Introduction to Envelope Tracking - Cambridge Wireless

Introduction to Envelope TrackingG J WimpennySnr Director Technology, Qualcomm UK Ltd EER first proposed by Leonard Kahn in 1952 to improve efficiency of SSB transmitters ET offers similar efficiency enhancement to EER but has fewer drawbacks Technique not widely adopted for many years due to difficulty of implementation, particularly for wide bandwidth signals In the last few years the implementational issues have been overcome and ET is now widely used to improve PA efficiency in Cellular HandsetsEnvelope Tracking Historical Context2 Modern high spectral efficiency Wireless communications standards have high Peak to Average Power Ratio (PAPR) 4G/LTE, WiFi Conventional fixed supply Power Amplifier has to use supply voltage high enough to support Peak Power, but is only energy efficient at the peaks.

Calculated RF sideband level for ideal AM modulator -49.6dBC Measured RF sideband level -51dBC PA Supply Sensitivity (dB) -1.4dB PA Supply Sensitivity (%) 85% env env rf rf V V V V ' ' env env V 'V rf rf V 'V dBm 0-10-20-30-40-50-60-70-80-90-100 SoftPlot Measurement Presentation Trace A Start: 0 Hz Stop: 200.0000 MHz Res BW: 100 kHz Vid BW: 300 ...

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