SBIR-STTR Award

The proposed investigation focuses on the research and development of a fundamentally new, high-speed, radio-frequency (RF) switch. It is designed for frequencies in the range 1-100 GHz. The switch is predicated on thin-film microelectromechanical systems (MEMS) technology with piezoelectric actuation. In general, piezoelectric materials develop strain when an electric field is present, which allows mechanical expansion and contraction of the material to be controlled by an applied voltage. Unlike traditional electrostatic MEMS switches, the closing force between the metal-to-metal contacts can be significantly improved by increasing the bias voltage (electric field strength) across the piezoelectric material. The piezoelectric material lead zirconate titanate (PZT) is employed in the current project. Phase 1 is expected to result in the validation of a sol-gel PZT actuator for use in MEMS RF switches. This research entails the development of a prototype with a standard cantilever design. It is unimorph in nature and utilizes a single layer of PZT; it is activated by piezoelectric strain that is transverse to the imposed electric field (d31). The Phase 1 cantilever will limit the switching time to a few microseconds because of limitations brought about by the mechanical resonance frequency of the cantilever itself. This is done to alleviate the need for a costly mechanical analysis in Phase 1. However, PZT actuators will make new mechanical designs feasible in Phase 2 that will lower the switch time constant into the tens of nanoseconds range (e.g., multi-layer PZT stacks with linear (d33) piezoelectric strain modes).

The proposed investigation focuses on the research and development of a fundamentally new, high-speed, radio-frequency (RF) switch. It is designed for frequencies in the range 1-100 GHz. The switch is predicted on thin-film microelectromechanical systems (MEMS) technology with piezoelectric actuation. In general, piezoelectric materials develop strain when an electric field is present, which allows mechanical expansion and contraction of the material to be controlled by an applied voltage. Unlike traditional electrostatic MEMS switches, the closing force between the metal-to-metal contacts can be significantly improved by increasing the bias voltage (electric field strength) across the piezoelectric material. Because the switch restoring force is large, in-use stiction is greatly mitigated with this architecture. The piezoelectric material lead zirconate titanate (PZT) is used as an actuator in the current project. This makes new mechanical designs feasible. Three strategies are suggested for lowering the switch time constant into the tens of nanoseconds range while preserving other important characteristics of the switch (e.g. high isolation, low resistive losses). These include a bimorph design, piezoelectric extensional bars, and flextensional actuators. Combinations of these strategies are likely to yield a high-performance switch.

Keywords:
MEMS, TRANSMIT-RECEIVE SWITCH, THIN FILMS , RF SWITCH, LEAD ZIRCONATE TITANATE, PIEZOELECTRIC A