Wireless Communication Technologies 1 Phase noise A practical oscillator does not produce a carrier at exactly one frequency, but rather a carrier that is phase modulated by random phase jitter, which is called phase noise. The oscillator output signal can be expressed by the equation where describes the amplitude variation as a function of time and is the phase variation. corresponds to the phase noise. A well-designed, high-quality oscillator is very amplitude stable and can be consider constant and all oscillator noise is due to

Wireless Communication Technologies 2 Phase noise The easiest technique for measuring oscillator noise is to view the oscillator spectrum directly on a spectrum analyzer. A simulation is shown in the following figure where the phase noise is 90 dBc/Hz at 100 kHz away

Wireless Communication Technologies 3 Sensitivity to phase noise Phase noise basically has two effects. First, it introduces a random phase variation that is common to all subcarriers. The common phase error is strongly correlated from symbol to symbol, so tracking techniques or differential detection can be used to minimize the effects. The second and more disturbing effect is that it introduces ICI, because the subcarriers are no longer spaced at exactly 1/T in the frequency domain