Experimental investigations of MIMO in the HF band

Previously, the majority of developments in the area of multiple input multiple output (MIMO) technology have been confined to short-range wireless applications operating in the VHF, UHF and SHF bands, with very little research conducted in the lower frequency bands. Recently, several experimental campaigns have been performed over a 255 km radio link between Durham and Leicester in the UK in order to investigate the feasibility of applying MIMO techniques to communications within the HF band. Results have indicated that traditional spaced HF antenna arrays can be replaced by compact, active, heterogeneous arrays with the consequence that de-correlation between the various antenna elements is achieved at a single location. This paper summarises the details of compact antenna arrays and presents significant results obtained on deploying these antenna arrays.