Gérard Tanné

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).

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.

Correlation between magnetic properties of layered ferromagnetic/dielectric material and tunable microwave device applications

Layered dielectric / ferromagnetic materials are extensively explored for microwave applications. Indeed, these materials combine the large saturation magnetization of ferromagnetic material with the low loss of dielectrics. Here, our aim was to integrate a layered ferromagnetic composite in a microwave propagation structure since the main advantage of such a material is the large impedance for one polarization. Thus, in order to predict the transmission response of the device, we carried out an electromagnetic analysis to determine how the field pattern of a microstrip line and the microwave-induced demagnetizing fields disturb the material behavior. We also explored the use of the propagation structure in two dc magnetic field-dependent devices: a tunable band stop filter and a magnetic switch. The stop-band function presented a large tunability of more than 50% with a minimal insertion loss of 3 dB when 250 Oe field was applied. Moreover, a magnetic switch using a dc field perpendicular to the easy axi...

Reconfigurable Planar SIW Cavity Resonator and Filter

A new reconfigurable frequency cavity compatible with planar technology has been designed, manufactured and measured. An original tuning solution is proposed, based upon the insertion of vertical capacitive posts integrated within SIW cavities. One extremity of each post is connected to a floating metallic ring, located on the substrate supporting the SIW cavity. The frequency agility is obtained once the metallic ring is connected to the ground plane by short-circuited the corresponding annular slot using surface actuators. Such combination of volumetric cavity and planar activation leads to reconfigurable filters with high Q values and simplified tuning control conditions

Tuneable microstrip device controlled by a weak magnetic field using ferromagnetic laminations

The properties of lamellar insulator ferromagnetic on the edge (LIFE) material in a microwave device under a static field are studied. The LIFE composite is manufactured by gluing sheets of a ferromagnetic thin film deposited by physical vapor deposition on a polymeric substrate. The 0.154-μm-thick ferromagnetic material is an amorphous CoNiZr alloy deposited on a 12.7-μm-thick kapton film. According to gyromagnetic model, when an external static field is applied along the easy axis, the gyromagnetic resonance frequency is shifted towards high frequencies. Then, a piece of LIFE composite was integrated in a microstrip line, using a substrate of low permittivity. The displacement of the minimum of the transmission coefficient in the microstrip line due to a static field applied is presented. The operation of a microwave filter with a stopband tuneable in the 2–6 GHz range by a small static magnetic field (<500 Oe) is demonstrated, as well as a magnetic switch.

KTa/sub 0.6/Nb/sub 0.4/O/sub 3/ ferroelectric thin film behavior at microwave frequencies for tunable applications

In this study about the relationships between structural and microwave electrical properties of KTa1-xNbxO3 (KTN) ferroelectric materials, a KTN thin film was deposited on different substrates to investigate how KTN growth affects the microwave behavior. Interdigital capacitors and stubs were made on these films through a simple engraving process. Microwave measurements under a static electric field showed the importance of the substrate on the circuit behavior and, notably, on the tuning factor

Ferromagnetic composite-based and magnetically-tunable microwave devices

This article deals with a new generation of tunable microwave devices using ferromagnetic materials. The sensitivity of the device cut-off frequency to the dc magnetic field was investigated for two filtering resonators (stub resonator and Stepped Impedance Resonator). The stub resonator exhibited a frequency tunability of nearly 40% for a dc magnetic field strength of 250 Oe, whereas the linewidth remained unchanged. A 12.2% tunability of the SIR device was reached under 250 Oe applied.

Highly tunable microwave stub resonator on ferroelectric KTa0.5Nb0.5O3 thin film

A coplanar waveguide (CPW) stub resonator has been fabricated on a pulsed-laser deposited KTa(0.5)Nb(0.5)O(3) (KTN) thin film (600 nm-thick) onto a r-plane sapphire substrate. It was designed to operate at 10 GHz when the applied bias voltage is zero. We show experimentally that the resonance frequency is shifted by 44% under a 70 kV/cm DC applied electric field. In addition, the dielectric characteristics of the KTN film have been assessed through post-processed measurements of CPW 50-Omega transmission lines using the conformal mapping method.

Ferroelectric Thin Films for Applications in High Frequency Range

Abstract SrBi 2 Nb 2 O 9 and KTa 1− x Nb x O 3 thin films were grown by pulsed laser deposition on various substrates. Structural investigations evidenced that single phase polycrystalline randomly oriented films were grown on sintered alumina whereas epitaxial films were grown on (100)MgO. The microstructure was strongly controlled by the structural characteristics. Interdigited capacitors patterned on SrBi 2 Nb 2 O 9 films on both substrates as well as permittivity and losses measurements performed at 12.5 GHz showed a strong effect of the structural characteristics on the dielectric behavior.

KTN Dielectric Properties at Microwave Frequencies: Substrate Influence

To determine the dielectric properties of ferroelectric thin-films over a wide range of frequencies we developed a simple and efficient method based on the measurement of coplanar waveguide realized on ferroelectric/dielectric heterostructures by using a Spectral Domain Approach. We applied this method to KTa 1−x Nb x O 3 (KTN) thin-films deposited on different substrates. The strong differences observed in the dielectric behavior of KTNs according to the growth substrate suggest that it is affected not only via the resulting microstructure, but also by the induced strains. Accuracy of the method was estimated to 15 and 10% on permittivity and loss tangent, respectively.