JPS6373744A - Phase control system - Google Patents

Abstract

PURPOSE:To surely attain phase control after the completion of hit, by providing a comparator which sends only the output of a square unit beyond a threshold value, and a decision circuit which decides the output of the comparator, and outputs a third error signal only when the hit is generated in a reception signal. CONSTITUTION:Immediately after the hit, a signal (j) outputted through the square unit 5, the comparator 6, and a signal sending part 13 is four-value decided at a second decision circuit 7, and a decided output (k) is selected at a selector 8, and a selected signal (k) is sent to a carrier phase controller 3 through a signal sending part 12 as an error signal (e). At this time, the control operation of the carrier phase controller 3 is corrected. Furthermore, when the output (n) of a level detector 1 outputs a level 1, a multivalued error signal (g) outputted from a first decision circuit 4 is inputted to the carrier phase controller 3, through the selector 8, and the signal sending part 12, as the error signal (e). In this way, it is possible to surely control a rotary phase after completing the hit of the reception signal, preventing the rotation of a carrier due to phase jitter, or frequency offset, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a data transmission device using a multilevel quadrature amplitude modulation method, and particularly relates to a phase control method. The phase control method is the fifth
The one shown in the figure is known.

A conventional example will be explained below with reference to FIG. The demodulated received signal a is input to the automatic equalizer 2, and the signal output from the automatic equalizer 2 is input to the carrier phase controller 3, and the received signal a is output from the carrier phase controller 3. The signal C is manually inputted to the judgment circuit 4. The 0 judgment circuit 4 judges which data point of the transmission signal the demodulated received signal a corresponds to, and compares this judged data point with the demodulated signal (received signal & ), an error signal is generated from the data points, and the error signal is output to the automatic equalizer 2 and the carrier phase controller 3. The automatic equalizer 2 corrects taps based on the error signal dK, and equalizes amplitude distortion and group delay distortion. When the carrier phase controller 3 receives the error signal e, it compensates for phase errors due to frequency offset, phase jitter, and the like. The level detector l outputs error signals d and e to the automatic equalizer 2 and the carrier phase controller 3 when a momentary interruption of the received signal a occurs.
It works to make it zero. At this time, the tap of the automatic equalizer 2 and the parameters of the phase controller 3 are held in the state before the momentary interruption while the momentary interruption occurs.

After recovery from the instantaneous interruption, the level detector 1 returns to the state BK before the instantaneous interruption occurred. That is, the level detector 1 prevents the control system of the receiving section (not shown) from running out of control by controlling the input of each error signal d, e to the automatic equalizer 2 and the phase controller 3 during signal interruption. .

(Problems to be Solved by the Invention) In the conventional carrier phase control method described above, when a momentary signal interruption occurs, the phase of the phase controller 3 immediately before the momentary interruption does not necessarily apply to the received signal immediately after recovery from the momentary interruption. However, it may not always be equalized. If the momentary interruption occurs for a short period of time, equalization can be performed using a method using the level detector 1. but,
In the case of an instantaneous interruption of a slightly longer time, the carrier amplitude distortion and carrier group delay distortion hardly change, but during the instantaneous interruption, the phase jitter and the frequency offset estimated by the carrier phase controller 3 change. In some cases, the phase rotation becomes large due to an error.In data transmission using multilevel data quadrature amplitude modulation, the distance between adjacent data points is short, so the difference between adjacent data points immediately after recovery from a momentary power loss is If the phase rotates,
This has the disadvantage that correct judgment cannot be made, and in this case, the control system of the receiving section goes out of control.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a phase control method that reliably controls the phase even after the momentary interruption of the received signal occurs.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the above objects, the present invention provides means for determining a received signal and determining an ml error signal and a second error signal. a first determination circuit that outputs;
an automatic equalizer for equalizing amplitude distortion and delay distortion of the received signal based on the first error signal; and a phase correcting phase error due to jitter or the like in the received signal based on the second error signal. A phase control system comprising: a controller; and a level detector that blocks output of the first and second error signals only when an instantaneous interruption of the received signal is detected; a comparator that compares the output of the squarer with a preset threshold and sends out only the output of the squarer that is equal to or higher than the threshold; and when the received signal is momentarily interrupted by determining the output of the comparator. only the second outputs the third error signal
and a selector that sends the third error signal to the phase controller at least while the received signal is momentarily interrupted, and receives the third error signal when the received signal is momentarily interrupted. It is characterized in that the phase controller is activated only when

(Example) Next, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. The level detector l outputs a level I01 to a first output signal m and a second output signal n, respectively, when the level of the input signal a suddenly decreases. The first output signal m is set to level '1° when the level of the input signal a, which has decreased, returns to the level before the decrease. The second output signal n is set to level 111 after a predetermined period of time after the first output signal m returns to level 11@. Focusing on the error signal d input to the automatic equalizer 2, when a momentary interruption of the signal a occurs, the error signal d input via the level detector 1 and the error sending section 11 is set to level 101. .

At this time, the tap of the automatic equalizer 2 is held until the instantaneous interruption ends.

When the momentary interruption ends, the error signal f is input from the first determination circuit 4 to the error sending section 11. This error signal f is given to the automatic equalizer 2 as an error signal d.

The tap built into the automatic equalizer 2 holds the state before the instantaneous interruption during the interruption, and the automatic equalizer 2 operates normally based on the error signal fK input after the instantaneous interruption ends.

On the other hand, the error signal e input to the carrier phase controller 3 is set to the level 'O''K at the moment of momentary interruption, and prohibits the control operation of the phase controller 3.This state is held until the momentary interruption ends.Signal When the transmitter 13 receives the received signal C, which is a multilevel data signal, the transmitting unit 13 performs a second four-level judgment on the signal j excluding data with an amplitude smaller than a predetermined threshold level.
It is sent to the determination circuit 7. The second determination circuit 7 outputs the error signal output k to the selector 8. Next, when the output signal n of the level detector 1 reaches the level "1"K, the selector 8 is operated to switch the error signal e to the error signal g output from the first determination circuit 4.

Assume now that a 64-value input signal a is input to the automatic equalizer 2, and that the automatic equalizer 2 and the carrier phase controller 3 are operating normally. If the input signal aO [interruption occurs in this state, the demodulated signal C that passes through the automatic equalizer 2 and the carrier phase controller 3 and is output will be as shown in the eye pattern in Fig. 2 immediately after the interruption ends. The phase of the carrier may rotate due to phase jitter or frequency offset estimation error of the carrier phase controller 3. That is, conventionally, in the eye pattern as shown in FIG. 2, the output signal C of the carrier phase controller 3
If the phase rotates by more than 10', it becomes impossible to recognize data points that match each other, and the control system of the receiver (not shown) may go out of control. In this method, immediately after a momentary interruption, the signal jt outputted through the squarer 5, the comparator 6, and the signal sending section 13--the second judgment circuit 7 performs a four-value judgment, and the judgment output k is outputted by the selector 8. The selected output k is sent to the carrier phase controller 3 via the signal sending section 12 as an error signal e. At this time, carrier phase controller 3
control behavior is modified. That is, the carrier phase controller 3
The zero output C is corrected to an eye pattern as shown in FIG. Furthermore, when the output n of the level detector 1 outputs a level 11', the multi-value error signal g output from the first determination circuit 4 is transmitted to the carrier phase controller 3 via the selector 8 and the signal sending section 12. , is input as an error signal e. In this way, the demodulated signal C of the carrier phase controller 3 is finally
In this case, a 64-value eye pattern as shown in FIG. 4 is reproduced.

Next, each error signal f of the determination circuit 4 and the determination circuit 7,
To explain g and k, if it corresponds to the demodulated signal decoded signal data point dn at a certain point, the error signal f1 at that point and the error signal g are each expressed as the following equation using an and dn. .

Here, an and dn are treated as complex data.

f = dn -a n g= -Im (an X ;n'/I dn l"
) Also, the output signal of the second determination circuit 7 is the same as the output signal g of the first determination circuit 4. The error signal f is a complex number.

(Effects of the Invention) As described above, according to the present invention, even if a momentary interruption occurs in the received signal, rotation of the carrier due to phase jitter, frequency offset, etc. is prevented, and after the momentary interruption of the received signal ends, This has the effect of reliably controlling the rotational phase.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an eye pattern diagram of the output signal of the carrier phase controller immediately after a momentary interruption, and Fig. 3 is a four-value judgment of the eye pattern in Fig. 2. A modified eye pattern diagram, FIG. 4 is an eye pattern diagram obtained by modifying the eye pattern of FIG. 3 by 64-value determination, and FIG. 5 is a block diagram showing a conventional example. 1... Level detection circuit, 2... Automatic equalizer, 3...
・Carrier phase controller, 4...Multi-value judgment circuit, 4...
Squarer, 6... Comparator, 7... 4 value judgment circuit,
・Selector 0 Figure 2 Figure 3

Claims (1)

[Claims] A first determination circuit that determines a received signal and outputs a first error signal and a second error signal; and a first determination circuit that determines the amplitude distortion and delay of the received signal based on the first error signal. an automatic equalizer that equalizes distortion; a phase controller that corrects a phase error due to jitter or the like of the received signal based on the second error signal;
A phase control method comprising: a level detector that blocks output of the first and second error signals only when a momentary interruption of the received signal is detected; a squarer that squares the received signal; and the squarer a comparator that compares the output of the comparator with a preset threshold value and sends out only the squarer output that is equal to or higher than the threshold value; a second determination circuit that outputs the second error signal; and a selector that sends the third error signal to the phase controller at least while the received signal is momentarily interrupted; A phase control method that operates the phase controller only when the signal is being received.