## Example 5.7

#### A binary PSK modem uses a preamble data word to achieve symbol synchronization in the receiver. This symbol timing reference, however, drifts between resynchronization bursts so that the timing is in error by 10% when the next synchronisation update is received. If the PSK detector uses an integrate and dump filter, and the symbols are not shaped, what will be the worst-case degradation on the effective received symbol energy due to the timing error?

### Solution

#### With reference to the diagram below, the 10% timing error in the symbol sampling time will result in the voltage at the output from the integrator when sampled being reduced by 90% of the optimum value. This in turn will result in a fall of 81% (0.9 x 0.9) in the effective symbol energy, equivalent to a 0.91 dB degradation in Eb/N0 performance for the modem.

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