RU1811023C - Demodulator of minimum frequency-shift keyed signal - Google Patents

Abstract

The inventive demodulator contains three phase shifters 1, 4, 17, six multipliers 2, 3. 6, 7, 13, 16, one inverter 5, two generators 8.14, two adders 9. 10, one phase detector 11, one frequency multiplier 12, one synchronization block 13, one decision block 8. 6-9-15-18, 3-5-10-16-18, -2-9, 1-7-10. 13-12-11-8-4-2, 4-3, 8-6, 8-11, 8-7. 13-12, 9-13-14-15.14-17-18-18.17-13, 17-16.14-13.14I8. 1 ill.

Description

The invention relates to radio engineering.

The purpose of the invention is to improve noise immunity.

The drawing shows a structural electric scheme of the proposed demodulator.

The demodulator contains a third phase shifter 1, a first, second multipliers 2, 3, a first phase shifter 4, an inverter 5, a third, fourth multipliers b, 7, a first generator 8, a first, second adders 9, 10, a phase detector 11, a multiplier 12 frequency block 13 synchronization second 14 generator, fifth, sixth multipliers 15, 16, the second phase shifter 17, the decision block 18.

The demodulator operates as follows.

The input signal x (t). At the output of the phase shifter 1, we obtain the signal x (t) described by the expression

In the synchronization unit 13, the signals b (t) and a (t) are squared

") 4W & -" 6. g.

 .

takkaki12 1 ,.

As a result of this operation, the manipulation is removed from the signals b (t) na (t) and the phase jumps on p disappear. In the synchronization block 13, the signals c (t) and

s (t)

yi (tbc (t) S (t)

2.That

twenty

99

and signal a (t) is subtracted from signal b (t):

y2 (t) b2 (t) -a2 (t) | cos- .to

) Ui cos sin ftfc. t-U2 cos ub t. 25

Jl to

The generator 8 generates an oscillation c (t) -: cos ft) b (t) and at the output of the phase shifter 4 we have an oscillation

S (t) sln (Wot. 30

The timing of the first generator 8 will be explained below.

As a result, at the output of adder 9 we get a signal

b (t) x (t) COS ftfet + xfrjsln (COS

4. to

and at the output of adder 10 we get a signal

a (t) x (t) sin MO t-x (t) cos (DO) 2 sin

Jtt

2 TO

The minus sign in the expression a (t) is due to the presence of an inverter 5. -Further, these signals b (t) and a (t) are supplied to the first inputs of the multipliers 15, 16, respectively, and the oscillations c (t) and S ( t) -c the output of the generator 14 and the phase shifter 17, respectively. The timing of the generator 14 will be explained below.

As a result, at the outputs of the multipliers 15 and 16, the signals xi (t) and X2 (t) are generated, respectively.

The operation of synchronization devices of 8.14 generators in the inventive device will be shown.

As a result of multiplying the signals yi (t) and y2 (t), we obtain the signal for controlling the frequency of the generator 14

y (t) yi (t) y2 (t) -Uln- -. . h & o

proportional to the sine of the phase difference between the signals c (t) and b (t). As a result, the generator is phase locked to the oscillations b (t) and a (t).

To synchronize the generator 8, an oscillation frequency multiplier 12 is used for i (t) and y2 (t).

Works — this multiplier is as follows.

In it several times the operations are carried out:

1st operation - squaring yi (t) and y2 (t); . 2nd operation - multiplying yi (t) by

V2 (t); 22 3- operation - subtracting Y2 (t) -yi (t.). As a result of these operations, we obtain

two quadrature oscillations with doubled

frequency

...:.

"(") -I-.

These operations are repeated so many times until we obtain the oscillation frequency at the output of the multiplier equal to the frequency fo of generator 4.

If the ratio

TQ To

not equal to 2 then in

the multiplier uses a different sequence of operations as explained by the following trigonometric formula

cosm "cosnaa-sinni aslnn2tf cos (ni + n2) or.

As a result, these are always out of oscillation with frequency

half-operations can

J

Then

learn oscillation with frequency n / r0, where n is an integer.

The oscillation with a frequency fo from the output of the frequency multiplier 12 goes to one input of the phase detector 11, the second input of which receives the oscillation from the output of the generator 8. As a result, the control voltage appears at the output of the phase detector 11, which synchronizes the generator 8. Synchronization of this generator more stable and does not break at Doppler frequency shifts, since this shift does not affect low-frequency oscillations

TTt ,,, П

UICQS

and uasin

2 m0 2r0 — The proprietary generator stably operates in channels with a Doppler frequency shift. This allows the use of an inventive device for communicating with moving objects;

Formula and Demodulator of a signal of minimal frequency manipulation, containing the first multiplier, the second and third multipliers, the first inputs of the latter are connected and are the input of the demodulator, the fourth multiplier, the first generator the output of which is connected to the first inputs of the first phase shifter and phase detector, the output of which is connected to

the input of the first generator, the second generator, the output of which is connected to the first input of the decisive unit and through the second phase shifter with the second input of the decisive 5th unit, characterized in that, in order to increase noise immunity, a third phase shifter, inverter, first and second adders, multiplier are introduced frequency synchronization unit, the fifth and sixth multipliers, the input of the third phase shifter being the input of the demodulator, and the output connected to the first inputs of the first and fourth multipliers, the outputs of which are connected respectively but with

15 by the first inputs of the first and second adders, the output of the first phase shifter is connected to the second inputs of the first and second multipliers, the output of the latter through an inverter is connected to the second input of the second 20 adder, the output of which is connected to the first inputs of the synchronization unit and the sixth multiplier, the output of which is connected to the third the input of the decision block, the fourth input of which is connected to the output of the house of the fifth multiplier, the first input of which and the second input of the synchronization block are connected to the output of the first adder, the second input is cerned connected to the output of the third multiplier, a second input koto30 cerned and a second input of the fourth multiplier soedineny.s output of the first generator, the second input of the phase detector is connected to the output of frequency multiplier, the first and second inputs of which

35 are connected respectively to the first and second outputs of the synchronization unit, tre. the second output of which is connected to the input of the second generator, the output of which is connected to the third input of the synchronization unit

40 and the second input of the fifth remnant, the output of the second phase shifter is connected to the fourth input of the synchronization unit and the second input of the sixth multiplier.