JP3130578B2 - Quadrature amplitude modulation data receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is applied to a QAM data receiver which receives a QAM (quadrature amplitude modulated) signal as a reception signal and obtains a reception code. In particular, it relates to amplitude fluctuation canceling means.

[0002]

2. Description of the Related Art In a conventional example, when there is a fluctuation in the amplitude direction, the amplitude fluctuation is absorbed by an automatic gain controller (AGC) and an automatic equalizer. Further, there is a QAM receiver having a means for temporarily stopping the control of the automatic equalizer in order to prevent the automatic equalizer from diverging when the amplitude fluctuation is large.

[0003]

In such a conventional example, the amplitude fluctuation is corrected by the AGC and the automatic equalizer. However, the correction speed is relatively slow in order to prevent malfunction due to noise or the like in a steady state. Is set. Therefore,
There is a disadvantage that it takes a long time to correct the amplitude fluctuation, and a received code error occurs for a long time. Further, when the amplitude fluctuation is large, the automatic equalizer cannot follow up, and the automatic equalizer may diverge. Even if the receiver has a function to stop the control of the automatic equalizer to prevent the divergence of the automatic equalizer, if the amplitude fluctuation time is longer than the time when the control of the automatic equalizer is stopped, the automatic Gasifier diverges,
In addition, there is a disadvantage that errors in received codes cannot be reduced. The present invention eliminates such disadvantages.
An object of the present invention is to provide a quadrature amplitude modulation data receiver having means for reducing a data error due to a sudden amplitude fluctuation of a line.

[0004]

SUMMARY OF THE INVENTION The present invention provides an automatic gain controller for adjusting the level of a received signal, a demodulator for demodulating the received signal whose level has been adjusted by the automatic gain controller, and a demodulator for demodulating the received signal. A quadrature amplitude comprising: an automatic equalizer for equalizing distortion due to a telephone line included in the extracted signal; and a decoder for decoding a signal related to the signal equalized by the automatic equalizer to obtain received data. In a modulated data receiver, a first coordinate determining means for determining an output signal of the automatic equalizer as a predetermined data coordinate point, and an amplitude component of an error between an input signal and an output signal of the first coordinate determining means are extracted. A first amplitude error extracting means, an amplifier for providing an amplitude gain to the output signal of the automatic equalizer, a second coordinate determining means for determining the output signal of the amplifier to a predetermined data coordinate point, Input signal and output signal of judgment means A second amplitude error extracting means for extracting an amplitude component of an error of the attenuator, an attenuator for attenuating the amplitude of the output signal of the automatic equalizer, and a second attenuator for determining the output signal of the attenuator to a predetermined data coordinate point. Three coordinate determining means, third amplitude error extracting means for extracting an amplitude component of an error between an input signal and an output signal of the third coordinate determining means, and an output of the first coordinate determining means in response to a given command. A signal, a switch for giving either the output signal of the second coordinate determining means or the output signal of the third coordinate determining means to the decoder, and the output signal of the first amplitude error extracting means, the second amplitude error The absolute value of the output signal of the extracting means and the absolute value of the output signal of the third amplitude error extracting means are compared to specify the amplitude error determining means having the smallest error, and the amplitude error determining means corresponding to the specified amplitude error determining means is determined. Of the coordinate determination means A command to select a force signal characterized by comprising a switch control means for supplying to said switching device.

[0005]

With respect to the output signal of the automatic equalizer 3 of the quadrature amplitude modulation data receiver, the coordinates of the signal passing through the amplifier 6, the coordinates of the signal passing through the attenuator 9, and the coordinates of the signal as it is are determined. An error between the absolute value of each of the coordinate determination output signals and the amplitude value of each of the coordinate determination input signals is calculated, and a coordinate determination output signal that gives a coordinate determination result with the least error is selected and input to the decoder 14. I do. When the amplitude fluctuation is corrected by the automatic gain controller 1, a coordinate determination output signal for determining the coordinates of the signal as it is is selected, and the control is stabilized.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of this embodiment. In this embodiment, as shown in FIG. 1, an automatic gain controller 1 for adjusting a received signal level, and a demodulator 2 for demodulating a received signal.
Automatic equalizer 3 for equalizing line distortion, and automatic equalizer 3
A coordinate determination means 4 for determining the output signal of the coordinate data into predetermined data point coordinates; an amplitude error determination means 5 for extracting only an amplitude component among errors between an input signal and an output signal of the coordinate determination means 4;
An amplifier 6 for amplifying an output signal of the automatic equalizer 3; a coordinate determining means 7 for determining the output signal of the amplifier 6 to predetermined data point coordinates; and an error between an input signal and an output signal of the coordinate determining means 7 Amplitude error extracting means 8 for extracting only the amplitude component
An attenuator 9 for attenuating an output signal of the automatic equalizer 3; a coordinate determining means 10 for determining an output signal of the attenuator 9 to predetermined data point coordinates; an input signal and an output signal of the coordinate determining means 10; An amplitude error extracting means 11 for extracting only an amplitude component among errors of the above, a switch 12 for selecting and outputting one of the outputs of the coordinate determining means 4, the coordinate determining means 7 and the coordinate determining means 10, The switching unit 12 compares the absolute values of the output signals of the extraction unit 5, the amplitude error extraction unit 8, and the amplitude error extraction unit 11 and selects the coordinate determination unit with the smallest error.
And a decoder 14 for decoding the output signal of the switch 12.

That is, in this embodiment, as shown in FIG. 1, an automatic gain controller 1 for adjusting the level of a received signal;
A demodulator 2 for demodulating the received signal whose level has been adjusted by the automatic gain controller 1; an automatic equalizer 3 for equalizing distortion caused by a telephone line included in the signal demodulated by the demodulator 2; And a decoder 14 for decoding a signal related to the signal equalized by the equalizer 3 to obtain received data. Further, as a feature of the present invention, the output signal of the automatic equalizer 3 A coordinate judging means 4 for judging a data coordinate point, an amplitude error extracting means 5 for extracting an amplitude component of an error between an input signal and an output signal of the coordinate judging means 4, and an amplitude gain for an output signal of the automatic equalizer 3 , A coordinate determining means 7 for determining an output signal of the amplifier 6 to a predetermined data coordinate point, and an amplitude error extraction for extracting an amplitude component of an error between an input signal and an output signal of the coordinate determining means 7. Means 8 and output signal of automatic equalizer 3 An attenuator 9 for attenuating the amplitude, a coordinate determining means 10 for determining an output signal of the attenuator 9 to a predetermined data coordinate point, and an amplitude component of an error between an input signal and an output signal of the coordinate determining means 10 is extracted. And a switch 12 for providing one of the output signal of the coordinate determining means 4, the output signal of the coordinate determining means 7 or the output signal of the coordinate determining means 10 to the decoder 14 in accordance with a given command. And the absolute values of the output signal of the amplitude error extracting means 5, the output signal of the amplitude error extracting means 8 and the output signal of the amplitude error extracting means 11 are compared to identify the amplitude error determining means with the smallest error. And a switch controller 13 for giving a command to the switch 12 to select an output signal of the coordinate determiner corresponding to the specified amplitude error determiner.

Next, the operation of this embodiment will be described. When an amplitude fluctuation in which the amplitude fluctuates in the negative direction occurs on the telephone line, the amplitude error of the normally selected coordinate determination means 4 becomes large. Further, the amplitude error of the coordinate judging means 10 for judging the coordinates of the signal obtained by attenuating the output signal of the automatic equalizer 3 is further increased. However, coordinate determination means 7 for always determining the coordinates of a signal obtained by amplifying the output signal of automatic equalizer 3.
Is offset by the negative amplitude error of the line, and the switch control means 13 switches the switch 12 to the coordinate determination means 7.
Switch to output. Therefore, the input signal of the decoder 14 is a signal whose amplitude fluctuation has been corrected by the amplifier 6, and the error of the received code is small. Then, when the amplitude fluctuation is corrected by the automatic gain controller 1, the amplitude error of the coordinate judging means 4 becomes the smallest, and the switch 12 selects the output of the coordinate judging means 4. On the other hand, when an amplitude fluctuation in which the amplitude fluctuates in the positive direction occurs on the telephone line, the amplitude error of the normally selected coordinate determination unit 4 becomes large. Further, the amplitude error of the coordinate judging means 7 for judging the coordinates of the signal obtained by amplifying the output signal of the automatic equalizer 3 is further increased. However, the amplitude error of the coordinate judging means 10 which always performs the coordinate judgment of the signal in which the output signal of the automatic equalizer 3 is attenuated is offset by the positive amplitude error of the line and becomes small. 1
2 is switched to the output of the coordinate determination means 10. For this reason, the input signal of the decoder 14 is a signal whose amplitude fluctuation has been corrected by the attenuator 9. Then, when the amplitude fluctuation is corrected by the automatic gain controller 1, the amplitude error of the coordinate judging means 4 becomes the smallest, so that the switch 12 selects the output of the coordinate judging means 4.

In the conventional example shown in FIG. 2, the amplitude fluctuation is corrected by the automatic gain controller 15, but the control speed of the automatic gain controller 15 is set relatively low to prevent the transmission quality from deteriorating. However, even if an amplitude fluctuation occurs to such an extent that a data error occurs, a convergence time of 100T or more of the normal baud rate clock is required and many data errors occur.
However, in the method of the present invention, the switch control means 13 controls the switch 12 by sufficiently recognizing the amplitude fluctuation in about 10T of the baud rate clock. Is small.

[0010]

As described above, according to the present invention, in addition to the ordinary coordinate judging means, the coordinate judgment of the signal obtained by always amplifying and attenuating the output signal of the automatic equalizer in order to cancel the amplitude fluctuation is performed simultaneously. Since the output of the coordinate determination means having a small amplitude error is decoded by comparing the amplitude errors of the respective inputs and outputs,
This has the effect of minimizing the degradation of the quality of the received signal even when a sudden amplitude fluctuation occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Automatic gain controller (AGC) 2 Demodulator 3 Automatic equalizer 4 Coordinate determination means 5 Amplitude error extraction means 6 Amplifier 7 Coordinate determination means 8 Amplitude error extraction means 9 Attenuator 10 Coordinate determination means 11 Amplitude error extraction means 12 Switching Unit 13 switcher control means 14 decoder 15 automatic gain controller 16 demodulator 17 automatic equalizer 18 coordinate determination means 19 decoder

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-372248 (JP, A) JP-A-60-500473 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/38 H04L 27/01

Claims (1)

(57) [Claims] 1. An automatic gain controller for adjusting the level of a received signal, a demodulator for demodulating the received signal whose level has been adjusted by the automatic gain controller, and a telephone line included in the signal demodulated by the demodulator. A quadrature amplitude modulation data receiver comprising: an automatic equalizer for equalizing distortion due to the signal; and a decoder for decoding a signal related to the signal equalized by the automatic equalizer to obtain received data. First coordinate determining means for determining an output signal of the equalizer to a predetermined data coordinate point; first amplitude error extracting means for extracting an amplitude component of an error between an input signal and an output signal of the first coordinate determining means; An amplifier for providing an amplitude gain to an output signal of the automatic equalizer; a second coordinate determination unit for determining an output signal of the amplifier to a predetermined data coordinate point; an input signal and an output signal of the second coordinate determination unit And the amplitude component of the error Output second amplitude error extracting means, an attenuator for attenuating the output signal of the automatic equalizer, and third coordinate determining means for determining the output signal of the attenuator to a predetermined data coordinate point; A third amplitude error extracting means for extracting an amplitude component of an error between an input signal and an output signal of the third coordinate determining means; an output signal of the first coordinate determining means according to a given command; A switch for giving either the output signal of the means or the output signal of the third coordinate determination means to the decoder, an output signal of the first amplitude error extraction means, an output signal of the second amplitude error extraction means, and The absolute value of the output signal of the third amplitude error extracting means is compared, the amplitude error determining means having the smallest error is specified, and the output signal of the coordinate determining means corresponding to the specified amplitude error determining means is determined. Finger to choose A quadrature amplitude modulation data receiver, comprising: switch control means for giving a command to the switch.