Practical and Efficient Approaches to Device Modeling and Power Amplifier Module Design

A 'best-practices' approach to device modeling and power amplifier (PA) module design optimization is described. It was developed to help designers go from the arrival of footprint and electrical specs to samples-out as fast and accurately as possible. It uses the same modulation signals and average output powers as on the lab measurement benches, properly averages the spec'd quantities (Gain, ACPR, EVM, PAE, IRL,..), and covers the full frequency band. Designing the module involves organizing the simulation output into a single weighted and normalized figure of merit that the optimizer can use as its one-goal error function. This FOM also serves as a meaningful progress monitor, and design-review quality measure. Waveform engineering and gain curve shaping are not explicitly part of the process, but happen ‘under the hood’, automatically, in a properly weighted and averaged way. Physically based and physically scalable (geometrically and thermally) active device models (GaAs HBT and PHEMT) serve as the foundation of the approach, with more emphasis on adherence to known and manageable temperature-dependent device physics than perfect snap-shot model-measurement agreement. Such models are not subor-dinates to the semiconductor fabrication process and measured data, but can help improve the former and monitor the latter. It allows for meaningful investigations of device structure variations and product yield, and promotes accuracy in circuit envelope (CE) and electrothermal (ETh) simulations. The optimization is done with harmonic balance (HB) and S-parameter (SP) simulation data. The setup incorporates envelope tracking (ET) and digital predistortion (DPD) in an efficient way.