Wideband LC-VCO design for LTE/LTE-A standards

This paper presents the design of two wideband LC-VCOs dedicated to LTE/LTE-A standards. The first oscillator employs an improved MIM + NMOS-switch varactors to achieve wideband frequency tuning. The second oscillator employs in addition an “8-shaped” inductor to reduce the electromagnetic (EM) interactions involving the oscillator and a dual-Gm start-up boost technique to compensate the losses increase caused by the “8-shaped” inductor. The boost principle is based on a novel way of connecting an auxiliary bipolar transconductance (Gm´) to the oscillator´s tank in order to enhance the global transconductance and boost the oscillation start-up while reducing the total power consumption. The two LC-VCOs are designed in 0.25-μm BiCMOS process. The first oscillator version provides 67.3% tuning-range (4856-9779 MHz), below than -116 dBc/Hz phase noise at 1-MHz offset and 20 mW power consumption from 1.2 V supply voltage. The second oscillator offers 68.7% tuning-range (4821-9867 MHz), a phase noise at 1-MHz offset varying from -121 dBc/Hz to -115 dBc/Hz, at minimum and maximum LTE/LTE-A frequencies, respectively. The maximum power consumption is 18.6 mW from a 1.2 V supply voltage.