Compact high-Q, low-loss mmW transmission lines and power splitters in RF CMOS technology

A set of slow-wave transmission lines designed in the BiCMOS9-MW technology from STMicroelectronics is characterized up to 110 GHz. State-of-the-art measured quality factors are obtained: 40 at 60 GHz, and more than 50 at 90 GHz. These transmission lines are also quite compact, thanks to a high effective relative permittivity, from 8 to 15 for a characteristic impedance, respectively between 70 Ω and 30 Ω. Based on these results, two power dividers using these slow-wave transmission lines are designed at millimeter-wave frequencies (77 GHz and 94 GHz). The measured S parameters present insertion loss lower than -3.5 dB and return loss better than -20 dB, at the operating frequency. Moreover the use of slow-wave transmission lines leads to a miniaturization of 70 % compared to a classical power splitter designed with microstrip or CPW transmission lines.