CN103391269B - The method of 8QAM receiver and extraction local carrier-phase error thereof - Google Patents

Abstract

The present invention is applicable to satellite communication, satellite remote sensing, satellite broadcasting ground digital reception technique field, provides a kind of method of 8QAM receiver and extraction local carrier-phase error thereof; Described method comprises the steps: steps A, obtains I road range value yR and the Q road range value yI of the actual constellation point received; Step B, according to following formulas Extraction local carrier-phase error E (y): E (y)=sign (EyR) sign (yI)-sign (EyI) sign (yR), wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value; <maths num=" 0001 " > </maths><maths num=" 0002 " > compared with prior art, the calculating of whole carrier phase error is quite simple, only can realize with several adder and simple hardware logic in </maths> the present invention.

Description

The method of 8QAM receiver and extraction local carrier-phase error thereof

Technical field

The invention belongs to satellite communication, satellite remote sensing, satellite broadcasting ground digital reception technique field, particularly relate to a kind of method of 8QAM receiver and extraction local carrier-phase error thereof.

Background technology

In satellite digital communication system, in order to transmit the signal of more high data rate in limited bandwidth chahnel, fully must weigh the probability of spectrum efficiency and symbol error, the probability of symbol error uses Eb/N0 (EnergypertransmittedbitversustheNoisespectraldensity usually, bit signal to noise ratio) specify, in satellite communication system, conventional modulation system has PSK (Phase-ShiftKeying, phase shift keying), QAM (QuadratureAmplitudeModulation, quadrature amplitude modulation), APSK (AmplitudePhase-ShiftKeying, APK amplitude phase shift keying), wherein, PSK modulation technique has again BPSK (BinaryPhase-ShiftKeying, two-phase PSK), QPSK (QuadraturePhase-ShiftKeying, Quadrature Phase Shift Keying), OQPSK (Offset-QPSK, offset quadraphase shift keying), 8PSK (eight phase phase shift keyings) divides, QAM modulation technology has again 8QAM (eight rank quadrature amplitude modulation), 16QAM (16 rank quadrature amplitude modulation) divides, APSK modulation technique has again 16APSK (16 rank APK amplitude phase shift keying), 32APSK (30 second order APK amplitude phase shift keying) divides.

QAM and the APSK modulation system of high-order can provide higher spectrum efficiency for the signal of Bandwidth-Constrained, for qam signal, the state of its more specific amplitude/phase is used to representative information bit, these states form the figure of a constellation point in reference axis, and each state point in constellation point can be mapped to one group of special Bit data, this mapping relations are comparatively diversified, and suitable selection constellation point and mapping relations can reduce the probability of symbol error.

The constellation point of PSK modulation system is equally spacedly distributed in circumferentially, and along with the increase of order of modulation, Distance Shortened between its constellation point (cannot increase distance between constellation point by increasing power when transmit power limited.Usually in satellite link, there is multiple carrier signal, in order to avoid the interference between adjacent channel, high power amplifier (HPA) should be avoided being operated in nonlinear state, so transmitting power is limited), such as 8PSK, in noise circumstance, the ability reduction of constellation point belonging to certain received signal points differentiated by receiver, and the probability of symbol error increases, under identical Eb/N0, its bit error rate can be higher.So for this situation, use 8QAM modulation system can be a kind of better selection, they have identical spectrum efficiency 3bits/s/Hz, and the constellation point distribution of 8QAM is more reasonable, make under equal launching condition, the likelihood ratio 8PSK of its symbol error is low.

Compensate local carrier-phase error needing during 8QAM demodulation, to realize the tracking of local carrier to the modulation signal carrier wave received, but the realizing circuit of current carrier track is comparatively complicated, is unfavorable for the miniaturization of product, is also unfavorable for saving cost.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of 8QAM to extract the method for local carrier-phase error, is intended to the calculating realizing carrier phase error with simple hardware logic.

The present invention is achieved in that a kind of 8QAM extracts the method for carrier phase error, and described method comprises the steps:

Steps A, obtains I road range value yR and the Q road range value yI of the actual constellation point received;

Step B, according to following formulas Extraction local carrier-phase error E (y):

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ -1& 0>yR\&GreaterEqual;-2\\ -3& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ -1& 0>yI\&GreaterEqual;-2\\ -3& -2>yI\end{array}\right\}.$

Present invention also offers a kind of 8QAM receiver, it is characterized in that, comprising: complex multiplier, for the modulated signal of reception and local carrier signal are carried out complex multiplication, export baseband I road signal and base band Q road signal;

Decimation filter, is connected with described complex multiplier, for by the processing clock rate reduction of described baseband I road signal and base band Q road signal to 2 times of symbol clock speed;

Matched filter, is connected with described decimation filter, for exporting I road range value yR and the Q road range value yI of the actual constellation point received;

Decoder, is connected with described matched filter, for carrying out decoding process to described I road range value yR and Q road range value yI;

Carrier track restore circuit, be connected between described matched filter and described complex multiplier, for according to following formulas Extraction local carrier-phase error E (y), and according to E (y), the phase error of local carrier is compensated, then export the local carrier after compensating to described complex multiplier:

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ -1& 0>yR\&GreaterEqual;-2\\ -3& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ -1& 0>yI\&GreaterEqual;-2\\ -3& -2>yI\end{array}\right\}.$

The present invention compared with prior art, the calculating of whole carrier phase error is quite simple, only can realize with several adder and simple hardware logic, on original basis not possessing the demodulator of 8QAM demodulation function, so just can increase the demodulation function of 8QAM easily.

Accompanying drawing explanation

Fig. 1 is the architecture principle figure of modulation demodulation system provided by the invention;

Fig. 2 A and Fig. 2 B is 8QAM constellation point relation and 8PSK constellation point relation schematic diagram respectively;

Fig. 3 is the structure principle chart of 8QAM transmitter provided by the invention;

Fig. 4 is the structure principle chart of 8QAM receiver provided by the invention;

Fig. 5 is the structure principle chart of carrier track restore circuit in Fig. 4;

Fig. 6 is the structure principle chart of carrier phase error extraction module in Fig. 5.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

Fig. 1 shows the architecture principle of modulation demodulation system provided by the invention, for convenience of description, illustrate only part related to the present invention.

With reference to Fig. 1, modulation demodulation system provided by the invention comprises 8QAM transmitter 1 and 8QAM receiver 2,8QAM transmitter 1 for carrying out data encoding, is then gone out by antenna transmission after modulation.After 8QAM receiver 2 receives modulation signal, process obtains baseband I road signal and base band Q road signal, then decoding.Above-mentioned modulation demodulation system is applicable to 8QAM technology, and the constellation point relation of 8QAM as shown in Figure 2 A, can find out that constellation point relation is different from the 8PSK technology shown in Fig. 2 B.

Fig. 3 shows the structural principle of above-mentioned 8QAM transmitter 1, and with encoder 11 for generation of forward error correction, the LDPC (other forward error corrections are applicable equally) that such as error correcting capability is extremely strong, encoder 11 exports bit sequence (b after encoding _3i, b _3i+1, b _3i+2), wherein, i=0,1,2,3 ..., 3 one group is because what adopt below is the modulation system of 8QAM, in the process through 8QAM constellation point module 12, exports the quadrature amplitude value after mapping; To modulate finally by 8QAM modulator 13 and after high power amplifier 14 carries out power amplification, from this signal of antenna transmission.

Fig. 4 shows the structural principle of above-mentioned 8QAM receiver 2, comprise complex multiplier 21, decimation filter 22, matched filter 23, decoder 24 and carrier track restore circuit 25, wherein, complex multiplier 21, decimation filter 22, matched filter 23, decoder 24 connect in turn.Complex multiplier 21 is for carrying out complex multiplication by the modulated signal of reception and local carrier signal, export baseband I road signal and base band Q road signal, decimation filter 22 by the processing clock rate reduction of baseband I road signal and base band Q road signal to 2 times of symbol clock speed.Then matched filter 23 exports I road range value yR and the Q road range value yI of the actual constellation point received, then carries out decoding process by decoder 24 couples of I road range value yR and Q road range value yI.

Carrier track restore circuit 25 is connected between matched filter 23 and complex multiplier 21, for extracting local carrier-phase error E (y), and according to E (y), the phase error of local carrier is compensated, then export the local carrier after compensating to complex multiplier 21.In the present invention, carrier track restore circuit 25 is according to following formulas Extraction local carrier-phase error E (y):

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ -1& 0>yR\&GreaterEqual;-2\\ -3& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ -1& 0>yI\&GreaterEqual;-2\\ -3& -2>yI\end{array}\right\}.$

Particularly, the structure of carrier track restore circuit 25 as shown in Figure 5, comprise: carrier phase error extraction module 251, second-order loop filter 252, digital controlled oscillator 253, carrier phase error extraction module 251 is for according to following formulas Extraction local carrier-phase error E (y):

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ -1& 0>yR\&GreaterEqual;-2\\ -3& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ -1& 0>yI\&GreaterEqual;-2\\ -3& -2>yI\end{array}\right\};$

Second-order loop filter 252 is connected with carrier phase error extraction module, for carrying out integration to carrier phase error E (y), is equivalent to the effect of a low pass filter.Digital controlled oscillator 253 is connected with second-order loop filter 252 again, for adjusting the phase place of the local carrier that it exports according to the output of second-order loop filter 252, realize compensating the phase error of local carrier, then export the local carrier after compensation of phase to complex multiplier 21.

Further, Fig. 6 shows a kind of concrete structure of carrier phase error extraction module 251, comprises the first decision device 501, first adder 502, a sign function module 503, the 2nd sign function module 504, first multiplier 505, second decision device 506, second adder 507, the 3rd sign function module 508, the 4th sign function module 509, second multiplier 510 and the 3rd adder 511.The operation principle of each device/module is as follows.

The input matching connection filter 23 of the first decision device 501, for receiving the I road range value yR of the actual constellation point received, exports the first hard-decision values DyR according to such as under type, $DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ -1& 0>yR\&GreaterEqual;-2\\ -3& -2>yR\end{array}\right\},$ The position of the constellation point shown in its operation principle to Fig. 2 A is relevant.An input matching connection filter of first adder 502, receive the I road range value yR of the actual constellation point received, another input connects the output of the first decision device, for by poor for I road range value yR and the first hard-decision values DyR, obtains difference EyR.The input of the one sign function module 503 is connected with the output of first adder 502, for extracting the symbol of difference EyR.The input of the 2nd sign function module 504 is connected with the output of matched filter 23, for receiving the Q road range value yI of the actual constellation point received, extracts the symbol of Q road range value yI.Two inputs of the first multiplier 505 connect the output of a sign function module 503 and the output of the 2nd sign function module 504 respectively, and the symbol for the difference EyR by extraction is multiplied with the symbol of Q road range value yI, obtains the first product.The input matching connection filter 23 of the second decision device 506, for receiving the Q road range value yI of the actual constellation point received, exports the second hard-decision values DyI according to such as under type, $DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ -1& 0>yI\&GreaterEqual;-2\\ -3& -2>yI\end{array}\right\},$ In like manner, its operation principle is also relevant to the position of the constellation point shown in Fig. 2 A.An input matching connection filter 23 of second adder 507, receive the Q road range value yI of the actual constellation point received, another input connects the output of the second decision device 506, for by poor for Q road range value yI and the second hard-decision values DyI, obtains difference EyI.The input of the 3rd sign function module 508 is connected with the output of second adder 507, for extracting the symbol of difference EyI.The input of the 4th sign function module 509 is connected with matched filter 23, for receiving the I road range value yR of the actual constellation point received, extracts the symbol of I road range value yR.Two inputs of the second multiplier 510 connect the output of the 3rd sign function module 508 and the output of the 4th sign function module 509 respectively, and the symbol for the difference EyI by extraction is multiplied with the symbol of I road range value yR, obtains the second product.An input of the 3rd adder 511 connects the output of the first multiplier, and another input connects the output of the second multiplier, for by the first product and the second product poor, difference is the phase error of local carrier.

Based on above-mentioned principle, present invention also offers a kind of method that 8QAM extracts carrier phase error, comprise the steps:

Steps A, obtains I road range value yR and the Q road range value yI of the actual constellation point received;

Step B, according to following formulas Extraction local carrier-phase error E (y):

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ -1& 0>yR\&GreaterEqual;-2\\ -3& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ -1& 0>yI\&GreaterEqual;-2\\ -3& -2>yI\end{array}\right\}.$

In sum, the calculating of whole carrier phase error provided by the invention is quite simple, only can realize with several adder and simple hardware logic, be the actualizing technology that a kind of simple and effective carrier track recovers, be applicable to the orthogonal amplitude modulation system on 8 rank.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (4)

1.8QAM extracts the method for local carrier-phase error, and it is characterized in that, described method comprises the steps:

Steps A, obtains I road range value yR and the Q road range value yI of the actual constellation point received;

Step B, according to following formulas Extraction local carrier-phase error E (y):

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ \mathrm{-1}& 0>yR\&GreaterEqual;-2\\ \mathrm{-3}& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ \mathrm{-1}& 0>yI\&GreaterEqual;-2\\ \mathrm{-3}& -2>yI\end{array}\right\}.$

2. a 8QAM receiver, is characterized in that, comprising:

Complex multiplier, for the modulated signal of reception and local carrier signal are carried out complex multiplication, exports baseband I road signal and base band Q road signal;

Decimation filter, is connected with described complex multiplier, for by the processing clock rate reduction of described baseband I road signal and base band Q road signal to 2 times of symbol clock speed;

Matched filter, is connected with described decimation filter, for exporting I road range value yR and the Q road range value yI of the actual constellation point received;

Decoder, is connected with described matched filter, for carrying out decoding process to described I road range value yR and Q road range value yI;

Carrier track restore circuit, be connected between described matched filter and described complex multiplier, for according to following formulas Extraction local carrier-phase error E (y), and according to E (y), the phase error of local carrier is compensated, then export the local carrier after compensating to described complex multiplier:

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ \mathrm{-1}& 0>yR\&GreaterEqual;-2\\ \mathrm{-3}& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ \mathrm{-1}& 0>yI\&GreaterEqual;-2\\ \mathrm{-3}& -2>yI\end{array}\right\}.$

3. 8QAM receiver as claimed in claim 2, it is characterized in that, described carrier track restore circuit comprises:

Carrier phase error extraction module, for according to following formulas Extraction local carrier-phase error E (y):

E(y)＝sign(EyR)·sign(yI)-sign(EyI)·sign(yR)

Wherein, EyR=yR-DyR, EyI=yI-DyI, sign function for getting sign function, for extracting the symbol of numerical value;

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ \mathrm{-1}& 0>yR\&GreaterEqual;-2\\ \mathrm{-3}& -2>yR\end{array}\right\},DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ \mathrm{-1}& 0>yI\&GreaterEqual;-2\\ \mathrm{-3}& -2>yI\end{array}\right\};$

Second-order loop filter, is connected with described carrier phase error extraction module, for carrying out integration to carrier phase error E (y);

Digital controlled oscillator, be connected with described second-order loop filter, for the phase place of the output adjustment local carrier according to second-order loop filter, realize compensating the phase error of local carrier, then export the local carrier after compensation of phase to described complex multiplier.

4. 8QAM receiver as claimed in claim 3, it is characterized in that, described carrier phase error extraction module comprises:

First decision device, its input connects described matched filter, for receiving the I road range value yR of the actual constellation point received, exports the first hard-decision values DyR according to such as under type,

$DyR=\left\{\begin{array}{cc}3& yR\&GreaterEqual;2\\ 1& 2>yR\&GreaterEqual;0\\ \mathrm{-1}& 0>yR\&GreaterEqual;-2\\ \mathrm{-3}& -2>yR\end{array}\right\};$

First adder, an one input connects described matched filter, receives the I road range value yR of the actual constellation point received, and another input connects the output of described first decision device, for by poor for described I road range value yR and described first hard-decision values DyR, obtain difference EyR;

One sign function module, its input is connected with the output of described first adder, for extracting the symbol of difference EyR;

2nd sign function module, its input is connected with the output of described matched filter, for receiving the Q road range value yI of the actual constellation point received, extracts the symbol of Q road range value yI;

First multiplier, two input connects the output of a described sign function module and the output of the 2nd sign function module respectively, and the symbol for the difference EyR by extraction is multiplied with the symbol of Q road range value yI, obtains the first product;

Second decision device, its input connects described matched filter, for receiving the Q road range value yI of the actual constellation point received, exports the second hard-decision values DyI according to such as under type,

$DyI=\left\{\begin{array}{cc}3& yI\&GreaterEqual;2\\ 1& 2>yI\&GreaterEqual;0\\ \mathrm{-1}& 0>yI\&GreaterEqual;-2\\ \mathrm{-3}& -2>yI\end{array}\right\};$

Second adder, an one input connects described matched filter, receives the Q road range value yI of the actual constellation point received, and another input connects the output of described second decision device, for by poor for described Q road range value yI and described second hard-decision values DyI, obtain difference EyI;

3rd sign function module, its input is connected with the output of described second adder, for extracting the symbol of difference EyI;

4th sign function module, its input is connected with described matched filter, for receiving the I road range value yR of the actual constellation point received, extracts the symbol of I road range value yR;

Second multiplier, two input connects the output of described 3rd sign function module and the output of the 4th sign function module respectively, and the symbol for the difference EyI by extraction is multiplied with the symbol of I road range value yR, obtains the second product;

3rd adder, one input connects the output of described first multiplier, and another input connects the output of the second multiplier, for by described first product and the second product poor, difference is the phase error of local carrier.