JPH0795761B2 - Modulator / demodulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention is a modulator / demodulator that transmits / receives amplitude / phase modulated digital information. In order to improve the S / N characteristics, the complex number coordinate determination surface of the value of the output signal of the equalizer is used. According to the position, the quantizing judging means and the minimum distance judging means are switched by the selecting means to judge the value of the output signal of the equalizer.

[Industrial application field]

The present invention relates to a modulation / demodulation device that transmits / receives amplitude / phase modulated digital information and determines an output signal of an equalizer on a complex number coordinate determination surface. This device is suitable for high-speed, multi-level signal modulation / demodulation devices such as V29, V33, and 19.2 Kbps of CCITT recommendation, which require good S / N characteristics.

[Conventional technology]

As a conventional hard-decision method of modulation / demodulation for transmitting / receiving amplitude-phase-modulated digital information, there is, for example, a technique implemented in a modulation / demodulation apparatus shown in the block diagram of FIG.

Reference numeral 10 is an A / D converter for A / D converting the amplitude / phase modulation signal received from the modulation / demodulation device on the transmission side via the communication line 9, and 11 is
An automatic gain control circuit (hereinafter referred to as "AGC") that amplifies the output signal of the A / D converter 10 to a signal of a constant level, 12
Is a demodulator, which demodulates the frequency-phase modulated carrier wave and outputs the data signal. 13 is a carrier generation circuit that oscillates at the same frequency as the carrier wave (hereinafter, "CR
R ”. ), And the output signal is output to the demodulator 12. Reference numeral 14 is a roll-off filter (hereinafter referred to as "ROF"), and 15 is an automatic equalizer for compensating the waveform distortion that the received signal has received due to the characteristics of the communication line. Reference numeral 16 is a phase jitter removal circuit (hereinafter referred to as "CAPC") that removes phase jitter generated due to a decrease in frequency. Reference numeral 17 is a hard decision circuit. The hard decision circuit 17 adopts a quantization decision method, the details of which will be described with reference to FIG.

As shown in FIG. 4, the horizontal axis is a real number, and the vertical axis is an imaginary number complex number coordinate plane, which is divided into grid-like sections containing one piece of determination data. Then, the partition data is stored in the ROM in advance, and when the digital information is received from the modulator / demodulator on the transmission side via the communication line, the partition that includes the value of the output signal of the automatic equalizer 15 of the modulator / demodulator. Is output as the determination result.

[Problems to be solved by the invention]

However, in such a conventional modulator / demodulator, a method of preliminarily storing the division information of the complex number coordinate determination surface divided into a lattice shape and searching for the division including the value of the output signal of the equalizer Therefore, if, for example, Gaussian noise is introduced into the communication line between modulators and demodulators, the S / N characteristics will deteriorate in the hard decision, and the transmission speed will increase and the decision plane information will be stored. RO to keep
There was a problem that the capacity of M increased.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a modulator / demodulator capable of improving the S / N characteristics in hard decision and saving the ROM capacity. .

[Means for solving problems]

Then, in order to achieve this object, in the present invention, in the modulation and demodulation device for transmitting and receiving amplitude-phase modulated digital information, the complex coordinate judgment surface is divided into a grid-like section containing one judgment data. Quantization determining means 2 that outputs the determination data of the partition including the value of the output signal of the equalizer as a determination result, and one area set to be equidistant from the center of the complex coordinate determination surface. A minimum distance determining unit 3 that stores one or a plurality of determination data in the vicinity, obtains the determination data that minimizes the distance from the equalizer output, and outputs the determination data as a determination result, and the complex number coordinate determination. When the value of the output signal of the equalizer is located within the area that is equidistant from the center of the surface, the quantizing determination means 2 is selected and outside the area that is equidistant from the center of the complex coordinate determination surface. To When the value of the equalizer output signal is located was comprise a selection means 1 for selecting the minimum distance determining means 3.

[Action]

Next, the operation of the present invention will be described based on the principle diagram of the present invention shown in FIG.

The selecting means 1 selects the quantizing determining means 2 when the value of the output signal of the equalizer is located in the area equidistant from the center of the complex number coordinate determination surface, while selecting the quantizing determination means 2 from the center of the complex number coordinate determination surface. When the value of the output signal of the equalizer is located outside the range of distance, the minimum distance determination means 3 is selected.

When the quantizing judging means 2 is selected, the quantizing judging means 2 divides the complex number coordinate judging surface into a grid-like section containing one judging data and the value of the output signal of the equalizer is included. The judgment data of the section is output as the judgment result.

When the minimum distance determination means 3 is selected, the minimum distance determination means 3 stores one or a plurality of determination data in the vicinity of one area set to be equidistant from the center of the complex coordinate determination surface, The determination data that minimizes the distance from the output of the equalizer is obtained, and the determination data is output as the determination result.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of the hard decision circuit 27 of the modulation / demodulation device having a transmission rate of 19.2 Kbps. This is obtained by replacing the hard decision circuit 17 of FIG. 4 with the hard decision circuit 27 of the present invention, and other circuits are basically the same as the conventional ones. Then, FIG. 3 (A) shows the first quadrant of the complex number coordinate judging surface used by the hard judging circuit 27. The complex number coordinate determination planes in the second to fourth quadrants are the same as these and are not shown. Incidentally, FIG. 3 (B) to (F)
Have transmission speeds of 16.8Kbps, 14.4Kbps and 12.0KbpsKbp, respectively.
s, 9.6 Kbps, 4.8 Kbps is a complex number coordinate determination surface when transmitting.

The structure and operation of the hard decision circuit 27 will be described with reference to FIG.

Reference numeral 18 is a selector, and 19 is a switch which is switch-controlled by the selector 18 in two directions, and these realize the selecting means 1 in the claims. That is, the selector 18 stores in advance, in the internal ROM, boundary line data of a circular area having a radius r from the center 0 of the complex number coordinate determination surface of FIG. 3 (A), and is stored in the boundary line via the CAPC 16. Input automatic equalizer 16
When it is determined that the value of the output signal is present, the output of the switching signal S is stopped and the switch 19 is held in the direction shown by the solid line to automatically input the signal to the quantization determination circuit 20 to be described later via the CAPC 16. The output signal of the equalizer 16 is input. Also, when the selector 18 determines that the value of the output signal of the equalizer 16 exists outside the circular region having the radius r from the center 0 of the complex number coordinate determination surface, it outputs the switching signal S to the switch 19. As a result, the switch 19 is switched to the direction shown by the dotted line and the CAPC 16
The output signal of the automatic equalizer 16 input via is input.

When the switch 19 is held in the direction shown by the solid line, the quantization decision circuit 20 inputs the value of the output signal of the automatic equalizer 15 via the CAPC 16, and the complex number coordinate decision plane contains one decision data. As described above, the determination data of the section in which the value of the output signal of the automatic equalizer 15 via the CAPC 16 is included is output as the determination result. Thus, the quantization determination circuit 20 realizes the quantization determination means 2 in the claims.

Next, the minimum distance determination circuit unit 26 which realizes the minimum distance determination means 3 in the claims will be described.

Reference numeral 24 is a ROM, which has a radius r from the center 0 of the complex number coordinate determination surface.
A plurality of determination data existing in the vicinity of the circular area is stored in advance. Reference numeral 21 denotes a subtraction circuit, which stores the values in the real number axis coordinates and the imaginary number axis coordinates of the output signal value of the automatic equalizer 15 input via the CAPC 16 and the ROM 24 when the switch 19 is switched in the direction shown by the dotted line. The difference between the real-axis coordinate and the imaginary-axis coordinate of the determination data in the vicinity of the circle area is calculated. twenty two
Is a multiplication circuit, and calculates the square product of the difference obtained by the subtraction circuit 21. This is because when Gaussian noise shifts the received signal in the vicinity of the circle area with radius r from the center 0 of the complex coordinate judgment surface to the outer side from the original position, it is automatically input through CAPC16. This means that the distance between the coordinate of the value of the output signal of the rectifier 15 and the coordinate of the determination data in the vicinity of the circular area is obtained. Reference numeral 23 is a comparison circuit which obtains a value having the smallest distance by mutually comparing the respective squared products obtained by the multiplication circuit 22, that is, the respective distances between the coordinates. Reference numeral 25 is a selection circuit, which obtains determination data when the value obtained by the comparison circuit 23 is the smallest value and outputs the determination data as a determination result.

Even if the received signal in the vicinity of the circular region with radius r from the center 0 of the complex number judgment surface due to Gaussian noise does not exist at the original position, it should be correctly positioned on the ideal position on the complex number judgment surface. I tried to correct it.

〔The invention's effect〕

As described above, according to the modem device of the present invention,
Since the quantizing judgment means and the minimum distance judgment means are switched by the selection means depending on the position of the output signal value of the equalizer on the complex coordinate judgment surface, the value of the output signal of the equalizer is judged. In the vicinity of the area equidistant from the center of the surface, even when the received signal is shifted from the original position due to Gaussian noise, it can be correctly corrected to the ideal position that should originally exist on the complex number judgment surface. It is possible to improve the S / N characteristic in hard decision. Also, since the quantization determination means by program processing is used,
It is possible to significantly reduce the ROM capacity than before.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram of a hard decision circuit in an embodiment of the present invention, FIG. 3 is a complex number coordinate decision plane in the hard decision circuit shown in FIG. 2, and FIG. FIG. 5 is a block diagram of a conventional modulator / demodulator, and FIG. 5 is a complex coordinate decision plane in the hard decision circuit shown in FIG. 1 ... Selecting means 2 ... Quantization determining means 3 ... Minimum distance determining means

Claims (1)

[Claims] 1. A modulation / demodulation device for transmitting / receiving amplitude-phase modulated digital information, wherein a complex number coordinate judgment plane is divided into a grid-like section containing one judgment data, and the output signal value of the equalizer is included. Quantization determination means for outputting the determination data of the partition as a determination result, and stores one or a plurality of determination data in the vicinity of one region set to be equidistant from the center of the complex coordinate determination surface,
Minimum distance determining means for determining the determination data that minimizes the distance from the equalizer output, and outputting the determination data as a determination result, and equalization within a region that is equidistant from the center of the complex number coordinate determination surface. When the value of the output signal of the equalizer is located, the quantization determination means is selected, and when the value of the output signal of the equalizer is located outside the area equidistant from the center of the complex number coordinate determination surface, the quantization determination means is selected. A modulation / demodulation apparatus comprising: a selection unit that selects a minimum distance determination unit.