KR100995136B1 - Apparatus for correcting DC offset - Google Patents

Abstract

A DC component correction device is provided. The DC component correcting apparatus includes a first correction unit for correcting a DC component from a received signal based on an initial value, outputting a first correction signal, an ADC for analog-to-digital converting the first correction signal, and synchronization information. A DC component estimator for generating a reference signal, extracting the residual DC component of the first correction signal from the converted first correction signal and the reference signal output from the ADC, and converting the first DC component based on the extracted residual DC component And a second correction unit for correcting the DC component from the correction signal.

DC offset, direct current component

Description

DC component correction device {Apparatus for correcting DC offset}

The present invention relates to a DC component correcting apparatus, and more particularly, to a DC component correcting apparatus capable of estimating and removing a DC component from a received signal at a receiver.

A receiver used in a wireless communication system basically performs an operation of down-converting an RF signal received at a high frequency to baseband. In this process, the received signal passes through a plurality of circuits such as a mixer, an amplifier, and the like, and the distortion of the signal due to mismatch and / or signal leakage occurring in each of the circuits. Phenomenon occurs.

Typical distortion of the received signal is a DC offset. The DC offset is a phenomenon in which a DC component is added to a received signal, and may be generated by, for example, self-mixing between received signals or re-inflow of a leaked local oscillator signal. This DC offset changes the level of the received signal to distort the received signal.

Conventionally, a method of estimating a DC offset based on an average value of a received signal and removing the estimated DC offset from the received signal has been used to remove the above-described DC offset.

However, since the conventional DC offset removing method removes all the DC components of the received signal, loss of the received signal, for example, when the data signal is included in the DC component of the received signal, may cause loss of the data signal.

The problem to be solved by the present invention is to provide a DC component correction device that can remove only the DC component of the received signal without data loss.

The DC component correcting apparatus according to an embodiment of the present invention for solving the above technical problem, the first correction unit for correcting the DC component from the received signal based on the initial value, and outputs the first correction signal, the synchronization information A first signal is generated based on the first signal, a channel signal estimated from the first correction signal and a frequency offset value are mixed with the first signal to generate a reference signal, and the first signal is generated from the first correction signal and the reference signal. A DC component estimator for extracting the residual DC component of the correction signal and a second correction unit for correcting the residual DC component of the first correction signal based on the extracted residual DC component.

The DC component estimator may include a signal generator configured to receive the synchronization information and output the first signal, a channel estimator configured to estimate the channel value based on the first correction signal, and based on the first correction signal. A frequency offset estimator for estimating a frequency offset value, a first mixer for mixing the first signal and the channel value to output a second signal, and a second signal for mixing the second signal and the frequency offset value to output a reference signal And a direct current component extraction unit configured to extract the residual direct current component by subtracting the reference signal from the mixer and the first correction signal.

The DC component estimating unit further includes an accumulating unit which accumulates and averages the extracted residual DC component for a predetermined time.

In the DC component correcting apparatus according to the present invention, the DC component of the received signal is firstly corrected, the residual DC component is estimated from the first corrected signal, and the DC component is secondly corrected to thereby correct the DC component of the received signal. Even when included, the quality of the received signal is preserved, and only the DC component of the received signal can be removed without losing data components.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the embodiments of the present invention, reference should be made to the accompanying drawings that illustrate embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a DC component correcting apparatus according to an exemplary embodiment of the present invention, and FIG. 2 is a block diagram of the DC component estimating unit illustrated in FIG. 1.

Referring to FIG. 1, a DC component correcting apparatus 100 according to an exemplary embodiment of the present invention may include a first corrector 110, an analog-digital converter (ADC) 120, a DC component estimator 130, and a second beam. It may include the government 140. The DC component correcting apparatus 100 according to the embodiment of the present invention may be used in a receiver of a wireless communication system, for example, an OFDm receiver.

The DC component correcting apparatus 100 is a signal Y from which a DC component has been removed by correcting a DC component of a signal received by an external receiver, for example, a receiver (not shown) received by the receiver. You can output

For example, the reception signal Y0 may be represented as shown in [Equation 1].

[Equation 1]

Where Nused is the number of subcarriers used, k is the index of the subcarrier, hk is the channel value, Ck is the data of each subcarrier, Δf is the frequency interval of each subcarrier, fc is the frequency offset value, and DC is the direct current component. It may mean. For example, DC can also be expressed as the sum of the in-phase and quadrature values of the DC offset.

The received signal Y0 may be input to the first corrector 110 of the DC component corrector 100. The first corrector 110 may first correct the received signal Y0 based on the initial value CNT, and output the first corrected signal Y1 as shown in Equation 2 below.

&Quot; (2) "

Where Nused is the number of subcarriers used, k is the index of the subcarrier, hk is the channel value, Ck is the data of each subcarrier, Δf is the frequency interval of each subcarrier, Δfc is the frequency offset value, and DC 'remains. It may mean a direct current component.

The first corrector 110 may include at least one of a preset tuning value, a correction value derived based on the average of the received signal Y0, or a DC component correction value provided from the DC component estimator 130 to be described later. Using the value of as an initial value CNT, the received signal Y0 may be firstly corrected and the first correction signal Y1 may be output.

The first correction signal Y1 may be input to an analog digital converter (ADC) 120, and the ADC 120 may analog-digital convert the first correction signal Y1 to perform a second correction signal ( Y2) can be output. The second correction signal Y2 is a signal obtained by converting the first correction signal Y1, and may be represented by Equation 3 to be the same as the first correction signal Y1.

&Quot; (3) "

Where Nused is the number of subcarriers used, hk is the channel value, Ck is the data of each subcarrier, Δf is the frequency interval of each subcarrier, Δfc is the frequency offset value, and DC 'is the residual DC component. Can be.

The second correction signal Y2 may be input to the DC component estimator 130, and the DC component estimator 130 may extract residual DC components ΔD1 and ΔD2 from the second correction signal Y2. Can be. The residual DC components ΔD1 and ΔD2 extracted from the DC component estimator 130 may be provided to the second corrector 140.

The DC component estimator 130 may receive synchronization information SI, for example, the same synchronization information SI as that of the reception signal Y0 from the outside, and according to the synchronization information SI, the second correction signal ( The residual direct current components DELTA D1 and DELTA D2 can be extracted from Y2).

Referring to FIG. 2, the DC component estimator 130 includes a signal generator 131, a channel estimator 132, an IFFT unit 133, a frequency offset estimator 134, a DC component extractor 135, and An accumulator 136 may be included.

The signal generator 131 may generate the first signal S1 substantially synchronized with the received signal Y0 based on the synchronization information SI input from the outside. In other words, the signal generator 131 may be a signal that is substantially the same as an output signal output from the transmitter based on the synchronization information SI, for example, a first signal in which no distortion such as a channel value, a frequency offset, a DC component, or the like is generated. (S1) can be generated. The first signal S1 may be represented by Equation 4 below.

&Quot; (4) "

Here, Nused may be the number of subcarriers used, k may be an index of subcarriers, Ck 'may be data of subcarriers of each first signal, and Δf may mean a frequency interval of each subcarrier.

The signal generator 131 may have a configuration substantially the same as, for example, a signal generator (not shown) of the transmitter.

The channel estimator 132 may estimate the channel value hk 'from the second correction signal Y2, and the estimated channel value hk' is obtained by the first mixer 137 by the first signal S1. Can be mixed with.

In detail, the channel estimator 132 may estimate the channel value hk 'from the second correction signal Y2 output from the ADC 120. The estimated channel value hk 'may be mixed with the first signal S1 by the first mixer 137, and the first mixer 137 may output the mixed signal, for example, the second signal S2. Can be. The second signal S2 may be represented by Equation 5 below.

[Equation 5]

Here, Nused may be the number of subcarriers used, k may be an index of subcarriers, hk 'may be an estimated channel value, Ck' may be data of subcarriers of each first signal, and Δf may mean a frequency interval of each subcarrier. .

The IFFT unit 133 may output a third signal S3 by performing an inverse fast fourier transform (IFFT) on the second signal S2 output from the first mixer 137. For example, the first signal S1 generated by the signal generator 131 of the receiver may be a signal in a frequency domain. In practice, however, an OFDM receiver can receive signals in the time domain from the transmitter. Therefore, in the present invention, the estimated channel value hk 'may be mixed with a signal in the frequency domain, that is, the first signal S1, and IFFT may be converted into a signal in the time domain. The IFFT unit 133 may be omitted depending on the type of the receiver.

The frequency offset estimator 134 may estimate the frequency offset value Δfc ′ from the second correction signal Y2, and the estimated frequency offset value Δfc ′ may be calculated by the second mixer 138. It can be mixed with three signals S3.

In detail, the frequency offset estimator 134 may estimate the frequency offset value? Fc 'from the second correction signal Y2 output from the ADC 120. The estimated frequency offset value Δfc ′ may be mixed with the third signal S3 by the second mixer 138, and the second mixer 138 outputs the mixed signal, eg, the reference signal Sref. can do. The reference signal Sref may be expressed as shown in [Equation 6]. Here, the reference signal Sref may be the same signal except for the difference between the input signal of the first correction unit 110, that is, the difference between the received signal Y0 and the DC component.

[Equation 6]

Where Nused is the number of subcarriers used, k is the index of subcarriers, hk 'is the estimated channel value, Ck' is the data of each subcarrier of the first signal, Δf is the frequency interval of each subcarrier, and Δfc 'is It may mean an estimated frequency offset value.

The DC component extracting unit 135 may generate a residual DC component ΔD1 or ΔD2, for example, from the reference signal Sref output from the second mixer 138 and the second correction signal Y2 output from the ADC 120. The residual DC component? D1 or? D2 of the second correction signal Y2 can be extracted.

In detail, the DC component extractor 135 extracts a difference value between the reference signal Sref and the second correction signal Y2, for example, a value obtained by subtracting the reference signal Sref from the second correction signal Y2. The residual DC component? D1 or? D2 of the two correction signals Y1 can be extracted.

Here, the residual direct current component (ΔD1 or ΔD2) can be expressed as shown in [Equation 7].

[Equation 7]

Here, N may mean the number of used subcarriers, DC 'may mean a residual DC component.

At this time, if the result of the subtraction is a positive value, the DC component extractor 135 may extract the first residual DC component ΔD1, for example, a positive DC component. If the result of the subtraction is a negative value, the DC component extraction unit 135 may extract the second residual DC component ΔD2, for example, a negative DC component.

The extracted first residual DC component ΔD1 or the second residual DC component ΔD2 may be provided to the accumulator 136, and the accumulator 136 may provide the first residual DC component Δ for a predetermined time. D1) or the second residual direct current component ΔD2 may be accumulated, averaged, and output. The output first residual DC component ΔD1 or the second residual DC component ΔD2 may be provided to the second corrector 140.

In addition, the DC component estimator 130 may provide the first residual DC component ΔD1 or the second residual DC component ΔD2 to the first correction unit 110, and the first correction unit 110 may be provided. May finely adjust the initial value CNT from the first residual DC component ΔD1 or the second residual DC component ΔD2. The finely adjusted initial value CNT may be used as a first correction level for firstly correcting the received signal Y0 in the next frame operation of the first corrector 110.

The second corrector 140 may perform the residual direct current of the second correction signal Y2 based on the first residual DC component ΔD1 or the second residual DC component ΔD2 output from the DC component estimator 130. The component can be corrected.

For example, when the first residual DC component ΔD1 is output from the DC component estimation unit 130, the second correction unit 140 outputs the DC component of the received signal Y0 in the first correction unit 110. It can be determined that only a part is removed.

Accordingly, the second correction unit 140 performs a second correction that subtracts the first residual DC component? D1 output from the DC component estimator 130 from the second correction signal Y2 output from the ADC 120. In this case, all DC components of the received signal Y0 may be removed.

In addition, when the second residual DC component ΔD2 is output from the DC component estimation unit 130, the second correction unit 140 removes the entire DC component of the received signal Y0 from the first correction unit 110. Therefore, it can be determined that the data component included in the DC component is lost.

Therefore, the second correction unit 140 performs a second correction that adds the second residual DC component ΔD2 output from the DC component estimator 130 to the second correction signal Y2 output from the ADC 120. The data component included in the DC component lost in the first correction of the received signal Y0 may be recovered.

That is, the second correction unit 140 adds or adds the first residual DC component ΔD1 or the second residual DC component ΔD2 output from the DC component estimation unit 130 to the second correction signal Y2. The second correction may be performed to subtract and output a signal Y from which only a DC component is removed from the received signal Y0.

Hereinafter, the operation of the above-described DC component correcting apparatus will be described in detail with reference to FIGS. 3 and 4. In the present embodiment, for convenience of description, FIGS. 3 and 4 will be described with reference to FIGS. 1 and 2.

3 is an operation flowchart of the DC component correcting apparatus of the present invention, and FIG. 4 is an operation section diagram of the DC component correcting apparatus of the present invention according to a viewpoint.

1 to 4, the received signal Y0 received by the receiver may be input to the first corrector 110 of the DC component corrector 100. Here, the received signal Y0 may be distorted in channel, frequency, and DC components by a plurality of circuits of the receiver, for example, an amplifier, a filter, and a mixer.

The first corrector 110 may first correct the received signal Y0 based on the initial value CNT (S10). The first corrector 110 may set at least one of a preset tuning value, a correction value derived based on an average of the received signal, or a DC component correction value extracted from the DC component estimator 130. By doing so, the received signal Y0 can be firstly corrected and the first corrected signal Y1 can be output.

On the other hand, the DC component correcting apparatus 100 receives the received signal Y0 by the operation of the first correcting unit 110 up to a point in time when the synchronization information SI is extracted from the received signal Y0, for example, the A point on the time axis t. Only the first order correction to remove the direct current component of

The ADC 120 may analog-digital convert the first correction signal Y1 output from the first correction unit 110 and output a second correction signal Y2. The second correction signal Y2 may be provided to the DC component estimator 130.

The DC component estimator 130 obtains the synchronization information SI at time A on the time axis t, generates a reference signal Sref based on the synchronization information SI, and generates the generated reference signal Sref. The residual DC component? D1 or? D2 of the second correction signal Y2 can be extracted from the step S20.

The DC component estimator 130 may obtain the synchronization information SI from the received signal Y0. The synchronization information SI may be extracted in a preamble section of the received signal Y0.

The synchronization information SI is provided to the signal generator 131, and the signal generator 131 generates a first signal S1 substantially synchronized with the received signal Y0 based on the synchronization information SI. It may be (S21).

The channel estimator 132 may estimate the channel value hk 'from the second correction signal Y2, and the estimated channel value hk' is obtained by the first mixer 137 by the first signal S1. Can be mixed with. The first mixer 137 may output the mixed second signal S2 (S22).

The second signal S2 may be IFFT-converted by the IFFT unit 133 and output as the third signal S3.

The frequency offset estimator 134 may estimate the frequency offset value? Fc 'from the second correction signal Y2, and the second mixer 138 may IFFT the estimated frequency offset value? Fc'. The reference signal Sref may be generated by mixing the second signal, that is, the third signal S3 (S23).

The DC component extractor 135 may extract the first residual DC component ΔD1 or the second residual DC component ΔD2 by subtracting the reference signal Sref from the second correction signal Y2 (S24). ). Here, as described above, the first residual DC component ΔD1 is a residual DC component having a positive value, and the second residual DC component ΔD2 has a residual DC component having a negative value. Can be.

In addition, the DC component estimator 130 adjusts the initial value CNT of the first correction unit 110 based on the extracted first residual DC component ΔD1 or the second residual DC component ΔD2. Can be adjusted (S40).

For example, the initial value CNT of the first compensator 110 finely adjusted at the time B on the time axis t may be used as the first correction level of the reception signal Y0 in the next frame operation of the receiver.

The second corrector 140 may perform the residual direct current of the second correction signal Y1 based on the first residual DC component ΔD1 or the second residual DC component ΔD2 extracted from the DC component estimation unit 130. The component may be second-corrected (S30).

For example, if the residual DC component extracted from the DC component estimator 130 is the first residual DC component ΔD1, the second correction unit 140 may direct-current the received signal Y0 from the first correction unit 110. It can be determined that only some of the components have been removed. In addition, a second correction may be performed to remove the remaining DC component by subtracting the first residual DC component ΔD1 from the second correction signal Y2.

In addition, the second corrector 140 may generate a direct current of the received signal Y0 from the first corrector 110 when the residual DC component extracted from the DC component estimator 130 is the second residual DC component ΔD2. It may be determined that all of the components, such as all of the direct current components including some data components, are removed. Second-order correction may be performed to recover the lost data component by adding the absolute value of the second residual direct current component ΔD2 from the second correction signal Y1.

As a result, the second correction unit 140 may correct only the DC component from the received signal Y0, and at the same time prevent loss of data components of the received signal Y0, thereby preserving the quality of the received signal Y0. can do.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.

1 is a block diagram of a DC component correction device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a DC component estimator shown in FIG. 1.

3 is an operation flowchart of the DC component correcting apparatus of the present invention.

4 is an operation interval diagram of the DC component correcting apparatus of the present invention according to a viewpoint.

Claims (9)

A first corrector configured to correct a DC component from a received signal based on an initial value and output a first corrected signal; A first signal is generated based on the synchronization information, and a reference signal is generated by mixing the channel value estimated from the first correction signal and the frequency offset value with the first signal, and from the first correction signal and the reference signal. A DC component estimator for extracting a residual DC component of the first correction signal; And And a second correction unit for correcting the residual DC component of the first correction signal based on the extracted residual DC component. The method of claim 1, wherein the DC component estimator, A signal generator which receives the synchronization information and outputs the first signal; A channel estimator estimating the channel value based on the first correction signal; A frequency offset estimator for estimating the frequency offset value based on the first correction signal; A first mixer for mixing the first signal and the channel value to output a second signal; A second mixer for mixing the second signal and the frequency offset value to output a reference signal; And And a DC component extracting unit configured to extract the residual DC component by subtracting the reference signal from the first correction signal. The method of claim 1, The DC component estimator further includes an accumulator configured to accumulate and average the extracted residual DC component for a predetermined time. The method of claim 1, And the first signal is the same signal as the signal output from the transmitter. The method of claim 1, The first correction unit outputs a first correction signal from which the entirety of the DC component including some data components is removed from the received signal. And the second corrector corrects the data component removed from the first correction signal based on the residual direct current component. The method of claim 1, The first correction unit outputs a first correction signal from which a part of the DC component is removed from the received signal. And the second correcting unit corrects the remaining DC components of the first correction signal based on the residual DC components. The method of claim 1, And the synchronization information is extracted from a preamble section of the received signal. The method of claim 1, And the DC component estimating unit finely adjusts the initial value based on the residual DC component. The method of claim 8, And the first corrector adjusts a correction level of a next frame based on the finely adjusted initial value.

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