A 1.9 GHz low phase noise complementary cross-coupled FBAR-VCO in 0.18 μm CMOS technology

A 1.9 GHz film bulk acoustic resonator (FBAR) based complementary cross-coupled voltage-controlled oscillator (VCO) designed in 0.18 μm CMOS is presented. DC latch and low frequency instability problems have been solved by the cross-coupled pairs with DC block capacitors. The open loop gain has been analyzed and optimized by considering the effect of transistors' size on enhancement of the stability at low frequencies and the loop gain at the desired oscillation frequency. The optimization of the phase noise has been done by considering the effect of PMOS transistors' size on the quality (Q-) factor and the impedance of FBAR. The final fabricated chip is packaged in dual in-line package (DIP) and the measured performance shows that the proposed FBAR-VCO achieves a phase noise of -148 dBc/Hz at 1 MHz offset with a figure of merit (FOM) of -212 dBc/Hz.