The Load-Modulated Linearizer: A Technique for Intermodulation Cancellation in PA Systems

Abstract

A novel application utilizing the load-modulated balanced amplifier (LMBA) principle to actively absorb individual out-of-band intermodulation components at the output of a power amplifier operating in high compression is presented. The system requires nearly the same amount of additional power as the IMD power it absorbs, making it very efficient. It retains the power conservation properties of the LMBA and achieves linearization at a very low power and complexity penalty.

Active Load-Modulated Devices: A General PA Network Solution Identifying Highly Efficient Linearizer Systems

“…Active load-modulation can emulate impedances within and beyond the boundary of the Smith chart. This opens the possibility to selectively absorb undesired signals, such as OOB IMD products, while leaving other signals unaffected independent of the frequency spacing between them [11]. We refer to this process as load-modulated linearization and the LMBA architecture is a suitable platform for developing this concept due to its three key characteristics:…”

“…And second, in Section III, we present an extended analysis of the load-modulated linearizer (LML) [11], which is a variation of the LMBA concept [5], [12]- [14]. The LML absorbs unwanted IMD products, while keeping the main tones unaffected.…”