High-temperature superconducting beam forming network for communication system applications

This paper presents an application of the high-temperature superconductor (HTS) technology to the development of a high-performance antenna beam forming network (BFN) for communication systems. Design and measurements are made in Ku-band with a multiple power divider technique involving a cascade of 3-dB branch-line couplers. Three microstrip couplers are integrated to form a one-to-four BFN. An experimental prototype is fabricated with TlBaCaCuO thin film deposited onto LaAlO/sub 3/ substrate. Power handling capability of related HTS components such as line, bend, and BFN are also studied together with third-order intermodulation characteristics. It is shown that theoretical prediction is consistent with experimental results, presenting insertion loss of the four output ports ranging from 6.1-6.4 dB and return loss better than 14 dB at 11.95 GHz. These preliminary results demonstrate the potential of extending such a power divider technique in designing an N-port BFN. It is also indicated that the proposed HTS BFN scheme can offer advantages compared to its conventional counterpart, namely, a significant reduction in size/weight and low power loss.