Design of a buried hybrid coupler for wideband applications using LTCC technology

The design of a buried wideband 3 dB hybrid coupler in Low Temperature Co-fired Ceramics (LTCC) technology is presented. The LTCC process used is briefly described and the electromagnetic field simulation-based design is presented. Particular care is placed on the design and optimization of transmission from the buried stripline coupler to coplanar probing pads at the surfaces. Measured results of the fabricated coupler are in good agreement with simulations and show good performance with input matching, an amplitude balance of ±0.5 dB and phase balance of 90±1.5° over a wide frequency band from 3.2 to 5.1 GHz. The dimensions of the fabricated coupler are (3.3 × 6.8 × 2.15mm
³
).