JPS6145415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic equalizer that automatically equalizes waveform distortion in a transmission line, and more specifically, the present invention relates to an automatic equalizer that automatically equalizes waveform distortion in a transmission line. The present invention relates to an automatic equalizer that automatically removes waveform distortion when simultaneously transmitting data using a transmission line that experiences waveform distortion.

The modulation method to which this invention is applied is a modification of the orthogonal amplitude modulation method currently employed in many high-speed data transmissions. First, the above-mentioned quadrature amplitude modulation method will be explained, and secondly, the modulation method to which the automatic equalizer of the present invention is applied will be explained,
Third, the principle of the automatic equalizer of this invention will be explained.

Orthogonal amplitude modulation, which is used in high-speed data transmission, is a method in which two mutually orthogonal carrier waves, ie, a sine wave and a cosine wave, are amplitude-modulated and transmitted using two independent information sequences. For example, a signal that modulates a sine wave The signal that modulates the cosine wave Then, the modulated transmission signal S(t) is expressed as S(t)=p(t)Sin2π _c t +q(t)cos2π _c t . Here, T is the two data series a
_k and b _k are the time intervals at which they are sent, and _c is the frequency of the carrier wave, which is usually selected to be 1700 Hz or 1800 Hz for high-speed data transmission targeting the voice band.
In transmission at 9600 bits/second, T = 1/2400, so a _k and b _k must each have 2 bits of information, and the possible values of the coordinates (a _k , b _k ) are 16 ways are required. Figure 1 shows the data point arrangement (a _k , b
_k ) is an example. If the transmitted signal S(t) is received without any distortion and the pulse waveform m(t)
satisfies the Nyquist condition m(o)=1, m(kT)=0 (k≠0), p(t) and q are separated by two-axis synchronous detection of the received S(t). (t) to T
The set of values obtained by sampling every second at time t=iT is (a _i , b _i ), which corresponds to one of the data points in FIG.

The modulation method targeted in this invention is one that simultaneously transmits digital information and analog value information, and is an extension of the above-mentioned quadrature amplitude modulation as described below.

The above method of expansion involves expressing the coordinates (a _k , b _k ) as polar coordinates (ρ _k , θ _k ), using the mapping shown in Figure 2, where the amplitude coordinate ρ _k is an analog value and the angular coordinate θ _k is a digital value. It's a method. Hereinafter, the above mapping method will be referred to as radial mapping. Using this radial map, θ _k
A data transmission rate of 4800 bits/second is possible with .rho.k, and at the same time 2400 analog values per second can be transmitted with _.rho.k .

In reality, the transmitted signal S(t) undergoes large waveform distortion while being transmitted over the telephone line. Therefore, in the above-mentioned transmission system, as in the case of high-speed data transmission, it is necessary to remove waveform distortion using an automatic equalizer and accurately detect the coordinates (ρ _k , θ _k ).

An object of the present invention is to provide an automatic equalizer for accurately separating and detecting digital information and analog value information by automatically removing waveform distortion in a transmission path.

Next, this invention will be explained in detail using the drawings.

First, the principle of the automatic equalizer of the present invention applied to a transmission system using a radial mapping method will be explained.

The automatic equalization problem of quadrature amplitude modulation can be systematically and concisely explained by expressing all signals as complex numbers. If the impulse response of the equivalent baseband system of the telephone line is H(t), the complex representation R(t) of the two signals (in-phase component and quadrature component) obtained by two-axis synchronous detection of the received signal is as follows. Become.

However, D _k = ρ _k e ^j 〓k X(t)=∫ ^∞ _−∞ m(t-τ)H(τ)dτ
Variable complex value tap gain C ₁ with (t) as input
... It is composed of a two-dimensional variable transversal filter having C _N. In FIG. 3, R(t) is input to a delay line, and a plurality of signals having different delays applied to R(t) are extracted through signal lead lines drawn from the delay line at equal intervals.
Each of these signals is multiplied by the corresponding complex tap gain C ₁ , C ₂ , C ₃ ,... _C The output is Assuming that the output signal of this automatic equalizer is Y(t), each tap gain is automatically adjusted so that the value sampled from Y(t) every T seconds becomes exactly ρ _k e ^j 〓k. The main point of this invention is to provide a circuit that automatically adjusts each tap gain.

Tap gain adjustment in the case of radial mapping is performed every T seconds according to the following equation.

C _o ^k+1 = C ^k _o −αe ^−j 〓k (Y((k−L)T)−e ^j 〓k−L (n=1, 2,...N, 1LN) Here, θ _k is the time It is the estimated value of digital information at t=kT, and in the case of Fig. 3, it is π/4 or 3π/
4 or 5π/4 or 7π/4. The tap gain obtained by repeating the successive adjustment according to the above equation realizes Y(kT)=ρ _k e ^j 〓k.

The feature of this tap gain adjustment method is that the gain fluctuation of the analog value information series ρ _k converges to the desired solution without being affected by temporal correlation, and it can be applied to analog value information transmission in a wider range of fields. .

Embodiments of the present invention will be described below with reference to FIGS. 4, 5, and 6.

In FIG. 4, two baseband signals obtained by two-axis synchronous detection are input from terminals 1 and 2. A delay line in which delay elements 3 and 4 are connected in series is connected to terminal 1, and a delay line in which delay elements 5 and 6 are connected in series is connected to terminal 2. Two pairs of signal lead lines 7 and 8, 9 and 10 are connected from the connection lines connecting each delay element.
11 and 12 are drawn out, and two-dimensional bridge type variable attenuators 13, 14, and 15 shown in FIG. 6 are connected to the three pairs of lead lines. The above two-dimensional bridge type variable attenuator has a complex signal X+jY and a complex tap gain c _i +jd _i
This is a circuit that performs complex multiplication of , and the multiplication result (Xc _i −
The real and imaginary parts of Yd _i )+j(Xd _i +Yc _i ) are taken out as the outputs of the two adders shown in FIG. 6, respectively. Each two-dimensional bridge type variable attenuator outputs two signals, and the adder 16 outputs lines 17, 18 and 1.
The sum of the output signals of one of the two-dimensional bridge type variable attenuators flowing through the line 9 is outputted to the line 20 where the sum is determined. Similarly, adder 21 calculates the sum of the other output signals of the two-dimensional bridge type variable attenuators flowing through lines 22, 23 and 24, and outputs an equalized signal to line 25. 27 is an estimator that estimates digital data from the signals output to lines 20 and 25, and outputs digital estimated data to line 38. If the signals output to the line 20 and the line 25 are P and Q, this estimator 27 first calculates P
This circuit determines the polarity of Q and Q, and outputs an estimated data D to the line 38 according to the following regulations in accordance with the determination result, and can be constructed from a polarity determiner and a simple logic circuit.

When P0 and Q>0 D=00 When P<0 and Q0 D=01 When P0 and Q<0 D=10 When P>0 and Q0 D=11 Note that D=00 means that the angular coordinate θ _k is It is π/4. D
=01 means 3π/4, D=10 means 5π/4, and D=11 means 7π/4. The equalized signals output to the lines 20 and 25 and the estimated digital data output to the line 38 are input to the tap gain correction circuit 23, and in the tap gain correction circuit 23, the two-dimensional bridge type variable attenuators 13, 14 and The acting variable gain is output on lines 29, 30, 31, 32, 33 and 34.

FIG. 5 shows an embodiment of the tap gain correction circuit 23. Since the estimated digital data coming from the track 38 is angle information, it is converted to the conversion circuit 72.
is converted into cosine and sine components. The cosine and sine components transformed by circuit 72 are input to subtracters 70 and 71, respectively, where they are subtracted with the corresponding equalized signals, ie, the signals input from lines 20 and 25. subtractor 70
The outputs of 71 and 71 are the delay element arrays 3 and 4.
and are connected to delay element arrays 73, 74 and 75, 76 having the same delay time and number as 5, 6.
On the other hand, only one of the output signals of the circuit 72 is sign-inverted by a sign-inverting circuit 79, and is input to delay elements 77 and 78 having a delay equal to the delay to the center tap position in this automatic equalizer. . The output signals of the delay elements 77 and 78 are complex multiplied by the signals from the connection lines connected to the delay elements 73, 74, 75, 76, etc. in two-dimensional bridge type variable attenuation circuits 80, 81, and 82. It can be done. two-dimensional bridge type variable attenuation circuit 80,
81 and 82 are realized by the configuration shown in FIG. two-dimensional bridge type variable attenuation circuit 80,
The two outputs 81 and 82 are sent to the amplifier 8.
3, 84, 85, 86, 87 and 88 to update the contents of integrators 89, 90, 91, 92, 93 and 94, lines 29, 30, 31,
Derive new tap gains at 32, 33 and 34. All the tap gain correction circuits shown in FIG. 5 are successively corrected and automatically equalized once each time one sample value is obtained.

According to this invention, it is believed that a modulation/demodulation device that simultaneously transmits digital information and analog value information as data transmission will create various new applications, but it is particularly applicable to data and voice as an application field using existing telephone lines. This enables many applications such as simultaneous transmission of data and biomedical information (electrocardiogram, electroencephalogram, etc.), photographic transmission, etc.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams for explaining the principle of this invention. Figure 1 is a diagram showing an example of data point arrangement, Figure 2 is a diagram explaining a radial mapping method, and Figure 3 is a diagram for explaining the radial mapping method. A block diagram showing a two-dimensional transversal filter, FIG. 4 a block diagram showing an embodiment of the automatic equalizer of the present invention, FIG. 5 a block diagram showing an embodiment of the tap gain correction circuit 23, and FIG. is a block diagram of a two-dimensional bridge type variable attenuator. In the figure, 3, 4, 5, 6 are delay elements, 1
3, 14, and 15 are two-dimensional bridge type variable attenuators;
16 and 21 are adders, 27 is an estimator, 23 is a tap gain correction circuit, 70 and 71 are subtracters, 72 is a conversion circuit, 73, 74, 75, and 76 are delay element arrays, 77 and 78 are delay elements, 79 80, 81, 82 are two-dimensional bridge type variable attenuators, 83, 84, 85, 86, 87, 88 are amplifiers, and 89, 90, 91, 92, 93, 94 are integrators, respectively. .

Claims (1)

[Claims] 1. Two-axis synchronous detection in a method that simultaneously transmits digital information and analog value information using a radial mapping method that is an extension of orthogonal amplitude modulation that simultaneously amplitude modulates two carrier waves, a sine wave and a cosine wave.
a two-dimensional variable transversal filter into which two baseband signals are input; means for obtaining an estimated value of transmitted digital information from angular coordinates in a polar marker representation of two output signals of the two-dimensional variable transversal filter; By providing means for determining the error with the output signal of the two-dimensional variable transversal filter, and means for adjusting the variable complex value tap gain in the two-dimensional variable transversal filter using the estimated value and the error, the analog value An automatic equalizer characterized by performing equalization without depending on gain fluctuations and temporal correlation of information.