JPS6363129B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic waveform equalizer such as a transversal automatic equalizer.

Generally, when high-speed data transmission is performed using QAM modulation or phase modulation, the transmission waveform is subjected to line waveform distortion, resulting in intersymbol interference. For example, when waveform distortion is caused by selectivity fading in a wireless line, this waveform distortion changes from moment to moment, so transversal technology automatically monitors this distortion at all times and equalizes the waveform to prevent intersymbol interference. It is useful to introduce a waveform equalizer such as a waveform automatic equalizer.

FIG. 1 shows a block diagram of the basic configuration of a transversal automatic equalizer when the ZF (zero-focusing) method is used as the control algorithm.
In the figure, 1 is a delay element for the time slot, 2 is a variable attenuator that is not directly related to the equalization effect and only changes the amplitude of the input signal (main signal), and 3 and 4 are echoes that equalize intersymbol interference. A variable attenuator that changes the amplitude and polarity of the signal (a signal weighted to lead or lag in time from the main signal); 5 is an adder; 6 is a discriminator; 7 is an error signal detector; 8 is a variable attenuator control It is a circuit.

Briefly explain the operation. a plurality of delay elements 1;
The main signal taken out from the center tap of the delay line connected in a subordinate manner is passed through variable attenuator 2, and the signal taken out temporally ahead or behind the main signal is passed through variable attenuators 3 and 4. The echo signals are sent to the adder 5, where their waveforms are equalized. This equalized output is input to a discriminator 6, and an identification signal is output from the discriminator 6. The error signal detection 7 compares the equalized output and the identification signal,
Detects and outputs errors. When using the ZF method, the control circuit 8 receives the error detection signal from the error detector 7 and the identification signal from the discriminator 6, controls the variable attenuators 2, 3, and 4 based on these, and controls the variable attenuators 2, 3, and 4 to obtain a predetermined signal. Ensure that waveform equalization is performed.

Now, if the transversal type automatic waveform equalizer as described above becomes uncontrollable due to waveform distortion that cannot be equalized or an abnormality other than the equalizer, the output of the equalizer tends to be worse than the input signal. However, since the equalizer is inserted into the main transmission line, it poses a serious problem. In addition, especially in the case of the ZF method, control is performed using the equalized output signal, so when the waveform distortion that cannot be equalized or the abnormality other than the equalizer disappears, and the equalizer is in a state where it can be equalized, control is performed. The drawback is that the response time from a disabled state to a normal equalization state is long.

This invention was made in order to eliminate the drawbacks of the conventional waveform equalizer as described above, and therefore, the purpose of this invention is to solve the problem when equalization becomes impossible.
without making the equalizer output worse than the input signal.
Another object of the present invention is to provide an automatic equalization device that can quickly return to a normal equalization state when the impossible-to-equalize state is resolved.

The main point of the configuration of the present invention is that in a conventional automatic waveform equalizer, an equalization failure detection circuit and an equalization failure detection signal from the circuit cause the control circuit to set initial values for all variable attenuators. and a variable attenuator initial value setting circuit that sets all the variable attenuators to their initial values while the non-equalization detection signal is being generated to prevent the equalization function from working, and cancels the initial value settings when the signal disappears. The point is that the equalization function is restarted.

Next, one embodiment of this invention will be described. For example, in the case of a transversal automatic equalizer with a baseband band input waveform, the waveform distortion in the IF band is not equalized, so even though the equalizer itself can equalize even larger distortions, the IF band waveform distortion is not equalized. The carrier reproduction function during demodulation stops due to distortion, and as a result, equalization becomes impossible. Therefore, in this case, the equalization failure detection circuit may be any circuit as long as it can monitor whether the carrier regeneration function is working normally. This detection circuit can be used because a carrier regeneration function monitoring circuit is often already added as a device monitoring circuit for the demodulator.

An embodiment of the present invention in this case is shown in a block diagram in FIG. In the figure, 9 is a carrier regeneration circuit, 10 is an equalization failure detection circuit, and 11 is a variable attenuator initial value setting circuit. To explain the operation, when the carrier regeneration function is stopped in the carrier regeneration circuit 9, the equalization failure detection circuit 10 generates an equalization failure signal, which activates the initial value setting circuit 11, causing the control circuit 8 to Set all variable attenuators to their initial values and stop automatic control of the variable attenuators. As an initial value, the attenuation amount of the main signal variable attenuator 2, which is not directly related to the equalization effect, is fixed to output a constant voltage, and the other variable attenuators 3 and 4 are set to the maximum attenuation amount. setting, and cut off the echo signal so that it does not output. As a result, the input signal appears on the output side as it is without being subjected to equalization. This initial value setting is the initial value when the transversal automatic equalizer starts equalization, so as soon as the impossible-to-equalize state is resolved, equalization starts from this initial value, so the equalization effect is immediately activated. is started.

In the embodiment, three variable attenuators are used, but in reality, a larger number of attenuators may be used as needed, and their outputs are added together in an adder. Needless to say, this process is subject to change.

As explained above, according to the present invention, by eliminating the erroneous equalization operation of the automatic waveform equalizer when equalization is impossible, further deterioration of the input signal is prevented from being output. Since the equalizer has its initial value set at that point, there is an advantage that the response time at the start of the equalization operation can be shortened, compared to a conventional device that starts equalization from a malfunction in which equalization is not possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of a conventional transversal automatic waveform equalizer, and FIG. 2 is a block diagram showing an embodiment of the present invention. Explanation of symbols: 1...delay element for one time slot, 2, 3, 4...variable attenuator, 5...adder,
6... Discriminator, 7... Error signal detector, 8... Variable attenuator control circuit, 9... Carrier regeneration circuit, 1
0...Unequalization detection circuit, 11...Variable attenuator initial value setting circuit.

Claims (1)

[Claims] 1. Consisting of a plurality of delay elements connected in a subordinate manner,
A delay line is provided with a plurality of output taps that take out input signals at fixed delay intervals, a plurality of variable attenuators each receive a delayed signal from each of the output taps, and the outputs of the variable attenuators are synthesized. an adder that generates an equalized output; an identification circuit that identifies the equalized output and generates an identification signal; and an error detector that generates an error signal based on the difference between the identification signal and the equalized output. , and a control circuit that controls the variable attenuator based on the error signal, the automatic waveform equalization device comprising: an equalization impossibility detector provided on the input side of the equalization device to detect the impossibility of equalization; and a variable attenuator initial value setting circuit that causes the control circuit to set all variable attenuators to initial values in response to the non-equalization detection signal from the circuit, and when the non-equalization detection signal is generated, An automatic waveform equalizer characterized in that all variable attenuators are set to initial values so that the equalization function does not work, and when the signal disappears, the initial value settings are canceled and the equalization function is restarted. .