Andrew Malczewski

Lifetime characterization of capacitive RF MEMS switches

The first experimental characterization of dielectric charging within capacitive RF MEMS switches has been demonstrated. Standard devices have been inserted into a time domain setup and their lifetimes have been characterized as a function of actuation voltage. Switch lifetimes were measured using a dual-pulse waveform with 30 to 65 V of actuation voltage. Resulting lifetimes were between 10/sup 4/ and 10/sup 8/ switch actuations, demonstrating an exponential relationship between lifetime and actuation voltage.

X-band RF MEMS phase shifters for phased array applications

In this work, development of a low-loss radio frequency (RF) microelectromechanical (MEMS) 4-bit X-band monolithic phase shifter is presented. These microstrip circuits are fabricated on 0.021-in-thick high-resistivity silicon and are based on a reflection topology using 3-dB Lange couplers. The average insertion loss of the circuit is 1.4 dB with the return loss >11 dB at 8 GHz. To the best of our knowledge, this is a lowest reported loss for X-band phase shifter and promises to greatly reduce the cost of designing and building phase arrays.

RF MEMs Variable Capacitors for Tunable Filters

() ABSTRACT: An RF MEMs microelectromechanical system variable capacitor has been demonstrated with a 22:1 tuning range, tuning from 1.5 to 33.2 pF of capacitance. This capacitor was constructed using bistable MEMs membrane capacitors with individual tuning ranges of 70:1 to 100:1, control voltages in the 30-55 V range, switching speeds less than 10 mS, and operating frequencies as high as 40 GHz. These devices may eventually provide a viable alternative to electronic varactors with improved tuning range and lower loss. Q 1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 362)374, 1999.

Ka-band RF MEMS phase shifters

As the need for low-loss phase shifters increases, so does the interest in radio frequency (RF) MEMS as a solution to provide them. In this paper, progress in building low loss Ka-band phase shifters using RF MEMS capacitive switches is demonstrated. Using a switched transmission line 4-bit resonant phase shifter, an average insertion loss of 2.25 dB was obtained with better than 15-dB return loss, a similar 3-bit phase shifter produced an average insertion loss of 1.7 dB with better than 13-dB return loss. Both devices had a phase error of less than 13/spl deg/ in the fundamental states. To our knowledge, these devices represent the lowest loss Ka-band phase shifters reported to date.

Impact of Humidity on Dielectric Charging in RF MEMS Capacitive Switches

A novel technique is used to distinguish the charging of the surface from that of the bulk of the dielectrics of different types of RF MEMS capacitive switches under different electric fields and humidity levels. In general, bulk charging dominates in dry air, while surface charging increases linearly with increasing humidity. Under comparable electric fields and humidity levels, switches made of silicon dioxide are less susceptible to surface charging than switches made of silicon nitride. These quantitative results not only underscore the importance of packaging the switches in a dry ambient atmosphere, but also validate the novel technique for evaluating the effectiveness of dielectric preparation and packaging.

Effect of packaging on dielectric charging in RF MEMS capacitive switches

A novel technique was used to evaluate the effectiveness of packaging in maintaining a dry ambient atmosphere for electrostatically actuated RF MEMS capacitive switches and in preventing the charging of the dielectric surface after prolonged operation. It was found that as-packaged switches exhibited different degrees of surface charging, probably due to different amounts of moisture inadvertently sealed in the essentially hermetic packages. However, after the switches were delidded and baked dry, all switches showed minimum surface charging. The results imply that the switches can have consistently long lifetimes by improving the yield of the packaging process.