Capability and manufacturability: Some considerations concerning the current status of multi-filar dielectric loaded antennas

Dielectric-loaded multifilar-helix antennas have been established as a useful means of providing circular polarization in small body-loaded devices. They invoke the principle that resonance-fields balanced across a dielectric medium occupy less volume than they would in equivalent air-loaded antennas. It has also been shown that circular-polarization discrimination is important for accurate position determination using GNSS systems in multi-path environments such as may exist in modern cites. The paper proceeds to analyze the more general benefits of circular-polarization discrimination in respect of the spatial capacity of MIMO systems. Damping of reflections from the device, caused by body-loading, reduces radiation efficiency but has been shown to actually improve circular-polarization discrimination between antennas of this type. Circular/elliptical polarization can be seen as always resulting from superposition of sources of differing static dipole direction and phase separation. Therefore such discrimination presents an opportunity to exploit linear independence of cross-polar summations which occur in close proximity to each other. Finally the paper considers the manufacturability of such antennas and describes some advances that have been made at Maruwa Co Ltd.