A Dual-Mode SIW Compact Monopulse Comparator for Sum and Difference Multibeam Radar Applications

In this letter, a compact wideband substrate integrated waveguide (SIW) monopulse comparator is proposed. The TE
₁₀
and TE
₂₀
modes of an SIW transmission line are used to generate in-phase and out-of-phase excitation fields for the sum and difference beams without complex phase shift network. The monopulse comparator can realize maximum 0.4-dB amplitude balance, 3.6° phase balance for both sum and difference ports, and −37.0-dB isolation coefficient within the operating bandwidth of 9.43–10.65 GHz. In addition, to integrate the monopulse comparator with a low-cost beam scanning capability, six monopulse comparators are used as the sources to excite a flat Luneburg lens. The experimental result demonstrates that ±58° beam coverage range with around −20.0-dB null depth and 15.0-dBi gain can be realized. The advantages of the proposed monopulse multibeam antenna, including low profile, low cost, wide beam scanning range, and wide operating bandwidth, make it a very promising solution for low-cost monopulse radar systems.