A Fractal Monopole Antenna With Dual Polarization Reconfigurable Characteristics for X-Band Applications

A monopole antenna with dual (linear/circular) polarization reconfigurability for X-band applications is presented in this paper. The antenna consists of a bent arm cross-shaped (BACS) slot created on the inverted triangular staircase fractal (ITSF) shaped patch. Two PIN diodes are embedded on the opposite side of the horizontal arm of the BACS slot for electronic switching between two different polarization states. By varying the biasing conditions of PIN diodes, the measured antenna’s 3 dB axial ratio (AR) operational band for left-hand circular polarization (LHCP) is observed from 9.88 GHz to 11.06 GHz, whereas linear polarization (LP) is achieved from 7.95 GHz to 12.64 GHz. The measured peak gain of the antenna is 5.71 dBi, whereas the average peak gain is obtained as 4.97 dBi. The size of the antenna is
$1.57\mathrm {\lambda }_{\mathrm {g}}\times 1.25\mathrm {\lambda }_{\mathrm {g}}$
where,
$\mathrm {\lambda }_{\mathrm {g}}$
is guided wavelength at the lowest cutoff frequency, 7.95 GHz. The proposed monopole antenna’s progressive design steps, an equivalent lumped circuit model analysis, and a comparative study between electromagnetic (EM) simulation and measured results are carried out to validate the antenna’s performance.