Miniaturized 180$^{\circ}$ Hybrid Coupler in LTCC for L-Band Applications

In this letter, the lumped element technique is used to design a 180 ° hybrid coupler or balun for applications at L1 band. The material system employed is low temperature co-fired ceramic (LTCC), which allows for three-dimensional passive integration. The proposed balun uses a modified equivalent circuit that permits the simultaneous optimization of amplitude and phase balances. A process for the quick tuning of the balun design parameters is also presented. Measurements at 1.575 GHz indicate insertion losses below 0.67 dB, an amplitude imbalance of 0.14 dB, and a phase difference of 179.1 °. To the author's best knowledge, this is the smallest and best performing lumped element balun for applications at L1 band.