Monolithic IPD-MEMS Technology and Its Applications to High- $Q$ Switched Capacitor Banks and Variable True-Time-Delay Networks

A low-loss monolithic integrated passive device-microelectromechanical systems (IPD-MEMS) technology process on an alumina substrate is proposed. Two applications are investigated both theoretically and experimentally using the proposed IPD-MEMS process: 1) a high-quality-factor switched capacitor bank, and 2) a variable true-time-delay (TTD) network with a fine resolution. The measured IPD-MEMS capacitor bank exhibits a variable capacitance of 0.63-3.8 pF with Q-values between 100 and 300 at 1 GHz. A low-loss highly miniature IPD-MEMS digital delay line, with a delay ranging between 40 and 120 ps, is measured. A maximum 1-dB insertion loss is achieved for this digital TTD network of up to 2 GHz with a footprint of 2 mm × 1.3 mm. To realize a fine delay step resolution, a barium-strontium-titanate varactor is added to this IPD-MEMS digital design. A continuous maximum group delay between 70 and 148 ps with a fine resolution of 0.6 ps is achieved with an overall size of 2.9 mm × 1.6 mm.