THE ACTIVE DEVICE CHARACTERIZATION AND MODELING PROBLEM IN LOW PHASE NOISE MICROWAVE-OSCILLATOR DESIGN

The conversion of low frequency noise into phase noise in a high frequ ency oscillator depends strongly on the active device type and operati ng conditions. Experimental set-ups are presented to achieve the choic e of a transistor to be used in low noise oscillators and to study the correlation between phase noise and low frequency noise. Modelling gu idelines are then described to help in the understanding of the noise conversion process. Simple rules of noise reduction are derived from s implified small signal models but the emphasis is put on more complete modelling approaches. These accurate models are affected by yet unsol ved (or partially unsolved) problems such as : the influence of the la rge signal behaviour on the noise sources or the physically unacceptab le cancellation of the phase noise in special biasing conditions.