Adaptive RF Front-Ends for Hand-held Applications by Andre van Bezooijen, Reza Mahmoudi, Arthur H.M. van Roermund

By Andre van Bezooijen, Reza Mahmoudi, Arthur H.M. van Roermund

The RF front-end – antenna mix is an important a part of a cellular phone simply because its functionality is especially proper to the hyperlink caliber among hand-set and mobile community base-stations. The RF front-end functionality suffers from adjustments in working atmosphere, like hand-effects, which are frequently unpredictable.

Adaptive RF Front-Ends for handheld Applications provides an research at the influence of fluctuating environmental parameters. so one can conquer undesired habit diverse adaptive keep an eye on equipment are handled that make RF frond-ends extra resilient: adaptive impedance keep watch over, and adaptive strength control.

Several adaptive impedance regulate concepts are mentioned, utilizing a priori wisdom on matching community houses, as a way to simplify strong 2-dimensional keep watch over. A widely used defense proposal is gifted, according to adaptive strength keep an eye on, which improves the ruggedness of an influence amplifier or preserves its linearity less than extremes. It contains over-voltage, over-temperature, and under-voltage protection.

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Extra resources for Adaptive RF Front-Ends for Hand-held Applications

Example text

In this book we make use of control systems that are based on feedback in order to become insensitive to inaccuracies of the forward path, which is important for the following reasons. In case of adaptive impedance matching, treated in Chapter 3, small variations in component values can result in large variations of the matching impedance,1 especially for high-order matching networks that need to tune over a wide load impedance and frequency range. Especially the accuracy of RF-MEMS capacitors is rather limited, due to variations in dielectric layer thickness, roughness, plate and spring bending, etc.

18 2 Adaptive RF Front-Ends 10,000 ICOL_n [A] 1,000 0,100 DC n=1 0,010 n=2 n=3 0,001 0,1 1 AIN / UT 10 Fig. 3 Visualization of the harmonic collector currents ICOL_n as a function of the input signal AIN normalized to the thermal voltage UT. 2 Voltage Fluctuation In this section we derive the operating conditions at which the collector voltage is most extreme, because these extremes are relevant to avalanche break-down of the power transistor and distortion due to clipping. 2d), and the magnitude of the load impedance ZLOAD_n.

Im{Γ} X G - plane Z - plane |Z|⋅sin(jZ) |Γ|⋅sin(q Γ) |Z| qΓ 0 |Γ|⋅cos(q ) 1 Γ jZ 0 |Z|⋅cos(jZ) |Γ| Re{Γ} R Fig. 2 A Polar and Cartesian representation of the impedance Z and reflection coefficient G 2 The impedance of a receiving antenna exhibits a negative real part covering the left-handside of the Z-plane. 1 Introduction 39 Hence, in general adaptive impedance matching requires control in two dimensions simply because impedance has two dimensions. In special cases however, adaptive impedance matching can be simplified in to 1-dimensional control.

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