This paper presents a new methodology for airborne wideband space-time adaptive processing (W-STAP) radar systems. In W-STAP, the wideband target signal is first decomposed into a series of narrowband signals. This is referred to as a sub-banding process. The different signals are then combined into a single reference sub-band (usually the center). STAP processing is then performed at this reference band. The combination process is done through a transformation from the different sub-bands into the reference one using the focusing approach H. Wang et al., (1985). In this method, non-singular transformation matrices are used. Compared to the conventional approach proposed in Hoffman et al., (2000), the focusing technique provides greater computational efficiency in wideband STAP systems.