Phase-change Reconfigurable RF and Analog Integrated Circuits

The need to accommodate increasing numbers of standards and functions makes reconfigurable integrated circuits attractive. Reconfigurable digital and mixed-signal circuits are commonly implemented using MOS switches. Reconfigurable radios that can accommodate multiple standards are conceptually attractive for smart phones and tablets, however, reconfiguration of the underlying RF circuits using MOS switches can result in poor performance due to high parasitic capacitance and high ON state resistance (RON). While MOS switches can be used for capacitance-only switched resonators, resonators with capacitance and inductance switching are desirable to reduce chip area and to optimize the tank Q over a wider frequency range. Such reconfigurability requires extremely low RON and small parasitic capacitance from the switches, which MOS transistors can achieve only with stringent design trade-offs or severe performance penalty.;This paper describes the use of reconfigurable phase-change (PC) vias that can be reversibly switched between high ROFF and low RON states to program RF front-end circuits. Two VCO's using (i) a series-connected (SC) and (ii) a coupling-controlled (CC) PC via-reconfigurable inductor to switch their operating bands by widely separated frequencies are designed and fabricated to demonstrate the efficacy of PC vias in reconfiguring RF circuits. Wide tuning ranges of 2.89-4.23/4.93-7.79 GHz and 4.80-8.53/5.28-10.20 GHz were achieved in the OFF/ON states for the SC and CC VCO's. The measured phase noise over the entire tuning range was lower than -103.4 and -102.7 dBc/Hz, at 1 MHz offset, respectively.