8-PSK Modulation: Understanding Multilevel Phase Shift Keying

This page describes 8-PSK modulation basics, also known as multilevel PSK modulation. This is a type of digital modulation where the carrier’s phase is changed to represent digital data. In Phase Shift Keying (PSK) modulation, the phase of the carrier signal is altered according to the digital input.

It’s a digital modulation technique used in various applications, including broadcast video, aircraft, and satellite systems. We can achieve better bandwidth efficiency by mapping more than one bit to each signal element.

In Binary Phase Shift Keying (BPSK), digital data (1s and 0s) is represented by a 180-degree phase change.

In Quadrature Phase Shift Keying (QPSK), a phase shift of 90 degrees is used, mapping 2 bits onto each signal.

Multilevel PSK takes this further by mapping more than 2 bits using different phase angles. For instance, in 8-PSK, eight different phase angles are used, representing 3 bits.

The figure below shows a constellation diagram of an 8-PSK signal.

Fig. 8-PSK modulation technique