Thanks to Professor John Jackson of JR Magnetics for writing in and sharing his design for a 3D printed wideband antenna designed for 50 Ohm 900 MHz to 11 GHz operation.
John required a wideband antenna that could cover the cellphone bands, WiFi, Bluetooth up to 6 GHz and the new USB band from 5 GHz to 10 GHz all in a single antenna installation. He also needed the impedance to be as flat as possible to reduce signal pulse distortion. First he looked into classic discone and sphere antenna designs, but found that while a sphere had the required bandwidth, it did not have the desired impedance characteristics, and a discone had the desired impedance characteristics, but not the ultra wide bandwidth required.
To get around this John combines the sphere and discone designs together to create a sort of icecream with cone looking shape. This results in the ultra wide bandwidth required, and a relatively flat SWR that stays below 2.
The design is easily reproducible by anyone with a metal 3D printer. The antenna's top hemisphere and cone are printed in brass, whilst the radome and supporting structure are printed in plastic.
We have uploaded John's original document here (pdf warning), and display some of the images below. The full build instructions can be found on his website, and John is also selling the 3D printed parts via Shapeways.