The RF front-end – antenna combination is a vital part of a mobile phone because its performance is very relevant to the link quality between hand-set and cellular network base-stations. The RF front-end performance suffers from changes in operating environment, like hand-effects, that are often unpredictable.
Adaptive RF Front-Ends for Hand-Held Applications presents an analysis on the impact of fluctuating environmental parameters. In order to overcome undesired behavior two different adaptive control methods are treated that make RF frond-ends more resilient: adaptive impedance control, and adaptive power control.
Several adaptive impedance control techniques are discussed, using a priori knowledge on matching network properties, in order to simplify robust 2-dimensional control. A generic protection concept is presented, based on adaptive power control, which improves the ruggedness of a power amplifier or preserves its linearity under extremes. It comprises over-voltage, over-temperature, and under-voltage protection.
Table of Content
Symbols.- Abbreviations.- 1 Introduction.- 2 Adaptive RF frond-ends.- 3 Adaptive impedance control.- 4 Adaptive power control.- 5 Conclusions.- Appendix A Overview of adaptively controlled matching networks.- Appendix B A dual-banding technique.- Appendix C Transistor breakdown voltages.- References.- Summary.
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