CN103391269A - 8 QAM (quadrature amplitude modulation) receiver and method for extracting local carrier phase error by 8QAM receiver - Google Patents

Abstract

The invention belongs to the technical field of terrestrial digital receiving of satellite communication, satellite remote sensing and satellite broadcast, and provides an 8QAM receiver and a method for extracting a local carrier phase error by the 8QAM receiver. The method comprises the steps as follows: step A, an I-way amplitude value yR and a Q-way amplitude value yI of an actually received constellation point are obtained; and step B, a local carrier phase error E(y) is extracted according to the following formula: E(y):E(y)=sign(EyR)*sign(yI)-sign(EyI)*sign(yR), wherein EyR=yR-DyR, EyI=yI-DyI, and a sign function is a symbol extraction function and used for extracting symbols of numerical values. Compared with the prior art, the computation of the whole carrier phase error is pretty simple, and only requires a few of summators and simple hardware logic.

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, relate in particular to a kind of method of 8QAM receiver and extraction local carrier phase error thereof.

Background technology

in the satellite digital communication system, in order to transmit the more signal of high data rate in limited bandwidth chahnel, must fully weigh the probability of spectrum efficiency and symbol error, the probability of symbol error is used Eb/N0(Energy per transmitted bit versus the Noise spectral density usually, the bit signal to noise ratio) stipulate, in satellite communication system, modulation system commonly used has PSK(Phase-Shift Keying, phase shift keying), QAM(Quadrature Amplitude Modulation, quadrature amplitude modulation), APSK(Amplitude Phase-Shift Keying, APK amplitude phase shift keying), wherein, the PSK modulation technique has again BPSK(Binary Phase-Shift Keying, two-phase PSK), QPSK(Quadrature Phase-Shift Keying, Quadrature Phase Shift Keying), OQPSK(Offset-QPSK, offset quadraphase shift keying), dividing 8PSK(eight phase phase shift keyings), the QAM modulation technique has again 8QAM(eight rank quadrature amplitude modulation), dividing 16QAM(16 rank quadrature amplitude modulation), the APSK modulation technique has again 16APSK(16 rank APK amplitude phase shift keyings), dividing 32APSK(30 second order APK amplitude phase shift keyings).

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

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

8QAM is separated timing need to be compensated the local carrier phase error, to realize the tracking of local carrier to the modulation signal carrier wave that receives, but present carrier track realize that circuit is comparatively complicated, be unfavorable for the miniaturization of product, also be 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 realize with simple hardware logic the calculating of carrier phase error.

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, obtain I road range value yR and the Q road range value yI of the actual constellation point that receives;

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, are used for extracting the symbol of numerical value;

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

The present invention also provides a kind of 8QAM receiver, it is characterized in that, comprising: complex multiplier, and the modulated signal and the local carrier signal that are used for receiving are carried out complex multiplication, output baseband I road signal and base band Q road signal;

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

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

Decoder, be connected with described matched filter, is used for described I road range value yR and Q road range value yI are carried out the decoding processing;

The carrier track restore circuit, be connected between described matched filter and described complex multiplier, be used 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, the local carrier after then output compensates is described complex multiplier extremely:

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

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

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

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

Description of drawings

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

Fig. 2 A and Fig. 2 B are respectively 8QAM constellation point mapping relations and 8PSK constellation point mapping relations schematic diagram;

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 purpose of the present invention, technical scheme and advantage clearer, 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, is 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, only shows 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, and 8QAM transmitter 1 is used for carrying out data encoding, is then gone out by antenna transmission after modulation.After 8QAM receiver 2 receives modulation signal, process and obtain baseband I road signal and base band Q road signal, then decoding.Above-mentioned modulation demodulation system is applicable to the 8QAM technology, and the constellation point mapping relations of 8QAM as shown in Figure 2 A, can find out that the constellation point mapping relations are different from the 8PSK technology shown in Fig. 2 B.

Fig. 3 shows the structural principle of above-mentioned 8QAM transmitter 1, and for generation of forward error correction, for example extremely strong other forward error corrections of LDPC(of error correcting capability are applicable equally with encoder 11), export bit sequence (b after encoder 11 codings _3i, b _3i+1, b _3i+2), wherein, i=0,1,2,3 ..., 3 one group is to be the modulation system of 8QAM because of what adopt later, in the processing through 8QAM constellation point mapping block 12, and the quadrature amplitude value after the output mapping; After carrying out power amplification by 13 modulation of 8QAM modulator and high power amplifier 14 finally, 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.Modulated signal and local carrier signal that complex multiplier 21 is used for receiving are carried out complex multiplication, output baseband I road signal and base band Q road signal, decimation filter 22 is with processing clock rate reduction to the 2 times symbol clock speed of baseband I road signal and base band Q road signal.Then matched filter 23 is exported I road range value yR and the Q road range value yI of the actual constellation point that receive, then carries out decoding by 24 couples of I road range value yR of decoder and Q road range value yI and process.

Carrier track restore circuit 25 is connected between matched filter 23 and complex multiplier 21, be used for extracting local carrier phase error E (y), and according to E (y), the phase error of local carrier is compensated, then the local carrier after the output compensation is 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, are used for extracting the symbol of numerical value;

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

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 used 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, are used for extracting the symbol of numerical value;

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

Second-order loop filter 252 is connected with the carrier phase error extraction module, is used for carrier phase error E (y) is carried out integration, is equivalent to the effect of a low pass filter.Digital controlled oscillator 253 is connected with second-order loop filter 252 again, be used for adjusting according to the output of second-order loop filter 252 phase place of the local carrier of its output, realization compensates the phase error of local carrier, then exports 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, the first multiplier 505, the second decision device 506, second adder 507, the 3rd sign function module 508, the 4th sign function module 509, the 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, the I road range value yR for receiving the actual constellation point that receives, export the first hard decision value DyR according to following mode, $\mathrm{DyR}=\left\{\begin{array}{cc}3& \mathrm{yR}\≥2\\ 1& 2>\mathrm{yR}\≥0\\ -1& 0>\mathrm{yR}\≥-2\\ -3& -2>\mathrm{yR}\end{array}\right\},$ Its operation principle is relevant to the position of the constellation point shown in Fig. 2 A.An input matching connection filter of first adder 502, receive the I road range value yR of the actual constellation point that receives, another input connects the output of the first decision device, and it is poor with I road range value yR and the first hard decision value DyR to be used for, and obtains difference EyR.The input of the one sign function module 503 is connected with the output of first adder 502, is used 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, is used for receiving the Q road range value yI of the actual constellation point that receives, and extracts the symbol of Q road range value yI.Two inputs of the first multiplier 505 connect respectively the output of a sign function module 503 and the output of the 2nd sign function module 504, are used for the symbol of the difference EyR that will extract and the symbol of Q road range value yI and multiply each other, and obtain the first product.The input matching connection filter 23 of the second decision device 506, the Q road range value yI for receiving the actual constellation point that receives, export the second hard decision value DyI according to following mode, $\mathrm{DyI}=\left\{\begin{array}{cc}3& \mathrm{yI}\≥2\\ 1& 2>\mathrm{yI}\≥0\\ -1& 0>\mathrm{yI}\≥-2\\ -3& -2>\mathrm{yI}\end{array}\right\}.$ 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 that receives, another input connects the output of the second decision device 506, and it is poor with Q road range value yI and the second hard decision value DyI to be used for, and obtains difference EyI.The input of the 3rd sign function module 508 is connected with the output of second adder 507, is used for extracting the symbol of difference EyI.The input of the 4th sign function module 509 is connected with matched filter 23, is used for receiving the I road range value yR of the actual constellation point that receives, and extracts the symbol of I road range value yR.Two inputs of the second multiplier 510 connect respectively the output of the 3rd sign function module 508 and the output of the 4th sign function module 509, are used for the symbol of the difference EyI that will extract and the symbol of I road range value yR and multiply each other, and obtain 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, and it is poor with the first product and the second product to be used for, and difference is the phase error of local carrier.

Based on above-mentioned principle, the present invention also provides a kind of 8QAM to extract the method for carrier phase error, comprises the steps:

Steps A, obtain I road range value yR and the Q road range value yI of the actual constellation point that receives;

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, are used for extracting the symbol of numerical value;

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

In sum, the calculating of whole carrier phase error provided by the invention is quite simple, only with several adders and simple hardware logic, can realize, for a kind of technology that realizes of simple and effective carrier track recovery, 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 modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.

Claims (4)

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

Steps A, obtain I road range value yR and the Q road range value yI of the actual constellation point that receives;

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, are used for extracting the symbol of numerical value;

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

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

Complex multiplier, the modulated signal and the local carrier signal that are used for receiving are carried out complex multiplication, output baseband I road signal and base band Q road signal;

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

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

Decoder, be connected with described matched filter, is used for described I road range value yR and Q road range value yI are carried out the decoding processing;

The carrier track restore circuit, be connected between described matched filter and described complex multiplier, be used 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, the local carrier after then output compensates is described complex multiplier extremely:

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

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

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

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

The carrier phase error extraction module is used 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, are used for extracting the symbol of numerical value;

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

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

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

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

The first decision device, its input connects described matched filter, is used for receiving the I road range value yR of the actual constellation point that receives, and according to following mode, exports the first hard decision value DyR, $\mathrm{DyR}=\left\{\begin{array}{cc}3& \mathrm{yR}\≥2\\ 1& 2>\mathrm{yR}\≥0\\ -1& 0>\mathrm{yR}\≥-2\\ -3& -2>\mathrm{yR}\end{array}\right\};$

First adder, an one input connects described matched filter, receives the I road range value yR of the actual constellation point that receives, and another input connects the output of described the first decision device, it is poor with described I road range value yR and described the first hard decision value DyR to be used for, and obtains difference EyR;

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

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

The first multiplier, two input connect respectively the output of a described sign function module and the output of the 2nd sign function module, are used for the symbol of the difference EyR that will extract and the symbol of Q road range value yI and multiply each other, and obtain the first product;

The second decision device, its input connects described matched filter, is used for receiving the Q road range value yI of the actual constellation point that receives, and according to following mode, exports the second hard decision value DyI, $\mathrm{DyI}=\left\{\begin{array}{cc}3& \mathrm{yI}\≥2\\ 1& 2>\mathrm{yI}\≥0\\ -1& 0>\mathrm{yI}\≥-2\\ -3& -2>\mathrm{yI}\end{array}\right\};$

Second adder, an one input connects described matched filter, receives the Q road range value yI of the actual constellation point that receives, and another input connects the output of described the second decision device, it is poor with described Q road range value yI and described the second hard decision value DyI to be used for, and obtains difference EyI;

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

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

The second multiplier, two input connect respectively the output of described the 3rd sign function module and the output of the 4th sign function module, are used for the symbol of the difference EyI that will extract and the symbol of I road range value yR and multiply each other, and obtain the second product;

The 3rd adder, an one input connects the output of described the first multiplier, and another input connects the output of the second multiplier, and it is poor with described the first product and the second product to be used for, and difference is the phase error of local carrier.

Images