CN107105222A - Symbol detection circuit and method - Google Patents

Abstract

The invention provides a detection method, which is applied to a receiving end of digital video broadcasting to detect a position of a data frame of an input signal, wherein the input signal comprises a continuous wave interference component, and the method comprises the following steps: generating a correlation signal according to the input signal; performing a moving average calculation on the correlation signal to generate a first moving average result; frequency shifting the correlation signal to generate a frequency shifted correlation signal; performing moving average calculation on the frequency-shifted correlation signal to generate a second moving average result; eliminating the continuous wave interference component according to the first moving average result and the second moving average result, and generating an output signal according to the eliminating the continuous wave interference component; and judging the position according to a peak value of the output signal.

Description

Symbol detection circuit and method

technical field

The present invention relates to a symbol detection circuit and a method, in particular to a symbol detection circuit and a method of a second generation digital video broadcasting (Digital Video Broadcasting over Terrestrial 2, hereinafter referred to as DVB-T2) system.

Background technique

FIG. 1 is a schematic diagram of a T2 data frame (frame) of the second generation digital video broadcasting system, and each T2 data frame includes a P1 symbol, a P2 symbol and a data body. Among them, the P1 symbol carries some information of the transmitting end, such as the Fast Fourier Transform (FFT) mode used in data modulation, the digital communication system is Single Input Single Output (Single Input Single Output, hereinafter referred to as SISO) or Multiple Input Single Output (Multiple Input Single Output, hereinafter referred to as MISO) and other information. In addition to carrying the above-mentioned important information, the P1 symbol can also be used to detect some characteristics of the data stream, such as the starting position of the T2 data frame, carrier frequency offset (Carrier Frequency Offset, CFO), spectrum inversion (IQ swap, referred to as IQS, that is, the sine component and the cosine component are inverted) and so on.

The P1 symbol contains data C (with 542 samples and time length T _C ), data A (with 1024 samples and time length T _A ), and data B (with 482 samples and time length T _B ) . Data C is the result of the first 542 samples of data A (data C') after frequency offset, and data B is the result of the last 482 samples of data A (data B') after frequency offset, frequency offset The quantity f _SH is 1/1024T, and T is the sampling period of the T2 data frame. The P1 notation can be represented as follows:

Among them, p _1A is the content of data A.

Since data B and C are respectively generated by frequency shifting part of data A, detection unit 110 can find out the position of symbol P1 by comparing the correlation between data B, C and data A, and then obtain P1 The data in the symbol and the starting position of the T2 data frame can be known. FIG. 2 is a detailed circuit diagram of a known detection unit 110 . After the input signal enters the detection unit 110, it is multiplied by exp(-j2πf _SH nT) in one of the routes by the multiplier 310 to generate a frequency offset (the offset is -f _SH ), and is delayed by 482T in the other route through the delay unit 320 Or 542T (respectively corresponding to using data B or data C for correlation calculation). Afterwards, the multiplier 330 multiplies the conjugate of the signal after the frequency shift and the signal after the delay, and then performs a moving average operation (moving average, MA) by the filter 340 to obtain a correlated value (correlated value ) moving average. By finding the position of the maximum of the moving average of the correlation value and referring to the delay time of the delay unit 320, the initial position of the P1 symbol can be deduced. Since the frequency offset f _SH is 1/1024T, when the window length (window length) of the filter 340 is equal to the length of the data A (ie 1024T), the continuous wave (continuous wave, CW) present in the input signal can be filtered out at the same time Interference (also known as co-channel interference (CCI)), avoiding the interference of CCI on the correlation value, so as to obtain a more accurate starting position. However, this will cause the filtering time of the filter 340 to be longer; on the contrary, if the filter 340 adopts a shorter window length (such as 482T or 542T), although the correlation value can be obtained quickly, the continuous wave interference cannot be completely filtered out. . Such limitations force known circuits to make a trade-off between detection speed and accuracy.

Contents of the invention

In view of the deficiencies in the prior art, an object of the present invention is to provide a symbol detection circuit and method to improve detection speed and performance.

The present invention proposes a detection circuit, which is applied to the receiving end of digital video broadcasting to detect a position of a data frame of an input signal, the input signal includes a continuous wave interference component, the detection circuit includes: a correlation operation unit, Used to generate a correlation signal based on the input signal; a first moving average unit, coupled to the correlation calculation unit, for performing a moving average calculation on the correlation signal to generate a first moving average result; a frequency offset unit , coupled to the correlation calculation unit, used to frequency shift the correlation signal; a second moving average unit, coupled to the frequency shift unit, used to perform moving average calculation on the frequency shifted correlation signal to generate A second moving average result; a calculation unit, coupled to the first moving average unit and the second moving average unit, used to eliminate the continuous wave interference component according to the first moving average result and the second moving average result, and generate an output signal accordingly; and a judging unit, coupled to the computing unit, for judging the position according to a peak value of the output signal.

The present invention also proposes a detection method, which is applied to the receiving end of digital video broadcasting to detect a position of a data frame of an input signal, the input signal includes a continuous wave interference component, the method includes: generating a signal according to the input signal correlation signal; performing moving average calculation on the correlation signal to generate a first moving average result; frequency shifting the correlation signal to generate the frequency shifted correlation signal; performing a moving average calculation on the frequency shifted correlation signal to generate a second moving average result; eliminate the continuous wave interference component according to the first moving average result and the second moving average result, and generate an output signal accordingly; and judge the position according to a peak value of the output signal.

Compared with the known technology, the symbol detection circuit and method of the present invention adopt a shorter filtering time, and achieve the effect of simultaneously filtering continuous wave interference.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of a T2 data frame of the second generation digital video broadcasting system;

FIG. 2 is a detailed circuit diagram of a known detection unit 110;

Fig. 3 is the circuit diagram of an embodiment of the P1 symbol detection circuit of the present invention;

FIG. 4 is a detailed circuit of one of the implementations in FIG. 3;

FIG. 5 is a corresponding diagram of the input signal X[n], the delay of the input signal X[n], and the signal C_II_I[n] on the time axis;

Fig. 6 is the circuit diagram of another embodiment of P1 symbol detection circuit of the present invention;

FIG. 7 is a detailed circuit diagram of the computing unit 54;

FIG. 8 is a corresponding diagram of the input signal X[n], the delay of the input signal X[n], and the signal C_II_I[n] and the signal B_II_I[n] on the time axis;

9 is a circuit diagram of another embodiment of the P1 symbol detection circuit of the present invention;

10 is a circuit diagram of another embodiment of the P1 symbol detection circuit of the present invention; and

FIG. 11 is a schematic diagram of a P1 symbol detection circuit and a judgment circuit applied to a receiving end of a DVB-T2 system according to the present invention.

The component numbers in the figure are explained as follows:

110 detection unit

310, 330, 414, 460, 465, 55, 560, 565, 610 Multipliers

320, 412, 416, 420, 425, 440, 445 delay units

340 filter

41, 51 Related computing units

42, 43, 46, 52, 53, 56 moving average units

418, 470, 518, 570, 59 Frequency Offset Units

44, 54, 60, 70 computing units

49, 65, 66, 75 judgment circuit

430, 435, 475, 575 adders

450, 455 divider

1210 Register

1220 P1 sign detection circuit

1230 compensation circuit

1240 judgment circuit

1242, 491, 651, 661, 751 Peak Detect Unit

1244, 492, 652, 662, 752 P1 position judgment unit

1246, 653, 753 IQS detection unit

1248, 663, 754 fCFO estimation unit

Steps from S1310 to S1370

detailed description

The disclosure content of the present invention includes the symbol detection circuit and method. On the premise that the implementation is possible, those skilled in the art can select equivalent components or steps to realize the present invention according to the disclosure content of this specification, that is, the Implementation is not limited to the examples described below.

Assume that the input signal X[n] of the DVB-T2 receiver is expressed as follows:

X[n]＝P ₁ [n-θ]·exp(j2πΦnT _S )+exp(j2πf _CW nT _S ) (1)

Among them, P ₁ [n-θ]·exp(j2πΦnT _S ) is the part of P1 symbol, θ represents the sampling delay, Φ is the carrier frequency offset; exp(j2πf _CW nT _S ) is the continuous wave of single-tone interference (frequency f _CW ). For ease of illustration, channel effects and noise are ignored here. Delay X[n] by T _C (that is, the length of the delayed data C, 542 samples), and then multiplied by its own conjugate, the signal C_I_0[n] can be obtained:

C_I_0[n]=X[nn _c ]·X ^* [n]=exp(-j2πf _CW T _C )·1+|P ₁ [n-θ]| ² ·exp(-j2π(f _SH +Φ)T _C )·exp(j2πf _SH nT _S )+…(2)

Wherein, the residual term "..." is orthogonal to 1 and exp(j2πf _SH nT _S ). After delaying the signal C_I_0[n] by 2T _B (that is, twice the length of the delayed data B, 964 samples), the signal C_I[n] can be obtained:

C_I[n]=C_I_0[n-2n _B ]=exp(-j2πf _CW T _C )·1+|P ₁ [n-2n _B -θ]| ² ·exp(-j2π(f _SH +Φ)T _C )·exp(-j4πf _SH T _B )·exp(j2πf _SH nT _S )+…(3)

Simplify equation (3) to the following:

C_I[n]=a_C·1+b_C·ρ ⁿ +...(4)

Among them, a_C=exp(-j2πf _CW T _C ) is the part of continuous wave interference, b_C=|P ₁ [n-2n _B -θ]/2·exp-j2πfSH+ΦTC·exp(-j4πfSHTB) is the part of P1 symbol part, ρ=expj2πfSHTS.

Next, C_I[n] is accumulated at 542 consecutive sampling points (corresponding to the delay time T _C of the input signal X[n] in equation (2)), and the signal C_S[n] can be obtained:

C_S[n]=C_I[n]+C_I[n-1]+...+C_I[n-542+1]

＝542·a_C+b_C·ρn- ^(542-1)/2 ·(ρ ^(542-1)/2 +ρ ^(542-1)/2-1 +...+ρ ^(1-542)/2 )

=542·a_C+b_C·ρn- ^(542-1)/2 ·λ (5)

in

Among them, it is assumed that π/1024 tends to 0, so the approximately When L=542 or 482, the value of λ is about 324.5686967.

On the other hand, after shifting the frequency of the signal C_I[n] by -f _SH (i.e. multiplied by exp(-j2πf _SH nT _S )), the input signal X[n ] The delayed time T _C ) is accumulated to obtain the signal:

C_T1[n]=ρ ^-n C_I[n]+ρ ^-(n-1 ) C_I[n-1]+...+ρ ^-(n-542+1) C_I[n-542+1

＝542·b_C+a_C·ρ ^(542-1)/2-n ·(ρ ^(542-1)/2 +ρ ^(542-1)/2-1 +...+ρ ^(1-542)/2 )

=542 b_C+a_C ρ ^(542-1)/2-n λ (6)

The above equation (5) and equation (6) can be rewritten as the following equation (7) and equation (8) respectively:

ρ ^(542-1)/2-n C_S[n]=542 a_C ρ ^(542-1)/2-n +b_C λ (7)

C_T1[n]=542 b_C+a_C ρ ^(542-1)/2-n λ (8)

Express equation (7) and equation (8) in matrix form:

It can be found from Equation (9) that after the signal C_S[n] is frequency shifted, the component b_C corresponding to the P1 symbol can be obtained by linear operation with the signal C_T1[n], that is, the component a_C that can remove the continuous wave interference. This linear operation is fairly easy to implement on a circuit, as shown in Figure 3.

FIG. 3 is a circuit diagram of an embodiment of the P1 symbol detection circuit of the present invention. Correlation operation unit 41 can realize equation (2), and moving average unit 42 carries out moving average operation to the continuous 542 sampling points of signal C_I_0[n]. The frequency offset unit 418 can be implemented by a multiplier or implemented by a central processing unit, a microcontroller, etc. to perform frequency offset operations) The continuous 542 sampling points of the signal C_I_0[n] perform a moving average operation . The calculation unit 44 calculates the output of the moving average unit 42 and the moving average unit 43 to obtain the signal C_II_I[n] from which the continuous wave interference has been removed. Finally, the judging circuit 49 can deduce the starting position of the data A of the input signal X[n] according to the position of a maximum value of the signal C_II_I[n].

FIG. 4 is a detailed circuit of one embodiment of FIG. 3 . The correlation operation unit 41 includes a delay unit 412 and a multiplier 414 . The moving average unit 42 includes an accumulating unit and an averaging unit. The accumulating unit includes the delay unit 420 , the adder 430 and the delay unit 440 shown in FIG. 4 , and the averaging unit is implemented by a divider 450 . Similarly, the moving average unit 43 includes an accumulation unit and an averaging unit, the accumulation unit includes the delay unit 425 , the adder 435 and the delay unit 445 shown in FIG. 4 , and the averaging unit is implemented by the divider 455 . The calculation unit 44 includes a multiplier 460 , a multiplier 465 , a frequency offset unit 470 and an adder 475 in FIG. 4 . The judging circuit 49 includes a peak detection unit 491 and a P1 position judging unit 492 .

The delay unit 412 and the multiplier 414 can implement equation (2). The delay unit 420 , the adder 430 and the delay unit 440 accumulate consecutive 542 sampling points of the signal C_I_0[n] to obtain the signal C_S[n]. On the other hand, the delay unit 425, the adder 435 and the delay unit 445 accumulate the continuous 542 sampling points of the signal C_I_0[n] after the frequency offset (executed by the frequency offset unit 418) to obtain the signal C_T1[n] . After obtaining the signal C_S[n] and the signal C_T1[n], the equation (9) can be obtained by the divider 450 (divided by 542), the divider 455 (divided by 542), the multiplier 460 (multiplied by -0.934), multiplication 465 (multiplied by 1.559), frequency offset unit 470 (to generate frequency offset for signal C_S[n]) and adder 475 to obtain signal C_II_I[n] from which CW interference has been removed.

The peak detection unit 491 detects the peak value (i.e. the maximum correlation value) of the signal C_II_I[n], and transmits the position of the peak value to the P1 position judgment unit 492, and the P1 position judgment unit 492 is based on the delay applied by the previous stage circuit to the input signal (for example, 542T _S or 482T _S ), and calculate the correct position of the P1 symbol in the T2 data frame.

FIG. 5 is a corresponding diagram of the input signal X[n], the delayed input signal X[n], and the signal C_II_I[n] on the time axis. Because in the circuit of FIG. 3 or FIG. 4, the delay unit 412 in the correlation operation unit 41 delays the input signal X[n] by 542Ts, just makes the data C of the delayed input signal X[n] and the input signal The first half of the data A of X[n] overlaps, so the input signal X[n] is calculated by the correlation calculation unit 41, the frequency offset unit 418, the moving average unit 42, the moving average unit 43, and the calculation unit 44 to generate The signal C_II_I[n] of the signal C_II_I[n] will have a maximum value as time changes, and the initial position of the data A of the input signal X[n] can be deduced from the position of the maximum value. The circuits in Fig. 3 and Fig. 4 overlap the first half of the data A of the input signal X[n] with the data C for correlation calculation, so a window length of 542T _S is required to effectively generate the maximum value; similarly, in another In one embodiment, the second half of the data A of the input signal X[n] can also be overlapped with the data B to perform correlation calculation, so only a window length of 482T _S is needed to effectively generate the maximum value.

Compared with the known detection unit 110, the P1 symbol detection circuit of the present invention has at least the following features:

The known window length of the filter 340 of the detection unit 110 must be 1024T _S to filter the continuous wave interference, while the filter in Fig. 3 (ie, the moving average unit 42 and the moving average unit 43) only needs a window length of 542T _S (processing data C) or the window length (processing data B) of _482TS , so the present invention can greatly save the processing time of the filter while not reducing the detection accuracy;

The filter signal output by the filter 340 of the known detection unit 110 has no continuous wave interference component, and although the filter signal output by the filter of the present invention still has a continuous wave interference component, the calculation unit 44 executes the equation ( Part of the multiplication and addition operations in 9) is to extract the component b_C of the P1 symbol from the two filtered signals output by the moving average unit 42 and the moving average unit 43, so as to filter out the components of the continuous wave interference. Except for the processing of the frequency offset, the coefficients used by the calculation unit 44 are all real numbers, so it is easy to realize on the circuit, and the cost is relatively low; and

In the correlation operation performed by the known detection unit 110, one of the two signals has a frequency offset from the input signal (the offset is -f _SH , executed by the multiplier 310); and the correlation operation of the present invention The two signals multiplied by the characteristic operation unit 41 (ie, the two input signals of the multiplier 414 ) have no frequency offset compared with the input signal X[n].

FIG. 6 is a circuit diagram of another embodiment of the P1 symbol detection circuit of the present invention. The circuit in FIG. 6 includes two paths. The circuit in the upper path is similar to the circuit shown in FIG. 4 (only the delay unit 416 is added), and outputs the signal C_II_I[n] after processing the input signal X[n]. The lower path is also similar to the circuit shown in FIG. 4 , which processes the input signal X[n] and outputs the signal B_II_I[n]. The detailed circuit of the correlation operation unit 51 is the same as that of the correlation operation unit 41, but its delay unit is a delay of 482T _S instead of 542T _S . So the signal B_I[n] is represented as follows:

B_I[n]＝exp(-j2πf _CW T _B )·1+|P ₁ [n-θ]| ² ·exp(-j2πΦT _B )·exp(-j2πf _SH nT _S )+...(10)

Similarly, on the one hand, the signal B_I[n] is directly calculated by the moving average unit 52, and on the other hand, after the frequency offset (the frequency offset f _SH is applied by the frequency offset unit 518, and multiple conjugate operations are performed ) is calculated by the moving average unit 53 again. Please note that the window lengths of the moving average unit 52 and the moving average unit 53 are both 482T _S (corresponding to the delay time 482T _S of the correlation calculation unit 51 ). The last two signals are calculated by the calculation unit 54 to obtain the signal B_II_I[n]. The circuit of calculation unit 54 is the same as calculation unit 44, but the coefficients are different, as shown in Figure 7, the output of moving average unit 52 is multiplied by multiplier 560 by -1.232 and then frequency offset is carried out by bias rate offset unit 570; After the output of the averaging unit 53 is multiplied by 1.830 by the multiplier 565 , it is added to another signal in the adder 575 to form the signal B_II_I[n]. The coefficient and the frequency offset used by the calculation unit 54 can be obtained by the following derivation:

First simplify equation (10) to the following formula:

B_I[n]=a_B·1+b_B·ρ- ⁿ +...(11)

Among them, a_B=exp(-j2πf _CW T _B ) is the part of continuous wave interference, b_B=|P ₁ [n-θ]| ² exp(-j2πΦT _B ) is the part of P1, ρ=exp(j2πf _SH T _S ).

Next, accumulate B_I[n] at 482 consecutive sampling points (corresponding to the delay time T _B =482T _S of the input signal X[n] in equation (10)), and the signal B_S[n] can be obtained:

B_S[n]=B_I[n]+B_I[n-1]+...+B_I[n-482+1]

=482·a_B+b_B·(ρ ^* ) ^n-(482-1)/2 ·λ (12)

On the other hand, after shifting the frequency of the signal B_I[n] by f _SH (that is, multiplying by exp(j2πf _SH nT _S )), and then accumulating at 482 consecutive sampling points, the signal can be obtained:

B_T1[n]=ρ ⁿ B_I[n]+ρ ^(n-1) B_I[n-1]+…+ρ ^(n-482+1) B_I[n-482+1

=482 b_B+a_B (ρ ^* ) ^(482-1)/2-n λ (13)

The above equation (12) and equation (13) can be rewritten as the following equation (14) and equation (15) respectively:

ρ ^n-(482-1)/2 B_S[n]=482 a_B ρ ^n-(482-1)/2 +b_B λ (14)

B_T1[n]=482 b_B+a_B ρ ^n-(482-1)/2 λ (15)

Express equation (14) and equation (15) in matrix form:

In this way, the coefficients and frequency offset used by the calculation unit 54 can be obtained, and it is also proved that the signal B_II_I[n] finally output by the calculation unit 54 has removed the component a_B of continuous wave interference, leaving only the component b_B corresponding to the P1 symbol.

FIG. 8 is a corresponding diagram of the input signal X[n], two sets of delayed input signals X[n], and the signal C_II_I[n] and the signal B_II_I[n] on the time axis. Signal B_II_I[n] is a correlation operation based on data _B , so a maximum value will be generated at time 2TA. Because the detection circuit in FIG. 6 includes a delay unit 416, the maximum value of the signal C_II_I[n] also falls at the time 2T _A , so the signal after multiplying the signal C_II_I[n] and the signal B_II_I[n] (that is, the signal P1_no_IQS[n]) will have a more obvious peak at 2T _A , which is beneficial to the judgment of the subsequent circuit.

The judging circuit 66 in FIG. 6 includes a peak detection unit 661 , a P1 position judging unit 662 and an fCFO estimating unit 663 . The peak detection unit 661 detects the peak value of the signal P1_no_IQS[n] (at this time, a more accurate judgment result than the signal C_II_I[n] can be obtained), and the fCFO estimation unit 663 obtains the carrier frequency deviation of the input signal from the signal P1_no_IQS[n] In more detail, calculate the argument of the signal P1_no_IQS[n]:

Arg(P1_no_IQS[n])=Arg(b_C·b_B)

＝-2π·(T _B ·f _SH +T _A ·Φ)

Therefore, the fractional CarrierFrequency Offset (fCFO) of the input signal X[n] can be obtained:

From the above analysis, it can be seen that the P1 symbol detection circuit shown in FIG. 6 uses the upper path and the lower path to perform correlation operations on the data C and data B of the P1 symbol respectively to obtain the signal C_II_I[n] and the signal B_II_I[n]. Finally, the signal P1_no_IQS[n] obtained by multiplying the signal C_II_I[n] and the signal B_II_I[n] through the multiplier 55 has a more obvious peak to facilitate finding the position of the maximum correlation value, and can also be obtained according to In order to know the fractional part of the carrier frequency offset of the input signal X[n].

The above discussion is based on the fact that the spectrum operation preset by the receiving end is consistent with the signal spectrum sent by the transmitting end, that is, there is no spectrum frequency inversion. However, the present invention also proposes a P1 symbol detection circuit that can detect spectrum inversion at the same time . FIG. 9 is a circuit diagram of another embodiment of the P1 symbol detection circuit of the present invention. In addition, this circuit uses the moving average unit 56 to process the frequency shifted signal C_I[n] (the frequency shift unit 59 performs frequency shift and multiple conjugate operations), and then calculates through the calculation circuit 60 to obtain the signal C_II_II[ n]. Therefore, the judgment circuit 65 of the subsequent stage can know whether the spectrum of the input signal X[n] is inverted according to which one of the signal C_II_I[n] and the signal C_II_II[n] has a larger maximum correlation value (the same principle can be applied to the signal B_II_I[n] and signal B_II_II[n]). The peak detection unit 651 of the judging circuit 65 detects the peak values of the signal C_II_I[n] and the signal C_II_II[n] at the same time, and then sends the positions of the two peaks to the P1 position judging unit 652, and the magnitudes of the two peaks (i.e. take absolute values) The IQS detection unit 653 compares the magnitude of the two peaks to know whether there is spectrum inversion, and the compensation circuit in the subsequent stage determines the correct position of the P1 symbol based on this information and the output of the P1 position determination unit 652.

FIG. 10 is a circuit diagram of another embodiment of the P1 symbol detection circuit of the present invention. Signal C_II_I[n] and signal C_II_II[n] (signal B_II_I[n] and signal B_II_II[n] are the same as signal B_II_II[n]) are related signals corresponding to spectrum non-inversion and spectrum inversion respectively, and both have removed continuous wave interference , that is to say, the co-channel interference suffered by the input signal X[n] can be solved after the calculation of the calculation unit 60 and the calculation unit 70 (the circuit is the same as that of the calculation unit 60, and the coefficients can refer to FIG. 7 ). . The waveform diagram of the corresponding time between signal C_II_I[n] (or C_II_II[n]) and signal B_II_I[n] (or B_II_II[n]) is shown in Figure 8, because the signal C_II_I[n] (or C_II_II[n]) is delayed 964T _S , so the signal P1_no_IQS[n] (or P1_IQS[n]) multiplied by the signal B_II_I[n] (or B_II_II[n]) has a more obvious maximum value to facilitate the judgment circuit interpretation of the subsequent stage . In addition, the judging circuit can know whether the input signal X[n] has spectrum inversion by comparing the maximum value of P1_no_IQS[n] and P1_IQS[n]. One, to obtain the carrier frequency offset of the input signal X[n] (as shown in equation (17)). The judgment circuit 75 of FIG. 10 includes a peak detection unit 751, a P1 position judgment unit 752, an IQS detection unit 753, and an fCFO estimation unit 754, wherein the fCFO estimation unit 754 is the same as the fCFO estimation unit 663 of the embodiment in FIG. The signal P1_no_IQS[n] obtains the carrier frequency offset of the input signal. However, the fCFO estimation unit 754 in the embodiment shown in FIG. The determination circuit 75 performs other determinations on the signal P1_no_IQS[n] and the signal P1_IQS[n], which have been described in detail of each functional unit, and thus will not be repeated here.

FIG. 11 is a schematic diagram of a P1 symbol detection circuit and a judgment circuit applied to a receiving end of a DVB-T2 system according to the present invention. The compensation circuit 1230 adjusts/compensates the input signal temporarily stored in the register 1210 according to the determination result of the determination circuit 1240 , so that the subsequent circuit (such as an FFT operation unit, etc.) can process the correct input signal. The functional units included in the judging circuit 1240 have been introduced previously, so details are not repeated here.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims.

Claims (20)

1. one kind detection circuit, applied to the receiving terminal of DVB to detect a number of an input signal According to a position of frame, the input signal includes a continuous wave CO_2 laser composition, and the detection circuit is included：

One correlation operation unit, for producing a coherent signal according to the input signal；

One first rolling average unit, couples the correlation operation unit, for being moved to the coherent signal Average computation is moved to produce one first rolling average result；

One frequency shift (FS) unit, couples the correlation operation unit, for the frequency shift (FS) coherent signal；

One second rolling average unit, couples the frequency shift (FS) unit, for the correlation after frequency shift (FS) Signal moves average computation to produce one second rolling average result；

One computing unit, couples the first rolling average unit and the second rolling average unit, for foundation The first rolling average result and the second rolling average result eliminate the continuous wave CO_2 laser composition, and produce according to this A raw output signal；And

One judging unit, couples the computing unit, and the position is judged for the peak value according to the output signal.

2. circuit is detected as claimed in claim 1, it is characterised in that the correlation operation unit is foundation The conjugated signal of the input signal and the input signal after delay produces the coherent signal.

3. circuit is detected as claimed in claim 1, it is characterised in that the data frame has a symbol, should Symbol carries a modulation intelligence of the input signal, and the first rolling average unit and second rolling average The Window length of unit is less than the half of the time span of the symbol.

4. circuit is detected as claimed in claim 1, it is characterised in that the first rolling average result is with being somebody's turn to do Second rolling average result is to include the continuous wave CO_2 laser composition.

5. circuit is detected as claimed in claim 1, it is characterised in that the frequency shift (FS) unit is one first Frequency shift (FS) unit, the detection circuit is further included：

One another correlation operation unit, for producing an another coherent signal according to the input signal；

One the 3rd rolling average unit, couples another correlation operation unit, for another related letter Number move average computation to produce one the 3rd rolling average result；

One second frequency offset units, couple another correlation operation unit, this is another for frequency shift (FS) Coherent signal；

One the 4th rolling average unit, couples the second frequency offset units, for being somebody's turn to do after frequency shift (FS) Another coherent signal moves average computation to produce one the 4th rolling average result；

One another computing unit, couples the 3rd rolling average unit and the 4th rolling average unit, is used for The continuous wave CO_2 laser composition is eliminated according to the 3rd rolling average result and the 4th rolling average result, and is produced A raw another output signal；And

One multiplier, is coupled to the computing unit and another computing unit, for by the output signal and should Another output signal is multiplied to produce an echo signal；

Wherein, the judging unit judges the position according to a peak value of the echo signal.

6. circuit is detected as claimed in claim 5, it is characterised in that the judging unit is more according to the target Signal judges a carrier frequency shift of the input signal.

7. circuit is detected as claimed in claim 1, it is characterised in that the output signal is one first output Signal, the frequency shift (FS) unit is a first frequency offset units, and the detection circuit is further included：

One second frequency offset units, couple the correlation operation unit, for the frequency shift (FS) coherent signal；

One the 3rd rolling average unit, couples the correlation operation unit, for the phase after frequency shift (FS) The conjugated signal of OFF signal moves average computation to produce one the 3rd rolling average result；

Wherein, the computing unit more couples the 3rd rolling average unit, and more flat according to first movement Result and the 3rd rolling average result eliminate the continuous wave CO_2 laser composition, and one second output signal of generation, And the judging unit more judges the one of the input signal according to first output signal and second output signal Reversing spectrum information.

8. detection circuit, is further included as claimed in claim 7：

One another correlation operation unit, for producing an another coherent signal according to the input signal；

One the 4th rolling average unit, couples another correlation operation unit, for another related letter Number move average computation to produce one the 4th rolling average result；

One the 3rd frequency shift (FS) unit, couples another correlation operation unit, this is another for frequency shift (FS) Coherent signal；

One the 5th rolling average unit, couples the 3rd frequency shift (FS) unit, for being somebody's turn to do after frequency shift (FS) Another coherent signal moves average computation to produce one the 5th rolling average result；

One the 4th frequency shift (FS) unit, couples another correlation operation unit, this is another for frequency shift (FS) Coherent signal；

One the 6th rolling average unit, couples the 4th frequency shift (FS) unit, for being somebody's turn to do after frequency shift (FS) The conjugated signal of another coherent signal moves average computation to produce one the 6th rolling average result；

One another computing unit, couple the 4th rolling average unit, the 5th rolling average unit and this Six rolling average units, should for being eliminated according to the 4th rolling average result, the 5th rolling average result Continuous wave CO_2 laser composition, and one the 3rd output signal is produced according to this, and for according to the 4th rolling average As a result, the 6th rolling average result eliminates the continuous wave CO_2 laser composition, and produces one the 4th output letter according to this Number；

One first multiplier, is coupled to the computing unit and another computing unit, for this first is exported Signal and the 3rd output signal are multiplied to produce a first object signal；And

One second multiplier, is coupled to the computing unit and another computing unit, for this second is exported Signal and the 4th output signal are multiplied to produce one second echo signal；

Wherein, the judging unit is according to a peak value of the first object signal and a peak of second echo signal Value judges the positional information.

9. as claimed in claim 8 detection circuit, it is characterised in that the judging unit more according to this first Echo signal and second echo signal judge a carrier frequency shift of the input signal.

10. detection circuit as claimed in claim 8, it is characterised in that the judging unit more according to this At least one of one echo signal and second echo signal judge a reversing spectrum of the input signal Information.

11. detection circuit is to be applied to a second generation digital video broadcast system as claimed in claim 1 (DVB-T2)。

12. a kind of detection method, applied to the receiving terminal of DVB to detect the one of an input signal One position of data frame, the input signal includes a continuous wave CO_2 laser composition, and this method is included：

A coherent signal is produced according to the input signal；

Average computation is moved to the coherent signal to produce one first rolling average result；

The frequency shift (FS) coherent signal is to produce the coherent signal after frequency shift (FS)；

Average computation is moved to the coherent signal after frequency shift (FS) to produce one second rolling average knot Really；

The continuous wave CO_2 laser composition is eliminated according to the first rolling average result and the second rolling average result, And an output signal is produced according to this；And

A peak value according to the output signal judges the position.

13. detection method as claimed in claim 12, it is characterised in that this is produced according to the input signal The step of one coherent signal is to produce to be somebody's turn to do with the conjugated signal of the input signal according to the input signal of delay Coherent signal.

14. detection method as claimed in claim 12, it is characterised in that the data frame has a symbol, The symbol carries a modulation intelligence of the input signal, and produces the one of the first rolling average result according to this One Window length is less than the symbol with producing one second Window length of the second rolling average result according to this The half of time span.

15. detection method as claimed in claim 12, it is characterised in that the first rolling average result with The second rolling average result is to include the continuous wave CO_2 laser composition.

16. detection method as claimed in claim 12, is further included：

An another coherent signal is produced according to the input signal；

Average computation is moved to another coherent signal to produce one the 3rd rolling average result；

Frequency shift (FS) another coherent signal is to produce another coherent signal after frequency shift (FS)；

It is flat to produce one the 4th movement to move average computation to another coherent signal after frequency shift (FS) Equal results；

The continuous wave CO_2 laser composition is eliminated according to the 3rd rolling average result and the 4th rolling average result, And produce an another output signal；

The output signal and another output signal are multiplied to produce an echo signal；And

A peak value according to the echo signal judges the position.

17. detection method as claimed in claim 16, further includes and judges that the input is believed according to the echo signal Number a carrier frequency shift.

18. detection method as claimed in claim 12, it is characterised in that the output signal is one first defeated Go out signal, this method is further included：

The conjugated signal of the coherent signal after the frequency shift (FS) is moved average computation to produce one Three rolling average results；

The continuous wave CO_2 laser composition is eliminated according to the first rolling average result and the 3rd rolling average result, And produce one second output signal；And

The reversing spectrum letter of the input signal is judged according to first output signal and second output signal Breath.

19. detection method as claimed in claim 18, is further included：

An another coherent signal is produced according to the input signal；

Average computation is moved to another coherent signal to produce one the 4th rolling average result；

Frequency shift (FS) another coherent signal is to produce another coherent signal after frequency shift (FS)；

It is flat to produce one the 5th movement to move average computation to another coherent signal after frequency shift (FS) Equal results；

The conjugated signal of another coherent signal after frequency shift (FS) is moved average computation to produce one 6th rolling average result；

The continuous wave CO_2 laser composition is eliminated according to the 4th rolling average result, the 5th rolling average result, And one the 3rd output signal and according to the 4th rolling average result, the 6th rolling average knot is produced according to this Fruit eliminates the continuous wave CO_2 laser composition, and produces one the 4th output signal according to this；

First output signal and the 3rd output signal are multiplied to produce a first object signal；

Second output signal and the 4th output signal are multiplied to produce one second echo signal；And

Judge the position according to a peak value of the first object signal and a peak value of second echo signal.

20. detection method as claimed in claim 12 is to be applied to a second generation digital video broadcast system (DVB-T2)。