Shared Envelope Tracking for Time-Delayed Power Amplifiers in Phased Array Systems

Analysis shows that multiple time-delayed power amplifiers can share a single envelope tracker and provide a significant improvement over statically supplied amplifiers. Phased arrays are a suitable application of this technique. Our analysis shows a 15 point efficiency improvement over a static supply when amplifying a two-tone signal. We claim that sharing an envelope tracker is justified when $\frac{1}{2} \gg \frac{\Delta f}{f_{0}} \sin(\theta) (N-1$), where $\frac{\Delta f}{f_{0}}$ is the fractional bandwidth of the signal, $\theta$ is the maximum steering angle, and $N$ is the number of elements sharing an envelope tracker. Closed form analytic solutions of a two-tone signal are presented to verify the concept.