F. Huret

Multimode TRL. A new concept in microwave measurements: theory and experimental verification

An original multimode thru-reflection line (TRL) algorithm is used to derive the generalized scattering parameters of multimode two-port networks. Theoretical developments are detailed for calibration procedures based on two ports as well as multiple-port vector network analyzer (VNA) measurements. First-run experimental results demonstrate the validity of this technique. This method allows the experimental characterization of multiconductor transmission-line devices. It could also be used to characterize power coupling to undesired modes in monolithic microwave integrated circuit (MMIC) structures using conductor-backed coplanar waveguides.

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.

Patch antenna adjustable in frequency using liquid crystal

The topic considered here is the design, achievement and test of a liquid crystal-based patch antenna. This device was realised in planar technology with low-cost foam substrate. Liquid crystal dielectric anisotropy permits frequency agility. Owing to technological difficulties of the foam, we used this dielectric property to adjust the shift of the antenna resonance frequency whenever required. The comparison of simulation and measurement data evidenced that frequency can be adjusted.

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

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.

Improvement of an inverted microstrip line-based microwave tunable phase-shifter using liquid crystal

This paper deals with the study of electrically tunable phase-shifters based on the use of liquid crystals. First, the dielectric characterization of the commercial liquid crystal involved in our investigations allowed us to determine its dielectric anisotropy. Secondly, two phase-shifter configurations were studied. Both structures propose inverted microstrip line with coplanar accesses, but they are based on a different design of the transmission line. The measurements carried out with the first one evidenced an efficient phase shift. The second one showed considerable improvement in performances.

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.

Additivity of capacitive and inductive coupling in submicronic interconnects

Constant evolution in integrated circuit technology has led to an increase in the switching speed of the digital chip. As a result, there is a growing interest in the inductance associated with signal lines. Inductive coupling effects on interconnects is an emerging concern in high performance digital integrated circuits. Based on an RLC transmission line model, associated to each propagation mode, a new crosstalk noise model is proposed to evaluate both the capacitive and the inductive coupling. The additivity of the coupling is shown and validated with several simulations

Liquid Crystal Tunable Filter Based On DBR Topology

The use of liquid crystals for tunable devices has already been investigated for phase-shifters and antennas in planar technology. Here, the focus is, first, on a half-wavelength open-circuited stub resonator, then on a second-order dual behavior resonator filter. To have the benefit of liquid crystal anisotropy and thus obtain agility, a bias voltage is applied to the device under study. In order to avoid the shift observed between simulated and measured results of the half-wavelength open-circuited stub for the first structure, the technological process has been improved for the second one in the aim to reduce mismatching and LC leaking