A carrier phase tracking device and signal receiver for QAM weak signal

Abstract

The present invention provides a carrier phase tracking device for a QAM weak signal, comprising: a compensation module for initially estimating and compensating the signal frequency of the QAM signal; a first processing module, which is connected in communication with the compensation module and is used to perform fourth-power processing on the peripheral signal points in the constellation diagram of the QAM signal; a Kalman tracking loop, which is connected in communication with the processing module and is used to perform coherent accumulation of phase errors of continuous data blocks and use Kalman loop tracking; a second processing module, which is connected in communication with the Kalman tracking loop and is used to compensate the QAM signal, and then perform phase discrimination, coherent accumulation and use Kalman tracking loop tracking on the peripheral signal points in the constellation diagram of the QAM signal to obtain a second signal parameter estimation value of the QAM signal. The present invention also provides a signal receiver. The present invention can achieve higher-precision tracking of the carrier phase, and solves the technical problem of the conventional tracking loop being unstable and prone to losing lock under high dynamic and low signal-to-noise ratio conditions in the prior art.

Description

Technical Field

[0001] The invention relates to the field of QAM signal receiving equipment development, and in particular to a carrier phase tracking device for a QAM weak signal and a signal receiver. Background Art

[0002] Quadrature Amplitude Modulation (QAM) is an orthogonal modulation technology that jointly controls amplitude and phase. It uses amplitude and phase to transmit information at the same time, so it can achieve higher bandwidth utilization under the same minimum distance condition. It is widely used in microwave communication, satellite communication, deep space communication and other fields. The corresponding communication system may operate in a high dynamic and low signal-to-noise ratio environment.

[0003] The traditional QAM signal carrier tracking loop adopts a high dynamic tracking environment, which will introduce a large frequency deviation and frequency change rate, which will cause the phase of the constellation point to change rapidly in a short time. On the other hand, the frequency detection and phase detection loops are usually used in the early stage of tracking. When the adjacent symbol phase rotation is detected to be too large, the phase detection result is directly set to zero. It has both frequency detection and phase detection capabilities. After the signal frequency tracking is stable, a phase-locked loop or only a phase detection loop is used for fine tracking. When frequency detection and phase detection are performed, if all constellation points are processed, the tolerable phase error is limited (high-order QAM signal phase tracking accuracy is required to be higher). If the constellation points outside the QAM signal are processed, since the peripheral constellation points are less affected by the phase error, the frequency detection and phase detection usually perform polarity judgment and then take the constellation points outside the constellation diagram, but the probability of the corresponding tracking available symbols is reduced. The higher the order of the QAM signal, the lower the probability of the constellation points outside the constellation diagram. The signal-to-noise ratio of the phase detection information input to the traditional tracking loop is reduced, and a large loop bandwidth is required in a high dynamic environment. Therefore, the traditional tracking loop under high dynamic and low signal-to-noise ratio is unstable and easy to lose lock. Summary of the invention

[0004] In view of the defect of the traditional QAM signal carrier phase tracking loop introduced in the background technology that the tracking is unstable and easy to lose lock in a high dynamic and low signal-to-noise ratio environment, the present invention proposes a carrier phase tracking device for QAM weak signals, which can achieve higher-precision tracking of the carrier phase, and solves the technical problem of the traditional tracking loop being unstable and easy to lose lock in high dynamic and low signal-to-noise ratio conditions in the prior art.

[0005] The technical solution of the present invention is as follows:

[0006] A carrier phase tracking device for a QAM weak signal, the carrier phase tracking device comprising:

[0007] The compensation module is used to compensate the QAM signal according to the fourth power spectrum of the QAM signal. The signal frequency is initially estimated and compensated, and the QAM signal is output ;

[0008] The first processing module is connected to the compensation module for processing the QAM signal within the loop update period T. The outer signal points in the constellation diagram are processed to the fourth power and the unsigned modulated QAM signal is output. ;

[0009] The Kalman tracking loop is connected to the processing module for QAM signal The phase errors of consecutive data blocks in the QAM signal are coherently accumulated and tracked using the Kalman tracking loop to obtain the QAM signal. An estimate of a first signal parameter of ;

[0010] The second processing module is connected to the Kalman tracking loop for processing the QAM signal according to the first signal parameter estimation value. Compensate and output QAM signal , then the QAM signal The peripheral signal points in the constellation diagram are phase-detected, coherently accumulated, and tracked using the Kalman tracking loop to obtain the QAM signal. The second signal parameter estimate.

[0011] Furthermore, the compensation module comprises:

[0012] The first preset unit is used to preset the QAM signal The signal sampling rate is , the sampling interval is , the QAM signal is a QAM baseband signal;

[0013] The FFT unit is connected to the first preset unit for converting the QAM signal After the fourth power and phase information Multiply, sum the products and divide by the data length used for frequency estimation to get the QAM signal The fast Fourier transform result of , whose expression is: ,in, is the data length used for signal frequency estimation, is the phase information, N is the number of data points used for signal frequency estimation, variable i is the signal sampling point number, and variable k is the signal spectrum line number;

[0014] The search unit communicates with the FFT unit and is used to find the absolute value of the fast Fourier transform result. The signal spectrum line number corresponding to the maximum value of , whose expression is: ;

[0015] The first judgment unit is connected to the search unit for determining the signal spectrum line number. When the number of data points N used for signal frequency estimation is less than half, the signal frequency estimate is the signal spectrum line number Divide by the data length The quotient of the multiple value is then divided by the signal sampling rate The product of the multiplication between the two is the signal spectrum line number If the signal frequency estimate is greater than or equal to half the number of data points N used in the signal frequency estimate, the signal frequency estimate is the signal spectrum line number With data length The difference between The quotient obtained by division is then divided by the signal sampling rate The product of multiplication between them, QAM signal The signal frequency estimate The expression is: ,in, For QAM signal The signal sampling rate is The data length used for signal frequency estimation, is the signal spectrum line number;

[0016] The first compensation unit is connected to the first judgment unit for converting the QAM signal With phase information Multiply them to get the frequency compensated QAM signal , whose expression is: ;in, is the estimated value of signal frequency, is the signal sampling rate, and variable i is the signal sampling point number.

[0017] Furthermore, the first processing module includes:

[0018] Setting unit, used to obtain QAM signal The average amplitude of the outermost constellation point and the adjacent constellation point of the constellation diagram is used as the QAM signal amplitude decision threshold ;

[0019] The second judgment unit is connected to the setting unit for judging the QAM signal after signal compensation. Is the absolute value of greater than or equal to the QAM signal amplitude decision threshold? , the QAM signal after signal compensation The absolute value of is greater than or equal to the QAM signal amplitude decision threshold In the case of The outer signal points in the constellation diagram are processed to the fourth power to obtain the unsigned modulated QAM signal .

[0020] In the initial stage of tracking, the present invention selects the outermost constellation point of the constellation diagram of the QAM signal through the setting unit in the first processing module, and then performs quartic processing through the second judgment unit, which can effectively eliminate the symbol influence, thereby accumulating data for a longer period of time and effectively improving the accuracy of signal frequency and carrier phase estimation.

[0021] Furthermore, the Kalman tracking loop includes:

[0022] The first residual phase error estimation unit is used to perform coherent accumulation and fast Fourier transform processing on continuous data blocks, and then estimate the residual phase error to obtain a residual phase error estimation value ;

[0023] A Kalman tracking unit is connected in communication with the residual phase error estimation unit, and is used to , for QAM signals Perform preliminary tracking of the signal residual frequency change rate, residual frequency and residual phase error to obtain the first residual frequency estimate and the first phase error estimate .

[0024] Furthermore, the second processing module includes:

[0025] The second compensation unit is used to convert the QAM signal With phase information Multiply them to get the QAM compensated signal , whose expression is: ,in, is the first residual frequency estimate, is the first phase error estimation value, N is the number of signal sampling points;

[0026] A phase detector is connected to the second compensation unit for compensating the QAM compensated signal. The outer signal points of the constellation diagram are subjected to polarity judgment phase detection processing to obtain the phase detection sequence dis(i);

[0027] The second residual phase error estimation unit is connected to the phase detector for dividing the phase detection sequence dis(i) by the number of data sampling points N to obtain the QAM compensated signal The residual phase error estimate of the signal ;

[0028] and for estimating the residual phase error according to the , using the Kalman tracking loop, the QAM signal The residual frequency change rate, residual frequency and residual phase error are accurately tracked to obtain the second residual frequency estimate , the second residual phase error estimate .

[0029] Furthermore, the phase detector comprises:

[0030] Phase detector unit, used for QAM signal The absolute value of is greater than or equal to the QAM signal amplitude decision threshold In this case, the QAM signal Divide by the QAM signal Take the imaginary part of the nearest theoretical constellation signal point in the constellation diagram to get the phase detection sequence , the QAM signal amplitude decision threshold It is the average amplitude of the outermost constellation point and the adjacent constellation points.

[0031] Further, the first residual phase error estimation unit includes:

[0032] The coherent accumulation subunit is used to convert the QAM signal The continuous data block is divided into M segments, each segment is L point data, and then the L point data in each segment is coherently accumulated to obtain the accumulated QAM signal , its expression is: , where the variable is the data segment number, and its value range is [0,M], where M is the number of data segments in a continuous data block. is the data point number, L is the number of data points in each data segment;

[0033] The FFT subunit is connected to the coherent accumulation subunit for coherently accumulating the QAM signal. Perform fast Fourier transform processing to obtain the QAM signal after fast Fourier transform processing , whose expression is: , where the variable is the data segment number, is the number of data segments, variable is the data point number;

[0034] The first calculation subunit is connected to the FFT subunit for calculating the QAM signal after the fast Fourier transform. The data point number corresponding to the maximum value of the absolute value of and numbered by the number of data points Calculate the QAM signal after coherent accumulation The residual phase error estimate ; Wherein, the data point number The expression is: , the residual phase error estimate The expression is: .

[0035] The present invention performs long-term coherent accumulation on the QAM signal through the coherent accumulation subunit in the first residual phase error estimation unit to form a QAM signal of a certain length, thereby greatly improving the input signal-to-noise ratio of the tracking loop.

[0036] Further, the Kalman tracking unit comprises:

[0037] A first processing unit, configured to calculate a priori covariance matrix of a signal residual error vector of a signal to be tracked according to the predicted signal residual error vector and update the priori covariance matrix;

[0038] A second processing unit is connected to the first processing unit for estimating a residual phase error estimate value of a next tracking cycle and correcting a signal frequency and phase deviation;

[0039] The frequency and phase acquisition unit is connected to the second processing unit for continuously tracking for multiple cycles and obtaining a frequency estimation value and a phase error estimation value after convergence. The signal to be tracked is a QAM signal. or QAM signal .

[0040] The present invention tracks the QAM signal through a Kalman tracking loop, which can achieve fast and robust tracking convergence of the QAM signal, while improving the estimation accuracy of the frequency estimation value and the phase error estimation value.

[0041] Furthermore, the first processing unit includes:

[0042] The preset subunit is used to preset the signal residual error vector of the signal to be tracked at the start time of the k-1 tracking cycle as , The expression is: ,in, is the estimated value of the residual frequency change rate at the start of the k-1th tracking cycle, is the residual frequency estimate at the start of the k-1th tracking cycle, is the residual phase estimate at the start of the k-1th tracking cycle;

[0043] The first estimation subunit is connected to the preset subunit for presetting the signal residual error vector of the signal to be tracked. After multiplying by the state transfer matrix of the signal residual error vector, the signal residual error vector at the start time of the kth tracking cycle is estimated. , obtain the residual frequency estimate at the start of the kth tracking cycle and the residual phase error estimate , The expression is: ,in, is the state transfer matrix of the signal residual error vector of the signal to be tracked, and its expression is: ;

[0044] The first processing subunit is connected to the first estimation subunit in communication, and is used to add the product of the state transfer matrix of the signal residual error vector, the covariance matrix of the signal residual error vector at the start time of the k-1th tracking, and the transposed matrix of the state transfer matrix of the residual error vector to the process covariance matrix, and the result is the prior covariance matrix of the signal residual error vector at the start time of the kth tracking. , whose expression is: ,in, is the covariance matrix of the signal residual error vector at the start time of the k-1th tracking, Q is the process covariance matrix, and its expression is: ,in, is the RF frequency of the signal, is the speed of light, is the phase of the receiver crystal, is the frequency noise power spectral density, is the acceleration noise from the signal, is the loop tracking period;

[0045] The second processing subunit is connected to the first processing subunit for converting the prior covariance matrix of the signal residual error vector Sequentially with the measurement matrix , Kalman gain The product after multiplication, and then calculate the product prior covariance matrix The difference between them gives the updated covariance matrix , whose expression is: ,in, is the measurement variance of the residual phase error estimate, is the prior covariance matrix of the signal residual error vector, is the measurement matrix, is the measurement matrix, and its expression is: , is the Kalman gain, and its expression is: .

[0046] Furthermore, the second processing unit includes:

[0047] The third estimation subunit is used to estimate the residual carrier phase of the signal to be tracked in the kth tracking cycle to obtain a residual phase error estimate Or the residual phase error estimate , the signal to be tracked is a QAM signal or QAM signal ;

[0048] The third processing subunit is connected to the third estimation subunit for calculating the measurement matrix The predicted value of the residual error vector The product is then calculated with the residual phase error estimate The difference between After multiplication, the predicted value of the residual error vector of the signal The result of adding is the signal residual error vector estimated by Kalman tracking at the start of the kth tracking. , whose expression is ,in, is the measurement matrix, is the Kalman gain, and its expression is: ,in, is the measurement variance of the residual phase error estimate, is the prior covariance matrix of the signal residual error vector;

[0049] The fourth processing subunit is connected to the third processing subunit in communication, and is used to estimate the residual frequency at the start time of the kth tracking period according to the residual frequency estimation value. and the residual phase error estimate , the signal to be tracked and the phase information Multiply them together to obtain a modified QAM signal, the QAM signal is expressed as: ,in, is the signal to be tracked before correction, is the number of signal sampling points, is the sampling interval, the variable is the signal sampling point number, variable It is the loop tracking cycle number.

[0050] A signal receiver comprises the above-mentioned carrier phase tracking device.

[0051] Beneficial effects of the present invention:

[0052] 1. The present invention eliminates the influence of symbols by performing quartic processing on the peripheral constellation points of the QAM signal in the initial stage of tracking, thereby accumulating data for a long time to estimate the signal frequency and carrier phase with high estimation accuracy, thus solving the problem that the traditional frequency and phase detection and phase-locked loop can only use a single symbol for frequency and phase estimation in the initial stage of tracking, resulting in poor estimation accuracy.

[0053] 2. The present invention takes peripheral constellation points for residual phase estimation during the tracking process, improves the estimation accuracy through long-term integration, and adopts a Kalman filter tracking loop after estimation to achieve high-precision and robust tracking of high-dynamic and low-SNR QAM signals. This solves the problem that the traditional polarity decision phase-locked loop uses peripheral constellation points for phase estimation and a single symbol for estimation, but is difficult to take into account both high-dynamic and low-SNR environments due to the low probability of peripheral constellation points and poor estimation accuracy in high-order BOC conditions, as well as the technical problem of instability in tracking in a high-dynamic and low-SNR environment.

[0054] 4. The present invention accumulates a certain length of signal in the initial stage of tracking, thereby greatly improving the loop input signal-to-noise ratio, and greatly improving the phase and frequency tracking accuracy and stability; then, after the frequency and phase tracking of the QAM signal are locked by the Kalman tracking loop, the phase detection is performed using the peripheral constellation points, and the phase detection error is accumulated for a certain length to improve the signal-to-noise ratio, thereby achieving fast and robust tracking convergence of high-dynamic and low-signal-to-noise ratio QAM weak signals, and at the same time solves the technical problem that the traditional frequency detection and phase-locked loop requires a narrow phase-locked loop bandwidth in the initial stage of tracking, but the high-dynamic scenario requires a wide phase-locked loop bandwidth, resulting in unstable tracking in a high-dynamic and low-signal-to-noise ratio environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0056] Figure 1 A schematic diagram of a carrier phase tracking device for a QAM weak signal according to an embodiment of the present invention;

[0057] Figure 2 A specific schematic diagram of a carrier phase tracking device for a QAM weak signal according to an embodiment of the present invention;

[0058] Figure 3 A schematic diagram of a Kalman tracking loop according to an embodiment of the present invention;

[0059] Figure 4 Schematic diagram of carrier phase tracking convergence of QAM weak signal in high dynamic and low signal-to-noise ratio scenarios;

[0060] Figure 5 This is the constellation diagram after the QAM weak signal carrier phase tracking converges. DETAILED DESCRIPTION

[0061] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0062] As attached Figure 1 As shown, a carrier phase tracking device for a QAM weak signal, the carrier phase tracking device comprising:

[0063] The compensation module is used to compensate the QAM signal according to the fourth power spectrum of the QAM signal. The signal frequency is initially estimated and compensated, and the QAM signal is output ;

[0064] The first processing module is connected to the compensation module for processing the QAM signal within the loop update period T. The outer signal points in the constellation diagram are processed to the fourth power and the unsigned modulated QAM signal is output. ;

[0065] The Kalman tracking loop is connected to the processing module for QAM signal The phase errors of consecutive data blocks in the QAM signal are coherently accumulated and tracked using the Kalman tracking loop to obtain the QAM signal. An estimate of a first signal parameter of ;

[0066] The second processing module is connected to the Kalman tracking loop for processing the QAM signal according to the first signal parameter estimation value. Compensate and output QAM signal , then the QAM signal The peripheral signal points in the constellation diagram are phase-detected, coherently accumulated, and tracked using the Kalman tracking loop to obtain the QAM signal. The second signal parameter estimate.

[0067] As attached Figure 2 As shown, preferably, the compensation module includes:

[0068] The first preset unit is used to preset the QAM signal The signal sampling rate is , the sampling interval is , the QAM signal is a QAM baseband signal;

[0069] The FFT unit is connected to the first preset unit for converting the QAM signal After the fourth power and phase information Multiply, sum the products and divide by the data length used for frequency estimation to get the QAM signal The fast Fourier transform result of , whose expression is: ,in, is the data length used for signal frequency estimation, is the phase information, N is the number of data points used for signal frequency estimation, variable i is the signal sampling point number, and variable k is the signal spectrum line number;

[0070] The search unit communicates with the FFT unit and is used to find the absolute value of the fast Fourier transform result. The signal spectrum line number corresponding to the maximum value of , whose expression is: ;

[0071] The first judgment unit is connected to the search unit for determining the signal spectrum line number. When the number of data points N used for signal frequency estimation is less than half, the signal frequency estimate is the signal spectrum line number Divide by the data length The quotient of the multiple value is then divided by the signal sampling rate The product of the multiplication between the two is the signal spectrum line number If the signal frequency estimate is greater than or equal to half the number of data points N used in the signal frequency estimate, the signal frequency estimate is the signal spectrum line number With data length The difference between The quotient obtained by division is then divided by the signal sampling rate The product of multiplication between them, QAM signal The signal frequency estimate The expression is: ,in, For QAM signal The signal sampling rate is The data length used for signal frequency estimation, is the signal spectrum line number;

[0072] The first compensation unit is connected to the first judgment unit for converting the QAM signal With phase information Multiply them to get the frequency compensated QAM signal , whose expression is: ;in, is the estimated value of signal frequency, is the signal sampling rate, and variable i is the signal sampling point number.

[0073] Preferably, the first processing module comprises:

[0074] Setting unit, used to obtain QAM signal The average amplitude of the outermost constellation point and the adjacent constellation point of the constellation diagram is used as the QAM signal amplitude decision threshold ;

[0075] The second judgment unit is connected to the setting unit for judging the QAM signal after signal compensation. Is the absolute value of greater than or equal to the QAM signal amplitude decision threshold? , the QAM signal after signal compensation The absolute value of is greater than or equal to the QAM signal amplitude decision threshold In the case of The outer signal points in the constellation diagram are processed to the fourth power to obtain the unsigned modulated QAM signal .

[0076] As attached Figure 3 As shown, preferably, the Kalman tracking loop includes:

[0077] The first residual phase error estimation unit is used to perform coherent accumulation and fast Fourier transform processing on continuous data blocks, and then estimate the residual phase error to obtain a residual phase error estimation value ;

[0078] A Kalman tracking unit is connected in communication with the residual phase error estimation unit, and is used to , for QAM signals Perform preliminary tracking of the signal residual frequency change rate, residual frequency and residual phase error to obtain the first residual frequency estimate and the first phase error estimate .

[0079] Preferably, the second processing module comprises:

[0080] The second compensation unit is used to convert the QAM signal With phase information Multiply them to get the QAM compensated signal , whose expression is: ,in, is the first residual frequency estimate, is the first phase error estimation value, N is the number of signal sampling points;

[0081] A phase detector is connected to the second compensation unit for compensating the QAM compensated signal. The outer signal points of the constellation diagram are subjected to polarity judgment phase detection processing to obtain the phase detection sequence dis(i);

[0082] The second residual phase error estimation unit is connected to the phase detector for dividing the phase detection sequence dis(i) by the number of data sampling points N to obtain the QAM compensated signal The residual phase error estimate of the signal ;

[0083] and for estimating the residual phase error according to the , for QAM signals The residual frequency change rate, residual frequency and residual phase error are accurately tracked to obtain the second residual frequency estimate , the second residual phase error estimate .

[0084] Preferably, the phase detector comprises:

[0085] Phase detector unit, used for QAM signal The absolute value of is greater than or equal to the QAM signal amplitude decision threshold In this case, the QAM signal Divide by the QAM signal Take the imaginary part of the nearest theoretical constellation signal point in the constellation diagram to get the phase detection sequence , the QAM signal amplitude decision threshold It is the average amplitude of the outermost constellation point and the adjacent constellation points.

[0086] Preferably, the first residual phase error estimation unit comprises:

[0087] The coherent accumulation subunit is used to convert the QAM signal The continuous data block is divided into M segments, each segment is L point data, and then the L point data in each segment is coherently accumulated to obtain the accumulated QAM signal , its expression is: , where the variable is the data segment number, and its value range is [0,M], where M is the number of data segments in a continuous data block. is the data point number, L is the number of data points in each data segment;

[0088] The FFT subunit is connected to the coherent accumulation subunit for coherently accumulating the QAM signal. Perform fast Fourier transform processing to obtain the QAM signal after fast Fourier transform processing , whose expression is: , where the variable is the data segment number, is the number of data segments, variable is the data point number;

[0089] The first calculation subunit is connected to the FFT subunit for calculating the QAM signal after the fast Fourier transform. The data point number corresponding to the maximum value of the absolute value of and numbered by the number of data points Calculate the QAM signal after coherent accumulation The residual phase error estimate ; Wherein, the data point number The expression is: , the residual phase error estimate The expression is: .

[0090] Preferably, the Kalman tracking unit comprises:

[0091] A first processing unit, configured to calculate a priori covariance matrix of a signal residual error vector of a signal to be tracked according to the predicted signal residual error vector and update the priori covariance matrix;

[0092] A second processing unit is connected to the first processing unit for estimating a residual phase error estimate value of a next tracking cycle and correcting a signal frequency and phase deviation;

[0093] The frequency and phase acquisition unit is connected to the second processing unit for continuously tracking for multiple cycles and obtaining a frequency estimation value and a phase error estimation value after convergence. The signal to be tracked is a QAM signal. or QAM signal .

[0094] Preferably, the first processing unit comprises:

[0095] The preset subunit is used to preset the signal residual error vector of the signal to be tracked at the start time of the k-1 tracking cycle as , The expression is: ,in, is the estimated value of the residual frequency change rate at the start of the k-1th tracking cycle, is the residual frequency estimate at the start of the k-1th tracking cycle, is the residual phase estimate at the start of the k-1th tracking cycle;

[0096] The first estimation subunit is connected to the preset subunit for presetting the signal residual error vector of the signal to be tracked. After multiplying by the state transfer matrix of the signal residual error vector, the signal residual error vector at the start time of the kth tracking cycle is estimated. , obtain the residual frequency estimate at the start of the kth tracking cycle and the residual phase error estimate , The expression is: ,in, is the state transfer matrix of the signal residual error vector of the signal to be tracked, and its expression is: ;

[0097] The first processing subunit is connected to the first estimation subunit in communication, and is used to add the product of the state transfer matrix of the signal residual error vector, the covariance matrix of the signal residual error vector at the start time of the k-1th tracking, and the transposed matrix of the state transfer matrix of the residual error vector to the process covariance matrix, and the result is the prior covariance matrix of the signal residual error vector at the start time of the kth tracking. , whose expression is: ,in, is the covariance matrix of the signal residual error vector at the start time of the k-1th tracking, Q is the process covariance matrix, and its expression is: ,in, is the RF frequency of the signal, is the speed of light, is the phase of the receiver crystal, is the frequency noise power spectral density, is the acceleration noise from the signal, is the loop tracking period;

[0098] The second processing subunit is connected to the first processing subunit for converting the prior covariance matrix of the signal residual error vector Sequentially with the measurement matrix , Kalman gain The product after multiplication, and then calculate the product prior covariance matrix The difference between them gives the updated covariance matrix , whose expression is: ,in, is the measurement variance of the residual phase error estimate, is the prior covariance matrix of the signal residual error vector, is the measurement matrix, is the measurement matrix, and its expression is: , is the Kalman gain, and its expression is: .

[0099] Preferably, the second processing unit comprises:

[0100] The third estimation subunit is used to estimate the residual carrier phase of the signal to be tracked in the kth tracking cycle to obtain a residual phase error estimate Or the residual phase error estimate , the signal to be tracked is a QAM signal or QAM signal ;

[0101] The third processing subunit is connected to the third estimation subunit for calculating the measurement matrix The predicted value of the residual error vector The product is then calculated with the residual phase error estimate The difference between After multiplication, the predicted value of the signal residual error vector The result of adding is the signal residual error vector estimated by Kalman tracking at the start of the kth tracking. , whose expression is ,in, is the measurement matrix, is the Kalman gain, and its expression is: ,in, is the measurement variance of the residual phase error estimate, is the prior covariance matrix of the signal residual error vector;

[0102] The fourth processing subunit is connected to the third processing subunit in communication with the third processing subunit, and is used to estimate the residual frequency at the start time of the kth tracking cycle. and the residual phase error estimate , the signal to be tracked and the phase information Multiply them together to obtain a modified QAM signal, the QAM signal is expressed as: ,in, is the signal to be tracked before correction, is the number of signal sampling points, is the sampling interval, the variable is the signal sampling point number, variable It is the loop tracking cycle number.

[0103] The carrier phase tracking device according to the embodiment of the present invention performs carrier phase tracking on a QAM weak signal, and after simulation, as shown in the attached figure Figure 4As shown in the figure, with the change of time, the carrier phase error changes rapidly within about 100ms and approaches 0 infinitely. It can be seen that the convergence speed of carrier tracking is fast and the tracking accuracy is high. Figure 5 The constellation diagram shown can track QAM weak signals in a high dynamic and low signal-to-noise ratio environment, such as when the signal-to-noise ratio EbN0 is equal to 13dB, through the carrier phase tracking device described in the embodiment of the present invention.

[0104] The embodiment of the present invention uses a compensation module to initially estimate and compensate the signal frequency of the QAM signal, then uses a first processing module to perform fourth power processing on the peripheral signal points in the constellation diagram of the QAM signal, and uses a Kalman tracking loop to coherently accumulate and track the phase errors of continuous data blocks in the QAM signal, and finally uses a second processing module to compensate the QAM signal and perform phase discrimination, coherent accumulation, and Kalman loop tracking on the peripheral signal points in the constellation diagram of the QAM signal, thereby achieving fast and robust tracking convergence of QAM weak signals under high dynamic and low signal-to-noise ratio, and achieving high-precision residual frequency and residual phase errors of QAM weak signals. The estimation not only solves the problem that the traditional frequency detection and phase lock loop can only use a single symbol for frequency and phase estimation in the initial stage of tracking, with poor estimation accuracy and requiring a narrow phase lock loop bandwidth, but the high dynamic scene requires a wide phase lock loop bandwidth, and the technical problem of unstable tracking in a high dynamic and low signal-to-noise ratio environment, but also solves the problem that the traditional polarity decision phase lock loop also takes the outer points of the constellation for phase estimation, but usually uses a single symbol for estimation. Due to the low probability of the outer constellation points, especially in the case of high-order BOC, its estimation accuracy is poor, and it is also difficult to take into account both high dynamic and low signal-to-noise ratio environments at the same time, and the technical problem of unstable tracking in a high dynamic and low signal-to-noise ratio environment.

[0105] An embodiment of the present invention further provides a signal receiver, comprising the above-mentioned carrier phase tracking device; the signal receiver and the carrier phase tracking device are based on the same technical concept and have the same technical effect, which will not be repeated here.

Claims

1. A carrier phase tracking device for a QAM weak signal, characterized in that: The carrier phase tracking device comprises: A compensation module, used for initially estimating and compensating the signal frequency of the QAM signal r0(i) according to the fourth power spectrum of the QAM signal, and outputting the QAM signal r(i); A first processing module is communicatively connected to the compensation module, and is used to perform a fourth power processing on the peripheral signal points in the constellation diagram of the QAM signal r(i) within a loop update period T, and output an unsigned modulated QAM signal r4(i); A Kalman tracking loop, in communication with the first processing module, for coherently accumulating phase errors of consecutive data blocks in the QAM signal r4(i) and tracking them using the Kalman tracking loop to obtain a first signal parameter estimation value of the QAM signal r4(i); The second processing module is communicatively connected to the Kalman tracking loop, and is used to compensate the QAM signal r(i) according to the first signal parameter estimation value, output the QAM signal r′(i), and then perform phase detection, coherent accumulation and Kalman tracking loop tracking on the peripheral signal points in the constellation diagram of the QAM signal r′(i) to obtain the second signal parameter estimation value of the QAM signal r′(i).

2. A carrier phase tracking device for a QAM weak signal as claimed in claim 1, characterized in that: The compensation module comprises: The first preset unit is used to preset the signal sampling rate of the QAM signal r0(i) to be f s , the sampling interval is T s , the QAM signal r0(i) is a QAM baseband signal; The FFT unit is connected to the first preset unit for performing the fourth power calculation on the QAM signal r0(i) and the phase information Multiply, sum the products and divide by the data length used for frequency estimation to obtain the fast Fourier transform result R(k) of the QAM signal r0(i), which is expressed as: Among them, N0 is the data length used for signal frequency estimation, is the phase information, N is the number of data points used for signal frequency estimation, variable i is the signal sampling point number, and variable k is the signal spectrum line number; A search unit is connected to the FFT unit for searching the signal spectrum line number k corresponding to the maximum absolute value |R(k)| of the fast Fourier transform result. max , whose expression is: The first judgment unit is connected to the search unit for determining the signal spectrum line number k. max When the number of data points N used for signal frequency estimation is less than half, the signal frequency estimate is the signal spectrum line number k max Divide the quotient by the multiple value of the data length N0 and then add it to the signal sampling rate f s The product of the multiplication between the two, in the signal spectrum line number k max If the signal frequency estimate is greater than or equal to half the number of data points N used in the signal frequency estimate, the signal frequency estimate is the signal spectrum line number k max The difference between the data length N0 and the four times data length N0 is divided by the quotient obtained by dividing the signal sampling rate f s The product of the multiplication between them, the signal frequency estimate of the QAM signal r(i) The expression is: Among them, f s is the signal sampling rate of the QAM signal r0(i), N0 is the data length used for signal frequency estimation, k max is the signal spectrum line number; The first compensation unit is connected to the first judgment unit for compensating the QAM signal r0(i) with the phase information Multiply them to get the frequency compensated QAM signal r(i), which is expressed as: in, is the signal frequency estimate, f s is the signal sampling rate, and variable i is the signal sampling point number.

3. A carrier phase tracking device for a QAM weak signal as claimed in claim 1 or 2, characterized in that: The first processing module includes: A setting unit is used to take the average amplitude of the outermost constellation point and the adjacent constellation point of the constellation diagram of the QAM signal r(i) as the QAM signal amplitude decision threshold η; The second judgment unit is communicatively connected with the setting unit, and is used for judging whether the absolute value of the QAM signal r(i) after signal compensation is greater than or equal to the QAM signal amplitude judgment threshold η. When the absolute value of the QAM signal r(i) after signal compensation is greater than or equal to the QAM signal amplitude judgment threshold η, the peripheral signal points in the constellation diagram of the QAM signal r(i) after signal compensation are selected for fourth-power processing to obtain an unsigned modulated QAM signal r4(i).

4. A carrier phase tracking device for a QAM weak signal as claimed in claim 3, characterized in that: The Kalman tracking loop consists of: The first residual phase error estimation unit is used to perform coherent accumulation and fast Fourier transform processing on continuous data blocks, and then estimate the residual phase error to obtain a residual phase error estimation value A Kalman tracking unit is connected in communication with the residual phase error estimation unit, and is used to Perform preliminary tracking of the signal residual frequency change rate, residual frequency and residual phase error of the QAM signal r4(i) to obtain the first residual frequency estimate and the first phase error estimate 5. A carrier phase tracking device for a QAM weak signal as claimed in claim 4, characterized in that: The second processing module includes: The second compensation unit is used to convert the QAM signal r(i) into phase information Multiply them to get the QAM compensated signal r′(i), which is expressed as: in, is the first residual frequency estimate, is the first phase error estimation value, N is the number of signal sampling points; A phase detector, which is in communication connection with the second compensation unit, is used to perform polarity decision phase detection processing on the peripheral signal points of the constellation diagram of the QAM compensated signal r′(i) to obtain a phase detection sequence dis(i); The second residual phase error estimation unit is connected to the phase detector and is used to divide the phase detection sequence dis(i) by the number of data sampling points N to obtain the residual phase error estimation value of the QAM compensated signal r′(i) and for estimating the residual phase error according to the The Kalman tracking loop is used to accurately track the residual frequency change rate, residual frequency and residual phase error of the QAM signal r′(i) to obtain the second residual frequency estimate. The second residual phase error estimate The phase detector includes a phase detection unit, which is used to divide the QAM signal r′(i) by the theoretical constellation signal point closest to the QAM signal r′(i) in the constellation diagram and take its imaginary part to obtain a phase detection sequence dis(i) when the absolute value of the QAM signal r′(i) is greater than or equal to the QAM signal amplitude decision threshold η. The QAM signal amplitude decision threshold η is the amplitude average of the outermost constellation point and the adjacent constellation point.

6. A carrier phase tracking device for a QAM weak signal as claimed in claim 4, characterized in that: The first residual phase error estimation unit comprises: The coherent accumulation subunit is used to divide the continuous data blocks in the QAM signal r4(i) into M segments, each segment is L point data, and then coherently accumulate the L point data in each segment to obtain the accumulated QAM signal r 4c (j), its expression is: Among them, variable j is the data segment number, and its value range is [0, M], M is the number of data segments in a continuous data block, variable k is the data point number, and L is the number of data points in each data segment; The FFT subunit is connected to the coherent accumulation subunit for coherently accumulating the QAM signal r 4c (j) Perform fast Fourier transform processing to obtain the QAM signal R after fast Fourier transform processing 4c (k), its expression is: Among them, variable j is the data segment number, M is the number of data segments, and variable k is the number of data points; The first calculation subunit is connected to the FFT subunit for calculating the QAM signal R after the fast Fourier transform. 4c The data point number corresponding to the maximum value of the absolute value of (k) And the data point number is Calculate the QAM signal r after coherent accumulation 4c (j) The residual phase error estimate Among them, the data point number The expression is: The residual phase error estimate The expression is:

7. A carrier phase tracking device for a QAM weak signal as described in claim 4 or 5, characterized in that: The Kalman tracking unit comprises: A first processing unit, configured to calculate a priori covariance matrix of a signal residual error vector of a signal to be tracked according to the predicted signal residual error vector and update the priori covariance matrix; A second processing unit is connected to the first processing unit for estimating a residual phase error estimate value of a next tracking cycle and correcting a signal frequency and phase deviation; The frequency and phase acquisition unit is in communication with the second processing unit and is used to obtain a frequency estimation value and a phase error estimation value after continuous tracking for multiple cycles and convergence. The signal to be tracked is a QAM signal r4(i) or a QAM signal r′(i).

8. A carrier phase tracking device for a QAM weak signal as claimed in claim 7, characterized in that: The first processing unit comprises: The preset subunit is used to preset the signal residual error vector of the signal to be tracked at the start time of the k-1 tracking cycle as X k-1 , X k-1 The expression is: in, is the estimated value of the residual frequency change rate at the start of the k-1th tracking cycle, is the residual frequency estimate at the start of the k-1th tracking cycle, is the residual phase estimate at the start of the k-1th tracking cycle; The first estimation subunit is connected to the preset subunit for presetting the signal residual error vector X of the signal to be tracked. k-1 After multiplying by the state transfer matrix of the signal residual error vector, the signal residual error vector at the start time of the kth tracking cycle is estimated. Get the residual frequency estimate at the start of the kth tracking cycle and the residual phase error estimate The expression is: Among them, Φ is the state transfer matrix of the signal residual error vector of the signal to be tracked, and its expression is: The first processing subunit is connected to the first estimation subunit in communication, and is used to add the product of the state transfer matrix of the signal residual error vector, the covariance matrix of the signal residual error vector at the start time of the k-1th tracking, and the transposed matrix of the state transfer matrix of the residual error vector to the process covariance matrix, and the result is the prior covariance matrix of the signal residual error vector at the start time of the kth tracking. Its expression is: Among them, P k-1 is the covariance matrix of the signal residual error vector at the start time of the k-1th tracking, Q is the process covariance matrix, and its expression is: Among them, f rf is the RF frequency of the signal, v c is the speed of light, q b is the phase of the receiver crystal, q d is the frequency noise power spectral density, q a is the acceleration noise from the signal, T is the loop tracking period; The second processing subunit is connected to the first processing subunit for converting the prior covariance matrix of the signal residual error vector Sequentially with the measurement matrix H k , Kalman gain G k The product after multiplication, and then calculate the product prior covariance matrix The difference between them is used to obtain the updated covariance matrix P k , whose expression is: in, is the measurement variance of the residual phase error estimate, is the prior covariance matrix of the signal residual error vector, H k is the measurement matrix, H k is the measurement matrix, and its expression is: k =[1,0,0], G k is the Kalman gain, and its expression is:

9. A carrier phase tracking device for a QAM weak signal as claimed in claim 8, characterized in that: The second processing unit comprises: The third estimation subunit is used to estimate the residual carrier phase of the signal to be tracked in the kth tracking cycle to obtain a residual phase error estimate Or the residual phase error estimate The signal to be tracked is a QAM signal r4(kN+i) or a QAM signal r′(kN+i); The third processing subunit is connected to the third estimation subunit for calculating the measurement matrix H k The predicted value of the residual error vector The product is then calculated with the residual phase error estimate The difference between k After multiplication, the predicted value of the residual error vector of the signal The result of adding is the signal residual error vector X estimated by Kalman tracking at the start of the kth tracking. k , whose expression is Among them, H k is the measurement matrix, G k is the Kalman gain, and its expression is: in, is the measurement variance of the residual phase error estimate, is the prior covariance matrix of the signal residual error vector; The fourth processing subunit is connected to the third processing subunit in communication with the third processing subunit, and is used to estimate the residual frequency at the start time of the kth tracking cycle. and the residual phase error estimate The signal to be tracked and the phase information Multiply them together to obtain a modified QAM signal, the QAM signal is expressed as: Among them, r(kN+i) is the signal to be tracked before correction, N is the number of signal sampling points, T s is the sampling interval, variable i is the signal sampling point number, and variable k is the loop tracking cycle number.

10. A signal receiver, characterized in that: The invention comprises a carrier phase tracking device as described in any one of claims 1 to 9.

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