A unifying theory and characterization of microwave oscillator/VCO

Oscillators/VCOs phase noise is an important concern in RF design. Ultra low noise oscillator sources are crucial for the development of high bit rate wireless link system such as point-to-point radios or multipoint radios. This paper presents an analytical method to optimize phase noise of high Q autonomous circuits (oscillators/VCOs). The key point of this approach is to optimize the conduction angle of the RF current leading to minimum phase noise for a given transistor and resonator. The optimization technique is demonstrated through a design example, leading to an ultra low noise oscillator at 2.4 GHz. The measured phase noise at 1 KHz offset frequency is better than -108 dBc/Hz, and to our knowledge this is best phase noise using ceramic resonator so far reported