CN1812389A - Frequency recovery apparatus and method for digital multimedia broadcasting receiver - Google Patents
Frequency recovery apparatus and method for digital multimedia broadcasting receiver Download PDFInfo
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- CN1812389A CN1812389A CNA2005100330464A CN200510033046A CN1812389A CN 1812389 A CN1812389 A CN 1812389A CN A2005100330464 A CNA2005100330464 A CN A2005100330464A CN 200510033046 A CN200510033046 A CN 200510033046A CN 1812389 A CN1812389 A CN 1812389A
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Abstract
This invention is a kind of frequency recovery method for digital broadcasting receiver. It concludes: I/Q distributor, which divided the gain augmenting transmitted signal into real number part and imaginary number part. It also converts the signal to low-frequency frequency band and outputs the converted signal; fast Fourier transformation part, which converts the signal into frequency area signal; level detector, which makes the said signal to carry out level detecting and converts it into QPSK state signal; first inference machine, which infers error by the searching mode; second inference machine, which infers error by tracking mode; first, second cycle filters, which input the said inferred error numerical value and cumulate the augmenting error according to self-determined frequency band amplitude; numeric control oscillator, which generates sine wave and cosine wave corresponded to the said augmenting numerical value; multiplier, which multiplies the said generated sine wave and cosine wave by low-frequency frequency band signal outputted from the said I/Q distributor. It also outputs the error augmenting signal.
Description
(1) technical field
The invention relates to the technology of the frequency recovery of digital multimedia broadcasting system, more particularly carry out the frequency recovery apparatus and the method for a kind of digital multimedia broadcast receiver of revisal about the corresponding frequency error of decimal (1kHz is following) to the carrier spacing in the frequency field.
(2) background technology
DMB (Digital Multimedia Broadcasting, hereinafter to be referred as DMB) use OFDM (the Orthogonal Frequency Division Multplexing: right angle frequency division multipath conversion) of system, it utilizes a plurality of carrier waves, transmits simultaneously.
In order to make above-mentioned a plurality of carrier wave, need a plurality of oscillators, with IFFT (Inverse Fast Fourier Transform: contrary fast Fourier transform) replace using oscillator, in numeric area, construct above-mentioned a plurality of carrier wave.
Like this, utilize a plurality of carrier waves to transmit, for its separation, should have the right angle at intercarrier at receiving terminal.If above-mentioned so-called right angle is exactly with mutual different carrier multiplication, integration occurs 0, only has the characteristic of numerical value at identical intercarrier.
Therefore, if receiving terminal with the signal that receives and separately carrier multiplication, integration owing to the signal of each carrier wave correspondence only occurs, can be with Signal Separation.At this moment, do not use oscillator, and be to use FFT (fast Fourier transform), take on the effect of above-mentioned product and integration.
At this moment, if having error in the carrier wave in received signal, the right angle of the intercarrier of reception is broken, and disturbs by producing in the signal of fast Fourier transformation algorithm appearance, and signal noise ratio (SNR) reduces.
There is not the constant phase place by the grade wave detector of receiver in the phase error of above-mentioned received signal.Therefore, what should consider is frequency error, infers that also this frequency error of revisal is a sixty-four dollar question.
(3) summary of the invention
To the objective of the invention is in order addressing the above problem, to provide a kind of decimal frequency error below the 1kHz in the frequency error in frequency field carrier spacing is inferred the also frequency recovery apparatus and the method for a kind of digital multimedia broadcast receiver of revisal.
To achieve these goals, the frequency recovery apparatus of digital multimedia broadcast receiver of the present invention and method, signal to the specific channel that transmits by OFDM right angle frequency division multipath conversion modulation system carries out detection, its frequency recovery apparatus of DMB receiver that is recovered to the signal of revisal frequency error and phase error is made of following components, and as feature: the signal of the above-mentioned transmission of gain revisal, the signal of input digit conversion, it is separated into real part and imaginary part, and to the I/Q distributor of low-frequency band conversion and output; By in the signal of above-mentioned low-frequency band, carrying out the fast Fourier transform computing, convert FFT (fast Fourier transform) portion of frequency field signal to; With above-mentioned signal is that signal unit carries out the grade detection, converts the grade wave detector of the signal of QPSK state to; The time zone signal of input before above-mentioned frequency field conversion inferred by the 1st error of search (acquisition) pattern inference error; Import the signal of above-mentioned QPSK (quadriphase PSK) state, by following the tracks of the 2nd error estimator of (tracking) pattern inference error; Import the error numerical value of above-mentioned deduction, according to the frequency band width of cloth that determines separately, the 1st recursive filter and the 2nd recursive filter of accumulation revisal error; Generate the sine wave of numerical value correspondence of above-mentioned revisal and the Numerical Control oscillator of cosine wave; The sine of above-mentioned generation is involved the signal multiplication of the low-frequency band of cosine wave and the output of above-mentioned I/Q distributor, the multiplier of the signal of output error revisal.
The feature of the frequency recovery apparatus of DMB receiver is: above-mentioned the 2nd error estimator is made of following components, and as feature: import the output of above-mentioned grade wave detector, the QPSK resolver of decision QPSK (quadriphase PSK) signal; Import the signal of the signal deciding front and back of above-mentioned QPSK resolver, with above-mentioned two signal multiplications, with the multiplier of the I-Phase direction of principal axis rotation of the angle astrology dot image of the numerical value of above-mentioned decision: only with the imaginary part Q in the output of above-mentioned multiplier at the effective accumulator of the interval addition of carrier wave; Try to achieve the averager of the mean value of above-mentioned accumulation numerical value.
The frequency recovery apparatus of DMB receiver also comprises following structure, and as feature: import the output signal of above-mentioned I/Q distributor, delta frame and signal Synchronization signal are to the frame and the signal Synchronization portion of above-mentioned FFT (fast Fourier transform) portion output.
The frequency recovery apparatus of DMB receiver also comprises following structure, and as feature: select and export one MUX (Port Multiplier) in the output valve of above-mentioned the 1st, second recursive filter by the selection signal of outside.
Signal to the specific channel that transmits by OFDM right angle frequency division multipath conversion modulation system carries out detection, its frequency recovery method of DMB receiver of the present invention that is recovered to the signal of revisal frequency error and phase error is made of following step, and as feature: the gain of the signal of the above-mentioned transmission of revisal, carry out the step of digital translation; The Signal Separation of above-mentioned digital translation is become real part and imaginary part, and with its step to the low-frequency band conversion; By in the signal of above-mentioned low-frequency band, carrying out the fast Fourier transform computing, convert thereof into the step of frequency field signal; With above-mentioned signal is that signal unit carries out the grade detection, converts the step of the signal of QPSK (quadriphase PSK) state to; The time zone signal of input before above-mentioned frequency field conversion is by the step of search (acquisition) pattern inference error; Import the signal of above-mentioned QPSK state, by following the tracks of the step of (tracking) pattern inference error; Import the error numerical value of above-mentioned deduction, according to the frequency band width of cloth that determines separately, the step of accumulation revisal error; Generate the sine wave of numerical value correspondence of above-mentioned revisal and the step of cosine wave; With the signal multiplication of the low-frequency band of the sine of above-mentioned generation and cosine wave and the output of above-mentioned I/Q distributor, the step of the signal of output error revisal.
The feature of the frequency recovery method of DMB receiver is: the error of above-mentioned tracing mode infers that step also comprises following several steps: import the signal of above-mentioned QPSK (quadriphase PSK) state, the step of decision QPSK signal; Import the signal of above-mentioned QPSK signal deciding front and back, with above-mentioned two signal multiplications, to the step of the I-Phase of astrology dot image axle rotation; Only multiply each other above-mentioned, the imaginary part in the output signal is to the step of the interval addition accumulation of effective carrier wave; Try to achieve the step of the mean value of above-mentioned accumulation numerical value.
Effect of the present invention:
The frequency recovery apparatus and the method for DMB of the present invention (DMB) receiver reach following effect.
The first, infer frequency error by search pattern and tracing mode, and carry out revisal, reach rapidly, restore the effect of frequency exactly.
The second, utilize accumulator at frequency field, the calculated rate error by trying to achieve mean value, reaches the very little effect of dispersion simply.
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
Fig. 1 is the formation schematic diagram of the frequency recovery system of DMB receiver of the present invention.
Fig. 2 is the schematic diagram of an embodiment of the frequency error estimator of frequency recovery of the present invention system.
The symbol description of major part in the accompanying drawing:
1: tuner 2:AGC (automatic gain control)
3:A/D transducer 4:I/Q distributor
5: frame and signal Synchronization portion 6: multiplier
7:FFT (fast Fourier transform) portion 8: grade wave detector
10: the 2 estimators of 9: the 1 estimators
12: the 2 recursive filters of 11: the 1 recursive filters
13: Port Multiplier (MUX)
14: the Numerical Control oscillator
(5) embodiment
Below with reference to accompanying drawings the frequency recovery apparatus of DMB of the present invention (DMB) receiver and the embodiment of method are elaborated.
Fig. 1 is the formation schematic diagram of the frequency recovery system of DMB receiver of the present invention.
As shown in Figure 1, the frequency recovery system of DMB receiver is made of following components: will be converted to the tuner 1 of transmission band (Pass-band) signal of intermediate frequency (Intermediate Frequency) by the received signal of antenna input; For certain amplitude of the signal of A/D converter after keeping 3 input, with above-mentioned tuning signal and the automatic gain control of multiplying each other (AGC:Automatic Gain Control: automatic gain control) portion 2 according to the gain of standard signal magnitude determinations; The signal of above-mentioned certain amplitude is taken a sample (Sampling), and (Analog-Digital: analog/digital) transducer 3 to be converted to the A/D of digital signal; The composite signal (Complex Signal) of the digital signal of above-mentioned conversion is separated into real part (Real Part) and imaginary part, to the I/Q distributor 4 of low-frequency band conversion; Infer the frame of low frequency signal of above-mentioned conversion and the frame and the signal Synchronization portion 5 of signal Synchronization; Utilize the low frequency signal and the synchronizing signal of above-mentioned conversion,, convert the FFT portion 7 of frequency field signal to by carrying out FFT (fast Fourier transform); With above-mentioned signal is that signal unit carries out the grade detection, is converted to the transmission signal--the grade wave detector 8 of QPSK status signal; The time zone signal of input before above-mentioned frequency field conversion is by the 1st error estimator 9 of search (acquisition) pattern inference error; Import the signal of above-mentioned QPSK state, by following the tracks of (tracking) pattern, the 2nd error estimator 10 of inference error; Import the error amount of above-mentioned deduction, according to the frequency band width of cloth that determines separately, the 1st recursive filter 11 and the 2nd recursive filter 12 of accumulation revisal error; Import above-mentioned compensating value respectively,, select one Port Multiplier (MUX) 13 in the numerical value of above-mentioned revisal by the selection signal of outside; Generate the sine wave of numerical value correspondence of above-mentioned revisal and the Numerical Control oscillator 14 of cosine wave; With the signal multiplication of the low-frequency band of the sine of above-mentioned generation and cosine wave and 4 outputs of above-mentioned I/Q distributor, the multiplier 6 of the signal of output error revisal.
The course of action of the DMB receiver frequency recovery of the present invention system that constitutes according to said structure is as follows.
At first, the signal that the 200MHz frequency band receives is converted to intermediate frequency signal by tuner 1, adjusts by the gain of 2 pairs of signals of automatic gain control part (AGC).The signal of above-mentioned gain adjustment is taken a sample by A/Dz transducer 3, is converted to digital signal, by I/Q distributor 4, is separated into real part and imaginary part, exports to low-frequency band.
Utilize the signal of above-mentioned low-frequency band, in the 1st estimator 9, infer the frequency error of search (acquisition) pattern.
Above-mentioned search pattern is one of pattern of having of frequency recovery system.Frequency recovery of the present invention system is made of two kinds of patterns, and they are: collect the search pattern of mistake fast and accurately collect tracking (tracking) pattern of little error.
Frequency recovery system by the action of above-mentioned search pattern uses characteristic--the method that guard interval is identical with the definite part of signal at time zone OFDM (right angle frequency division multipath conversion) signal.
Promptly; because guard interval (Guard Interval) is identical with the definite part of signal; if there is frequency error; the definite part of guard interval and signal can be because frequency error; cause phase place that certain variation takes place; if utilize relevant (correlation) relation value to show it, be merely able to by signal amplitude and frequency error performance.
Bright for instance, if the value arbitrarily of the guard interval of OFDM (right angle frequency division multipath conversion) signal is a*exp (j*wn), the signal in the Dui Ying signal is a with it.Above-mentioned two values all reduce the M size, if there is frequency error dW, are exactly a*exp (j*dWn) and a*exp (j*dW (n+M)).
If it is exactly that (j*dW (n+M))=a2*exp (j*dWM) for a*exp (j*dWn) * a*exp that above-mentioned two values are multiplied each other.The output of above-mentioned product is exactly the amplitude and the frequency error of signal.
If in above-mentioned output valve, get imaginary number, be sin (dWM), littler if dWM is bigger than 0 than π, be positive number, if littler than 0, bigger than π, be negative, utilize the output of product, can infer frequency error.
The numerical value of above-mentioned deduction is imported to the 1st recursive filter 11, and the revisal error amount in this case, can obtain ± 500Hz (situation of transfer mode 1).At this moment, use big that of the frequency band width of cloth of above-mentioned the 1st recursive filter 11, can carry out revisal to it fast.
On the other hand, the signal of above-mentioned low-frequency band utilizes the synchronizing signal of frame and signal Synchronization portion 5, at FFT (Fast Fourier Transform: fast Fourier transform) be converted to the signal of frequency field in the portion 7.The output signal of above-mentioned FFT portion 7 is as the DQPSK signal that loads in each carrier wave, if be signal unit with this signal, carries out the grade detection by grade wave detector 8, can obtain to send signal--the signal of-QPSK state.
At this moment, if there is frequency error in received signal, above-mentioned QPSK signal is distorted, because frequency error, astrology point (constellation point) rotates.
In order to find this error, the 2nd estimator 10 is inferred frequency error by following the tracks of (tracking) pattern.That is, above-mentioned the 2nd estimator 10 adopts the angle of rotating by above-mentioned astrology point to infer the method for frequency error.
Below, we are elaborated to this content with reference to Fig. 2.Fig. 2 is the schematic diagram of an embodiment of frequency error the 2nd estimator of frequency recovery of the present invention system.
As shown in Figure 2, frequency error the 2nd estimator of frequency recovery system is made of following components: the output of input rank wave detector 8, the QPSK resolver 101 of decision QPSK signal; Multiplier 102 with the I-Phase direction of principal axis rotation of the angle astrology dot image of the numerical value of above-mentioned decision; Only with the accumulator 103 of imaginary part (Q) in the numerical value of above-mentioned rotation to the interval accumulation of effective carrier wave; Try to achieve the averager 104 of mean value of the numerical value of above-mentioned accumulation.
The action relationships of frequency error the 2nd estimator 10 of Gou Chenging is as follows like this.
Above-mentioned the 2nd estimator 10) input signal is the output of grade wave detector 8---QPSK signal, if owing to have frequency error in above-mentioned signal, its astrology point rotates, by the above-mentioned signal of QPSK resolver 101 decisions.That is, for instance, if the coordinate of astrology point is (0.707,0.707), the value of decision is (1,1).
Utilize the angle of above-mentioned signals, above-mentioned signal is rotated round about.In the above example, because the value of decision is (1,1), so be 135 degree, if with its rotation-135 degree, the coordinate on the astrology point diagram is to (1,0).
If the coordinate that utilizes said method rotation to utilize frequency error to rotate, I-Phase (phase place) axle ± have the output signal of above-mentioned grade wave detector 8 in 45 degree.
In this case, if there is no frequency error, coordinate is positioned at the I-Phase axle, if coordinate be positioned at the I-Phase axle below, frequency error is just (+), if be positioned at the I-Phase axle above, frequency error is negative (-).
Like this, the 2nd estimator 10 internal multiplier 102 have the effect of rotation.That is, the signal before and after 101 decisions of input QPSK resolver, with above-mentioned two signal multiplications, the output valve of rotation grade wave detector 8.
Bright for instance, if the angle of above-mentioned QPSK resolver 101 decisions is 45 degree, signal before above-mentioned QPSK resolver 101 decisions--the angle that-frequency error stretches is 50 degree, because exp (j50) * exp (j-45)=exp (j50-45)=exp (j5) can know that it rotates to the IPhase direction of principal axis.
In the signal of above-mentioned rotation, have only imaginary part in effective carrier wave interval, its mean value is tried to achieve in accumulation in averager 104 in accumulator 103.Above-mentioned mean value is the output valve of the 2nd estimator 10, is the error amount of inferring.
The frequency band width of cloth according to 12 decisions of the 2nd recursive filter is accumulated revisal to the error amount of above-mentioned deduction.
DMB has 4 kinds of transfer modes.In Korea S, the number of the effective carrier wave of the transfer mode 1 that adopts as standard is 1536.Therefore, if use the method for above-mentioned the 2nd estimator 10, can obtain ± frequency error of 100Hz,, disperse very little owing to try to achieve 1536 mean values.
Selection signal according to the outside, Port Multiplier (MUX) 13 is selected in the output valve of above-mentioned the 1st, 2 recursive filters 11,12, the numerical value of above-mentioned selection generates the Numerical Control signal of sine and cosine waveform by Numerical Control oscillator (NCO:Numerical Control Oscillator) 14.
The output signal of above-mentioned Numerical Control signal and I/Q distributor 4---low frequency signal multiplies each other in multiplier 6, obtains the signal of frequency recovery.
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 (6)
1, a kind of frequency recovery apparatus of digital multimedia broadcast receiver, be that signal to the specific channel that transmits by OFDM right angle frequency division multipath conversion modulation system carries out detection, with its device that is recovered to the signal of revisal frequency error and phase error, it is characterized in that constituting by following components:
The I/Q distributor, the signal of the above-mentioned transmission of gain revisal, the signal of input digit conversion is separated into real part and imaginary part with it, and to low-frequency band conversion and output;
Fast Fourier transform portion by carry out the fast Fourier transform computing in the signal of above-mentioned low-frequency band, converts the frequency field signal to;
The grade wave detector is that signal unit carries out the grade detection with above-mentioned frequency field signal, converts the signal of quadriphase PSK QPSK state to;
The 1st estimator, the time zone signal of input before the frequency field conversion of above-mentioned fast Fourier transform portion is by the numerical value of search pattern inference error;
The 2nd estimator is imported the signal of the QPSK state of above-mentioned grade wave detector output, by the numerical value of tracing mode inference error;
1st, 2 recursive filters are imported the error numerical value that above-mentioned the 1st, the 2nd estimator is inferred, according to the frequency band width of cloth that determines separately, and accumulation revisal error;
The Numerical Control oscillator generates the sine wave and the cosine wave of the numerical value correspondence of above-mentioned revisal;
Multiplier involves the signal multiplication of the low-frequency band of cosine wave and the output of above-mentioned I/Q distributor, the signal of output error revisal with the sine of above-mentioned generation.
2, the frequency recovery apparatus of digital multimedia broadcast receiver as claimed in claim 1 is characterized in that described the 2nd estimator is made of following components:
Import the output signal of described grade wave detector, the QPSK resolver of decision QPSK signal;
Import the signal of described QPSK resolver decision front and back, with two signal multiplications before and after the described resolver decision, to the multiplier of the I-of astrology dot image phase shaft rotation;
Only with the accumulator of the imaginary part in the output of described multiplier in the interval addition of effective carrier wave;
Try to achieve the averager of mean value of the numerical value of described accumulation.
3, the frequency recovery apparatus of digital multimedia broadcast receiver as claimed in claim 1 is characterized in that also comprising following structure:
Import the output signal of described I/Q distributor, delta frame and signal Synchronization signal are to the frame and the signal Synchronization portion of described fast Fourier transform portion output.
4, the frequency recovery apparatus of digital multimedia broadcast receiver as claimed in claim 1 is characterized in that also comprising following structure:
One Port Multiplier in the output valve of described the 1st, the 2nd recursive filter is selected and exported to selection signal by the outside.
5, a kind ofly use the frequency recovery method that frequency recovery apparatus as claimed in claim 1 carries out digital multimedia broadcast receiver, be that signal to the specific channel that transmits by OFDM right angle frequency division multipath conversion modulation system carries out detection, with its method that is recovered to the signal of revisal frequency error and phase error, it is characterized in that constituting by following step:
The step of digital translation is carried out in the gain of the signal of the above-mentioned transmission of revisal;
The Signal Separation of above-mentioned digital translation is become real part and imaginary part, with its step to the low-frequency band conversion;
By in the signal of above-mentioned low-frequency band, carrying out the fast Fourier transform computing, convert thereof into the step of frequency field signal;
With above-mentioned signal is that signal unit carries out the grade detection, converts the step of the signal of QPSK state to;
The time zone signal of input before above-mentioned frequency field conversion is by the step of search pattern inference error;
Import the signal of above-mentioned QPSK state, by the step of tracing mode inference error;
Import the error numerical value of above-mentioned deduction, according to the frequency band width of cloth that determines separately, the step of accumulation revisal error;
Generate the sine wave of numerical value correspondence of above-mentioned revisal and the step of cosine wave;
With the signal multiplication of the low-frequency band of the sine of above-mentioned generation and cosine wave and the output of above-mentioned I/Q distributor, the step of the signal of output error revisal.
6, the frequency recovery method of digital multimedia broadcast receiver as claimed in claim 5 is characterized in that: the error of described tracing mode infers that step also comprises following several steps:
Import the signal of described QPSK state, the step of decision QPSK signal;
Import the signal of described QPSK signal deciding front and back, with two signal multiplications before and after the described QPSK signal deciding, to the step of the I-of astrology dot image phase shaft rotation;
Only multiply each other above-mentioned, the imaginary part in the signal of output is to the step of the interval addition accumulation of effective carrier wave;
Try to achieve the step of the mean value of above-mentioned accumulation numerical value.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2005100330464A CN100527722C (en) | 2005-01-26 | 2005-01-26 | Frequency recovery apparatus and method for digital multimedia broadcasting receiver |
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2005100330464A CN100527722C (en) | 2005-01-26 | 2005-01-26 | Frequency recovery apparatus and method for digital multimedia broadcasting receiver |
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| Publication Number | Publication Date |
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| CN1812389A true CN1812389A (en) | 2006-08-02 |
| CN100527722C CN100527722C (en) | 2009-08-12 |
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| CNB2005100330464A Expired - Fee Related CN100527722C (en) | 2005-01-26 | 2005-01-26 | Frequency recovery apparatus and method for digital multimedia broadcasting receiver |
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