SU1570014A1 - Device for duplex transmission of signals - Google Patents

Abstract

The invention relates to telecommunications and may find application in digital information transmission systems. The aim of the invention is to increase the communication range by increasing the degree of suppression of the signal of the own transmitter at the input of the receiver. To achieve this goal, a master oscillator 9, a pseudo-random sequence generator 10, a first switch 7, a second switch 8, a shaping filter 5, and an adder 6 are entered. After a certain number of iterations, the amount of correction signal for all possible combinations of transmitted signals is accumulated in the memory block. 2 Il.

Description

O1

 about

1

The invention relates to telecommunications and may find application in digital information transmission systems.

The purpose of the invention is to increase the communication distance by increasing the degree of suppression of the signal of the own transmitter at the input of the receiver.

Figure 1 shows a structural electrical circuit diagram of the device; Fig. 2 is a structural electric circuit forming filter.

The device contains a transmitter 1, receiver 2, differential amplifier 3, mode control block 4, forming filter 5, adder b, the first switch 7, the second switch 8, the master oscillator 9 and the generator 10 of a pseudo-random sequence, and the forming filter 5 contains the shift register 11, a decision block 12, a counter 13, a memory block 13, an adder 15 and a digital-to-analog converter 16

The device for duplex signaling operates as follows.

There are two modes of operation of the device: the setting mode and the transfer-receiving mode set by the mode control unit 4 The setting mode is set when the service information is received from the digital information source, which is decoded by the mode control unit 4 and a signal is output to its output the input of the first switch 7 and the second input of the second switch 8. The first switch 7 connects the output of the pseudo-random sequence generator 10 to the first input of the transmitter 1, and the second mmutator 8 connects the differential force output

bodies 3 with the first input of the shaping filter 5. Since the communication line connected to the output of the adder 6 has a reactive input resistance, prior to setting up the device, the srgnals at the output of the transmitter 1 and at the output of the adder b differ in amplitude, phase and shape from each other, and the amplitude of each of the samples of the transmitted signal at the output of the adder 6 is determined with the convolution of the samples of the impulse response of the adder 6 loaded on the reactance of the line and the samples of the output signal of the transmitter 1. When

assuming that the pulse response is a finite duration of N clock intervals, and the amplitude of each of the samples of the transmitted signal b. at the output of the adder 6, only the N last transmitted symbols are affected. Thus

-, - LAM.

(five)

5 d

five

Q

five

five

0

five

where h. - Pulse response counts. but. - transmitter output signal samples, 10

In order to completely suppress the transmitted signal at the input of receiver 2 using differential amplifier 3, it is necessary that the signals at the outputs of transmitter 1 and adder 6 are the same. Thus, the device setup consists in changing the parameters of the shaping filter 5 so that it synthesizes From the transmitted sequence, the signal, adding in the adder 6 to the output signal of the transmitter 1, has distorted it, compensating for the effect of the communication link reactivity. Therefore, after adjusting the shaping filter 5, the signals at the output of the transmitter 1 and the adder 6 are equal.

To adjust the shaping filter 5, a pseudo-random sequence 2N-1 characters long is used, which from the generator output 10 of the pseudo-random sequence through the first switch 7 enters the inputs of transmitter 1 and shaping filter 5. While the shaping filter 5 is not configured, the signals on the first and second inputs of the differential amplifier 3 differ in amplitude, shape and phase. The signal at the output of the differential amplifier 3 is proportional to the difference of the signals at its inputs. This signal through the second switch 8 is fed to the first input of the shaping filter 5 and changes its characteristics so as to reduce the value of the difference signal at the output of the differential amplifier 3 "

The configuration mode is terminated when the code mode control unit arrives at the input 4, the end of the setting from the digital information source output. The signal from the mode control unit 4 output is fed to the third input of the first switch 7, which i

turns off the pseudo-random sequence generator 0 output from the transmitter 1 input and the second input of the shaping filter 5 and connects the output of the digital information source to the transmitter input S and the second input of the second switch 8, which disconnects the output of the differential amplifier 3 from the first input of the shaping filter 5. After This sets the send-receive mode. During the communication session, the parameters of the shaping filter 5 remain unchanged.

Forming filter 5 works as follows. Since, as mentioned, the amplitude of the transmitted signal at the output of the adder 6 is uniquely determined by a combination of the N last transmitted symbols, to correct it, it is enough to extract from the memory block 14 at the address determined by the last N transmitted symbols the correction signal count analogue converter 16 to analogue and fold in adder 6 with a count of the output signal of transmitter 1. Since the amplitude of the output signal of adder 6 can vary over the duration of one th clock interval, it is necessary to carry out the correction of n times per clock period after a time t, wherein theorem At Kotel'nikova J

- Fg, where F g is upper bound

transmit spectrum frequency

Therefore, in the device, the formation of the address at which the reference value of the correction signal is stored is performed as follows. N higher bits of the address inputs of the memory block 14 are connected to the outputs of the sequential shift register 11, in which the N most recently transmitted symbols are stored, M the lower bits of the address..yhogs of the memory block 14

50

connected to the outputs of the counter 13, to the input of which a regular sequence of frequency nft is fed, fT is the clock frequency, from the second output of the master oscillator 9, therefore the outputs of the counter 13 are 55 but the binary number from 1 to p. . The shift register 11 is produced with a clock frequency fT. Consequently,

During the time while the output of the shift register i1 remains the next combination of transmitted symbols, all possible numbers from 0 to n appear at the outputs of counter 13. Thus, the binary number at the address inputs of the memory I4 at each time determines the address one of the n samples of the correction signal on the duration of the last transmitted symbol

The shaping filter 5 is set up adaptively using a sign adaptation algorithm.

sixteen)

0

l

ea

e

where e.

+ l sign g.,

1M

- estimation of the error (difference) of the voltages at the output of the transmitter 1 and 0 of the adder 6 at the i-th step;

L - the size of the adaptation step. „, - the signal at the output of the differential amplifier 3, and

25

G. e.

+ i

(7)

0

where p. is additive noise.

The sign of the error is determined in decision block 12, the input of which supplies a signal from the output of the differential

Q amplifier 3. From the output of block 12, the first input of the adder 15 is supplied ± & (usually & - the low-order unit of the correction number recorded in memory block 14). The second input of the adder 15 is fed to the contents of this cell of the memory block 14, which, after changing the addition ±), is written to the same cell.

Q Thus, after the operational number of iterations, in memory block 14, information is accumulated on the magnitude of the correction signal PL of all possible N-bit combinations of transmission signals.

In the transfer-receive mode, the second switch 8, at the command of the mode control unit 4, disconnects the input of the decision block 1 2 from the output of the differential amplifier 3, and during the communication session the contents of the memory block i4 do not change - it only works for reading.

Claims (1)

 Invention Formula A device for duplex signal transmission, comprising a transmitter, a mode control unit, a serially connected differential amplifier and a receiver, the output of which is the subscriber output of the device, whose subscriber and linear inputs are respectively the input of the mode control unit and the first input of the differential amplifier, characterized by that, in order to increase the range of the SVYaei by increasing the degree of suppression of the signal of its own transmitter at the receiver input, sequentially The master oscillator, the pseudo-random sequence generator and the first switch are connected in series to the second switch that forms the filter and the adder, the second input of which is connected to the transmitter output and the second input of the differential amplifier, and the output to the first input of the differential amplifier is connected to the second input the first switch, the output of which is connected to the first input of the transmitter and the second input of the shaping filter, the third input of which is connected to the second Odom oscillator, which first vyhrd under the keys to the second input of the transmitter output mode control unit connected to the third input of the first switch and the second input of the second switch having a first input connected to the output of the differential amplifier.