A Low-Loss 3-dB Coupler Using Metal-Integrated Suspended Line

This paper proposed a novel 3-dB coupler with low loss based on metal-integrated suspended line (MISL) platform. By using metal-integrated technology, most of the electric field is distributed in the air cavity, which can effectively reduce the dielectric loss and improve the performance of the whole circuit. Multi-section slot-coupled structure is used to achieve wideband operation. From 2.4 GHz to 7.25 GHz, i.e. a 100.5% fractional bandwidth, the measured amplitude imbalance and phase imbalance are less than 1.2 dB and 2.8° respectively, and the measured insertion loss (including connectors and transitions) is around 0.57 dB at the center frequency of 4.8 GHz. Based on the multi-layer MISL platform, the proposed 3-dB coupler also has the advantages of self-packaging.