A high output power and low phase noise GaN HEMT VCO with array of switchable inductors

This paper presents cross-coupled voltage-controlled oscillators (VCOs) involving array of switchable inductors (i.e., N = 1 and N = 2 switchable inductors) and implemented using gallium-nitride high electron mobility transistors on Si substrate technology for worldwide interoperability for microwave access applications. Band selection and coarse frequency tuning were achieved using the array of switchable inductors, whereas fine tuning was controlled using varactors. Two bands were obtained using the one-stage switchable inductor VCO operating in the ranges 3.41–3.57 GHz and 3.85–3.94 GHz. The VCO output power (P_out) was 21.8 dBm at 3.57 GHz from a 10-V power supply. Four continuous bands were obtained using the two-stage switchable inductors VCO operating in the range of 3.16–3.4, 3.25–3.64, 3.48–3.71 and 3.64–3.9 GHz, respectively. An additional band was generated by fine-tuning the inductance through mutual coupling between the transmission line and one of the inductors. The proposed two-stage switchable inductors VCO provided a 21% tuning range at frequencies ranging with a control voltage ranging from 12 to 20 V, a low phase noise of −123 dBc/Hz at a 1-MHz offset from a 3.3-GHz carrier and a P_out of 21 dBm at 3.5 GHz from a 10-V power supply.