Metallic Wideband Dual-Polarized 2-D Monopulse Array Antenna Based on Dual-Mode Composite Waveguides

This paper presents a wideband dual-polarized 2-D monopulse array antenna (MAA) based on dual-mode composite waveguides (DMCWs). The proposed antenna consists of an 8 × 8-element dual-polarized array and a dual-mode monopulse comparator. The monopulse comparator is constructed from proposing dual-mode 3-dB couplers, 90° phase shifters, and mode separators, all based on composite dual-mode structure of rectangular waveguide (RW) and coaxial line. The radiating part of the dual-polarized array includes square slots, cross-shaped slots, and new T-shaped orthomode transducers (OMTs), generating stable dual-polarized boresight radiation without grating lobes across the operating frequency band. To reduce the occupied size (meeting the scalability of the array), another type of compact DMCW based on double-ridge waveguide (DRW) and coaxial line is used to implements a compact wideband full-corporate feeding network. Benefiting from the DMCW-based feeding network and monopulse comparator, the whole MAA significantly reduces structural complexity and profile height. Experimental results show that the fabricated prototype has stable sum-beam radiation for both polarizations within the frequency range of 14 to 18 GHz. The null depth of the difference-beam is less than -36 dB, and the amplitude difference is less than 0.5 dB.