Alexandru Takacs

Microwave Power Harvesting for Satellite Health Monitoring

This paper addresses the microwave energy harvesting on board of geostationary satellites for health satellite monitoring. To prove the feasibility of such a concept, we investigated the electromagnetic environment existing on antenna panels. Based on established cartographic maps, three designs of rectennas are proposed. Measured dc powers ranging from 0.256 to 1.28 mW can be harvested for electric field levels ranging from 91 to 121 V/m and by using very simple and compact designs. The harvesting structures consist of only one Schottky diode per rectenna and present a total surface of 2.4 cm 2. They are suitable for powering the new generation of ultra-low power transceivers, thus enabling autonomous wireless power networks for satellite health monitoring.

Tunable Bandstop and Bandpass MEMS Filters for Millimeter Wave Applications

This paper addresses the design and modeling of millimeter wave tunable filters using CoPlanar Waveguide (CPW) quarter wavelength stubs and MEMS (Micro-Electro-Mechanical-Systems) switches. In order to design bandstop and bandpass tunable MEMS filters an accurate design methodology based on the transmission line theory is presented. The tunable behavior is achieved using original MEMS switches: Two Cantilever Shunt Switch (TCSS). The overall structures, including TCSS, have been manufactured using dielectric membrane, in order to minimize the insertion losses. The obtained simulation and experimental results confirm the accuracy of the proposed design methodology and indicates very good performances in millimeter wave band.

Tunable MEMS Filters for Millimeter Wave Applications

This paper addresses the design and the realization of millimeter wave tunable filters using MEMS (micro-electro-mechanical-systems) technology. In order to design hands top tunable MEMS filters two new topologies are presented. The tunable behavior is achieved using MEMS switches. These switches, based on original topology of two cantilever shunt switch, have a typical shunt switch behavior and low actuation voltage. The overall structures are manufactured using dielectric membrane

New topologies of tunable bandstop MEMS filters for millimeter wave applications

This paper addresses the design and the realization of tunable bandstop filters using MEMS (micro-electro-mechanical-Systems) technology for millimeter wave applications. In order to design bandstop tunable MEMS filters, three new topologies are presented. The presented measurement and simulation results validate the proposed topologies. The tunable behavior is achieved using MEMS switches. These switches, based on original topology of two cantilever shunt switch (TCSS), have a typical shunt switch behavior and intrinsic low actuation voltage. The overall structures, including TCSS, have been manufactured using dielectric membrane, in order to minimize the insertion losses.

Compact Lumped Elements Micromachined Band-Pass Filters with Discrete Switching for 1.8/5.2 GHZ Applications

This paper presents the design, fabrication and first experimental results of a dual-band switchable band-pass filter structure for the selection of DCS 1800 and WLAN standards. The design approach makes use of intensive electromagnetic modelling and layout optimisation. The fabrication technology is based on bulk and surface silicon micromachining to manufacture lumped elements on high resistivity silicon bulk and dielectric membrane. Filter test structures were fabricated and their frequency responses are presented

160 GHz silicon micromachined folded slot antenna array

This paper describes the design, electromagnetic (EM) modeling and experimental results obtained for a 160 GHz double folded slot antenna array processed through silicon micromachining. Initial simulations showed reflection losses (RL) of -17 dB at 160 GHz and a fractional bandwidth of ~18.7% (with RL<;-10dB between 148.65 GHz and 178.59 GHz). The simulated directivity was larger than 4 dBi in the working frequency band and ~6.8 dBi at 160 GHz. The structure was processed through deep reactive ion etching (DRIE), and resulted in a thinner substrate than designed. The experimental results for this thinner substrate of about 140 μm showed a ultra wideband behavior, with measured RL<;-10dB for almost the whole 140-210 GHz band and -17 dB at 160 GHz. The free space transmission parameter was measured and the results were compared with the simulated directivity showing a frequency shift of the curve, but otherwise a very good agreement in the trend of the two curves.

Miniaturization of Compact Quadrifilar Helix Antennas for Telemetry, Tracking and Command Applications

This paper addresses the miniaturization of Quadrifilar Helix Antennas (QHAs) for space applications (VHF Telemetry, Tracking and Command). Several shape miniaturization techniques were presented, and the impact of height reduction is quantified in terms of radiation pattern, gain and phase center. Simulated and experimental results demonstrate that Compact Quadrifilar Helix Antennas (CQHAs) with a height reduced up to 70% reported to the reference QHA can be designed. By using an appropriate optimization method, the impact of the miniaturization on CQHA performances in terms of radiation pattern and polarization purity can be minimized. Moreover, the impact on the gain is quantified, and design rules are reported. Finally a closed-form expression for estimating the gain of CQHAs from the height reduction factor is found.

Micromachined front-end for 60 GHz applications

In this paper we present the electromagnetic modeling, fabrication and experimental results of a on-chip 2×1 folded slot dipole antenna array manufactured through silicon micromachining, working in the 60 GHz band. The measurements are in very good agreement with the simulations and demonstrate a large working band of ~20% (54-65 GHz) for a return loss better than 10 dB.

A Methodology to Study the Electromagnetic Behavior of a Cryogenic Metallic System Used to Control the Ratchet Effect

We introduce an electromagnetic investigation of the complex experimental setup used in studying the Ratchet Efiect at low temperature. This investigation, based on intensive electromagnetic simulations, shows that a compromise has to be taken into consideration between the physical aspects, the technological and the practical restrictions as well as the electromagnetic conditions of the observed phenomenon. By improving the electromagnetic response of the whole system, the Ratchet induced photovoltage can be increased, and hence the Ratchet device can be used for practical applications in wireless communications.

On layout optimization of the microwave diplexor filter using genetic algorithms

An original application of genetics algorithms in the on layout optimization of the microwave filters is presented. Based on a resonant coupling irises topology, a Ka-band diplexor filter on silicon membrane substrate is tuned in order to improve its performances. The optimization process uses the numerical results given by Sonnet software and the overall process is piloted by a genetic algorithm. A very good acknowledgment between numerical (optimized) and experimental results was obtained.