Design and analysis of microstrip line rotman lenses

We simulate and compare three different Rotman lenses, under the beam excitation from the outermost input port, with the help of FEM method. Preliminary results suggest that for a large lens, eta = 0.65 , with a scan angle of 45deg, the microstrip Rotman lens with the focal ratio suggested by [1], g = (l+alpha²)/2, has a better performance than other designs with smaller focal ratio when uniform amplitude and linear phase variation is desired. Detail investigations will be conducted to compare the pros and cons of each design.