JPH05244037A - Signal transmitter/receiver and transmitting and receiving equalizing circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for manual operation for transmission and reception corrections corresponding to the cable loss of a line by deciding the signal attenuation quantity of the line from a received signal and automatically correcting a transmitted signal without any external control. CONSTITUTION:A receiving transformer 10 receives the transmitted signal from an opposite transmitter/receiver through the line 20 and inputs it to an attenuation quantity decision part 12. The decision part 12 decides the signal attenuation quantity of the line 20 on the reception side and sends decided quantity information 17 to a reception equalizing amplification part 13 and a transmission equalizing amplification part 15. The amplifier part 13 corrects the received signal from the transformer 10 according to the information 17 and outputs the reception equalized output signal to a receiver main body through a discrimination part 14. The transmitted signal 19, on the other hand, is inputted to the amplifier part 15, which corrects the signal attenuation quantity of the line 21 on the transmission side and sends out the equalized transmitted signal to the reception side of the opposite transmitter receiver through the line 21. Consequently, the signal corrections corresponding to the cable loss are automatically made to eliminate the need for manual operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal transmitter / receiver for transmitting information, and more particularly to a transmission signal transmitter / receiver characterized by a control system of a transmission signal correction function for transmission correction of signal attenuation of a transmission medium, and The present invention relates to a transmission / reception equalization circuit for a PCM signal transmitted through a 4-wire metallic cable, and more particularly to an equalization circuit for equalizing transmission / reception waveforms on only one side of the cable.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 13, a transmission signal transmitter / receiver of this type has a transmission equalizer / amplifier 6 for correcting the attenuation characteristics of a cable 2 (hereinafter referred to as a line) facing each other.
The reference numerals 1A and 61B represent correction amount information according to a previously known line length, or correction amount information input from a result of observing a transmission waveform at a certain point on the line, which is external to the transmission signal transceivers 60A and 60B. Was more controlled. Also,
The conventional waveform equalization circuit has been installed on either the reception side or the transmission side of the opposing transmission / reception circuit. When installed on the transmitting side, the frequency characteristics of the cable loss that affects the signal waveform at the opposite receiving circuit are almost unknown, so the construction staff and maintenance personnel estimate the cable loss and manually The transmission equalization circuit was set by operation. In addition, the cable is installed at both ends of the cable regardless of whether it is installed on the transmitting side or the receiving side.

[0003]

In this conventional transmission signal transmitter / receiver, in addition to the problem that the line length must be known in advance, the correction amount information must be re-input every time the line length is changed. There was a problem.
Further, in the other conventional technique, the point that a signal waveform can be observed in the middle of a line, for example, the problem that a terminal board must be provided, and that the correction amount information is slightly monitored while observing the signal waveform on the line each time the line length is changed There was a problem that it had to be changed for each setting.

Further, the conventional transmission equalization circuit has a drawback that it requires manual operation.

Further, when one of the transmitting and receiving circuits is installed in a station facility or the like and a general user cannot touch it, and the other transmitting and receiving circuit is in the user's hand, the user is required to further extend the transmission distance. Sometimes there was a problem that the user alone could not do anything.

[0006]

SUMMARY OF THE INVENTION The present invention is a transmission signal transmitter / receiver for transmitting / receiving information between a plurality of points via a transmission medium having an attenuation characteristic with respect to the transmission signal amplitude. A configuration comprising: an attenuation amount determination means for estimating an attenuation amount of the transmission medium from a received signal; and a transmission signal correction means for multiplying an original signal waveform by an inverse characteristic of the attenuation characteristic of the transmission medium based on the attenuation amount. I am trying.

According to a second aspect of the present invention, in a waveform equalization circuit connected to each of a transmission line and a reception line of a four-wire communication line, a first bandpass filter through which a signal band component of a reception signal passes is provided. , The gain frequency characteristic including the first band-pass filter is simulated to the loss frequency characteristic of the line with less loss due to the increase of the control signal level, and then passes through the first pseudo line and the first amplifier in order. Then, the transmission signal is sequentially transmitted to the attenuator, the second bandpass filter having the same configuration as the first bandpass filter, the second pseudo line having the same configuration as the first pseudo line, and the second amplifier. The configuration is such that the low-pass filter is charged when the peak of the output of the first amplifier exceeds a fixed threshold value, and a peak detection circuit that prevents discharge of the low-pass filter when the peak of the first amplifier output does not exceed the fixed threshold is provided. It is configured to apply a force as the control signal of the first and second pseudo line.

[0008]

The present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram of a 4-wire digital transmission signal transmitter / receiver according to an embodiment of the present invention. A receiving transformer 10 that receives a transmission signal of an opposing transceiver through a pair of pair lines 20, and a line 20 on the receiving side from the output signal thereof.
Of the signal attenuation amount, the reception equalization amplification unit 13 that corrects the reception signal from the reception transformer 10 based on the determination amount information 17, and the reception equalized output signal. The discriminator 14 for retiming and identifying and outputting the reception logic signal 18, and the transmission logic signal 19 for the determination amount information 1
7, a transmission equalization amplification unit 15 that corrects the signal attenuation amount of the other pair line 21 on the transmission side, and a transmission transformer that transmits the transmission signal to the reception side of the transceiver that opposes the transmission signal through the line 21. It is composed of 11.

FIG. 2 is a connection diagram showing an example of use of the digital transmission signal transmitter / receiver of FIG. 1, and the digital transmission signal transmitter / receiver 1 of FIG. 1 having a function of correcting the attenuation amount of the transmission signal,
A conventional digital transmission signal transmitter / receiver 3 that does not have a function of correcting the attenuation amount of the transmission / reception signal is transmitted / received 1
They are connected by a cable 2 including a pair of transmission lines. As will be described later, by only providing the digital transmission signal transmitter / receiver of the present invention on one side, the signal attenuation characteristic is automatically corrected on the transmission line, and accurate transmission over a long distance can be performed.

Prior to explaining the operation of FIG.
The pattern of signal attenuation of a signal passing through a line connecting two transceivers will be described. FIG. 3 is a typical example showing the relationship between the signal frequency of the paired lines and the signal attenuation amount per unit line length, and it is known that most lines have the characteristics of almost the same tendency. It can be seen from FIG. 3 that the higher the signal frequency is, the larger the signal attenuation amount is, and that the signal is attenuated even at the low frequency.

Now, the transmission logic signal 19 shown in FIG.
As shown in (a), it is assumed that the values are 1, _0, 1, ... And the cycle T (transmission signal center frequency f ₀ = 1 / 2T) is 5 μ.
s, assuming that the transmission signal amplitude is 100% rectangular wave of 1v, f
_{Since 0} = 100 kHz and higher frequency components are also included little by little, if the transmission equalization amplification unit 15 in Fig. 1 transmits a rectangular wave as shown in Fig. 4 (a). Then, at the receiving end that opposes, a signal having a very small amplitude distorted as shown in FIG. 3A due to the signal attenuation characteristic of the line 21 as described in FIG. 3 (0.5 mmφ in the example of FIG. 3).
If it is a pair of wires, it will be attenuated by about 9 dB per 1 km of line length) and cannot be received accurately. Here, if the transmission equalization amplification unit 15 knows the signal attenuation amount of the line 21 in advance, as shown in FIG. 4B, the transmission equalization amplification unit 15 is not a 1v rectangular wave but f ₀ Transmission signal waveform that is a voltage amplified by the amount of attenuation (corrected to about 3v assuming that the line length is 1km in the example of Fig. 4 (b)) and that further amplified the high frequency component (this is generally called high-frequency emphasis) , The signal at the receiving end that opposes even if it is attenuated by the line 21 can be identified sufficiently accurately.

The estimation of this signal attenuation amount utilizes that the line 21 is accommodated in the same cable as the line 20,
The determination amount information 17 of the attenuation amount determination unit 12 in FIG. 1 can be used. By detecting the peak amplitude voltage of the received signal, the attenuation amount determination unit 12 can almost determine that it is the signal attenuation amount at f _0. Therefore, the ratio of the amplitude voltage 1v transmitted by the opposite side to the received peak voltage can be calculated. By outputting as the determination amount information 17, the transmission equalization amplification unit 15
From the characteristics of FIG. 3, it can be seen how much a rectangular wave should be corrected to generate a waveform.

Next, an example of the configuration of the transmission equalization amplification unit 15 will be described with reference to the functional block diagram of FIG. 5, and an AND gate 44 that takes an AND condition between the 4-bit decision amount information 17 and the transmission logic signal 19. , The lower 4 bits of the initial load data are fixed to "0", and the upper 4 bits of the initial load data are connected to the output of the AND gate 44 to send each transmission logic signal (each transmission cycle, that is, in FIG. 4). (In the example, every 5 μs)
A ROM address generation unit 40 configured by a counter 43 that is set with data by an initial value load signal and counts up with a 16-times speed clock having a cycle of 1/16 of the transmission cycle, and 8-bit transmission using the output as an address Waveform R of 256 words x 8 bits containing data for equalization
It is composed of an OM 41 and a D / A converter 42 for converting its 8-bit output with an analog transmission waveform.

The operation of the transmission equalization amplification section will be briefly described. The transmission equalization amplification section operates at a 16 × speed clock as shown in FIG.
The transmission signal of the transmission equalization amplification unit in (b) is divided into 16 within the period T, and the transmission amplitude at each point is converted into 8-bit data, and the output information contained in the 16 words of the waveform ROM 41 is read. By generating 16 continuous waveform ROM addresses, it is possible to output a transmission waveform with the transmission logic signal “1” and according to the determination information amount 17 from the waveform ROM 41 through the D / A converter 42.

Next, an embodiment of the transmission / reception equalization circuit of the present invention will be described. FIG. 6 is a block diagram of a transmission / reception equalization circuit according to an embodiment of the present invention. A reception signal input from a reception line (not shown) via the reception input terminals RI1 and RI2 is balanced-unbalanced converted by the reception transformer T1 and then input to the filter FIL1. The filter FIL1 is a BPF (band pass filter) for removing high frequency noise and crosstalk. The output of this filter is input to the automatic pseudo line ALBO1. The attenuation amount of this circuit and the zero-point frequency are interlocked with each other, and they change depending on the control signal. As the cable loss increases, they both move in the lower direction.

Since the output of the automatic pseudo line ALBO1 is minute, the voltage is amplified by the amplifier AMP1 and the reception output terminal RO
1, output from RO2. This output signal is input to the receiver body (not shown). The output of the amplifier AMP1 is simultaneously input to the peak detection circuit PDET, and the fixed threshold value and the peak value are compared. Only when the peak value exceeds the fixed threshold value, a signal having a constant level is passed through the low pass filter L.
Input to PF.

The filter LPF extracts the DC component from the input signal and holds it, and holds the two automatic pseudo lines ALBO1 and ALBO.
Commonly supplied to BO2. The received signal has a waveform free from intersymbol interference by emphasizing the high frequency component lost by passing through the automatic pseudo line controlled in this way.

On the other hand, the transmission signal is input to the attenuator ATT, attenuated by a certain amount, and then the band pass filter FI.
Input to L2. The attenuator ATT is the transmission input terminal T
It is used because the output signal level of the transmitter (not shown) connected to I1 and TI2 is generally too high above the dynamic range of the automatic pseudo-line ALBO2.

The two filters FIL1 and FIL2 have the same circuit, and the two automatic pseudo lines ALBO1 and ABO
LBO2 has the same circuit. The amplifier AMP2 on the transmission side amplifies the high-frequency-enhanced transmission signal, and transmits the transmission signal from the transmission output terminals TO1 and TO2 to the transmission line (not shown) via the transmission transformer T2 for unbalance-balance conversion. To do.

Next, FIG. 7 shows a block diagram of the entire system including the opposite transmission / reception circuit and the cable. Opposite transmitter TRS
AMI code (Alternate of PCM signal transmitted from 0
MarkInversion) transmits the reception line LINE1 and
Is input to the receiving circuit (REQL) shown in FIG. Similarly, on the transmission side, the AMI code output from the transmitter TRS1 is transmitted and equalized by the transmission circuit (TEQL) shown in FIG.
2 is transmitted to the opposite receiver REC0.
The transmission line and the reception line here are names based on the transmission / reception equalization circuit of the present invention.

The principle of waveform equalization will be described with reference to FIG. X of the Fourier transform of the transmission signal of the transmitter TRS0
(Ω) and the transfer function of the transmission line LINE1 is H ₁
(Ω), the winding ratio of the receiving transformer T ₁ is 1, the filter FI
Transfer function of L1 is F ₁ (ω), automatic pseudo line ALBO1
Let A ₁ (ω) be the transfer function of A, and G _{1 be} the amplification degree of the amplifier 1. Fourier transform Y of the output signal of the receiving circuit REQL
(Ω) is

[Equation 1] Becomes Near the center of the signal band

[Equation 2] The transfer function on the left side is designed so that

In the high frequency range, the expression (2) generally does not hold due to the cutoff characteristic of the filter FIL1, but this is not a problem because intersymbol interference does not occur in the signal after reception equalization. Intersymbol interference is sufficiently removed from the received output signal obtained by performing the inverse Fourier transform of Y (ω) in the equation (1).

On the other hand, regarding the transmission circuit, the transmitter TRS1
Let X '(ω) be the Fourier transform of the output signal of A, the attenuation amount of the attenuator ATT to be L, the transfer function of the filter FIL2 to be F ₂ (ω), and the transfer function of the automatic pseudo line ALBO2 to be A.
_{If 1} (ω), the amplification degree of the amplifier AMP2 is G ₂ , the winding ratio of the transmission transformer T2 is 1, and the transfer function of the transmission line LINE2 is H ₂ (ω), the Fourier transform of the input signal of the opposite receiver REC0 is performed. The transformation Y '(ω) is

[Equation 3] Becomes Here, H ₁ (ω) = H from the identity of the transmission system and the reception system
₂ (ω), F ₁ (ω) = F ₂ (ω), A ₁ (ω) = A ₂ (ω). Equation (3) is calculated using equation (1)

[Equation 4] Becomes Here, since the transmission signal pulse waveforms of the two transmitters TRS0 and TRS1 are generally the same, the Fourier transforms are also equal to X '(ω) = X (ω). Furthermore,

[Equation 5] If you set

[Equation 6] Becomes Since the inter-code interference is removed from the output signal of the receiving circuit REQL as described above, the inter-code interference is also removed from the input signal of the opposite receiver REC0 from the equation (6). That is, transmission equalization is automatically performed.

FIG. 8 is a circuit diagram showing an embodiment of the present invention. The filters FIL1 and FIL2 form a second-order BPF, and the Laplace transform F (s) thereof is determined by the inverse circuit condition of each element.

[Equation 7] Becomes Here, ω ₀ , Q, a are constants determined from the circuit constants.

The Laplace transform A (s) of the automatic pseudo lines ALBO1, ALBO2 has one low-pass pole and one mid-zero.

[Equation 8] Becomes Here, K ₁ , K ₂ , a ', and b are constants. In the figure, a capacitor C _DC is for cutting direct current, and has a diode D1 (D2) and an NPN transistor Q1 (Q2).
A parallel resistance is formed between the emitter and the base of AC in parallel with the signal. The value of their combined equivalent resistance is determined by the value of the direct current flowing from the positive power supply V _CC to the ground through the NPN transistor Q1 (Q2) and the diode D1 (D2). The larger the current value, the smaller the resistance value. NPN
The bases of the transistors Q1 and Q2 are AC grounded by the capacitor C, and the signals are diode D1 (D2) and N.
The PN transistor Q1 (Q2) is branched and passed.

The output voltage of the amplifier AMP1 is the high potential threshold V
_P and two comparators CM with low potential threshold V _N
P1 and CMP2 are compared with each threshold value. PN connected to the positive power supply V _CC for a period exceeding either threshold
The P transistor Q0 is turned on and charges the low pass filter LPF composed of the resistor R and the capacitor C. A DC component appears in the output voltage V _C of the filter LPF, and retains its value even when 0 is input to the received signal.

If the cable loss is large, the output signal level of the amplifier AMP1 is low and the time width over which the thresholds V _P and V _N are exceeded is narrowed. As a result, the charging current to the low pass filter LPF is reduced and the filter LPF output voltage is reduced. V _C also decreases. Therefore, the DC bias voltage applied to the series circuit of the NPN transistor Q1 (Q2) and the diode D1 (D2) is reduced, the current flowing through the series circuit is reduced, and as a result, the diode D1 (D2) and the NPN transistor Q1 are
The parallel equivalent AC resistance of (Q2) increases. Then, the attenuation amount of the automatic pseudo lines ALBO1 and ALBO2 decreases, and at the same time, the zero point moves to the low range. As a result, the high-frequency emphasis on the received signal is increased, and the automatic pseudo lines ALBO1, ALB are
O2 output level is increased, the output level of the amplifier AMP1 is increased, the threshold value V _P, the time width of over V _N becomes wider. In other words, negative feedback will be applied. Finally, the output level of the amplifier AMP1 becomes stable at a level slightly exceeding the thresholds V _P and V _N. At this time, the circuit constants are set based on the equations (2) and (5) so that the frequency characteristics of the automatic pseudo lines ALBO1 and ALBO2 match the cable loss. In this state, the frequency characteristic is optimally set on the transmitting side as described above.

The output impedances of the filters FIL1 and FIL2 are used to determine the automatic pseudo lines ALBO1 and ALB.
The input impedance of O2 is set high so that they do not affect each other.

Next, the state of equalization will be described with reference to the frequency characteristic diagram of FIG. FIG. 9A shows the bandpass filter FI.
It is a gain characteristic of L1 and FIL2. As is clear from the equation (7), there is a flat attenuation amount at a frequency lower than f _a = a / 2π, and there is a peak at f ₀ = ω ₀ / 2π. f ₀
Is generally chosen to pass most of the signal spectrum.

FIG. 9B shows the automatic pseudo line ALBO1, A.
It is a gain characteristic of LBO2, and the graph 1 shows the case where the cable loss is large, and the graph s shows the case where the cable loss is small. From the equation (8), by setting the circuit constants so as to be a'a, the receiving circuit REQL and the transmitting circuit TEQ are set.
The gain of the entire L is as shown in FIG. In other words, the greater the cable loss, the lower the zero point moves to the low range (f
_l ) and the gain is also high (L _l ). This is b in equation (8)
Is smaller. The fact that b becomes small is an effect of the above-mentioned negative feedback. Zero point frequency b / 2 and attenuation amount (b−K ₂ ) of the automatic pseudo line ALBO1 shown by the equation (8).
The relationship of / K ₁ is the straight line shown in FIG.

Next, description will be made with reference to the timing chart of FIG. The five graphs on the left side of FIG. 11 show the case where the cable loss is small, and the five graphs on the right side show the case where the cable loss is large. The larger the cable loss, the lower the input level to the filter FIL1 and the lower the output level of the amplifier AMP1. Therefore, the time width of exceeding the thresholds V _P and V _N is narrow, and as a result, the time during which the switching PNP transistor Q0 is conducting is shortened and the charging current to the low pass filter LPF is reduced, and the output voltage of the filter LPF is reduced. V _C becomes lower. Therefore, as described above, the attenuation amount of the automatic pseudo line ALBO1 stabilizes at the reduced value (L ₁ ). Next, the operation of the transmission circuit TEQL will be described with reference to the timing chart of FIG. Attenuator ATT
The frequency characteristics of the signal attenuated by are emphasized in the high frequency range (Fig. 1
2 (b)), the high frequency band is attenuated and appears as a waveform without intersymbol interference in the counter receiver REC0 after being transmitted through the cable (FIG. 12 (c)).

[0032]

As described above, according to the transmission signal transmitter / receiver of the present invention, the signal attenuation amount of the line is determined from the received signal by utilizing the fact that the lines on the transmitting side and the receiving side are generally the same cable. However, there is an effect that the transmission signal can be automatically corrected without receiving any control from the outside. Therefore, there is no need for a person to prepare the line length data, to observe the transmission signal waveform in the middle of the cable, and to redo these every time the line length is changed. However, since each line has the same tendency with respect to frequency, there is an effect that the transmission correction function can be used for various lines without modification. Further, the operation in the case where the transceiver without the correction function is provided on one side is explained, but it is clear that the effect is the same even when the transceiver according to the present invention is provided on both sides. Since the amount is corrected, there is an effect that it can be transmitted over a longer distance.

According to the transmission / reception equalization circuit of the present invention, the control signal corresponding to the cable loss generated from the reception circuit is also used in common in the transmission circuit, so that either one of the opposing transceivers can be used. This circuit has the effect that it is not necessary to manually adjust the transmission equalization circuit since it is only necessary to install this circuit on the side.

[Brief description of drawings]

FIG. 1 is a functional block configuration diagram of a transmission signal transmitter / receiver according to an embodiment of the present invention.

FIG. 2 is a connection diagram showing a usage example of the present invention.

FIG. 3 is a characteristic diagram of an example of frequency characteristics of signal attenuation of a line.

FIG. 4 is a signal waveform diagram showing waveforms at various points in FIG.

5 is a functional block diagram of a transmission equalization amplification unit shown in FIG.

FIG. 6 is a block diagram of an embodiment of the present invention.

FIG. 7 is a block diagram of the entire system including the facing.

FIG. 8 is a circuit diagram of an embodiment of the present invention.

9 is a frequency characteristic diagram of the receiving circuit shown in FIG.

FIG. 10 is a characteristic diagram of the automatic pseudo line shown in FIG.

FIG. 11 is a timing diagram of the receiving circuit shown in FIG.

12 is a timing diagram of the transmission circuit shown in FIG.

FIG. 13 is a functional block diagram of a conventional transmission signal transceiver.

[Explanation of symbols]

 10 reception transformer 11 transmission transformer 12 attenuation determination unit 13 reception equalization amplification unit 14 identification unit 15 transmission equalization amplification unit 20, 21 lines 40 ROM address generation unit 41 waveform ROM 42 D / A converter 43 counter 44 AND gate T1 reception Transformer T2 transmission transformer AMP1, AMP2 amplifier FIL1, FIL2 band pass filter ALBO1, ALBO2 automatic pseudo line PDET peak detection circuit LPF low pass filter ATT attenuator TRS0, TRS1 transmitter REC0, REC1 receiver REQL reception equalization circuit TEQL transmission equalization circuit

Claims (2)

[Claims] 1. A transmission signal transmitter / receiver for transmitting / receiving information between a plurality of points via a transmission medium having an attenuation characteristic with respect to a transmission signal amplitude, wherein a reception signal received through the transmission medium attenuates the transmission medium. A transmission signal transmitter / receiver comprising: an attenuation amount determination means for estimating the amount; and a transmission signal correction means for multiplying the original signal waveform by an inverse characteristic of the attenuation characteristic of the transmission medium based on the attenuation amount. .. 2. A waveform equalization circuit connected to each of a transmission line and a reception line of a four-wire type communication line, wherein a first band pass filter for passing a signal band component of a received signal and a control signal level Due to the increase, the transmission frequency of the transmission signal is made to pass through the first pseudo line in which the gain frequency characteristic including the first band pass filter is pseudo and the first amplifier in order to the loss frequency characteristic of the line with less loss. And an attenuator and a second bandpass filter having the same configuration as the first bandpass filter.
Of the bandpass filter, the second pseudo line having the same configuration as the first pseudo line, and the second amplifier in order, and the low pass filter is used when the peak of the output of the first amplifier exceeds the fixed threshold value. A transmission / reception equalization circuit comprising a peak detection circuit for preventing discharge of the low-pass filter when it is charged and does not exceed, and giving an output of the low-pass filter as a control signal for the first and second pseudo lines.