Low phase noise oscillator design and simulation using large signal analysis and low frequency feedback networks
Güngör, Çağatay Ertürk
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Spectral purity of oscillators is of great importance in both commercial and military systems. Implementing communication, radar, and Electronic Warfare systems with increasingly higher frequencies, wider bandwidths, greater data rates, and more complex modulation schemes require low phase noise signal sources. There are still discrepancies in the literature about phase noise in signal sources. Although analytical models accomplish to describe the phase noise of known signal sources accurately, a unifying and reproducible model or method that provides a priori information for the design of a low phase noise oscillator is still not established. Due to this lack of methodical approach, mostly empirical design practices that are known to produce good results are widely adopted. Proposed design method is similar. Design and simulation of a low phase noise Dielectric Resonator Oscillator is studied. Noise sources in oscillators are briefly summarized. Phase noise models are compared. Dielectric resonators, which use small, disc-shaped ceramic materials that have high quality factors at microwave and millimeter-wave frequencies, are introduced with a concise theoretical coverage. Effect of circuit configuration on phase noise is studied on two different FET devices. Common-gate configuration gave best simulation results for both transistors. Parameters of coupling to the resonator are studied based on large signal analysis of the active device. The optimal parameters are described with supporting simulation results. Comparisons with suboptimal designs are provided, results indicate that optimization improves the phase noise on the order of tens of dBs. Low frequency feedback method is investigated. Simulation results showed significant improvement in close-in phase noise when such networks are used. A large data set is obtained with input parameters of frequency, device, bias point, and feedback configuration; and optimality of such schemes are discussed based on it. The methods for suppressing both close-in and away from the carrier phase noise are presented in the most generalized way, only to be reproduced for the intended device of operation.