Compact Broadband Electromagnetically Coupled Stacked Patch Monopulse Antenna Array at X-Band

This paper presents a compact, broadband, electromagnetically coupled stacked patch monopulse antenna array at X-band. The antenna element consists of a microstrip line, radiating patch, and parasitic patch in three different layers without air-gap. The antenna array is designed within the diameter of 9 λ with the corporate feed network, which aids the sidelobe level of <; -24 dB. The monopulse comparator is designed with a combination of rat-race and double section branch-line hybrids. The impedance bandwidth of the antenna array is 10 % for VSWR <; 2. The measured results show a sum pattern peak gain of 24.5 dBi, beamwidth is about 8 deg. in both E- and H-planes. The difference pattern shows a null-depth of better than -30 dB over the bandwidth with a maximum null-depth of about -48 dB.