Wideband 18–40 GHz Surface Micromachined Branchline Quadrature Hybrid

This letter demonstrates two 18-40 GHz rectangular coaxial branchline quadrature hybrids designed using circuit and full-wave simulations. The chosen topologies are fabricated in a surface micromachining technology PolyStrata. Measured in-band performance of baseline wideband branchline hybrid shows |S
₁₁
|<;-10dB, |S
₂₁
| = -4.1 ± 1dB, and |S
₃₁
| = -4.3 ± 0.7 dB. This hybrid is miniaturized by meandering the rectangular coaxial lines to obtain 57% reduction in surface area and in-band performance with |S
₁₁
| <; -10dB, |S
₂₁
|= -4.2±1.2dB, and |S
₃₁
| = -4.1 ± 0.7 dB.