An Analog RF MEMS Slotline True-Time-Delay Phase Shifter

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> An analog RF microelectromechanical systems (MEMS) slotline true-time-delay (TTD) phase shifter is presented for use in conjunction with tapered slot antennas, such as the Vivaldi aerial and the double exponentially tapered slot antenna. The design is a scalable distributed loaded-line cascade of 62 novel differential slow-wave unit cells. Each differential slow-wave unit cell comprises an electrically short slotline section, which is loaded with a shunt impedance consisting of two center-pulled contactless fixedfixed beam RF MEMS varactors in series, sharing a common electrode. The analog RF MEMS slotline TTD phase shifter is demonstrated on a borosilicate glass wafer using a microfabrication process requiring six masks. It is designed for transistortransistor logic bias voltage levels and exhibits a measured phase shift of 28.2$^{\circ}/{\hbox{dB}}$ (7.8 ps/dB) and 59.2$^{\circ}/{\hbox{cm}}$ at 10 GHz, maintaining a 75-$\Omega$ differential impedance match $(S_{11_{dd}}&lt;-15.8\ {\hbox{dB}})$ . The input third-order intercept point is 5 dBm at 10 GHz for a $\Delta{ f}$ of 50 kHz, measured in a 100-$\Omega$ differential transmission line system. Design and fabrication opportunities, concerning distortion and loss reduction, as well as packaging, are highlighted. </para>