A 
multiple input multiple output (
MIMO) calibration device (360) for calibrating a 
phase relationship between at least two signals present on at least two 
radio frequency (RF) paths 
coupling a 
wireless communication unit and the 
MIMO calibration device (360) is described. The 
MIMO calibration device (360) is operably coupleable via at least two RF paths between a 
wireless communication unit and an antenna arrangement (219). The calibration device (360) comprises a 
processing module (490) configured to: process a coupled amount of at least one first 
signal from a first path operably coupleable to a first polarisation of the antenna arrangement (219) to determine at least one 
pilot signal from said at least one first 
signal; process a coupled amount of at least one second signal from a second path operably coupleable to at least one second polarisation feed of antenna arrangement (219), different to the first polarisation, to determine the at least one 
pilot signal from said at least one second signal; and determine a first 
phase relationship of the same 
pilot signal between the at least two RF paths.