#### Example 5.5

## Detection of PSK

There is no non-coherent equivalent detection process for PSK, and various forms of coherent detection must be employed. The ideal detector thus requires perfect knowledge of the unmodulated carrier phase at the receiver. As with ASK, any phase error q of the locally generated carrier reference reduces the signal voltage at the output of the detector by a factor cos(q). This in turn (see example) degrades the Es/N0 performance of the detector by a factor cos2(q). Thus we need zero phase error for optimum detection and must re-visit the whole area of carrier recovery. Note that if the phase error reaches 90°, the output falls to zero! |