Patrick Pratt

Application of Digital Adaptive Pre-distortion to Mobile Wireless Devices

Low power adaptive pre-distortion (APD) techniques are applied to nonlinear RF power amplifiers for mobile devices. An APD system is demonstrated which reduces spectral regrowth products by 10-20 dB and increases modulation accuracy by 2-6X. The use of APD allows a reduction in 3 G PA supply current by 2X and provides immunity to load mismatches as high as 8:1.

Active noise control using robust feedback techniques

With the resurgence of active noise control in the past two decades, the design and implementation of optimal noise cancellers has been a topic of considerable research. Recently, much of the investigation has focused on fixed controllers that rely on the robustness of closed loop systems to deal with poorly parameterized or changing plants. Many acoustic systems employ internal model controller structures designed via H/sub /spl infin// techniques to attain optimality. Absent from the literature, however, is a qualitative study of classical robust controllers applied to the active noise problem. This paper looks at the practical issues and possible pitfalls of applying H/sub /spl infin/_/optimal feedback controllers to one-dimensional acoustic ducts. In particular, it is observed that the relatively high degree of non-minimum-phase zeros, typical of acoustic plants, limits the ultimate performance of the optimal H/sub /spl infin// solution.