# Confusion between PSK and QPSK

What is the difference between PSK (Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying)? Doesn't PSK need quadrature component for its working?

• PSK is not necessarily QPSK. QPSK is PSK. en.wikipedia.org/wiki/Phase-shift_keying#Higher-order_PSK They all have inphase and quadrature components. Jun 2 '17 at 9:18
• Your question is really good though. We often don't think on these lines with established terminologies.
– QMC
Jun 3 '17 at 2:08

QPSK modulation is a PSK modulation with exactly 4 constellation points. The constellation points for QPSK are normally at $\left(\pm\dfrac{1}{\sqrt{2}}\pm\dfrac{1}{\sqrt{2}}j\right)$