CN102098258B - 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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CN102098258B
CN102098258B CN 200910225449 CN200910225449A CN102098258B CN 102098258 B CN102098258 B CN 102098258B CN 200910225449 CN200910225449 CN 200910225449 CN 200910225449 A CN200910225449 A CN 200910225449A CN 102098258 B CN102098258 B CN 102098258B
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CN102098258A (en
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王守义
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ZTE Corp
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    • H03—ELECTRONIC CIRCUITRY
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    • H03H21/0012—Digital adaptive filters

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 the arrowband interference
Technical field
The present invention relates to the signal process field, particularly a kind of method and sef-adapting filter of removing the arrowband interference.
Background technology
OFDM (Orthogonal Frequency Division Multiplexing, OFDM) technology is a kind of multi-carrier digital modulation technique, is also a kind of channeling technology.Compare other modulation techniques and multiplex technique, the OFDM technology has efficient spectrum utilization efficiency and good anti-multipath interference performance, therefore has been widely used in the Voice ﹠ Video field of broadcast type, and in dual-use communication system.the main application of OFDM technology comprises: high bitrate digital subscriber line (the High-speed DigitalSubscriber Line of 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), WLAN (wireless local area network) (WLAN), etc..Particularly in wireless MAN and WLAN (wireless local area network) field, obtained extensive application with the OFDM technology as 802.16 series and 802.11 series standards of Main physical layer technology.
The OFDM technology is to carry with a large amount of orthogonal sub-carriers the information that needs transmission.Therefore, ofdm system very easily is subject to the adverse effect that the arrowband disturbs.Arrowband herein disturbs the arrowband that namely comprises on ordinary meaning to disturb, but also comprises the single-frequency interference.Because after FFT (fast fourier transform) conversion in ofdm system, the frequency spectrum of simple signal is no longer line spectrum but occupies the narrow-band spectrum of certain bandwidth.When the arrowband disturbs sustainable existence, will cause long interference to system, have a strong impact on the performance of ofdm system.And when the arrowband interference was overlapping with the pilot sub-carrier that is used for channel estimating on frequency spectrum, this adverse effect will be spread by channel estimation errors, makes the mis-behave degree of whole system more serious.
The method that is used at present Interference Cancellation is to offset the arrowband by the fixed coefficient filter of constructing a plural coefficient to disturb.But when the structure filter coefficient, require the centre frequency of known arrowband 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 to be about the priori of signal statistics, these prioris are unforeseen often, or need to estimate in real time, the centre frequency of particularly disturbing 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 present invention provides a kind of method and sef-adapting filter that the arrowband disturbs of removing, in order to solve removing interference by fixed coefficient filter and can introducing processing delay, the problem that real-time is poor of existing in prior art.
A kind of method of removing the arrowband interference that the embodiment of the present invention provides, the method comprises:
Sef-adapting filter is determined the weights that current sampling instant is corresponding;
The weights that described sef-adapting filter basis is determined and the reference signal of sampling in current sampling instant are determined the offseting signal that current sampling instant is corresponding, and wherein said reference signal is to generate according to the centre frequency that the arrowband disturbs;
Described sef-adapting filter carries out filtering according to offseting signal corresponding to current sampling instant of determining to the baseband signal of sampling in current sampling instant, the baseband signal after the arrowband that is removed disturbs.
A kind of sef-adapting filter that the embodiment of the present invention provides, this sef-adapting filter comprises:
The weights determination module is used for determining weights corresponding to current sampling instant;
The signal determination module, the reference signal that is used for the definite weights of basis and samples in current sampling instant is determined the offseting signal that current sampling instant is corresponding, wherein said reference signal is to generate according to the centre frequency that the arrowband disturbs;
Filtration module is used for according to offseting signal corresponding to current sampling instant of determining, to carrying out filtering in the baseband signal of current sampling instant sampling, and the baseband signal after the arrowband that is removed disturbs.
The weights that embodiment of the present invention sef-adapting filter is corresponding according to current sampling instant and the reference signal of sampling in current sampling instant, determine the offseting signal that current sampling instant is corresponding, and according to offseting signal corresponding to current sampling instant of determining, to carrying out filtering in the baseband signal of current sampling instant sampling, the baseband signal after the arrowband that is removed disturbs.
Because the embodiment of the present invention is removed the arrowband interference by sef-adapting filter, thereby reduced processing delay, improved real-time, and adopted sef-adapting filter can adjust in real time weights, the environmental requirement that becomes when satisfying improves the Interference Cancellation effect.
Further, the realization of the embodiment of the present invention is simple, and complexity is low, and reaction speed is fast, more is fit to ofdm system.
Description of drawings
Fig. 1 is the structural representation of embodiment of the present invention sef-adapting filter;
Fig. 2 is that the embodiment of the present invention is removed the method flow schematic diagram that the arrowband disturbs;
Fig. 3 A is that the embodiment of the present 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 present invention Notch filter.
Embodiment
The weights that embodiment of the present invention sef-adapting filter is corresponding according to current sampling instant and the reference signal of sampling in current sampling instant, determine the offseting signal that current sampling instant is corresponding, and according to offseting signal corresponding to current sampling instant of determining, to carrying out filtering in the baseband signal of current sampling instant sampling, the baseband signal after the arrowband that is removed disturbs.Because the embodiment of the present invention is removed the arrowband interference by sef-adapting filter, thereby reduced processing delay, improved real-time, and adopted sef-adapting filter can adjust in real time weights, the environmental requirement that becomes when satisfying improves the Interference Cancellation effect.
Wherein, reference signal is to generate according to the centre frequency that the arrowband disturbs.
Concrete, detect and judge having or not the arrowband to disturb, the centre frequency of when having the arrowband to disturb, the arrowband being disturbed is estimated, obtains the arrowband and disturbs 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 detect and judge having or not the arrowband to disturb by narrowband interference detectors, and the centre frequency that the arrowband disturbs is estimated, obtain the arrowband and disturb the center frequency estimation value.
Need to prove, the embodiment of the present invention is not limited to narrowband interference detectors, other can detect and judge having or not the arrowband to disturb, and the centre frequency that the arrowband disturbs are estimated to obtain the arrowband disturb the mode of center frequency estimation value all to be suitable for the embodiment of the present invention.
Wherein, the centre frequency of disturbing according to the arrowband just can generating reference signal.
Such as two reference signals of needs, can generate two-way quadrature single-frequency reference signal r according to formula one and formula two sAnd r c, both be respectively with f rCentered by sinusoidal reference signal and the cosine reference signal of 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 simple signal, therefore can only store the sampled value in one-period, recursive call when filtering is to save memory resource; If arrowband interference centre frequency becomes when being slow, can pass through computation of table lookup reference signal sampled value.
Need to prove, the embodiment of the present invention is not limited to the mode of above-mentioned employing formula one and formula two generating reference signals, and the mode of the centre frequency generating reference signal that other can disturb according to the arrowband all is suitable for the embodiment of the present invention.
In specific implementation process, can obtain by the sef-adapting filter parameter is set the filtering bandwidth of a rational sef-adapting filter, and sef-adapting filter can be adjusted the filtered band centre frequency of self automatically, namely can follow the tracks of the centre frequency that the arrowband disturbs, therefore do not need known arrowband to disturb the exact value of centre frequency, only need the large probable value that certain precision is arranged.
Wherein, the embodiment of the present invention can be applied to ofdm system, can also be applied to carry with a large amount of orthogonal sub-carriers the system of the information that needs transmission.
Below in conjunction with Figure of description, the embodiment of the present invention is described in further detail.
As shown in Figure 1, embodiment of the present 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 weights corresponding to current sampling instant.
Signal determination module 20 is used for the weights of determining according to weights determination module 10 and the reference signal of sampling in current sampling instant, determines the offseting signal that current sampling instant is corresponding, and wherein reference signal is to generate according to the centre frequency that the arrowband disturbs.
Filtration module 30 is used for offseting signal corresponding to current sampling instant definite according to signal determination module 20, to carrying out filtering in the baseband signal of current sampling instant sampling, and the baseband signal after the arrowband that is removed disturbs.
Wherein, the reference signal that the weights that weights determination module 10 is corresponding according to a upper sampling instant, a upper sampling instant are removed the baseband signal after the arrowband disturbs and sampled in a upper sampling instant is determined the weights that current sampling instant is corresponding.
Concrete weights determination module 10 can adopt answers algorithm to determine the weights that current sampling instant is corresponding 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, Normalized LMS Algorithm, New variable step-size LMS etc.
The below describes as an example of least-mean-square error algorithm example, and other algorithms and least-mean-square error algorithm are similar, and just algorithm is different, does not repeat them here.
If weights determination module 10 adopts least-mean-square error algorithm to determine weights corresponding to current sampling instant 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 weights corresponding to current sampling instant; W (k-1) is the upper weights that sampling instant is corresponding; μ is the iterative computation step-length of adaptive algorithm;
Figure G2009102254497D00061
The useful signal in the baseband signal after the arrowband interference is removed in a upper sampling instant,
Figure G2009102254497D00062
Other signals except useful signal in the baseband signal after a upper sampling instant is removed the arrowband and disturbed (such as noise jamming etc.),
Figure G2009102254497D00063
With
Figure G2009102254497D00064
Consisted of the baseband signal after the arrowband interference is removed in a upper sampling instant; R (k-1) is the reference signal in upper sampling instant sampling.
If current sampling instant is first sampling instant, going up weights corresponding to sampling instant is exactly predefined weights, the baseband signal after a upper sampling instant is removed the arrowband and disturbed and be all 0 in the reference signal of upper sampling instant sampling.
Wherein, the weights quantity that different sef-adapting filters needs is not identical yet, take the Notch filter as example, needs two weights, and weights comprise the first weights and the second weights; Accordingly, reference signal comprises the first reference signal and the second reference signal.
Weights determination module 10 need to be corresponding according to a upper sampling instant the first weights, a upper sampling instant after removing the arrowband and disturbing baseband signal and in the first reference signal of upper sampling instant sampling, determine the first weights that current sampling instant is corresponding, and second weights corresponding according to a upper sampling instant, a upper sampling instant remove after the arrowband disturbs baseband signal and in the second reference signal of upper sampling instant sampling, determine the second weights that current sampling instant is corresponding.
Take least-mean-square error algorithm as example, can derive formula four and formula five according to formula three, weights determination module 10 is determined the first weights according to formula four, determines the 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 the first weights corresponding to current sampling instant; w s(k-1) be the first weights corresponding to a upper sampling instant; μ is the iterative computation step-length of adaptive algorithm;
Figure G2009102254497D00066
The useful signal in the baseband signal after the arrowband interference is removed in a upper sampling instant,
Figure G2009102254497D00067
To locate other outer signals of useful signal (such as noise jamming etc.) in the baseband signal after a upper sampling instant is removed the arrowband and disturbed,
Figure G2009102254497D00068
With
Figure G2009102254497D00071
Consisted of the baseband signal after the arrowband interference is removed in a upper sampling instant; r s(k-1) be first reference signal of sampling in a upper 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 the first weights corresponding to current sampling instant; w c(k-1) be the second weights corresponding to a upper sampling instant; μ is the iterative computation step-length of adaptive algorithm;
Figure G2009102254497D00073
The useful signal in the baseband signal after the arrowband interference is removed in a upper sampling instant,
Figure G2009102254497D00074
To locate other outer signals of useful signal (such as noise jamming etc.) in the baseband signal after a upper sampling instant is removed the arrowband and disturbed,
Figure G2009102254497D00075
With Consisted of the baseband signal after the arrowband interference is removed in a upper sampling instant; r c(k-1) be second reference signal of sampling in a upper sampling instant.
Need to prove, if the first weights are definite according to the first reference signal, the first weights of correspondence all must be according to the first reference signal constantly for subsequent sampling; Accordingly, if the second weights are definite according to the first reference signal, the second weights of correspondence all must be according to the second reference signal constantly for subsequent sampling.
Such as the first reference signal is sinusoidal reference signal, the second reference signal is the cosine reference signal.If the first weights corresponding to first sampling instant are determined according to sinusoidal reference signal, the second weights corresponding to first sampling instant are determined according to the cosine reference signal, the first weights of correspondence must be definite according to sinusoidal reference signal constantly for subsequent sampling, and subsequent sampling the second weights of correspondence constantly must be determined according to the cosine reference signal.
Can determine offseting signal corresponding to current sampling instant 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 weights corresponding to current sampling instant; R (k) is the reference signal in current sampling instant sampling.
If the sef-adapting filter of the embodiment of the present invention needs two weights, the first weights corresponding to the current sampling instant that will determine of signal determination module 20 and the first reference signal of current sampling instant sampling multiply each other, obtain the first processing signals corresponding to current sampling instant, the second reference signal of the second weights that the current sampling instant of determining is corresponding and current sampling instant sampling multiplies each other, obtain the second processing signals corresponding to current sampling instant, with the first processing signals and the second processing signals addition, obtain offseting signal corresponding to current sampling instant.
Concrete, can derive formula seven according to formula six, signal determination module 20 can obtain offseting signal corresponding to current sampling instant according to formula seven:
n ^ I ( k ) = w s ( k ) r s ( k ) + w c ( k ) r c ( k ) ... ... ... .. formula seven;
Wherein,
Figure G2009102254497D00082
Offseting signal corresponding to current sampling instant; w s(k) be the first weights corresponding to current sampling instant; r s(k) be first reference signal of sampling in current sampling instant; w s(k) r s(k) be the first processing signals corresponding to current sampling instant; w c(k) be the second weights corresponding to current sampling instant; r c(k) be second reference signal of sampling in current sampling instant; w c(k) r c(k) be the second processing signals corresponding to current sampling instant.
Wherein, filtration module 30 can will subtract each other in the baseband signal of current sampling instant sampling and offseting signal corresponding to current sampling instant of determining, the signal that obtains is the baseband signal of removing after the arrowband disturbs.
Concrete, the signal that filtration module 30 can obtain according to formula eight is the baseband signal of removing after the arrowband disturbs:
y ^ ( k ) + n ^ ( k ) = s ( k ) - n ^ I ( k ) ... ... formula eight;
Wherein,
Figure G2009102254497D00084
The useful signal in the baseband signal after the arrowband interference is removed in current sampling instant,
Figure G2009102254497D00085
Other signals except useful signal in the baseband signal after the arrowband interference is removed in current sampling instant,
Figure G2009102254497D00086
Consisted of the baseband signal after the arrowband interference is removed in current sampling instant; S (k) is the baseband signal in current sampling instant sampling;
Figure G2009102254497D00087
Offseting signal corresponding to current sampling instant that current sampling instant is determined.
As shown in Figure 2, the method for embodiment of the present invention removal arrowband interference comprises the following steps:
Step 201, sef-adapting filter are determined the weights that current sampling instant is corresponding.
The weights that step 202, sef-adapting filter basis are determined and the reference signal of sampling in current sampling instant are determined the offseting signal that current sampling instant is corresponding, and wherein reference signal is to generate according to the centre frequency that the arrowband disturbs.
Step 203, sef-adapting filter carry out filtering according to offseting signal corresponding to current sampling instant of determining to the baseband signal of sampling in current sampling instant, the baseband signal after the arrowband that is removed disturbs.
In step 201, the reference signal that the weights that sef-adapting filter is corresponding according to a upper sampling instant, a upper sampling instant are removed the baseband signal after the arrowband disturbs and sampled in a upper sampling instant is determined the weights that current sampling instant is corresponding.
Concrete sef-adapting filter can adopt answers algorithm to determine the weights that current sampling instant is corresponding voluntarily.Adaptive algorithm has a variety of, such as least-mean-square error algorithm, recursive least squares, Normalized LMS Algorithm, New variable step-size LMS etc.
The below describes as an example of least-mean-square error algorithm example, and other algorithms and least-mean-square error algorithm are similar, and just algorithm is different, does not repeat them here.
If sef-adapting filter adopts least-mean-square error algorithm to determine weights corresponding to current sampling instant according to formula three.
If current sampling instant is first sampling instant, going up weights corresponding to sampling instant is exactly predefined weights, the baseband signal after a upper sampling instant is removed the arrowband and disturbed and be all 0 in the reference signal of upper sampling instant sampling.
Wherein, the weights quantity that different sef-adapting filters needs is not identical yet, take the Notch filter as example, needs two weights, and weights comprise the first weights and the second weights; Accordingly, reference signal comprises the first reference signal and the second reference signal.
In step 201, sef-adapting filter need to be corresponding according to a upper sampling instant the first weights, a upper sampling instant after removing the arrowband and disturbing baseband signal and in the first reference signal of upper sampling instant sampling, determine the first weights that current sampling instant is corresponding, and second weights corresponding according to a upper sampling instant, a upper sampling instant remove after the arrowband disturbs baseband signal and in the second reference signal of upper sampling instant sampling, determine the second weights that current sampling instant is corresponding.
Take least-mean-square error algorithm as example, can derive formula four and formula five according to formula three, sef-adapting filter is determined the first weights according to formula four, determines the second weights according to formula five.
Need to prove, if the first weights are definite according to the first reference signal, the first weights of correspondence all must be according to the first reference signal constantly for subsequent sampling; Accordingly, if the second weights are definite according to the first reference signal, the second weights of correspondence all must be according to the second reference signal constantly for subsequent sampling.
Such as the first reference signal is sinusoidal reference signal, the second reference signal is the cosine reference signal.If the first weights corresponding to first sampling instant are determined according to sinusoidal reference signal, the second weights corresponding to first sampling instant are determined according to the cosine reference signal, the first weights of correspondence must be definite according to sinusoidal reference signal constantly for subsequent sampling, and subsequent sampling the second weights of correspondence constantly must be determined according to the cosine reference signal.
In step 202, can determine offseting signal corresponding to current sampling instant according to formula six for sef-adapting filter.
if the sef-adapting filter of the embodiment of the present invention needs two weights, in step 202, the first reference signal of the first weights that the current sampling instant that sef-adapting filter will be determined is corresponding and current sampling instant sampling multiplies each other, obtain the first processing signals corresponding to current sampling instant, the second reference signal of the second weights that the current sampling instant of determining is corresponding and current sampling instant sampling multiplies each other, obtain the second processing signals corresponding to current sampling instant, with the first processing signals and the second processing signals addition, obtain offseting signal corresponding to current sampling instant.
Concrete, can derive formula seven according to formula six, sef-adapting filter can obtain offseting signal corresponding to current sampling instant according to formula seven.
In step 203, sef-adapting filter can will subtract each other in the baseband signal of current sampling instant sampling and offseting signal corresponding to current sampling instant of determining, the signal that obtains is the baseband signal of removing after the arrowband disturbs.
Concrete, the signal that sef-adapting filter can obtain according to formula eight is the baseband signal of removing after the arrowband disturbs.
The sef-adapting filter of the embodiment of the present invention can be the Notch filter, such as notch filter, trapper etc., can be also other sef-adapting filters.To be the Notch filter take the sef-adapting filter of the embodiment of the present invention describe as example the below.
As shown in Figure 3A, the embodiment of the present invention utilizes the Notch filter to carry out in the filtering principle schematic diagram:
At first, narrowband interference detectors detects and judges having or not the arrowband to disturb, and the centre frequency of when having the arrowband to disturb, the arrowband being disturbed is estimated, obtains the arrowband and disturbs center frequency estimation value f r
Then, the centre frequency of disturbing according to the arrowband 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 arrowband that is removed disturbs
Figure G2009102254497D00111
And offseting signal
Figure G2009102254497D00112
As shown in Fig. 3 B, in the handling principle schematic diagram of embodiment of the present 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, 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, 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 the first weight w corresponding to current sampling instant s(k), determine the first processing signals that current sampling instant is corresponding
Figure G2009102254497D00113
The Notch filter is according to the cosine reference signal r according to current sampling instant sampling c(k) and the second weight w corresponding to current sampling instant c(k), determine the second processing signals that current sampling instant is corresponding
Figure G2009102254497D00114
The first processing signals that the Notch filter is corresponding according to current sampling instant
Figure G2009102254497D00115
Second processing signals corresponding with current sampling instant
Figure G2009102254497D00121
Obtain offseting signal corresponding to current sampling instant
The offseting signal that the Notch filter is corresponding according to current sampling instant
Figure G2009102254497D00123
Baseband signal s (k) in current sampling instant sampling is carried out filtering, obtain current sampling instant corresponding remove baseband signal after the arrowband disturbs
Figure G2009102254497D00124
After through one section convergence process, two weights of Notch filter will be restrained close to the optimal linear filtering weights under 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 arrowband disturbs
Figure G2009102254497D00125
And the estimation waveform of narrow-band interference signal
Figure G2009102254497D00126
After the self adaptation convergence process finishes, 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 etc.,
Figure G2009102254497D001210
Can be used for the calibration of primary signal and correction etc.
The adaptive-filtering of the embodiment of the present 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.
Can find out from above-described embodiment: embodiment of the present invention sef-adapting filter is determined the weights that current sampling instant is corresponding; The weights that the sef-adapting filter basis is determined and the reference signal of sampling in current sampling instant are determined the offseting signal that current sampling instant is corresponding, and wherein reference signal is to generate according to the centre frequency that the arrowband disturbs; Sef-adapting filter carries out filtering according to offseting signal corresponding to current sampling instant of determining to the baseband signal of sampling in current sampling instant, the baseband signal after the arrowband that is removed disturbs.
The embodiment of the present invention takes full advantage of the Cyclic Prefix time as the convergence time of sef-adapting filter.
Because the embodiment of the present invention is removed the arrowband interference by sef-adapting filter, thereby reduced processing delay, improved real-time, and adopted sef-adapting filter can adjust in real time weights, the environmental requirement that becomes when satisfying improves the Interference Cancellation effect.
Further, the realization of the embodiment of the present invention is simple, and complexity is low, and reaction speed is fast, more is fit to ofdm system.
Obviously, those skilled in the art can carry out various changes and modification and not break away from the spirit and scope of the present invention the present invention.Like this, if within of the present invention these are revised and modification belongs to the scope of claim of the present invention and equivalent technologies thereof, the present invention also is intended to comprise these changes and modification interior.

Claims (4)

1. remove the method that the arrowband disturbs for one kind, it is characterized in that, the method comprises:
Sef-adapting filter is determined the weights that current sampling instant is corresponding;
The weights that described sef-adapting filter basis is determined and the reference signal of sampling in current sampling instant are determined the offseting signal that current sampling instant is corresponding, and wherein said reference signal is to generate according to the centre frequency that the arrowband disturbs;
Described sef-adapting filter carries out filtering according to offseting signal corresponding to current sampling instant of determining to the baseband signal of sampling in current sampling instant, the baseband signal after the arrowband that is removed disturbs;
Wherein, described weights comprise the first weights and the second weights, and described reference signal comprises sinusoidal reference signal and cosine reference signal;
Described sef-adapting filter determines that weights corresponding to current sampling instant comprise:
The sinusoidal reference signal that the first weights that described sef-adapting filter is corresponding according to a upper sampling instant, a upper sampling instant are removed the baseband signal after the arrowband disturbs and sampled in a upper sampling instant is determined the first weights that current sampling instant is corresponding; And second weights corresponding according to a upper sampling instant, a upper sampling instant remove after the arrowband disturbs baseband signal and in the cosine reference signal of upper sampling instant sampling, determine the second weights that current sampling instant is corresponding;
Described sef-adapting filter determines that offseting signal corresponding to current sampling instant comprises:
The sinusoidal reference signal of the first weights that the current sampling instant that described sef-adapting filter will be determined is corresponding and current sampling instant sampling multiplies each other, and obtains the first processing signals corresponding to current sampling instant; The cosine reference signal of the second weights that the current sampling instant of determining is corresponding and current sampling instant sampling multiplies each other, and obtains the second processing signals corresponding to current sampling instant; And with described the first processing signals and described the second processing signals addition, obtain offseting signal corresponding to current sampling instant;
Described reference signal is sinusoidal reference signal, according to following formula generating reference signal:
r s(k)＝Csin(2πf rk)
Described reference signal is the cosine reference signal, according to following formula generating reference signal:
r c(k)＝Ccos(2πf rk)
R wherein 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, f rCentre frequency for the arrowband interference.
2. the method for claim 1, 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 in the baseband signal of current sampling instant sampling and offseting signal corresponding to current sampling instant of determining, the signal that obtains is the baseband signal of removing after the arrowband disturbs.
3. a sef-adapting filter, is characterized in that, this sef-adapting filter comprises:
The weights determination module is used for determining weights corresponding to current sampling instant;
The signal determination module, the reference signal that is used for the definite weights of basis and samples in current sampling instant is determined the offseting signal that current sampling instant is corresponding, wherein said reference signal is to generate according to the centre frequency that the arrowband disturbs;
Filtration module is used for according to offseting signal corresponding to current sampling instant of determining, to carrying out filtering in the baseband signal of current sampling instant sampling, and the baseband signal after the arrowband that is removed disturbs;
Wherein, described weights comprise the first weights and the second weights, and described reference signal comprises sinusoidal reference signal and cosine reference signal;
Described weights determination module, be used for the first reference signal that first weights, a upper sampling instant corresponding according to a upper sampling instant removed the baseband signal after the arrowband disturbs and sampled in a upper sampling instant, determine the first weights that current sampling instant is corresponding, and second weights corresponding according to a upper sampling instant, a upper sampling instant remove after the arrowband disturbs baseband signal and in the second reference signal of upper sampling instant sampling, determine the second weights that current sampling instant is corresponding;
Described signal determination module, being used for the first weights corresponding to the current sampling instant that will determine and the first reference signal of current sampling instant sampling multiplies each other, obtain the first processing signals corresponding to current sampling instant, the second reference signal of the second weights that the current sampling instant of determining is corresponding and current sampling instant sampling multiplies each other, obtain the second processing signals corresponding to current sampling instant, with described the first processing signals and described the second processing signals addition, obtain offseting signal corresponding to current sampling instant;
Described reference signal is sinusoidal reference signal, according to following formula generating reference signal:
r s(k)＝Csin(2πf rk)
Described reference signal is the cosine reference signal, according to following formula generating reference signal:
r c(k)＝Ccos(2πf rk)
R wherein 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, f rCentre frequency for the arrowband interference.
4. sef-adapting filter as claimed in claim 3, is characterized in that, described filtration module is used for:
To subtract each other in the baseband signal of current sampling instant sampling and offseting signal corresponding to current sampling instant of determining, the signal that obtains is the baseband signal of removing after the arrowband disturbs.
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