Fully embedded CDMA cellular-band lumped LC-quadrature hybrid coupler into organic package substrate

In this paper, fully embedded lumped LC-quadrature hybrid coupler are designed, fabricated, and characterized into multi-layered organic packaging substrate. This embedded device is comprised of high Q MIM capacitors and circular spiral stacked inductors. For realizing fully embedded high Q capacitor, barium titanate (BaTiO₃) composite high Dk film was utilized. The measured return loss and isolation are better than 25 dB. Measured insertion loss is about 0.38 ~ 0.42 dB at the frequencies ranged from 824 MHz to 894 MHz (CDMA cellular-band). The coupler exhibits a coupling loss of 23.3 ~ 24 dB. The phase difference between through and coupling ports is 1.2 ~ 2.4 degree. It has a size of 2.8 mm times 2.95 mm times 0.66 mm (height), which is the smallest one in the couplers developed onto the package substrate. The measured performance characteristics are well matched with the 3D EM simulated ones.