An Ultra-Compact CMOS Variable Phase Shifter for 2.4-GHz ISM Applications

An ultra-compact monolithic microwave integrated circuit active variable phase shifter is proposed and implemented using CMOS technology. It is a reflective-type phase shifter consisting of a compact three-transistor active circulator and a second-order LC network. The use of an active inductor in the second-order LC network makes this phase shifter all active and ultra compact with a size of only 0.357 including bonding pads. The phase shifter was designed and demonstrated at 2.4 GHz and has a linear and continuously tunable range of 120 across the 2.4-GHz industrial-scientific-medical band.