Miniaturized T-DMB Antenna With a Low–Loss Ni–Mn–Co Ferrite for Mobile Handset Applications

In this paper, a low–loss Ni–Mn–Co ferrite (Ni
$_{0.76}$
Mn
$_{0.24-}$

$_x$
Co
$_x$
Fe
$_2$
O
$_4$
with x = 0–0.04) has been developed for miniaturization and performance improvement of mobile handset antennas. The developed ferrite material has almost equal permittivity and permeability of 7–9, as well as sufficiently low dielectric and magnetic loss tangent less than 0.001 and 0.01 below 200 MHz, respectively. Miniaturization factor of about 8 and normalized impedance of about 1 were obtained at 200 MHz. A helical antenna operating at terrestrial digital multimedia broadcasting (T-DMB, 174–216 MHz) band was fabricated on the ferrite substrate, which has compact size, low loss, wide bandwidth, and good radiation performance.