Design of a Compact Circularly Polarized Dual-Mode Monopulse Cavity-Backed Substrate Integrated Waveguide Antenna

A novel compact dual-mode monopulse cavity-backed substrate integrated waveguide (SIW) antenna is proposed. The antenna consists of an array of two circular-polarized cavity-backed SIW antennas, a dual-mode section, and two input ports. TE10 and TE20 modes are excited in the multimode section to produce sum and difference pattern, respectively. A prototype of the proposed monopulse antenna at the center frequency of 10 GHz is manufactured. Measured results show 10-dB return-loss bandwidth of 4.4%, axial-ratio bandwidth of 1.9%, 9.2 dBi gain, and 25 dB null depth. The proposed antenna has good monopulse radiation characteristics and can be easily integrated with planar circuits.