Miniaturization of Rotman Lens Using Array Port Extension

This letter proposes a miniaturization design of Rotman lens using array port extension technique. The array ports of the proposed 4 × 12 Rotman lens are extended from an initial 4 × 7 Rotman lens through a port extension (PE) network to achieve a smaller equivalent lens body. The initial Rotman lens and the topology for the PE network are designed based on the analysis of phase distributions along the extended array ports when different beam ports are excited. The proposed design allows all the beam pointing angles to be consistent before and after extension at center frequency. A prototype working at X-band was fabricated. The measured results show that all beam ports are matched well, and high isolations between beam ports are achieved from 8 to 12 GHz. The Rotman lens provides a ±29° scanning range with four uniformly distributed beams at 10 GHz. The beam pointing angles remain relatively stable within 20% frequency bandwidth, with the maximum angle distortion of ±3°.