Dual-Polarized (CP, LP, and Slant), Series-Fed, Monopulse Planar Array Antenna

Abstract

A single-layered, series-fed monopulse planar array antenna system is presented, which reduces the complexity of corporate-fed monopulse antennas in terms of multilayered structures and number of 180° ring hybrid couplers as monopulse comparator circuit. The proposed antenna exploits only two 3-dB/180° hybrid couplers that results in reduced insertion loss of 3 dB. The proposed X-band monopulse antenna system exhibits the sum ( $\Sigma $ ) patterns with dual (linear, circular, and slant) polarization, difference ( $\Delta $ ) patterns with dual linear polarization, bi-difference patterns with dual (slant and circular) polarization. The prototype of the proposed antenna system has been fabricated using 0.762-mm-thick Rogers 4350B substrate ( ${\varepsilon }_{r} =3.66$ and $\tan \delta =0.0031$ ). The theoretical and experimental results confirm that −10-dB impedance bandwidth (or VSWR <1.92)> $xo\textit {z}$ -plane and yoz-plane in the field-of-view (FOV) of 40° [ $- 20^{\circ } + 20^{\circ }$ ] for all polarizations. To the best of our knowledge, this is first series-fed planar array antenna reported so far for dual-axis monopulse direction finding applications while offering all types of polarizations with reduced number of 180° ring hybrid couplers as monopulse comparator without compromising the radiation performance and electrical size.