The Design of Low Noise Oscillators - A. Hajimiri and Thomas H. Lee

Buttom line: great book by the two of the greatest authorities in oscillators design.
Go and buy it!

Details:
This comprehensive book provides a quantitatively model of how circuit noise becomes oscillator phase noise and uses this new model to describe how to design low noise oscillators. The emphasizes is on integrated oscillators. It exploits so-called cyclostationary properties of noise to improve the spectral purity of the oscillator. This book applies, examines in great detail the behavior of both tuned and relaxation oscillators. Long-standing conundrums (such as "what is the optimum number of stages in a ring oscillator?") are resolved at last, and an important framework for answering questions as yet unasked is provided.

Hajimiri and Lee's book is the most complete analysis of noise in oscillators their approach to noise modeling has rendered previous work obsolete. It clarifies a large number of highly debated issues about VCO noise and provides tangible design guidelines that can be used to optimize the noise performance of integrated VCOs. I enjoyed it a lot and highly recommend it to anyone tired of ad hoc analysis and empirical design of VCOs.