Right-Angled Microcoaxial Bends for Si-Based RF/Microwave Integrated Circuits.

This paper presents the detailed design, fabrication, and measurement of right-angled microcoaxial bends for silicon (Si)-based radio frequency and microwave integrated circuits. The design of the right-angled microcoaxial bends is performed using the high-frequency structural simulator and the trained artificial neural networks (ANNs) models. The ANN models enable fast and accurate design of microcoaxial bends to achieve desired impedance. The right-angled straight and curved microcoaxial bends are fabricated by a multilayer copper (Cu) Damescene process, which has a low thermal budget and is fully compatible with a complementary metal–oxide–semiconductor back-end-of-line process. Insertion loss less than 0.04 dB at frequency from 0.1 to 40 GHz is realized for both straight and curved bends. The measured return loss is less than −20 dB at frequency from 0.1 to 40 GHz for both microcoaxial bends. The impedance for both microcoaxial bends is well matched to 50 $\Omega $ . Besides the low loss and the high impedance matching, the microcoaxial bends also show other advanced characteristics, including high-quality factors ( $Q$ -factors) as well as supporting pure transverse electromagnetic mode. The use of high-performance bends allows us to fold microcoaxial passive components to meander structures for miniaturization while maintain low loss and perfectly matched impedance. [ABSTRACT FROM PUBLISHER]