SU1356247A1 - Device for receiving signals with amplitude-phase-shift keying - Google Patents

Abstract

The invention relates to telecommunications and m. used in multi-channel data transmission devices for receiving signals with amplitude-phase shift manipulation with a change in the average level of the input signal. The aim of the invention is to improve noise immunity when the average level of the input signal changes. The device contains a phase demodulator 1, an amplitude comparator 6, and the phase demodulator 1 contains a decisive unit 7, a synchronization unit 8 and synchronous detectors 9. Series-connected switch 2, a controlled attenuator 3, a DC amplifier 4 and a low-pass filter 5 are introduced The device according to claim 1 is characterized in that the outputs of the synchronous detectors 9 are connected to the inputs of the decision block 7, the control outputs of which are connected to the control inputs of the synchronization block 8, the outputs of which are connected to the first inputs of the synchronous s detectors 9, 1 ZP f-ly, 1 ill. i (L cond C5 S 4;

Description

one

The invention relates to telecommunications and can be used in multi-channel data transmission devices for receiving signals with amplitude-phase shift manipulation with a change in the average level of the input signal.

The aim of the invention is to improve noise immunity when the average input level changes.

The drawing shows the structural-electrical circuit of the device.

The device contains a phase demodulator 1, a polarity switch 2, a controlled attenuator 3, a DC amplifier A, a low-pass filter 5 and an amplitude comparator 6, the phase demodulator 1 including a resolver unit 7, a synchronization unit 8 and synchronous detectors 9 .

The device works as follows.

The input signal of the device passes through the synchronization unit 8, where it is released from a single informational phase manipulation.

Synchronous detectors 9 detect the amplitude and phase of the input signal of the device. The outputs of the decision block 7 generate estimates of the binary signals transmitted respectively by the subchannels of phase telegraphy. The synchronization unit 8 with the help of control signals from the decision block 7 generates reference oscillations for the synchronous detectors 9.

Further analysis is carried out for the case of two subchannels of phase telegraphy.

The signal arriving at the input of the device (excluding noise and other additive interference) is:

Sjt) (t),), t-4 fS (t)) +

 %

, (t)

- a sequence of binary symbols transmitted over an amplitude-manipulated subchannel;

(t) A (t) {s, (t) + (t) I l (instantaneous amplitude

input signal. Here, A p (t) is the fluctuation amplitude of the input signal;

7

S, (t) S (t)

t is the ratio of the amplitude of unpolarized parcels during amplitude manipulation, О Е d;

ABOUT

J .- sequences

binary symbols transmitted by phase-shifted subchannels.

vK (t), S (. (t.),. (t) + R, (t) ® l / 2, 1

® S (t)

;

- phase manipulation function. Here ® is the modulo 2 summation operation.

The synchronization unit 8 generates the reference oscillations supplied to the first inputs of the synchronous detectors 9. Let the reference oscillation be fed to the first input synchronously from the detector 9 of the first subchannel of the phase demodulator 1 from the synchronization unit 8

Won / t) U, cos u; t-3T / 44-i / J.

If the synchronous detector 9 contains a series-connected multiplier and a low-pass filter, then

U (t),) cos if),

-

thirty

S ,, / t) ,,, (t) l5r2S Jt) - J

where, (t)

- output voltage

synchronous detector 9; K - transfer coefficient

synchronous detector 9. It follows from the above expression that Uci) (t) depends only on the signals transmitted on the first phase-controlled subchannel and the amplitude-manipulated subchannel, and does not depend on the signal transmitted on the second phase-manipulated subchannel. Similarly, it can be shown that the voltage at the output of the synchronous detector 9 of the second subchannel of the phase demodulator does not depend on the signal transmitted via the first phase-shifted subchannel.

TO

We introduce the notation to

and"

 M, w ,,

In this case

UcD (t) (t) - 2SK (t), (t) x (t) + iri-S (t)) - l.

Since the threshold unit included in. the composition of the resolver unit 7, responds only to the sign of the signal Ucii -)

sent to its input, then at the first output of the decision block 7 we have the estimate Sj (t) of the signal S ((t) transmitted via the first phase-shift keyed subchannel. With a sufficiently large signal-to-noise ratio at the input of the device, we can assume that Sj (t) Sc ,, (t).

The polarity switch 2 performs the operation

U, (t) U, g, (t) 2S ,, (t) -l,

where U | (t) is the output voltage of the switch 2 polarity; the voltage applied to the signal input of the commutator 2 polarity; logical signal supplied to the control input of the switch 2 is completely, In the considered device

U, B, (t) HUjt), S ,, (t)), S (t)

UK8. (T)

S.npCt)

. „P (t) S (t),

. Consequently,

Uk (t) K Ajt) S (t) + l-S (t) U. 2S (t).

Since R ((t) coins only

two values (O or 1), then 2S,. (t) -.

In this way,

U, (t) K A, (t) {S (t) + (t) J

 GK Ao (t) with lK Ao (t) g with

Amplitude comparator 6 distinguishes between cases B (t) l and Sfl (t) 0, i.e. forms an estimate of the S (t) signal, S (t

Suppose that the input voltage of the amplitude comparator 6 is a corona voltage P,, Required to ensure the greatest noise immunity of the amplitude-manipulated subchannel. In this case, at a sufficiently large signal-to-noise ratio at the device input, we can assume that S (t) S / t).

Note that for any criterion of optimality and a sufficiently large signal-to-noise ratio at the device input linearly depends on the amplitude of the carrier of the input signal A, (t).

 Thus, U (t) aA Ct), where a is a coefficient depending on the selected criterion of optimality

at p-

The controlled attenuator 3 performs the operation

u ,, / t) ijy, 8x (t) fs; np (t) K, + i-s ;; p (t) 3K

 (t) K, with (t) l Ks) K

where i; (t) 10

15

about

 .

20

25

thirty

40

45

50

at (t) o,

and

VA BV

 Vnp

(t) voltage at the output of the equalizer 3;

the voltage supplied to the first input of the controlled attenuator 3; logic signal supplied to the second input of the controlled attenuator 3.

In the considered device, Judas () to (0, S; p (t); s; (t), S (t) S (t). Consequently, U (t) - K Ao (t) S / t) + tri -S, (t)} - fS (t) K, + + 1-8Иь) CL KA «(t) fsUt) K. -S, (t).

Choose K, I, V-. Since S, (t) can take only two values (O or 1), then S (t) K, + -S (t).

Thus, Uy, (t) (t).

Select the low-pass filter 5 gain ratio equal to a / K t, and the low-pass filter 5 passband is no longer the width of the fluctuation spectrum of the carrier amplitude of the input signal of the device. In this case

35 U (t) U, / t) K ,, aA, (t) U, op ,,

where and. - voltage at the output of the low pass filter 5. Therefore, at the first input of the amplitude comparator 6, connected to the output of the low-pass filter, there is a threshold voltage and, -, required to ensure the greatest noise immunity of the amplitude-manipulated subchannel. Since the low pass filter band 5 is not related to the information transfer rate, the device allows information to be transmitted with fast fluctuations of amplitude non-transmitting (fading).

Claims (2)

1. A device for receiving signals with amplitude-phase manipulation, containing a phase demodulator and amplitude comparator, the output of which is an output amplitude-manipulator of the device’s subchannel, the input and outputs of the phase-shifted subchannels of which are respectively the input and information outputs of the phase demodulator, which are connected in order to increase the noise immunity when the average level of the input signal is changed, controlled by an attenuator, a DC amplifier and a low-pass filter whose output is connected to the first input of the amplitude comparator j the second input and the output of which are connected respectively with the output of the polarity switch and the second input of the controlled attenuator, the auxiliary output and one of the information outputs of the basic demodulator are connected respectively to the signal Editor M. Bandura Compiled by O. Andrushko Tehred M. Khodanych Order 5814/56 Circulation 636 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 6 And control inputs commutator0 five 0 torus polarity. 2. The device according to claim 1, 1 is that the phase demodulator contains a decision unit, a synchronization unit and synchronous detectors, the outputs of which are connected to the inputs of the decision unit, the control outputs of which are connected to the control inputs of the unit synchronization, the outputs of which are connected to the first inputs of synchronous detectors, the second inputs of which, as well as the signal input of the synchronization unit, are the input of the phase demodulator, the information outputs of which are the outputs of the decision unit, and the output of the corresponding synchronization detector is an additional output of the phase demodulator. Proofreader L. Pilipenko