2 Phase modulations: Differential Phase-Shift Keying, Quadrature Phase-Shift Keying
Similarly as for OOK, DPSK can be implemented as RZ and NRZ.
It is a type of phase modulation that conveys data by changing the phase of the carrier wave. All subsequent information is coded as 180° phase reversals of the carrier frequency.
- A 180-degree carrier phase reversal preceding a chip shall characterize that chip as a binary 1.
- The absence of a preceding phase reversal shall denote a binary 0.
The main advantage of DPSK is the 3-dB improvement it offers in the receiver sensitivity compared to OOK.
The difference in results between NRZ-DPSK and RZ-DPSK is primarily related to the wider spectrum of RZ-DPSK format.
Transceiver’s construction:
The principle of BPSK modulation – binary zeros and ones are represented by phase states shifted by π from each other, e.g. binary zero is assigned phase π and binary one, phase 0 radians.
The principle of DPSK modulation – a binary one shifts the symbol’s phase by π, binary zero does not shift the phases.