A 67 GHz dual injection quadrature VCO with −182.9 dBc/Hz FOM in 90-nm CMOS

Investigation of Coupling Mechanisms for Efficient High Power and Low Phase Noise E-Band Quadrature VCOs in 130nm SiGe

“…An alternative approach to couple oscillators for quadrature operation is, for example, using a coupling network at the oscillator's fundamental frequency. Different realizations have been demonstrated with both passive coupling networks [27], where the required phase shift is introduced by capacitive coupling, and also active coupling networks [28], [29], [30], where amplifiers shift the phase.…”