Wideband Multimode Filtering Circular Patch Antenna

A wideband circular patch antenna (CPA) is proposed and fabricated in this article. Based on the cavity mode theory of circular patch, four resonant modes of quasi-TM
₀₁
, quasi-TM
₀₂
, quasi-TM
₀₃
, and quasi-TM
₀₄
are merged together to obtain a wide passband through cutting slots and adding short pins on the driven patch. In order to generate low stopband radiation nulls, two circles of defected ground structures (DGSs) are designed. Meanwhile, a stacked patch is added above the driven patch to obtain an upper edge radiation null. The experimental results achieve the 10 dB impedance bandwidth of 30.3% from 5.3 to 7.19 GHz with an overall size of
$1.84\,\,\lambda _{0} \times 1.84\lambda _{0} \times 0.05 \lambda _{0}$
(
$\lambda _{0}$
is the free space wavelength at 6 GHz). Without any extra filtering circuit, the proposed antenna obtains the sharp band edge with a stopband suppression level of 15.7 dB. The out-of-roundness of the radiation pattern in the H-plane is less than 2.7 dB in passband. With good performance in wideband, omnidirectivity, low profile, and high stopband suppression, the proposed antenna has great application prospects in the high-integration microwave systems of large unmanned aerial vehicles.