JPL's Wireless Communication Reference Website Chapter: Analog and Digital Transmission Section: Analog Modulation

The audio SNR for NBPM appears to be proportional to the square of the phase deviation.

Phasor diagram for AM

Phasor diagram for PM

NBPM has advantages over AM, because

• NBPM is constant envelope
  • This allows the use of class C power amplifiers in the mobile transmitter. This saves battery power.
  • The receiver can more easily distinguish wanted PM modulation from unwanted amplitude fading (However, fading also produces phase noise)
• If the phase deviation is large: Less received power is needed for the same audio SNR.

JPL's Wireless Communication Reference Website © 1993, 1995.