CN102098258A - Method for removing narrow-band interference and self-adapting filter - Google Patents

Method for removing narrow-band interference and self-adapting filter Download PDF

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CN102098258A
CN102098258A CN2009102254497A CN200910225449A CN102098258A CN 102098258 A CN102098258 A CN 102098258A CN 2009102254497 A CN2009102254497 A CN 2009102254497A CN 200910225449 A CN200910225449 A CN 200910225449A CN 102098258 A CN102098258 A CN 102098258A
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sampling instant
weights
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CN102098258B (en
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王守义
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ZTE Corp
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    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
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    • H03H21/0012—Digital adaptive filters

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Abstract

The embodiment of the invention relates to the signal processing field, in particular to a method for removing narrow-band interference and a self-adapting filter, aiming to solve the problems of processing time delay and poor real-time for removal of interference by a fixity coefficient filter in the prior art. The method provided by the embodiment of the invention comprises the steps that: the self-adapting filter can determine a weight corresponding to the current sampling time, a cancellation signal corresponding to the current sampling time according to the determined weight and a reference signal sampled at the current sampling time, wherein the reference signal is generated based on a centre frequency of the narrow-band interference; then the self-adapting filter filters a band signal sampled at the current sampling time according to the determined cancellation signal corresponding to the current sampling time, and finally the band signal with narrow-band interference being removed is obtained. The embodiment of the invention can reduce the processing time delay, improve the real time, and perfect an interference cancellation effect.

Description

A kind of method and sef-adapting filter of removing narrow band interference
Technical field
The present invention relates to the signal processing field, particularly a kind of method and sef-adapting filter of removing narrow band interference.
Background technology
(Orthogonal Frequency Division Multiplexing, OFDM) technology is a kind of multi-carrier digital modulation technique to OFDM, also is a kind of channeling technology.Compare other modulation techniques and multiplex technique, the OFDM technology has spectrum utilization efficiency and good anti-multipath interference performance efficiently, therefore has been widely used in the Voice ﹠ Video field of broadcast type, and in the dual-use communication system.The main application of OFDM technology comprises: (the High-speed DigitalSubscriber Line of high bitrate digital subscriber line system, HDSL), asymmetrical Digital Subscriber Loop (Asymmetric Digital SubscriberLine, ADSL), ETSI (European Telecommunications Standards Institute, ETSI) digital audio broadcasting of standard (Digital Audio Broadcasting, DAB), digital video broadcasting (Digital Video Broadcasting, DVB), high definition TV (High DefinitionTelevision, HDTV), wireless MAN (WMAN), wireless lan (wlan), or the like.Particularly in wireless MAN and WLAN (wireless local area network) field, obtained extensive application as 802.16 series and 802.11 series standards of Main physical layer technology with the OFDM technology.
The OFDM technology is to carry with a large amount of orthogonal sub-carriers to need information transmitted.Therefore, ofdm system very easily is subjected to the adverse effect of narrow band interference.Narrow band interference herein promptly comprises the narrow band interference on the ordinary meaning, but also comprises the single-frequency interference.Because after FFT (fast fourier transform) conversion in the ofdm system, the frequency spectrum of simple signal no longer is line spectrum but occupies the narrow-band spectrum of certain bandwidth.When narrow band interference continues to exist, will cause long interference to system, have a strong impact on the performance of ofdm system.And when narrow band interference on frequency spectrum be used for the pilot sub-carrier of channel estimating when overlapping, this adverse effect will obtain diffusion by channel estimation errors, makes that the mis-behave degree of whole system is more serious.
The method that is used for Interference Cancellation at present is to offset narrow band interference by the fixed coefficient filter of constructing a plural coefficient.But when the structure filter coefficient, require the centre frequency of known narrow band interference or the estimated value of its degree of precision, otherwise can not obtain satisfied Interference Cancellation effect.The main shortcoming of the filter of fixed coefficient is that coefficient can not be adjusted in real time according to environmental change, so the environmental requirement that becomes can not satisfy the time of its performance; And when the coefficient of the filter of constructing some fixed coefficient, need be about the priori of signal statistics, these prioris are unforeseen often, or need estimate in real time, particularly the centre frequency of Gan Raoing can not obtain its actual value or very high-precision estimated value.Therefore, remove interference by fixed coefficient filter and can introduce processing delay, real-time is poor.
In sum, remove interference by fixed coefficient filter at present and can introduce processing delay, real-time is poor.
Summary of the invention
The embodiment of the invention provides a kind of method and sef-adapting filter of removing narrow band interference, removes interference and can introduce processing delay, the problem that real-time is poor in order to solve the fixed coefficient filter that passes through that exists in the prior art.
A kind of method of removing narrow band interference that the embodiment of the invention provides, this method comprises:
Sef-adapting filter is determined the weights of current sampling instant correspondence;
Described sef-adapting filter is determined the offseting signal of current sampling instant correspondence according to the weights of determining with in the reference signal of current sampling instant sampling, and wherein said reference signal is that the centre frequency according to narrow band interference generates;
Described sef-adapting filter is according to the offseting signal of the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
A kind of sef-adapting filter that the embodiment of the invention provides, this sef-adapting filter comprises:
The weights determination module is used for determining the weights of current sampling instant correspondence;
The signal determination module is used for determining the offseting signal of current sampling instant correspondence according to the weights of determining with in the reference signal of current sampling instant sampling, and wherein said reference signal is that the centre frequency according to narrow band interference generates;
Filtration module is used for the offseting signal according to the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
Embodiment of the invention sef-adapting filter is according to the weights of current sampling instant correspondence and the reference signal of sampling in current sampling instant, determine the offseting signal of current sampling instant correspondence, and according to the offseting signal of the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
Because the embodiment of the invention is removed narrow band interference by sef-adapting filter, thereby has reduced processing delay, has improved real-time, and adopt sef-adapting filter can adjust weights in real time, the environmental requirement that becomes when satisfying improves the Interference Cancellation effect.
Further, the realization of the embodiment of the invention is simple, and complexity is low, and reaction speed is fast, is fit to ofdm system more.
Description of drawings
Fig. 1 is the structural representation of embodiment of the invention sef-adapting filter;
Fig. 2 removes the method flow schematic diagram of narrow band interference for the embodiment of the invention;
Fig. 3 A is that the embodiment of the invention utilizes Notch (recess) filter to carry out in the filtering principle schematic diagram;
Fig. 3 B is the handling principle schematic diagram of embodiment of the invention Notch filter.
Embodiment
Embodiment of the invention sef-adapting filter is according to the weights of current sampling instant correspondence and the reference signal of sampling in current sampling instant, determine the offseting signal of current sampling instant correspondence, and according to the offseting signal of the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.Because the embodiment of the invention is removed narrow band interference by sef-adapting filter, thereby has reduced processing delay, has improved real-time, and adopt sef-adapting filter can adjust weights in real time, the environmental requirement that becomes when satisfying improves the Interference Cancellation effect.
Wherein, reference signal is to generate according to the centre frequency of narrow band interference.
Concrete, to having or not narrow band interference to detect and judging, the centre frequency to narrow band interference when narrow band interference is arranged is estimated, obtains narrow band interference center frequency estimation value f r, this frequency will be as the centre frequency of sef-adapting filter reference signal.
In specific implementation process, can be by narrowband interference detectors to having or not narrow band interference and detect and judge, and the centre frequency of narrow band interference is estimated, obtain narrow band interference center frequency estimation value.
Need to prove, the embodiment of the invention is not limited to narrowband interference detectors, other can be to having or not narrow band interference to detect and judge, and the centre frequency of narrow band interference is estimated that the mode that obtains narrow band interference center frequency estimation value all is suitable for the embodiment of the invention.
Wherein, the centre frequency according to narrow band interference just can generate reference signal.
Such as two reference signals of needs, then can generate two-way quadrature single-frequency reference signal r according to formula one and formula two sAnd r c, the two is respectively with f rSinusoidal reference signal and cosine reference signal for centre frequency:
r s(k)=Csin (2 π f rK) ... ... .. formula one;
r c(k)=Ccos (2 π f rK) ... .... formula two.
Wherein, r s(k) sinusoidal reference signal of k sampling instant sampling of expression; r c(k) the cosine reference signal of k sampling instant sampling of expression; C is the amplitude of reference signal, can set as required.
Because reference signal is a simple signal, therefore can only store the sampled value in the one-period, recursive call when filtering is to save memory resource; If become when the narrow band interference centre frequency is slow, can pass through computation of table lookup reference signal sampled value.
Need to prove that the embodiment of the invention is not limited to the mode of above-mentioned employing formula one and formula two generation reference signals, other modes that can generate reference signal according to the centre frequency of narrow band interference all are suitable for the embodiment of the invention.
In specific implementation process, can be by the filtering bandwidth that the sef-adapting filter parameter obtains a rational sef-adapting filter be set, and sef-adapting filter can be adjusted the filtered band centre frequency of self automatically, promptly can follow the tracks of the centre frequency of narrow band interference, therefore the exact value that does not need known narrow band interference centre frequency only needs the big probable value that certain precision is arranged.
Wherein, the embodiment of the invention can be applied to ofdm system, can also be applied to carry the system that needs information transmitted with a large amount of orthogonal sub-carriers.
Below in conjunction with Figure of description the embodiment of the invention is described in further detail.
As shown in Figure 1, embodiment of the invention sef-adapting filter comprises: weights determination module 10, signal determination module 20 and filtration module 30.
Weights determination module 10 is used for determining the weights of current sampling instant correspondence.
Signal determination module 20 is used for the weights determined according to weights determination module 10 and in the reference signal of current sampling instant sampling, determines the offseting signal of current sampling instant correspondence, and wherein reference signal is that centre frequency according to narrow band interference generates.
Filtration module 30 is used for the offseting signal of the current sampling instant correspondence determined according to signal determination module 20, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
Wherein, weights determination module 10 according to the weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in the reference signal of last sampling instant sampling, determine the weights of current sampling instant correspondence.
Concrete weights determination module 10 can adopt the weights of answering algorithm to determine current sampling instant correspondence voluntarily.Adaptive algorithm has a variety of, such as least mean-square error (Least Mean Square, LMS) algorithm, recurrence least square (Recursive Least Squares, RLS) algorithm, normalization LMS algorithm, variable step LMS algorithm etc.
Be that example describes below with the least-mean-square error algorithm, other algorithms and least-mean-square error algorithm are similar, and just the algorithm difference does not repeat them here.
If weights determination module 10 adopts least-mean-square error algorithm can determine the weights of current sampling instant correspondence according to formula three:
w ( k ) = w ( k - 1 ) + μ [ y ^ ( k - 1 ) + n ^ ( k - 1 ) ] r ( k - 1 ) ... ... .. formula three.
Wherein, w (k) is the weights of current sampling instant correspondence; W (k-1) is the weights of a last sampling instant correspondence; μ is the iterative computation step-length of adaptive algorithm;
Figure G2009102254497D00061
Be the useful signal in the baseband signal after narrow band interference is removed in a last sampling instant, Be other signals except that useful signal in the baseband signal after narrow band interference is removed in a last sampling instant (such as noise jamming etc.),
Figure G2009102254497D00063
With
Figure G2009102254497D00064
Constituted the baseband signal after narrow band interference is removed in a last sampling instant; R (k-1) is the reference signal in last sampling instant sampling.
If current sampling instant is first sampling instant, the weights of then going up a sampling instant correspondence are exactly predefined weights, and a last sampling instant is removed the baseband signal after the narrow band interference and all is 0 in the reference signal of last sampling instant sampling.
Wherein, the weights quantity that different sef-adapting filters needs is also inequality, is example with the Notch filter, needs two weights, and then weights comprise first weights and second weights; Accordingly, reference signal comprises first reference signal and second reference signal.
Weights determination module 10 need according to first weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in first reference signal of last sampling instant sampling, determine first weights of current sampling instant correspondence, and, determine second weights of current sampling instant correspondence according to second reference signal that second weights of a last sampling instant correspondence, a last sampling instant are removed the baseband signal after the narrow band interference and sampled in a last sampling instant.
With the least-mean-square error algorithm is example, then can derive formula four and formula five according to formula three, and weights determination module 10 is determined first weights according to formula four, determines second weights according to formula five:
w s ( k ) = w s ( k - 1 ) + μ [ y ^ ( k - 1 ) + n ^ ( k - 1 ) ] r s ( k - 1 ) ... ... .. formula four;
Wherein, w s(k) be first weights of current sampling instant correspondence; w s(k-1) be first weights of a last sampling instant correspondence; μ is the iterative computation step-length of adaptive algorithm;
Figure G2009102254497D00066
Be the useful signal in the baseband signal after narrow band interference is removed in a last sampling instant,
Figure G2009102254497D00067
Be to locate other outer signals of useful signal (such as noise jamming etc.) in the baseband signal after narrow band interference is removed in a last sampling instant,
Figure G2009102254497D00068
With
Figure G2009102254497D00071
Constituted the baseband signal after narrow band interference is removed in a last sampling instant; r s(k-1) be first reference signal of sampling in a last sampling instant.
w c ( k ) = w c ( k - 1 ) + μ [ y ^ ( k - 1 ) + n ^ ( k - 1 ) ] r c ( k - 1 ) ... ... .. formula five;
Wherein, w c(k) be first weights of current sampling instant correspondence; w c(k-1) be second weights of a last sampling instant correspondence; μ is the iterative computation step-length of adaptive algorithm;
Figure G2009102254497D00073
Be the useful signal in the baseband signal after narrow band interference is removed in a last sampling instant,
Figure G2009102254497D00074
Be to locate other outer signals of useful signal (such as noise jamming etc.) in the baseband signal after narrow band interference is removed in a last sampling instant,
Figure G2009102254497D00075
With
Figure G2009102254497D00076
Constituted the baseband signal after narrow band interference is removed in a last sampling instant; r c(k-1) be second reference signal of sampling in a last sampling instant.
Need to prove, if first weights determine that according to first reference signal then the first corresponding constantly weights of subsequent sampling all must be according to first reference signal; Accordingly, if second weights determine that according to first reference signal then the second corresponding constantly weights of subsequent sampling all must be according to second reference signal.
Such as first reference signal is sinusoidal reference signal, and second reference signal is the cosine reference signal.If first weights of first sampling instant correspondence are determined according to sinusoidal reference signal, second weights of first sampling instant correspondence are determined according to the cosine reference signal, then the first corresponding constantly weights of subsequent sampling must be determined according to sinusoidal reference signal, and the second corresponding constantly weights of subsequent sampling must be determined according to the cosine reference signal.
Can determine the offseting signal of current sampling instant correspondence according to formula six for signal determination module 20:
n ^ I ( k ) = w ( k ) r ( k ) ... ... ... formula six;
Wherein,
Figure G2009102254497D00078
It is offseting signal; W (k) is the weights of current sampling instant correspondence; R (k) is the reference signal in current sampling instant sampling.
If the sef-adapting filter of the embodiment of the invention needs two weights, then first reference signal of first weights of the current sampling instant correspondence that will determine of signal determination module 20 and current sampling instant sampling multiplies each other, obtain first processing signals of current sampling instant correspondence, second weights of definite current sampling instant correspondence and second reference signal of current sampling instant sampling are multiplied each other, obtain second processing signals of current sampling instant correspondence, with first processing signals and the second processing signals addition, obtain the offseting signal of current sampling instant correspondence.
Concrete, can derive formula seven according to formula six, signal determination module 20 can obtain the offseting signal of current sampling instant correspondence according to formula seven:
n ^ I ( k ) = w s ( k ) r s ( k ) + w c ( k ) r c ( k ) ... ... ... .. formula seven;
Wherein,
Figure G2009102254497D00082
It is the offseting signal of current sampling instant correspondence; w s(k) be first weights of current sampling instant correspondence; r s(k) be first reference signal of sampling in current sampling instant; w s(k) r s(k) be first processing signals of current sampling instant correspondence; w c(k) be second weights of current sampling instant correspondence; r c(k) be second reference signal of sampling in current sampling instant; w c(k) r c(k) be second processing signals of current sampling instant correspondence.
Wherein, filtration module 30 can subtract each other at the offseting signal of the baseband signal of current sampling instant sampling and the current sampling instant correspondence of determining, the signal that obtains is the baseband signal of removing after the narrow band interference.
Concrete, the signal that filtration module 30 can obtain according to formula eight is the baseband signal of removing after the narrow band interference:
y ^ ( k ) + n ^ ( k ) = s ( k ) - n ^ I ( k ) ... ... formula eight;
Wherein,
Figure G2009102254497D00084
Be the useful signal in the baseband signal after narrow band interference is removed in current sampling instant,
Figure G2009102254497D00085
Be other signals except that useful signal in the baseband signal after narrow band interference is removed in current sampling instant,
Figure G2009102254497D00086
Constituted the baseband signal after narrow band interference is removed in current sampling instant; S (k) is the baseband signal in current sampling instant sampling;
Figure G2009102254497D00087
It is the offseting signal of the definite current sampling instant correspondence of current sampling instant.
As shown in Figure 2, the method for embodiment of the invention removal narrow band interference comprises the following steps:
Step 201, sef-adapting filter are determined the weights of current sampling instant correspondence.
Step 202, sef-adapting filter are determined the offseting signal of current sampling instant correspondence according to the weights of determining with in the reference signal of current sampling instant sampling, and wherein reference signal is that centre frequency according to narrow band interference generates.
The offseting signal of the current sampling instant correspondence that step 203, sef-adapting filter basis are determined is to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
In the step 201, sef-adapting filter according to the weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in the reference signal of last sampling instant sampling, determine the weights of current sampling instant correspondence.
Concrete sef-adapting filter can adopt the weights of answering algorithm to determine current sampling instant correspondence voluntarily.Adaptive algorithm has a variety of, such as least-mean-square error algorithm, recursive least squares, and normalization LMS algorithm, variable step LMS algorithm etc.
Be that example describes below with the least-mean-square error algorithm, other algorithms and least-mean-square error algorithm are similar, and just the algorithm difference does not repeat them here.
If sef-adapting filter adopts least-mean-square error algorithm can determine the weights of current sampling instant correspondence according to formula three.
If current sampling instant is first sampling instant, the weights of then going up a sampling instant correspondence are exactly predefined weights, and a last sampling instant is removed the baseband signal after the narrow band interference and all is 0 in the reference signal of last sampling instant sampling.
Wherein, the weights quantity that different sef-adapting filters needs is also inequality, is example with the Notch filter, needs two weights, and then weights comprise first weights and second weights; Accordingly, reference signal comprises first reference signal and second reference signal.
In the step 201, sef-adapting filter need according to first weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in first reference signal of last sampling instant sampling, determine first weights of current sampling instant correspondence, and, determine second weights of current sampling instant correspondence according to second reference signal that second weights of a last sampling instant correspondence, a last sampling instant are removed the baseband signal after the narrow band interference and sampled in a last sampling instant.
With the least-mean-square error algorithm is example, then can derive formula four and formula five according to formula three, and sef-adapting filter is determined first weights according to formula four, determines second weights according to formula five.
Need to prove, if first weights determine that according to first reference signal then the first corresponding constantly weights of subsequent sampling all must be according to first reference signal; Accordingly, if second weights determine that according to first reference signal then the second corresponding constantly weights of subsequent sampling all must be according to second reference signal.
Such as first reference signal is sinusoidal reference signal, and second reference signal is the cosine reference signal.If first weights of first sampling instant correspondence are determined according to sinusoidal reference signal, second weights of first sampling instant correspondence are determined according to the cosine reference signal, then the first corresponding constantly weights of subsequent sampling must be determined according to sinusoidal reference signal, and the second corresponding constantly weights of subsequent sampling must be determined according to the cosine reference signal.
In the step 202, can determine the offseting signal of current sampling instant correspondence for sef-adapting filter according to formula six.
If the sef-adapting filter of the embodiment of the invention needs two weights, then in the step 202, first reference signal of first weights of the current sampling instant correspondence that sef-adapting filter will be determined and current sampling instant sampling multiplies each other, obtain first processing signals of current sampling instant correspondence, second weights of definite current sampling instant correspondence and second reference signal of current sampling instant sampling are multiplied each other, obtain second processing signals of current sampling instant correspondence, with first processing signals and the second processing signals addition, obtain the offseting signal of current sampling instant correspondence.
Concrete, can derive formula seven according to formula six, sef-adapting filter can obtain the offseting signal of current sampling instant correspondence according to formula seven.
In the step 203, sef-adapting filter can subtract each other at the offseting signal of the baseband signal of current sampling instant sampling and the current sampling instant correspondence of determining, the signal that obtains is the baseband signal of removing after the narrow band interference.
Concrete, the signal that sef-adapting filter can obtain according to formula eight is the baseband signal of removing after the narrow band interference.
The sef-adapting filter of the embodiment of the invention can be the Notch filter, such as notch filter, trapper etc., also can be other sef-adapting filters.Sef-adapting filter with the embodiment of the invention is that the Notch filter is that example describes below.
As shown in Figure 3A, the embodiment of the invention utilizes the Notch filter to carry out in the filtering principle schematic diagram:
At first, narrowband interference detectors is to having or not narrow band interference and detect and judging that the centre frequency to narrow band interference when narrow band interference is arranged is estimated, obtains narrow band interference center frequency estimation value f r
Then, the centre frequency according to narrow band interference generates sinusoidal reference signal r sWith cosine reference signal r c
At last, the Notch filter is according to sinusoidal reference signal r sWith cosine reference signal r c, to the baseband signal (s=y+n+n of input I) carry out filtering, the baseband signal after the narrow band interference that is removed
Figure G2009102254497D00111
And offseting signal
Figure G2009102254497D00112
Shown in Fig. 3 B, in the handling principle schematic diagram of embodiment of the invention Notch filter, three road signals are arranged, wherein one the tunnel is baseband signal s, comprises useful signal y, narrow-band interference signal n IWith other interference signals n; Another road is sinusoidal reference signal r sLast road is cosine reference signal r c
Wherein, sinusoidal reference signal r sWith cosine reference signal r cStore in the Notch filter, such as the sampled value in the storage one-period, then the Notch filter can receive one road signal, i.e. baseband signal S; Also can be similar to sinusoidal reference signal r with baseband signal s sWith cosine reference signal r cSend to the Notch filter, then the Notch filter can receive three road signals, i.e. baseband signal S, sinusoidal reference signal r sWith cosine reference signal r c
The Notch filter is according to the sinusoidal reference signal r of current sampling instant sampling s(k) and first weight w of current sampling instant correspondence s(k), determine first processing signals of current sampling instant correspondence
The Notch filter is according to the cosine reference signal r according to current sampling instant sampling c(k) and second weight w of current sampling instant correspondence c(k), determine second processing signals of current sampling instant correspondence
Figure G2009102254497D00114
The Notch filter is according to first processing signals of current sampling instant correspondence
Figure G2009102254497D00115
Second processing signals with current sampling instant correspondence
Figure G2009102254497D00121
Obtain the offseting signal of current sampling instant correspondence
Figure G2009102254497D00122
The Notch filter is according to the offseting signal of current sampling instant correspondence
Figure G2009102254497D00123
Baseband signal s (k) in current sampling instant sampling is carried out filtering, obtain the baseband signal after the narrow band interference of removing of current sampling instant correspondence
Figure G2009102254497D00124
After through one section convergence process, two weights of Notch filter will be restrained the optimal linear filtering weights that approach under the minimum mean square error criterion (supposing to adopt least-mean-square error algorithm), and what at this moment obtain is exactly the output signal of offsetting after the narrow band interference
Figure G2009102254497D00125
And the estimation waveform of narrow-band interference signal
Figure G2009102254497D00126
After the self adaptation convergence process finishes,
Figure G2009102254497D00127
To be that the y+n least mean-square error is estimated, and
Figure G2009102254497D00128
To be n ILeast mean-square error is estimated.
Figure G2009102254497D00129
Can directly use next step processing, for example channel estimating, demodulation, decoding or the like,
Figure G2009102254497D001210
Can be used for the calibration of primary signal and correction etc.
The adaptive-filtering of the embodiment of the invention can adopt the multiple hardwares device to realize, not only can adopt general processor, single-chip microcomputer and special-purpose digital signal processor, can also adopt programmable logic device etc.
From the foregoing description as can be seen: embodiment of the invention sef-adapting filter is determined the weights of current sampling instant correspondence; Sef-adapting filter is determined the offseting signal of current sampling instant correspondence according to the weights of determining with in the reference signal of current sampling instant sampling, and wherein reference signal is that centre frequency according to narrow band interference generates; Sef-adapting filter is according to the offseting signal of the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
The embodiment of the invention has made full use of the convergence time of Cyclic Prefix time as sef-adapting filter.
Because the embodiment of the invention is removed narrow band interference by sef-adapting filter, thereby has reduced processing delay, has improved real-time, and adopt sef-adapting filter can adjust weights in real time, the environmental requirement that becomes when satisfying improves the Interference Cancellation effect.
Further, the realization of the embodiment of the invention is simple, and complexity is low, and reaction speed is fast, is fit to ofdm system more.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

Claims (10)

1. a method of removing narrow band interference is characterized in that, this method comprises:
Sef-adapting filter is determined the weights of current sampling instant correspondence;
Described sef-adapting filter is determined the offseting signal of current sampling instant correspondence according to the weights of determining with in the reference signal of current sampling instant sampling, and wherein said reference signal is that the centre frequency according to narrow band interference generates;
Described sef-adapting filter is according to the offseting signal of the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
2. the method for claim 1 is characterized in that, described sef-adapting filter determines that the weights of current sampling point correspondence comprise:
Described sef-adapting filter according to the weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in the reference signal of last sampling instant sampling, determine the weights of current sampling instant correspondence.
3. method as claimed in claim 2 is characterized in that, described weights comprise first weights and second weights, and described reference signal comprises first reference signal and second reference signal;
Described sef-adapting filter determines that the weights of current sampling point correspondence comprise:
Described sef-adapting filter according to first weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in first reference signal of last sampling instant sampling, determine first weights of current sampling instant correspondence;
Described sef-adapting filter according to second weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in second reference signal of last sampling instant sampling, determine second weights of current sampling instant correspondence.
4. method as claimed in claim 3 is characterized in that, described sef-adapting filter determines that the offseting signal of current sampling instant correspondence comprises:
First reference signal of first weights of the current sampling instant correspondence that described sef-adapting filter will be determined and current sampling instant sampling multiplies each other, and obtains first processing signals of current sampling instant correspondence;
Second reference signal of second weights of the current sampling instant correspondence that described sef-adapting filter will be determined and current sampling instant sampling multiplies each other, and obtains second processing signals of current sampling instant correspondence;
Described sef-adapting filter obtains the offseting signal of current sampling instant correspondence with described first processing signals and the described second processing signals addition.
5. as the described method of the arbitrary claim of claim 1～4, it is characterized in that described sef-adapting filter comprises carrying out filtering in the baseband signal of current sampling instant sampling:
Described sef-adapting filter will subtract each other at the offseting signal of the baseband signal of current sampling instant sampling and the current sampling instant correspondence of determining, the signal that obtains is the baseband signal of removing after the narrow band interference.
6. a sef-adapting filter is characterized in that, this sef-adapting filter comprises:
The weights determination module is used for determining the weights of current sampling instant correspondence;
The signal determination module is used for determining the offseting signal of current sampling instant correspondence according to the weights of determining with in the reference signal of current sampling instant sampling, and wherein said reference signal is that the centre frequency according to narrow band interference generates;
Filtration module is used for the offseting signal according to the current sampling instant correspondence of determining, to carrying out filtering, the baseband signal after the narrow band interference that is removed in the baseband signal of current sampling instant sampling.
7. sef-adapting filter as claimed in claim 6 is characterized in that, described weights determination module is used for:
According to the reference signal that the weights of a last sampling instant correspondence, a last sampling instant are removed the baseband signal after the narrow band interference and sampled in a last sampling instant, determine the weights of current sampling instant correspondence.
8. sef-adapting filter as claimed in claim 7 is characterized in that, described weights determination module is used for:
Comprise first weights and second weights at described weights, when described reference signal comprises first reference signal and second reference signal, first weights according to a last sampling instant correspondence, first reference signal that a last sampling instant is removed the baseband signal after the narrow band interference and sampled in a last sampling instant, determine first weights of current sampling instant correspondence, and according to second weights of a last sampling instant correspondence, a last sampling instant remove after the narrow band interference baseband signal and in second reference signal of last sampling instant sampling, determine second weights of current sampling instant correspondence.
9. sef-adapting filter as claimed in claim 8 is characterized in that, described signal determination module is used for:
First weights of definite current sampling instant correspondence and first reference signal of current sampling instant sampling are multiplied each other, obtain first processing signals of current sampling instant correspondence, second weights of definite current sampling instant correspondence and second reference signal of current sampling instant sampling are multiplied each other, obtain second processing signals of current sampling instant correspondence, with described first processing signals and the described second processing signals addition, obtain the offseting signal of current sampling instant correspondence.
10. as the described sef-adapting filter of the arbitrary claim of claim 6～9, it is characterized in that described filtration module is used for:
To subtract each other at the offseting signal of the baseband signal of current sampling instant sampling and the current sampling instant correspondence of determining, the signal that obtains is the baseband signal of removing after the narrow band interference.
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