Remote, non-contact, radio frequency phase contrast detection using CWDM and directly modulated VCSELs

Microwave imaging techniques using centimetre wavelengths gives benefits of low cost and high penetration coupled with low RF exposure. Non-contact methods such as that described here give the advantage that the antenna design procedure does not have to compensate for the electromagnetic properties of the medium under investigation. Surrounding material does not degrade the accuracy of the phase contrast based measurement technique described. The measurement system was complemented by the development of a Coarse Wavelength Division Multiplexed (CWDM) optical transmission system enabling remote operation over 1km. This technique achieves improved directional isolation over the previously reported reflective optical method. Target identification down to 5mm with sub-mm resolution was achieved at just 5 GHz carrier frequency.