A differential 0.13/spl mu/m CMOS active inductor for high-frequency phase shifters

This paper presents a novel differential 0.13/spl mu/m CMOS active inductor circuit, which is employed in the design of an integrated negative refractive index metamaterial phase shifter. The active inductor circuit employs a digital/analog tunable feedback resistance to allow controlling both the inductance and the quality factor. The inductance is tunable from 2.5nH to 13.6nH at 5GHz while having a fixed peak quality factor of 100. This results in a phase shift of 36.7/spl deg//stage, at 5GHz, with less than 0.67dB insertion loss.