Four-level heterodyne video systems: a comparison of DQPSK and 4-FSK

Experimental implementation of four-level heterodyne video systems using 4-ary FSK (frequency shift keying) are described and compared to DQPSK (differential quadrature phase-shift keying). The results show that the receiver sensitivity and complexity of the two systems are very similar. However, DQPSK provides a much higher spectral efficiency and is therefore preferable for video distribution systems. >