JPH01218218A - Automatic equalizer - Google Patents

Abstract

PURPOSE:To obtain an equalizer which does not exist at the sampling phase and has a stable pull-in characteristic by providing a means to control a weight coefficient based on the self correlation coefficient of a transversal filter output. CONSTITUTION:A reception base band signal inputted from an input terminal 1 is inputted to a transversal filter (Tf)2. Respective taps of a Tf2 are connected respectively through weight coefficient devices 31-3n to an adder 4, the output of the adder 4 becomes the output of an adaptive type Tf and inputted to an arithmetic part 5, a deciding device 7 and an error signal generating circuit 8. By the arithmetic part 5, the self-correlation coefficient of the output waveform from the adder 4 is calculated, and a first control circuit 6 controls the weight coefficient devices 31-3n based on the arithmetic result from the arithmetic part 5. On the other hand, the output of the deciding device 7 is given to the circuit 8 and an output terminal 11, the output of the circuit 8 is given to a second control circuit 9 and further, the output of the Tf2 is added to the circuit 9. The output is given through a switch 10 to the coefficient devices 31-3n toward the circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic equalizer, and particularly to an automatic equalizer.
d rate: transmission rate).

[Conventional technology]

Conventionally, a transparsal type automatic equalizer has been known as an automatic equalizer applied to a received signal sampled at baud rate (for example, Digital Filter Design, Takebe, Tokai University Press, 1986). ).

After the traditional automatic equalizer regenerates the data.

An error signal is created and the weighting coefficient of the transversal filter is controlled to minimize this error signal.

Margin below By the way, in the automatic equalizer described above, if data reproduction is incorrect, the error signal also becomes incorrect information, and as a result, the weighting coefficient of the transversal filter becomes defective, and the entire automatic equalizer There is a problem that the characteristics of the device deteriorate.

The automatic equalizer of the present invention includes an adaptive transformer filter that operates on a data-rate sampled input signal, an arithmetic unit that calculates an autocorrelation coefficient of the output of the transformer filter, and A first control circuit that controls the weighting coefficient of the transversal filter based on the autocorrelation coefficient, a data judgment circuit that acts on the output of the transversal filter, and a judgment result of the transversal filter output and the data judgment circuit. an error signal generation circuit that takes the difference between the two and sends out an error signal; a second control circuit that receives this error signal and the contents of the taps of the transformer/gusal filter and controls the weighting coefficient; The transversal filter is characterized by having a switch for switching between supplying either the control circuit output or the second control circuit output to the transversal filter.

〔Example〕 Next, the present invention will be explained with reference to examples.

Referring to FIG. 1, an input terminal 1 receives a received baseband signal distorted by a transmission line, and this received baseband signal is input to an n-tap transversal filter 2. Transversal filter 20 interval is Baud
rate is the sample interval. Each tap of the transversal filter 2 has a weighting coefficient unit 31 to 3.
connected to n.

The weighting coefficient units 31 to 3n are connected to an adder 4, and the output of the adder 4 becomes the output of a so-called adaptive transversal filter. The output signal of the adder 4 is sent to the arithmetic unit 59 and the determiner 7.
．． and is input to the error signal generation circuit 8. The calculation unit 5 calculates the autocorrelation coefficient of the output waveform of the adder 4, ff1H>, ) and the output waveform of the Lance Parsal filter.

The calculation unit 5 is connected to a first control circuit 6, and the first control circuit 6 is connected to weighting coefficient units 31 to 3n via a switch 10. The first control circuit 6 then operates based on the calculation result from the calculation section 5.

Controls weighting coefficient units 31 to 3n.

On the other hand, the output (judgment result) of the determiner 7 is output to the error signal generating circuit 8.
and is applied to the output terminal 11. The output (error signal) of the error signal generation circuit 8 is sent to the second control circuit 9
Furthermore, each tap output of the transversal filter 2 is applied to a second control circuit 9, and the output of the second control circuit 9 is applied to a weighting coefficient unit 3 via a switch 10.
1 to 3n.

Here, control of the weighting coefficient of the transversal filter in the above-mentioned equalizer will be explained.

For example, at time 9 mT, let fm be the sample value of the output waveform from the transversal filter.

The calculation unit 5 performs the calculation shown in equation (1).

Pl-E (fm-fITl+, fm-frn-10, 2fm-f□-2) ... (1) Here, E is the code indicating the time average, fm-1 is the time (nr-1)T The sample value at , fm-2 is the sample value at time (m-2)T, and 2 is the coefficient for k, . The first control circuit 6 is provided with a plurality of weighting coefficients in advance.
, select an appropriate weighting factor based on the value of .

Here, FIG. 2 shows the value of Pl when the i-th and i-1th weighting coefficients are selected from among the plurality of weighting coefficients. As shown in FIG. 2, in the case of the i-1th weighting coefficient, Pl is smaller than the threshold value 1, and in the case of the i+1th weighting coefficient, P1 is larger than the threshold value 1. Now, if P is smaller than the threshold 1, select the weighting coefficient one higher than the current weighting coefficient, and if Pl is larger than the threshold 1, select the weighting coefficient one lower than the current weighting coefficient. If the first control circuit 6 operates to select the i-th or i-1-th weighting coefficient from among the plurality of weighting coefficients. Furthermore, the value of P calculated as shown in equation (1) is independent of the sampling phase as shown in FIG. You can do it right.

Next, as shown in FIG. 3, a case will be described in which two threshold values are used. The first control circuit 6 is P.

If the value of P is larger than threshold 3, select the weighting coefficient that is one level lower than the current weighting coefficient, and if the value of P is between threshold 3 and threshold 2, select the current weighting coefficient. If no change is made and the value of Pl is smaller than threshold 2, a weighting factor one higher than the current weighting factor is selected. If the first control circuit 6 operates as described above, it is possible to select the first weighting coefficient from among the plurality of weighting coefficients.

As described above, the first control circuit 6 controls the two weighting coefficient units 31 to 3n without using the determination result of the output from the adder 4 by the determiner 7, that is, the determination result of the output from the transversal filter. This eliminates the instability of retraction.

Furthermore, since the control of the weighting coefficients does not depend on the sampling phase, it can be applied to automatic equalization of baud rate sample systems.

On the other hand, the output from the adder 4 is given to the determiner 7, where it is determined. For example, transmission information is estimated. Based on this determination result and the output from the adder 4, the error signal generation circuit 9 supplies an error signal to the second control circuit 9. The second control circuit 9 is given tap information of the transversal filter 2 in addition to the error signal.
controls the weighting coefficient units 31 to 3n based on these error signals and tag information. Switching between the first control circuit 6 and the second control circuit 9 is performed by a switch 10, and in the initial stage (transitional period) of information reception, the weighting coefficient units 31 to 3n are switched in the first control circuit 6. controlled.

After that (stationary period), the second control circuit 9 uses the weighting coefficient unit 31
~3n is controlled. Although some code amount interference occurs in the weighting coefficient control by the first control circuit 6, the equalization accuracy is improved by switching to the weighting coefficient control by the second control circuit 9.

〔Effect of the invention〕

As explained above, the automatic equalizer of the present invention has a stable drawing characteristic that is independent of the sampling phase.
Furthermore, it has the advantage of being highly effective in suppressing code amount interference.

The block diagrams shown in the blanks below, FIG. 2, are diagrams for explaining one example of weighting coefficient control, and FIG. 3 is a diagram for explaining another example of weighting coefficient control.

1...Input terminal, 2...Transversal filter.

3... Weighting factor unit, 4-... Adder, 5... Arithmetic circuit.

6... First control circuit, 7... Determiner, 8... Error signal generation circuit, 9... Second control circuit, 10...
switch.

11... Output terminal.

Claims (1)

[Claims] 1. In an automatic equalizer used for baseband data transmission, a transversal filter to which an input signal sampled at a baud rate is input, and an arithmetic unit that calculates an autocorrelation coefficient of an output from the transversal filter;
a first control circuit that controls a weighting coefficient of the transversal filter based on the autocorrelation coefficient from the calculation unit; a data determination circuit that acts on the output of the transversal filter; and an output of the transversal filter. an error signal generation circuit that calculates a difference between determination results by the data determination circuit and outputs an error signal; and a second control circuit that receives the error signal and information from the taps of the transversal filter and controls the weighting coefficient. and the first
An automatic equalizer comprising: a control circuit; and a switch connecting either one of the second control circuits to the transversal filter.