Compact Dielectric Resonator Antenna With Improved Bandwidth via Loading of Metal Ring

In this paper, a novel dielectric resonator antenna (DRA) characterized by a compact size and wide bandwidth is proposed. The achievement of wideband performance involves the introduction of a metallic ring structure inside the dielectric resonato, ensuring that the antenna’s volume remains compact. Fundamental and higher-order modes,
${\text{TM}}_{01\delta} $
,
${\mathrm{ TM}}_{021+\delta }$
of the cylinder DRA are first investigated by using E-field distribution analysis, and it is found that these two modes are hard to resonate in proximity to each other. Therefore, a thin metal ring, acting as a perturbation structure is inserted into the DR to perturb the E-field of the higher-order mode and reduce its resonant frequency. Consequently, the resonant frequency of the
${\mathrm{ TM}}_{021+\delta }$
mode is significantly decreased, with only a slight effect on the
${\mathrm{ TM}}_{01\delta }$
mode. The resonant frequencies of the three resonances, i.e.,
${\text{TM}}_01\delta $
,
${\mathrm{ TM}}_{021+\delta }$
and probe-mode, are moved in proximity to achieve a wide impedance bandwidth. For experimental validation, a prototype is fabricated and tested. The measured results show the proposed antenna achieves a bandwidth of 51.1% with a low profile of
$0.156\lambda _{c}$
, where
$\lambda _{c}$
represents the wavelength at the center frequency. With these advantages, the proposed design is well-suited for mounting on vehicle platforms, particularly for 4G (2.6 GHz) and 5G (3.5 GHz) communications.