JPS58117715A - Recursive filter type bridged tap equalizer - Google Patents

Abstract

PURPOSE:To attain stable equalizing lock-in, by generating a pulse to obtain a timing of correction, and regarding the amount of an input signal reaching a prescribed value as the incoming of an isolated wave. CONSTITUTION:An input signal X(t) receiving echo distortion of a bridged tap is subtracted at an adder 1 with an output y(t) delayed at a tapped delay line 2 and multiplied with tap coefficients C1-C4 at multipliers 3-1-3-4 and becomes an equalized output y(t). A pulse generating section 5 generates a pulse when the amount of change in the input signal reaches a prescribed value VH. This pulse is inputted to a delay generating section 6, where a timing pulse correcting the tap coefficient in response to each tap. Each tap coefficient is corrected with the timing pulse and output of the adder 1 to attain equalized locking.

Description

Detailed Description of the Invention (4) Technical Field of the Invention The present invention relates to a recursible filter type bridged tap equalizer, particularly to a recursible filter type bridged tap equalizer, which is provided on the receiving side of a signal line in which a bridged tap is present. The present invention relates to a filter-type bridged tap equalizer that extracts the correction timing for correcting tap coefficients to realize stable pull-in, and relates to a cursible filter-type bridged tap equalizer.

CB) Technical background and problems Recently, the concept of integrated service digital networks has been adopted, and digital signals are being carried over conventional telephone lines. Bridged taps have traditionally been installed on such signal lines so that they can be used no matter where the subscriber is installed.For this reason, when carrying the above-mentioned digital signals, the conventional The bridged tap reflection, which was hardly a problem in the audio frequency band, becomes a problem.

In order to eliminate the echo caused by the reflection, a bridged tap equalizer is provided at the receiving end of the signal line, and a rising wave is applied to perform automatic equalization to cancel the echo. In this case, a recursible filter type bridged tap equalizer is used, but the problem is to correctly extract the correction timing for correcting the tap coefficients.

That is, on the receiving side, it is safe to correctly extract the timing at which the solitary wave arrives, and thereby to correctly create the correction timing. In other words, on the receiving side, a signal containing an echo will be transmitted before equalization, and it is safe to correctly extract the arrival point of the solitary wave from such a signal and create the above timing. becomes. Even if a clock is simply generated using a PLL on the receiving side, there is a risk that the clock will be synchronized with the echo, which is not preferable.

(0) Object and Structure of the Invention The purpose of the present invention is to solve the above-mentioned problems. In order to equalize the echo signal when a signal of Suri Carsiple
A bridged filter is used to apply a solitary wave and automatically adjust the tap coefficients to equalize the echo.
The tap equalizer is equipped with a pulse generator that generates a pulse by assuming that a rising wave has arrived when the amount of change in the input signal reaches a predetermined value, and also generates a pulse from the pulse generator as described above. The present invention is characterized in that it is configured to be supplied to a delay generation section that generates a delay corresponding to the delay on the delay line, and that correction timing for correcting each of the above-mentioned tap coefficients is obtained based on the output from the delay generation section. This will be explained below with reference to the drawings.

(9) Embodiment of the invention FIG. 1 shows the configuration of an embodiment of the invention, FIG. 2 is an explanatory diagram illustrating a mode of equalization on the receiving side, and FIGS. 3 and 4 are respectively similar to FIG. 1. In FIG. 1, l is an adder, 2 is a tapped delay line,
3-1 to 3-4 are multipliers each having a tap coefficient C.
4''-1 to 4-4 are coefficient generators for obtaining tap coefficients (j); 5 is a pulse generator that extracts the arrival of a solitary wave and generates a pulse; 6
0 represents a delay generating section. In the figure, the rising wave applied at the transmitting end is added with a reflection from a bridged tap in the middle, and becomes an input signal shown as an input in the figure.

Multipliers 3-1 to 3- are applied to the input signal X↓(t).
The output from 4 is subtracted to obtain the output y (t), but
At this time, tap coefficients 01 to C4 to be supplied to multipliers 3-1 to 3-4 are selected and equalized so that the output (t) has substantially the same waveform as the rising wave applied at the transmitting end. will be carried out.

As described above, the waveform transmitted to the receiving side has a reflection component added to it before equalization. For this reason, it is difficult to correctly extract the arrival timing of rising waves. However, in the case shown in Figure 1, as shown in Figure 2, input signal 3: L(t) is considered to be zero when t≦-T, and the amount of change in the input signal is a predetermined value. When reaching vH, it is assumed that a rising wave has arrived. In other words, the pulse generating section 5 shown in FIG. 1 generates a pulse at point A shown in FIG. 2, and this pulse is supplied to the delay generating section. .

Letting the point A be t=00 point, t=T, , t=iT
,+T.

The output from adder 1 at each point of... is '+
(TI),'t (TI +T, ),..., then '+ (Tt) ='L (TI) -C+
”t (01'* (Tt +T,) = rL(T+
+Ttl −”s・'+ (Ts) −c, ZL (0
) g3(T, +T, +T,) =xL('r, +'r,
+T', )-cl-g.

It is given by x(TI+T,)-C,·g, (Tt>-C31 et al. 0).

In the case shown in FIG. 1, the timing at which tap coefficient 01 is corrected in the coefficient generating section 4-1 is delayed by T from the point //iA, and the output from the adder l is the above-mentioned g, ( TI), and this value is supplied via line 1, which correctly matches the principle for equalization in which the tap coefficient CI is corrected in the direction of making the '+(Tt) zero. Needless to say, in the coefficient generating section 4-2, the tap coefficient C! The timing for correcting is 9 timings delayed by (T++Tt) from point A, and the output from adder l at this time is ε* (TI+
This value is supplied via line J, and the tap coefficient C8 is corrected in the direction of making the εt (Tt '' T) zero.

In addition, the above '! (Tt), 't (Ts+Tt),
g, (T, + T, +Ts)... As can be seen from the formula, it is desirable to first correct the tap coefficient C0, then correct the tap coefficient C1, etc., but the first
The illustrated configuration satisfies this point as well. and,
By transmitting a solitary wave from the transmitting end at a predetermined period, the tap coefficients C,
C.... is corrected to the desired form, etc. 1
2% reduction is completed.

3 or 4 respectively show the delay generating section 6 shown in FIG. 1.
A modification example is shown. In FIGS. 3 and 4, the timing is given to the coefficient generating section 4-1 with a time delay of T, and the timing is given to the coefficient generating section 4-2 (
The timing is given with a time delay of T++Tt), and the delay generating section 6 functions substantially in the same way as the delay generating section 6 using the delay line shown in FIG.

(K) As described in detail, according to the present invention, the signal arrival point is correctly extracted from a signal that includes outside reflections, and the error 'r (
Tt ), 't (Tt +T!), ... It becomes possible to sequentially correct the tap coefficient CI, ``*, river, paying attention to the mountain.As a result, the equalizer integration can be carried out efficiently.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram illustrating a mode of equalization in a reception example, and FIGS. 3 and 4 are modified examples of the delay generation section shown in FIG. 1, respectively. shows. In the figure, 1 is an adder, 2 is a tapped delay, 3 is a multiplier, 4 is a coefficient generator, 5 is a pulse generator, and 6 is a delay generator. Patent applicant Fujitsu Limited

Claims (1)

[Claims] In order to equalize the echo signal when a broadband signal is applied to a signal line with bridged taps, a tapped delay line is provided, and the output is obtained by multiplying the output of each tap by a coefficient and subtracting it from the input. , in a bridged tap equalizer in which the cough output is input to the tapped delay line, a cursive filter is used, and the tap coefficients are automatically adjusted to equalize the echo by applying a rising wave, A pulse generator is provided that generates a pulse by regarding the arrival of a rising wave when the amount of change in the input signal reaches a predetermined value, and the pulse from the pulse generator is made to correspond to the delay on the delay line. The cartridge is configured to be supplied to a delay generation section that generates a delay, and correction timing for correcting each of the above-mentioned tap coefficients is obtained based on the output from the delay generation section. Equalizer.