Compact SIW-based Feeding Network for S-band Monopulse Antenna

One of the key components in tracking system is the antenna. Monopulse antennas frequently used in tracking system provide high accuracy and efficiency in determining the range and position of the target due to the utilization of two beams, namely, sum and difference. A hybrid junction is one type of four-port network coupler widely applied in feeding networks for providing sum and diff channels. This paper deals with the development of substrate integrated waveguide (SIW) based feeding network for S-band monopulse antenna. The use of SIW aims to overcome the bulky structure of the conventional metallic waveguide and the complex integration in a finite space. The proposed SIWbased feeding network which operates at S-band frequency is implemented using a 1.524 mm thin Rogers RO-4003C dielectric substrate. The characterization result shows that the SIW-based feeding network can achieve less than -10 dB isolation, with insertion loss about -3.99 dB, return loss less than -10 dB, and phase difference around 180 degrees. The close match between the results enables the proposed SIW-based feeding network to be applied for the desired application in tracking system.