Design of wideband Rotman lenses with dummy ports for wide-scan phases array applications

Microwave Rotman Lenses support wide-angle scanning, wideband, low-phase error, and true time delay (TTD) beam forming. Their performance is ideal for applications such as remotepiloted vehicles, satellites, collision-avoidance radars, and ultra-wideband communications systems. The use of printed circuit technology for Rotman Lenses in recent years has facilitated designing high performance but low profile, and lightweight beam-forming networks (BFNs). In this thesis, wide-band wide-scan phased arrays are investigated by utilizing the beamforming network that is based on a microstrip Rotman Lens. A wide beam scanning capability of ±40o for the frequency range 8-12 GHz is demonstrated. The most crucial part is to design a wide beam scanning Rotman Lens in conjunction with a good impedance matching over the entire frequency band. To do so, a technique is proposed to place the dummy ports between input ports and output ports of Rotman Lens as mutual coupling between ports are reduced significantly which results in improving the performance of Rotman Lens. Three different Rotman Lenses are designed and full wave simulated in CST (EM Simulation Software). One of them is fabricated and tested to verify the simulations. Good agreement between simulation and measured results is achieved. A wide-band Vivaldi phased arrays antenna incorporating the designed Rotman lens is also designed and simulated. Size reduction while maintaining good performance in terms of grating lobes and radiation gain was carried out. The design Rotman-Vivaldi phased array offers a good alternative for achieving both wide scanning angles and wide bandwidth coverage