Envelope tracking mechanism for improving efficiency of PA.

[alexandr22061986]

Hi

I need explanation about envelope tracking mechanism for improving efficiency of PA.

 

[jayce3390]

Re: Envelope tracking

Envelope tracking circuit consits of a two ways circuit, a low frequency path driving PA drain according to envelop modulation BW, and a main path with input RF signal.
The PA efficiency is directly improved because the PA bias point moves with input signal, then you can reduce waste of power.

 

[totowo]

Envelope tracking

Envelope tracking means that, a envelope detector to adjust the bias of a linear PA, in order to prevent the PA from working in the shallow class A which is inefficient.........The key is always keeping the linearity param (IMR, ACPR...etc.) satisfied within your spec.

An alike way is named "Envelope Elimination & Restoration" (EER or Kahn method), the difference is the PA in EER is a nonlinear PA(switching PA)...driven by a phase-only signal and modulated by a envelope driver......


If the envelope and phase signal is already apart in baseband, another name of "polar method" is more usual. In recent years, many papers on GSM PA --> EDGE PA adopted this method.