Angle modulation

Angle modulation is the generic term for phase angle modulation and frequency modulation .

Angle modulation types are modulation types in which the instantaneous phase angle of the carrier is influenced by the signal to be transmitted.

In the phase modulation of the relative phase angle of the carrier is by the instantaneous value of the signal voltage influenced . With frequency modulation, the frequency of the carrier is influenced by the instantaneous value of the signal voltage . ${\displaystyle \Delta \varphi _{T}}$ ${\displaystyle \Delta \varphi _{T}(t)\sim U_{S}(t)}$ ${\displaystyle f_{T}(t)}$ ${\displaystyle \!\ \Delta f\sim U_{S}(t)}$

The current frequency of the carrier corresponds to the time derivative of the phase angle . ${\displaystyle f_{T}(t)}$ ${\displaystyle \varphi _{T}(t)}$ ${\displaystyle f_{T}(t)={\dot {\varphi }}_{T}(t)}$

With frequency modulation, it is more difficult to transmit the high frequencies of a useful signal because the phase deviation becomes smaller as the signal frequency increases. In order to counteract a correspondingly poor signal-to-noise ratio behind the modulator, a pre-emphasis is applied to the useful signal in the transmitter in VHF broadcasting . This preemphasis is reversed with a deemphasis in the receiver.

With phase modulation, it is more difficult to transmit low frequencies because the frequency change of the carrier signal is proportional to the signal frequency and therefore there is only a slight change in the carrier frequency at low signal frequencies.

See also

• Quadrature amplitude modulation

Web links

• Overview of modulation methods (186 kB)