Semiconductor technologies enable the fabrication of microelectromechanical-systems (MEMS) components for use as high-frequency oscillators and components with changing modes, such as switches and phase shifters. To investigate the potential of MEMS technology for terahertz applications, researchers from the KTH Royal Institute of Technology in Stockholm and the California Institute of Technology in Pasadena, Calif., integrated a submillimeter-wave, 3.3-b MEMS phase shifter in micromachined waveguide for use from 500 to 550 GHz.
The component was created by loading micromachined rectangular waveguide with nine E-plane stubs. The phase shifter uses reconfigurable MEMS surfaces to block or unblock the E-plane stubs from the waveguide as well as achieve the different phase states.
The component provides a linear phase shift of 20 deg. in 10 discrete steps (3.3 b). It features only 3 dB or less insertion loss from 500 to 550 GHz, with at most 1.5 dB attributed to the MEMS surfaces. Most of the insertion loss was traced to misalignment and mechanical manufacturing errors with the micromachined chips and the waveguide surfaces. The MEMS chips were fabricated on SOI wafers and deep-reactive-ion-etching (DRIE) process techniques. Simulations were performed with CST Microwave Studio simulation software from CST, and measurements were made using a PNA-X VNA system with waveguide frequency extenders from Agilent Technologies (now Keysight Technologies). The results were closely matched for phase shifts from 0 to 90 deg. in 10 steps across a frequency range of 500 to 600 GHz.
See “Submillimeter-Wave 3.3-bit RF MEMS Phase Shifter Integrated in Micromachined Waveguide, ” IEEE Transactions on Terahertz Science and Technology, Vol. 6, No. 5, September, 2016, p. 706.