A frequency offset estimation error correction method for UWB

Abstract

The application provides a frequency offset estimation error correction method for UWB, which comprises the following steps: a receiver performs correlation operation on a preamble and a local template, sets an energy window, extracts a plurality of data in a first window as a first valid interval signal, and slides the window at intervals of a symbol period T_sym to extract a plurality of data in a second window as a second valid interval signal; conjugate multiplication is performed on sampling points at the same index positions of the first and second valid interval signals respectively, and the conjugate multiplication results in all intervals are accumulated to obtain an initial phase difference estimation value; according to a linear segmented CFO estimation and a correction error model, in combination with historical phase difference estimation data, a phase correction factor is introduced to correct the initial phase difference estimation value to obtain a corrected phase difference estimation value; the corrected phase difference estimation value is used to calculate a phase difference radian value by using an atan2 function; and the phase difference radian value is used as a phase rotation step to perform phase compensation on subsequent data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultra-wideband, and particularly to a frequency offset estimation error correction method for UWB. BACKGROUND

[0002] Ultra-Wideband (UWB) technology is widely used in digital key, indoor precise positioning and Internet of Things field due to its high precision, high resolution and low power consumption. However, in the UWB transceiver system, there is inevitably a frequency deviation, which will cause signal phase rotation, cause inter-symbol interference, reduce communication sensitivity, and also cause ranging error to increase. Frequency deviation is a key factor affecting UWB device communication and ranging. In order to correct CFO (Carrier Frequency Offset), the receiver needs to estimate CFO and correct the received signal accordingly.

[0003] Therefore, it is necessary to provide a frequency offset estimation error correction method for UWB to effectively solve the above problems. SUMMARY

[0004] The present application provides a frequency offset estimation error correction method for UWB to solve the problems and deficiencies in the prior art. A phase correction factor is introduced to correct the phase difference estimation value, effectively compensating for the systematic error caused by linear segmentation in hardware implementation.

[0005] The present application provides a frequency offset estimation error correction method for UWB, which comprises the following steps:

[0006] Step S101: The receiver performs correlation operation on the preamble and the local template, determines a synchronization point by peak energy detection, determines that the synchronization point is fixed and unchanged, sets an energy window with the synchronization point as the center, extracts a plurality of data in the first window as the first effective interval signal, slides the window with a symbol period T_sym as the interval to extract a plurality of data in the second window as the second effective interval signal, slides the window with a symbol period T_sym as the interval to extract a plurality of data in the third window as the third effective interval signal, and so on until the last preamble symbol extracts a plurality of data in the Mth window as the Mth effective interval signal.

[0007] Step S102: The same index position sampling points of the first effective interval signal and the second effective interval signal are respectively conjugate multiplied, and the conjugate multiplication results in all intervals are accumulated to obtain an initial phase difference estimation value.

[0008] Step S103: According to the linear segmented CFO estimation and the error model of correction, combining the historical phase difference estimation data, a phase correction factor is introduced to modify the initial phase difference estimation value, and a modified phase difference estimation value is obtained;

[0009] Step S104: Using the modified phase difference estimation value, the phase difference radian value is calculated using the atan2 function;

[0010] Step S105: Using the phase difference radian value as the phase rotation step, the subsequent data is phase compensated;

[0011] Step S106: Return to step S102 to continue the second process, and then loop M times to end.

[0012] Preferably, the size of the energy window is 3, all the window data is extracted, and the symbol period T_sym is 0.1us.

[0013] Preferably, the initial phase difference estimation value represents the average phase rotation amount in each symbol period T_sym.

[0014] Preferably, the modified phase difference estimation value is calculated by the following formula:

[0015]

[0016] wherein, the modified phase difference estimation value is denoted as the initial phase difference estimation value is denoted as the CFO correction factor is denoted as

[0017] Preferably, the calculation formula of the CFO correction factor is:

[0018]

[0019] wherein, β is a coefficient, and the coefficient is pre-stored in the register of the receiver.

[0020] Preferably, the value of β is 0.5.

[0021] Preferably, the phase difference radian value is calculated using the following formula:

[0022]

[0023] wherein, the phase difference radian value is denoted as

[0024] Preferably, a symbol period There are N sampling points, for the kth symbol segment, for the ith sampling point (i=0,1,…,N-1) therein, the phase compensation value applied is:

[0025]

[0026] The compensation is usually realized by complex multiplication: where y[k, n] is the original received signal.

[0027] Preferably, the symbol period T_sym is 0.1 us, and the N is 1024.

[0028] Preferably, the second time is to multiply the sampling points at the same index positions of the second and third effective interval signals by conjugate, the third time is to multiply the sampling points at the same index positions of the third and fourth effective interval signals by conjugate, and so on.

[0029] Compared with the prior art, the technical scheme of the embodiment of the application has the following beneficial effects:

[0030] The method for frequency offset estimation error correction for UWB provided by the embodiment of the application comprises the following steps: S101, a receiver performs correlation operation on a preamble and a local template, determines a synchronization point by peak energy detection, sets an energy window with the synchronization point as the center, extracts a plurality of data in a first window as a first effective interval signal, slides the window by a symbol period T_sym to extract a plurality of data in a second window as a second effective interval signal, slides the window by a symbol period T_sym to extract a plurality of data in a third window as a third effective interval signal, and so on until a plurality of data in an Mth window in the last preamble symbol are extracted as an Mth effective interval signal; S102, conjugate multiplication is performed on sampling points at the same index positions of the first effective interval signal and the second effective interval signal respectively, the conjugate multiplication results in all intervals are accumulated, and an initial phase difference estimation value is obtained; S103, according to a linear segmented CFO estimation and a correction error model, in combination with historical phase difference estimation data, a phase correction factor is introduced to correct the initial phase difference estimation value, and a corrected phase difference estimation value is obtained; S104, the corrected phase difference estimation value is used to calculate a phase difference radian value by using an atan2 function; S105, the phase difference radian value is used as a phase rotation step to perform phase compensation on subsequent data; and S106, the step S102 is returned to continue the second process, and then the process is repeated M times to end, wherein a phase correction factor is introduced to correct the phase difference estimation value, and systematic errors caused by linear segmentation in hardware implementation are effectively compensated.

[0031] Further, the residual frequency offset after CFO compensation is significantly reduced, and the communication demodulation sensitivity and the ranging accuracy are improved

[0032] ​Further, the calculation overhead is small by using the complex multiplication operation only once, and the hardware burden is not increased;

[0033] Further, the method can be seamlessly integrated into the existing UWB receiver architecture, without changing the core CFO estimation and compensation module structure, and is easy for FPGA or ASIC hardware implementation. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are only some of the embodiments of the present application, not all the embodiments. For those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0035] Figure 1 A flowchart of a frequency offset estimation error correction method for UWB according to a preferred embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0037] The technical solutions of the present application will be described in detail in the following specific embodiments. The following several specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in some embodiments.

[0038] The present application provides a frequency offset estimation error correction method for UWB, which introduces a phase correction factor to correct the phase difference estimation value, effectively compensating for the systematic error caused by linear segmentation in hardware implementation.

[0039] Figure 1 A flowchart of a frequency offset estimation error correction method for UWB according to a preferred embodiment of the present application. Figure 1 The present application provides a frequency offset estimation error correction method for UWB, which includes:

[0040] Step S101: The receiver performs correlation operation on the preamble and the local template, determines a synchronization point by peak energy detection, fixes the synchronization point after determination, sets an energy window with the synchronization point as the center, extracts multiple data in a first window as a first valid interval signal, slides the window by symbol period T_sym to extract multiple data in a second window as a second valid interval signal, slides the window by symbol period T_sym to extract multiple data in a third window as a third valid interval signal, and so on until the last preamble symbol is extracted to extract multiple data in an Mth window as an Mth valid interval signal;

[0041] Step S102: The conjugate multiplication is performed on the same index position sampling points of the first valid interval signal and the second valid interval signal respectively, the conjugate multiplication results in all intervals are accumulated to obtain an initial phase difference estimation value;

[0042] Step S103: According to the linear segmented CFO estimation and the correction error model, the initial phase difference estimation value is modified by introducing a phase correction factor combined with historical phase difference estimation data to obtain a modified phase difference estimation value;

[0043] Step S104: The modified phase difference estimation value is used to calculate a phase difference radian value by using an atan2 function;

[0044] Step S105: The phase difference radian value is used as a phase rotation step to perform phase compensation on subsequent data;

[0045] Step S106: Return to step S102 to continue the second flow, and then loop M times to end.

[0046] Specifically, the correction error model is derived as follows:

[0047] Suppose that adjacent symbol data are Si and Si+1

[0048]

[0049] Wherein, n is a sample quantization time, is a signal amplitude value of symbol i at sample n, N is a preamble symbol sample number, is an ADC sampled CFO, is a sampling phase offset, and is a CFO estimation value of samples Si and Si+1. The product of the conjugate of symbol Si+1 and Si obtains the phase difference of the two symbols , the fixed phase offset is removed ,

[0050]

[0051] The estimation error introduced by the linear segment CFO estimation in the above model which needs to be eliminated before the next phase difference calculation.

[0052] In a specific implementation, the size of the energy window is 3, all the data within the window is extracted, and the symbol period T_sym is 0.1 us.

[0053] In a specific implementation, the initial phase difference estimation value represents the average phase rotation amount within each symbol period T_sym.

[0054] In a specific implementation, the modified phase difference estimation value is calculated by the following formula:

[0055]

[0056] wherein, represents the modified phase difference estimation value, represents the initial phase difference estimation value, represents the CFO correction factor.

[0057] In a specific implementation, the calculation formula of the CFO correction factor is:

[0058]

[0059] wherein β is a coefficient, and the coefficient is pre-stored in a register of the receiver.

[0060] In a specific implementation, the value of β is 0.5.

[0061] In a specific implementation, the phase difference radian value is calculated by the following formula:

[0062]

[0063] wherein, represents the phase difference radian value.

[0064] In a specific implementation, one symbol period There are N sampling points, for the kth symbol segment, for the nth sampling point (i=0, 1, …, N-1) therein, the phase compensation value applied is:

[0065]

[0066] The compensation is usually realized by complex multiplication: wherein y[k, n] is the original received signal.

[0067] In a specific implementation, the symbol period is 0.1us, and N is 1024.

[0068] In a specific implementation, the second time is to multiply the conjugate of the sampling points at the same index positions of the second and third valid interval signals, the third time is to multiply the conjugate of the sampling points at the same index positions of the third and fourth valid interval signals, and so on.

[0069] To sum up, the method for frequency offset estimation error correction for UWB provided by the embodiment of the application comprises the following steps: S101, a receiver performs correlation operation on a preamble and a local template, determines a synchronization point by using peak energy detection, sets an energy window with the synchronization point as the center, extracts a plurality of data in a first window as a first valid interval signal, slides the window by a symbol period T_sym to extract a plurality of data in a second window as a second valid interval signal, slides the window by a symbol period T_sym to extract a plurality of data in a third window as a third valid interval signal, and so on until a plurality of data in an Mth window are extracted as an Mth valid interval signal; S102, the conjugate of the sampling points at the same index positions of the first valid interval signal and the second valid interval signal is multiplied, the results of the conjugate multiplication in all intervals are accumulated, and an initial phase difference estimation value is obtained; S103, according to a linear segmented CFO estimation and error correction model, in combination with historical phase difference estimation data, a phase correction factor is introduced to correct the initial phase difference estimation value, and a corrected phase difference estimation value is obtained; S104, the corrected phase difference estimation value is used to calculate a phase difference radian value by using an atan2 function; S105, the phase difference radian value is used as a phase rotation step to perform phase compensation on subsequent data; and S106, the step S102 is returned to continue the second process, and then the process is repeated M times to end, wherein the phase correction factor is introduced to correct the phase difference estimation value, and the systematic error caused by linear segmentation in hardware implementation is effectively compensated.

[0070] Further, the residual frequency offset after CFO compensation is significantly reduced, and the communication demodulation sensitivity and the ranging accuracy are improved

[0071] Further, only one complex multiplication operation is used, the calculation overhead is small, and the hardware burden is not increased.

[0072] Further, the method can be seamlessly integrated into an existing UWB receiver architecture, without changing the core CFO estimation and compensation module structure, and is easy to implement in FPGA or ASIC hardware.

[0073] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for correcting frequency offset estimation errors in UWB, characterized in that, The method includes: Step S101: The receiver performs correlation operations on the preamble and the local template, uses peak energy detection to determine a synchronization point, and the synchronization point remains fixed after determination. An energy window is set with the synchronization point as the center. Multiple data in the first window are extracted as the first effective interval signal. The window is slid with the symbol period T_sym as the interval to extract multiple data in the second window as the second effective interval signal. The window is slid with the symbol period T_sym as the interval to extract multiple data in the third window as the third effective interval signal, and so on until the last preamble symbol, multiple data in the Mth window are extracted as the Mth effective interval signal. Step S102: Perform conjugate multiplication on the sampling points at the same index positions of the first effective interval signal and the second effective interval signal respectively, and accumulate the conjugate multiplication results in all intervals to obtain the initial phase difference estimate; Step S103: Based on the linear piecewise CFO estimation and correction error model, and combined with historical phase difference estimation data, a phase correction factor is introduced to correct the initial phase difference estimate, and the corrected phase difference estimate is obtained. Step S104: Using the corrected phase difference estimate, calculate the phase difference in radians using the atan2 function; Step S105: Use the phase difference in radians as the phase rotation step to perform phase compensation on subsequent data; Step S106: Return to step S102 to continue the second process, and then repeat the process M times to end; The corrected phase difference estimate is calculated using the following formula: in, This represents the corrected phase difference estimate. This represents the initial phase difference estimate; The formula for calculating the CFO correction factor is: in, The coefficients are pre-stored in the receiver's register.

2. The frequency offset estimation error correction method for UWB as described in claim 1, characterized in that, The energy window size is 3, and all data within the window is extracted. The symbol period T_sym is 0.1us.

3. The frequency offset estimation error correction method for UWB as described in claim 1, characterized in that, The initial phase difference estimate represents the average phase rotation within each symbol period T_sym.

4. The frequency offset estimation error correction method for UWB as described in claim 1, characterized in that, The value is 0.

5.

5. The frequency offset estimation error correction method for UWB as described in claim 1, characterized in that, The phase difference in radians is calculated using the following formula: in, This represents the phase difference in radians.

6. The frequency offset estimation error correction method for UWB as described in claim 1, characterized in that, The second step involves multiplying the sampled points at the same index positions of the signals in the second and third valid intervals by their conjugates. The third step involves multiplying the sampled points at the same index positions of the signals in the third and fourth valid intervals by their conjugates, and so on.

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