Monopulse RLSA antenna based on a gap waveguide Butler matrix with a feeding cavity at 94 GHz

The purpose of this work is to design a monopulse Radial Line Slot Array (RLSA) antenna to be used for a space debris detector radar. This work is part of a bigger project, financed by Madrid government, to manufacture a complete RADAR for this application. This paper deals with the design of a circular polarized Radial Line Slot Antenna for this purpose: the slots are placed in concentric rings. The length and position of each slot is optimized using a global optimization algorithm where the analysis is based on an in-house Method of Moment algorithm. The second part of the design is the monopulse feed. This is based on a multimode cavity excited by a Butler matrix for simultaneous Σ and Δ operation. The cavity is located below the ground plane of the RLSA and is coupled to the antenna by means of a circular slot and is implemented using gap-waveguide technology. Simulations show good matching and stable Σ and Δ patterns for the monopulse operation.