07. Measuring a power amplifier under dynamic operating conditions

The problem

State of the art microwave power amplifier measurements use a measurement in a fixed operating point with a fixed signal. As these amplifiers are operated in more and more diverse and variable environments, the need for a characterisation of the devices over a wider range of complex operating conditions grows too. To tackle the challenges imposed by the massive MIMO communication, characterisation will be required over a wide frequency band, a wide range of powers, and a wide range of linear and nonlinear loading impedances. Current instrumentation falls short to meet these challenges.

The idea

We want to measure the linearized and nonlinear behaviour of the PA over a range of powers, a broad frequency band and a variable loading impedance in a single experiment. To this end, we first design a non-stationary signal that covers the space. Next, we use transient and time-variation detection and estimation techniques to impose a user-specified accuracy level. To tackle the complex non-linear loading of the PA’s that are connected to a MIMO antenna panel, we use a second amplifier that is driven in nonlinear regime and is used as an active, nonlinear load for the device under test.

Your contribution

To tackle this engineering challenge, you will

  • design the non-stationary signals off-line, perform a measurement and then assess the level of transient and time-varying behaviour present in the response.
  • Link the measured non-ideal behaviour to the accuracy of the measurement, and adapt the designed signal if needed
  • extract the nonlinear behaviour of the PA and its dependence op power level, and output impedance presented by the load
  • use active load-pull with a second amplifier that is driven in nonlinear regime to create a nonlinear loading impedance for the PA
  • use the model with the nonlinear loading to predict the influence of the nonlinear crosstalk on a MIMO antenna driven by the PA


Yves Rolain
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