TWI390916B - Tap/group-revivable decision feedback equlizing method and equalizer - Google Patents

Description

Tap/group can reply to decision feedback equalization method and equalizer

The present invention relates to a decision feedback equalizer, and more to a tap/group returnable decision feedback equalization method and an equalizer using the same.

In general, the equalizer is designed to eliminate multipath interference (mutlipath) in the communication system receiver for the purpose of avoiding signal distortion.

Referring to Figure 1, a schematic diagram of a prior art decision feedback equalizer 10. The decision feedback equalizer 10 includes a feedforward filter 102, a feedback filter 104, a subtractor 106, and a clipper 108. The feedforward filter 102 generates a preamble signal t2 from the received input t1. The subtracter 106 subtracts the post-signal t3 output from the feedback signal 104 to the preamble signal t2 to generate an equalization signal t4. Then, the clipper 108 uses the equalized signal t4 to generate a decision output t5, and the decision output t5 is fed back to the feedback filter 104 to generate the post signal t3.

Referring to FIG. 2, it is a schematic diagram of the feedforward filter 102 and the feedback filter 104 of FIG. The feedforward filter 102 has M ^* m taps divided into M groups, each of which has m taps. For example, a group of 0 has a tap 0, a tap 1, ..., and a tap m-1. On the other hand, the feedback filter 104 has N ^* n taps divided into N groups, and each group has n taps. For example, a group of 0 has a tap 0, a tap 1, ..., and a tap n-1.

In the prior art, whether the tap of any group of the feedforward filter 102 or the feedback filter 104 is selected and used for equalization is based on one of the sub-fractions of any one of the groups. Whether the connection coefficient is greater than a preset value. If the tap coefficient of one of the group is greater than the preset value, all taps of any group are selected and used for equalization. Otherwise, all taps of any group are discarded and are no longer selected and used for equalization. However, because multipath interference distortion changes over time, any tap that is discarded due to sudden multipath interference at a particular point in time may still be useful at other points in time, under normal multipath interference. Therefore, discarding the tap that has a tap coefficient greater than the preset value will degrade the performance of the decision feedback equalizer 10.

The present invention provides a tap/group-recoverable decision feedback equalizer for a tap/group-revivable decision feedback equalizer, wherein the equalizer includes a former a feed-forward filter and a feedback filter, the feedforward filter including a plurality of taps divided into M group groups, and the feedback filter includes dividing into N group groups a plurality of taps, wherein each of the N groups has n taps, and the M groups each have m taps, wherein M, N, m, and n are positive integers greater than 2, and the method includes: Having all the taps generate respective tap coefficients; selecting all the taps of any group of the feedforward filters whose tap coefficients are greater than a first preset value, and selecting any of the group of the feedback filters All taps with a coefficient greater than a second preset value; selecting the feedforward filter Any one of the groups of the group whose branching coefficient is not greater than the first predetermined value but whose tap coefficient of the adjacent group is greater than the first preset value, and any group of the feedback filters is selected a tap that has a tap coefficient that is not greater than the second predetermined value but whose tap coefficient of the adjacent group is greater than the second preset value; and equalization using the selected taps (equalization).

The present invention further provides a tap/group returnable decision feedback equalizer, comprising: a feedforward filter for filtering a preamble signal from an input, the feedforward filter having a group of M groups a plurality of taps, wherein the M groups each have m taps, and both M and m are positive integers greater than 2; a subtractor for subtracting the preamble signal output by the feedforward filter a post signal to generate an equalizer output; a clipper for cutting the equalizer output into a decision output; and a feedback filter for filtering the decision output into the post signal The post signal is fed back to the subtractor, wherein the feedback filter has a plurality of taps divided into N groups, wherein the N groups have n taps, and N and n are both greater than 2. a positive integer; and a function, comprising selecting all taps of any group of the feedforward filters that have a tap coefficient greater than a first preset value, and selecting a tap coefficient of any group of the feedforward filters is not greater than The first preset value, but the tap coefficient of the adjacent group is greater than a plurality of taps of the first preset value, selecting all taps of any group of the feedback filters having a tap coefficient greater than a second preset value, and selecting a tap in any group of the feedback filters The plurality of taps whose coefficients are not greater than the second preset value but whose tap coefficients of adjacent groups are greater than the second preset value, and the tapped operations are performed by the selected taps.

The following is a description of the preferred embodiment of the invention. The examples are intended to illustrate the principles of the invention, but are not intended to limit the invention. The scope of the invention is defined by the appended claims.

It is to be noted that the architecture of the first and second embodiments of the present invention is only for the purpose of describing the present invention and is not intended to limit the scope of the patent application of the present invention.

As described above, the decision feedback equalizer 10 includes a feedforward filter 102, a feedback filter 104, a subtractor 106, and a clipper 108. The feedforward filter 102 has M ^* m taps divided into M groups, each of which has m taps. The feedback filter 104 has N ^* n taps divided into N group families, and each group has n taps. Each tap of the feedforward filter 102 or the feedback filter 104 has a corresponding tap coefficient. In addition, the decision feedback equalizer 10 can be used to equalize the data fields of an Advanced Television Systems Committee (ATSC), but is not limited thereto. The feedforward filter 102 filters out a preamble signal t2 from an input t1. The subtractor 106 subtracts the preamble signal t3 from the preamble signal t2 to generate an equalization signal t4. The clipper 108 intercepts the equalized signal t4 to generate a decision output t5, and the decision output t5 is fed back to the decision feedback equalizer 105 and filtered to generate the post signal t3. Furthermore, the decision feedback equalizer 10 also includes a selection unit (not shown) for performing the process shown in FIG. 3, and the selection unit can be implemented by a circuit, a program, or a combination of the two. .

Referring to Figure 3, there is shown a flow diagram of a tap/group replies decision feedback equalization method 30 in accordance with an embodiment of the present invention. The tap/group can be returned The complex decision feedback equalization method 30 begins in step S301 and can be implemented by the equalizers in Figures 1 and 2.

In step S302, all of the taps of the feedforward filter 102 and the feedback filter 104 are trained. In particular, the decision feedback equalizer 10 can perform operations to generate all of the required tap coefficients. However, those skilled in the art will be well aware of how to produce the required tap coefficients, and such details will be omitted herein to simplify the description.

In step S303, a maximum tap coefficient of any one of the feedforward filter 102 or the feedback filter 104 is set separately.

In step S304, in any one of the feedforward filter 102 and the feedback filter 104, a tap having a tap coefficient greater than the first preset value and the second preset value is selected. Since all the tap coefficients are calculated in step S302, the maximum tap coefficients of any one of the feedforward filter 102 and the feedback filter 104 can be compared with the first and second preset values. If the maximum tap coefficient of any one of the feedforward filter 102 or the feedback filter 104 is greater than the first or second preset value, all of the feedforward filter 102 or the feedback filter 104 The taps are selected and used for subsequent equalization.

In step S305, any group of the feedforward filter 102 lacks a tap coefficient greater than the first preset value, but a tap coefficient of the adjacent group is greater than the first preset value, and the plurality of taps will be selected. And any group of the feedback filter 104 lacking a tap coefficient greater than the second preset value, but a tap coefficient of its adjacent group is greater than the second preset value will be selected. That is to say, any one of the feedforward filter 102 or the feedback filter 104 lacking the tap coefficient is greater than the first or second preset value is not as prior art. Was immediately abandoned. Conversely, the present invention checks whether any of the feedforward filter 102 or the feedback filter 104 has a missing branching coefficient that is greater than a preset value. If one of the adjacent group has a tap coefficient greater than the first or second preset value, there may still be several taps if any group lacks a tap coefficient greater than the first or second preset value. It is selected and used to perform subsequent equalization. For example, if the group 1 of the feedforward filter 102 (refer to FIG. 2) has no tap coefficient larger than the first preset value, the group 0 has a tap larger than the first preset value. For the coefficient, then several taps in group 1 that are close to group 0 will be selected. In addition, if the group 2 also has a tap coefficient larger than the first preset value, then several taps in the group 1 close to the group 2 are also selected. Therefore, for any group of groups that do not have a tap coefficient greater than the first or second preset value, if the left neighbor group or the right neighbor group has a score greater than the second or second preset value When the coefficient is connected, a plurality of taps in the group close to the left neighbor group or the right neighbor group are correspondingly selected, and if the left neighbor group or the right neighbor group has greater than the first Or the tap coefficient of the second preset value, the plurality of taps close to the left neighbor group and the plurality of taps in the right neighbor group are correspondingly selected. For the feedforward filter 102, the number of taps selected is less than m, preferably less than m/2; for the feedback filter 104, the number of taps selected is less than n, preferably less than n/2 . The number of taps selected is not fixed and can be changed with different design conditions.

In step S306, the decision feedback equalizer 10 performs an equalization operation using the selected tap, and thus the tap/group replies decision feedback equalization method 30 is completed in step S307.

The tap/group of the present invention can reply back to the prior art relative to the prior art The feed equalization method 30 will not immediately discard any group that lacks the first or second preset value, and will also check the adjacent group to determine that the defect is greater than the first or second preset value. Whether the group has a tap that can be selected for subsequent equalization. Since this selection step will be repeated for each ATSC data field or for each specific number of ATSC data fields, any group or its taps may be restored. For example, if a first equalization operation is performed, no branching coefficient is greater than a preset value in group 0, group 1 and group 2, but group 3 has a tap coefficient greater than a preset value. , all the taps of group 0 and group 1 will not be selected, but several taps in group 2 close to the group 3 and all taps of group 3 will be selected and used Perform equalization work. Thereafter, if a second equalization operation is performed, and the taps of the plurality of taps of the previously selected group 2 have a tap coefficient greater than a preset value, all taps in the group 2 are selected, and the result is Several taps in group 1 that are close to group 2 are restored and selected for equalization because group 2 has a tap coefficient greater than the preset value. Therefore, several taps of group 1 and group 2 will be restored at this time. If the equalization operation is performed subsequently, and the tap coefficients of the previously selected group 1 have a tap coefficient greater than the preset value, the number of taps of the group 0 and the taps of all the group 1 will be Restored and selected for equalization. Therefore, all previously unselected taps have a chance to be restored, which will enhance the performance of the decision feedback equalizer 10.

It should be noted that the preset values set in the feedforward filter 102 and the feedback filter 104 may be different from each other. In addition, the branching coefficient of the feedforward filter 102 lacks a tap coefficient greater than the first preset value, but is adjacent thereto The plurality of taps of the group having a tap coefficient greater than the first preset value are taps adjacent to the adjacent group, and the lack of any of the feedforward filters 102 is greater than the first preset value. The tap coefficient, but the number of taps of the adjacent group having a tap coefficient greater than the first preset value is less than m, and preferably less than m/2; the lack of any of the feedback filters 104 is greater than The tap coefficients of the second preset value, but the taps of the adjacent group but greater than the tap coefficients of the second preset value are taps adjacent to the adjacent group, and the feedback The number of taps in any group of filters 104 that are less than the tap coefficient of the second preset value but whose neighboring group has a tap coefficient greater than the second preset value is less than n, and preferably less than n/2.

In addition, the present invention also includes the tap/group returnable decision feedback equalizer as shown in FIGS. 1 and 2, and uses the tap/group replies decision feedback as shown in FIG. Method 30.

Referring to FIG. 1, the decision feedback equalizer 10 includes a feedforward filter 102, a feedback filter 104, a subtractor 106, and a clipper 108. The feedforward filter 102 filters out a preamble signal t2 from an input t1. The subtractor 106 subtracts the preamble signal t3 from the preamble signal t2 to generate an equalization signal t4. The clipper 108 intercepts the equalized signal t4 to generate a decision output t5, and the decision output t5 is fed back to the decision feedback equalizer 105 and filtered to generate the post signal t3.

Referring to Fig. 2, the feedforward filter 102 has M ^* m taps divided into M groups, and each group has m taps. For example, a group of 0 has a tap 0, a tap 1, ..., and a tap m-1. On the other hand, the feedback filter 104 has N ^* n taps divided into N groups, and each group has n taps. For example, a group of 0 has a tap 0, a tap 1, ..., and a tap n-1. Each tap of the feedforward filter 102 or the feedback filter 104 has a corresponding tap coefficient.

In addition, the decision feedback equalizer 10 includes a selection unit (not shown) that selects all taps in the group of the feedforward filter 102 that have a tap coefficient greater than a first preset value, and selects the feedforward. And any group of the feedforward filter 102 is selected in any group of the filter 102, wherein the tap coefficient is not greater than the first preset value but the tap coefficient of the adjacent group is greater than the first preset value All taps of the family having a tap coefficient greater than a second preset value, and selecting a tap coefficient of any group of the feedback filters that is not greater than the second preset value but adjacent groups thereof A plurality of taps larger than the second preset value, and after the selection, the selected tap is used for the equalization operation. In the present specification, the selection unit may be implemented by a circuit, a program, or a combination of the two.

It should be noted that the first preset value set for the feedforward filter 102 and the second preset value set for the feedback filter 104 may be different from each other. In addition, the selected steps will be repeated for each ATSC data field, or for each predetermined number of ATSC data fields. Furthermore, the tap coefficients of any group of the feedforward filters 102 that are not greater than the first preset value, but whose tap coefficients of adjacent groups are greater than the first preset value are close to the phase a tap of a neighboring group, and the tap coefficient of any group of the feedforward filters is not greater than the first preset value, but the tap coefficient of the adjacent group is greater than the tap of the first preset value The number is less than m, preferably less than m/2; the tap coefficient of any group of the feedback filter 104 is not greater than the second preset value, but the tap coefficient of the adjacent group is greater than the second preset Value The tap is a tap close to the adjacent group, and the tap coefficient of any group of the feedback filters 104 is not greater than the second preset value, but the tap coefficient of the adjacent group is greater than the second pre- The number of taps of the value is less than n, preferably less than n/2.

The present invention has been described above with reference to the preferred embodiments thereof, and is not intended to limit the scope of the present invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

10‧‧‧Determined feedback equalizer

102‧‧‧ Feedforward filter

104‧‧‧Response filter

106‧‧‧Subtractor

108‧‧‧Cut cutter

T2‧‧‧leading signal

T1‧‧‧ input

T3‧‧‧post signal

T4‧‧‧ Equalization signal

T5‧‧‧Judgement output

30‧‧‧Split/group can reply to the judgment feedback equalization method

S301~S307‧‧‧Steps

1 is a schematic diagram of a prior art decision feedback equalizer; FIG. 2 is a schematic diagram of the feedforward filter and the feedback filter of FIG. 1; FIG. 3 is a taper according to an embodiment of the present invention/ The group can reply to the flow chart of the decision feedback equalization method.

30‧‧‧Split/group can reply to the judgment feedback equalization method

S301~S307‧‧‧Steps

Claims (12)

A tap/group-recoverable decision feedback equalizer for a tap/group-revivable decision feedback equalizer, wherein the equalizer includes a feedforward filter (feed-forward filter) and a feedback filter, the feedforward filter includes a plurality of taps divided into M group groups, and the feedback filter includes a plurality of sub-groups divided into N groups a tap, wherein each of the N groups has n taps, and each of the M groups has m taps, wherein M, N, m, and n are positive integers greater than 2, and the method includes: The taps generate respective tap coefficients; all taps of any group of the feedforward filters having a tap coefficient greater than a first preset value are selected, and the tap coefficients of any group of the feedback filters are selected to be greater than a tap of a second preset value; selecting a tap coefficient of any group of the feedforward filters that is not greater than the first preset value, but a tap coefficient of the adjacent group is greater than the first preset a number of taps of the value, and selecting the feedback filters a plurality of taps in the group having a tap coefficient not greater than the second predetermined value but having a tap coefficient of the adjacent group greater than the second preset value; and using the selected taps to perform Equalization. A tap/group replies to a decision feedback equalization method for a tap/group retrievable decision feedback equalizer as described in claim 1 of the patent application, wherein any group of the feedforward filters is selected The tap coefficient is not large The step of the first preset value, but the tap coefficient of the adjacent group is greater than the first preset value, the step further includes: approaching the tap coefficient having the tap coefficient greater than the first preset value A tap is selected from the group of adjacent groups. A tap/group replies to a decision feedback equalization method for a tap/group replies to a decision feedback equalizer as described in claim 2, wherein the feedforward filter is in any group of groups The number of taps whose connection coefficient is not greater than the first preset value but whose tap coefficient of the adjacent group is greater than the first preset value is less than m/2. A tap/group replies to a decision feedback equalization method for a tap/group retrievable decision feedback equalizer as described in claim 1 of the patent application, wherein any group of the feedforward filters is selected The step that the tap coefficient is not greater than the second preset value but the tap coefficient of the adjacent group is greater than the second preset value further includes: having a tap coefficient greater than the first A tap is selected from a group of adjacent groups of two preset values. A tap/group replies to a decision feedback equalization method for a tap/group retrievable decision feedback equalizer as described in claim 4, wherein the tap coefficients of any group of equal feedback filters are The number of taps that are not greater than the second predetermined value but whose tap coefficients of adjacent groups are greater than the second preset value are less than n/2. The tap/group replies to the decision feedback equalization method for the tap/group replies to the decision feedback equalizer as described in claim 1 of the scope of the patent application, wherein the selected steps are for each high-order television system committee ( The ATSC) data field, or repeated for each predetermined number of ATSC data fields. A tap/group replies to a decision feedback equalizer, comprising: a feedforward filter for filtering a preamble signal from an input, The feedforward filter has a plurality of taps divided into M groups, wherein the M groups each have m taps, and both M and m are positive integers greater than 2; a subtractor is used to The preamble signal outputted by the feed filter is subtracted from a post signal to generate an equalizer output; a clipper is used to cut the equalizer output into a decision output; and a feedback filter is used for Filtering the decision output into the post-signal, and the post-signal is fed back to the subtractor, wherein the feedback filter has a plurality of taps divided into N groups, wherein the N groups each have n points a connector, and N and n are both positive integers greater than 2; and wherein the tap/group replies to the decision feedback equalizer selects the feed coefficient of the group of the feedforward filters to be greater than a first preset For all taps of the value, select a branch of any one of the feedforward filters that has a tap coefficient that is not greater than the first preset value, but whose tap coefficients of the adjacent group are greater than the first preset value Connector, select the feedback filter, the tap coefficient of any group of groups is greater than a second pre- All taps of the set value, and selecting a number of the group of the feedback filters that the tap coefficient is not greater than the second preset value, but the tap coefficients of the adjacent group are greater than the second preset value Taps, and the use of the selected taps for equalization. The tap/group can be returned to the decision feedback equalizer as described in claim 7 wherein the tap coefficients of any group of the feedforward filters are not greater than the first preset value but adjacent thereto A tap of the group having a tap coefficient greater than the first preset value is a tap selected adjacent to the adjacent group having a tap coefficient greater than the first preset value. The tap/group can be returned to the decision feedback equalizer as described in claim 8 wherein the tap coefficients of any group of the feedforward filters are not greater than the first preset value but adjacent thereto The number of taps of the group having a tap coefficient greater than the first preset value is less than m/2. The tap/group can be returned to the decision feedback equalizer according to claim 7 of the patent application scope, wherein the tap coefficient of any group of the feedback filters is not greater than the second preset value, but the adjacent group is The tap having a tap coefficient greater than the second preset value is a tap selected adjacent to the adjacent group having the tap coefficient greater than the second preset value. The tap/group can be returned to the decision feedback equalizer as described in claim 10, and the tap coefficient in any group of the feedback filter is not greater than the second preset value, but the adjacent group is The number of taps whose tap coefficient is greater than the second preset value is less than n/2. The tap/group can be returned to the decision feedback equalizer as described in claim 7 wherein the input signal is an ATSC field, and the tap is in each ATSC data field, or at each reservation. The number of ATSC data fields is repeatedly selected.