  Manipulating the excitation of resonant electric and magnetic multipole
moments in structured dielectric media has unlocked many sophisticated
electromagnetic functionalities. This article demonstrates the experimental
realization of a broadband Huygens' source. This Huygens' source consists of a
spherical particle that exhibits a well-defined forward-scattering pattern
across more than an octave-spanning spectral band at GHz frequencies, where the
scattering in the entire backward hemisphere is suppressed. Two different
low-index nonmagnetic spheres are studied that differ in their permittivity.
This causes them to offer a different shape for the forward-scattering pattern.
The theoretical understanding of this broadband feature is based on the
approximate equality of the resonant electric and magnetic multipole moments in
both amplitude and phase in low permittivity spheres. This is a key condition
to approximate the electromagnetic duality symmetry which, together with the
spherical symmetry, suppresses the backscattering. With such a configuration,
broadband Huygens' sources can be designed even if magnetic materials are
unavailable. This article provides guidelines for designing broadband Huygens'
sources using low-index spheres that could be valuable to a plethora of
applications.
