Modified Square Loop Antennas with an Increased Axial-Ratio Bandwidth

Using the method of moments, we analyze two types of loop antennas; they have loop circumferences of
$\boldsymbol{1\lambda}$
and 2λ (
$\lambda$
: wavelength). Each loop is located above a ground plane at height
$\boldsymbol{h}$
, and a 3dB axial-ratio bandwidth versus
$\boldsymbol{h}$
is evaluated. It is found that the
$\boldsymbol{1\lambda}$
and
$\boldsymbol{2\lambda}$
loops have maximum bandwidths of 3% and 2% at
$\boldsymbol{h}=\boldsymbol{0.18\lambda}$
, respectively. Using
$\boldsymbol{1\lambda}$
and
$\boldsymbol{2\lambda}$
loops, we further design a double-loop antenna. It is revealed that the antenna shows a bandwidth of 3%, which is three times as wide as that of a conventional double-loop antenna.