quadrature coupled lc oscillators

Coupled LC oscillators are known to provide good performance in terms of phase noise, signal amplitude, power consumption, and quadrature output signals. However, IQ amplitude and phase mismatches in these oscillators can be quite large due to the serious mismatch problem of large area inductors and varactors. A simple design modification of the coupled LC oscillators shows a significant improvement of the amplitude and phase mismatches. Detailed operational principle is examined. A 2V 900Mhz prototype using this simple idea has been designed and is in fabrication. The full paper