Dimitrios Peroulis

Design of reconfigurable slot antennas

In this paper the design of a compact, efficient and electronically tunable antenna is presented. A single-fed resonant slot loaded with a series of PIN diode switches constitute the fundamental structure of the antenna. The antenna tuning is realized by changing its effective electrical length, which is controlled by the bias voltages of the solid state shunt switches along the slot antenna. Although the design is based on a resonant configuration, an effective bandwidth of 1.7:1 is obtained through this tuning without requiring a reconfigurable matching network. Four resonant frequencies from 540-890 MHz are selected in this bandwidth and very good matching is achieved for all resonant frequencies. Theoretical and experimental behavior of the antenna parameters is presented and it is demonstrated that the radiation pattern, efficiency and polarization state of the antenna remain essentially unaffected by the frequency tuning

Electromechanical considerations in developing low-voltage RF MEMS switches

This paper reports on the design, fabrication, and testing of a low-actuation voltage Microelectromechanical systems (MEMS) switch for high-frequency applications. The mechanical design of low spring-constant folded-suspension beams is presented first, and switches using these beams are demonstrated with measured actuation voltages of as low as 6 V. Furthermore, common nonidealities such as residual in-plane and gradient stress, as well as down-state stiction problems are addressed, and possible solutions are discussed. Finally, both experimental and theoretical data for the dynamic behavior of these devices are presented. The results of this paper clearly underline the need of an integrated design approach for the development of ultra low-voltage RF MEMS switches.

Tunable lumped components with applications to reconfigurable MEMS filters

This paper presents a novel design scheme for tunable coplanar waveguide components with applications to compact lumped-element MEMS reconfigurable filters. Shunt MEMS switches are employed for tuning the values of lumped components frequently encountered in microwave integrated circuits. In particular, shunt capacitors, series inductors and shunt inductive stubs are the main tunable circuit elements utilized in this work. Furthermore, accurate equivalent circuits that include the most important parasitics introduced by the tuning mechanism are provided. Finally, the proposed method is applied to the design and implementation of very compact low-pass and bandpass tunable filters. The very high tunability range, the compactness of the resulting networks and their very wideband response constitute the main advantages of this technique.

RF MEMS switches with enhanced power-handling capabilities

This paper reports on the experimental and theoretical characterization of RF microelectromechanical systems (MEMS) switches for high-power applications. First, we investigate the problem of self-actuation due to high RF power and we demonstrate switches that do not self-actuate or catastrophically fail with a measured RF power of up to 5.5 W. Second, the problem of switch stiction to the down state as a function of the applied RF power is also theoretically and experimentally studied. Finally, a novel switch design with a top electrode is introduced and its advantages related to RF power-handling capabilities are presented. By applying this technology, we demonstrate hot-switching measurements with a maximum power of 0.8 W. Our results, backed by theory and measurements, illustrate that careful design can significantly improve the power-handling capabilities of RF MEMS switches.

Low contact resistance series MEMS switches

This paper reports on the design and development of a novel DC-contact MEMS switch for microwave applications. The switching operation utilizes two different forces: electrostatic and stress-induced forces. The former is employed as the actuation force, while the latter is responsible for achieving the actual DC contact. In particular, when no bias voltage is applied, the deformation of a metallic cantilever beam caused by residual gradient stress leads to a metal-to-metal contact. On the other hand, when a DC-voltage is applied between the cantilever beam and an actuation electrode, the cantilever deflects due to electrostatic force and the metallic contact ceases to exist. Contact resistance of less than 1 /spl Omega/ is demonstrated with this technique in the closed position, which corresponds to an RF insertion loss of 0.1-0.2 dB up to 40 GHz. In this switch the contact force does not depend on the actuation voltage and there is no DC potential across the closed contact, which constitute the main advantages of this design.

A MEMS reconfigurable matching network for a class AB amplifier

This letter presents the design of a reconfigurable amplifier with an adaptive matching network implemented by shunt MEMS switches. In particular, the MEMS switches are used as capacitive stubs in double-stub matching circuit designs. The effective capacitance of the switches can be varied by switch activation which results in a change of the matching configuration. The RF response of the adaptive matching network is studied and the power performance of the amplifier is presented.

Electrostatically-tunable analog RF MEMS varactors with measured capacitance range of 300%

This paper reports on the design, fabrication, and testing of a novel analog MEMS varactor with measured tuning range of 300%. The proposed electrostatically actuated varactor is based on a parallel-plate approach and is best suited for microwave/millimeter-wave applications. The measured capacitance values are in the range of 40-160 fF and are achieved with DC voltages of 20-34 V. The proposed varactor has the additional advantages of very high resonant frequency (its series measured parasitic inductance is 9 pH) and high quality factor (higher than 80 at 40 GHz).

MEMS single-pole double-throw (SPDT) X and K-band switching circuits

Single-pole double-throw (SPDT) X and K-band circuit designs incorporating low-loss microelectromechanical shunt capacitive switches are reported. The switches incorporate highly inductive connecting beams which aid in further increasing the isolation at the desired operational RF frequency. Measurements show an isolation of better than 40 dB at both 7 and 20 GHz. Insertion loss was measured at -0.95 dB at 7 GHz and -0.69 dB at 20 GHz for the two respective designs.

A planar VHF reconfigurable slot antenna

This paper presents a novel electronically tunable slot antenna. The design is based on a resonant slot structure loaded with a series of PIN diode switches. The tuning of the operating frequency is realized by varying the electrical length of the antenna, which is controlled by the DC bias voltages of the switches. The fabricated antenna is capable of resonating at four different frequencies ranging from 550 to 900 MHz. Very good matching is achieved for all resonant frequencies without the need for any special matching network. Additionally, it is demonstrated that the radiation pattern, efficiency and polarization remain essentially unaffected by the frequency tuning.

Silicon Micromachined Packages for RF MEMS Switches

MEMS technology has major applications in developing smaller, faster and less energy consuming devices provided that reliability of packaging/interconnect technology is sufficiently addressed. This paper presents a low cost, on-wafer, silicon micromachined packaging scheme for RF MEMS switches having excellent electrical performance in K-band. In particular, the package demonstrates an insertion loss of 0.1dB and a return loss of 32dB at 20 GHz. The package is fabricated in parallel with the MEMS switch on the same wafer and therefore requires no lossy solder bumps or bond wires to achieve signal propagation.