KR101711031B1 - Equalizer, receiver using the same, and method of equalizing - Google Patents

Abstract

The channel equalizer includes an equalization filter section and a digital control section. The equalization filter unit receives the input signal received through the transmission channel, generates an equalization signal based on the filter code signal, and sequentially generates an equalization signal pattern by sequentially delaying the equalization signal. The digital control unit generates an i-th histogram based on the input signal and the equalization signal pattern to calculate a transfer function of the transmission channel, generates a filter code signal reflecting transfer characteristics of the transmission channel based on the i-th histogram, to provide.

Description

[0001] The present invention relates to an equalizer, a receiver using the equalizer,

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

During the high-speed data communication, the waveform of the data is greatly affected by the waveform of the neighboring symbols while the digital signal is transmitted at a high speed through a communication channel such as a circuit board, a wireless communication channel, an optical fiber or a cable at a limited bandwidth appear. Such a phenomenon is referred to as inter-symbol interference, and the energy of one symbol may interfere with the neighboring symbols, thereby deteriorating the communication performance. Particularly, as the transmission rate increases and the intervals between symbols become shorter, this phenomenon becomes worse and is one of the reasons for limiting the transmission rate in high-speed data communication.

A channel equalization filter can be used to compensate for performance degradation due to inter-symbol interference and to efficiently utilize the bandwidth of the channel. The channel equalization filter can be applied to an intermediate frequency and a baseband. In the intermediate frequency band, a frequency domain equalizer (FDE) is mainly used. In the baseband, a time domain equalizer Time-domain equalizer (TDE) is used. The time domain equalizer is a form of an adaptive equalization filter that can adaptively compensate for a channel by applying a variable filter characteristic even when an environmental change such as a characteristic of a channel, Can be designed. In such an adaptive equalization filter, an equalizer adaptive algorithm that automatically controls the characteristics of the filter in the transmission and reception stages during communication is important.

An object of the present invention is to provide a channel equalizer that reduces symbol interference of data received through a transmission channel.

It is another object of the present invention to provide a receiver that reduces symbol interference of data received over a transmission channel.

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

In order to accomplish one 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, generates an equalization signal based on a filter code signal, and sequentially generates an equalization signal pattern by sequentially delaying the equalization signal. Wherein the digital control unit generates an i-th histogram based on the input signal and the equalization signal pattern to calculate a transfer function of the transmission channel, and generates the i-th histogram based on the i-th histogram, And provides it to the equalization filter unit.

The equalization filter section 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.

The digital control unit may include a comparator and a filter controller. The comparator may compare the reference signal with the level of the input signal to generate a comparison bit 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 generating unit and a sample comparing unit. The reference signal generating 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 input signal with the reference signal.

The filter controller may include an eye histogram generation unit and a filter code calculation unit. Wherein the eye histogram generation unit accumulates the value of the comparison bit signal corresponding to the level of the reference signal to generate the eye histogram including the reception level frequency distribution corresponding to each of the equalization signal combinations that the equalization signal pattern can have Can be generated. The filter code calculation unit may generate the filter code signal based on the highest frequency reception level corresponding to each of the equalization 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 counts the comparison bit signal based on the equalized signal pattern to calculate a level reception frequency corresponding to the level of the reference signal. The cumulative histogram generating unit may generate a cumulative histogram based on the level receiving frequency corresponding to the level of the reference signal. The histogram generation unit may generate the eye histogram by differentiating the cumulative histogram.

Wherein the filter code calculation unit calculates an eye pattern opening degree based on the eye histogram and calculates a feedback filter coefficient based on the eye histogram when the eye pattern opening degree is larger than a threshold value, Generates a feed-forward filter code of the filter code signal and supplies the filter code signal to the feedback filter of the equalization filter unit when the degree of eye pattern opening is below the threshold value, To the feed forward filter of the filter section.

In an embodiment, the digital control unit does not perform an analog-to-digital conversion on the input signal, and the maximum frequency reception level for some combinations of the equalization signal combinations that the equalization signal pattern may have The eye histogram can be generated by comparing the input signal with a reference signal. Some combinations may be combinations for calculating the filter coefficients of the equalization filter portion.

Wherein the number of levels of the reference signal is greater than the number of possible combinations of the equalization signal pattern and the number of combinations of the equalization signal combinations may be a minimum number required to calculate the filter coefficient of the equalization filter unit .

In order to accomplish 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 signal received via the transmission channel on the carrier frequency into a baseband signal. The channel equalizer generates an equalization signal reflecting characteristics of a channel based on an i-histogram of the reception level of the baseband signal to reduce inter-symbol interference of the baseband signal. The decoder decodes the equalized signal to recover transmission data. The channel equalizer includes an equalization filter unit and a digital control unit. The equalization filter unit receives the baseband signal, generates the equalization signal based on the filter code signal, and sequentially generates an equalization signal pattern by delaying the equalization signal. The digital control unit generates the eye histogram based on the equalization signal and the equalization signal pattern to calculate a transfer function of the transmission channel, and generates the i-th histogram based on the filter code And supplies the signal to the equalization filter unit.

According to an aspect of the present invention, there is provided a channel equalization method comprising: receiving an input signal received through a transmission channel and sequentially generating an equalization signal based on a filter code signal; Generates an equalization signal pattern by delaying the signal, generates an eye histogram based on the input signal and the equalization signal pattern, and generates the filter code signal reflecting the transfer characteristic of the transmission channel based on the eye histogram.

Calculating an i-pattern opening degree based on the i-th histogram when the filter code signal is generated, calculating a feedback filter coefficient based on the i-th histogram when the i-pattern opening degree is greater than a threshold value, Generating a feedback filter code of the filter code signal based on the filter coefficient and providing the feedback filter code of the filter code signal to a feedback filter of the equalization filter unit; To the feed-forward filter of the equalization filter unit.

The channel equalizer, receiver, and channel equalization method according to 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 levels of the data symbols. By using the comparator instead of the analog-to-digital converter to generate the cumulative density function and the eye histogram of the equalized signal, the complexity and power consumption of the equalizer can be reduced.

In addition, since the channel equalizer, receiver and channel equalization method according to the embodiments of the present invention involve on-chip EYE monitoring in the equalization process, it is possible to grasp whether the child is open or closed, It is possible to calculate the operating condition of the judgment feedback filter without the pilot sequence even in the initial state in which the closed feedback filter is closed.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned above can 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 in accordance with embodiments of the present invention.
2 is a block diagram showing an example of an equalization filter unit included in the channel equalizer of FIG.
3 is a block diagram illustrating an example of a feedback filter included in the equalization filter unit of FIG.
FIG. 4 is a block diagram showing an example of a feedforward filter included in the equalization filter unit of FIG. 2. FIG.
5 is a block diagram illustrating a comparator included in the channel equalizer of FIG.
6 is a block diagram illustrating a filter controller included in the channel equalizer of FIG.
FIG. 7 is a block diagram showing an eye histogram generation unit included in the filter controller of FIG. 6. FIG.
FIG. 8 is a timing chart showing a process of generating an eye histogram using the channel equalizer of FIG. 1. FIG.
9 is a diagram showing a process of obtaining an input maximum frequency reception level according to each equalization signal pattern from the eye histogram.
10 is a block diagram illustrating a receiver in accordance with 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 showing an example of a step of generating an eye histogram of FIG.
13 is a flowchart showing an example of a step of generating the filter code signal of FIG.

For the embodiments of the invention disclosed herein, specific structural and functional descriptions are set forth for the purpose of describing an embodiment of the invention only, and it is to be understood that the embodiments of the invention may be practiced in various forms, The present invention should not be construed as limited to the embodiments described in Figs.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Similar reference numerals have been used for the components in describing each drawing.

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 a second component, and similarly, the second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having", etc., are intended to specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, But do not preclude the presence or addition of other features, numbers, steps, operations, elements, 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 to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

On the other hand, if an embodiment is otherwise feasible, the functions or operations specified in a particular block may occur differently from the order specified in the flowchart. For example, two consecutive blocks may actually be performed at substantially the same time, and depending on the associated function or operation, the blocks may be performed backwards.

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

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

The equalization filter unit 100 receives the input signal I received through the transmission channel and generates an equalization signal EQ based on the filter code signals CF and CD to delay the equalization signal EQ, And sequentially generates the signal pattern (P). The received input signal I may be a non-return-to-zero (NRZ) signal. When the equalization filter unit 100 is used in a receiver or a communication system, the received input signal I may be supplied to a carrier frequency band or an intermediate frequency band by a demodulator, for example, And may be a baseband signal demodulated to a baseband in an intermediate frequency band.

The digital controller 200 generates an eye histogram based on the input signal I and the equalization signal pattern P to calculate a transfer function of the transport channel, And supplies the generated filter code signals CF and CD to the equalization filter unit 100.

The digital control unit 200 does not perform the analog-to-digital conversion on the input signal I and does not perform the maximum frequency for some combinations of the combinations of equalization signals EQ that the equalization signal pattern P can have It is possible to generate the eye histogram HG by comparing the input signal I with the reference signal VREF to find the reception level. Some of the combinations may be combinations for calculating the 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 some of the combinations of the equalization signals EQ is greater than the number of combinations of the equalization signal pattern P, Lt; / RTI >

The digital control unit 200 may include a comparator 210 and a filter controller 250. The comparator 210 may compare the reference signal with the level of the input signal I to generate a comparison bit signal DO. 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.

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

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

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

The feedback filter 150 generates an equalized signal EQ based on the filter codes CF and CD and the output signal FO of the feed forward filter 100 and delays the equalized signal EQ to generate an equalized signal pattern P). The feedback filter 150 may be a Decision Feedback Equalizer for reducing the post-cursor ISI of the channel by feeding back the result of determining the symbol for the received signal I. The symbol for the delayed input signal may be determined to generate a delayed equalized signal. In determining the symbol of the input signal I, the ISI may be determined by the delayed equalized signal of the delayed input signal.

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

3, the feedback filter 150 includes a determination unit 160, first to nth delay elements 171 to 17n, and first to nth multipliers 151 to 15n . The first to the n-th delay elements 171 to 17n sequentially delay the equalization signal EQ generated by the determination unit 160 to generate equalization signal patterns P ({P1, ..., Pn) And generates equalization signals P1, ..., Pn. The first to n-th multipliers 151 to 15n multiply the equalized signal patterns P (P1, ..., Pn) generated by the first to the n-th delay elements 171 to 17n by delayed equalization (CD1, ..., CDn) of the feedback filter code CD ({CD1, ..., CDn}) to the signals P1, ..., Pn, respectively, to the decision unit 160 . The decision unit 160 performs an addition and subtraction operation on the signals supplied from the first to nth multipliers 151 to 15n to the output signal FO of the feedforward filter 110 applied from the feedforward filter 110, It is possible to generate an equalization signal EQ by performing a symbol decision operation having nonlinear characteristics. This series of operations is performed in response to a 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 synchronous clock CLK.

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

4, the feed-forward filter 110 may include an adder 120, first to n-th delay elements 111 to 11n, and first to nth multipliers 131 to 13n. have. The first to nth delay elements 111 to 11n may provide signals to the first to nth multipliers 131 to 13n sequentially delaying the input signal I. [ The first to nth multipliers 131 to 13n multiply the feed forward filter coefficients of the signals and the feedforward code signals CF (CF1, ..., CFm) sequentially delaying the input signal I CF1, ..., CFm) to the adder 120. [ The adder 120 generates a signal obtained by adding the signals multiplied by the feedforward filter coefficients CF1, ..., CFm to the output signal FO of the feedforward filter 110 and provides the signal to the feedback filter 150 . Such a series of operations may be performed in response to a synchronous clock (CLK) having the same frequency as the sampling frequency of the input signal, but may be performed independently of the synchronous clock (CLK). The feedback filter 150 generates an equalizing signal EQ in response to a rising edge or a falling edge of the synchronous clock CLK in the case of operating in response to the synchronous clock CLK can do.

4, the feedforward filter 110 may be implemented as an Infinite Impulse Response (IIR) filter or as an < RTI ID = 0.0 > Fractionally Spaced Equalizer (FSE).

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

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

The reference signal generating unit 230 may generate the reference signal VREF based on the reference code signal CV. The reference signal VREF is a reference for comparison of magnitudes for representing 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 . According to the embodiment, the reference signal VREF may be a signal which changes in a relatively long period in comparison with the period of the input signal I. The reference signal generating unit 230 may receive the reference code signal CV, which is a digital signal or an analog signal, and output a reference signal VREF, which is an analog signal. Therefore, as will be described later, the sample comparison unit 220 samples and receives the reference signal VREF from the reference signal generation unit 230, compares the input signal I received through the transmission channel with the input signal I, It is possible to generate the signal D0.

The sample comparing unit 220 can compare the level of the input signal I with the reference signal VREF to generate the comparison bit signal DO. That is, the sample comparison unit 220 compares only the magnitude of the reference signal VREF with the input signal I without performing the analog-to-digital conversion of the input signal I and outputs the logic high level and the logic And outputs a comparison bit signal DO having only a low level (logic low). Therefore, the input signal I can be operated by receiving the input signal I of high frequency in comparison with 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 a 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 synchronous clock CLK.

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

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 generation unit 260 accumulates the value of the comparison bit signal DO corresponding to the level of the reference signal VREF to generate a reception histogram corresponding to each of the equalization signal combinations that the equalization signal pattern P can have, And generate an eye histogram (HG) including the distribution. The eye histogram generation unit 260 generates a comparison histogram signal DO corresponding to each reference signal VREF for each of the reference signals VREF that is greater than the number of information symbols that the input signal I can have The cumulative cumulative frequency can be calculated. For example, when the number of symbols that the input signal I may have is 8, the number of the reference signals VREF or the number of levels of the reference signal VREF may be 24. However, since the number and the range of the maximum frequency reception levels required for calculating the impulse response or the transfer function of the transmission channel can be specified, only the reference signal VREF corresponding to the specific equalization signal pattern is used to generate the eye histogram HG, May be generated. In this case, the cumulative frequency for the reference signals excluding the reference signal VREF corresponding to the specific equalized 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 is set to a logic high level And has only a logic low level (logic low). Therefore, when the comparison bit signal DO is logic high, i.e., 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, Signal level. The accumulated frequency of the corresponding reference signal VREF can be obtained by counting the number of times that the comparison bit signal DO corresponding to the current reference signal VREF is logic high. The comparison bit signal DO may have the logic high level when the voltage of the input signal I is lower than the reference signal VREF and the voltage of the input signal I is higher than 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 the embodiment.

The reference code signal CV may be provided by the channel parameter calculation unit 270 as described below, or may be provided by an external control circuit. The reference code signal CV may be generated so that the level of the reference signal VREF generated in accordance with the reference code signal CV increases by a unit level and the reference code signal CV may be generated in accordance with the reference code signal CV So that the level of the generated reference signal VREF decreases by the unit level.

After obtaining the cumulative frequency corresponding to each of the reference signals VREF, on the basis of the difference with the cumulative frequency corresponding to the reference signal VREF adjacent to each reference signal VREF, ).

The filter code calculation unit 270 can 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, it is possible to further provide the reference histogram generation unit 260 with a reference code signal CV for generating the reference signal VREF applied to the sample comparison unit 220. [

The filter code calculation unit 270 can determine the eye pattern opening degree based on the eye histogram HG and generate the feedback filter code CD so that the filter coefficients of the feedback filter 150 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, A feedback filter code CD of the filter code signals CF and CD or the filter code signals CF and CD can be generated and provided to the feedback filter 150 of the equalization filter unit 100. [ In this case, the filter code signals CF and CD are generated according to the number of precursors and post-cursors to be considered for reducing inter-symbol interference, that is, the number of filter taps of each filter, and are provided to the equalization filter unit 100 And 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, if the degree of eye pattern opening is less than or equal to the threshold value, a 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 And adjust the feedforward filter 110 to improve the degree of opening of the eye, which indicates the discriminability of the received signal.

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

7, the eye histogram generation unit 260 may include a counter 261, a cumulative histogram generation unit 263, and a histogram generation 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 equalized signal pattern P. [ By obtaining the level frequency corresponding to the level of each reference signal VREF in this way, a reception level cumulative frequency distribution corresponding to each of the equalized signal combinations that the equalized signal pattern P can have is obtained. As described below with reference to Figs. 9 and 10, among the equalized signal combinations that the equalized signal pattern may have, a transmission corresponding to the impulse response of the transmission channel required to generate the filter code signal CD, CF May be performed on a portion of the equalization signal pattern sufficient to generate the coefficients of the function.

The cumulative histogram generating unit 263 can generate the cumulative histogram CHG based on the level receiving 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 That is, the frequency for each reference signal level (VREF).

The histogram generation unit 265 may generate the eye histogram HG by differentiating the cumulative histogram CHG. The level of the reference signal VREF may be determined so that the interval between the levels of neighboring reference signals is constant so that a reception level cumulative frequency distribution corresponding to each of the equalized signal combinations that the equalized signal pattern P may have is obtained . The eye histogram HG can be generated by calculating the difference between the cumulative histogram, i.e., the frequency for each reference signal VREF and the level receiving frequency for the adjacent reference signal.

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

Hereinafter, a process of generating an eye histogram will be described with reference to FIGS. 1, 5, 7, and 8. FIG. After the reference code signal CV is initialized to zero, the reference signal generating unit 230 of the comparator 210 generates a reference signal VREF that increases linearly or according to a predetermined rule as the reference code signal CV increases. Lt; / RTI > 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 via the transmission channel at the rising edge of the synchronous clock CLK in response to the synchronous clock CLK And provides a comparison bit signal DO which is digital data having one bit as a result. The counter 261 of the eye histogram generation unit 260 determines that the comparison bit signal D0 is at a logic high level (here, the input signal I is larger than the reference signal VREF) The logic high level) is accumulated and stored in the register. The digital control unit 200 can generate the cumulative histogram CHG for each reference signal VREF by repeating the process while increasing the reference code signal CV by the unit interval for each sample collection interval W. [ It is possible to generate the eye histogram HG by obtaining the difference between the cumulative histogram, i.e., the frequency for each reference signal VREF and the frequency for the 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.

Referring back to FIG. 3 and FIG. 4, the impulse response of the transmission channel may be distributed to one cursor, m pre-cursors, and n post-cursors. Or the size of the (n + 1) th or more precursors of the impulse response and the size of the (m + 1) th or more precursors is negligible, the impulse response of the transmission channel may be a single cursor, may be distributed into m pre-cursors and n post-cursors. The input signal (I) received through the transmission channel with the impulse response is determined by performing a convolution integration of the transmission signal with the impulse response. That is, the magnitude of the inter-symbol interference of the received signal is determined by the combination of the received signal m, n interference components and m, n symbols before and after the symbol.

Equation (1) is expressed as an equalization signal pattern around the current cursor.

[Equation 1]

In Equation (1), PPi is a matrix having a total of n + m + 1 elements, which is a combination of j-th combinations of equalization signals that an equalization signal pattern can have. J is the number of combinations of equalization signals that the equalization signal pattern can have (J is equal to m + n + 1 squared of 2, since there are a number of equalization signal patterns with m + n + 1 squares of 2) , n is the number of postcursors, and m is the number of precursors. Where sk (k is an integer equal to or greater than -m and equal to or less than n) represent possible symbols of the input signal. For example, in the case of a non-return-to-zero (NRZ) signal, sk may have a symbol value of -1 or 1, respectively.

(J is an integer equal to or greater than 1 and equal to or less than J) of the input signal I received through the transmission channel is expressed by a matrix, the following equation (2) is satisfied.

&Quot; (2) "

In Equation (2), ak (k is an integer equal to or greater than n and equal to or less than n) are coefficients of a transfer function corresponding to the precursors and the post-cursors and indicative of an impulse response of a transmission channel, and rj An integer equal to or greater than 1 and equal to or less than J) corresponds to a substantial magnitude of the input signal I received.

Since the size of the input signal I received through the transmission channel has a number of J branches due to intersymbol interference, it can have J branches at 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 It is possible to calculate the magnitude of the input signal I for some equalization signal patterns rather than the equalization signal pattern through the eye histogram HG. In other words, when the digital control unit 200 receives an equalization signal pattern P from the equalization filter unit 100 and corresponds to an equalization signal pattern having a combination of specific equalization signals, , And generate an eye histogram (S300).

Referring again to FIGS. 7 and 8, the cumulative histogram CHG represents the level values of the reference signals corresponding to each of the equalization signal patterns P, that is, the accumulated histogram rank values, the level received cumulative frequency corresponding to each of them, I.e., cumulative histogram frequency values. However, the method of generating the eye histogram (HG) may be changed according to a method of accumulating the level reception cumulative frequency. The eye histogram HG may include the level values of the reference signals corresponding to each of the equalization signal patterns P, that is, the eye histogram class values and the level receiving frequency corresponding to each of them, i.e., the eye histogram frequency values.

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

Referring to Figs. 1 and 9, for convenience of explanation, it is assumed that two postcursors are considered to reduce intersymbol interference, that is, when n is 2 and J is 8, the two postcursors correspond to the impulse response of the transmission channel The process of calculating the coefficients ak of the transfer function will be described. Some combinations of possible equalization signals PP1, ..., PPJ of the equalization signal pattern P, when the input signal I received through the transmission channel has an eye pattern as shown at the left, (PP3, PP5, PP6). In this case, the eye histogram for each of the combinations of equalization signals PP3, PP5, and PP6 can be separately stored. (R3, r5, r6) of the i-th histogram corresponding to the maximum frequency for each of the combinations of equalization signals PP3, PP5, PP6 can be determined, and the input values received through the transmission channel The rank values r3, r5 and r6 corresponding to the magnitude of the signal I are the convolution of the coefficients ak of the transfer function of the transmission channel and the symbols sk of the input signal I, for example, when n is 2 and J is 8, the coefficients ak of the transfer function of the transmission channel can be calculated by Equation (3) below.

&Quot; (3) "

R3, r5 and r6 are rank values of the i-th histogram corresponding to the maximum frequency for each of the combinations of equalization signals PP3, PP5 and PP6, a0, a1 and a2 are 2 When considering the number of post-cursors, the coefficients of the transfer function of the transmission channel.

For convenience of explanation, the process of calculating the transfer function coefficients ak corresponding to the impulse response of the transmission channel when two postcursors are considered, that is, when n is 2 and J is 8 , It is possible to calculate the coefficients ak of the transfer function corresponding to the impulse response of the transmission channel in a similar manner even when considering m precincts and arbitrary n postcursors.

10 is a block diagram illustrating a receiver in accordance with embodiments of the present invention.

10, the receiver 20 includes a demodulator 300, a channel equalizer 10, and a decoder 400. [

Demodulator 300 demodulates the received signal on the transmission channel into a baseband signal at a carrier frequency. The channel equalizer 10 generates an equalization signal EQ reflecting the characteristics of the channel based on the eye histogram HG with respect to the reception level of the baseband signal in order 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 is omitted. The decoder 400 decodes the equalized signal EQ to recover the transmission data.

The demodulator 300 may be a frequency shift keying (FSK), a frequency shift keying (MFSK), an amplitude shift keying (ASK), an on-off keying (OOK), a phase shift keying (PSK), a quadrature amplitude modulation ), A Minimum-Shift Keying (MSK), a Continuous Phase Modulation (CPM), a Pulse Code Modulation (PWM), a Pulse Width Modulation (PWM), a Pulse Amplitude Modulation (PAM), a Pulse Density Modulation (PDM) ), TCM (Trellis Coded Modulation), OFDM (Orthogonal Frequency Division Multiplexing), SC-FDE (Single Carrier FDMA), CSS (Chirp Spread Spectrum), DSSS (Direct Sequence Spread Spectrum), FHSS (Frequency Hopping Spread Spectrum) And a demodulator that demodulates the modulated signals in at least one of the modulation schemes including THSS (Time Hopping Spread Spectrum) and the like.

Decoder 400 may include error detection (e. G., Error detection) that improves bit error rate performance in the transport channel environment with limited power or limited bandwidth by inserting structured redundancy into the input signal < Code or an error correction code to decode the encoded signal. 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 a source coding signal in a lossless or lossless compression scheme as well as channel coding as described above.

The decoder 400 may be implemented with a decoding algorithm such as a Hamming Code, a Reed-Solomon Code, a Viterbi Code, a Bose and Ray-Chaudhuri code, a Turbo Code, an LDPC Gap code, Goppa code, Hadamard code, Hagelbarger code, LT code (Constant-weight code, Convolution code, Group code) Luby Transform Codes, Lexicographic codes, Latin Square based codes, Online codes, Raptor codes, Reed-Muller codes, Repeat-Accumulate codes, A decoding code 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 (ARQ), which provides an ARQ (Automatic Repeat Request) for transmitting a retransmission signal to the sender when an error is detected in the decoder 400 . Alternatively, the receiver 20 may perform a Hybrid Automatic Repeat Request (HARQ) to perform 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 controller 200. The equalization filter unit 100 receives the baseband signal and generates an equalization signal EQ based on the filter code signals CF and CD and delays the equalization signal EQ to sequentially output the equalization signal pattern P . The digital controller 200 generates an eye histogram HG based on the equalization signal EQ and the equalization signal pattern P to calculate the transfer function of the transmission channel and generates the eye histogram HG based on the eye histogram HG Generates the filter code signal reflecting the transmission characteristics of the transmission channel, and provides the filter code signal to the equalization filter unit 100. Since the channel equalizer 10 of FIG. 10 is similar to the channel equalizer 10 of FIG. 1, a duplicate description will be omitted.

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

Referring to FIGS. 1 and 11, in the channel equalization method according to an embodiment of the present invention, an input signal I received through a transmission channel is received and an equalization signal EQ is sequentially Generates an equalization signal pattern P by delaying the equalization signal EQ in S200 and generates an eye histogram HG based on the input signal I and the equalization signal pattern P S300), and generates filter code signals CD and CF reflecting transfer characteristics of the transmission channel based on the eye histogram HG (S400).

The steps S100 and S200 of FIG. 11 may be performed by the equalization filter unit 100 of FIG. 1 and the steps S300 and S400 of FIG. 11 may be performed by the digital control unit 200 of FIG. So that redundant description is omitted.

12 is a flowchart showing an example of a step of generating an eye histogram of FIG.

Referring to FIGS. 1 and 12, in generating the eye histogram (S300), a comparison bit signal DO is generated by comparing the reference signal VREF with the level of the input signal I (S310) It is possible to generate the eye histogram HG based on the signal DO and the equalization signal pattern P (S320).

The step S310 of FIG. 12 may be performed by the comparing unit 210 of FIG. 1, and the step S320 of FIG. 12 may be performed by the filter controller 250 of FIG. It is omitted.

13 is a flowchart showing an example of a step of generating the filter code signal of FIG.

1 and 13, in generating the filter code signal (S400), the eye pattern opening degree is calculated based on the eye histogram HG. If the eye pattern opening degree is larger than the threshold value (S410: YES), a feedback filter coefficient is calculated based on the eye histogram HG (S420), a feedback filter code CD of the filter code signals CF and CD is generated based on the feedback filter coefficients, (S430). If the eye pattern opening degree is equal to or smaller than the threshold value (S410: NO), the feedforward filter code CF of the filter code signals CF and CD is generated To the feedforward filter 110 of the equalization filter unit 100 (S440). According to the embodiment, as described above with reference to Fig. 6, a feedback filter code (CD) and a feedforward filter code (CF) of the filter code signals CF and CD are generated based on the feedback filter coefficients, (100).

The steps S410, S420, S430, and S440 of FIG. 13 can be performed by the filter controller 250 of FIG. 1, so that redundant description is omitted.

The overall operation of the channel equalizer will be described with reference to Figs. 1, 3, 4, 8, and 13. Fig. It is determined whether the eye pattern of the input signal I received through the transmission channel is open enough to transmit / receive data at a sufficiently low bit error rate, that is, between the reception level corresponding to the logic high level and the reception level corresponding to the logic low level It is determined whether or not the interval is sufficiently formed. In other words, the degree of opening of the eye pattern is measured to determine whether it is equal to or 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 when the eye pattern opening degree is larger than the threshold value. The filter coefficients of the feedback filter 150, i.e., the feedback filter codes CD1, ..., CDn, can be generated by calculating the impulse response. The digital control unit 200 may adjust the filter coefficients by providing the feedback filter codes CD1, ..., CDn to the feedback filter 150 of the equalization filter unit 100. [

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

The digital control unit 200 controls the filter code of the feed forward filter 150 so that the digital control unit 200 calculates the feedback filter 150 coefficient values, i.e., the feedback filter code CD1 , ..., CDn). That is, by controlling the filter coefficients of the feedforward filter 110 based on the degree of eye pattern opening of the input signal I before controlling the filter coefficients of the feedback filter 150, The operation of the channel equalizer 10 is possible even if the eye pattern of the channel equalizer 10 is not open enough to receive data at a certain bit error rate or less.

Referring again to FIGS. 1, 11 and 13, the eye histogram HG generated by the digital controller 200 may be used to generate a filter code signal CD (S400) by updating only for a predetermined period of time And generates filter code signals CD and CF (S400) by updating each input signal I in consideration of the input signals I for a certain period (or clock) preceding the present It can also be utilized. (S400) based on the bit error rate of the input signal (I) received through the transmission channel on the basis of the eye histogram (S400), and outputs the filter code signal CD and CF to the equalization filter unit 100 When the bit error rate becomes larger than the threshold value after the application of the filter code signal CD (CD), the filter code signal CD and CF of FIG. 13 are generated again , CF), a new eye histogram can be generated based on the new input signal I and the new equalization signal pattern P (S300).

Although the number of total filter taps has been described for the sake of convenience of description of the channel equalizer, the receiver and the channel equalization method according to the embodiments of the present invention, It is to be understood that the present invention can be configured and operated in a tab. Similarly, although it has been described primarily in terms of the configuration and operation of reducing interference by the post-cursor during inter-symbol interference, it should be understood that it can be configured and operated to reduce interference by precursors and post-cursors. In addition, the present invention is limited to the case where two symbols of data are received through a transmission channel. However, it should be understood that the present invention can be configured and operated for a case having more symbols.

INDUSTRIAL APPLICABILITY The present invention can be usefully utilized in a data transmission / reception apparatus. Particularly, the present invention can be more effectively used for an equalizer, a receiver or a portable communication device and a data communication system including the same for high-speed data transmission and reception.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. It will be understood that the invention may be modified and varied without departing from the scope of the invention.

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 an equalization signal pattern by sequentially delaying the equalization signal; And
Generating an i-th histogram based on the input signal and the equalization signal pattern to calculate a transfer function of the transmission channel, generating the filter code signal reflecting transfer characteristics of the transmission channel based on the i-th histogram, To the equalization filter unit,
The digital control unit
A comparator for comparing a reference signal with a 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 filter controller
An i-th histogram generation unit for generating the i-th histogram including a reception level frequency distribution corresponding to each of the equalization signal combinations that the equalization signal pattern can have by accumulating the value of the comparison bit signal corresponding to the level of the reference signal, ; 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 equalization signal combinations detected from the eye histogram. The apparatus of claim 1, wherein the equalization filter unit
A feed forward filter for filtering and providing the input signal based on a feed forward filter code; And
And a feedback filter for generating the equalization signal based on the filter code and the output signal of the feedforward filter and sequentially generating the equalization signal pattern by delaying the equalization signal. delete The apparatus of claim 1, wherein the comparator
A reference signal generation unit for generating the reference signal based on the reference code signal; And
And a sample comparison unit for comparing the reference signal with the level of the input signal to generate the comparison bit signal. delete The apparatus of claim 1, wherein the eye histogram generation unit
A counter for counting the comparison bit signal based on the equalization signal pattern and calculating a level reception frequency corresponding to the level of the reference signal;
A cumulative histogram generation unit for generating a cumulative histogram based on the level reception frequency corresponding to the level of the reference signal; And
And a histogram generation unit for generating the eye histogram by differentiating the cumulative histogram. The apparatus of claim 1, wherein the filter code calculation unit
Calculating an eye pattern opening degree based on the eye histogram; calculating a feedback filter coefficient based on the eye histogram when the eye pattern opening degree is greater than a threshold value; And generates a feedforward filter code of the filter code signal to generate the feedforward filter code of the equalization filter unit and supplies the feedforward filter code of the equalization filter unit to the feedforward filter unit of the equalization filter unit when the eye pattern opening degree is equal to or smaller than the threshold value, To the channel equalizer. 2. The apparatus of claim 1, wherein the digital control unit
The input signal is converted to a reference signal to search for the most frequent reception level for some combinations of the equalized signal combinations that the equalized signal pattern may have without performing an analog to digital conversion on the input signal. Generates the child histogram by comparing the child histogram,
Wherein some of the combinations are combinations for calculating filter coefficients of the equalization filter portion. delete A demodulator for demodulating an input signal received on a carrier frequency through a transmission channel into a baseband signal;
A channel equalizer for generating an equalization signal reflecting the characteristics of the transmission channel based on an i-th histogram of the reception level of the baseband signal to reduce inter-symbol interference of the baseband signal; And
And a decoder for decoding the equalized signal to recover transmission data,
The channel equalizer
An equalization filter unit receiving the baseband signal to generate the equalization signal based on the filter code signal and sequentially generating an equalization signal pattern by delaying the equalization signal; And
Generates an i-th histogram based on the equalization signal and the equalization signal pattern to calculate a transfer function of the transmission channel, generates the filter code signal reflecting transfer characteristics of the transmission channel based on the i-th histogram And a digital control unit for providing the digital signal to the equalization filter unit,
The digital control unit
A comparator for comparing a reference signal with a 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 filter controller
An i-th histogram generation unit for generating the i-th histogram including a reception level frequency distribution corresponding to each of the equalization signal combinations that the equalization signal pattern can have by accumulating the value of the comparison bit signal corresponding to the level of the reference signal, ; And
And a filter code calculation unit for generating the filter code signal based on a highest frequency reception level corresponding to each of the equalization signal combinations detected from the eye histogram. delete delete

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