Frequency Modulation (FM)

Manipulates frequency instead of amplitude. The amplitude of the information signal causes the resulting modulated signal frequency to increase (higher amplitude) or decrease (lower amplitude).

Amplitude to Frequency mapping

VCO (Voltage Controlled Oscillator)

Simple FM modulator Voltage Controller Oscillator

Modulation Index and Signal Bandwidth (βfm)

Differential Demodulation

Receiving FM into Complex Baseband

Complex Differentiation Discriminator (Non-coherent Demodulation)

Complex Delay Line Discriminator

Phased Locked Loop Demodulator (Coherent demodulation)

Other concerns specific to commercial FM radio