CH4-ANGLE-MODULATIONS

ANGLE MODULATION


PHASE AND FREQUENCY MODULATION

NARROWBAND ANGLE MODULATION

SINUSOIDAL (OR TONE), MODULATION

GENERATION OF ANGLE-MODULUED


Narrowband Angle-Modulated Signals

Wideband Angle-Modulated Signals
There are two methods of generating wideband (WB) angle-modulated signals; the indirect method and the direct method.

Indirect Method of Armstrong In this method, an NB angle-modulated signal is produced first and then converted to a WB angle-modulated signal by using frequency multipliers. The frequency multiplier multiplies the argument of the input sinusoid by n.

Use of frequency multiplication normally increases the carrier frequency to an impractically high value. To avoid this, a frequency conversion (using a mixer or DSB modulator) is necessary to shift the spectrum.

Integration of the discriminator output yields a signal which is proportional to m(t). A demodulator for PM can therefore be implemented as an FM demodulator followed by an integrator. A simple approximation to the ideal discriminator is an ideal- differentiator followed by an envelope detector