of pulse cancellation module eliminates signal to the 3rd filtration module；3rd filtration module filters arteries and veins
The noise that punching eliminates signal obtains the 3rd filtering signal, and the 3rd filtration module exports the 3rd filtering signal to cosine and sine signal to be occurred
Module；There is module and be calculated the signal that counts according to the 3rd filtering signal in cosine and sine signal, it is defeated that cosine and sine signal occurs module
Go out to count signal to the first frequency spectrum shift module and the second Postponement module.
Therefore, computing module exports the signal to the first frequency spectrum shift module and the second Postponement module that counts, and is used for
Calculate the shifting frequency of the first frequency spectrum shift module and the shifting frequency of the second frequency spectrum shift module.
One preferred scheme is that pulse cancellation module includes judge module, multi-path choice module and the 3rd delay mould
Whether block, contrast module is used to contrast default maximum more than or equal to the differential signal being input into；Multi-path choice module is used
In the pulse elimination signal according to the selection output of the result of contrast module；3rd Postponement module is used for storage pulse and eliminates signal.
Therefore, pulse cancellation module is compared by by the differential signal of input with default maximum, judges
Whether the intermediate-freuqncy signal of input is normal signal, so that selectively output pulse eliminates signal.
One preferred scheme is that the signal that counts counts signal and cosine counts signal including sine.
Therefore, the cosine and sine signal of computing module occur module by calculating respectively obtain sine count signal and
Cosine counts signal, and exports respectively to the first frequency spectrum shift module and the second Postponement module.
To realize above-mentioned another object, the extended threshold method of the digital FM receiver that the present invention is provided includes simulation
Front end procedure, receive FM signals and by FM signal frequency conversions be intermediate-freuqncy signal；Analog-to-digital conversion step, modulus is carried out by intermediate-freuqncy signal
It is converted to data signal；Frequency mixing stages, are mixed to data signal direct current and obtain mixed frequency signal；First filter step, filters
The noise and mirror image of mixed frequency signal obtain the first filtering signal；Extended threshold step, the threshold value for extending the first filtering signal is obtained
To extended threshold signal；Demodulation step, demodulation threshold extension signal obtains demodulated signal；Wherein, extended threshold step is wrapped successively
Include the first delay step, the first frequency spectrum shift step, the second filter step, the second frequency spectrum shift step and calculation procedure；The
One delay step is to carry out the first filtering signal to postpone the step of obtaining the first postpones signal；First frequency spectrum shift step be by
First postpones signal carries out the step of obtaining first and move signal of frequency spectrum shift；Second filter step is to move signal by first
The step of being filtered；Second frequency spectrum shift step is to move signal by filtered first and move to origin-location to obtain thresholding
The step of extension signal；Calculation procedure for the first filtering signal of reception and is calculated the signal that counts according to the first filtering signal
The step of.
From such scheme, intermediate-freuqncy signal of the extended threshold method of the invention after to mixing and filtering carries out frequency spectrum
Move and realize carrier track, the centre frequency required for intermediate-freuqncy signal is moved into direct current first, then with fixed low pass filtered
Ripple device is filtered, and completes to carry out an equal amount of frequency translation toward rightabout again after filtering to reduce intermediate-freuqncy signal.
Brief description of the drawings
Fig. 1 is the structured flowchart of existing digital FM receiver embodiment.
Fig. 2 is the structured flowchart of the extended threshold system embodiment of digital FM receiver of the present invention.
Fig. 3 be digital FM receiver of the present invention extended threshold system embodiment in extended threshold module structural frames
Figure.
Fig. 4 be digital FM receiver of the present invention extended threshold system embodiment in extended threshold module pulse eliminate
The structured flowchart of module.
Fig. 5 is the method flow diagram of the extended threshold embodiment of the method for digital FM receiver of the present invention.
Below in conjunction with drawings and Examples, the invention will be further described.
Specific embodiment
Referring to Fig. 2, Fig. 2 is the structured flowchart of the extended threshold system embodiment of digital FM receiver of the present invention.This hair
Bright extended threshold system include analog front-end module 11, analog-to-digital conversion module 12, frequency mixing module 13, the first filtration module 14,
Extended threshold module 15 and demodulation module 16.
Analog front-end module 11 is used to receive FM signals and the carrier frequency of the FM signals of reception is converted into intermediate frequency,
Generation intermediate-freuqncy signal；Analog-to-digital conversion module 12 obtains data signal for intermediate-freuqncy signal to be carried out into analog-to-digital conversion；Frequency mixing module 13,
I.e. complex mixer, mixed frequency signal is obtained for data signal to be mixed into direct current；First filtration module 14, i.e. FIRLPF low passes
Wave filter, noise and mirror image for filtering mixed frequency signal obtain the first filtering signal, wherein using LPF instead of the good of RFBPF
Place is without complex filter；The thresholding that extended threshold module 15 is used to extend the first filtering signal is worth to extended threshold letter
Number；Demodulation module 16 is used for demodulation threshold extension signal and obtains demodulated signal, particularly by cordic algorithm and differential electricity
Rood is to final demodulated signal.Cordic algorithm is transformed into polar algorithm for a kind of cartesian coordinate.
The purpose of the present invention is the signal to noise ratio of the demodulated signal for improving carrier signal to noise ratio below FM signalc thresholds.With it is existing
Technology is compared, it is not necessary to reduce modulation degree, will not cause audio distortions, and the signal to noise ratio of demodulated signal is higher.Realization principle is as follows：
If the expression formula of warbled carrier signal is：
WhereinIt is carrier frequency；D is warble rate, generally 75KHz；It is modulated signals.Assuming that, then the instantaneous frequency of carrier signal be：
By above formula it is recognised that the instantaneous frequency of carrier signal be byInstantaneous voltage determine.And becauseInstantaneous voltage change will not be too fast, therefore carrier signal instant bandwidthThan the total bandwidth that carrier signal is occupiedIt is narrow.
Therefore, the present invention provide extended threshold module 15 be a kind of instantaneous frequency that can accurately track carrier signal and
Bandwidth only hasCTLPF（Carrier Tracking Low Pass Filter：Carrier track formula low pass filter）, lead to
Cross CTLPF to filter more carrier noises, so as to improve the signal to noise ratio of demodulated signal, and audio distortions will not be caused.Will
Carrier track is realized, then needs to change the centre frequency of wave filter, be numerically difficult to realize.A kind of preferably implementation method is right
Signal carries out frequency spectrum shift.Centre frequency required for signal is moved into direct current, is then entered with fixed low pass filter again
Row filtering, carries out an equal amount of frequency translation and carrys out recovering signal toward rightabout again after completion filtering.
With reference to Fig. 3, Fig. 3 be digital FM receiver of the present invention extended threshold system embodiment in extended threshold module 15
Structured flowchart.Extended threshold module 15 includes the first Postponement module 51, the first frequency spectrum shift module 52, the second filtration module
53rd, the second frequency spectrum shift module 54, the second Postponement module 55 and computing module 25.
Digital FM receiver of the invention is quadrature receiver, that is, received by digital FM receiver antenna
FM signals can immediately be divided into two channels, and one is same phase (I) channel, and another is orthogonal (Q) channel.First filtering signal point
For IQ two paths of signals accesses extended threshold module 15, first the first postpones signal, first are obtained respectively through the first Postponement module 51
The IQ two paths of signals of filtering signal is equal to the group delay of the second filtration module 53 by the sampled point quantity for postponing, and this is to protect
Card is capable of the instantaneous frequency of accurate tracking carrier wave.
Then, the IQ two paths of signals of the first postpones signal reaches the first frequency spectrum shift module 52, carries out frequency spectrum shift and obtains
First moves signal, and the frequency of frequency spectrum shift is determined by the instantaneous frequency of carrier wave, the corresponding sine values of this instantaneous frequency and
There is module 59 and be calculated in cosine values, by cosine and sine signal wherein the first frequency spectrum shift module 52 is complex mixer.
The first IQ two paths of signals for moving signal arrives separately at the second filtration module 53, and the second filtration module 53 includes two
The IQ two paths of signals that independent FIR low pass filter moves signal to first respectively is filtered, the second filtration module 53 it is logical
Frequency band can be with according to whether switch for monophonic between 15KHz and 53KHz.
The second frequency spectrum shift module 54 of the filtered first IQ two paths of signals for moving signal and then arrival, the frequency moved
There is module 59 and be calculated in size, and introduced by the first Postponement module 51 of compensation of the second Postponement module 55 by cosine and sine signal
The group delay of the second filtration module 53, the frequency spectrum of the IQ two paths of signals for moving signal by filtered first reverts to correct position
Put and obtain extended threshold signal, the IQ two paths of signals for then exporting extended threshold signal is used to outside for demodulation module 16,
Wherein the second frequency spectrum shift module 54 is complex mixer.
The shifting frequency of the first frequency spectrum shift module 52 as described above and the shifting frequency of the second spectrum block 54 are by counting
Module 25 is calculated to be calculated.Wherein, computing module 25 includes derivative module 56, pulse cancellation module 57, the 3rd filtration module 58
And cosine and sine signal occurs module 59, calculating process is as follows：
The IQ two paths of signals of the first filtering signal of input after derivative module 56 by obtaining differential signal, wherein differential
Module is specially CORDIC and differential circuit, and pulse cancellation module 57 is reached afterwards.With reference to Fig. 4, Fig. 4 is frequency-shift keying of the present invention
The structured flowchart of the pulse cancellation module 57 of extended threshold module 15 in the extended threshold system embodiment of receiver.Pulse is eliminated
Module 57 includes contrast module 571, the Postponement module 573 of multi-path choice module 572 and the 3rd, and wherein contrast module 571 is used for
The default maximum of program is compared with the differential signal of input, whether the default maximum of determining program is more than or equal to
Input signal, 1 is exported when being judged as YES, and the differential signal for now thinking input is normal signal, and multi-path choice module 572 is selected
Select the differential signal of the current input of output；0 is exported when being judged as NO, now thinks that the differential signal of input is an interference arteries and veins
Punching, the differential signal of the previous output that selection the 3rd Postponement module of output of multi-path choice module 572 is preserved, i.e., as normal letter
Number output differential signal will be buffered in the 3rd Postponement module 573.
The referred to as pulse of pulse cancellation module 57 is exported differential signal herein eliminates signal, and pulse eliminates signal input
3rd filtration module 58 carries out LPF, wherein the passband of the 3rd filtration module 58 can with according to whether for monophonic
Switched between 15KHz and 53KHz.Pulse obtains the 3rd filtering signal after eliminating signal filtering, and the 3rd filtration module 58 will
3rd filtering signal input sine and cosine signal generating module 59 carries out accumulation calculating and obtains the signal that counts, specific computing formula
It is as follows, i.e., accumulated value, then the sine value and cosine value for calculating accumulated value first are calculated to the 3rd filtering signal being input into：
Obtain that sine counts signal and cosine counts signal, then sine counted into signal respectively and cosine counts signal output
To the first frequency spectrum shift module 52 and the second Postponement module 55, the first frequency spectrum shift module 52 and the second frequency spectrum shift are finally given
The frequency spectrum shift frequency of module 54.
Referring to Fig. 5, Fig. 5 is the method flow diagram of the extended threshold embodiment of the method for digital FM receiver of the present invention.It is first
Step S1 is first carried out, the RF radio of the FM signals of reception is converted to intermediate frequency and obtains intermediate frequency by analog front-end module 11（IF）
Signal, post filtering obtain IQ two paths of signals；Then step S2 is performed, analog-to-digital conversion module 12 carries out mould to if signal sampling
Number is converted to data signal；Step S3 is performed, data signal is mixed to by direct current by frequency mixing module 13, i.e. complex mixer
Obtain mixed frequency signal；Step S4 is performed afterwards, and making an uproar for mixed frequency signal is filtered by filtration module 14, i.e. FIRLPF low pass filters
Sound and mirror image obtain filtering signal；Step S5 is performed, using extended threshold module 15, i.e. CTLPF（Carrier Tracking
Low Pass Filter：Carrier track formula low pass filter）Frequency spectrum shift is carried out to filtering signal to be obtained so as to realize extended threshold
To extended threshold signal；Step S6 is finally performed, by demodulation module 16, i.e., is obtained most by cordic algorithm and differential circuit
The demodulated signal of whole FM signals.
Therefore, extended threshold module of the invention is a kind of instantaneous frequency and band that can accurately track carrier signal
The CTLPF of width（Carrier Tracking Low Pass Filter：Carrier track formula low pass filter）, by CTLPF
More carrier noises can be filtered, so as to improve the signal to noise ratio of demodulated signal, and audio distortions will not be caused.
Claims (10)
1. the extended threshold system of digital FM receiver, including analog front-end module, analog-to-digital conversion module, frequency mixing module,
One filtration module, extended threshold module and demodulation module；
The analog front-end module receives FM signals and is intermediate-freuqncy signal by the FM signal frequency conversions, and the analog front-end module is defeated
Go out the intermediate-freuqncy signal to the analog-to-digital conversion module；
The intermediate-freuqncy signal is carried out analog-to-digital conversion and obtains data signal by the analog-to-digital conversion module, and the analog-to-digital conversion module is defeated
Go out the data signal to the frequency mixing module；
The data signal is mixed to direct current and obtains mixed frequency signal by the frequency mixing module, and the frequency mixing module exports the mixing
Signal is to first filtration module；
The noise and mirror image that first filtration module filters the mixed frequency signal obtain the first filtering signal, first filtering
Module exports first filtering signal to the extended threshold module；
The thresholding that the extended threshold module extends first filtering signal is worth to extended threshold signal, the extended threshold
Module exports the extended threshold signal to the demodulation module；
The demodulation module demodulates the extended threshold signal and obtains demodulated signal；
It is characterized in that：
The extended threshold module includes the first Postponement module, the second Postponement module, the first frequency spectrum shift module, the second filtering mould
Block, the second frequency spectrum shift module and computing module；
First Postponement module carries out first filtering signal to postpone to obtain the first postpones signal, and described first postpones mould
Block exports first postpones signal to the first frequency spectrum shift module；
First postpones signal is carried out frequency spectrum shift and obtains first moving signal, described by the first frequency spectrum shift module
Signal to second filtration module is moved in one frequency spectrum shift module output described first；
Second filtration module is moved described first signal and is filtered, and second filtration module exports filtered institute
State first and move signal to the second frequency spectrum shift module；
The second frequency spectrum shift module is moved filtered described first signal and is moved to origin-location and obtains the thresholding
Extension signal；
The computing module receives first filtering signal and is calculated the signal that counts according to first filtering signal,
Count signal to the first frequency spectrum shift module and second Postponement module described in the computing module output.
2. the extended threshold system of digital FM receiver according to claim 1, it is characterised in that：
Second Postponement module receives the signal that counts of the computing module input, and the second delay letter is obtained after being postponed
Number, second Postponement module exports second postpones signal to the second frequency spectrum shift module.
3. the extended threshold system of digital FM receiver according to claim 1, it is characterised in that：
The computing module includes that derivative module, pulse cancellation module, the 3rd filtration module and cosine and sine signal occur module；
The derivative module receives first filtering signal and by first filtering signal process and obtains differential letter
Number, the derivative module exports the differential signal to the pulse cancellation module；
The disturbing pulse that the pulse cancellation module eliminates the differential signal obtains pulse elimination signal, and the pulse eliminates mould
Block exports the pulse and eliminates signal to the 3rd filtration module；
The noise that 3rd filtration module filters the pulse elimination signal obtains the 3rd filtering signal, the 3rd filtering mould
Block exports the 3rd filtering signal to the cosine and sine signal and module occurs；
The module that the cosine and sine signal occurs counts signal, the sine and cosine according to the 3rd filtering signal is calculated
Count signal to the first frequency spectrum shift module and the second Postponement module described in signal generating module output.
4. the extended threshold system of digital FM receiver according to claim 3, it is characterised in that：
The pulse cancellation module includes contrast module, multi-path choice module and the 3rd Postponement module,
Whether the contrast module is used to contrast default maximum more than or equal to the differential signal being input into；
The multi-path choice module is used to eliminate signal according to the pulse of the result of contrast module selection output；
3rd Postponement module is used to store the pulse elimination signal.
5. the extended threshold system of the digital FM receiver according to Claims 2 or 3, it is characterised in that：
The signal that counts counts signal including sine and cosine counts signal.
6. the extended threshold method of digital FM receiver, the method includes：
AFE(analog front end) step, receive FM signals and by the FM signal frequency conversions be intermediate-freuqncy signal；
Analog-to-digital conversion step, carries out the intermediate-freuqncy signal analog-to-digital conversion and obtains data signal；
Frequency mixing stages, are mixed to the data signal direct current and obtain mixed frequency signal；
First filter step, the noise and mirror image for filtering the mixed frequency signal obtains the first filtering signal；
Extended threshold step, the thresholding for extending first filtering signal is worth to extended threshold signal；
Demodulation step, demodulates the extended threshold signal and obtains demodulated signal；
It is characterized in that：
The extended threshold step includes that first postpones step, the first frequency spectrum shift step, the second filter step, the second frequency successively
Spectrum moves step and calculation procedure；
The first delay step is to carry out postponing the step of obtaining the first postpones signal by first filtering signal；
The first frequency spectrum shift step be by first postpones signal carry out frequency spectrum shift obtain first move signal
Step；
Second filter step is the step of moving signal by described first to be filtered；
The second frequency spectrum shift step be by filtered described first move signal move to origin-location obtain thresholding expand
The step of exhibition signal；
The calculation procedure for reception first filtering signal and is calculated the letter that counts according to first filtering signal
Number the step of.
7. the extended threshold method of digital FM receiver according to claim 6, it is characterised in that：
The extended threshold step includes that second postpones step, and the second delay step is before the second frequency spectrum shift step
Perform, it is described second delay step include receive described in count signal the step of.
8. the extended threshold method of digital FM receiver according to claim 6, it is characterised in that：
The calculation procedure includes that differentiation step, pulse removal process, the 3rd filter step and cosine and sine signal occur successively
Step；
The differentiation step includes receiving first filtering signal and by first filtering signal process obtaining micro-
The step of sub-signal；
The pulse removal process includes the step of disturbing pulse for eliminating the differential signal obtains pulse elimination signal；
3rd filter step includes the step of noise for filtering the pulse elimination signal obtains three filtering signals；
The cosine and sine signal generation step include counted according to the 3rd filtering signal is calculated signal the step of.
9. the extended threshold method of digital FM receiver according to claim 8, it is characterised in that：
The pulse removal process includes contrast step, multi-path choice step and the 3rd delay step successively,
The contrast step is the step of whether default maximum of contrast is more than or equal to the differential signal of input；
The multi-path choice step is the step of eliminating signal according to the comparing result selection output pulse of the contrast step；
The step of 3rd delay step eliminates signal to store the pulse.
10. the extended threshold method of the digital FM receiver according to claim 7 or 8, it is characterised in that：
The signal that counts counts signal including sine and cosine counts signal.
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| US6512555B1 (en) * | 1994-05-04 | 2003-01-28 | Samsung Electronics Co., Ltd. | Radio receiver for vestigal-sideband amplitude-modulation digital television signals |
| CN1134894C (en) * | 1998-03-11 | 2004-01-14 | 汤姆森特许公司 | Digital signal modulation system |
| CN102325110A (en) * | 2011-09-20 | 2012-01-18 | 中国空间技术研究院 | Large-modulation index satellite-borne digital frequency modulating receiver |
| CN205490507U (en) * | 2016-01-22 | 2016-08-17 | 建荣集成电路科技(珠海)有限公司 | Digital FM receiver's threshold extend system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP3450078B2 (en) * | 1995-01-30 | 2003-09-22 | セイコーエプソン株式会社 | Power assist device for electric vehicles |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6512555B1 (en) * | 1994-05-04 | 2003-01-28 | Samsung Electronics Co., Ltd. | Radio receiver for vestigal-sideband amplitude-modulation digital television signals |
| CN1134894C (en) * | 1998-03-11 | 2004-01-14 | 汤姆森特许公司 | Digital signal modulation system |
| CN102325110A (en) * | 2011-09-20 | 2012-01-18 | 中国空间技术研究院 | Large-modulation index satellite-borne digital frequency modulating receiver |
| CN205490507U (en) * | 2016-01-22 | 2016-08-17 | 建荣集成电路科技(珠海)有限公司 | Digital FM receiver's threshold extend system |
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