2.2 GHz LC VCO for RFID on a 0.5-μm digital gate-array designed for ultra-thin silicon substrates

A new technology provides opportunities in the implementation of radio frequency identification (RFID) tags. A test chip comprising four transmitter circuits is implemented on a 0.5-μm gate array designed for flexible ultra-thin silicon substrates (20 μm). Two transmitters are based on the cross-coupled oscillator topology and two are based on ring oscillators. The main focus of this paper is the cross-coupled voltage controlled oscillator (VCO) core that operates at 2.2 GHz with a 20% tuning ratio. It features a four band frequency tuning characteristic utilizing a binary-weighted switched capacitor bank and metal-oxide semiconductor (MOS) varactors. Power consumption of the VCO core is 20 mW with a tail current of 5 mA and a signal swing equal to 588 mV. Simulated phase noise is -65 dBc/Hz at 100 kHz offset.