Monopulse Antenna in SIW Technology for Beam Steering Applications

Series-fed slot arrays using substrate integrated waveguide (SIW) technology are reported in which the sum and difference patterns are steered to a desired beam angle in the far-field. Applications include radar, localization, and new target detection algorithms where beam steering designs are of interest. In the paper, the design methodology and steering approach for two antenna prototypes is discussed. Initially, simulations and measurements of a single-element antenna for monopulse are described. This planar SIW antenna is matched to 50-Ω and is defined by two-sided, microstrip end-launch feeding. A series-fed array of slots is realized defining a total antenna structure which employs sub-arrays and with two input ports for each sub-array element. Concepts are extended to a 4-port structure, defining a new monopulse array, which offers sum pattern control along with null steering for the monopulse pattern. The simulations and measurements show proof of concept for the developed monopulse antennas at 24 GHz. The design approach is also applicable to other planar antennas and arrays which operate at microwave and millimeter-wave frequencies where pattern maximum and null steering for the sum and difference patterns is of interest.