DESIGN OF HIGH FREQUENCY OSCILLATORS: NOISE CHARACTERIZATION, DESIGN THEORY, AND MEASUREMENTS

A design theory for high frequency oscillators is presented. Emphasis is placed on oscillator design techniques which are applicable to the electrical tuning of LC and transmission line resonators. Attention is paid to design approaches which yield an oscillator with high spectral purity and a large signal to noise ratio. Theory and measurements demonstrate for the oscillator configurations investigated the a small L/C ratio is desirable for improved oscillator signal to noise ratio. Equations are developed which define the noise figure the oscillator due to the additive noise of the active device. This analysis demonstrates the need for a high device starting transconductance which should be subsequently reduced during oscillation to minimize the device noise contribution. A relationship is developed between the receiver dynamic range and the oscillator signal to the noise ratio. Oscillator designs in the region 20 Mhz - 200 Mhz verify the analysis. A unified approach to large signal oscillator design is investigated and relationships to oscillator signal to noise ratio using the previously developed theory are noted