# modulator

A modulator is a device or part of a device with which a signal is modulated .

The following parameters of a signal can be modulated:

## Communications engineering

Modulators are used in communications technology to transmit information . In order to be able to transmit information from the transmitter to the receiver , the carrier wave (the high-frequency signal with the frequency ) must be modulated with the information (e.g. voice, data; the low-frequency modulation signal with the frequency :) . ${\ displaystyle f_ {t}}$${\ displaystyle f_ {m}}$${\ displaystyle f_ {t} \ gg f_ {m}}$

Depending on the type of modulation, the modulator must change the corresponding size in time with the information.

An example from practice: A VHF radio transmitter (e.g. 100 MHz) generates a carrier wave with an average frequency of 100 MHz, but changes (modulates) its frequency in time with the AF signal (speech, music). This can be done, for example, with a capacitance diode in the resonant circuit of the HF oscillator to which the LF signal is sent. This changes its capacitance and thus the resonance frequency of the oscillating circuit in time with the LF signal.

## Optics / laser technology

In optics , a modulator refers to an optical component used to impart acoustic , electrical or magnetic characteristics to light waves. This can be, for example, a temporal amplitude or phase distribution .