Direction finding and target tracking make demanding requirements on the measurement of incoming angles of electromagnetic waves. A monopulse antenna, based on the singular symmetric spoof surface plasmon polariton (SSPP) structure, is proposed for high-accuracy angle sensing. The singular SSPP structure is composed of periodic corrugated grooves for the confinement of the electromagnetic fields. Due to the microstrip–coplanar waveguide transition, the fields along both sides of the SSPP add constructively to form the endfire beam at the sum port and destructively to form the null radiation in the endfire direction at the difference port. An optimization based on the team progress algorithm is adopted to facilitate this antenna design. A prototype is designed and fabricated to validate the design principle, and measured results agree with the simulation. The proposed antenna shows a wide bandwidth ranging from 5.0 GHz to 7.5 GHz for both the sum and difference ports with the return loss greater than 10 dB, realizing a relative bandwidth of 40%. The isolation for the sum and difference ports is higher than 21 dB, and the null depth is larger than 20 dB over the entire operating range, which is favorable for the high accuracy angle sensing and measurement. This monopulse antenna has broad prospect in angle measuring systems such as direction finding and radar tracking scenes.
A Rectangular Waveguide-to-Coplanar Waveguide Transition at D-band Using Wideband Patch Antenna