Miniaturized Microstrip Antenna Designed by Loading Dual Intersected F-Slots

A miniaturized microstrip antenna (MSA) is designed by loading dual intersected F-slots on the patch. Compared with the simple meandered (dual-I-slotted) MSA, the dual F-slots enable the patch with a lengthened current path, leading to a much reduced resonant frequency. The compacting effect is numerically demonstrated using a patch of 20mm×20mm and substrate with ε
r
= 2.2. It is found that the conventional MSA resonates at 4.42GHz (the guided-wavelength λ
g
= 45.8mm) and the dual-I-slotted MSA resonates at 3.515GHz (λ
g
= 57.5mm). However, the dual-F-slotted MSA is with a downshifted resonant frequency of 2.548GHz (λ
g
= 79.4mm). Hence their electrical lengths are 0.437λ
g
, 0.347λ
g
, and 0.252λ
g
, respectively, among which the last dual-F-slotted MSA is the smallest. In addition, the dual-F-slotted MSA has a gain of 5.99dBi and efficiency of 84.5% in the numerical calculations.