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

  • 1
    $\begingroup$ 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. $\endgroup$
    – AlexTP
    Jun 2, 2017 at 9:18
  • $\begingroup$ Your question is really good though. We often don't think on these lines with established terminologies. $\endgroup$
    – QMC
    Jun 3, 2017 at 2:08

1 Answer 1


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) $


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