SU77478A3 - Device for frequency modulation - Google Patents

Description

A device for frequency modulating oscillations received from a quartz-stabilized oscillator is known.

In the device described, high stability sinusoidal oscillations received from a quartz stabilized generator are converted into sawtooth oscillations and, together with modulating oscillations, are applied to the grid value of a mixing lamp, causing current in the anode value of a pulse of variable duration varying with changes in amplitude of modulating voltage. These pulses are then subjected to amplitude limitation and differentiation, in which case the pulses in the form of positive PIR are applied to an oscillatory circuit, which produces oscillations with a variable frequency.

FIG. 1 is a diagram of one embodiment of the device according to the invention; FIG. 2, 3, 4 and 5 are graphical illustrations of oscillatory processes, in the device of FIG. one; in fig. 6 shows a simplified diagram of the modification of the proposed device.

The Vi crystal oscillator gives a sinusoidal current of a certain frequency. This current is fed to the input of the lamp V-2, on the grid of which a bias voltage appears due to the grid current flowing through RI. The operating mode of the Wo lamp is chosen so that the applied voltage acts within 60 °. These current pulses discharge the capacitor C, continuously charged through the resistance R and. Thus, at the output of the lamp, the Vo current has a sawtooth shape shown in FIG. 2

The sawtooth oscillations are supplied to the lamp V, and the modulating oscillations to the lamp. The input circuit of this lamp is connected in series with the resistance R and parallel to the capacitor Cg. The values of Ri and C2 are chosen so that the input to the 1/4 lamp is inversely proportional to the frequency. Such a relationship is necessary to convert phase to frequency modulation.

№ 77478

The total voltage is applied to the grid circuit of the ultrasonic modulator lamp, to which such an offset is given, so that its characteristic has the form of a modulated sawtooth wave, shown in FIG. 3. In FIG. Figure 3 shows the form of the oscillations at the output of this lamp, having different amplitudes and durations, depending on the magnitude of the modulating voltage. The sawtooth oscillations of various amplitudes and durations then enter the lamp V, which cuts off the peaks and turns these pulses into pulses of constant amplitude shown in FIG. 4. where it can be seen that the increase in the square-shaped current occurs at regular intervals, and the fall-off at various time intervals, with the intervals changing according to the law of change of the modulating voltage. The pulses are then supplied to the lamp V through a Cs-R-a differentiating capacitive-ohmic circuit, in which they take the form shown in FIG. 5, where it can be seen that negative pulses are not only equal in amplitude, but also separated by equal intervals and, thus, correspond to the rise times of a rectangular current, while its decay times correspond to positive pulses that are identical in amplitude but separated by different intervals. Since the lamp V responds only to positive pulses, the negative parts of the pulses do not act on it, and their positive parts through the lamp VT act on the lamp Vs. The pulses applied to the lamp V excite the L, C circuit, which is tuned to either the fundamental frequency of the crystal oscillator or to one of the harmonics.

Thus, in the described device, the arrangement of the positive pulses in the output circuit of the lamp Vj varies in accordance with sound modulation. It is possible to change the position of the pulses within the pre-ZOO period of the modulated oscillation. The tuned L, € 4 circuit filters out unwanted oscillations and a variable voltage is generated on it, the frequency of which varies according to the modulation. In the absence of modulation, the oscillating circuit operates at a medium frequency or its harmonic. By multiplying the frequency, it is possible to arbitrarily increase the phase shift, which reaches the loop L, Sc by up to 300 °.

In the device of FIG. 1 each lamp performs its particular function. It is possible to make one lamp perform two or more different functions, such as in the device shown in FIG. 6, where the Vg crystal oscillator and the VY sawtooth generator each perform one function, and the Vu and Via lamps act as limiters for the amplitude of the positive and negative pulses of both the sawtooth and modulation currents. The termination lamp Vj corresponds to the lamp in FIG. 1. In this way, the UV and Vf2 lamps function as U- lamps,

E4 V5 UVI U7FIG. one.

Subject invention

A device for frequency modulation with quartz stabilization, characterized in that the sawtooth pulses obtained by converting the voltage of the crystal oscillator and the modulating signals are connected to mixing lamps, the voltages from which are converted by a limiter into rectangular pulses of the same height but of different duration , summed up to a tuned circuit that produces oscillations with variable frequency.

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