SU1628206A1 - Commination line - Google Patents

Abstract

The invention is intended for use in communications technology. The purpose of the invention is to increase the noise immunity under narrowband and impulse noise conditions. The communication line on the transmitting side contains a source of information 1, a block 2 of time-frequency shift, an adder 4 and a transmitter 6, and on a receiving side a block 3 of time-frequency shift, a delay line 5, a receiver 7, compensators 8 and 9, block 10 noise suppression and limiting amplifier 11 o Form the transmitted signal as a sum of two signals, one of which is offset from the other in time and frequency. At the receiving side, the signals are separated. Then, one of them is subjected to a time-frequency shift operation. Thereafter, the signals are summed. Since the interfering components are shifted relative to one another in the time and frequency axes in block 3 of the time-frequency shift, they are eliminated without damaging the desired signal, by generating interference estimates in block 10 and subtracting them from the received signal. 4 hp f-ly, 5 ill. (L

Description

The invention is intended to transmit discrete information under conditions of nomeh.

The purpose of the invention is to improve noise immunity under narrowband and impulse noise conditions.

Figure 1 shows a structural electrical circuit of a communication line; figure 2 - the same compensators; on fig.Z - block time-frequency shift of the transmitting side; figure 4 - the same, the receiving side; 5 shows an interference suppression unit.

The communication line contains a source of 1 information; blocks 2.3 of the time-frequency shift; adder 4, delay line 5, transmitter 6, receiver 7, compensators 8.9, interference suppression unit 10, limiting amplifier 11.

Compensators 8.9 contain an adder 12, a phase shifter at 90 ° 13, amplifiers 14.15, integrators 16.17, multipliers 18.19.

Block 2 of the time-frequency shift of the transmitting side contains mixers 20,21, local oscillators 22,23, delay line 24.

Block 3 of the time-frequency shift of the receiving side contains mixers 25, 26, delay line 27, local oscillator 28, generator 29 j voltage controlled, phase detector 30, low pass filter 31

Interference suppression unit 10 includes subtractors 32.33, controlled notch filters 34.35, keys 36, 37, adder 38, amplifier 39, control block 40, memory element 41, controlled oscillator 42, mixer 43, narrowband filter 44, line 45 delays, 46 high-pass filter, 47 low-pass filter, amplitude detectors 48.49, threshold blocks 50.51.

The communication line works as follows.

On the transmitting side, signal source 1 generates a signal S (t) (with FM, TH, or OFT). Block 2 frequency, time shift shifts the signal

Sj (t) along the frequency axis by the magnitude DЈ and delays it in time by ut, thus forming the signal), S2 (t) S (t). The signal level of Si (t) and Sz (t) is the same. At the output of the adder 4, a sum signal SgXt) S (t) + S (t) is formed, which is emitted into space by the transmitter 6 and the transmitting antenna.

The line is designed to operate under conditions where the width of the spectrum of the narrowband interference is P, –A, and many are already the spectral widths of the PS, Pn & Ps signal. The magnitude of the frequency shift Df in block 2 must be greater than Pn, P,

It is easy to see that the signals S ((t) and 8l (t) are uncorrelated at coinciding moments of time. Indeed, let FM, S (t) U0cos w0t + q (t), where U0, 00, is the amplitude, center frequency and the initial phase of the signal; tf (t) is a random phase change carrying information. Then the coefficient

correlations of the processes S (t) and S (t)

8.8 „UoCOsCcDot +4 (t) + (CQo + 2fiuf) (t -Ut) + Cj (t -At) + J

 ujcos fiift - (C00 + 2faf) At + q (t) -cf (t -At).

It is easy to see that the average value of this component is zero, since for any D. f 0 0 cos 2 / u & ft 0. At the receiving side, an external signal is added to the sum signal S (t)

interference 7 (t), while at the output of the receiver 7 the signal U (t) S (t) + + S (t) + (t), interfering | f (t :) and v (t) are separated by frequency and time - change. This allows them to be removed from the desired signal. In the case of impulse noise, the signal of one input (where it is present) is blanked, and instead of it, the signal of another input is used, where there is no interference at the moment, and vice versa.

In the case of narrowband interference from a single input signal, the spectrum is rejected where the interference is concentrated. Instead of the cut out part, a signal is placed with the same spectral region that was cut from the signal of another input, and there is a narrow interference in another spectral region, but in the considered one, it is absent. Thus, the interference is removed, and the signal is recovered. Similarly, the signal is processed.

five

0

five

0

another entrance. Thus, at the output of the interference suppression unit 10 there is a cleared signal), which is fed to the limiting amplifier 11 and then to the reference input of the first compensation unit and to the output of the communication line as a whole. The amplifier-limiter 11 is needed to stabilize the operation of the units during the transition process mode setting.

Compensators 8.9 (Fig. 2) are intended to remove from the voltage of the signal input (c) those components that are correlated with the voltage of the reference input (0).

Let the gains of the first 14 and second 15 adjustable amplifiers be q and q, respectively.

The input signal (s) at point 10

Z

- Uc (t)., The input signal (0) at point 11 and Uo (t), the output signal of the adder 12 and the compensation unit U Ug- (t). Let U0 (t) denote the signal U0 (t) that passed through the phase shifter 13 at 90e. Then + + + q2Uo. At the outputs of the first 18

and the second 19 multipliers (at points 13 and 14) of the voltage

because u0uq oh uj itЈ

These stresses are applied to rators 16 and 17, and their output rolls control the coefficients q, q, and adjustable forces. Thus, the values of q and are determined by the formulas

qX,

2

kuo

cumulative gain for the corresponding feedback loop.

The integrators 16, 17 will be rearranged until the voltage at their inputs is zero.

With

by this

/ 2

i b 0

H, o °; UcUo

+ - 0 and the coefficients q ,, are defined as

UcUo

and;

Cho

UcUo

AND

They can be combined into one complex factor, describing Uc and U0 with complex signals. In this case

TO

m

/ ucfz

ig

-Mli

(In the following, we omit the point above the notation, assuming complex signals).

The latter formula describes the fact that only those components of the Uc signal that are uncorrelated with the UQ signal are passed to the compensator output.

Consider the operation of block 2 time-frequency shift (fig.Z). The input signal after passing through the mixer 20 is shifted upward along the frequency axis.

but

s

th 20

ten

15

35

40

at frequency fj. Further, in mixer 21, it shifts down the frequency axis.

The sinusoidal oscillations f are generated by the frequency f f or the frequencies fj

Vym 22 and second .3 heterodyne. The frequency ff and f t satisfy the conditions f - f fif. The signal is then delayed by a delay line 24 of At. Thus, after the signal passes the first block of the time-frequency shift, it acquires the required frequency shift by D f and time by & t.

Consider the operation of block 3 time-frequency shift (figure 4).

It also shifts

signal frequency at DЈ and time at At. For this, the signal is passed through a mixer 25, where it is shifted upward along the frequency axis to a frequency with the help of a local oscillator 28, producing a voltage with a frequency f-). The signal then moves down.

25 along the frequency axis in the fourth mixer to the frequency Јf generated by the frequency-controlled local oscillator 28. Thereafter, the signal is delayed in time by the amount of Ate using

30 line 27 delay. The frequencies f and Ј4. must satisfy conditions if

  14.

The circuit of the frequency-time shift block 3 differs from the circuit of block 2 in that the phase detector 30 and filter 31 are present here. This chain serves to neutralize the frequency instabilities of the local oscillators 22, 23, 28. Due to the frequency instabilities, the D f value provided by on the transmitting side, it may differ slightly within the limits of the value of AH provided on the receiving side. In this regard, the frequency-controlled 45 local oscillator 28 can be tuned in frequency within small limits (these limits are determined by the instability of the three local oscillators).

50 A phase locked loop is used for trimming. The parameters of the filter 31 are chosen so as to pass only slow changes due to instabilities. The comparison is made with a reference input signal. At the reference input there is a signal Sc + S. At the signal input at point 16 there is also a signal S c + S

(during the transition process, at the end of the component SЈ in this signal disappears). After line 29 delayed watts. 17, there is a signal U, .-

 -Vgggtst1

 (S4 + S-)

w

In signal

1 S7 + ° v

4 I. - h / S only the components of S are correlated

U

but

with signal S, +

H

According to them, the frequency will be adjusted to phase accuracy. The results of the interaction of the other components in the phase detector will be sufficiently high-frequency, they will not pass through the filter for generation 10

Som interference at the input of the second key. In order to equalize the various delays in passing the signal in two different ways from the key input to the output of the horn device at the output of the drive 7 (Fig. 1), the first delay line 5 is designed.

Next, the control video pulse is delayed in the delay line 45 by time Dt and is fed to the control input of the switch 36. Each of the key 36, 37 closes when a video pulse is applied to its control

Torus 29 will not work. Thus, 15 ВХ ° Д - in the open state, the keys

At the output of the time-frequency shift unit 3, there is a signal in which the component S is in phase and equal to the component S ,, in the reference signal (equality is ensured by a single gain coefficient in the amplitude of the through path). The presence of interference will not affect the trim, since at point 17 and in the reference signal there are 20

have a unit coefficient before

A circuit from control block 40, controlled oscillator 42, mixer 43, narrow band filter 44, amplitude tector 49, threshold block 51, and

the fur components of the mutually non-corre-25 memory element 41,

the result of the comparison of their current phases through the filter 31 also does not pass. The band of filter 31 must be less than fif,

Now consider the operation of the interference suppression unit, FIG. First, consider the noise detection circuit. The input signal is fed to the adjustable amplifier 39, then to the amplitude detector 48. The voltage of the low-pass filter 47 controls the gain of the adjustable amplifier 39, ensuring the average level of the signal at its output is constant. The described ring performs automatic gain control (AGC). Moreover, the LPF parameters are selected in such a way that the AGC monitors relatively slow changes in the signal amplitude (for example, due to fading) and does not work for fast changes in the envelope when a pulse noise hits. Since these types of modulation in the communication line (FM, THU, OFT) imply a constant level of the emitted useful signal, rapid changes in the output signal at the output of the amplitude detector 48 indicate the arrival of a pulse interference. They are allocated using a high pass filter 46, and then using a threshold block 50 of them, a control video pulse is generated that coincides in time with the radio pulse

Som interference at the input of the second key 37. To equalize the various delays in passing the signal along two different chains from the key input to the output of the threshold device at the output of the receiver 7 (Fig. 1), the first delay line 5 is intended.

Next, the control video pulse is delayed in the delay line 45 by time Dt and is fed to the control input of the switch 36. Each of the keys 36, 37 is closed when a video pulse is applied to its control

0

have a single transfer coefficient.

A circuit from control unit 40, controlled oscillator 42, mixer 43, narrowband filter 44, amplitude detector 49, threshold unit 51, and

0

five

0

five

0

five

A narrowband is considered interference, the power of which significantly exceeds the average power of the useful signal in this narrow band. The control unit 40 generates a control voltage that cyclically tunes the frequency fr of the controlled oscillator 42 so that it travels the entire frequency spectrum of the useful signal. In mixer 43, the spectrum of the desired signal is shifted down by the frequency fr. The signal then passes through a narrowband filter 44, an amplitude detector 49 and a threshold unit 51. Thus, the level of the spectral components of the input signal is determined in a narrow band, and this band passes the entire spectrum of the input signal. If somewhere the level of the components in this narrow band rises sharply, the second threshold unit will record this as the presence of narrow band interference.

A signal about this is sent to the memory element 41, to which the control voltage is also constantly supplied from the control unit 40. At the time the signals of the threshold unit 51 arrive, this control voltage will be remembered. It carries information about which region of the spectrum narrowband interference is concentrated.

The control voltage from the memory element is applied to the controlled notch filters 34, 35 and turns them on so that their fp and fp instruction bands coincide with the position of the narrowband interference in the signal passing through them. And fp - fr Af. Outside the notch band, the transmittance of both notch filters is close to one.

If narrowband interference is absent in the entire band of the useful signal, rejection is not performed and their transmission coefficient is one in the entire band.

Consider the process of removing impulse noise.

Let at some point in time the noise in the input signals, UA (points 18 and 19) are absent. Then, at the output of the first subtractor 32 at point 20, the signal is U20 UA9- U. The transfer ratio of the notch filters and keys is equal to one, therefore at the output of the second subtractor

one . A communication line containing an information source and a transmitter with an antenna on the transmitting side, and a receiver with an antenna and a delay line on the receiving side, characterized in that, in order to increase the noise immunity under narrowband and impulse noise conditions,

33 signal is zero. At the same time, on the 25-series-connected in series, the block is, during the course of the block as a whole, the signal is UB (,, Ґ + + U4Q 2i „, where U,

 EXIT is a useful option.

Let the impulse noise (t) appear in the signal U 18 (there is no signal in the signal, since the interference in them is shifted to DO. Then Uio U19 - U18. The first key 36 is closed, therefore U2 U19 18 is left and the signal

thirty

The same-time shift and adder, the output of which is connected to the transmitter input, and the second input of the adder is combined with the output of the information source and the input of the time-frequency shift block, and on the receiving side the first and second compensators, the time-frequency shift block, the interference suppression unit and an amplifier-limiter, the combined signal inputs of the compensators are connected to the output of the delay line, the input of which is connected to the output of the receiver and the first input of the interference suppression unit, the output of which through the amplifier is limiting is connected to the reference input of the first compensator, the output of which is connected to the signal input of the time-frequency shift unit and the reference input of the second compensator, the output of which is connected to the second input of the interference suppression unit and to the reference input of the time-frequency shift unit whose output is connected to 50 is the third input of the interference suppressor, the output of the limiting amplifier is the information output of the communication link.

 U18

+ U19 + U2 2U

nineteen

But

in the signal at this time, only the component U is useful, i.e. Ugb (x 2U0. Likewise, if the interference pulse is at point 19. Then key 2 is closed, V is U2o L8

 and & ЫГ 2 и18 2ис as there is no interference in this moment at this moment, and since the signals and the useful components are equal and in-phase. This removes the impulse noise.

Consider the process of removing narrowband interference. Let it be present in the signal at the frequency Јl, in the signal U - at the frequency f n „, f Af Afn. At the same time, the first notch filter 34 is tuned to the frequency fn, the second 35 - to the frequency fПЈ. Both keys are open. Outside the frequencies f (c, the components of the signals pass (as discussed above) unchanged and are summed in the third adder 38.

Consider the components at the frequency f rm {- U18 P1,. Was 0

five

0

schA U m P | contains interference. In this case, U20 -. Since the signal does not pass through filter 34 at this frequency, then U U is Ui8, ni J U8b, x 2 Una. And in the signal U, q at frequency f, there is no interference. Thus, in the output signal the interference at the frequency ЈP | (rejected, and the useful signal itself is not damaged.

Similarly, it happens at the frequency fn.

Claims (5)

Invention Formula one . A communication line containing an information source and a transmitter with an antenna on the transmitting side, and a receiver with an antenna and a delay line on the receiving side, characterized in that, in order to increase the noise immunity under narrowband and impulse noise conditions, 5 series-connected unit of 25 series-connected unit of thirty 35 0 The same-time shift and adder, the output of which is connected to the transmitter input, and the second input of the adder is combined with the output of the information source and the input of the time-frequency shift block, and on the receiving side the first and second compensators, the time-frequency shift block, the interference suppression unit and an amplifier-limiter, the combined signal inputs of the compensators are connected to the output of the delay line, the input of which is connected to the output of the receiver and the first input of the interference suppression unit, the output of which through the amplifier is limiting is connected to the reference input of the first compensator, the output of which is connected to the signal input of the time-frequency shift unit and the reference input of the second compensator, the output of which is connected to the second input of the interference suppression unit and to the reference input of the time-frequency shift unit whose output is connected to 0 by the third input of the interference suppressor, the output of the limiting amplifier is the information output of the communication link. 2. A communication line according to claim 1, characterized in that the compensators comprise an adder, a first and a second adjustable amplifiers, a first and a second integrator, a first and second multipliers, and a phase shifter five five eleven 90 ° the output of the compensator is the output of the adder, the signal input of the compensator is one input of the adder, and the reference input of the compensator is the combined inputs of the second multiplier and the second adjustable amplifier and the phase rotator input 90 °, the output of which is connected to the inputs of the first multiplier and the first adjustable amplifier, the outputs of the first and the second multipliers, respectively, through the first and second integrators are connected to the other inputs of the first and second adjustable amplifiers, and the outputs of the adjustable amplifiers are connected respectively, with other inputs of the adder, its output is connected to other inputs of the first and second multipliers, 3, Communication line pop-1, characterized in that the block of time-frequency shift of the transmitting sides contains serially connected first and second mixers and a delay line, as well as the first and second heterodyne, and the input of the time-frequency shift block is the input of the first mixer, and the output of the output of the delay line, the outputs of the first and second local oscillators are connected to other inputs of the first and second mixers, respectively. 4. The communication line of claim 2, which is different from the fact that the time-frequency shift unit of the receiving side contains serially connected first mixer, second mixer, delay line, phase detector, low-pass filter and voltage controlled oscillator, connected by the output to the second input of the second mixer, and the local oscillator connected by the output to the second input of the first mixer, the signal and reference inputs of the block are respectively the first input of the first mixer and the second input of the phase detector, and the output of the block is the output of the line delays 5. A communication line according to claim 1, characterized in that the unit is 12 0 five The interference pressure contains the first and second subtractors, the first and second controlled notch filters, the first and second keys, the adder and the adjustable amplifier, the first and second amplitude detectors, the first and second threshold units, the controlled oscillator, the control unit, the narrow band filter, mixer element memory, a high-pass filter, a low-pass filter and a delay line, the first and second inputs of the interference suppression unit being respectively the first and second inputs of the first subtractor and also connected to the first and second inputs of the adder, the output of which is interference suppression, and the third input to the output of the second subtractor, the output of the first subtractor is connected to the signal inputs of the first and second controlled notch filters, their outputs to the signal inputs of the first and second keys, and the outputs of the first and second keys, respectively, to the first and second inputs of the second subtractor, the third input of the interference suppression unit is input 0 of the Adjustable amplifier, the output of which is connected to the inputs of the first amplitude detector and mixer, the output of the first amplitude detector is connected to another input of the adjustable amplifier, and through a series-connected high-pass filter and the first threshold unit to the input of the delay line, the output and input of the delay line are connected to the control inputs of the first and second keys, the output of the control unit is connected to the input of the memory element and through a controlled generator to another input of the mixer, its output through the series-connected narrowband filter, the second amplitude detector and the second threshold unit connected to another input of the memory element, the outputs of the memory element are connected to the control inputs of the first and second controlled notch filters. five 0 five 0 D-4 1 YuigZ QJU2.4. 5