Compact SIW-based Phased Array Antenna for X-Band 2-D Tracking Applications

This paper introduces a compact monopulse phased array antenna utilizing substrate-integrated waveguide (SIW) technology for X-band 2-D tracking applications. The entire antenna structure is made up of four subarrays, each containing a pair of SIWs. Each SIW comprises five inclined slots along its central axis, spaced at intervals of λg/2, and is excited in the TE10 mode to produce linear polarization. Each of the four subarrays is driven by a four individual ports. Simultaneous excitation of these subarrays with different phase combinations at the four input ports results in the creation of a sum pattern, as well as E-plane, H-plane, and Bi-plane difference patterns. The antenna offers broadside gain of 16.5 dBi with the sum pattern and null-depth of -30 dB using the difference patterns at a frequency of 8.2 GHz. It also offers an impedance bandwidth of 1.2% and maintains inter-port isolation of over 40 dB across the entire operating band.