An injection-locking scheme for precision quadrature generation

We describe a novel quadrature splitter based on injection locking a cascade of ring oscillators to a low-phase-noise (external) single-phase reference clock. The output signals are in accurate quadrature with low phase noise over a wide bandwidth. This scheme inherently operates at high signal frequencies and is insensitive to the shape of the reference clock waveform. Experimental results at 2.7 GHz are reported for a prototype implementation in 0.25-/spl mu/m BiCMOS technology. To prove the viability of this scheme, a single-sideband upconverter was implemented along with the splitter. Over several chips, an average sideband suppression better than 45 dB over a large signal bandwidth of 100 MHz was achieved.