Design and implementation of a 6-GHz array of four differential VCOs coupled through a resistive network

This paper presents the design and the implementation of a fully monolithic coupled-oscillator array, operating at 6 GHz with close to zero coupling phase, in 0.25 μm BICMOS silicon germanium process. This array is made of four LC-NMOS differential VCOs coupled through a resistor. The single LC-NMOS VCO structure is designed and optimized in terms of phase noise with a graphical optimization approach while satisfying design constraints. At 2.5 V power supply voltage, and a power dissipation of only 125 mW, the coupled oscillators array features a simulated phase noise of −127.3 dBc/Hz at 1 MHz frequency offset from a 6 GHz carrier, giving a simulated phase progression that was continuously variable over the range −64° < Δϕ < 64° and −116° < Δϕ < 116°. This constant phase progression can be established by slightly detuning the peripheral array elements, while maintaining mutual synchronization.