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

A single-layered, series-fed monopulse planar array antenna system is presented which reduces the complexity of corporate-fed monopulse antennas in terms of multi-layered structures and number of 180° ring hybrid couplers as monopulse comparator circuit.The proposed antenna exploits only two 3dB/180° hybrid couplers that results in reduced insertion loss of 3 dB.The proposed X-band monopulse antenna system exhibits the sum (Σ) patterns with dual (linear, circular and slant) polarization, difference (Δ) patterns with dual linear polarization, bidifference 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 ( = 3.66 and tanδ = 0.0031).Theoretical and experimental results confirm that -10dB impedance bandwidth (or VSWR < 1.92) is recorded to be 190 MHz (9.56 GHz -9.75 GHz) for sum-ports and 460 MHz (9.94 GHz -10.4 GHz) for differenceports with maximum null depth over -33 dB.The proposed antenna system presents a peak sum gain of 10.57 dBi, 3-dB axial-ratio (AR) bandwidth greater than 160 MHz and root-mean-square-error (RMSE) less than 9° for both xoz-plane and yoz-plane in the field-of-view (FOV) of 40° [-20° +20°] for all polarizations.To the best of authors' 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 comparators without compromising the radiation performance and electrical size.