A Top-Biased Mutual Negative Resistance LC Oscillator Technique

A CMOS LC oscillator based on the mutual negative resistance (mu-R) with a top-biasing current source is presented. It offers superior phase noise over the traditional top-biased cross-coupled oscillator due to the indirect mutual coupling that results in a suppression of the LC resonator loading by the amplifier transistors. The top-biased mu-R structure also enables a low power quadrature oscillator implementation by virtue of coupling of two mu-R oscillator stages via the secondary coils with no use of parallel transistors. Verified via simulation at 1.8 V and 3.0 GHz operation, the mu-R oscillator outperforms the cross-coupled counterpart with identical parameters by more than 5 dB. Simulation of the quadrature mu-R oscillator is also given where it offers a power reduction by half compared to the quadrature cross-coupled oscillator.