Pierre Blondy

Low-loss 2-bit tunable bandpass filters using MEMS DC contact switches

This paper presents the development of tunable filters using ohmic contact microelectromechanical system switches. It is shown that this type of switch is very well suited for the fabrication of low-loss high tuning-range microwave filters. Two sets of tunable Ku-band microstrip filters and resonators have been fabricated, with measured tuning ranges of 20% and 44%, and unloaded quality factors better than 75 in all cases. The 2-bit 5.7% fractional bandwidth, tunable bandpass filters exhibit insertion losses lower than 3.2 dB in all states.

Low loss micromachined filters for millimeter-wave telecommunication systems

This paper describes the design and the realization of two membrane supported microstrip millimeter-wave planar bandpass filters. Both filters exhibit transmission zeros and a 2.3 dB port-to-port insertion loss for the 37 GHz 3.5% bandwidth 2-pole filter and a 1.5 dB insertion loss for a 60 GHz 8% bandwidth 4-pole filter. The use of membrane technology allows a significant reduction of insertion loss, combined with a reproducible, low cost fabrication process.

MEMS switchable interdigital coplanar filter

This paper presents a tunable interdigital coplanar filter with tapped-line feedings. Microelectromechanical systems capacitors are used as a high contrast capacitive switch between a quarter-wavelength resonator and an open-ended stub to perform the frequency shift. A two-pole tunable filter with a 13% relative bandwidth has been designed, fabricated, and measured. The center frequency can be switched from 18.5 to 21.05 GHz with low return losses (less than 15 dB) and low insertion losses (3.5 dB).

Low-loss micromachined filters for millimeter-wave communication systems

This paper describes the design and the realization of two membrane supported microstrip millimeter-wave planar bandpass filters. Both filters exhibit transmission zeros and a 2.3 dB port-to-port insertion loss for the 37 GHz 3.5% bandwidth 2-pole filter and a 1.5 dB insertion loss for a 60 GHz 8% bandwidth 4-pole filter. The use of membrane technology allows a significant reduction of insertion loss, combined with a reproducible, low cost fabrication process.

rf-microwave switches based on reversible semiconductor-metal transition of VO2 thin films synthesized by pulsed-laser deposition

Microwave switching devices based on the semiconductor-metal transition of VO2 thin films were developped on two types of substrates C-plane sapphire and SiO2 / Si, and in both shunt and series configurations. Under thermal activation, the switches achieved up to 30-40 dB average isolation of the radio-frequency rf signal on 500 MHz-35 GHz frequency band with weak insertion losses. These VO2-based switches can be electrically activated with commutation times less than 100 ns, which make them promising candidates for realizing efficient and simple rf switches.

Charging in Dielectricless Capacitive RF-MEMS Switches

This paper presents results on high lifetime RF microelectromechanical (RF-MEMS) dielectricless capacitive switches. Using air gap variation only, these RF MEMS capacitive switches achieve a capacitance ratio of 9, associated with small residual charging. The reliability of the switch has been studied, pull-in and pull-out voltages shifts have been observed, modeled and validated with good agreement between model and measurements for a switch held for one month in the down state. The dependence of charging mechanism to the biasing signal is also presented by applying unipolar and bipolar waveforms with different duty cycles. Charging can be modeled using a simple Curie-Von Schweidler equation. It is shown that the duty cycle of the bias signal is strongly accelerating switch failure, and that using bipolar signals improves the lifetime of these switches by several orders of magnitude. The projected lifetime of current RF-MEMS dielectricless switches held in the down state using bipolar signals is several tens of years.

Dielectric less capacitive MEMS switches

This paper presents the fabrication and experimental results on a capacitive switch without dielectric. Using an appropriate design of the switch, acceptable performances have been obtained with Con/Coff ratio around 10. The key advantage of this switch is that dielectric charge trapping related failure modes are eliminated. An example is shown with measured intrinsic loss less than 0.3 dB at 15 GHz and isolation better than 15 dB at the same frequency.

Bandwidth and central frequency control on tunable bandpass filter by using MEMS cantilevers

This paper deals with a tunable bandpass filter topology which controls independently and simultaneously both the central frequency and bandwidth. This tunable filter results from the association of MEMS cantilevers, used as variable capacitors, with an original passive topology. The latter is based on dual behavior resonators (DBRs), each of them is constituted of low- and high-frequency open-ended stubs. The associated filter electrical response is characterized by tunable frequency transmission zeros. A millimeter bandpass filter with central frequency and relative bandwidth tunability of about 10 and 75%, respectively, is presented.

Voltage and current-activated metal-insulator transition in VO2-based electrical switches : a lifetime operation analysis

Abstract Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal–insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal–insulator transition in VO2 thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO2 switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO2-based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO2-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.

Sub-Microsecond RF MEMS Switched Capacitors

This paper presents fast switching RF microelectromechanical systems (MEMS) capacitors with measured switching times between 150-400 ns. By introducing bent sides on a planar microbeam, it is shown experimentally that the resonance frequency of aluminum bridges is increased by a factor of 25 compared to standard RF MEMS components. In addition, this original shape can be implemented easily in post-processing of complementary metal-oxide-semiconductor circuits. Several designs are presented with measured mechanical resonance frequencies between 1-3 MHz and measured switching times under 400 ns. Using this original approach, sub-microsecond RF MEMS switched capacitors have been designed and fabricated on quartz substrate. Their resulting RF performance is presented with a measured capacitance ratio of 2.3. Reliability tests have also been performed and have demonstrated no significant mechanical behavior variation over 14 billion cycles and a moderate sensitivity to temperature variation.