IQ signal generator using 2nd-harmonic injection locked oscillator

A new approach to generate quadrature signals is proposed. The method is based on the injection and locking of a couple of L-C VCOs at the second harmonic through a nonlinear feedback loop. This procedure allows the direct generation of four equal amplitude signals with well-defined phases of 0°, 90°, 180° and 270°, in the whole tuning range of the VCOs. A demonstrator prototype of the generators has been built using SiGe BiCMOS technology from Austria Microsystems. The resulting system operates in the frequency range from 1.66 GHz to 2.68 GHz and demonstrates the reliability and robustness of the proposed quadrature generation procedure.