LINC power amplifiers for reducing out-of-band spectral re-growth: A comparative study

The Linear Amplification with Nonlinear Components (LINC) power amplifier structure combiner implementation has an effect on the linearity and efficiency of the design. Understanding and using this tradeoff is helpful to radar and communication designers and can be used to assist in operating with optimum efficiency while meeting spectral mask requirements instituted by regulatory agencies. In this paper, a simulation-based investigation is performed into implementations with a 180-degree coupler and with a Chireix outphasing network. In general, the overall efficiency in both designs is a function of the amplitude modulation of the message signal in the LINC configuration; however, the 180-degree coupler has a potential to obtain higher linearity in many cases due to the isolation of its two input ports. In certain cases of amplitude modulation, however, much of the output power in the 180-degree coupler design is delivered to an unused termination rather than to the network output.