DE809565C - Device for generating vibrations modulated in frequency or phase by sound vibrations - Google Patents

Description

The present JlrJiaduBg ^ E refers to a Device for generating frequency or phase modulated by sound vibrations Vibrations, especially for use in the form of news transmitters. In such The constancy of the carrier frequency must be transmitted in particular be good, whereby the frequency deviation may be relatively small, since that of the to be transmitted Message claimed frequency range

ίο is relatively small.

In a known circuit, the phase modulation is achieved in that a z. B-. Carrier oscillation of constant frequency generated by a crystal-controlled oscillator a phase-shifting network, the phase shift from a modulating Size, e.g. B. on a modulating current dependent which changes the self-induction of coils inserted in the network, and on it the phase deviation is greatly increased by means of a frequency multiplier.

The phase rotation is accomplished according to the invention by entering the phase-rotating network Reactances are inserted, which are changed mechanically by the sound vibrations.

However, it is known per se, through sound vibrations to insert changed reactance «} into the tuning circuit of a generator of frequency-modulated oscillations; the downside of one such a generator, however, is that the mean frequency is not constant.

In particular, capacitors can be used as variable reactances; these mutable Capacitors can easily be combined into a single condenser microphone by placing one of the electrodes on a such microphone is divided into a number of mutually isolated sectors.

The invention is based on the drawing

explained in more detail. .

In Fig. Ι 1 denotes a generator that the generated oscillation to be modulated, and 2 denotes a phase-rotating network in which the capacities C each of the capacitance between each sector of the divided electrode one Condenser microphones and the other, undivided electrode.

The microphone characteristic can be made such by a suitable choice of mechanical constants Course are granted that the low tones of the sound vibrations to be transmitted a significant bring about a greater change in capacitance than the high notes. By means of this device frequency-modulated oscillations are then generated, with the usual integrating network can be omitted, which is otherwise necessary to use phase modulators to frequency-modulate To generate vibrations, and the modulating sound vibrations converts so that the modulated oscillation has a frequency deviation proportional to the 'sound oscillations. In general, however, the microphone characteristic becomes significantly less pronounced granted as a full integration corresponds to the simultaneous favoring of the high notes to accomplish.

The frequency characteristic of such a microphone is illustrated in FIG.

The frequency-modulated or phase-modulated ones occurring in the output circuit of the phase-rotating network 3 Vibrations can, as shown in Fig. Ι, a frequency multiplier for the purpose of increasing the frequency or phase deviation.

Claims (2)

Patent claims: 1. Device for the generation of frequency or phase by sound vibrations' modulated oscillations, in which the oscillation to be modulated is a phase-rotating one Network is supplied, which is dependent on the modulating sound vibrations Phase rotation of the oscillation to be modulated causes, characterized in that the Network contains reactances that are mechanically changed by the sound vibrations. 2. Device according to claim 1, characterized in that that the dependence of these variable reactances on the sound vibrations has a characteristic curve falling towards the high frequencies. For this purpose τ sheet drawings