SU39224A1 - The method of obtaining amplitude modulation by adding in the antenna phase-modulated oscillations - Google Patents

Description

At present, there are two well-known methods for modulating radiotelephone transmitters: amplitude and phase modulation. With amplitude modulation, reception is possible at any receiver, but its disadvantage is the low efficiency (powerful stage) of the transmitter, which, with more than 1 power, becomes significant. The current in the antenna with amplitude modulation varies according to the law:

i / (l - (- / fe sin Qt) sin m

With phase modulation, it is possible to obtain a high transmitter efficiency, but special receiving devices are required for reception. The current in the antenna during phase modulation varies according to the law:

g / sin 9 (1 + sin Qt)

In order to use the positive qualities of these methods and eliminate the drawbacks of each of them separately, another method was proposed, according to which amplitude modulation is carried out by adding phase-modulated oscillations in the antenna.

The present invention relates to this latter method of obtaining amplitude modulation and consists in using a goniometer, in which

in the fixed coils they are shifted in phase by 90 ° between themselves and one or both currents are modulated in amplitude.

In FIG. 1 and 2 are schematic diagrams of an apparatus for carrying out the inventive method.

Two oscillators, of which each is modulated in phase, are associated with a common oscillating system so that in this common system amplitude modulation is obtained, thereby making it possible to receive to a conventional receiver.

Phase modulation can be performed using the device shown schematically in FIG. one; In this device, phase modulation is obtained by changing the current in one of the windings of the goniometer or by changing the currents in the two windings of the goniometer shifted 90 degrees apart in phase so that the voltage vector in the third winding of the goniometer will modulate in phase with the modulating frequency, with the vector itself remaining almost unchanged in amplitude.

Both generators, since they are phase modulated, have a high efficiency; when such generators are connected to one common oscillatory system (for example, to a circuit connected to the antenna, or to the antenna itself), their voltage is added and, as a result,

normal amplitude modulation is obtained.

Mathematically, the addition of voltages in the antenna can be represented as follows- If the current of one generator

ij / sin o) - | - ". (1- | - sin Q) and the current of the second generator

c. 1 sin cui - f (1 - {- sin Q), then the current in the antenna rd /, j- / 2 / sin f (1 - | - sin Qt) sin wt.

If (f (1 4) is small, TO sin is replaced by the argument, and then

if, (1 + sin sQ sin.

Although there is only or mainly phase modulation in each generator, in a general oscillating circuit or antenna, the current varies according to the law of amplitude modulation.

Along with phase modulation, each component of the current can be modulated in amplitude in one way or another. Adding amplitude modulation to the phase allows the degree of linearity of amplitude modulation obtained at the antenna to be affected.

The present invention differs from the known defasage scheme in that this scheme applies the addition of two voltage vectors in quadrature, of which one vector is modulated, which is difficult to accomplish, since a number of complicated measures are required to obtain strict circuit identity during modulation.

In general, the circuit diagram of the device according to the present invention is shown in FIG. 2. Here, the driving oscillator 7 excites the lamp oscillator 2, in the anode circuit of which there are two coupled oscillatory circuits 3 and 4. From these two circuits, the currents of which are shifted between themselves in phase by 90 °, high-frequency power is supplied by means of coils zi 5 and b on the fixed frames of two goniometers connected to each other, as shown in the drawing.

Two modulator lamps 9 and 10 are connected in series with the coders of the goniometers. The voltage of the modulating (sonic) frequency from the transformer with a midpoint on the secondary winding is applied to the grids of these lamps. The primary winding of this transformer is powered by a low frequency amplifier. Variable capacitance capacitors 72 and 75 serve to add the contours of the goniometers to the working wave. About the internal moving coils of the goniometers are powered by amplifiers of modulated high-frequency currents 14 and 75 of two circuits, terminating with powerful amplifiers 76 and 77.

The anode circuits 75 and 19 of these high-power amplifiers are associated with an intermediate oscillatory circuit 20, which, in turn, is associated with the antenna circuit 27.

The subject matter of the invention.

Claims (3)

1. A method of obtaining amplitude modulation by adding in the antenna phase-modulated oscillations, characterized by the use of a goniometer, in which the currents in the stationary coils are shifted between themselves in phase by 90 ° and one or both currents are modulated in amplitude (Fig. 1). 2. A method according to claim 1, characterized by the use of two goniometers connected in parallel or in series (Fig. 2). 3. Method according to paragraphs. 1 and 2, differing in application for amplitude modulation, in the presence of a phase goniometer with an elliptical field (for which, for example, the angle between the fixed coils of the goniometer is chosen to be unequal 90 °). to the author's testimony of A. L. and 3. I. Model No. Mints, G. A. Zeytlenok 39224 FI