A Modified-square Slot Antenna with Circular Polarization
Characteristics for Military Band Applications
Madhuri Sahal, Dinesh Yadav, Deepak Bhatnagar, and Manish Tiwari
In this work, the design and performance of a circu-
larly polarized (CP) antenna designed using characteristic modal
analysis (CMA) for military band application is presented. The
substrate used is single-sided glass-reinforced epoxy and the an-
tenna dimensions are 37×37×1.6 mm 3 . The antenna is compact,
low-profile, circular polarized having an ARBW of around 500
MHz (center frequency 4.6 GHz). A coplanar waveguide (CPW)
fed monopole antenna is used for excitation of the modified-square
slot antenna that incorporates quarter section of circular symmet-
rical patches on the four corners. A stub orthogonal to the CPW
fed monopole capacitively tunes the low Q mode as identified by
CMA technique to shift to a lower frequency to create degenerate
modes in military band for circular polarization generation. The
3-dB AR bandwidth of the antenna is in the frequency range 4.43-
4.9 GHz and measured value of impedance bandwidth is 3.33 GHz.
The fractional ARBW and impedance BW are 10.07 % and 61.6 %
respectively. The peak antenna gain in the CP frequency band is
3.75 dBic. The proposed antenna exhibits good polarization purity,
the minimum axial ratio is 1.38 at 4.6 GHz. The broad circular
polarized antenna is suited for military applications covering the
frequency range 4.43-4.9 GHz.