Polarization Reconfigurable, Single-Layer, 2-D, Monopulse Array Antenna With Compact Comparator Circuit

A single layered, planar array antenna is presented, aiming to replace the complex geometry of monopulse comparator circuits which are used in conventional corporate-fed monopulse antenna systems for direction-finding applications. This work investigates a new configuration of corporate-fed patch array antenna, in order to reduce the insertion loss of monopulse comparator circuit while utilizing only two 3 dB/180° hybrid couplers as monopulse comparator network. This antenna exhibits the sum ( $\Sigma $ ) pattern with dual (linear, slant and circular) polarization whereas the difference ( $\Delta $ ) patterns exhibit dual-linear polarization, without compromising the radiation performance and electrical size. The proposed monopulse comparator configuration leads to reduced insertion loss of only 3 dB. The measured peak gain is recorded to be 8.5 dBi at 10.04 GHz with minimum null-depth of -18 dB for the difference-patterns. The overall size of the antenna system is only $1.93\mathrm {\lambda }_{\mathrm {o}} \times 2.26\mathrm {\lambda }_{\mathrm {o}} \times 0.0254\mathrm {\lambda }_{\mathrm {o}}$ making the proposed single-layered structure a potential candidate for un-ambiguous, dual-axis monopulse direction-finding and polarimetric radar applications.