Coplanar Waveguide Fed Broadband Circularly Polarized Corner Truncated Slot Antenna

Abstract

Modal analysis based on magnetic dipole theory brings out detailed explanations for broadband circular polarization response which is obtained after truncating corners of rectangle slot antenna. Orthogonal modes are excited by truncating corners of coplanar waveguide fed rectangle slot antenna. Corner truncation excites orthogonal modes along slot diagonals as truncation is at an angle of 45 ⁰ to antenna feed. Magnetic current path length is reduced due to corner truncation length along 45 ⁰ diagonal. This increases corresponding path length of electrical current. Thus increase in electrical current path length results in frequency reduction corresponding to orthogonal mode ⁴⁵ TM 10 . As corners along 135 ⁰ diagonal are not truncated, its magnetic current path length is nearly constant yielding constant frequency of corresponding orthogonal mode ¹³⁵ TM 01 . Further tuning of the truncation length brings down frequency of next orthogonal mode T 11 . This broadens the circular polarization response. Antenna configuration results 47 ^% circularly polarized bandwidth superimposed on 77% of impedance band and both are centered at 1.520 GHz. Over complete circularly polarized response broadside gain of 3 dBi is obtained. It gave right hand circular polarization response along +Z-axis and left hand circular polarization response along -Z-axis. Along +Z-axis, left hand circular polarization component is 13 dB down.