KR20120009822A - Equalizer, receiver using the same, and method of equalizing - Google Patents

Abstract

PURPOSE: An equalizer, a receiver using the same, and an equalizing method are provided to produce a cumulative density function and an I histogram using a comparator instead of an analog-to-digital converter. CONSTITUTION: A channel equalizer(10) comprises an equalizing filter part(100), and a digital control part(200). The equalizing filter part is applied with input signals received through a transmission channel and produces equalization signals based on filter code signals. The equalizing filter part successively produces equalization signal patterns by delaying equalization signals. The digital control part produces I histogram based on input signals and equalization signal patterns to calculate the transfer function of a transmission channel. The digital control part produces filter code signals reflected with the transfer characteristic of the transmission channel based on I histogram.

Description

Equalizer, receiver using the same, and method of equalizing}

The present invention relates to data transmission and reception, and more particularly, to a channel equalizer using an eye histogram, a receiver, and an equalization method using the same.

During high-speed data communication, while the digital signal is transmitted at high speed with limited bandwidth through a communication channel such as a circuit board, a wireless communication channel, an optical fiber or a cable, the waveform of the data is greatly affected by the waveforms of adjacent symbols. appear. This phenomenon is called inter-symbol interference, and energy of one symbol may interfere with neighboring symbols, thereby degrading communication performance. In particular, this phenomenon is exacerbated when the transmission speed is increased and the interval between symbols is shortened, which is one of the causes of limiting the transmission speed in high-speed data communication.

A channel equalization filter may be used to compensate for performance degradation due to intersymbol interference to efficiently utilize the bandwidth of the channel. The channel equalization filter can be applied to an intermediate frequency and a baseband, in which a frequency-domain equalizer (FDE) is mainly used, and a time-domain equalizer is mainly used in the baseband. (TDE; Time-domain Equalizer) is used. The time domain equalizer is a channel equalization filter in the form of an adaptive equalization filter that provides adaptive channel compensation by applying variable filter characteristics even when an environmental change such as a channel characteristic or a change in temperature or power supply voltage occurs. Can be designed. In such an adaptive equalization filter, an equalizer adaptation algorithm that automatically controls the characteristics of the filter in a transmitting and receiving end during a communication process is important.

One object of the present invention for solving the above problems is to provide a channel equalizer for reducing symbol interference of data received through a transmission channel.

Another object of the present invention is to provide a receiver which reduces symbol interference of data received via a transmission channel.

It is still another object of the present invention to provide a channel equalization method for reducing symbol interference of data received through a transmission channel.

In order to achieve the above object of the present invention, a channel equalizer according to an embodiment of the present invention includes an equalization filter unit and a digital control unit. The equalization filter unit receives an input signal received through a transmission channel to generate an equalization signal based on a filter code signal, and sequentially delays the equalization signal to sequentially generate an equalization signal pattern. The digital control unit generates an eye histogram based on the input signal and the equalized signal pattern to calculate a transfer function of the transmission channel, and the filter code signal reflecting the transfer characteristic of the transmission channel based on the eye histogram. Produce it and provide it to the equalization filter unit.

The equalization filter unit may include a feedforward filter and a feedback filter. The feedforward filter may filter and provide the input signal based on a feedforward filter code. The feedback filter may generate the equalization signal based on the filter code and the output signal of the feedforward filter, and sequentially generate the equalization signal pattern by delaying the equalization signal sequentially.

The digital controller may include a comparator and a filter controller. The comparator may generate a comparison bit signal by comparing a level of the reference signal and the input signal. The filter controller may generate the eye histogram based on the comparison bit signal and the equalization signal pattern and generate the filter code signal based on the eye histogram.

The comparator may include a reference signal generation unit and a sample comparison unit. The reference signal generation unit may generate the reference signal based on the reference code signal. The sample comparison unit may generate the comparison bit signal by comparing the level of the reference signal and the input signal.

The filter controller may include an eye histogram generating unit and a filter code calculating unit. The eye histogram generating unit accumulates the value of the comparison bit signal corresponding to the level of the reference signal to generate the eye histogram including a reception level frequency distribution corresponding to each of the equalized signal combinations that the equalized signal pattern may have. Can be generated. The filter code calculating unit may generate the filter code signal based on the highest frequency reception level corresponding to each of the equalized signal combinations detected from the eye histogram.

The eye histogram generating unit may include a counter, a cumulative histogram generating unit, and a histogram generating unit. The counter may calculate the level reception frequency corresponding to the level of the reference signal by counting the comparison bit signal based on the equal sign signal pattern. The cumulative histogram generation unit may generate a cumulative histogram based on the level reception frequency corresponding to the level of the reference signal. The histogram generating unit may generate the eye histogram by differentiating the cumulative histogram.

The filter code calculating unit calculates an eye pattern opening degree based on the eye histogram, and when the eye pattern opening degree is larger than a threshold value, calculates a feedback filter coefficient based on the eye histogram, and calculates the feedback filter coefficient. A feedback filter code of the filter code signal is generated and provided to the feedback filter of the equalization filter unit, and when the eye pattern opening degree is less than or equal to the threshold value, a feedforward filter code of the filter code signal is generated to generate the equalization filter code. The filter unit may be provided to the feedforward filter.

The digital controller may be configured to determine a frequency reception level for some combinations of the equalized signal combinations of the equalized signal pattern without performing analog-to-digital conversion on the input signal. The eye histogram may be generated by comparing the input signal with a reference signal to find. The some combinations may be combinations for calculating filter coefficients of the equalization filter part.

The number of levels of the reference signal may be greater than the number of possible combinations of the equalization signal patterns, and the number of some of the combinations of the equalization signals may be the minimum number necessary to calculate the filter coefficients of the equalization filter unit. .

In order to achieve one object of the present invention, a receiver according to an embodiment of the present invention includes a demodulator, a channel equalizer and a decoder. The demodulator demodulates the data received via the transmission channel into a baseband signal on a carrier frequency. The channel equalizer generates an equalization signal reflecting characteristics of a channel based on an eye histogram of the reception level of the baseband signal to reduce intersymbol interference of the baseband signal. The decoder decodes the equalized signal to restore transmission data. The channel equalizer includes an equalization filter unit and a digital control unit. The equalization filter unit receives the baseband signal to generate the equalization signal based on a filter code signal, and delays the equalization signal to sequentially generate an equalization signal pattern. The digital controller generates the eye histogram based on the equalized signal and the equalized signal pattern, and calculates the transfer function of the transmission channel based on the eye histogram to calculate a transfer function of the transport channel. A signal is generated and provided to the equalization filter unit.

In order to achieve the object of the present invention, in the channel equalization method according to an embodiment of the present invention, the input signal received through the transmission channel is applied to sequentially generate an equalization signal based on a filter code signal, the equalization The signal is delayed to generate an equalized signal pattern, an eye histogram is generated based on the input signal and the equalized signal pattern, and the filter code signal reflecting a transmission characteristic of the transmission channel is generated based on the eye histogram.

In generating the filter code signal, an eye pattern opening degree is calculated based on the eye histogram, and when the eye pattern opening degree is larger than a threshold value, a feedback filter coefficient is calculated based on the eye histogram, and the feedback is generated. A feedback filter code of the filter code signal is generated based on a filter coefficient and provided to a feedback filter of an equalization filter unit. When the eye pattern opening degree is less than or equal to the threshold value, a feedforward filter code of the filter code signal is generated. The feed forward filter may be provided to the equalization filter unit.

The channel equalizer, the receiver and the channel equalization method according to the embodiments of the present invention calculate the coefficients of the equalization filters included in the equalization filter unit based on the histogram of the reception level of the data symbols. Comparators are used instead of analog-to-digital converters to generate cumulative density functions and eye histograms of the equalized signal, thereby reducing the complexity and power consumption of the equalizer.

In addition, the channel equalizer, the receiver and the channel equalization method according to the embodiments of the present invention include on-chip EYE monitoring in the process of performing equalization, and thus, whether the child is opened or closed can be determined. The operating condition of the decision feedback filter can be calculated without a pilot sequence even in the closed initial state.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art without departing from the spirit and scope of the present invention.

1 is a block diagram illustrating a channel equalizer according to embodiments of the present invention.
FIG. 2 is a block diagram illustrating an example of an equalization filter unit included in the channel equalizer of FIG. 1.
3 is a block diagram illustrating an example of a feedback filter included in an equalization filter of FIG. 3.
4 is a block diagram illustrating an example of a feedforward filter included in the equalization filter of FIG. 2.
5 is a block diagram illustrating a comparator included in the channel equalizer of FIG. 1.
6 is a block diagram illustrating a filter controller included in the channel equalizer of FIG. 1.
FIG. 7 is a block diagram illustrating an eye histogram generating unit included in the filter controller of FIG. 6.
8 is a timing diagram illustrating a process of generating an eye histogram using the channel equalizer of FIG. 1.
9 is a diagram illustrating a process of obtaining an input highest frequency reception level according to each equalization signal pattern from an eye histogram.
10 is a block diagram illustrating a receiver according to embodiments of the present invention.
11 is a flowchart illustrating a channel equalization method according to embodiments of the present invention.
12 is a flowchart illustrating an example of generating the eye histogram of FIG. 11.
FIG. 13 is a flowchart illustrating an example of generating a filter code signal of FIG. 11.

With respect to the embodiments of the present invention disclosed in the text, specific structural to functional descriptions are merely illustrated for the purpose of describing embodiments of the present invention, embodiments of the present invention may be implemented in various forms and It should not be construed as limited to the embodiments described in.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for the components.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that another component may exist in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between. Other expressions describing the relationship between components, such as "between" and "immediately between," or "neighboring to," and "directly neighboring to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof that has been described, and that one or more of them is present. It is to be understood that it does not exclude in advance the possibility of the presence or addition of other features or numbers, steps, actions, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

On the other hand, when an embodiment is otherwise implemented, a function or operation specified in a specific block may occur out of the order specified in the flowchart. For example, two consecutive blocks may actually be performed substantially simultaneously, and the blocks may be performed upside down depending on the function or operation involved.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. The same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

1 is a block diagram illustrating a channel equalizer according to embodiments of the present invention.

Referring to FIG. 1, the channel equalizer 10 includes an equalization filter unit 100 and a digital control unit 200.

The equalization filter unit 100 receives an input signal I received through a transmission channel, generates an equalization signal EQ based on the filter code signals CF and CD, delays the equalization signal EQ, and equalizes the equalization signal. The signal pattern P is sequentially generated. The received input signal I may be a non-return-to-zero (NRZ) signal. When the equalization filter unit 100 is utilized in a receiver or a communication system, the received input signal I may be, for example, a carrier frequency band or an intermediate frequency by a demodulator, as described below with reference to FIG. 10. The signal may be a baseband signal demodulated from an Intermediate Frequency band to a baseband.

The digital controller 200 generates an eye histogram based on an input signal I and an equalized signal pattern P, and calculates a transfer characteristic of the transmission channel based on the eye histogram, in order to calculate a transfer function of the transmission channel. The reflected filter code signals CF and CD are generated and provided to the equalization filter unit 100.

The digital control unit 200 does not perform an analog-to-digital conversion on the input signal I, but most frequencies of some combinations of the equalization signal EQ that the equalization signal pattern P may have. The eye histogram HG may be generated by comparing the input signal I with the reference signal VREF to find the reception level. The some combinations may be combinations for calculating filter coefficients of the equalization filter unit 100.

The number of levels of the reference signal is greater than the number of possible combinations of the equalization signal pattern P, and the number of the some combinations of the combinations of the equalization signals EQ is equal to the calculation of the filter coefficients of the equalization filter unit 100. May be the minimum number required.

The digital controller 200 may include a comparator 210 and a filter controller 250. The comparator 210 may generate a comparison bit signal DO by comparing the level of the reference signal and the input signal I. The filter controller 250 may generate the eye histogram based on the comparison bit signal DO and the equalization signal pattern P, and generate the filter code signals CD and CF based on the eye histogram.

FIG. 2 is a block diagram illustrating an example of an equalization filter unit included in the channel equalizer of FIG. 1.

Referring to FIG. 2, the equalization filter unit 100 may include a feedforward filter 110 and a feedback filter 150.

The feedforward filter 110 may filter and provide the input signal I based on the feedforward filter code CF. The feedforward filter 100 may be a linear filter, for example a transversal equalizer. Considering the ease of implementation and the complexity of the system, a shape of a tap delay line may be used as shown in FIG. 3. The number of filter taps may be m (m is an integer of 1 or more). The feed forward filter 110 may be an analog filter that performs filtering irrespective of a synchronous clock for receiving a high frequency signal, or may be a digital filter that operates in response to the synchronous clock.

The feedback filter 150 generates the equalization signal EQ based on the filter codes CF and CD and the output signal FO of the feedforward filter 100, and delays the equalization signal EQ so that the equalization signal pattern ( P) can be generated. The feedback filter 150 may be a decision feedback equalizer for reducing a post-cursor ISI of a channel by feeding back a result of determining a symbol with respect to the received signal I. In this case, when the symbol for the delayed input signal is generated to generate the delayed equalization signal, in determining the symbol of the input signal I, the ISI may be determined by the delayed equalization signal of the delayed input signal.

3 is a block diagram illustrating an example of a feedback filter included in an equalization filter of FIG. 2.

Referring to FIG. 3, the feedback filter 150 may include a determination unit 160, first to nth delay elements 171,..., 17n and first to nth multipliers 151,..., 15n. Can be. The first through n-th delay elements 171,..., 17n sequentially delay the equalization signal EQ generated by the determination unit 160 to equalize the signal pattern P; {P1,..., Pn}, that is, delayed. Equalization signals P1, ..., Pn are generated. The first to n-th multipliers 151,..., 15n are delayed equalization of the equalization signal patterns P; {P1, ..., Pn} generated by the first to nth delay elements 171, ..., 17n. Signals obtained by multiplying the signals P1, ..., Pn by the filter coefficient values CD1, ..., CDn of the feedback filter code CD {CD1, ..., CDn} may be provided to the determination unit 160, respectively. . The determination unit 160 adds or subtracts the signals provided from the first to nth multipliers 151,..., 15n to the output signal FO of the feedforward filter 110 applied from the feedforward filter 110, and The equalization signal EQ may be generated by performing a symbol determination operation having a nonlinear characteristic. This series of operations is performed in response to the synchronous clock CLK having the same frequency as the sampling frequency of the input signal. For example, the feedback filter 150 may generate an equalization signal EQ in response to a rising edge or a falling edge of the synchronization clock CLK.

4 is a block diagram illustrating an example of a feedforward filter included in the equalization filter of FIG. 2.

Referring to FIG. 4, the feedforward filter 110 may include an adder 120, first to n th delay elements 111,..., 11 n, and first to n th multipliers 131,..., 13n. have. The first to nth delay elements 111,..., And 11n may provide signals to the first to nth multipliers 131,..., 13n to which the input signal I is sequentially delayed. The first to n-th multipliers 131,..., 13n are feedforward filter coefficients of the signals delaying the input signal I sequentially and the feedforward code signal CF ({CF1,..., CFm}). Signals multiplied by CF1,..., CFm) may be provided to the adder 120. The adder 120 generates a signal obtained by adding the signals multiplied by the feedforward filter coefficients CF1,..., CFm as an output signal FO of the feedforward filter 110, and provides the feedback signal to the feedback filter 150. Can be. The series of operations may be performed in response to the synchronous clock CLK having the same frequency as the sampling frequency of the input signal, but may have a structure that is performed independently of the synchronous clock CLK. For example, when operating in response to the synchronization clock CLK, the feedback filter 150 generates an equalization signal EQ in response to a rising edge or a falling edge of the synchronization clock CLK. can do.

For convenience of description, the case in which the feedforward filter 110 is a transverse filter (Transversal Equalizer) as shown in FIG. 4 is illustrated and described. It may be a FSE (Fractionally Spaced Equalizer).

5 is a block diagram illustrating a comparator included in the channel equalizer of FIG. 1.

Referring to FIG. 5, the comparator 210 may include a reference signal generation unit 230 and a sample comparison unit 220.

The reference signal generation unit 230 may generate the reference signal VREF based on the reference code signal CV. The reference signal VREF serves as a reference for magnitude comparison to express the magnitude of the input signal I as one bit, and may be a reference for determining the rank of the eye histogram HG generated by the filter controller 250. . In some embodiments, the reference signal VREF may be a signal that changes in a relatively long period compared to the period of the input signal I. The reference signal generation unit 230 may receive the reference code signal CV, which is a digital signal or an analog signal, and output the reference signal VREF, which is an analog signal. Therefore, as will be described later, the sample comparison unit 220 receives the reference signal VREF from the reference signal generation unit 230, samples the sample signal, and compares the bits with the input signal I received through the transmission channel. Signal D0 can be generated.

The sample comparison unit 220 may generate the comparison bit signal DO by comparing the level of the reference signal VREF and the input signal I. That is, the sample comparison unit 220 does not analog-to-digital convert the input signal I, and compares only the magnitude of the reference signal VREF and the input signal I to a logic high level and logic. A comparison bit signal DO having only a low level (logic low) is output. Accordingly, the input signal I may be operated by receiving an input signal I having a higher frequency than the channel equalizer which obtains information on the reception level of the input signal I through analog-to-digital conversion.

This series of operations is performed in response to the synchronous clock CLK having the same frequency as the sampling frequency of the input signal. For example, the sample comparison unit 220 may generate an equalization signal EQ in response to a rising edge or a falling edge of the synchronization clock CLK.

6 is a block diagram illustrating a filter controller included in the channel equalizer of FIG. 1.

Referring to FIG. 6, the filter controller 250 may include an eye histogram generation unit 260 and a filter code calculation unit 270.

The eye histogram generating unit 260 accumulates the value of the comparison bit signal DO corresponding to the level of the reference signal VREF to receive level frequencies corresponding to each of the equalized signal combinations that the equalized signal pattern P may have. An eye histogram (HG) including the distribution can be generated. The eye histogram generation unit 260 generates a comparison bit signal DO corresponding to each reference signal VREF for each of the reference signals VREF greater than the number of information symbols that the input signal I may have. Cumulative frequency can be calculated cumulatively. For example, when the number of symbols that the input signal I can have is eight, the number of reference signals VREF or the number of levels of the reference signal VREF may be 24. However, since the number and range of the highest frequency reception levels required for calculating the impulse response or transfer function of the transmission channel can be specified, the eye histogram (HG) using only the reference signal VREF corresponding to the specific equalization signal pattern can be specified. You can also create In this case, the cumulative frequency of the reference signals except for the reference signal VREF corresponding to the specific equalization signal pattern among the reference signals VREF should be excluded when generating the eye histogram HG.

The comparison bit signal DO, which is a result of comparing the magnitude of the input signal I with the reference signal VREF whose level is determined according to the reference code signal CV, has a logic high level and a logic high level as described above. Only has logic low level. Therefore, when the comparison bit signal DO is logic high, that is, for example, when the input voltage is higher than the reference signal VREF, the comparison bit signal DO may have a signal level of, for example, 1V. . On the other hand, when the comparison bit signal DO is logic low, that is, for example, when the voltage of the input signal I is lower than the reference signal VREF, the comparison bit signal DO is, for example, 0V. It may have a signal level. By accumulating and counting the number of times the comparison bit signal DO corresponding to the current reference signal VREF is logic high, the cumulative frequency of the corresponding reference signal VREF may be obtained. According to an embodiment, when the voltage of the input signal I is lower than the reference signal VREF, the comparison bit signal DO may have the logic high level, and the voltage of the input signal I is the reference signal VREF. ), The comparison bit signal DO may have the logic low level. In addition, the voltage values of the comparison bit signal DO corresponding to the logic high and the logic low are exemplary, and may have different values that can be determined according to embodiments.

The reference code signal CV may be provided by the channel parameter calculation unit 270 as described later or may be provided by an external control circuit. The reference code signal CV may be generated such that the level of the reference signal VREF generated according to the reference code signal CV increases by a unit level. The reference code signal CV may be generated according to the reference code signal CV. The level of the generated reference signal VREF may be reduced by the unit level.

After obtaining the cumulative frequency corresponding to each reference signal VREF, the eye histogram HG is differentiated based on a difference from the cumulative frequency corresponding to the reference signal VREF adjacent to each reference signal VREF. ).

The filter code calculation unit 270 may generate the filter code signals CD and CF based on the highest frequency reception level corresponding to each of the equalized signal combinations detected from the eye histogram HG. In addition, the reference code signal CV for generating the reference signal VREF applied to the sample comparison unit 220 may be further provided to the eye histogram generation unit 260.

The filter code calculation unit 270 may generate the feedback filter code CD to determine the degree of opening of the eye pattern based on the eye histogram HG so that the filter coefficients of the feedback filter 150 may converge. That is, the eye pattern opening degree is calculated based on the eye histogram HG, and when the eye pattern opening degree is larger than the threshold value, the feedback filter coefficient is calculated based on the eye histogram HG, and the feedback filter coefficient is added to the feedback filter coefficient. Based on the above, the feedback filter code CD of the filter code signals CF and CD or the filter code signals CF and CD may be generated and provided to the feedback filter 150 of the equalization filter unit 100. In this case, filter code signals CF and CD may be generated and provided to the equalization filter unit 100 according to the number of precursors and postcursors that are considered to reduce intersymbol interference, that is, the number of filter taps of each filter. Alternatively, only the feedback filter code CD of the filter code signals CF and CD may be generated and provided to the feedback filter 150 of the equalization filter unit 100. On the other hand, when the opening degree of the eye pattern is less than or equal to the threshold value, the feedforward filter code CF of the filter code signals CF and CD is generated and provided to the feedforward filter 110 of the equalization filter unit 100. The feed forward filter 110 may be adjusted to improve the degree of opening of the eye indicating the discrimination of the received signal.

FIG. 7 is a block diagram illustrating an eye histogram generating unit included in the filter controller of FIG. 6.

Referring to FIG. 7, the eye histogram generating unit 260 may include a counter 261, a cumulative histogram generating unit 263, and a histogram generating unit 265.

The counter 261 may calculate the level reception frequency corresponding to the level of the reference signal VREF by counting the comparison bit signal DO based on the equal sign signal pattern P. FIG. As such, by acquiring the level frequency corresponding to the level of each reference signal VREF, the reception level cumulative frequency distribution corresponding to each of the equalized signal combinations of the equalized signal pattern P may be obtained. As described below with reference to FIGS. 9 and 10, of the equalization signal combinations that an equalization signal pattern may have, a transmission corresponding to an impulse response of the transmission channel required to generate a filter code signal CD, CF This may be done for some of the equalized signal patterns sufficient to produce the coefficients of the function.

The cumulative histogram generating unit 263 may generate a cumulative histogram CHG based on the level reception frequency corresponding to the level of the reference signal VREF. Since the counter 261 is used to calculate the level reception frequency corresponding to the reference signal level VREF without using an analog-to-digital converter, the level reception frequency can be calculated for each rank of the cumulative histogram (CHG) without further calculation. Value, that is, the frequency for each reference signal level VREF.

The histogram generating unit 265 may generate the eye histogram HG by differentiating the cumulative histogram CHG. The level of the reference signal VREF may be determined such that the interval between levels of neighboring reference signals is constant so that a reception level cumulative frequency distribution corresponding to each of the equalization signal combinations that the equalization signal pattern P may have is obtained. . The eye histogram HG can be generated by deriving the cumulative histogram from the derivative, that is, the difference between the frequency for each reference signal VREF and the level reception frequency for an adjacent reference signal.

8 is a timing diagram illustrating a process of generating an eye histogram using the channel equalizer of FIG. 1.

Hereinafter, an eye histogram generation process will be described with reference to FIGS. 1, 5, 7, and 8. After the reference code signal CV is initialized to zero, the reference signal generation unit 230 of the comparator 210 may increase the reference signal VREF linearly or according to a predetermined rule as the reference code signal CV increases. Can be generated. The generated reference signal VREF is applied to the sample comparison unit 220. The sample comparison means 220 compares the magnitude of the input signal I and the reference signal VREF received through the transmission channel at the rising edge of the synchronization clock CLK in response to the synchronization clock CLK. As a result, the comparison bit signal DO, which is digital data having one bit, is provided. The counter 261 of the eye histogram generating unit 260 has a logic high level (in this case, the input signal I is greater than the reference signal VREF) as described above during the sample collection interval W. In this case, the number of outputs of logic high level) is accumulated and stored in the register. The digital controller 200 may generate the cumulative histogram CHG for each reference signal VREF by repeating the above process while increasing the reference code signal CV by a unit interval for each sample collection interval W. FIG. The eye histogram HG can be generated by calculating the cumulative histogram, that is, the difference between the frequency for each reference signal VREF and the frequency for an adjacent reference signal. As described with reference to FIG. 5, the reference signal VREF may have L levels, where L may be an integer greater than the number of symbols of the input signal I. FIG.

Referring again to FIGS. 3 and 4, the impulse response of the transport channel may be distributed to one cursor, m pre-cursors, and n post-cursors. Or when the size of the n + 1 th or more post cursors and the m + 1 th or more free cursors is negligible, the impulse response of the transport channel is one cursor, It may be distributed to m pre-cursors and n post-cursors. The input signal I received through the transmission channel with the impulse response is determined by performing convolution integration of the transmitted signal and the impulse response. That is, the magnitude of the inter-symbol interference of the received signal is determined by the received signal signal m, n interference components, and m and n symbol combinations before and after the symbol.

The equalization signal pattern is represented by the current cursor as shown in [Equation 1].

[Equation 1]

In Equation 1, PPi is a j-th combination of the equalization signal combinations of the equalization signal pattern, and is a matrix having a total of n + m + 1 elements. J is the number of combinations of equalization signals that the equalization signal pattern can have (J equals m + n + 1 square of 2 since the equalization signal pattern is equal to the number of m + n + 1 squares of two). , n is the number of post cursors, m is the number of free cursors. Here sk (k is an integer greater than -m and less than n) each represents a possible symbol of the input signal. For example, in the case of a non-return-to-zero (NRZ) signal, each sk may have a symbol value of -1 or 1.

When rj (j is an integer of 1 or more and J or less), which is the magnitude of the input signal I received through the transmission channel, is expressed as a matrix, Equation 2 below.

[Equation 2]

In Equation 2, ak (k is an integer greater than or equal to -m and less than n) is a coefficient of a transfer function corresponding to the precursor and the postcursor and represents an impulse response of a transport channel, and rj (j is An integer equal to or greater than 1 and equal to or less than J) corresponds to a substantial magnitude in the received input signal I.

Since the magnitude of the input signal I received through the transmission channel has the number of J branches due to intersymbol interference, it may have a J branch level in the center of the eye pattern. As such, since there is a magnitude of the input signal I that can be distinguished from other equalization signal patterns for a particular equalization signal pattern, calculating the coefficients ak of the transfer function representing the impulse response of the transmission channel is It is possible by calculating the magnitude of the input signal I for some equalized signal patterns other than the equalized signal pattern through the eye histogram HG. In other words, when the digital controller 200 receives the equalized signal pattern P from the equalized filter unit 100 and corresponds to an equalized signal pattern having a combination of specific equalized signals, the digital controller 200 will be described later with reference to FIG. 11. In addition, the eye histogram generation operation S300 may be performed.

Referring to FIGS. 7 and 8 again, the cumulative histogram CHG may include level values of reference signals corresponding to each of the equalized signal patterns P, that is, cumulative histogram rank values, a level reception cumulative frequency corresponding to each of them, That is, the cumulative histogram frequency values may be included. However, a method of generating an eye histogram HG may vary according to a method of accumulating the level reception cumulative frequency. The eye histogram HG may include level values of reference signals corresponding to each of the equalized signal patterns P, that is, eye histogram rank values, and level reception frequency corresponding to each of them, that is, eye histogram frequency values.

9 is a diagram illustrating a process of obtaining an input highest frequency reception level according to each equalization signal pattern from an eye histogram.

1 and 9, for convenience of description, when considering two post cursors to reduce intersymbol interference, that is, when n is 2 and J is 8, the corresponding impulse response of the transmission channel corresponds. A process of calculating the coefficients ak of the transfer function is described. When the input signal I received through the transmission channel has an eye pattern as shown on the left, some combination of the possible equalization signals PP1, ..., PPJ in the equalization signal pattern P Eye histograms are generated for the fields PP3, PP5, and PP6. In this case, the eye histogram for each of the combinations PP3, PP5, and PP6 of the equalization signals may be stored separately. It is possible to determine the class values r3, r5, r6 of the eye histogram corresponding to the maximum frequency for each of the combinations of equalization signals PP3, PP5, PP6, and the input received via the transmission channel as described above. The rank values r3, r5, r6 corresponding to the magnitude of the signal I are respectively the convolution of the coefficients ak of the transfer function of the transmission channel and the overlap sk of the symbols sk of the input signal I. Since, for example, when n is 2 and J is 8, the coefficients ak of the transfer function of the transmission channel can be calculated through Equation 3 below.

&Quot; (3) "

In Equation 3, r3, r5 and r6 are rank values of an eye histogram corresponding to the maximum frequency for each of the combinations of equalization signals PP3, PP5 and PP6, and a0, a1 and a2 are 2 Considering the number of post cursors, the coefficients of the transfer function of the transport channel.

In the above, for convenience of description, when considering two post cursors, that is, when n is 2 and J is 8, a process of calculating coefficients ak of a transfer function corresponding to an impulse response of the transport channel is described. However, in consideration of any m free cursors and any n post cursors, the coefficients ak of the transfer function corresponding to the impulse response of the transmission channel can be calculated in a similar manner.

10 is a block diagram illustrating a receiver according to embodiments of the present invention.

Referring to FIG. 10, the receiver 20 includes a demodulator 300, a channel equalizer 10, and a decoder 400.

The demodulator 300 demodulates the data received on the carrier frequency into a baseband signal on a carrier frequency. The channel equalizer 10 generates an equalization signal EQ reflecting the characteristics of the channel based on an eye histogram HG of the reception level of the baseband signal to reduce the intersymbol interference of the baseband signal. . However, since the channel equalizer 10 of FIG. 10 corresponds to the channel equalizer 10 of FIG. 1, redundant description thereof will be omitted. The decoder 400 restores the transmission data by decoding the equalization signal EQ.

The demodulator 300 includes Frequency-Shift Keying (FSK), Frequency-Shift Keying (FSK), Amplitude-Shift Keying (ASK), On-Off Keying (OOK), Phase-Shift Keying (PSK), and Quadrature Amplitude Modulation ), Minimum-Shift Keying (MSK), Continuous Phase Modulation (CPM), Pulse Code Modulation (PCM), Pulse Width Modulation (PWM), Pulse Amplitude Modulation (PAM), Pulse Density Modulation (PDM), Pulse Position Modulation ), Trellis Coded Modulation (TCM), Orthogonal Frequency Division Multiplexing (OFDM), Single Carrier FDMA (SC-FDE), Chip Spread Spectrum (CSS), Direct-Sequence Spread Spectrum (DSSS), Frequency Hopping Spread Spectrum (FHSS), The demodulator may demodulate signals modulated in at least one of modulation schemes including a time hopping spread spectrum (THSS).

The decoder 400 inserts structured redundancy into the input signal I transmitted through the transmission channel to detect bit error rate performance in the transmission channel environment having limited power or limited bandwidth. A coded signal may be decoded using a code or an error correction code. The decoder 400 may be a decoder that decodes signals encoded in at least one of a block code and a non-block code. According to an embodiment, the decoder 400 may decode the source coded signal in a lossless or lossy compression scheme as well as the channel coding as described above.

The decoder 400 includes a hamming code, a reed-solomon code, a viterbi code, a bose and ray-chaudhuri code, a turbo code, an LDPC. (Low-Density Parity-Check Codes), Constant-weight Code, Convolution Code, Group Codes, Golay Code, Goppa Code, Hadamard Code, Hagelbarger Code, LT Code ( Luby Transform Codes, Lexicographic Codes, Latin Square based Codes, Online Codes, Raptor Codes, Reed-Muller Codes, and Repeat-Accumulate The decoder may be a decoder for decoding signals encoded in at least one of error correction codes including a code, a repetition code, a tornado code, and the like.

In an embodiment, the receiver 20 may perform backward error correction, which provides an automatic repeat request (ARQ) for transmitting a retransmission signal to a transmitter when an error is detected in the decoder 400. . Alternatively, the receiver 20 may perform a hybrid automatic repeat request (HARQ) that performs forward error correction or ARQ according to the severity of the error.

The channel equalizer 10 includes an equalization filter unit 100 and a digital control unit 200. The equalization filter unit 100 receives the baseband signal to generate an equalization signal EQ based on the filter code signals CF and CD, delays the equalization signal EQ, and sequentially processes the equalization signal pattern P. To create. The digital controller 200 generates an eye histogram HG based on an equalization signal EQ and an equalization signal pattern P, and calculates an eye histogram HG based on the eye histogram HG in order to calculate a transfer function of the transmission channel. The filter code signal reflecting the transmission characteristics of the transmission channel is generated and provided to the equalization filter unit 100. Since the channel equalizer 10 of FIG. 10 is similar to the channel equalizer 10 of FIG. 1, redundant description thereof will be omitted.

11 is a flowchart illustrating a channel equalization method according to embodiments of the present invention.

1 and 11, in a channel equalization method according to an embodiment of the present invention, an equalization signal EQ is sequentially received based on a filter code signal by receiving an input signal I received through a transmission channel. Generate (S100), delay the equalized signal (EQ) to generate the equalized signal pattern (P) (S200), and generate the eye histogram (HG) based on the input signal (I) and the equalized signal pattern (P). In operation S300, filter codes signals CD and CF reflecting transmission characteristics of the transmission channel are generated based on the eye histogram HG (S400).

Steps S100 and S200 of FIG. 11 may be performed by the equalization filter unit 100 of FIG. 1, and steps S300 and S400 of FIG. 11 may be performed by the digital control unit 200 of FIG. 1. As such, redundant descriptions are omitted.

12 is a flowchart illustrating an example of generating the eye histogram of FIG. 11.

1 and 12, in generating the eye histogram (S300), the comparison bit signal DO is generated (S310) by comparing the level of the reference signal VREF and the input signal I (S310), and the comparison bit. An eye histogram HG may be generated based on the signal DO and the equalized signal pattern P (S320).

Step S310 of FIG. 12 may be performed by the comparator 210 of FIG. 1, and step S320 of FIG. 12 may be performed by the filter controller 250 of FIG. 1. Omit.

FIG. 13 is a flowchart illustrating an example of generating a filter code signal of FIG. 11.

1 and 13, when generating a filter code signal (S400), an eye pattern opening degree is calculated based on an eye histogram (HG), and the eye pattern opening degree is larger than a threshold (S410: YES), the feedback filter coefficient is calculated based on the eye histogram HG (S420), and the feedback filter code CD of the filter code signals CF and CD is generated based on the feedback filter coefficient to generate an equalization filter unit ( In operation S430, when the eye pattern opening degree is less than or equal to the threshold value (S410: NO), a feedforward filter code CF of the filter code signals CF and CD is generated. Then, the feed forward filter 110 of the equalization filter unit 100 may be provided (S440). According to an embodiment, as described above with reference to FIG. 6, an equalization filter is generated by generating a feedback filter code CD and a feedforward filter code CF of filter code signals CF and CD based on the feedback filter coefficients. It may be provided to the unit 100.

Steps S410, S420, S430, and S440 of FIG. 13 may be performed by the filter controller 250 of FIG. 1, and thus descriptions thereof will be omitted.

1, 3, 4, 8, and 13, the overall operation of the channel equalizer will be described. The eye pattern of the input signal I received through the transmission channel is open enough to transmit and receive data at a sufficiently low bit error rate, i.e., between a reception level corresponding to a logic high level and a reception level corresponding to a logic low level. Determine if enough gap is formed. In other words, the degree of eye pattern opening is measured to determine whether the threshold value is greater than or equal to the threshold value. When the degree of opening of the eye pattern is greater than the threshold value, the impulse response of the transmission channel is calculated using the equalization signal pattern P and the input signal I output from the feedback filter 150. By calculating the impulse response, the filter coefficients of the feedback filter 150, that is, the feedback filter codes CD1,..., CDn, may be generated. The digital controller 200 may provide feedback filter codes CD1,..., And CDn to the feedback filter 150 of the equalization filter unit 100 to adjust the filter coefficients.

On the other hand, when the eye pattern opening degree is equal to or less than a threshold value, that is, when the eye pattern of the input signal I received through the transmission channel is not open enough to transmit and receive data at a sufficiently low bit error rate, the digital controller. The control unit 200 may control the feedforward filter codes CF1 to CFm in a direction to amplify the high frequency component of the input signal I. In controlling the feedforward filter codes CF1, ..., CFm, it may not require the precision required for controlling the feedback filter codes CD1, ..., CDn. Therefore, the feedforward filter codes CF1,..., CFm of the feedforward filter 110 may be controlled by selecting and applying one filter code among the filter codes stored in the filter code group. The filter codes stored in the filter code group may be selectively applied to the feedforward filter 110, and the feedback filter 150 may be controlled to reach an operable eye pattern opening degree.

When the filter code of the feedforward filter 150 is reached to reach the above state, the digital control unit 200 calculates the impulse response of the transmission channel, thereby calculating the feedback filter 150 coefficient values, that is, the feedback filter code CD1. , ..., CDn) can be performed. That is, as described above, before controlling the filter coefficients of the feedback filter 150, the filter coefficients of the feedforward filter 110 are controlled based on the degree of opening of the eye pattern of the input signal I to thereby input the I signal. The channel equalizer 10 can be operated even when the eye pattern of the i) is not open enough to receive data below a certain bit error rate.

Referring to FIGS. 1, 11, and 13 again, the eye histogram HG generated by the digital controller 200 may be updated to generate a filter code signal CD by updating only for a predetermined period of time (S400). In order to generate the filter code signals CD and CF by updating each input signal I in consideration of the input signals I for a predetermined period (or clock) from the present time (S400). May be utilized. Alternatively, the filter code signals CD and CF may be generated based on the eye histogram based on the bit error rate of the input signal I received through the transmission channel (S400), and the result is transmitted to the equalization filter unit 100. If the bit error rate is larger than the threshold value after application, the process of generating the filter code signals CD and CF of FIG. 13 is repeated (S400), but the filter code signal (CD) is based on the existing eye histogram. Instead of generating CF, a new eye histogram may be generated based on the new input signal I and the new equalized signal pattern P (S300).

The channel equalizer, the receiver, and the channel equalization method according to the embodiments of the present invention have been described with a limited number of total filter taps for convenience of description, but a larger number of filters are within the scope of the inventive concept. It will be appreciated that the tabs can be configured and operated. Similarly, the configuration and operation for reducing the interference by the post cursor during the inter-symbol interference has been mainly described, it will be understood that it can be configured and operated to reduce the interference by the free cursor and post cursor. In addition, although the description has been limited to two cases of data received through the transmission channel, it should be understood that it may be configured and operated for a case having a larger number of symbols.

The present invention can be usefully used for a data transmission and reception apparatus. In particular, the present invention may be more usefully used for an equalizer for high-speed data transmission and reception, a receiver or a portable communication device including the same, and a data communication system.

As described above, the present invention has been described with reference to a preferred embodiment of the present invention, but those skilled in the art may vary the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It will be understood that modifications and changes can be made.

Claims (12)

An equalization filter unit receiving an input signal received through a transmission channel to generate an equalization signal based on a filter code signal, and sequentially generating the equalization signal pattern by sequentially delaying the equalization signal; And
To calculate a transfer function of the transport channel, an eye histogram is generated based on the input signal and the equalized signal pattern, and the filter code signal reflecting the transfer characteristic of the transport channel is generated based on the eye histogram. A channel equalizer comprising a digital control unit provided to the equalization filter unit. The method of claim 1, wherein the equalization filter unit
A feedforward filter for filtering and providing the input signal based on a feedforward filter code; And
And a feedback filter generating the equalization signal based on the filter code and the output signal of the feedforward filter, and sequentially delaying the equalization signal to generate the equalization signal pattern. The method of claim 1, wherein the digital control unit
A comparator for comparing a level of a reference signal with the level of the input signal to generate a comparison bit signal; And
And a filter controller for generating the eye histogram based on the comparison bit signal and the equalization signal pattern and generating the filter code signal based on the eye histogram. The method of claim 3, wherein the comparator
A reference signal generation unit for generating the reference signal based on a reference code signal; And
And a sample comparison unit for comparing the level of the reference signal with the level of the input signal to generate the comparison bit signal. 4. The filter of claim 3, wherein the filter controller is
An eye histogram generation unit that accumulates a value of the comparison bit signal corresponding to the level of the reference signal and generates the eye histogram including a reception level frequency distribution corresponding to each of the equalized signal combinations that the equalized signal pattern may have ; And
And a filter code calculation unit for generating the filter code signal based on the highest frequency reception level corresponding to each of the equalized signal combinations detected from the eye histogram. The method of claim 5, wherein the eye histogram generating unit
A counter for counting the comparison bit signal based on the equalization signal pattern to calculate a level reception frequency corresponding to the level of the reference signal;
A cumulative histogram generating unit that generates a cumulative histogram based on the level reception frequency corresponding to the level of the reference signal; And
And a histogram generating unit for generating the eye histogram by differentiating the cumulative histogram. 6. The filter code calculation unit of claim 5, wherein the filter code calculation unit
The eye pattern opening degree is calculated based on the eye histogram. When the eye pattern opening degree is larger than a threshold value, a feedback filter coefficient is calculated based on the eye histogram, and the filter code signal is based on the feedback filter coefficient. Generates a feedback filter code of the equalization filter unit and provides it to the feedback filter of the equalization filter unit, and generates a feedforward filter code of the filter code signal when the eye pattern opening degree is less than or equal to the threshold value. Channel equalizer, characterized in that provided in. The method of claim 1, wherein the digital control unit
Instead of performing analog-to-digital conversion on the input signal, the input signal is compared with a reference signal to find the highest frequency reception level for some of the combinations of the equalized signals that the equalized signal pattern may have. Generate the eye histogram by comparison,
And said some combinations are combinations for calculating filter coefficients of said equalization filter part. 9. The method of claim 8, wherein the number of levels of the reference signal is greater than the number of possible combinations of the equalization signal patterns, wherein the number of the some combinations of the combinations of equalization signals is for calculating the filter coefficients of the equalization filter portion. A channel equalizer, characterized in that the minimum number required. A demodulator for demodulating data into baseband signals on a carrier frequency;
A channel equalizer for generating an equalization signal reflecting characteristics of a channel based on an eye histogram of a reception level of the baseband signal to reduce intersymbol interference of the baseband signal; And
A decoder which decodes the equalized signal to restore transmission data;
The channel equalizer
An equalization filter unit generating the equalization signal based on the filter code signal by receiving the base band signal, and sequentially generating an equalization signal pattern by delaying the equalization signal; And
To calculate the transfer function of the transport channel, the eye histogram is generated based on the equalized signal and the equalized signal pattern, and the filter code signal reflecting the transfer characteristic of the transport channel is generated based on the eye histogram. And a digital control unit provided to the equalization filter unit. Receiving an input signal received through a transmission channel to sequentially generate an equalization signal based on the filter code signal;
Delaying the equalization signal to generate an equalization signal pattern;
Generating an eye histogram based on the input signal and the equalized signal pattern;
And generating the filter code signal reflecting the transfer characteristics of the transmission channel based on the eye histogram. The method of claim 11, wherein generating the filter code signal
Calculating an eye pattern opening degree based on the eye histogram;
When the eye pattern opening degree is larger than a threshold value, a feedback filter coefficient is calculated based on the eye histogram, and a feedback filter code of the filter code signal is generated based on the feedback filter coefficient and provided to a feedback filter of an equalization filter unit. Doing; And
And generating a feedforward filter code of the filter code signal to the feedforward filter of the equalization filter unit when the eye pattern opening degree is less than or equal to the threshold value.

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