Energy Efficiency Enhancement and Linear Amplifications: An Envelope-Tracking (ET) Approach

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review


This chapter presents the envelope-tracking (ET) technique, its general design considerations, and a silicon-based design example. This ET technique has been widely used for backoff efficiency enhancement of radio frequency power amplifiers (PAs) in broadband wireless applications. The chapter starts with a short introduction on why the ET-PA architecture is very attractive for low-power 3G/4G handset PA design. Then, the general design considerations and trade-offs in an ET-PA are presented, particularly with an emphasis on silicon-based implementation. The ET-PA example uses a pseudo-differential PA designed with two integrated SiGe power cells fabricated in a 0.35μm SiGe BiCMOS technology with through-silicon-via. In the continuous wave measurement, the PA achieves a saturated output power (POUT) of around 2W with power-added efficiency (PAE) above 65% across the bandwidth of 0.7-1.0GHz. To optimize the ET-PA system performance, several envelope-shaping methods such as DC shifting, envelope scaling, envelope clipping, and envelope attenuation at backoff have been investigated carefully. A highly efficient monolithic CMOS envelope modulator integrated circuit is designed in a 0.35μm bipolar-CMOS-DMOS process to mate with our SiGe PA. With the LTE 16 QAM 5/10/20MHz input signals, our ET-PA system achieves around 28dBm linear POUT, passing the stringent LTE linearity specifications, such as the spectrum emission mask with an average composite system PAE of 42.3%/41.1%/40.2%, respectively. No predistortion is applied in this design example, suggesting broadband ET-PA can be applied to handsets, as the first ET-PA handsets already on the market at 2014.

Original languageEnglish
Title of host publicationRF and mm-Wave Power Generation in Silicon
PublisherElsevier Inc.
Number of pages28
ISBN (Print)9780124080522
StatePublished - Jan 1 2016


  • Envelope modulator (EM)
  • Envelope tracking (ET)
  • Envelope-shaping method
  • Long-term evolution (LTE)
  • Polar transmitter
  • SiGe power amplifier (SiGe PA)
  • Through-silicon-via (TSV)


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