Accurate power control technique for handset PA modules with integrated directional couplers

This paper describes an accurate power control technique for handset PA modules (PAMs) with internal closed loop control. Our design approach is the first to include two integrated directional couplers in a handset RF PAM. It significantly improves power control accuracy over load variations. Directivity of the integrated couplers is also proved to be critical for establishing accurate power control over phase variations at high values of load VSWR. With our unique design we achieved directivity as high as 14.3 dB. When the load VSWR is equal to 6:1, we demonstrated that our design reduces output power variation to +/-1.2 dB. Under the same conditions, we measured two other major commercial modules that are not utilizing integrated directional couplers. They exhibited an output power variation of 5.5 dB.