CN105791179A - Sampling frequency offset compensation device and method - Google Patents
Sampling frequency offset compensation device and method Download PDFInfo
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Abstract
The embodiment of the invention discloses a sampling frequency offset compensation device and method. The sampling frequency offset compensation device comprises a phase-locked loop which is used for generating frequency offset estimation reference signals according to pilot signals obtained from time domain signals; a sampling frequency offset estimation module which is used for estimating the sampling frequency offset signals of the time domain signals according to the frequency offset estimation reference signals; and a sampling frequency offset compensation module which is used for carrying out sampling frequency offset compensation to the time domain signals according to the sampling frequency offset estimated by the sampling frequency offset estimation module. According to the sampling frequency offset compensation device and method provided by the embodiment of the invention, the sampling frequency offset of stereo frequency modulation broadcast signals can be compensated accurately.
Description
Technical field
The present invention relates to communication technical field, particularly relate to a kind of sampling frequency offset compensation device and method.
Background technology
Although the utilization rate of digital display circuit radio receiver is improving, frequency modulation(PFM) (Frequencymodulatin, FM) receiver is still popular, and comes across more and more in mobile phone and other electronic handset.In numerous FM receivers, stereo FM broadcast receiver is most commonly seen a kind of FM receiver.
Monophonic FM is broadcasted, launches signal and only account for the frequency range of 30Hz to 15KHz, in this frequency range, launch the monophonic broadcasting signal not differentiating between left and right acoustic channels.Referring to Fig. 1, in the frequency range of 30Hz to 15KHz, the signal that stereo FM broadcast is launched is left channel signals and right-channel signals and signal 11.Therefore receiving stereo broadcasting signal according to mono receivers, actual reception is left and right acoustic channels and signal 11.Except carrying above-mentioned and signal, stereo broadcasting signal also includes the pilot signal 13 of 19KHz and the difference signal 12 of carrying left channel signals and right-channel signals.Described difference signal 12 is distributed in the frequency range of 23KHz to 53KHz, and is double-sideband suppressed-carrier (Doublesidebandsuppressedcarrier, DSBSC) signal.At receiver side, after receiving above-mentioned and signal 11 and difference signal 12, it is possible to complete recovers original left channel signals and right-channel signals.
The purpose of FM receiver is exactly the sound or the music that provide a user with high-fidelity.But, in practical application, because producing the temperature drift of the crystal oscillator of sample frequency, and effect of noise, usually there are some frequency departures in sample frequency.If sampling frequency deviation is too big, sound or the music of the output of FM receiver are possible to distortion, cause that Consumer's Experience worsens.But, traditional FM receiver can not be completely eliminated sampling frequency deviation, causes user to listen to the experience of stereo FM broadcast very poor.
Summary of the invention
The embodiment of the present invention provides a kind of sampling frequency offset compensation device and method, to realize the sampling frequency offset of stereo fm broadcast singal is carried out accurate compensation.
First aspect, embodiments provides a kind of sampling frequency offset compensation device, and described device includes:
Phaselocked loop, estimates reference signal for generating frequency deviation according to the pilot signal obtained from described time-domain signal；
According to described frequency deviation, sampling frequency offset estimation module, for estimating that reference signal estimates the sampling frequency offset signal of described time-domain signal；
Sampling frequency offset compensating module, carries out sampling frequency offset compensation for the sampling frequency offset estimated by described sampling frequency offset estimation module to described time-domain signal.
Second aspect, the embodiment of the present invention additionally provides a kind of sampling frequency offset compensation method, and described method includes:
Generate frequency deviation according to the pilot signal obtained from the time-domain signal received and estimate reference signal；
Estimate that reference signal estimates the sampling frequency offset signal of described time-domain signal according to described frequency deviation；
According to described sampling frequency offset signal, described time-domain signal is carried out sampling frequency offset compensation.
The sampling frequency offset compensation device of embodiment of the present invention offer and method, generate frequency deviation according to the pilot signal obtained from time-domain signal and estimate reference signal, estimate that reference signal estimates the sampling frequency offset signal of described time-domain signal by the described frequency deviation obtained, and the sampling frequency offset signal of described time-domain signal is compensated, it is achieved that the accurate compensation to the sampling frequency offset of stereo fm broadcast singal.
Accompanying drawing explanation
Fig. 1 is the spectrogram of the stereo FM broadcast modulation front signal that prior art provides；
Fig. 2 is the structural representation of the sampling frequency offset compensation device that first embodiment of the invention provides；
Fig. 3 is the structural representation of the sampling frequency offset compensation device that second embodiment of the invention provides；
Fig. 4 is the spectrogram of band filter in the sampling frequency offset compensation device that second embodiment of the invention provides；
Fig. 5 is the structural representation that in the sampling frequency offset compensation device that second embodiment of the invention provides, time domain turns frequency domain module；
Fig. 6 is the structural representation of phaselocked loop in the sampling frequency offset compensation device that third embodiment of the invention provides；
Fig. 7 is the structural representation of low pass filter in the sampling frequency offset compensation device that third embodiment of the invention provides；
Fig. 8 is the structural representation of the sampling frequency offset compensation device loop filter that third embodiment of the invention provides；
Fig. 9 is the structural representation of sampling frequency offset estimation module in the sampling frequency offset compensation device that fourth embodiment of the invention provides；
Figure 10 is the flow chart of sampling frequency offset compensation method in the sampling frequency offset compensation device that sixth embodiment of the invention provides；
Figure 11 is the schematic flow sheet of sampling frequency offset compensation method in the sampling frequency offset compensation device that seventh embodiment of the invention provides；
Figure 12 is the schematic flow sheet of the sampling frequency offset compensation device frequency domain signal conversion that seventh embodiment of the invention provides；
Figure 13 is that the sampling frequency offset compensation device frequency deviation that seventh embodiment of the invention provides estimates the schematic flow sheet that reference signal generates；
Figure 14 is the schematic flow sheet that the sampling frequency offset that seventh embodiment of the invention provides is estimated.
Detailed description of the invention
Below in conjunction with drawings and Examples, the present invention is described in further detail.It is understood that specific embodiment described herein is used only for explaining the present invention, but not limitation of the invention.It also should be noted that, for the ease of describing, accompanying drawing illustrate only part related to the present invention but not entire infrastructure.
The sampling frequency offset compensation device that the embodiment of the present invention provides is applied in stereo FM broadcast receiver, for the sampling frequency offset in stereo FM broadcasting receiver is corrected.
First embodiment
Referring to Fig. 2, described sampling frequency offset compensation device includes: phaselocked loop 21, sampling frequency offset estimation module 22 and sampling frequency offset compensating module 23.
The transmitting signal of stereo FM broadcast, namely the signal received by stereo FM broadcast receiver is an analogue signal.But, in order to utilize general digital platform that the transmitting signal of described stereo FM broadcast is processed, demodulating high-quality stereo audio signal from launching signal, the radio-frequency front-end at described stereo radio receiver adopts the sampled signal of high frequency that received signal is sampled.After received signal is sampled, at Disgrete Time Domain, received signal is processed.
But, due to factors such as interference, noises, often there is frequency deviation in the sampled signal carrying out to the received signal sampling, causes the result carrying out to the received signal sampling inaccurate, and then is difficult to high-quality from the signal received recover stereo audio signal.Namely the technical scheme that the present embodiment provides is used for solving above-mentioned technical problem.
Described phaselocked loop 21 estimates reference signal for generating frequency deviation according to the pilot signal obtained from time-domain signal.
Described pilot signal is the reception signal from described stereo FM broadcast, the pilot signal namely extracted in time-domain signal.Described pilot signal is a simple signal.Concrete, the frequency of described pilot signal is 19kHz.
Referring to Fig. 1, the primary signal before the modulation of described stereo FM broadcast comprises the pilot signal 13 that frequency is 19kHz.The purpose adding described pilot signal 13 in signal before described modulation is in that auxiliary realizes the demodulation to the difference signal 12 between left channel signals and right-channel signals.After obtaining the frequency-region signal that described time-domain signal is corresponding, band filter 22 is utilized to extract described pilot signal 13 from described frequency-region signal.
Concrete, described phaselocked loop 21 generates frequency deviation estimate reference signal by the pilot signal of input is carried out frequency and Phase Tracking.Identical with described pilot signal, described frequency deviation estimates that reference signal is also a simple signal.Generally, described frequency deviation estimates the frequency frequency higher than described pilot signal of reference signal.Further, described frequency deviation estimates that the phase place of reference signal keeps Tong Bu with the phase place of described pilot signal.
Further, described phaselocked loop 21 includes multiplier, low pass filter, the first loop filter and digital controlled oscillator.
According to described frequency deviation, described sampling frequency offset estimation module 22 is for estimating that reference signal estimates the sampling frequency offset signal of described time-domain signal.
Owing to keeping Tong Bu between phase place and the phase place of described pilot signal of described frequency deviation estimation reference signal, it is possible to the half period starting point of reference signal is to estimate the sampling frequency offset of described time-domain signal to utilize described frequency deviation to estimate.
Described sampling frequency offset compensating module 23 is for carrying out sampling frequency offset compensation according to described sampling frequency offset signal to described time-domain signal.
Concrete, described time-domain signal is redefined sampling time point by the described sampling frequency offset compensating module 23 sampling frequency offset estimated by described sampling frequency offset estimation module 22, thus described time-domain signal is carried out sampling frequency offset compensation.
The present embodiment estimates reference signal by utilizing phaselocked loop to generate frequency deviation according to the pilot signal extracted, described sampling frequency offset estimation module is utilized to estimate that reference signal estimates the sampling frequency offset signal of described time-domain signal according to described frequency deviation, and utilize described sampling frequency offset compensating module according to described sampling frequency offset signal, the sampling frequency offset of described time-domain signal to be compensated, it is achieved thereby that the accurate compensation of the sampling frequency offset to described time-domain signal.
Second embodiment
The present embodiment provides a kind of technical scheme of sampling frequency offset compensation device on the basis of above-described embodiment.Except phaselocked loop 33, sampling frequency offset estimation module 35 and beyond sampling frequency offset compensating module 36, this technical scheme includes: time domain turns frequency domain module 31, band filter 32 and sample synchronization module 34.
Referring to Fig. 3, described sampling frequency offset compensation device includes: time domain turns frequency domain module 31, band filter 32, phaselocked loop 33, sample synchronization module 34, sampling frequency offset estimation module 35 and sampling frequency offset compensating module 36.
Described time domain turns frequency domain module 31 for the time-domain signal of input is converted to frequency-region signal.
Described time domain turns the frequency domain module 31 time-domain signal for being received by stereo FM broadcast receiver, and namely the transmitting signal of stereo FM broadcast is converted to frequency-region signal.
General, the transmitting signal of the stereo FM broadcast after sampling has the form of formula (1):
Wherein, T is the sampling period, ω0For the angular frequency launching signal of stereo FM broadcast, θ0For the phase place launching signal of stereo FM broadcast, f (kT) is the audio signal modulated, the signal before namely stereo FM broadcast modulation, KfFor summation coefficient, φFM(kT) for the transmitting signal of described stereo FM broadcast.
Through the time domain launching signal of described stereo FM broadcast is changed to frequency domain, namely obtain frequency-region signal f (kT).
Preferably, it is possible to calculate (Coordinaterotationaldigitalcomputer, CORDIC) and phase difference by described time-domain signal being performed Coordinate Rotation Digital and obtain frequency-region signal.
Described band filter 32 for obtaining the pilot signal of setpoint frequency from described frequency-region signal.
Fig. 4 illustrates the spectral characteristic of described band filter.Referring to Fig. 4, being the passband of described band filter 32 near 19kHz frequency, other portions of the spectrum are the suppression band of described band filter 32.After described band filter 32, other frequency contents comprised in described frequency-region signal are filtered out, and only have the pilot signal that frequency is 19kHz and have been retained.Preferably, described band filter 32 has narrow-band characteristic.
It should be noted that described 19kHz, refer to the frequency of the corresponding analogue signal before sampling to the received signal.
Described phaselocked loop 33 generates frequency deviation for the pilot signal according to input and estimates reference signal.
Described sample synchronization module 34 estimates the half period starting point of reference signal for obtaining described frequency deviation.
Preferably, it is possible to the frequency deviation arrived by the sample and Real-time Collection calculating the frequency deviation estimation reference signal prestored estimates that the cross-correlation function between reference signal obtains described frequency deviation and estimates the half period starting point of reference signal.
Concrete, it is possible to store described frequency deviation in memory and estimate the half period sample of reference signal.After creating described frequency deviation and estimating reference signal, calculate described frequency deviation and estimate that the half period sample of reference signal and described frequency deviation estimate the cross-correlation function between reference signal, finally time point maximum for described cross-correlation function value is estimated as described frequency deviation the half period starting point of reference signal.
Described sampling frequency offset estimation module 35 estimates the sampling frequency offset signal of described time-domain signal for the described half period starting point obtained according to described sample synchronization module 34.
Described time-domain signal is carried out sampling frequency offset compensation for the sampling frequency offset estimated by described sampling frequency offset estimation module 35 by described sampling frequency offset compensating module 36.
The present embodiment turns frequency domain module by arranging time domain in sampling frequency offset compensation device, band filter, phaselocked loop, sample synchronization module, sampling frequency offset estimation module and sampling frequency offset compensating module, pilot signal is extracted from frequency-region signal, generate frequency deviation according to described pilot signal and estimate reference signal, reference signal estimates the sampling frequency offset of described time-domain signal to utilize described frequency deviation to estimate, finally described sampling frequency offset is compensated, thus having carried out compensating accurately to the sampling frequency offset of stereo FM broadcast singal, effectively reduce the reception bit error rate of stereo FM broadcast signal.
Exemplary, referring to Fig. 5, described time domain turns frequency domain module 31 and includes: phase place acquiring unit 51 and difference unit 52.
Described phase place acquiring unit 51 for obtaining the phase place of described time-domain signal according to arc tangent solving method or CORDIC method.
Described difference unit 52 is for carrying out difference to described phase place, to obtain described frequency-region signal.
3rd embodiment
The present embodiment provides a kind of technical scheme of phaselocked loop on the basis of above-described embodiment, and this technical scheme includes: multiplier 61, low pass filter the 63, first loop filter 64, accumulator 65 and digital controlled oscillator 66.
Referring to Fig. 6, described multiplier 61 is for being multiplied the pilot signal of acquisition with the reference signal of frequency.
The described phase place differing pi/2 with pilot signal with reference signal frequently with described pilot signal.If described pilot signal is the sinusoidal signal of 19kHz, then described reference signal is the cosine signal of 19kHz.The relation that described pilot signal is multiplied with described reference signal is provided by formula (2):
Wherein, ω is the angular frequency of described pilot signal, α is the phase place of described pilot signal, β is the phase place of described reference signal, T is described pilot signal and the sampling interval duration of described reference signal, the described pilot signal that sin (ω kT+ α) is the kT moment, the described reference signal that cos (ω kT+ β) is the kT moment, θ (kT) be multiplied with described reference signal for pilot signal described in the kT moment after signal.
By formula (2) it is known that θ (kT) comprises the signal that angular frequency is 2 ω and a time-independent direct current signal.The signal that angular frequency is 2 ω is called high-frequency signal, and described direct current signal is called low frequency signal.
Described low pass filter 63 is for filtering the high-frequency signal exported in signal of described multiplier.
The passband of described low pass filter 63 is in the low frequency part of frequency spectrum, and suppresses band to be in the HFS of frequency spectrum, therefore can be filtered by the high-frequency signal in the output signal of described multiplier.
It should be noted that the cut-off frequency of described low pass filter 63 is not above the frequency of described high-frequency signal, namely corresponding for angular frequency 2 ω in formula (2) frequency.
Described first loop filter 64 carries out loop filtering for the signal after described low pass filter 63 is filtered, and obtains low frequency signal.
In order to eliminate interference signal and the effect of noise that described phaselocked loop 21 exports in signal, the signal after described low pass filter 63 is filtered carries out loop filtering.
Described accumulator 65 is for adding up to described low frequency signal, when accumulation result value reaches threshold value, generates and triggers signal.
Concrete, described totalizing step is provided by formula (3):
In formula (3), step_value is the totalizing step of described accumulator 65, and fd is the frequency of described pilot signal, and fs is the sample frequency of described time-domain signal.
Described digital controlled oscillator 66 estimates reference signal for generating described frequency deviation according to described triggering signal.
When described digital controlled oscillator 66 receives the triggering signal of described accumulator 65 output, described digital controlled oscillator 66 exports described frequency deviation and estimates reference signal.Concrete, described digital controlled oscillator 66 is when receiving described triggering signal, and output has the frequency deviation of cosine form and estimates reference signal.
Preferably, described phaselocked loop 33 also includes a twice amplifier 62.Described twice amplifier 62, for the signal of input from described multiplier 61 is carried out twice amplification, exports the coefficient of 1/2 in signal with multiplier 61 described in compensation (3).
Described pilot signal is multiplied with the reference signal of frequency by the present embodiment by multiplier, utilize low pass filter that the signal after being multiplied is carried out low-pass filtering, utilize loop filter that the signal through low-pass filtering is carried out loop filtering, the low frequency signal generated after loop filtering is added up, and frequency deviation estimation reference signal is exported when accumulation result reaches totalizing step, complete the Phase Tracking to described pilot signal, generate the frequency deviation with accurate phase and estimate reference signal.
Exemplary, described low pass filter 63 farther includes: the first multiplier 71, first adder the 72, second multiplier 73, second adder 74 and the first delay unit 75.
Referring to Fig. 7, described first multiplier 71 is for being multiplied input signal and first controlling elements of described low pass filter 63, and the consequential signal input extremely described second adder 74 that will be multiplied.Wherein, the value of described first controlling elements is between 0 to 1.The value change of described first controlling elements may be used for controlling the bandwidth of described low pass filter 63.
Described first adder 72 is for being added described first controlling elements with logic 1 signal, and result output extremely described second multiplier 73 that will add up.
Described second multiplier 73 is for being multiplied the output valve of described first adder 72 with the output valve of the described low pass filter 63 after time delay, and by second adder 74 described in the readout that is multiplied
Described second adder 74 is for by described first multiplier 71 and the output results added of described second multiplier 73, obtaining the output valve of described low pass filter 63.
Described first delay unit 75 for carrying out delay process to the output valve of described low pass filter 63, and exports the output valve of the described low pass filter 63 after time delay to described second multiplier 73.
Exemplary, described first loop filter 64 farther includes: the 3rd multiplier the 81, the 3rd adder 82 and the second delay unit 83.
Referring to Fig. 8, described 3rd multiplier 81 is for being multiplied input signal and second controlling elements of described first loop filter 64, and exports the result being multiplied to the 3rd adder 82.Wherein, the value of described second controlling elements is between 0 to 1.Further, described second controlling elements are for controlling computational accuracy and the convergence rate of described loop filter 64.
Described 3rd adder 82 is for being added the output signal of the multiplying signal inputted from described 3rd multiplier 81 with described first loop filter 64 through time delay, to generate the output signal of described first loop filter 64.
Described second delay unit 83 is for carrying out delay process to the output signal of described first loop filter 64, and exports the output signal of described first loop filter 64 after time delay to described 3rd adder 82.
3rd embodiment
The present embodiment provides a kind of technical scheme of sampling frequency offset estimation module on the basis of above-described embodiment.
Referring to Fig. 9, this technical scheme includes: Timing Error Detection unit the 91, second loop filter 92 and timing error processing unit 93.
Described Timing Error Detection unit 91 turns the timing error of the time-domain signal that frequency domain module 31 receives specifically for detecting described time domain, obtains signal of timing error.
Concrete, described Timing Error Detection unit 91 determines the timing error of described time-domain signal according to formula (4):
E [k]={ y_f [kT+T/2]-y_f [(k-1) T+T/2] } × y_f [kT] (4)
Wherein, the frequency deviation that y_f [kT+T/2] is the kT+T/2 moment estimates reference signal, the frequency deviation that y_f [(k-1) T+T/2] is (k-1) T+T/2 moment estimates reference signal, the frequency deviation that y_f [kT] is the kT moment estimates reference signal, the described signal of timing error that E [kT] is the kT moment.
Described second loop filter 92 is for carrying out loop filtering to described signal of timing error.
Signal of timing error owing to being detected by described Timing Error Detection unit 91 would be likely to occur error, so needing described signal of timing error is smoothed.Concrete, the mode that described signal of timing error is smoothed is for carry out loop filtering to described signal of timing error.
Exemplary, described signal of timing error is carried out loop filtering according to formula (5) by described second loop filter 92.
E_loop [k]=E_loop [k-1]+G × E [k] (5)
Wherein, the signal of timing error that E [k] is the k moment, G is gain coefficient, described signal of timing error is carried out loop rate and filters the signal obtained by described second loop filter 92 that E_loop [k] is the k moment, and described signal of timing error is carried out the signal that loop filtering obtains by described second loop filter 92 that E_loop [k-1] is the k-1 moment.
Described timing error processing unit 93, for carrying out anti-phase and amplitude limit to carrying out the signal that loop filtering obtains, exports and estimates, according to described frequency deviation, the sampling frequency offset signal that reference signal is estimated.
Concrete, described timing error processing unit 93 can include the anti-phase process performed according to formula (6) and the amplitude limiting processing to the above-mentioned consequential signal asking difference process.
E_out=C-E_loop (6)
In formula (6), C is constant, and E_loop is that described signal of timing error is carried out the signal that loop filtering obtains by described second loop filter 92, E_out be described in ask difference process consequential signal.It is understood that the difference of asking shown in through type (6) calculates, owing to C is constant, the opposite in phase between the E_out signal and the E-loop signal that obtain, namely complete the anti-phase process carrying out the signal that loop filtering obtains.
According to described frequency deviation, the present embodiment is by estimating that reference signal calculates the timing error of described time-domain signal, the signal of timing error obtained is carried out loop filtering, and the signal after loop filtering is carried out further anti-phase and amplitude limit, obtain the accurate of the sampling frequency offset to described time-domain signal and estimate.
4th embodiment
The present embodiment provides a kind of technical scheme of sampling frequency offset compensating module on the basis of above-described embodiment.In this technical scheme, described sampling frequency offset compensating module utilizes the mode of filtering interpolation, it is achieved the compensation to the sampling frequency offset of described time-domain signal.
Preferably, described sampling frequency offset compensating module is an interpolation filter.The sampling frequency offset of described time-domain signal is compensated by described interpolation filter according to formula (7).
Y_out (m)=y (m)+p_f × [y (m+1)-y (m)] (7)
Wherein, the time-domain sample signal in the m moment that y_out (m) exports for described differential filtering device, the time-domain sample signal that y (m) inputs in m moment and m+1 moment with y (m+1) respectively described differential filtering device, and the fractional part that p_f is the sampling frequency offset signal that described sampling frequency offset estimation module obtains.
Further, described time-domain sample signal is the time of the sampling time point that described time-domain signal is sampled.
Described time-domain signal is interpolated filtering by the present embodiment sampling frequency offset signal estimated by described sampling frequency offset estimation module, thus having carried out compensating accurately to the sample frequency of described time-domain signal.
5th embodiment
The sampling frequency offset compensation method that the present embodiment provides has above-mentioned sampling frequency offset compensation device to realize.
Referring to Figure 10, described sampling frequency offset compensation method includes: operation 101 to 103.
Operation 101, generates frequency deviation according to the pilot signal obtained from described time-domain signal and estimates reference signal.
Described pilot signal is included in a simple signal in described time-domain signal, is mainly used in auxiliary and the difference signal between described left channel signals and described right-channel signals is demodulated.Preferably, utilize phaselocked loop that described pilot signal is carried out Phase Tracking, thus generating described frequency deviation to estimate reference signal.
According to described frequency deviation, operation 102, estimates that reference signal estimates the sampling frequency offset signal of described time-domain signal.
Preferably, it is possible to estimate that the half period starting point of reference signal estimates the sampling frequency offset signal of described time-domain signal according to the described frequency deviation obtained.
Operation 103, carries out sampling frequency offset compensation according to described sampling frequency offset signal to described time-domain signal.
After obtaining described sampling frequency offset signal, according to described sampling frequency offset signal, the sampling frequency offset of described time-domain signal is compensated.Preferably, by redefine described time-domain signal sampling time put described time-domain signal is carried out sampling frequency offset compensation.
The present embodiment estimates reference signal by generating frequency deviation according to the pilot signal obtained from described time-domain signal, estimate that reference signal estimates the sampling frequency offset signal of described time-domain signal according to described frequency deviation, and described time-domain signal is carried out sampling frequency offset compensation according to described sampling frequency offset signal, it is achieved thereby that the accurate compensation of the sampling frequency offset to the time-domain signal of stereo FM broadcast.
5th embodiment
The present embodiment, based on above-described embodiment, gives the another kind of technical scheme of sampling frequency offset compensation method.In the technical program, before generating described frequency deviation estimation reference signal, the time-domain signal of reception is converted to frequency-region signal；The pilot signal of setpoint frequency is obtained from described frequency-region signal；After generating described frequency deviation and estimating reference signal, before estimating described sampling frequency offset signal, obtain described frequency deviation and estimate the half period starting point of reference signal；Then estimate that reference signal estimates that the sampling frequency offset signal of described time-domain signal includes according to described frequency deviation: estimate the sampling frequency offset signal of described time-domain signal according to described half period starting point.
Referring to Figure 11, described sampling frequency offset compensation method includes: operation 111 is to operating 116.
Operation 111, is converted to frequency-region signal by the time-domain signal of reception.
What described stereo FM receiver received is time-domain signal.After receiving above-mentioned time-domain signal, described time-domain signal is converted to frequency-region signal.
Operation 112, obtains the pilot signal of setpoint frequency from described frequency-region signal.
Comprising a frequency in described frequency-region signal is the single frequency pilot of 19kHz.After obtaining described frequency-region signal, from described frequency-region signal, obtain described pilot signal.Preferably, from described frequency-region signal, described pilot signal is obtained by bandpass filtering.
Operation 113, generates frequency deviation according to the pilot signal obtained and estimates reference signal.
After obtaining described pilot signal, generate frequency deviation according to described pilot signal and estimate reference signal.Preferably, utilize phaselocked loop that described pilot signal is carried out Phase Tracking, thus generating described frequency deviation to estimate reference signal.
Operation 114, obtains described frequency deviation and estimates the half period starting point of reference signal.
Concrete, estimate the half period sample of reference signal and the cross-correlation function of described frequency deviation estimation reference signal by calculating the frequency deviation prestored, and the time point that described cross-correlation function takes maximum estimates the half period starting point of reference signal as described frequency deviation.
Operation 115, estimates the sampling frequency offset signal of described time-domain signal according to described half period starting point.
Operation 116, carries out sampling frequency offset compensation according to described sampling frequency offset to described time-domain signal.
Exemplary, referring to Figure 12, the time-domain signal of reception is converted to frequency-region signal and includes: operation 121 and operation 122.
Operation 121, calculates CORDIC method according to arc tangent solving method or Coordinate Rotation Digital and obtains the phase place of described time-domain signal.
Operation 122, carries out difference to described phase place, to obtain described frequency-region signal.
Exemplary, referring to Figure 13, generate frequency deviation according to the pilot signal obtained and estimate that reference signal includes:
Operation 131, is multiplied the pilot signal of acquisition with the reference signal of frequency.
Operation 132, filters the high-frequency signal in the output signal being multiplied.
Operation 133, carries out loop filtering to the signal after filtering, obtains low frequency signal.
Operation 134, adds up to described low frequency signal, when accumulation result value reaches threshold value, generates and triggers signal.
Operation 135, generates described frequency deviation according to described triggering signal and estimates reference signal.
Exemplary, referring to Figure 14, estimate that according to described half period starting point the sampling frequency offset of described time-domain signal includes:
Operation 141, the timing error of the time-domain signal that detection receives, obtain signal of timing error.
Operation 142, carries out loop filtering to described signal of timing error.
Operation 143, carries out anti-phase and amplitude limit to carrying out the signal that loop filtering obtains, exports and estimate, according to described frequency deviation, the sampling frequency offset signal that reference signal is estimated.
The present embodiment is by being converted to frequency-region signal by the time-domain signal of reception, the pilot signal of setpoint frequency is obtained from described frequency-region signal, generate frequency deviation according to the pilot signal obtained and estimate reference signal, obtain described frequency deviation and estimate the half period starting point of reference signal, the sampling frequency offset of described time-domain signal is estimated according to described half period starting point, according to described sampling frequency offset, described time-domain signal is carried out sampling frequency offset compensation, it is achieved that the accurate compensation to the sampling frequency offset of stereo fm broadcast singal.
Note, above are only presently preferred embodiments of the present invention and institute's application technology principle.It will be appreciated by those skilled in the art that and the invention is not restricted to specific embodiment described here, various obvious change can be carried out for a person skilled in the art, readjust and substitute without departing from protection scope of the present invention.Therefore, although the present invention being described in further detail by above example, but the present invention is not limited only to above example, when without departing from present inventive concept, other Equivalent embodiments more can also be included, and the scope of the present invention is determined by appended right.
Claims (19)
1. a sampling frequency offset compensation device, it is characterised in that including:
Phaselocked loop, estimates reference signal for generating frequency deviation according to the pilot signal obtained from described time-domain signal；
According to described frequency deviation, sampling frequency offset estimation module, for estimating that reference signal estimates the sampling frequency offset signal of described time-domain signal；
Sampling frequency offset compensating module, carries out sampling frequency offset compensation for the sampling frequency offset estimated by described sampling frequency offset estimation module to described time-domain signal.
2. sampling frequency offset compensation device according to claim 1, it is characterised in that also include:
Time domain turns frequency domain module, for the time-domain signal of reception is converted to frequency-region signal；
Band filter, for obtaining the pilot signal of setpoint frequency from described frequency-region signal；
Then described phaselocked loop generates frequency deviation estimation reference signal for the pilot signal obtained according to described band filter.
3. sampling frequency offset compensation device according to claim 2, it is characterised in that also include:
Sample synchronization module, estimates the half period starting point of reference signal for obtaining described frequency deviation；
Then described sampling frequency offset estimation module estimates the sampling frequency offset signal of described time-domain signal for the described half period starting point obtained according to described sample synchronization module.
4. sampling frequency offset compensation device according to claim 3, it is characterised in that described time domain turns frequency domain module and includes:
Phase place acquiring unit, obtains the phase place of described time-domain signal for calculating CORDIC method according to arc tangent solving method or Coordinate Rotation Digital；
Difference unit, for carrying out difference to described phase place, to obtain described frequency-region signal.
5. sampling frequency offset compensation device according to claim 3, it is characterised in that described phaselocked loop includes:
Multiplier, for being multiplied the pilot signal of acquisition with the reference signal of frequency；
Low pass filter, for filtering the high-frequency signal exported in signal of described multiplier；
First loop filter, carries out loop filtering for the signal after described low pass filter is filtered, obtains low frequency signal；
Accumulator, for described low frequency signal is added up, when accumulation result value reaches threshold value, generates and triggers signal；
Digital controlled oscillator, estimates reference signal for generating described frequency deviation according to described triggering signal.
6. sampling frequency offset compensation device according to claim 5, it is characterised in that the totalizing step of described accumulator is:
Wherein, step_value is the totalizing step of described accumulator, fdFor the frequency of described pilot signal, fsSample frequency for described time-domain signal.
7. sampling frequency offset compensation device according to claim 3, it is characterized in that, described sample synchronization module estimates reference signal for the frequency deviation that will receive, estimate that reference signal sample carries out cross-correlation with the frequency deviation prestored, and by time point maximum for cross correlation value, estimate the half period starting point of reference signal as described frequency deviation.
8. sampling frequency offset compensation device according to claim 3, it is characterised in that described sampling frequency offset estimation module includes:
Timing Error Detection unit, turns the timing error of the time-domain signal that frequency domain module receives, obtains signal of timing error for detecting described time domain；
Second loop filter, for carrying out loop filtering to described signal of timing error；
According to result and described frequency deviation, timing error processing unit, for carrying out anti-phase and amplitude limiting processing to carrying out the signal that loop filtering obtains, estimates that reference signal estimates described sampling frequency offset signal.
9. sampling frequency offset compensation device according to claim 8, it is characterised in that the described signal of timing error that described Timing Error Detection unit obtains is:
E [k]={ y_f [kT+T/2]-y_f [(k-1) T+T/2] } × y_f [kT]
Wherein, the frequency deviation that y_f [kT+T/2] is the kT+T/2 moment estimates reference signal, the frequency deviation that y_f [(k-1) T+T/2] is (k-1) T+T/2 moment estimates reference signal, the frequency deviation that y_f [kT] is the kT moment estimates reference signal, the described signal of timing error that E [kT] is the kT moment.
10. sampling frequency offset compensation device according to claim 8, it is characterised in that described signal of timing error is carried out the signal that loop filtering obtains and is by described second loop filter:
E_loop [k]=E_loop [k-1]+G × E [k]
Wherein, the signal of timing error that E [k] is the k moment, G is gain coefficient, described signal of timing error is carried out loop rate and filters the signal obtained by described second loop filter that E_loop [k] is the k moment, and described signal of timing error is carried out the signal that loop filtering obtains by described second loop filter that E_loop [k-1] is the k-1 moment.
11. sampling frequency offset compensation device according to claim 8, it is characterised in that the described sampling frequency offset signal of described timing error processing unit output is:
E_out=C-E_loop
Wherein, C is constant, and E_loop is that described signal of timing error is carried out the signal that loop filtering obtains by described second loop filter, and E_out is described sampling frequency offset signal.
12. sampling frequency offset compensation device according to claim 3, it is characterised in that described sampling frequency offset compensating module is interpolation filter.
13. sampling frequency offset compensation device according to claim 12, it is characterised in that described interpolation filter output signal is:
Y_out [m]=y [m]+p_f × { y [m+1]-y [m] }
Wherein, p_f is the fractional part of described sampling frequency offset signal, the time-domain signal that y [m] is the m moment, the time-domain signal that y [m+1] is the m+1 moment, and y_out [m] is the output signal of described differential filtering device.
14. a sampling frequency offset compensation method, it is characterised in that including:
Generate frequency deviation according to the pilot signal obtained from the time-domain signal received and estimate reference signal；
Estimate that reference signal estimates the sampling frequency offset signal of described time-domain signal according to described frequency deviation；
According to described sampling frequency offset signal, described time-domain signal is carried out sampling frequency offset compensation.
15. sampling frequency offset compensation method according to claim 14, it is characterised in that also include:
Before generating described frequency deviation estimation reference signal, the time-domain signal of reception is converted to frequency-region signal；
The pilot signal of setpoint frequency is obtained from described frequency-region signal.
16. sampling frequency offset compensation method according to claim 15, it is characterised in that also include:
After generating described frequency deviation and estimating reference signal, before estimating described sampling frequency offset signal, obtain described frequency deviation and estimate the half period starting point of reference signal；
Then estimate that reference signal estimates that the sampling frequency offset signal of described time-domain signal includes according to described frequency deviation:
The sampling frequency offset signal of described time-domain signal is estimated according to described half period starting point.
17. sampling frequency offset compensation method according to claim 16, it is characterised in that the time-domain signal of reception is converted to frequency-region signal and includes:
Calculate CORDIC method according to arc tangent solving method or Coordinate Rotation Digital and obtain the phase place of described time-domain signal；
Described phase place is carried out difference, to obtain described frequency-region signal.
18. sampling frequency offset compensation method according to claim 16, it is characterised in that generate frequency deviation according to the pilot signal obtained from the time-domain signal received and estimate that reference signal includes:
The pilot signal of acquisition is multiplied with the reference signal of frequency；
Filter the high-frequency signal in the output signal being multiplied；
Signal after filtering is carried out loop filtering, obtains low frequency signal；
Described low frequency signal is added up, when accumulation result value reaches threshold value, generates and trigger signal；
Generate described frequency deviation according to described triggering signal and estimate reference signal.
19. sampling frequency offset compensation method according to claim 16, it is characterised in that estimate that according to described half period starting point the sampling frequency offset of described time-domain signal includes:
The timing error of the time-domain signal that detection receives, obtains signal of timing error；
Described signal of timing error is carried out loop filtering；
Process carrying out the signal that loop filtering obtains, export and estimate, according to described frequency deviation, the sampling frequency offset signal that reference signal is estimated.
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