To achieve a phase shifting function having lower transmission loss and better phase shift performance for transceivers in adaptive antenna array applications, a phase shifter requiring a chip area of only 623 /spl times/ 370 /spl mu/m/sup 2/ using a 250nm CMOS process is developed. The proposed tunable transmission line phase shifter consists of a coplanar waveguide used as a lumped inductor merged with an accumulation NMOS capacitor used for phase control. The merged structure reduces parasitic effects. The measured phase shift range for the proof-of-concept prototype is 22/spl deg/.