Electronically scanned millimeter wave antenna using a Rotman lens

Georgia Tech developed a Ka-band (33 to 37 GHz) millimeter wave Rotman lens that is being integrated with a beam switching system and horn array to produce a low cost electronically scanned antenna system. The MMW lens was designed and analyzed by generating various lens configurations as input into a mathematical model. This model uses a contour integral equation formulation to obtain the scattering matrix associated with a particular lens design. The optimized lens configuration was fabricated, and the S-matrix of the device was measured and processed to obtain the beam patterns and insertion loss. Maximum sidelobe levels ⩽-30 dB were achieved by applying an ideal -40 dB Taylor weighting function to the measured data. The measured insertion loss (Taylor weighting loss not included) ranged between 0.8 and 2.3 dB depending on the particular beam port that was excited and the frequency that was used. The lens has 32 active antenna element ports, and 17 active beam ports. Although the maximum scan angle for the present design is only ±22.2 degrees, greater scan angles up to ±45 degrees as well as frequencies up to 95 GHz are possible with different lens designs