Left: Ka primary feed with internal septum polariser. Ka band hybrid tee with internal matching vanes, for monopulse applications.Right: Ku primary feed with dual mode waveguide bend.
The lens antenna's gain and radiation patterns were measured using the near field range at the University of Northumbria.
Near field scanner and lens antenna Measured patterns (Ka band)
The performance was found to be very good at Ku band, with a gain of about 35 dBi at 12 GHz. To my knowledge, this is superior to any other antenna which can be accommodated inside the same headroom, which here is set by the lens height - just 220 mm. Also, unlike phased array antennas for satcoms-on-the-move, the lens exhibits almost no scan loss over the intended range of elevation angles of 20º to 50º. (At higher angles the waveguide increases the overall antenna height by about another 50 mm.)At Ka band, this prototype functioned quite well but did exhibit significant dielectric loss which reduced the aperture efficiency to less than 50%. Should this development ever be resurrected I would concentrate efforts on finding materials of better purity. These effects, and a fuller presentation of measurement results are found in the journal article noted above (International Journal of RF and Microwave Computer Aided Engineering, January 2017).A pragmatic way of showing the antenna work with a live satellite broadcast - plug it into a satellite TV receiver and compare with a dish.Spectrum analysis.This noisy looking plot is more informative than you might at first think. The 25 MHz wide blocks are broadcasts from satellite co-polarised transponders. Spectrum is re-used on the orthogonal polarisation, using a shifted set of frequency blocks which are centred at the nulls seen above. Poor cross-polar discrimination in the antenna would smear out these nulls and degrade signal quality.