CN103095619A - Direct current elimination method and direct current elimination device - Google Patents

Abstract

The invention provides a direct current elimination method and a direction current elimination device. The direct current elimination method comprises that direct current elimination is carried out on received data after analog-digital conversion using an averaging method; original channel estimation is carried out on the last 128 chip data of a Midamble code of the received data, and coefficients of taps after channel estimation are calculated; and according to an original channel estimation result, a tap with power smaller than a set threshold is selected to be conducted with residual direct current elimination process. According to the direct current elimination method and the direction current elimination device, digital information after analog-digital conversion is conducted with direct current elimination using the averaging method, then the residual direction current elimination method is used for secondary direct current elimination, and accordingly direct current elimination of the digital signal is more complete.

Description

Direct current removing method and device

Technical field

The present invention relates to communication technical field, relate in particular to a kind of direct current removing method and device.

Background technology

At TD-SCDMA (Time Division-Synchronous Code Division Multiple Access, TD SDMA) in system, terminal before carrying out descending joint detection algorithm, at first will be to the carrying out after radio frequency reception the digital signal that transforms of A/D (analog/digital) carry out the direct current Processing for removing.Different radio-frequency transmitter performance differences is very large, also is not quite similar for the direct current processing policy in the A/D conversion process that receives signal.

In the TD-SCDMA system, subframe structure and conventional structure of time slot as shown in Figure 1, the duration of each subframe is 5ms, each subframe one is divided into 7 conventional time slots and 3 special time slots.Wherein, the conventional time slot that can be used as downlink business in each subframe has 6 conventional time slots such as TS0 and TS2～TS6.In each conventional time slot, data symbol is positioned at Midamble (training sequence) yard both sides, and the protection interval (GP) of 16 chip (chip) is arranged at the time slot afterbody.Descending joint-detection is carried out data and is processed take a time slot as unit, for conventional time slot, existing direct current elimination algorithm mainly contains: segmentation direct current method (abbreviation discrete method) and the whole time slot average direct current method (abbreviation averaging method) that disappears that disappears, and invent in CN101304256 read the method (being called for short the AGC method) of corresponding DC component according to current AGC (receiver gain) value, wherein

(1) discrete method: be that data with a time slot are divided into some parts, every a part of IQ (inphase/orthogonal component) two paths of signals is averaged respectively, as the DC component of this segment data, the IQ two paths of signals is deducted respectively DC component eliminate direct current successively.Do like this and might cause signal power skewness weighing apparatus in whole time slot because after data sectional, the average of every segment data is not identical, cause that combined detection performance descends.

(2) averaging method: be simple direct current removing method at present commonly used, the method is eliminated direct current with the average of the whole time slot IQ two paths of signals DC component as this time slot with the DC component that the IQ two paths of signals deducts respectively separately.As descending spreading factor SF=16, and when the code channel number of configuration was more, receive data was the stack of many code channels data, had certain randomness because send data sample, adopt averaging method not only might eliminate unclean residual direct current, might introduce more DC component on the contrary.But in the TD-SCDMA system, averaging method is slightly excellent with respect to the discrete method performance.

(3) AGC method: need at first will obtain the size of receiver DC component under different AGC, each reception signal reads corresponding DC component according to the AGC value and eliminates.This way need take long to after starting up of terminal and set up the corresponding relation of AGC and direct current, and DC component only limits to the direct current size in sample, can not travel through various situations, and the result of joint-detection is subject to different ﹠ RF Components receptivities very much.

Above-mentioned DC detection method can accurately not realized the direct current of the digital signal after the A/D conversion is eliminated.

Summary of the invention

Can't accurately carry out direct current elimination problem, the method and apparatus that the embodiment of the present invention provides a kind of direct current to eliminate to the numeral after analog-to-digital conversion for solving in prior art.

A kind of direct current removing method comprises:

Eliminate utilize averaging method to carry out direct current through the receive data after analog-to-digital conversion;

The rear 128 chip data of described receive data Midamble code part are done original channel estimate, calculate the coefficient of each tap after channel estimating;

According to original estimation result, choose power and do residual direct current Processing for removing less than the tap of setting thresholding.

A kind of direct current cancellation element comprises:

Whole time slot average direct current cancellation element is used for eliminating utilize averaging method to carry out direct current through the receive data after analog-to-digital conversion;

Channel estimating apparatus is used for described receive data is carried out the original channel algorithm for estimating, calculates the coefficient of each tap after channel estimating;

Residual direct current estimation unit is used for realization to the best estimate of residual direct current;

Residual direct current cancellation element is used for realization the residual DC that described residual direct current estimation unit estimates is eliminated from described receive data.

Direct current removing method and device that the embodiment of the present invention provides, carry out the direct current elimination to first carry out averaging method through the digital information after analog-to-digital conversion, and then carry out for the second time direct current according to residual direct current null method and eliminate, can make so more thorough that the direct current of digital signal eliminates.

Description of drawings

Fig. 1 is TD-SCDMA system convention structure of time slot schematic diagram;

Fig. 2 is Midamble code structure schematic diagram;

Fig. 3 is the receive data analogous diagram that contains residual DC component;

Fig. 4 is the averaging method channel impulse response;

Fig. 5 is averaging method demodulation planisphere;

Fig. 6 is channel impulse response analogous diagram in the embodiment of the present invention;

Fig. 7 is demodulation planisphere in the embodiment of the present invention;

Fig. 8 is that the receive data SNR that contains residual DC component measures distribution schematic diagram

Fig. 9 is the analogous diagram of embodiment of the present invention block error rate BLER;

Figure 10 is throughput schematic diagram in the embodiment of the present invention;

Figure 11 is embodiment of the present invention direct current cancellation element schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, a kind of direct current removing method of the present invention and device are described in detail.

The embodiment of the present invention provides a kind of direct current removing method and device, comprising:

S1, eliminate utilize averaging method to carry out direct current through the receive data after analog-to-digital conversion;

S2, the rear 128 chip data of receive data Midamble code part are done original channel estimate, calculate the coefficient of each tap after channel estimating;

S3, according to original estimation result, choose power and do residual direct current Processing for removing less than the tap of setting thresholding.

in embodiments of the present invention, the thresholding of this setting can be done different processing according to concrete application scenarios, as set in third generation partner program 3GPP agreement several with reference to mobile channel (as PA3, PB3, VA30, VA120) under condition, minimum BLER value needed according to the different business performance, emulation obtains a BLER needed wealthy family limit value that satisfies that business allows, thresholding as the direct current elimination, all make residual direct current Processing for removing less than the tap of this setting thresholding, rule of thumb be worth, the span of this thresholding can be [1/64, 1/512] between.

In one embodiment of the invention, described to utilize averaging method to carry out the direct current elimination through the receive data after analog-to-digital conversion, comprising:

In described receive data in each time slot, with the average of the whole time slot IQ two paths of signals DC component as this time slot, the DC component that the IQ two paths of signals deducts is respectively separately eliminated direct current.

In another one embodiment of the present invention, described according to original estimation result, choose power and do residual direct current Processing for removing less than the tap of setting thresholding, comprising:

Calculating lower than the power of all taps of described thresholding and minimum value;

According to the power of described all taps and minimum value calculate the size of described residual direct current;

Carrying out direct current according to the size of described residual direct current eliminates.、

In embodiments of the present invention, the relation of estimating by deriving residual DC component and original channel, and then calculate the way that satisfies this part tap power sum minimum, estimate the size of residual direct current, again this part direct current is eliminated from system, thereby will eliminate through the direct current in the digital signal after analog-to-digital conversion the elevator system performance fully.

The embodiment of the present invention provides a kind of direct current removing method and device, comprising:

(1) do the direct current elimination to receiving the data averaging method, to eliminate the data before large DC component is supposed joint-detection eFor process Quadrature Phase Shift Keying QPSK or the data of quadrature amplitude modulation QAM modulation, namely through the data after the A/D conversion, its symbol sebolic addressing e(n) with being expressed as

e(n)＝e _I(n)+je _Q(n)，n＝0，1，L N-1，N＝864 (1)

E wherein _I(n) and e _Q(n) be respectively in-phase component sequence (I road) and the quadrature component sequence (Q road) of data.

If

Data after the averaging method direct current is eliminated e' symbol sebolic addressing e' (n) can be expressed as

${\underset{\‾}{e}}^{\′}\left(n\right)=(e_I\left(n\right)-{\stackrel{\‾}{e}}_I)+j(e_Q\left(n\right)-{\stackrel{\‾}{e}}_Q)={e^{\′}}_I\left(n\right)+j{e^{\′}}_Q\left(n\right)---\left(2\right)$

(2) adopt the rear 128chip of Midamble code to do the original channel estimation;

Because be subjected to the such environmental effects such as multipath, above-mentioned front 16chip through the Midamble code in the digital signal after the A/D conversion easily is subject to the impact of Data symbols 0 data division in Fig. 1, carry out channel estimating so only get rear 128chip, the Midamble code data of establishing through the 128chip after step (1) is e' _m, establishing 128 Fourier's changes (DFT) and anti-Fourier change (IDFT) can represent with change square formation DFTX and IDFTX respectively, original estimation result can be expressed as h _raw

h _raw＝IDFTX· G ^-1·DFTX· e′ _m (3)

Wherein GBe diagonal matrix, its diagonal entry vector is:

g＝DFTX· m _P (4)

Wherein m _P=( m ₁, m ₂..., m _P) be the local Basic Midamble code after modulation, P=128 wherein establishes residual direct current vector and is DC=( DC, DC, K DC) _P, wherein DCBe residual DC quantity, and the Midamble code is identical with the residual direct current size of data division, supposes to eliminate residual direct current DCAfter channel estimation results be h' _raw, have

h′ _raw＝IDFTX· G ^-1·DFTX·( e′ _m- DC)

＝IDFTX· G ^-1·DFTX· e′ _m-IDFTX· G ^-1·DFTX· DC (5)

＝ h _raw- DC·IDFTX· G ^-1·P·δ

Wherein $\mathrm{\&delta;}={\left[\begin{array}{c}1\\ 0\\ \mathrm{<figure-callout\; id="0"\; label="M"\; filenames="HDA0000103393630000013.png,HDA0000103393630000021.png"\; state="\{\{state\}\}">M</figure-callout>}\\ 0\\ 0\end{array}\right]}_{P\&times;1},$ If e _mid(n)= m _P=( m ₁, m ₂, K, m _P),

E wherein _mid(0)= m ₁, e _mid(1)= m ₂, L, e mid(P-1)= m _P

By $\underset{\&OverBar;}{g}=\mathrm{DFTX}\&CenterDot;{\underset{\&OverBar;}{m}}_P\&DoubleLeftRightArrow;g\left(k\right)=\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_P^{\mathrm{kn}},$ Wherein $W_P^{\mathrm{nk}}=\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000103393630000021.png,HDA0000103393630000023.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{P}\mathrm{nk})$

$\underset{\&OverBar;}{G}=\mathrm{diag}(\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right),\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_P^n,L\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_p^{n(k-1)},\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_P^{\mathrm{nk}})$

${\underset{\&OverBar;}{G}}^{-1}\&CenterDot;\mathrm{\&delta;}=\mathrm{diag}(\frac{1}{\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)},\frac{1}{\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_P^n},L,\frac{1}{\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_P^{n(k-1)}},\frac{1}{\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)W_P^{\mathrm{nk}}})\&CenterDot;{\left[\begin{array}{c}1\\ 0\\ \mathrm{<figure-callout\; id="0"\; label="M"\; filenames="HDA0000103393630000013.png,HDA0000103393630000021.png"\; state="\{\{state\}\}">M</figure-callout>}\\ 0\\ 0\end{array}\right]}_{P\&times;1}$

$=\frac{1}{\underset{n=0}{\overset{P-1}{\mathrm{\&Sigma;}}}{e}_{\mathrm{mid}}\left(n\right)}\&CenterDot;\mathrm{\&delta;}={\underset{\&OverBar;}{E}}_{\mathrm{mid}}\&CenterDot;\mathrm{\&delta;}---\left(6\right)$

Wherein diag ( X) represent by vector xThe diagonal matrix that forms, E _midFor local Midamble code P point plural number and inverse.Can release in the time of thus

h′ _raw＝ h _raw- DC· E _mid·IDFTX·(P·δ)＝ h _raw- E _mid· DC (7)

If H' _raw(n)= h' _raw, H _raw(n)= h _raw, n=0,1, L, P-1, after eliminating residual direct current, relation is as follows as a result for the channel estimation sequence of channel estimation results and the residual direct current that do not disappear

H′ _raw(n)＝ H _raw(n)- DC· E _mid (8)

(3) choose the intercepting thresholding of original estimation result, computing is carried out in the tap less than threshold value, purpose is power and the minimum of power after residual direct current is eliminated that makes these taps.

At first obtaining original channel estimates H _raw(n) maximum tap power H _{Raw_max}, set η _RatioBe the thresholding coefficient of tap intercepting, η _RatioBetween 0 to 1, generally can be given by emulation.If surpass total w of the tap of thresholding, the sequence of tap sequence number can be expressed as n _r=[n ₁, n ₂, L n _w], n ₁, n ₂, L n _w∈ 0,1, and K P-1 has | H _raw(n _r) | ²＞η _RatioH _{Raw_max}Without loss of generality, we establish

$\left\{\begin{array}{c}{\underset{\&OverBar;}{H}}_{\mathrm{raw}}\left(n\right)=H_{\mathrm{raw}\_I}\left(n\right)+j{H}_{\mathrm{raw}\_Q}\left(n\right)\\ {\underset{\&OverBar;}{E}}_{\mathrm{mid}}=E_{\mathrm{mid}\_I}+j{E}_{\mathrm{mid}\_Q}\\ \underset{\&OverBar;}{\mathrm{DC}}={\mathrm{DC}}_I+{\mathrm{jDC}}_Q\end{array}\right.---\left(9\right)$

H wherein _{Raw_I}(n) and H _{Raw_Q}(n) be respectively IQ (inphase/orthogonal component) two paths of data that original channel is estimated, E _{Mid_I}And E _{Mid_Q}For local Midamble code P point plural number and the IQ two paths of data of inverse, DC _IAnd DC _QBe respectively the residual DC component of IQ two-way, and separate.Intercept the power of the following tap of thresholding and be $\mathrm{Power}=\underset{n=0,n\&NotEqual;n_r}{\overset{P-1}{\mathrm{\&Sigma;}}}{\left|{{\underset{\&OverBar;}{H}}^{\&prime;}}_{\mathrm{raw}}\left(n\right)\right|}^2,$ That is:

$\mathrm{Power}=\underset{n=0,n\&NotEqual;n_r}{\overset{P-1}{\mathrm{\&Sigma;}}}{\left((H_{\mathrm{raw}\_I}\left(n\right)-{\mathrm{DC}}_I{E}_{\mathrm{mid}\_I}+{\mathrm{DC}}_Q{E}_{\mathrm{mid}\_Q})\right)}^2+(H_{\mathrm{raw}\_Q}\left(n\right)-{\mathrm{DC}}_I{E}_{\mathrm{mid}\_Q}-{\mathrm{DC}}_Q{E}_{\mathrm{mid}\_I}{\left)\right)}^2)$

$={\mathrm{<figure-callout\; id="1"\; label="coef"\; filenames="HDA0000103393630000011.png,HDA0000103393630000013.png"\; state="\{\{state\}\}">coef</figure-callout>}}_1{\mathrm{DC}}_I^2+{\mathrm{<figure-callout\; id="2"\; label="cofe"\; filenames="HDA0000103393630000021.png,HDA0000103393630000023.png"\; state="\{\{state\}\}">cofe</figure-callout>}}_2{\mathrm{DC}}_I+{\mathrm{coef}}_3{\mathrm{<figure-callout\; id="2"\; label="DC\; Q"\; filenames="HDA0000103393630000021.png,HDA0000103393630000023.png"\; state="\{\{state\}\}">DC</figure-callout>}}_Q^{}<figure-callout\; id="4"\; label="+\; coef"\; filenames="HDA0000103393630000013.png,HDA0000103393630000021.png"\; state="\{\{state\}\}">+</figure-callout>{\mathrm{coef}}_{}{}_4{\mathrm{DC}}_Q+{\mathrm{coef}}_5---\left(10\right)$

Wherein $\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="coef"\; filenames="HDA0000103393630000011.png,HDA0000103393630000013.png"\; state="\{\{state\}\}">coef</figure-callout>}}_1={\mathrm{<figure-callout\; id="3"\; label="coef"\; filenames="HDA0000103393630000021.png,HDA0000103393630000023.png"\; state="\{\{state\}\}">coef</figure-callout>}}_3=(N-w)(E_{\mathrm{mid}\_I}^2+E_{\mathrm{mid}\_Q}^2)\\ {\mathrm{cofe}}_2=-2\underset{n=0,n\&NotEqual;n_r}{\overset{P-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_I}\left(n\right)E_{\mathrm{mid}\_I}+H_{\mathrm{raw}\_Q}\left(n\right)E_{\mathrm{mid}\_Q})\\ {\mathrm{<figure-callout\; id="4"\; label="cofe"\; filenames="HDA0000103393630000013.png,HDA0000103393630000021.png"\; state="\{\{state\}\}">cofe</figure-callout>}}_4=-2\underset{n=0,n\&NotEqual;n_r}{\overset{P-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_Q}\left(n\right)E_{\mathrm{mid}\_I}-H_{\mathrm{raw}\_I}\left(n\right)E_{\mathrm{mid}\_Q})\\ {\mathrm{<figure-callout\; id="5"\; label="coef"\; filenames="HDA0000103393630000021.png,HDA0000103393630000023.png"\; state="\{\{state\}\}">coef</figure-callout>}}_5=\underset{n=0,n\&NotEqual;n_r}{\overset{P-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_I}^2\left(n\right)+H_{\mathrm{raw}\_Q}^2\left(n\right))\end{array}\right.$

Because coef ₁=coef ₃＞0, and DC _IAnd DC _QIndependent mutually, therefore (10) formula obtains the condition of minimum value be

And

Namely (10) formula is respectively for variables D C _IAnd DC _QThe single order partial derivative be 0, can try to achieve thus

$\left\{\begin{array}{c}{\mathrm{DC}}_I=\frac{\underset{n=0,n\&NotEqual;n_r}{\overset{N-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_I}\left(n\right)E_{\mathrm{mid}\_I}+H_{\mathrm{raw}\_Q}\left(n\right)E_{\mathrm{mid}\_Q})}{(N-w)(E_{\mathrm{mid}\_I}^2+E_{\mathrm{mid}\_Q}^2)}\\ {\mathrm{DC}}_Q=\frac{\underset{n=0,n\&NotEqual;r}{\overset{N-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_Q}\left(n\right)E_{\mathrm{mid}\_I}-H_{\mathrm{raw}\_I}\left(n\right)E_{\mathrm{mid}\_Q})}{(N-w)(E_{\mathrm{mid}\_I}^2+E_{\mathrm{mid}\_Q}^2)}\end{array}\right.---\left(11\right)$

This namely adopts when of the present invention, the residual direct current of IQ two paths of signals that the estimates component that disappears.Data result after the final direct current of whole time slot is eliminated is e"= e'- DC _N, wherein DC _N=( DC, DC, K DC) _N, jointly described by (9) formula and (11) formula.

Confirm by experiment, this scheme has effectively been eliminated the indelible DC component of averaging method, and for being configured to the descending SF=16 data of the time slot format of 16 code channels altogether, the SNR in joint-detection (signal to noise ratio) measurement result has obviously to be carried.Especially for the high-speed downlink packet access HSDPA business based on CQI (channel quality indication) mechanism, network all indicates to feed back by CQI for the resource distribution of terminal, under equal physics resource distribution, the SNR measured value is larger, the CQI value of feedback is larger, network is fuller for the scheduling of resource of terminal, and under constant decoding stability, the performance of throughput is higher.

Simultaneously, the signal constellation (in digital modulation) figure that the lifting of SNR more can make joint-detection go out is more concentrated, for the reliability of decode after joint-detection also getable lifting, further can improve system throughput.

The test simulation result:

Contain residual DC component receive data analogous diagram as shown in Figure 3, as can be seen from the figure, the symbol of this receive data afterbody finds out, also has residual direct current not eliminate clean.

Only adopt the joint detection results of the reception signal after the average direct current as shown in Fig. 4 figure, 5, wherein Fig. 4 is that averaging method is to the impulse response of channel, Fig. 5 is averaging method demodulation planisphere, wherein see from channel estimation results, tap power outside the main footpath that direct current causes is larger, and the demodulation planisphere is relatively dispersed.

After the direct current removing method that the employing embodiment of the present invention provides, joint detection results such as Fig. 6, shown in Figure 7 to same group of sample data, from channel estimation results, the power of the little tap that direct current causes obviously reduces, the demodulation planisphere is very concentrated, from SNR measurement result (referring to table 1), improved 11dB.

Table 1

	SNR(dB)
		Averaging method	17.1dB
The present invention	28.18dB

Disturb the SNR measurement result (referring to table 2) of more serious sample data based on direct current, referring to accompanying drawing 8, figure below is for being subjected to direct current to disturb 1000 groups of more serious sample datas to verify in actual test environment.

Table 2

	Average SNR (dB)
		Averaging method	21.2dB
The present invention	28.5dB

From the result, the measurement result of same group of sample SNR is had clear improvement, the distribution of SNR is more concentrated, and average SNR has the performance gain of 7dB left and right.

HSDPA FRC simulation, wherein simulated conditions is as shown in table 3:

Table 3

Be not difficult to find out, simulated environment is the highest configuration of HSDPA under the 1.28M bandwidth, reaches as high as the Theoretical Rate of 2.8Mbps under this kind configuration, but the encoding rate under this kind configuration is up to 99%, coding gain is very little, wants to reach reasonable performance, and is quite high to the requirement of receive data.In such cases, the present invention can bring the gain on BLER (error block ratio) and throughput equally, the gain that the high energy of BLER brings 1.5dB, and throughput is the highest to be improved more than 10 times.As seen the present invention for the mis-behave that causes because of the direct current reason, has reasonable inhibitory action, can reduce the performance difference that brings because of the difference of different radio frequency receiver simultaneously.

The embodiment of the present invention also provides a kind of direct current cancellation element, comprising:

Whole time slot average direct current cancellation element 1101 is used for eliminating utilize averaging method to carry out direct current through the receive data after analog-to-digital conversion;

Channel estimating apparatus 1102 is used for described receive data is carried out the original channel algorithm for estimating, calculates the coefficient of each tap after channel estimating;

Residual direct current estimation unit 1103 is used for realization to the best estimate of residual direct current;

Residual direct current cancellation element 1104 is used for realization the residual DC that described residual direct current estimation unit 1103 estimates is eliminated from described receive data.

In another one embodiment of the present invention, described whole time slot average direct current cancellation element 1101, concrete being used in each time slot of described receive data, with the average of the whole time slot IQ two paths of signals DC component as this time slot, the DC component that the IQ two paths of signals deducts is respectively separately eliminated direct current.

In another one embodiment of the present invention, described residual direct current estimation unit 1103, concrete be used for calculating lower than the power of all taps of described thresholding and minimum value; According to the power of described all taps and minimum value calculate the size of described residual direct current.

The direct current cancellation element that the embodiment of the present invention provides, be with previous embodiment in the direct current removing method fully corresponding, abridged part in the present embodiment, can reference method embodiment part despise.It is more than better execution mode of the embodiment of the present invention, anyone is under the prerequisite of skilled, do not deviate from spirit of the present invention and do not exceeding under the prerequisite of the technical scope that the present invention relates to, can do various replenishing and modification to the details that the present invention describes.Protection scope of the present invention is not limited to the cited scope of embodiment, and protection scope of the present invention is as the criterion with claim.

Claims (7)

1. a direct current removing method, is characterized in that, comprising:

Eliminate utilize averaging method to carry out direct current through the receive data after analog-to-digital conversion;

The rear 128 chip data of described receive data training sequence Midamble code part are done original channel estimate, calculate the coefficient of each tap after channel estimating;

According to original estimation result, choose power and do residual direct current Processing for removing less than the tap of setting thresholding.

2. direct current removing method according to claim 1, is characterized in that, and is described to utilize averaging method to carry out the direct current elimination through the receive data after analog-to-digital conversion, comprising:

In described receive data in each time slot, with the average of the whole time slot inphase/orthogonal component IQ two paths of signals DC component as this time slot, the DC component that the IQ two paths of signals deducts is respectively separately eliminated direct current.

3. direct current removing method according to claim 1, is characterized in that, and is described according to original estimation result, chooses power and does residual direct current Processing for removing less than the tap of setting thresholding, comprising:

Calculating lower than the power of all taps of described thresholding and minimum value;

According to the power of described all taps and minimum value calculate the size of described residual direct current;

Carrying out direct current according to the size of described residual direct current eliminates.

4. direct current removing method according to claim 3, is characterized in that, described according to described all taps power and minimum value calculate the size of described residual direct current, comprising:

$\left\{\begin{array}{c}{\mathrm{DC}}_I=\frac{\underset{n=0,n\&NotEqual;n_r}{\overset{N-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_I}\left(n\right)E_{\mathrm{mid}\_I}+H_{\mathrm{raw}\_Q}\left(n\right)E_{\mathrm{mid}\_Q})}{(N-w)(E_{\mathrm{mid}\_I}^2+E_{\mathrm{mid}\_Q}^2)}\\ {\mathrm{DC}}_Q=\frac{\underset{n=0,n\&NotEqual;r}{\overset{N-1}{\mathrm{\&Sigma;}}}(H_{\mathrm{raw}\_Q}\left(n\right)E_{\mathrm{mid}\_I}-H_{\mathrm{raw}\_I}\left(n\right)E_{\mathrm{mid}\_Q})}{(N-w)(E_{\mathrm{mid}\_I}^2+E_{\mathrm{mid}\_Q}^2)}\end{array}\right.$

H wherein _{Raw_I}(n) and H _{Raw_Q}(n) be respectively the IQ two paths of data that original channel is estimated, E _{Mid_I}And E _{Mid_Q}For local Midamble code P point plural number and the IQ two paths of data of inverse, DC _IAnd DC _QBe respectively the residual DC component of IQ two-way.

5. a direct current cancellation element, is characterized in that, comprising:

Whole time slot average direct current cancellation element is used for eliminating utilize averaging method to carry out direct current through the receive data after analog-to-digital conversion;

Channel estimating apparatus is used for described receive data is carried out the original channel algorithm for estimating, calculates the coefficient of each tap after channel estimating;

Residual direct current estimation unit is used for realization to the best estimate of residual direct current;

Residual direct current cancellation element is used for realization the residual DC that described residual direct current estimation unit estimates is eliminated from described receive data.

6. device according to claim 5, is characterized in that,

Described whole time slot average direct current cancellation element, concrete being used in each time slot of described receive data, with the average of the whole time slot inphase/orthogonal component IQ two paths of signals DC component as this time slot, the DC component that the IQ two paths of signals deducts is respectively separately eliminated direct current.

7. device according to claim 5, is characterized in that,

Described residual direct current estimation unit, concrete be used for calculating lower than the power of all taps of described thresholding and minimum value; According to the power of described all taps and minimum value calculate the size of described residual direct current.

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