Rotman lens in the microwave and millimeter frequency range

Applications in radar systems and communications systems require very often antennas with beam steering or multi beam capabilities. For the millimeter frequency range Rotman lenses can be useful as multiple beam forming networks for linear antennas providing the advantage of broadband performance. For microwave bands lens design is predominantly performed in stripline or microstrip technology to meet the requirements for compact low weight and low costs systems. In the mm-wave range however a parallel plate cavity forming the lens with waveguide ports arranged around the contour is more appropriate to avoid increasing losses with decreasing operating wavelengths. This attempt aims to realize a Rotman lens for the W-Band. The main problem for a usable lens design in this frequency range is the unavailability of a low loss cable technology. Based on this restriction, designs were tested which use rectangular waveguides. The design and development of Rotman lens at 94 GHz feeding an antenna array for beam steering applications is presented. Experimental results are compared with theoretical considerations and electromagnetic simulations.