CN103023841B - A kind of DC offset compensation method and device - Google Patents

Abstract

The open a kind of DC offset compensation method of the present invention and device, the method comprises: signal receiver receives the signal comprising pilot signal that described apparatus for transmitting signal sends; When setting cycle arrives, described signal receiver, according to the pilot signal received in local pilot signal and this cycle, calculates amplitude gain; Described local pilot signal is that described signal receiver generates local pilot signal generation according to the agreement parameter between apparatus for transmitting signal; Described signal receiver, according to described amplitude gain, the average of pilot signal received in this cycle, the average of local pilot signal, calculates DC offset; Or, according to described amplitude gain, the pilot signal received in this cycle, local pilot signal, calculate DC offset; The each signal received in this cycle is subtracted described DC offset by described signal receiver, obtains the signal after DC compensation.

Description

A kind of DC offset compensation method and device

Technical field

The present invention relates to wireless technical field, particularly relate to a kind of DC offset compensation method and device.

Background technology

At super large-scale integration (VeryLargeScaleIntegratedcircuits, VLSI) in, the equipment such as radio-frequency devices and analog device all exists and introduces direct current (DirectCurrent, it is called for short DC) device of composition, it is thus desirable to the output signal of above-mentioned device is carried out DC compensation.

Signal before DC compensation contains direct current composition, is called contaminated signal. Existing DC compensation scheme carries out in the digital domain sampling and sampled result is carried out respective handling, it is achieved to the DC compensation of contaminated signal. At present, a kind of DC compensation scheme being most widely used is: set a cycle estimator, sample in cycle estimator, add up the average of all sampling points of contaminated signal in this cycle estimator, carry out getting whole, the estimated value whole result will be got offset as direct current, in current or next cycle estimator, each sampling point of contaminated signal is subtracted above-mentioned direct current estimated value respectively, thus obtains direct current compensation signal (namely removing the signal of direct current skew), to carry out subsequent disposal.

Existing DC compensation technology is based on such prerequisite, think original signal (not through the signal of direct current skew) owing to disturbing through adding, the process not direct current signal such as modulation, namely average is 0, therefore, within a certain period of time, the average of all sampling points of Received signal strength is DC offset value. The DC offset value calculated affects very big by the primary characteristic of statistical sample number, signal, there is relatively big error, requires higher equipment (such as comprehensive test instrument etc.) for DC compensation, and this kind of method is difficult to reach requirement.

Therefore, need a kind of DC-offset compensation scheme badly and occur, in order to solve the problems of the technologies described above.

Summary of the invention

Embodiments provide a kind of DC offset compensation method and device, in order to improve the precision of DC compensation skew, ensure the accuracy of DC-offset compensation.

The embodiment of the present invention provides a kind of DC offset compensation method, and described method comprises:

Signal receiver receives the signal comprising pilot signal that described apparatus for transmitting signal sends;

When setting cycle arrives, described signal receiver, according to the pilot signal received in local pilot signal and this cycle, calculates amplitude gain; Described local pilot signal is that described signal receiver generates local pilot signal generation according to the agreement parameter between apparatus for transmitting signal;

Described signal receiver, according to described amplitude gain, the average of pilot signal received in this cycle, the average of local pilot signal, calculates DC offset; Or, according to described amplitude gain, the pilot signal received in this cycle, local pilot signal, calculate DC offset;

The each signal received in this cycle is subtracted described DC offset by described signal receiver, obtains the signal after DC compensation.

The embodiment of the present invention also provides a kind of DC-offset compensation device, comprising:

Signal pre-processing module, generates local pilot signal for the agreement parameter between basis and apparatus for transmitting signal;

Amplitude gain calculates module, for when setting cycle arrives, according to the local pilot signal of the pilot signal received in this cycle and described signal processing CMOS macro cell, calculates amplitude gain;

DC offset calculates module, for the average according to described amplitude gain, the average of pilot signal received in this cycle, the local pilot signal of generation, calculates DC offset; Or, according to described amplitude gain, receive pilot signal in this cycle, the local pilot signal of generation, calculate DC offset;

DC offset compensation module, for each signal received in this cycle is subtracted described DC offset, obtains the signal after DC compensation.

Compared with prior art, the above embodiment of the present invention has following Advantageous Effects:

In the DC-offset compensation scheme that the embodiment of the present invention provides, by generating local pilot signal by DC-offset compensation device, when setting cycle arrives, according to the pilot signal received in the local pilot signal generated and this cycle, calculate amplitude gain, and according to the average of the average of the pilot signal received in amplitude gain, this cycle, the local pilot signal of generation, calculate DC offset; Or, local pilot signal according to the pilot signal received in amplitude gain, this cycle, generation, calculate DC offset, and the signal received is subtracted DC offset, obtain the signal after DC compensation, DC offset affects little by statistical sample number and signal primary characteristic, it is to increase the precision of direct current bias estimation value, ensures the accuracy of DC-offset compensation.

Accompanying drawing explanation

The DC-offset compensation schematic flow sheet that Fig. 1 provides for the embodiment of the present invention;

The structural representation of the DC-offset compensation device that Fig. 2 provides for the embodiment of the present invention.

Embodiment

For the problems referred to above that prior art exists, embodiments provide the pilot signal calculating DC offset that a kind of utilization receives, and according to the DC offset calculated, carry out the scheme of DC compensation to the received signal, improve the precision of direct current bias estimation value, ensure the accuracy of DC-offset compensation. Below in conjunction with accompanying drawing, the embodiment of the present invention is described in detail.

The embodiment of the present invention is applied to the radio communication system comprising apparatus for transmitting signal and signal receiver, and signal receiver is provided with DC-offset compensation device, and DC-offset compensation device passes through Implement of Function Module usually. Apparatus for transmitting signal is used for sending signal (comprising pilot signal) to signal receiver; The agreement parameter that DC-offset compensation device is used between basis and apparatus for transmitting signal generates local pilot signal, and utilize local pilot signal and the pilot signal received, calculate DC offset, and carry out DC compensation to the received signal according to calculating DC offset.

In embodiments of the present invention, the territory of setting numeral in advance is as the collection period of signal, such as, numeral territory can be 1 subframe or gap when 1, in embodiments of the present invention, taking 1 subframe (5ms) for digital territory, the frequency of Received signal strength Rx is 1000Hz is example, then the quantity of the sampling point in this numeral territory is 500, that is, can receive 500 signal Rx within 1 second.

The ultimate principle of the Received signal strength DC-offset compensation scheme that the embodiment of the present invention provides is as follows:

The pilot signal that signal receiver receives is R (n), DC-offset compensation device generates local pilot signal T (n) according to the agreement parameter between apparatus for transmitting signal, and local pilot signal T (n) is the pilot signal that apparatus for transmitting signal sends. In signals transmission, the pilot signal R (n) that signal receiver receives is subject to the impact of channel gain a, white Gaussian noise N (n) and direct current offset d c_offset, and the pass between pilot signal R (n), channel gain a, white Gaussian noise N (n) and direct current offset d c_offset is:

R (n)=aT (n)+N (n)+dc_offset(1)

DC-offset compensation device calculates the conjugation of local pilot signal T (n), obtains conjugation signal T (n)^*After, pilot signal R (n) and the T (n) that will receive^*Relevant, and get mathematical expection, obtain formula (2):

E{R(n)��T(n)^*}=E{(a��T(n)+N(n)+dc_offset)��T(n)^*}=a �� E{ | | T (n) | |²}+E{N(n)��T(n)^*}+dc_offset��E{T(n)^*(2)

Due to local pilot signal T (n) be generally through randomization after signal, when the quantity of sample point is enough, E{T (n) } level off to 0, with managing E{T (n)^*Also 0 is leveled off to.

DC offset dc_offset is relative to the energy of local pilot signal | | T (n) | |²Very little, that is,

dc_offset��E{T(n)^*}<<����E{||T(n)||²(3)

In addition, owing to white Gaussian noise N (n) is uncorrelated with local pilot signal T (n), it is possible to obtain formula (4):

E{N(n)��T(n)^*�� 0(4)

In conjunction with formula (2), (3) and (4), it is possible to obtain formula (5):

$a\&ap;\frac{E\{R\left(n\right)\&times;T{\left(n\right)}^{*}\}}{E\left\{{\left|\right|T\left(n\right)\left|\right|}^2\right\}}---\left(5\right)$

According to formula (1) and (5), it is possible to obtain formula (6):

Dc_offset=E{R (n) }-a �� E{T (n) }-E{N (n) } (6)

Owing to noise has the characteristic that average is 0, that is, E{N (n) } �� 0, therefore, it is possible to formula (6) is deformed into formula (7):

Dc_offset �� E{R (n) }-a �� E{T (n) } (7)

In addition, according to formula (2), (4) and (5), it is possible to obtain formula (8):

$\mathrm{dc}\_\mathrm{offset}=\frac{E\{R\left(n\right)\&times;T{\left(n\right)}^{*}\}-a\&times;E\left\{{\left|\right|T\left(n\right)\left|\right|}^2\right\}-E\{N\left(n\right)\&times;T{\left(n\right)}^{*}\}}{E\left\{T{\left(n\right)}^{*}\right\}}---\left(8\right)$

With reason, owing to noise has the characteristic that average is 0, that is, E{N (n) } �� 0, and when sample point is enough, E{T (n)^*Also 0 is leveled off to therefore, it is possible to formula (8) is deformed into formula (9):

$\mathrm{dc}\_\mathrm{offset}=\frac{E\{R\left(n\right)\&times;T{\left(n\right)}^{*}\}-a\&times;E\left\{{\left|\right|T\left(n\right)\left|\right|}^2\right\}}{E\left\{T{\left(n\right)}^{*}\right\}}---\left(9\right)$

Derive by above-mentioned formula it will be seen that local pilot signal T (n) is the generation of the agreement parameter between basis and apparatus for transmitting signal, it is known signal, utilize formula (6) or (8) that direct current skew can be calculated. Utilizing the performance that formula (6) or (8) obtain only to be correlated with white Gaussian noise N (n), when statistical sample number is more many, or white Gaussian noise N (n) is more hour, E{N (n) �� T (n)^*And E{N (n) more level off to 0, therefore, the direct current bias estimation error calculated by formula (6) or (8) is more little, and the result of DC compensation is more accurate.

In actual applications, apparatus for transmitting signal can send with road pilot signal usually, and pilot signal is control signal, for measuring and monitoring and controlling channels information, ensures system synchronization and channel estimating. The embodiment of the present invention make use of the pilot signal in Received signal strength to carry out direct current bias estimation, and carries out DC-offset compensation. Below in conjunction with Fig. 1, DC-offset compensation flow process being described in detail, this flow process comprises the following steps:

Step 101, DC-offset compensation device Received signal strength sends the signal Rx that equipment sends, and signal Rx comprises data signal and pilot signal R_p��

Step 102, when setting cycle arrives, DC-offset compensation device is according to the pilot signal R received in this cycle_pWith local pilot signal T_p, calculate amplitude gain a.

Concrete, DC-offset compensation device generates local pilot signal according to the agreement parameter between apparatus for transmitting signal, generates local pilot signal T_pStep can regard as and carry out DC compensation pre-treatment step, local pilot signal T_pSpecific algorithm be prior art, do not repeat them here.

Within this cycle, the pilot signal R that DC-offset compensation device will receive_pWith local pilot signal T_pConjugation signal T_p ^*It is correlated with and sues for peace, obtain the first constant Corr, that is,Wherein, R_p(n) pilot signal sequence for receiving in this cycle;

T_pN local pilot signal sequence that () generates for DC-offset compensation device in this cycle; T_pN () * is the conjugation signal of the local pilot signal sequence that DC-offset compensation device generates; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal that described signal receiver receives within this cycle.

DC-offset compensation device is by local pilot signal T_pDelivery is asked square again, then result is finally added up, and calculates local pilot signal T_pTotal energy E_tx, that is:

$E\_\mathrm{tx}=\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(T_p\left(n\right)\&times;T_p{\left(n\right)}^{*})=\mathrm{\&Sigma;}{\left|\right|T_p\left(n\right)\left|\right|}^2;$ Wherein, R_p(n) pilot signal sequence for receiving in this cycle; T_pN local pilot signal sequence that () generates for DC-offset compensation device in this cycle; T_pN () * is the conjugation signal of the local pilot signal sequence that DC-offset compensation device generates; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

DC-offset compensation device is by calculating the first constant Corr and local pilot signal T_pThe ratio of total energy E_tx, obtain amplitude gain a, that is,

Step 103, DC-offset compensation device calculates DC offset.

Preferably, DC-offset compensation device can calculate DC offset by following two kinds of modes:

Mode one, according to amplitude gain a, the pilot signal R that receives in this cycle_pAverage, local pilot signal T_pAverage, calculate DC offset dc_offset.

Concrete, DC-offset compensation device calculates the pilot signal R received in this cycle respectively_pWith local pilot signal T_pAverage:

$\mathrm{mean}\_R=\stackrel{\&OverBar;}{R_p};$ $\mathrm{mean}\_T=\stackrel{\&OverBar;}{T_p};$

Therefore, according to aforesaid formula derivation it will be seen that DC offset dc_offset can be obtained by following formula: $\mathrm{dc}\_\mathrm{offset}=\mathrm{mean}\_R-a\&times;\mathrm{mean}\_T=\stackrel{\&OverBar;}{R_p}-a\&times;\stackrel{\&OverBar;}{T_p}.$

This shows, calculating DC offset by mode one, data processing process is simple.

Mode two, according to amplitude gain a, the pilot signal R that receives in this cycle_p, the local pilot signal T of apparatus for transmitting signal_p, calculate DC offset dc_offset.

Concrete, DC-offset compensation device is to local pilot signal T_pConjugation T_p ^*Summation, that is,Wherein, n is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

Therefore, according to aforesaid formula derivation it will be seen that DC offset dc_offset can be obtained by following formula:

$\mathrm{dc}\_\mathrm{offset}=\frac{\mathrm{Corr}-a\&times;E\_\mathrm{tx}}{\mathrm{sum}\_T\_\mathrm{conj}}=\frac{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(R_p\left(n\right)\&times;T_p{\left(n\right)}^{*})-a\&times;\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(T_p\left(n\right)\&times;T_p{\left(n\right)}^{*})}{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{T}_p{\left(n\right)}^{*}};$ Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

This shows, being calculated the DC offset obtained by mode two relative to mode one, more accurately, performance is better.

Step 104, each signal Rx (n) received in this cycle is subtracted DC offset dc_offset by DC-offset compensation device, obtains signal Rx_comp (n) after DC compensation.

In one-period, the DC offset dc_offset of each Received signal strength is identical, after DC-offset compensation device calculates DC offset dc_offset, it is possible to respectively Received signal strength Rx (n) each in this cycle is carried out DC compensation. The signal Rx received is subtracted DC offset dc_offset, obtains signal Rx_comp:Rx_comp (n) after corresponding DC compensation=Rx (n)-dc_offset.

By above-mentioned DC-offset compensation flow process it may be seen that the embodiment of the present invention utilizes the pilot signal received, the DC offset calculated affects little by statistical sample number and signal primary characteristic, and precision is higher, ensure that the accuracy of DC-offset compensation.

Based on identical technical conceive, the embodiment of the present invention additionally provides a kind of DC-offset compensation device, and as shown in Figure 2, this equipment comprises:

Signal pre-processing module 21, generates local pilot signal for the agreement parameter between basis and apparatus for transmitting signal;

Amplitude gain calculates module 22, for when setting cycle arrives, according to the local pilot signal that the pilot signal received in this cycle and described signal pre-processing module 21 generate, calculating amplitude gain;

DC offset calculates module 23, for the average according to described amplitude gain, the average of pilot signal received in this cycle, the local pilot signal of generation, calculates DC offset; Or, according to described amplitude gain, receive pilot signal in this cycle, the local pilot signal of generation, calculate DC offset;

DC offset compensation module 24, for each signal received in this cycle is subtracted described DC offset, obtains the signal after DC compensation.

Amplitude gain calculate module 22 specifically for, by following formulae discovery amplitude gain:

$a=\frac{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(R_p\left(n\right)\&times;T_p{\left(n\right)}^{*})}{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(T_p\left(n\right)\&times;T_p{\left(n\right)}^{*})};$

Wherein, a is amplitude gain; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

DC offset calculate module 23 specifically for, by following formulae discovery DC offset:

$\mathrm{dc}\_\mathrm{offset}=\stackrel{\&OverBar;}{R_p\left(n\right)}-a\&times;\stackrel{\&OverBar;}{T_p\left(n\right)};$

Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

DC offset calculate module 23 specifically for, by following formulae discovery DC offset:

$\mathrm{dc}\_\mathrm{offset}=\frac{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(R_p\left(n\right)\&times;T_p{\left(n\right)}^{*})-a\&times;\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}(T_p\left(n\right)\&times;T_p{\left(n\right)}^{*})}{\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}{T}_p{\left(n\right)}^{*}};$

Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

Through the above description of the embodiments, the technician of this area can be well understood to the present invention and can realize by the mode that software adds required general hardware platform, naturally it is also possible to by hardware, but in a lot of situation, the former is better enforcement mode. Based on such understanding, the technical scheme of the present invention in essence or says that part prior art contributed can embody with the form of software product, this computer software product is stored in a storage media, comprise some instructions with so that a station terminal equipment (can be mobile phone, Personal Computer, server, or the network equipment etc.) perform the method described in each embodiment of the present invention.

The above is only the preferred embodiment of the present invention; it is noted that for those skilled in the art, under the premise without departing from the principles of the invention; can also making some improvements and modifications, these improvements and modifications also should look protection scope of the present invention.

Claims (6)

1. a DC offset compensation method, it is characterised in that, described method comprises:

Signal receiver receives the signal comprising pilot signal that described apparatus for transmitting signal sends;

When setting cycle arrives, described signal receiver, according to the pilot signal received in local pilot signal and this cycle, calculates amplitude gain; Described local pilot signal is that described signal receiver generates local pilot signal generation according to the agreement parameter between apparatus for transmitting signal;

Described signal receiver, according to described amplitude gain, the average of pilot signal received in this cycle, the average of local pilot signal, calculates DC offset; Or, according to described amplitude gain, the pilot signal received in this cycle, local pilot signal, calculate DC offset;

The each signal received in this cycle is subtracted described DC offset by described signal receiver, obtains the signal after DC compensation;

Wherein, described amplitude gain is obtained by following formula:

Wherein, a is amplitude gain; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is the local pilot signal sequence of signal in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

2. the method for claim 1, it is characterised in that, described signal receiver, according to the average of described amplitude gain, the average of pilot signal received in this cycle, the local pilot signal of generation, calculates DC offset, is specially:

Described signal receiver is by following formulae discovery DC offset: $dc\_offset=\stackrel{\&OverBar;}{R_p\left(n\right)}-a\&times;\stackrel{\&OverBar;}{T_p\left(n\right)};$

Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

3. the method for claim 1, it is characterised in that, the described local pilot signal according to described amplitude gain, the pilot signal received in this cycle, generation, calculates DC offset, is specially:

Described signal receiver is by following formulae discovery DC offset:

$dc\_offset=\frac{\underset{n=1}{\overset{N}{\&Sigma;}}(R_p\left(n\right)\&times;T_p{\left(n\right)}^{*})-a\&times;\underset{n=1}{\overset{N}{\&Sigma;}}(T_p\left(n\right)\&times;T_p{\left(n\right)}^{*})}{\underset{n=1}{\overset{N}{\&Sigma;}}{T}_p{\left(n\right)}^{*}};$

Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

4. a DC-offset compensation device, it is characterised in that, comprising:

Signal pre-processing module, generates local pilot signal for the agreement parameter between basis and apparatus for transmitting signal;

Amplitude gain calculates module, for when setting cycle arrives, according to the local pilot signal that the pilot signal received in this cycle and described signal pre-processing module generate, calculating amplitude gain;

DC offset calculates module, for the average according to described amplitude gain, the average of pilot signal received in this cycle, the local pilot signal of generation, calculates DC offset; Or, according to described amplitude gain, receive pilot signal in this cycle, the local pilot signal of generation, calculate DC offset;

DC offset compensation module, for each signal received in this cycle is subtracted described DC offset, obtains the signal after DC compensation;

Wherein, described amplitude gain calculate module specifically for, by following formulae discovery amplitude gain:

$a=\frac{\underset{n=1}{\overset{N}{\&Sigma;}}(R_p\left(n\right)\&times;T_p\left(n\right)*)}{\underset{n=1}{\overset{N}{\&Sigma;}}(T_p\left(n\right)\&times;T_p\left(n\right)*)};$

Wherein, a is amplitude gain; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

5. DC-offset compensation device as claimed in claim 4, it is characterised in that, described DC offset calculate module specifically for, by following formulae discovery DC offset:

$dc\_offset=\stackrel{\&OverBar;}{R_p\left(n\right)}-a\&times;\stackrel{\&OverBar;}{T_p\left(n\right)};$

Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.

6. DC-offset compensation device as claimed in claim 4, it is characterised in that, described DC offset calculate module specifically for, by following formulae discovery DC offset:

$dc\_offset=\frac{\underset{n=1}{\overset{N}{\&Sigma;}}(R_p\left(n\right)\&times;T_p{\left(n\right)}^{*})-a\&times;\underset{n=1}{\overset{N}{\&Sigma;}}(T_p\left(n\right)\&times;T_p{\left(n\right)}^{*})}{\underset{n=1}{\overset{N}{\&Sigma;}}{T}_p{\left(n\right)}^{*}};$

Wherein, dc_offset is DC offset; R_p(n) pilot signal sequence for receiving in this cycle; T_pN () is pilot signal sequence local in this cycle; T_pN () * is the conjugation signal of local pilot signal sequence; N is sampling point index, and 1��n��N, N is the sampling point quantity of the signal received in this cycle.