SU1631699A1 - Single-sideband signal demodulator - Google Patents

Abstract

The invention relates to radio engineering and can be used in receiving devices. The purpose of the invention is to improve the accuracy of demodulation with instability of the carrier frequency. Single-band signal demodulator contains amplitude detector 1, amplitude limiter 2, frequency detector 3, high-pass filter 4, integrator 5, phase modulator 6, reference signal generator 7, single-band signal generation unit 8, multiplier 9, low-pass filter 10 . The single band signal, synthesized at the output of block 8, coincides with the input signal with an accuracy of a constant multiplier, but the frequency of the reference oscillation coincides with the frequency of the synthesized single band signal, which makes it possible to assert a high demodulation accuracy. The demodulator according to claim 2 of the formula is characterized by the implementation of block 8 consisting of amplitude modulators 11 and 12, inverter 13 and block 14 of subtraction. 1 hp ff, 1 ill. (L% in s

Description

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The invention relates to radio engineering and can be used in receiving devices.

The purpose of the invention is to improve the accuracy of demodulation with instability of the carrier frequency.

The drawing shows a structural electrical circuit of the demodulator of single-band signals.

The single-band demodulator contains an amplitude detector 1, an amplitude limiter 2, a frequency detector 3, a high-pass filter 4, an integrator 5, a phase modulator 6, a reference signal generator 7, a single-band signal generating unit 8, a multiplier 9 and a low-pass filter 10.

The single-band signal generating unit 8 comprises first and second amplitude modulators 11 and 12, an inverter 13 and a subtraction unit 14.

Single-band demodulator operates as follows.

The inputs of the limiter 2 and the amplitude detector 1 receives a single-band signal of the form:

Uc (t) KV (t) + Aft (t) t + (t) I,

(one)

where V (m.) and p (m.) are the instantaneous amplitude and phase of the signal;

c) - nominal circular frequency of the signal;

Aa (t) is a variable component of the circular frequency, due to the instability of the reference frequencies used in the formation and transformation of a single sideband signal;

K is a constant coefficient. After amplitude limiting in limiter 2, expression (1) has eid:

(2)

U2 (t) UlKcos + Aft (t) t 4-g9 (t) I

At the output of the frequency detector 3, the voltage is proportional to the variable component of the instantaneous frequency of the signal (2)

U id (t) +) 3, (3)

where Ki is the slope of the discriminatory characteristic.

The change in the frequency of the signal (1) due to the instability of the reference frequencies is a slow process compared to p (t). Therefore, the component of the signal corresponding to the first term in the expression (3) is suppressed by filter 4

After the integrator 5 integrates these frequencies, a voltage proportional to 1) ID is applied to the input of the phase modulator.

The signal at the output of the phase modulator 5 b has the form:

ifm (t) U2 cos wo t + p (t), (4) where is the circular frequency of the generator 7 of the reference signal.

A modulating signal V (t) from the output of the amplitude detector 1 is fed to the second input of the 8-generation unit 10 of a single-band signal or to the second input of the first amplitude modulator 11. The second input of the second amplitude modulator 12 receives the modulating signal V (t) through inverter 13. The output signals of the first and second amplitude modulators 11 and 12 are of the form:

Un (t) Umli 1 + mV (t) cos ftJOt + p (t);

20 (5)

Ul2 (t) Um12 1 -mV (t) (t),

(6)

where m is the amplitude modulation factor.

25 At the output of the subtraction unit 14, and, therefore, at the output of the single-band signal synthesis unit 8, a signal of the form: j, Ucnc 2m V (t) cos uot + p (t) is formed. (7).

30This signal is accurate to constant

the multiplier coincides with the input signal, but at the same time the frequency of the reference oscillation with high accuracy coincides with the frequency of the synthesized single-band signal,

35 which allows for improved demodulation accuracy.

Claims (2)

Invention Formula 40 1. A single-band demodulator containing a series-connected multiplier and a low-pass filter whose output is an output of a single-band demodulator and a reference signal generator whose output is connected to the first multiplier input, characterized in that the demodule when the carrier frequency is unstable, 50 consequently connected amplitude limiter, frequency detector, high-pass filter, integrator, phase modulator are introduced, to the second input of which under the output of the reference signal generator is turned on, and the block 55 forming a single sideband signal, the output of which is connected to the second input of the multiplier, and an amplitude detector, whose input is connected to the input of the amplitude limiter and is the input of demo A single-sided pulley signal and the output is connected to the second input of the single-sided signal generation unit. 2. The demodulator of claim 1, wherein the single-band signal generating unit comprises first and second amplitude modulators, the first inputs of which are the first input of the single-side signal generation unit, the inverter, whose input is connected to the second input of the first amplitude module the torus is the second input of the single-band signal shaping unit, and the subtraction unit, the first and second inputs of which are connected respectively to the outputs of the first and second amplitude modulators, and the input is the output of the shaping unit and a single-sideband signal,