General Combiner Initialization Workflow for All Types of Active Load Modulation Power Amplifiers

A highly trackable and computationally efficient combiner initialization workflow is introduced that can be applied to any type of power amplifier (PA) employing active load modulation (ALM), such as Doherty PAs (DPAs), outphasing transmitters, load modulated balanced amplifiers, and circulator load modulated amplifiers. The workflow is based on a tunable combiner and associated boundary conditions derived from single-transistor load-pull. As a result, the PA's topology is fixed in advance, clearly distinguishing this technique from existing analytical algorithms. The ability to transition seamlessly from load-pull to an educated initial design of the desired ALM scheme is demonstrated using a two-way inverted DPA based on compact models of Infineon's GaN-on-Si transistors at 3.6 GHz. Apart from its inherent single-frequency limitation, which can be overcome by sampling the band of interest, the software-aided nature of the novel design workflow allows both non-reciprocal components and measured data to be included in the tunable combiner, resulting in unprecedented versatility.