Design and Fabrication of Ultra-Wideband Baluns Embedded in Multilayer Liquid Crystal Polymer Flex

In this paper, we present the design and fabrication of ultra-wideband (UWB) baluns embedded in multilayer liquid crystal polymer (LCP) flex. Fabrication techniques are demonstrated for processing these commercially available LCP thin-films by standard PCB equipments. Variations in the LCP thin-film thickness are characterized and compared before and after lamination. Results show good dimensional stability of the material, a critical factor in controlling the line impedances and performance of the balun. Electrical results of these baluns show bandwidths exceeding 3.1-10.6 GHz with less than 1 dB insertion loss, and amplitude and phase imbalance less than 1.2 dB and 2deg, respectively. These baluns are ideal for applications in UWB communication systems specified by the IEEE 802.15.3a standard.