elneos five EN

Amplitude and frequency modulation Amplitude modulation (AM) With the amplitude modulation, the amplitude of a high-frequency carrier is modulated depending on the low-frequency wanted signal which is to be transferred. Frequency modulation (FM) With the frequency modulation, the frequency of a high-frequency carrier is modulated depending on the low-frequency wanted signal. Example of an amplitude modulation with a modulation depth of 50% n Carrier signal (high-frequency) n Wanted signal (modulating) n Modulated signal with a modulation depth of 100% n Modulated signal with a modulation depth of 50% Pulse width modulation (PWM) With the pulse width modulation a technical dimen- sion (e.g. current) changes between two values. The pulse duty factor of a rectangle pulse is modu- lated at a constant frequency. Consequently, the width (extent) of the pulse is influenced. A pulse width modulation is realized by the compari- son between a continuously ascending and descen- ding signal (triangle or saw tooth) with the analogue input signal. The ascending or descending signal is above or below the input signal for a certain time. At the intersection point the digital output signal is changed over and this results in the PWM signal. This signal can be transported without much energy input across a long distance and the PWM voltage process acts on inert consumers like a sinusoidal voltage. Field of application Communications engineering: Transfer of analogue measured values of sensors over long cables or by radio communication, for the use with big radio transmitters and many more. Power electronics: Low lost energy with power switches, DC regulators, electric motors, heating elements, dimmers, switching power supplies and many more are controlled by PWM signals. A sinusoidal process (n) can,for example,be converted in a PWM signal (n) by the comparison with a saw tooth-shaped signal (n). For each PWM pulse, the saw tooth ramp passes trough the entire value range. This means that the PWM voltage process acts on inert consumers such as motors like a sinusoidal voltage. Time PWM Signal Source Signals 1 0 1 0 Signal AM FM y1 = sin(100·x) y2 = sin(x) y3 = sin(x) · sin(100·x) y4 = y3 · modulation depth elneos® five | 53

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