JPS59231931A - 2 wire-4 wire converting circuit - Google Patents

Abstract

PURPOSE:To decrease power consumption and to attain high accuracy by synthesizing an actual impedance from impedance circuit networks multiplied by <=2 conatants (>1). CONSTITUTION:A means 1 detects a difference signal S1 of a 2-wire line TR and a means 2 deletes only a signal component S2 of a 4-wire input line RX from the signal S1 and detects it as a signal S3 of a 4-wire output line TX. A means 3 outputs a weighted sum between a signal S4 proportional to the signal S3 and inversely proportional to the impedance of a 2-terminal circuit network 6 and a signal S5 inversely proportional to the impedance of a 2-terminal circuit network 7 and proportional to the signal S2 as a feedback signal S6. Further, means 4, 5 input the signal S6 so as to generate currents opposite phase to each other and transmit a signal on the input line RX to lines T, R while being respectively coupled with the lines T, R and transmit an incoming signal to the line TR to the output line TX, causing the leakage of the signal from the input line RX to the output line TX to be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a 2-wire to 4-wire conversion circuit that couples a 2-wire line and a 4-wire line used in wired communications.

<Prior art> In wired communication, a two-wire line for two-way communication and a four-wire line for one-way communication are combined, and the signal from the two-wire line is guided to the four-wire output line, Signal from input line 2
A 2-wire to 4-wire conversion circuit is used that leads to the wire line and cancels the wrap-around signal from the 4-wire input line to the 4-wire output line.

Conventionally, a so-called transformer hybrid circuit using a transformer is well known as a first example of this type of circuit.

As a second example, with the electronicization of communication equipment in recent years, an impedance network is used to simulate the signal transmitted to the two-wire line from the signal of the Type 44 input line, and the signal is actually transmitted to the two-wire line. Keiichi Y is an electronic hybrid circuit that uses an electronic circuit to subtract this simulated signal from the signal generated on the railway line to eliminate the detour signal.
asuda, Koichi Hase-gawa a
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Furthermore, as a third example, from the point of view of electronically synthesizing the input impedance of a two-wire line, it is possible to detect the differential voltage of the two-wire line and apply feedback to the signal source that generates the signal to the two-wire line. , There is a method to control this amount of feedback using an impedance network inside the feedback circuit and realize the necessary input impedance. W, AULL, D, A, 5P
IRES, P, C, DAVIS and S, F.

MOYER″A High-Voltage ICfo
r a Transformer-1ess Tru
nk and 5ubscriber Line
Interface IEEE Journal
of 5old-5tate C1rcuits,
Vol.

5C-16, No, 4. August 1981.

The impedance values that determine the signal transfer characteristics in such a hybrid circuit include the terminal impedance ZT of the two-wire line, the signal sending impedance Z8 to the two-wire line, and the two-wire line connected to the hybrid circuit. There is a load impedance zL1, which is a composite impedance of the line and the terminal, and serves as a load of the hybrid circuit, and a balance impedance zn that simulates this load impedance. Of these, it is well known that it is particularly important that the values of ZL and zB match in order to attenuate the wrap-around signal from the 4-wire input line to the 4 mm output port. Further, zT and Za generally take the same value.

By the way, in the existing hybrid circuit, zT.

Three or more impedance networks are required to synthesize zB, zB. For example, in the transformer oct hybrid circuit of the first example, one impedance network (e.g., 600Ω is used) between the four-wire input line and one terminal of the four-wire line-side winding of the transformer. , Trance no 4
One impedance network (e.g. 600 Ω) between the opposite terminal of the wire line winding and ground, and four impedance networks of the transformer
Three impedance networks are required, such as a balance network between the midpoint of the wire line side winding and ground.

In addition, in the second example of the electronic hybrid, the ZT is configured by the impedance of an impedance network connected between the lines of the two-wire line, and the differential voltage of the two-wire line is detected by the high-impedance amplifier. The signal on the 4-wire input line is transmitted to the 2-wire line, and the signal is transmitted to the 28-wire line.
Using an impedance network proportional to zB and zB, the two-wire line voltage is simulated using an operational amplifier, etc., and the difference between the detected differential voltage is taken and the wrap-around signal is erased. impedance network.

Furthermore, even when using the feedback circuit of the third example, there is one impedance network for 21 synthesis, two impedance networks proportional to ZT I Za for wraparound prevention, and two wires from the four-wire input line. In order to achieve the desired transfer characteristics to the 4-wire system input line,
One impedance network proportional to , and a total of four impedance networks are used below.

Furthermore, the second and third examples of the latter are aimed at downsizing the circuits through electronicization, but the feature of these circuits is that the wrap-around cancellation circuit can switch from the 4-wire input line to the 2-wire line. It is configured so as not to affect the transfer characteristics leading to ZT, 28 synthesis.
Two impedance networks proportional to ZT z ZB are required for wraparound prevention independently of the two impedance networks, essentially requiring three or more impedance networks.

In addition, in the 71 hybrid circuits of the first, second, and third examples, even if the balance impedance zn matches the load impedance zL, if ZTNzL, the connection from the 4-wire input line to the 2-wire output record is impossible. There are five drawbacks in that the transfer characteristics have frequency characteristics and cause waveform distortion. In other words, this drawback is that the transfer characteristics from the 4-wire input line to the 2-wire output line in the first, second, and third examples are all impedance z8=
Since the signal is multiplied by an equivalent circuit that supplies a signal from a signal source having zT to a load impedance zL, even if ZB=ZL, if ZL/Z8 is not a real number, the transfer characteristic has a frequency characteristic.

<Objective of the Invention> An object of the present invention is to provide a 2i-4 line conversion circuit in which the number of impedance circuit networks for synthesizing ZT+28sZB is two or less.

Another object of the invention is to use an impedance network that is a constant multiple of the actual zT, zs, zB to
*An object of the present invention is to provide a 2-wire to 4-wire conversion circuit that achieves reduction in circuit power consumption and higher accuracy by combining ZB+ZB.

5 Still another object of the present invention is - Any 2
To provide a 2-wire to 4-wire conversion circuit having a transfer characteristic without frequency characteristics from a 4-wire input line to a 2-wire output line.

<Summary of the Invention> The 2-wire to 4-wire conversion circuit of the present invention includes a first means for detecting a difference signal of a two-wire line, and a difference signal obtained from the first means for detecting a difference signal of a four-wire line. The second one erases only the signal component and detects it as the 4g signal of the 4-wire output.
a signal proportional to the signal on the 4i output line and inversely proportional to the impedance of the 41 two-terminal impedance network; and a second two-terminal impedance network proportional to the signal on the 4-wire power line a third means for generating a weighted sum with a signal inversely proportional to the impedance of the circuit network as a feedback signal; and fourth and fifth means for respectively generating currents of opposite polarity by inputting the feedback signal. , coupling one of the fourth means and one of the two-wire lines;
and the other of the two-wire line, transmitting the signal of the four-wire power line to the two-wire line,
The present invention is characterized in that the signal arriving from the wire line is transmitted to the 4-wire output line, and the signal is routed from the 4-wire A input line to the 4-wire output line.

<Description of Embodiments> Next, embodiments of the present invention will be described with reference to two drawings.

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the 2-wire/4-wire conversion circuit of the present invention. The block 1 is connected to the 2i type lines T and H, and is means for detecting a difference signal S1 between the input signals SO from the 2i type lines T and R. Block 2 connects the difference signal S1 detected by block 1 with the 4-wire input &amp;
This means performs weighted addition of the IRX signal S2 with a polarity that eliminates the amount of wraparound, and detects it as the signal S3 for the four-wire output line calculation. Block 3 operates with a first two-terminal impedance network 6 with impedance zT' and a second two-terminal impedance network 1147 with impedance zS3 and connects the four-wire output line T.
A signal S4 proportional to the signal S3 of This is means for generating a weighted sum of the signal s5, which is inversely proportional to the impedance ZB', as the feedback signal S6. Blocks 4 and 5 are two-wire line voltage generation current sources that receive the feedback signal SO as input and generate signal currents of opposite polarity. Outputs of current sources 4 and 5 for generating 2-wire line voltage and T or R of 2-wire line
are combined. Note that even if this coupling occurs through impedance, it does not affect the effects of the present invention.

The weight in the weighted sum used in the explanation of each block above is determined by how the signal level in the circuit is determined, and when realizing the circuit, phase reflection,
Although various variations such as constant multiplication are possible, as long as the variations are based on the operation according to the principle formula as described later, they are included in the scope of the present invention.

Next, the qualitative operation of the circuit shown in FIG. 1 will be explained.

Block 1 removes the in-phase signal generated at the end of the two-wire gland and detects only the difference signal S1. This difference signal Sl is 4
This is the sum of the signal S2 input from the wire input line PX and transmitted to the two-wire line, and the signal SO arriving via the two-wire line. Therefore, in block 2, this difference signal S1
By subtracting the signal S2 of the 4-wire input line PX from the 4-wire input line PX, it is possible to detect only the signal SO that has arrived via the 2-wire line and obtain the signal S3 of the 4-wire output line.

The input impedance zT of the circuit seen from the two-wire line is
If block 1 has a high input impedance, it is determined by the current variation of the two-wire line voltage generation current source with respect to input voltage variation. The current fluctuation of the current source for generating the two-wire line voltage is variable by the first impedance network B constituting the feedback system, and as described later, the input impedance 2τ is changed by changing the impedance value of the first impedance network 6. It can be a constant multiple of zT'.

Considering the transfer characteristics from the 4-wire input line to the 2-wire line, it enters the feedback system from the 4-wire input line through the block 2 and the second impedance network 7, and as described later,
A first impedance network 6 generates a signal to a two-wire line with a variable delivery impedance. This signal is controlled by the load impedance zL of the two-wire line by the impedance value zB' of the second impedance network 7.
It is possible to correct the frequency characteristics of It is.

The block 1 detects the difference signal S1 of the 12-wire line at 1 times the amplitude, the block 4 outputs a current with an amplitude 560gm times the feedback signal output by the block 3, and the block 5 detects the feedback signal S6.
It is assumed that a current with an amplitude -gm times that of -gm is emitted, and the transfer function from the 14-wire input line PX to the 2-wire line, and 2! A circuit is set in which the transfer functions from the IT line to the four-wire output line TX are both 1.

In order to obtain this characteristic, block 2 and block 3 in Fig. 1. 2-terminal impedance network 6, 7. 4-wire input i
The portion including the RX and 4.11 output iTX and extending from the output s1 of block 1 to the output s6 of block 3 may be constructed with a circuit having characteristics as shown in FIG. That is, the output S1 of block 1 in FIG.
The signal s2 of the M-type personnel line ■ is subtracted, resulting in the signal s3 of the 4-wire type departure lineman.

This part corresponds to block 2 in diagram M1.

The signal s2 input from the 4i type input line bar is multiplied by 1/gm'·281 in block 6 and added in adder Mη, and becomes part of the feedback signal S6. The signal S3 of the 4-wire output line is multiplied by 1/grn'·211 in block 7 and sent to adder A.
It is subtracted by D2 and becomes part of the feedback signal s6.

The feedback signal S6 produced by the weighted sum in adder AD2 produces an output corresponding to the output of block 3 in FIG.

In such a circuit, the input impedance Z1n of the circuit viewed from the 2R type line is as follows.

When the differential voltage of the two-wire line changes by V, the two two-wire line voltage generating current sources have opposite polarities and 1 = grr
Since it absorbs the current v'grd ZT'・V, Zi
n”ZT・・・・・・・・・
......(2).

Next, when the load impedance of the two-wire line is z,
From the signal voltage VRX of the 4-wire input line ■ to the signal voltage v of the 2-wire line 2! When determining the transfer function H4g to W, the pressure generating current source causes a current gm times as much as this to flow through zL, and the voltage across zL becomes VIIW, so the following equation holds true.

(-g.IZTIvllW+(gn1/zTI+g11
1/zBl)74w)×gm ZL ”' v, w
・・・・・・・・・・・・・・・ (3) If we transform the equation (3) and set ZT' = mZT, gm' = -gm, then H4□=Fish=-IL ZT 10 ZBll
H+++, (4゜VRX ZT ＋Z1. ZB That is, from the theory that Zn = zL, ' H4
11=1, and the frequency characteristics become flat.

Also, when the load impedance of the 2-wire line is Zl, the signals s2 to 41j! on the 4-wire input line are The transfer function H44 of the wrap-around amount of the signal reaching the signal S3 of the output line TX is, if ZB:ZL, then from the formula (4), H42=1
Therefore, the signal S of the fourth input line RX in the adder ADI
By subtracting 2, H44=0.

Similarly, the transfer function from the two-wire line to the four-wire output line is 1.

The number of impedance circuit networks required in the above circuit configuration is 1 and 2 impedance circuit networks, 6.7.

Next, the basic configuration shown in FIG. 1 will be explained in more detail with reference to the circuit diagram shown in FIG.

Operational amplifier 11 detects difference signal S1 of two-wire line signal SO together with resistors R11 to R14. Here R11/R
12 = R1 14. Voltage of 2-wire line T and H is 1 each
VT and vR, the amplitude of the output of the operational amplifier 11 is '0v, -vR, D-□1a,'.

Wow. Tsuke, yo.

Detects only the DC component of the difference signal S1, and accordingly, 2
Operational amplifier 4 that allows an appropriate loop current to flow through the wire line
Although this is a means for determining the DC operating point of 1.51, the details are omitted here.

The output S1 of the operational amplifier 711 is DC-cut by the capacitor C1, and only the exchange signal is transmitted to the subsequent stage.

The operational amplifier 21, together with the resistors R21 to R23,
.

The signal S2 of the 4-wire input line is subtracted from the difference signal ''S1 detected by the amplifier 11 to obtain the signal S3 of the 4-wire output line TX.

The operational amplifier 81, together with the first impedance network 6, the second impedance network 7, and the resistor R31°,
A return signal S6 is generated to the operational amplifier 41.51. Here, the resistance R31 is selected to be 1/gm'.

The operational amplifier DPI, together with resistors R1 and R2, inverts the signal S2 on the four-wire input line (2). Also, operational amplifier OP2
is the output signal S of the operational amplifier 31 along with the resistors R3 and R4.
6 is reversed to generate a signal light. Operational amplifiers 41 and 51 are connected to resistors R41, R42, R43, R44, and resistor R, respectively.
Together with 51°R52, R53, and R54, they constitute line zero pressure generating current sources 4 and 5 that generate voltages of opposite polarity. To explain the operation of this current source 4 from the side of the stage amplifier 41, by selecting R42=R44 and R41=R43, the voltage-current conversion coefficient gm of the current source 4 becomes gm=
Then, 141=1/R43. The operation of the current source 5 on the operational amplifier 51 side is also similar. The output signal s6 of the operational amplifier 31 is applied to the operational amplifier 41 side and the output signal s6 of the operational amplifier 31 is applied to the operational amplifier 51 side, respectively, with the DC component cut off by capacitors C2 and C3.

The outputs of the current sources 4 and 5 are directly connected to the 2@ type lines T and H. By selecting R11 to R14 to be large compared to the impedance of the two-wire line, the differential voltage detection circuit 1 including R11 to R14 can be isometrically considered to have high impedance. - As an example, in this circuit, R11=R12=R1
3=R14, R21=R22=R23, R31=rr7
R41, R1=R2, R3=R4, R41=R43=R
51=R53°R42=R44=R52=R54, ZT
By setting '=mZT, ZB'=ZB'V4, the characteristics shown in the above-mentioned principle can be obtained.

<Effects of the Invention> As explained above, the present invention can reduce the number of impedance elements required by the 2@-4i conversion circuit to two by adopting the circuit configuration as described above, and can also reduce the number of impedance elements required by the 2@-4i conversion circuit. This has the effect of making the frequency characteristics from the line to the two-wire line flat for any load impedance zL.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is a block diagram specifically showing the main parts of FIG. 1, and FIG. 3 is a block diagram showing the basic configuration of an embodiment of the invention. FIG. 3 is a circuit diagram showing the embodiment in further detail. T, R... 2-wire line... 4-wire passenger line''
■...4-wire output line 1 river...first means 2...
・Second method 3・Song・Third method 4・・・・
・Fourth means 5...Song fifth means 6.7...
First and second impedance network “Ct!MAR original
Town,・、ノ＼−−″・′

Claims (1)

[Scope of Claims] In a circuit network that couples a two-wire line, a four-wire input line, and a 124-wire output line, a first means for detecting a difference signal of the two-wire line; 1st
a second means for eliminating only the signal component of the four-wire input line from the difference signal obtained from the means and detecting it as a signal of the four-wire output line; and a weighted sum of a signal that is inversely proportional to the impedance of the first two-terminal impedance network and a signal that is proportional to the signal of the four-wire input line and inversely proportional to the impedance of the second two-terminal impedance network. The third signal is the return signal.
and fourth and fifth means each receiving the feedback signal as an input and generating currents of opposite polarity to each other, one of the fourth means and one of the ZIFI type lines are coupled, and ,
coupling one of the fifth means and the other of the two-wire line, transmitting the signal of the four-wire input line to the two-wire line;
Said 2jI! ! A 2-wire to 4-wire conversion circuit that transmits a signal arriving from a 4-wire type line to a 4-wire type output line, and minimizes signal wraparound from the 4-wire type input line to the 49-type output line.