RF MEMS switches and phase shifters for three-dimensional MMIC phased array antenna systems

In order to incorporate the RF MEMS technology with the 3D MMICs technology, a novel RF MEMS switch was designed and implemented in a 3D MMIC circuit environment. RF MEMS switches possess many advantages compared to traditional solid-state switches, such as high electromechanical isolation, and ultra-low power consumption. The novelty of this switch was that it was based on low temperature processing techniques. Design equations for a shielded coplanar waveguide were derived for the switch. Traditional lumped element capacitor model and this newly developed distributed transmission line models were compared against measured data to verify their validity. While measurement results show good agreement with both models, the distributed model consistently demonstrated better match than its lumped element counterpart. Test and measurement results showed that a typical RF MEMS switch was capable of delivering less than 0.2dB insertion loss and more than 14.1 dB isolation between input and output ports at X-band (8GHz–12GHz). This RF MEMS switch required only 12V actuation voltage while it was capable of handling 2.88W RF power before “hot-switching” occurs. Hysteretic phenomenon of RF MEMS switches was observed; release voltage threshold was found to be around 2V∼4V, much lower than the one required for pulling down the structure. Switching speeds of RF MEMS switches with different beam strength were measured using a novel experimental setup utilizing couplers as bias networks. The fastest switches demonstrated maximum switching speed of 3.571 kHz and more than 10,800,000 life cycles.; As the application of RF MEMS switches, a 4-bit digital phase shifter was designed and fabricated. 180° bit and 90° bits were realized using reflection type phase shifters, while the 45° and 22.5° bits were achieved using loaded-line type phase shifters. A novel reflection type phase shifter loaded with multiple switch pairs was developed and was capable of delivering multiple phase shift angles within one circuit stage. Phase shifter measurement results were consistent with simulated results.