JPH0691480B2 - Method of setting filter coefficient vector of adaptive transversal filter in waveform equalizer using adaptive transversal filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of setting a filter coefficient vector of an adaptive transversal filter in a waveform equalizer using an adaptive transversal filter, and in particular in the field of digital transmission, adaptive FIR ( The present invention relates to a method of setting a filter coefficient vector of an adaptive transversal filter in a waveform equalizer using an adaptive transversal filter that performs waveform equalization using a (transversal) filter.

[Prior Art] In the field of digital transmission or recording / reproducing technology, signal deterioration may occur due to a data error due to the quality of the transmission line and the characteristics of the recording / reproducing apparatus, and waveform equalization is performed in the middle or end of the transmission line. Is essential.

FIG. 1 shows the configuration of a digital recording / reproducing system.

In FIG. 1, the code a _K is the information sequence to be recorded, usually 0o.
It is a binary symbol sequence of r1. Block 11 is a transmission filter that converts the information of a _K into an appropriate waveform, and its output x _K
Is recorded on a recording medium such as a magnetic disk shown in block 12. During reproduction signal y _K is by utilizing the output w _K through the amplifier shown in block 13 by the reading system to restore the original sequence a _K. However, the output w _K is
It is highly possible that the waveform is distorted due to the dynamic characteristics of 2 and 13 and noise, and as a result the original sequence a _K may not be restored correctly. In order to compensate for such a phenomenon, the equalizer 14 is used to equalize the waveform distortion, and the equalized waveform z _K is used to correctly restore the original data sequence a _K.

As the equalizer 14, multiple unit delay elements are connected in a conventional manner,
An adaptive FIR filter is often used in which each tap output is amplified with an appropriate gain and added to obtain an equalized output. The gain of each tap, that is, the filter coefficient is determined in the automatic equalizer based on a predetermined computer algorithm.

However, in the conventional filter coefficient determination, the coefficient is obtained by the method of approximating to the optimal solution by the steepest descent method which is a kind of iterative iteration method. There is no guarantee, and even if it converges, the amount of calculation may be considerable.

[Object] The present invention has been made in view of the above problems, and is an adaptive transversal that can obtain stable convergence with a small amount of calculation and processing time and can obtain desired equalization characteristics at high speed. An object of the present invention is to provide a method of setting a filter coefficient vector of an adaptive transversal filter in a waveform equalizer using a filter.

[Configuration of the Invention] In order to achieve the above object, the present invention has a filter coefficient vector h [h ₁ , h ₂ , ..., Of an adaptive transversal filter in a waveform equalizer using an adaptive transversal filter. h _N ], the root mean square of the error between the equalization output signal of the adaptive transversal filter and the equalization target signal prepared in advance is adopted as the evaluation function J of the filter coefficient vector h, and the evaluation function J is filtered. The coefficient vector h is expressed as a quadratic form, and the initial value of the filter coefficient vector h is set to h ₀ so that the value of the evaluation function J expressed as a quadratic form of the filter coefficient vector h becomes an appropriate value h ₁ , h ₂ , ..., h _N are adopted by the sequential iterative calculation.

[Examples] Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

FIG. 2 shows a block diagram of the waveform equalizer according to the present invention. The filter unit connects unit delay devices 1 in N stages in series, and outputs each tap output thereof by a multiplier 2 to obtain a coefficient h _0.
And it is configured to sum the to the adder 4 amplified by to h _N. In FIG. 2, x _n is an input signal to be equalized that has been distorted in the transmission system, y _n is an output signal when x _n is input to the filter, and d _n is an equalization target signal prepared in advance . Each filter coefficient h _{0 to} h _N is determined based on the input signal of each multiplier 2 by evaluating the error between the filter output signal y _n and the equalization target signal d _n by the control unit 3 composed of a microcomputer or the like. It

Mean square E of the error e _n of y _n and d _n as an evaluation criterion [e _n ^2] =
If J is adopted, J should be minimized Is given by

The symbols are defined as follows.

Since the evaluation standard is That is Can be shown as a quadratic form for.

In (3), minimize J Match.

Since J can take an extreme value, the following condition is satisfied.
That is, The following shows what can be obtained by linear combination of role vectors.

From equation (3) To be defined as

The h that minimizes J in the equation (5) is sequentially obtained with the initial value h ₀ .

To decide.

If J (9) is differentiated with respect to α ₀ by using Taylor expansion approximation as in the above equation and is set to 0, When the above operation is repeated, the following procedure is expressed.

By storing this procedure in the memory as a program of the control unit 3 and repeating the calculation, the coefficients of the multiplier 2, h ₀ , h ₁ , ..., H _N can be sequentially obtained.

Now, it is obtained by repeating the procedure from i) to v) (N + 1) times. Clarify the nature of.

Is conjugate with respect to the matrix A, that is, first-order independent, so (N +
1) dimensional space It can be expressed by the union binding.

Becomes

It became clear that the evaluation criterion J should be minimized.

Therefore, the correction direction of the coefficient vector is set in the same direction as the vector conjugate with the covariance matrix of the input signal sequence, and the above i) to
By repeating the procedure of v) in the control unit 3, the optimum coefficient vector of the multiplier 2 is obtained by a finite number of iterations, and the equalizer can be configured.

[Effect] As is clear from the above description, according to the present invention, the filter coefficient vector h [h ₁ , h ₂ , ..., Of the adaptive transversal filter in the waveform equalizer using the adaptive transversal filter is used. h _N ], the root mean square of the error between the equalization output signal of the adaptive transversal filter and the equalization target signal prepared in advance is adopted as the evaluation function J of the filter coefficient vector h, and the evaluation function J is filtered. The coefficient vector h is expressed as a quadratic form, and the initial value of the filter coefficient vector h is set to h ₀ so that the value of the evaluation function J expressed as a quadratic form of the filter coefficient vector h becomes an appropriate value h ₁ , h _2, ..., because it uses the sequentially repeated operation and determined configure h _N, determines the filter coefficient reliably and stably by a small amount of calculation and processing time, where It is possible to provide a waveform equalizer having high reliability can be obtained of the filter characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a digital recording / reproducing system, and FIG. 2 is a block diagram showing the configuration of a waveform equalizer according to the present invention. 1 ... Unit delay device, 2 ... Multiplier 3 ... Control unit, 4 ... Adder

Claims (2)

[Claims] 1. A method of setting a filter coefficient vector h [h ₁ , h ₂ , ..., H _N ] of an adaptive transversal filter in a waveform equalizer using an adaptive transversal filter, wherein: As the evaluation function J, the mean square of the error between the equalized output signal of the adaptive transversal filter and the equalization target signal prepared in advance is adopted, and the evaluation function J is expressed as a quadratic form of the filter coefficient vector h. With the initial value of the vector h as h ₀ , h ₁ , h ₂ , ..., H _N are sequentially repeated so that the value of the evaluation function J expressed as a quadratic form of the filter coefficient vector h becomes an appropriate value. Method of setting filter coefficient vector of adaptive transversal filter in waveform equalizer using adaptive transversal filter characterized by calculation . 2. A filter coefficient vector h is sequentially iteratively calculated using a vector Ci that is conjugate to a covariance matrix A of an input sequence X of an adaptive transversal filter as a filter coefficient correction vector. A method of setting a filter coefficient vector of an adaptive transversal filter in a waveform equalization device using the adaptive transversal filter according to claim 1.