A Printed Wide-Slot Antenna With a Modified L-Shaped Microstrip Line for Wideband Applications

A printed wide-slot antenna for wideband applications is proposed and experimentally investigated in this communication. A modified L-shaped microstrip line is used to excite the square slot. It consists of a horizontal line, a square patch, and a vertical line. For comparison, a simple L-shaped feed structure with the same line width is used as a reference geometry. The reference antenna exhibits dual resonance (lower resonant frequency
f
₁
, upper resonant frequency
f
₂
). When the square patch is embedded in the middle of the L-shaped line,
f
₁
decreases,
f
₂
remains unchanged, and a new resonance mode is formed between
f
₁
and
f
₂
. Moreover, if the size of the square patch is increased, an additional (fourth) resonance mode is formed above
f
₂
. Thus, the bandwidth of a slot antenna is easily enhanced. The measured results indicate that this structure possesses a wide impedance bandwidth of 118.4%, which is nearly three times that of the reference antenna. Also, a stable radiation pattern is observed inside the operating bandwidth. The gain variation is found to be less than 1.7 dB.