Analytical expressions for the PM noise in FET oscillators are derived in terms of the FET equivalent circuit elements and the passive circuitry. Efficient methods to reduce the PM noise in fundamental and in harmonic modes are suggested and implemented. The effects of the different FET equivalent circuit parameters on large-signal, small-signal, and noise behavior of FET oscillators are investigated. Finally, the effects of harmonic signal on the output noise power and on the phase noise at both fundamental and harmonic frequencies are determined.