Optimizing a resonator tap for maximizing oscillator carrier-to-noise ratio

Minimizing phase noise of resonator-based oscillators can be done by noise matching. Besides optimizing the biasing current of the input stage of the undamping circuit an impedance transformation is also a very effective technique. Here carrier-to-noise ratio is maximized by optimizing the resonator tap. In this way oscillator phase noise can be close to the limit determined by the noise of the resonator itself. For an example design of an 1 MHz oscillator at a supply of 1.3 V, the total noise is only 0.7 dB from this limit