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 cell phone simply because its functionality is particularly correct to the hyperlink caliber among hand-set and mobile community base-stations. The RF front-end functionality suffers from adjustments in working setting, like hand-effects, which are frequently unpredictable.

Adaptive RF Front-Ends for handheld Applications provides an research at the influence of fluctuating environmental parameters. on the way to conquer undesired habit assorted adaptive keep an eye on equipment are handled that make RF frond-ends extra resilient: adaptive impedance regulate, and adaptive energy control.

Several adaptive impedance keep an eye on concepts are mentioned, utilizing a priori wisdom on matching community homes, so one can simplify strong 2-dimensional regulate. A ordinary security suggestion is gifted, in line with adaptive strength keep an eye on, which improves the ruggedness of an influence amplifier or preserves its linearity less than extremes. It includes over-voltage, over-temperature, and under-voltage protection.

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5, this conclusion will be discussed in a broader context. 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.

3 Fluctuations in Operating Conditions 15 Phone environment Link quality Antenna impedance Battery charge Pout (A) Load impedance (B) Vsupply (C) Ambient temp. (D) Relationships Collector voltage (I) (b) Efficiency Clipping Distortion Talk time (1) Link quality (2) Die temperature (II) Collector current (III) (a) Avalanche instability Local heating Electro-thermal instability Blow-out Destructive breakdown (3) Fig. 1 The performance of a cellular phone RF front-end is affected by its fluctuating operating environment, which is visualized as a simplified chain of causes and effects l l l Ambient temperature The phone ambient temperature varies with changes in user and weather conditions.

For instance, the load impedance ZLOAD can be detected in order to correct for variations in antenna impedance by a tuneable impedance matching network. In this manner, all four singly dependent variables can be stabilized, in principle. Of course, stabilization of the input power PIN is not practical because the PA output power must be variable over a very wide dynamic range. Usually, the bias voltage UBIAS is stable, because it is often determined by a band-gap defined reference voltage UREF.

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