Dual-Band Voltage-Controlled Oscillator for CB and HF RFID Bands in a Flexible IGZO Technology

In this work, a cross-coupled voltage-controlled oscillator (VCO) for the high frequency RFID and citizen bands (CB) is investigated, and implemented on a flexible Indium gallium zinc oxide (IGZO) thin film transistor (TFT) technology. To circumvent the challenges of integrating passive components in this frequency range and minimize the circuit’s footprint, the resonant tank is designed as a parallel connection of an active inductor with a metal oxide semiconductor (MOS) capacitor -yielding a total area of 200μm by 330μm. The VCO can operate in the CB mode at 10V power supply, boasting a tuning range from 26.9MHz to 27.7MHz and a dc power of 1.93mW, or in the RFID mode from a 4V supply, obtaining a 12.9MHz -13.6MHz range at 140mW dc power. To the best of the authors’ knowledge, this circuit possesses the highest figure-of-merit (frequency/total power), and overall highest oscillation frequency for VCO reported up to date in comparable technologies.