SU1270865A1 - Generator of amplitude-modulated signals - Google Patents

Abstract

The invention relates to radio engineering. The purpose of the invention is to reduce the nonlinear distortion of the envelope of the output signal while reducing its parasitic phase modulation. The device contains a source of 1 modulated signals, y 2 with an adjustable coefficient. amplification, output y-3, synchronous detector 4, differential y-5, y-6 error signal, modulation source 7, amplitude modulator 8, Frequency converter 9 again, multiplier 10, source 11 RF signals. 1 il. yu | about 00 f sod

Description

The invention relates to radio engineering and can use dp to form amplitude modulated signals in radio engineering devices for various purposes.

The purpose of the invention is reduced: non-linear distortion of the envelope of the output signal while reducing its parasitic phase modulation.

The drawing shows a structural electrical circuit of the proposed driver.

Amplitude modulated signal generator contains a source of 1 modulated signals, an amplifier 2 with adjustable gain, an output amplifier 3, a synchronous detector 4, a differential amplifier 5, an error signal amplifier 6, a source 7 of modular signals, an amplitude modulator 8, a frequency converter 9, a multiplier 10, the source 11 of the high frequency signals.

The shaper of the amplitude-modulated signals works as follows.

The multiplier 10 multiplies the signals of the source 1 of the modulated signals Uj E, sin (. |) And the source 11 of the high frequency signals and, (O2t + 452) 3 resulting in the generation of the heterodyne signal for the frequency converter 9

and, {cos (с02-Ц) г + Чг-Ф, -COS (k) 2 + U3 tt42 + 4}.

The other input of the frequency converter 9 receives an amplitude-modulated signal from the output of the amplitude modulator 8 via the amplifier 2 with an adjustable coefficient, which is generated using the source 7 of modulating signals and the source 11 of the high-frequency signals. the signal looks like

(l + mRin; t) + (t) E (t)) + 4 (t),

where the term (t) - indicates the parasitic phase modulation that occurs in the amplitude modulator 8 and the amplifier 2.

In frequency converter 9, which is a multiplier with a filter, the signals Uj and Uv are multiplied and the signal U is extracted with a frequency Ox, having the form

, E, E, E (t)

liii llsin,) +

and

, -ip (t) j

Ji 5i lcos45 (t) sin (co, t + 4,).

From this expression it is evident that in

The output AM signal of frequency converter 9 is free of spurious phase-to-phase modulation, but additional non-linear envelope distortions appear, which, together with non-linear distortions arising in

Amplitude modulator, 8, compensation. This is controlled by negative feedback on the envelope generated by the synchronous detector 4, differential amplifier 5, amplifier 6, and variable gain amplifier 2. Compensation for the nonlinear distortion of the envelope is as follows.

If we assume that the synchronous detector 4 does not introduce nonlinear distortions into the envelope, then the voltage at its output is directly proportional to

the output envelope of the shaper of an amplitude modulated signal, B diff (}: Real Oscillator 5, the output voltage of the synchronous detector 4 is compared with the voltage of the modulating signal of source 7 and the error signal determined by the nonlinear distortion of the shaper of the output shaper of the amplitude modulated

signals, through the amplifier 6, the error signal with the opposite sign is fed to the control input of amplifier 2, in

which, due to a change in the gain factor, an additional amplitude modulation of the signal from the output of the amplitude modulator 8 is performed using the error signal voltage with the opposite sign, i.e. compensation of the nonlinear distortion of the envelope of the AM output signal.

However, the synchronous detector 4 also introduces non-linear distortions into the AM envelope of the signal, which in the axis is determined by the parasitic phase error.

Claims (1)

modulating the AM signal, preventing the AM signal from in-phase with the carrier signal. The non-linear distortion of the synchronous detector 3 pa 4 is not compensated and appears in the envelope of the output AM signal. But as the parasitic phase modulation of the AM signal, which enters the input of the synchronous detector 4, is reduced, the non-linear distortions introduced into the envelope of the synchronous detector 4 are also reduced. An inventive Shaper of amplitude modulated signals containing a sequentially connected source of modulating signals, a differential amplifier, an error signal amplifier and an amplifier with adjustable gain, and an amplitude modulator whose input signal of the modulating signal is connected to the second output of the source of modulating signals, and the output is from the control input of the amplifier with an adjustable gain factor, subsequently connected to the output amplifier and a synchronous detector 54 sec. whose input is connected to the first output of the modulated signal source, and the output to the second input of the differential amplifier, which is designed to reduce the non-linear 1x envelope distortion of the output signal while reducing its parasitic phase modulation, connected in series source of high frequency signals, a multiplier, the second input of which is connected to the second output of the source of modulated signals, and a frequency converter whose input is connected to the output of the amplifier with an adjustable coefficient is the gain, and the output - to the input of the output amplifier, said second output high frequency signal source connected to the input modulated signal is an amplitude modulator.