Help, please, somebody, by what principle are under construc

Hi,
help, please, somebody, by what principle are under construction low-profile ultra-wide-band antennas? Sometimes such antennas are used in panoramic receivers, scanners. They have width of a passband from 10:1 and more, and rather low efficiency - less-10-15dbi. If there are references or links about these , please reply.

antp

I don’t know what is exactly your application, but one of the most known wide-band antennas is Discone Antenna (do a google for this name)
Can cover from tens of MHz to a few GHz.