In conventional Multiple-Input Multiple Output (MIMO) systems, each antenna requires its own Radio Frequency (RF) chain. Since each RF-chain includes several active components that have to be synchronised, costs and complexity become restrictive. The outphasing MIMO and the outphasing precoder architectures are possible approaches to mitigate this problem. The core of both architectures are Outphasing Elements (OEs), which are used to form a electronically controllable, passive antenna feed network. These OEs are analysed with respect to component tolerances. The feasibility of the outphasing concept is demonstrated by the implementation of a hardware prototype OE. The performance of this prototype is measured and compared to theoretical predictions with good agreement.