Microstrip Hybrid Corporate-Series Feed Network for Low Sidelobe Monopulse Antenna Arrays

This paper presents a microstrip-based hybrid corporate-series feed network to realize low sidelobe levels for monopulse antenna arrays with circular symmetry. The central elements of the array are corporate fed by replicating 2×2 subarray and the remaining edge elements are series fed by taking feed points from the non-radiating edge of the preceding antenna elements. This novel feed network is implemented to design a linearly polarized, broadband, stacked patch monopulse antenna array at X-band. The sidelobe level of the antenna array is −24 dB. The diameter of the antenna array is 9λ. The impedance bandwidth of the antenna array is 10% for VSWR < 2. Rat-race hybrid-based comparator has been implemented for the monopulse operation of the antenna. The measured results show a sum pattern peak gain of 24 dBi with the gain variation of 1.5 dB over 10% impedance bandwidth, beamwidth is about 8 deg. in both E- and H-planes. The difference patterns show a null-depth of better than −30 dB over the bandwidth with a maximum null-depth of about −50 dB.