A 46⋆1 bandwidth ratio balun on multilayer organic substrate

We present the design and fabrication of an ultra-wide bandwidth balun on a multilayer organic Liquid Crystal Polymer substrate. Using a novel U-shaped defected ground structure and a single inductor, the balun achieves a measured insertion loss of less than 1dB and return loss of better than 10dB from 50MHz to more than 3 GHz. Within the measured 46:1 bandwidth ratio from 50MHz to 2.3GHz, the amplitude and phase imbalance are less than 1dB and 8°, respectively. This proposed balun has a compact size of 35mm × 51mm. To our knowledge, the balun has the largest bandwidth ratio reported to date on multilayer printed circuit without ferrites.