SU427450A1 - POWERFUL AMPLIFIER - Google Patents

Description

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The invention relates to radio transmission technology and can be used in radio transmitters or high-power amplifiers of amplitude-modulated (AM) radio frequency oscillations.

Power amplifiers of amplitude-modulated oscillations are known, containing a class B amplifier and a load.

The disadvantage of the known devices is low efficiency, as well as the redundancy of the nominal power of the amplifying device.

In addition, the linearity of the gain significantly depends on the shape of the static anodon-grid characteristics of the amplifying device in the lower part.

The purpose of the invention is to improve the power amplifier of amplitude-modulated oscillations of class B by significantly reducing the nominal power of the amplifying device, increasing its efficiency and eliminating the dependence of the linearity of the gain on the shape of the static anode-grid characteristics.

This is achieved by the fact that in the proposed power amplifier at its input, as well as between the outputs of the class B amplifier and the load, respectively, two phase-shifting circuits are connected with a signal phase shift for one of its sidebands by 180 °.

FIG. il presents the block diagram of the proposed powerful amplifier. Here between the low-power source of AM oscillations (exciter) 1 and the input of the amplifier 2 class "B

phase circuit 3 is turned on, and between the output of amplifier 2 and its load resistance 4 is phase circuit 5; in fig. 2 shows the phase-frequency characteristic of the phase circuit 3 (f (s)), the phase-frequency characteristic

phase circuit 5 (Φ (5)) and the total phase-frequency characteristic of both phase circuits (φ (3) + (f (5)). The solid lines show idealized phase characteristics, the dotted line shows the characteristics of real circuits.

It gives the location of the carrier frequency fn and the sidebands AM oscillations with modulation frequencies between F and FB. We assume that phase circuits 3 and 5 do not introduce amplitude-frequency distortions. One of these circuits provides 180 sideband, the other sideband along with the carrier.

Directly from FIG. 2 it follows that the inclusion of an amplifier circuit in the circuit, and 5 does not lead to signal distortion in the load of the 4 amplifier, since these circuits in total create only a rotation of the oscillations of the carrier frequency by 180 °.

From the consideration of the vector diagrams of FIG. 3 it is clear that the amplitude-modulated oscillations at the input of the amplifier are oscillating with quadrature modulation. As a result, with 100% modulation, the peak value of the signal is reduced by a factor of two, and, consequently, the power for which the amplifying device is to be calculated is reduced by half.

In terms of energy, the proposed amplifier is close to a class B generator with anodic modulation, but does not require a high-power anode modulator and increased electrical strength of the device.

Finally, from the diagram of FIG. 3 b it follows that with quadrature modulation, the current of the electron tube (transistor) pulsates from (0.7 H-il) b, ax, where 1. max is the current value in pink mode and for undistorted amplification the shape of grid-grid characteristic in its part does not matter.

It should be noted that the phase circuit 2 at the input of the amplifier is not presented hard

requirements regarding the phase rotation of the side frequencies by 180 °. If this phase rotation is 180 ° ± f, then the gain in peak power of the amplifying device is reduced

in 1 I g.-n o /. At the same time, if the total1 1 Ы П Y / о

on the phase characteristic of circuits 2 to 4 remains symmetric, signal distortion occurs.

Subject invention

A powerful amplifier of amplitude-modulated oscillations, containing a class B amplifier and a load, characterized in that, in order to reduce the nominal power of the amplifying device, increase the efficiency and improve the linearity of the amplifier, as well as between the output of the class S amplifier and the load includes, respectively, two phase-shifting circuits with a phase shift of the signal for one of its sidebands by 180 °.

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