JPS6265524A - Ping-pong transmission equipment - Google Patents

Abstract

PURPOSE:To improve the line frequency characteristic in a short time regardless of types of the wire of a transmission line by providing a setting means obtaining a coefficient of an equalizer characteristic to eliminate the distortion at the tail end ridge of a pulse during the reception pause period. CONSTITUTION:A signal inputted from a reception input terminal 1 and amplified by an AGC amplifier 2 is converted into a digital signal by an A/D converter 3 and enters an f<1/2> equalizer circuit 4, which is an m-order digital filter whose characteristic Hz is expressed as Hz=1-az<-m>, and the spread of a reception pulse to an isolated transmission pulse is squeezed within a prescribed time by setting the constant (a) to a proper value. After one burst training data is received till the next burst comes, an operation/control circuit 7 calculates the coefficient (a) and inputs the result of calculation to the f<1/2> equalizing circuit 4 to complete the setting of the circuit 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the improvement of a two-wire digital subscriber line transmission device, a so-called ping-pong transmission device, and in particular, to improvement of line frequency characteristics according to the length of the transmission line. The improvements are related to the F-equalization method.

[Conventional technology]

This type of ping-pong transmission device repeatedly transmits and receives information alternately within a fixed period (usually 2.5 ms). This is done within a burst (called a burst).

Therefore, in the ping pong transmission device, the communication mode and
Training mode is set.

The communication mode is a mode for performing normal communication.

In addition, the training mode is a mode in which isolated pulses are periodically transmitted and received, and the training mode is executed before the communication mode described above, and each device on the transmitting and receiving side is set to the communication mode during the training mode. Preparations are being made to move to

By the way, such a ping-pong transmission device improves line frequency characteristics depending on the length of the transmission line by providing an equalizer.

[Problem that the invention seeks to solve]

However, the conventional ping pong transmission device has the following problems.

That is, in such conventional methods, a specific line type (for example, 0
．． 5wmφ) lines can be almost completely equalized, but lines of different types (for example, 0.4wmφ) can be equalized almost completely.

0.65mmφ, 0. Equalization of the line L+nφ), i.e.
Line frequency characteristics are imperfect. As a result, for example, when an isolated pulse as shown in Figure 4a is transmitted, if the length of the transmission line is long, the pulse width will be greatly expanded on the receiving side, as shown in Figure 4. The problem is that the received waveform interferes with the next isolated pulse in code amount.

Therefore, the present invention has been made in view of the above circumstances, and its object is to provide a ping-pong transmission device that can improve the line frequency characteristics regardless of the line type.

[Means for solving problems]

The present invention uses an equalizer having a characteristic HZ (-1-a z-'') set to remove isolated pulses l received on the receiving side & distortion on the edge side, and and setting means for determining the coefficient a based on the leading portion of the isolated pulse.

Find a coefficient to reduce the distortion.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

In the figure, 1 is a reception input terminal, from which a signal is input. An AGC amplifier 2 is installed after the input terminal 1.
is provided. The AGC amplifier 2 has the input terminal l
The input signal is amplified to an appropriate voltage level. Further, the signal amplified by the AGC amplifier 2 is converted into a digital signal by an A/D converter 3 located after the AGC amplifier 2.

Further, at the subsequent stage of the A/D converter 3, an equalizer 1 is installed.
An equivalent circuit 4 is provided. The W equivalent circuit 4 is an m-order digital filter whose characteristic Hz is expressed by the following formula (1). It functions to reduce the spread of received pulses relative to isolated transmitted pulses within a certain period of time (for example, 8T). (However, T is the reciprocal of the transmission speed, that is, the time width of 1 bit.) Hz = 1-az-" (1) In other words, when an isolated pulse as shown in Figure 2 a is transmitted, if the line length is long, it will not be received. On the other hand, a waveform with a very wide pulse width is received, as shown in Figure 2, for example.
The long trailing portion of the trailing edge of the pulse -λt can be approximately regarded as an exponential function like Ae. Therefore, when the A/D converter 3 applies a signal sampled with a period τ as shown in FIG. 2C to the H equalization circuit 4, the F equalization circuit 4 has a
(2), the output of the E equalizer 4 is the second
- As shown in Figure d, the long trailing portion (the portion approximated by Ae) is eliminated, and the spread of the pulse width is shortened. Here, m is a positive integer that satisfies the relationship mτ<T (3).

However, the optimal value of a is unknown until bf equalization training is completed, so during training, a=o (Hz=
1) The JT equalization circuit 4 outputs the input as is.

, the output of the square equalization circuit 4 is led to a real-time processing circuit 6 and a bridge tap equalization circuit 8. Also, A/D converter 3.
/'r equalization circuit 4. As the operating clock for the real-time processing circuit 6, a clock having a period r (-eg, τ=T/4) is applied from the clock generation circuit 5 to each of the real-time processing circuits 6.

The real-time processing circuit 6 and the arithmetic/control circuit 7 calculate the coefficient a of the F equalization circuit 4 based on the received sampled data input to the real-time processing circuit 6 using the following algorithm, for example. Calculate and set.

In order to make the principle of the present invention easier to understand, the following description will be made using the output waveform of the AGC amplifier 2 before sampling.

The transmission waveform during training is basically an isolated pulse AMI (^
1ternate Mark Inversion).

Therefore, the received waveform of the isolated pulse (AG
C amplifier output waveform) is expressed as 7" iso (t), the received waveform during training is expressed as f tra (t). However, to is the start time of f tra (t).

For −≧−8T, 1'1sot=be−λC141)
(5゜However, assuming b=γiso (8T), to+8nT<t-≦-to+8 (n+1)T, 1' tra (tl = (-1))'iso (t-to-9nT)
-Σ(-1) b8 1 layer heavy 69-) TO D)KuI = (-1>' 7Iso (t-to-8nT)-
(-1) 9 b6-λt☆-ko θ-rkiding) 1- (-
6-")'L 1+eJ2-7 (6) Therefore, (.zuλd) capital < 1
(7) For n, it becomes. That is, if we set 0-≦- for 1≦t8T, then in to+sn'r<t<t0+s (n+1)T, γtra Ltl -(-1)%r7So(t t, 18 n T) (
10), and it can be seen that it is received as the AMI of r iso (t).

Therefore, 1o-≦- is 1≦-t. γave for +8T
(When calculating tl - NO , and aveLt) = γ1so (t - to )
(12). However, N is the minimum value of n that satisfies equation (7). Even if noise is superimposed on the rtra river, the noise power can be reduced by the averaging operation of equation (11).

(S1' iso Lt) is as shown in equation (9),
iso ft) from the waveform at the beginning (0-≦-t<3T) of the exponential relationship <e-)'-"I, and the term that attenuates according to It can be considered as the proximal waveform of the beginning part.

As can be seen from equation (11), the received waveform used for the averaging calculation is the waveform after jtra (t,) +8N,) T), so it is not necessary to find the rising time tρ of the beginning of )'tra (tl so strictly). For example, set an appropriate threshold voltage, detect the leading edge of the pulse, consider that point to be, for example, t.
N, -1) The calculation of Σ in equation (11) may be started after T.

riso (t) is 1. even when t<8T. <1<8
Within the range of T, it can be approximated by the same waveform as in equation (5):
(13). therefore,
When 5T<t<8T, then. Therefore, 5T<t-mr<t<8T (15) holds true. This is equal to the value of the coefficient a of the F equalization circuit 4 shown in equation (2). However, determining the coefficient a by calculating only one point t is easily affected by noise, so it is difficult to determine the coefficient a for multiple t =
It is better to use the value of

As described above, after detecting the rising time (1° + T) of the leading pulse, using equations (11), (13), and (17), 1. However, in this algorithm, from the detection of the rising edge of the first pulse (11
) Σ(-1) in the formula? Lrtra(t + 8 n T
) is executed by the real-time processing circuit 6, and then 1
The division of /(N-N,) and the calculation of equation (17) are performed by the arithmetic/control circuit 7 during the pause period of the reception burst. Note that N-N.

By choosing N and N such that -32(-2), the division of 1/(N-N,') can be simplified.

The real-time processing circuit 6 functions as a waveform calculation means, and the calculation/control circuit 7 functions as a setting means for determining the coefficient a.

As described above, after receiving one burst of training data, by calculating the value of the coefficient a in the arithmetic/control circuit 7 and inputting the calculation result to the J equalization circuit 4 before the arrival of the next burst, After the setting of the F equalization circuit 4 is completed, from the next burst, the signal data fully equalized by the J equalization circuit 4 is supplied to the bridge tap equalization circuit 8, and the bridge tap equalization circuit 8 performs 17 equalization. The remaining code amount interference mainly caused by bridge taps of the line is removed, and the correct received data is reproduced and guided to the output terminal 9. In addition, in the figure, 10 is an output terminal of the reception clock.

As the bridge tap equalization circuit 8, for example, one based on the invention "Bridge tap equalization method for ping-pong transmission device" (Japanese Patent Application No. 133704/1986) previously filed by the present inventor can be used.

In addition, the supply of a clock synchronized with the transmitting side, which is necessary for bridge tap equalization, is provided by the invention previously filed by the present inventor, ``Bit Synchronization System for Ping-Pong Transmission Device'' (June 12, 1985). This can be done by a method (patent application).

The real-time processing circuit 6 and the arithmetic/control circuit 7 are components that are commonly used in these two previously filed inventions.
The extra hardware required for this invention is extremely small, consisting only of the program and data memory in the arithmetic/control circuit 7.

Thus, as described above, in the ping-pong transmission device according to the present invention, the destination of the isolated pulse response periodically received during the reception of one burst of training data is determined, and after the reception of that burst is completed, the next burst l -a is determined. By calculating the coefficient a of z-' and setting the coefficients of the digital filter for JT equalization, p-equivalence can be achieved in a short time by just receiving one burst of training data. It has the advantage that the increase in hardware required for equalization is minimal.

〔Effect of the invention〕

As explained above, the ping-pong transmission device according to the present invention includes an equalizer whose characteristic Hz (=l-az-') is set so as to eliminate distortion on the trailing edge side of the isolated pulse received on the receiving side;
After the reception of the first burst of a plurality of isolated pulses received in one burst in the training mode is completed, during the reception pause period until reception of the next burst begins, the above waveform)'is.

Since the above coefficients are determined in such a way as to reduce the above distortion having the shape of
Line frequency characteristics can be improved in a short time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a pulse waveform diagram, FIG. 3 is a waveform diagram showing a transmission waveform in training mode, and FIG. 4 is a waveform diagram showing problems in the prior art. 4...Equivalent circuit (equalizer), 6...Real-time processing circuit (waveform calculation means), 7...Calculation
Control circuit (setting means). Procedural amendment (Jijo, June 9, 1988, 1, Indication of the case, Patent Application No. 1983-205072, 2,
Name of the invention: Ping-pong transmission device 3, relationship with the case of the person making the amendment Patent applicant address: 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, Agent Address: 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo
, the scope of the claims to be amended, the detailed description of the invention, and the drawings section. 6. Contents of amendment + l) The scope of claims is amended as shown in the attached sheet. (2) Page 4, line 6 of the specification, page 5, line 12. Line 19, page 6, line 17, page 14, line 9, line 19 rH2J is corrected to r H (ZI J. (3) Same book, page 3, line 4 , page 4, line 7, page 5, line 10, page 14, line 13, line 20, page 15, line 18, "equivalent" was corrected to "equalization" (4) In the same book, page 5, line 11, "/r equivalent circuit 4 is provided. The r equivalent" is replaced with "J equalizer circuit 4 is provided. The gong equalization." (5) In the same book, page 3, line 5, the phrase "by providing" is corrected to "by providing and changing the frequency characteristics of the equalizer in conjunction with the gain of the AGC amplifier." (6) In the same book, page 3, line 6, “Improved.” is corrected to “compensated.” (7) In the same book, page 3, line 14, “The frequency characteristics are not affected.” (8) On page 3, line 16 of the same book, the phrase ``On the receiving side, as an example'' was replaced with ``Compensation of frequency characteristics is incomplete.'' On the side, even after passing through an equalizer, it is corrected as "an example". Question 01, same book, page 9, line 3, "e''"" + 9) J is corrected as "e-人7 (9)" . tIIl Ibid., page 10, line 7, ``exponential relationship'' is corrected to ``exponential function.'' . In the first line of the same book, page 1121, the phrase ``a plurality of'' is amended to ``a plurality of such as, satisfying the expression.'' 1131 Ibid., page 15, line 5, ``The above waveform ♀1sol'' is corrected to ``the above waveform 7 products''. Endosho, page 9, line 3 r7iso t-Yiso t
-J is r(iso(t)=riso(t)-J
and correct it. 0!1 Drawing and Figure 1 will be corrected as shown in the attached sheet. Above 2, Claims The transmitting side and the receiving side are connected via a transmission line, and the system transitions to a normal communication mode through a training mode consisting of one or more bursts in which isolated pulses are periodically transmitted and received. In the transmission device, there is provided an isolator having a characteristic Hfzl (-1-a z-') set to eliminate distortion on the trailing edge side of the isolated pulse received at the receiving side, and an isolator at the first burst in the training mode. a waveform calculating means for obtaining a near wave (it7 ft) of the leading portions of the plurality of isolated pulses by arithmetic averaging the reply waveforms of the leading portions of the plurality of isolated pulses received; and a setting means for calculating the coefficient a of the characteristic H (Zl) based on the waveform ♀1R (11), and the setting means is configured to set the waveform 'ffi milk ft) and a predetermined value. A ping-pong transmission device characterized in that the coefficient a is determined so as to reduce the distortion having a relational shape.

Claims (1)

[Claims] Ping-pong transmission in which a transmitting side and a receiving side are connected via a transmission line, and a transition is made to a normal communication mode through a training mode consisting of one or more bursts in which isolated pulses are periodically transmitted and received. The device includes an equalizer whose characteristic Hz (=1-az^-^m) is set to eliminate distortion on the trailing edge side of the isolated pulse received on the receiving side, and By arithmetic averaging the approximate waveforms of the leading parts of the plural isolated pulses, the approximate waveform of these leading parts ■iso(t)^
(^1^) and during the reception suspension period from the end of reception of the first burst to the start of reception of the next burst, the waveform ■iso(t)^(^1^) is calculated. a setting means for determining a coefficient a of the characteristic Hz based on the above-mentioned waveform ■iso(t)^(^1^); A ping-pong transmission device characterized by the following features.