Case Study – Non-Linear Analysis

Measurement-aided Doherty amplifier design - chapter 8

Doherty amplifier non linear analysis
Doherty amplifier non linear analysis

The post-processing of non-linear results can potentially be more expansive than with the linear result dataset. With the linear sweep measurement results to be used as a reference, the engineer is enlightened with the limit of performance capability.

Here, the average versus peak envelope power data is plotted. Whereas the reference linear design offered a 35,5dBm average power and 43,8dBm saturated power, the introduction of shaping prior to the final stage has increase the saturated power capability by 1,7dB (or 47%).

The engineer may leverage this bonus power in different ways.

  • 1. It can be left as-is, and significant output power margin has been built-in.
  • 2. The design can be re-specified for 37,2dBm (whilst maintaining similar peak envelope headroom), whilst also taking advantage of a 5%-pts efficiency boost
  • 3. The design can be remade, using devices which are up to 47% smaller and similarly lower cost (and intrinsically more efficient anyway).
  • 4. The original 35,5dBm/44% efficiency specification may be written over a wider bandwidth.

Ask the expert

Gareth Lloyd

Gareth Lloyd

Gareth Lloyd graduated from the University of Leeds in 1994 with a degree in Electronic & Electrical Engineering. Gareth has worked in various engineering and management roles, in different industries, for major companies including Ericsson, Huawei, ZTE, TriQuint and Andrew Corporation. Gareth joined Rohde & Schwarz in 2015, as a Senior Expert. His primary work focus is performance differentiated radio front-ends (RFFE).

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