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ABSTRACT: A report is presented on the improvement by an optimised hexagonal metallic cavity of the electromagnetic field confinement in a hollow-core resonator based on out-of-plane two-dimensional photonic band-gap crystal cladding. A resonator was constructed with silica rods to prove the concept at frequencies around 30 GHz. It is shown that the technique can reduce the resonator size by 8.1 times without loss in quality.
Electronics Letters 08/2011; · 0.96 Impact Factor
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ABSTRACT: This paper presents the design, the fabrication and the measures of a two-pole tunable band-pass filter. The design filter consists of two microstrip resonators loaded by ferroelectric MIM (Metal-Insulator-Metal) capacitors. The capacitors use the Barium Strontium Titanate (BST) ceramics doped by 1% Manganese. The filter tunes from 385 MHz to 420 MHz under 0-380 V of bias. The insertion loss is -2.9 dB at zero bias (385 MHz) and the return loss is - 11 dB at 420 MHz.
Microwave Conference (EuMC), 2010 European; 10/2010
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ABSTRACT: We developed a novel technique for accurate phase synchronization of microwave oscillators based on sapphire dielectric resonators cooled to liquid nitrogen temperature. The achieved quality of phase synchronization (a few milliradians) enables the accurate measurements of extremely weak phase fluctuations expected from the next generation of ultralow phase noise microwave oscillators.
Review of Scientific Instruments 07/2010; · 1.37 Impact Factor
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ABSTRACT: This paper deals with the microwave study of coplanar tunable capacitors using Mn-doped Ba(0.6)Sr(0.4)TiO(3) ceramics. These ceramics are developed to improve performance at microwave frequencies (i.e., compromise between tuning capabilities and insertion losses). Interdigitated capacitors were first fabricated on thick Mn-doped BST ceramics. The capacitors showed reduced tuning factor because of a parasitic capacitance between the contact pads. The use of Mn-doped BST/ SiO(2) bilayers led to a significant enhancement of the capacitor performance (57% of agility under 200 V at 1 GHz).
IEEE transactions on ultrasonics, ferroelectrics, and frequency control 11/2009; 56(11):2363-9. · 1.80 Impact Factor
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ABSTRACT: This article presents a design methodology for bulk acoustic wave (BAW) filters. First, an overview of BAW physic principles, BAW filter synthesis and MBVD model is addressed. Next, design and optimization methodology is presented and applied to a mixed Ladder-Lattice BAW band pass filter for the UMTS TX-band at 1.95 GHz.
Microwave Conference, 2009. EuMC 2009. European; 11/2009
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ABSTRACT: Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at cryogenics temperatures < 50 K. In both cases persistent photoconductivity was observed after initially exposing semiconductors to white light from a halogen lamp. Photoconductance decay time constants for GaP and GaAs were determined to be 0.900 +/- 0.081 ns and 1.098 +/- 0.063 ns, respectively, using this method. Comment: 13 pages, 5 figures
06/2009;
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ABSTRACT: Whispering Gallery modes in bulk cylindrical Gallium Arsenide and Gallium Phosphide samples have been examined both in darkness and under white light at 50 K. In both samples we observed change in permittivity under light and dark conditions. This results from a change in the polarization state of the semiconductor, which is consistent with a free electron-hole creation/recombination process. The permittivity of the semiconductor is modified by free photocarriers in the surface layers of the sample which is the region sampled by Whispering Gallery modes. Comment: 8 pages, 3 figures
06/2009;
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ABSTRACT: The whispering gallery modes have been used to characterize the effect of the light on gallium arsenide and gallium phosphide placed in darkness at 50 K at frequencies respectively equal to 18.94 GHz and 11.54 GHz. The experiment shows a change in the polarization state of the semiconductor, which is consistent with a free electron-hole creation/recombination process. The permittivity and the loss tangent of the semiconductor are modified by shifting of the free electrons from the valence band to the conduction band.
Frequency Control Symposium, 2009 Joint with the 22nd European Frequency and Time forum. IEEE International; 05/2009
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ABSTRACT: We report on the demonstration of a resonator based on electromagnetic field confinement in a hollow-core by an out-of-plane 2D photonic band-gap (PBG) crystal cladding. The resonator is designed to concentrate the energy within an air region in the center of the resonator and away from the cavity walls to minimize conductor losses. In contrast with in- plane 2D PBG crystal devices, the PBG crystal studied here is perpendicular to the propagation plane. A resonator was constructed with silica rods to prove the concept at frequencies around 30 GHz.
Frequency Control Symposium, 2009 Joint with the 22nd European Frequency and Time forum. IEEE International; 05/2009
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ABSTRACT: Whispering gallery modes in bulk cylindrical gallium arsenide and gallium phosphide samples have been examined both in darkness and under white light at cryogenics temperatures ≤50 K . In both cases persistent photoconductivity was observed after initially exposing semiconductors to white light from a halogen lamp. Photoconductance decay time constants for GaP and GaAs were determined to be 0.900±0.081 and 1.098±0.063 ns , respectively, using this method.
Journal of Applied Physics 01/2009; · 2.17 Impact Factor
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ABSTRACT: This article discusses numerical simulations of thin film bulk acoustic wave resonators. FBAR simulation with 1D analytical model permits to quickly determine resonator layers thicknesses that correspond to the objective resonant frequency. 3D finite elements method permits to investigate the effect of the electrode shape on the spurious modes that are present in the electrical impedance. In order to reduce or to suppress those modes, solutions have to be investigated.
Frequency Control Symposium, 2007 Joint with the 21st European Frequency and Time Forum. IEEE International; 07/2007
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ABSTRACT: A new 2D and 3D software, using the method of line, has been proposed in this paper to analyze planar tunable microwave devices including ferroelectric thin-films. Next, a dynamic characterization method of ferroelectric layers and some first experimental results have been presented.
Ferroelectrics. 06/2007; 353(August 2007):124-131.
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ABSTRACT: This article discusses numerical simulations of thin film bulk acoustic wave resonators. FBAR simulation with 1D analytical model permits to quickly determine resonator layers thickness that correspond to the objective resonant frequency. 3D finite element method permits to investigate the effect of the electrode shape on the spurious modes that are present in the electrical impedance. In order to reduce or to suppress those modes, solutions have to be investigated.
Electronics, Circuits and Systems, 2006. ICECS '06. 13th IEEE International Conference on; 01/2007
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ABSTRACT: We present a method for BAW (bulk acoustic wave) filters computation. This method compares the equivalent impedance of the BUTTERWORTH-VAN DYKE (BVD) model based on an electrical equivalent circuit with the impedance obtained by piezoelectric equations in one dimension for a piezoelectric structure. Using the least squares method, the three elements of the BVD model can be determined as a function of the dimensions and the properties of the piezoelectric resonator. Based on the proposed method, a ladder piezoelectric 7 pole filter can be easily optimized using an electrical synthesis. The frequency of the proposed filter is around 1.84GHz and the band pass close to 100MHz. This method can be used either for FBAR (film bulk acoustic resonator) or SMR (solidly mounted resonator) structure.
Electronics, Circuits and Systems, 2006. ICECS '06. 13th IEEE International Conference on; 01/2007
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ABSTRACT: The characterization of ferroelectric thin-film planar microwave devices using the method of line (MoL) has been summarized in this paper and a method in order to dynamically characterize ferroelectric layers has been proposed. Because the permittivity-dc electric field dependence in ferroelectric materials is used to tune microwave devices, it is necessary to develop a suitable analysis method to accurately characterize ferroelectric materials. First, this paper presents results of 2D and 3D analysis of tunable planar devices and, next, the dynamic characterization of ferroelectric thin-film layers
Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006
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ABSTRACT: An analysis is presented for a room temperature dual-mode oscillator (patent pending) utilising a single sapphire resonator in which two orthogonally polarised whispering gallery modes are excited. The temperature dependence of the 3.39 GHz beat frequency was aned near 304 K. An Allan deviation of 8×10<sup>-12</sup> was measured at 1s.
Electronics Letters 02/2006; · 0.96 Impact Factor
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ABSTRACT: In this paper, we present a method of designing a Bragg reflector structure, using a simple non-Maxwellian model. This allows us to obtain an unloaded Q-factor of 350,000 with a one-layer Bragg reflector resonator at room temperature and at 10GHz, using sapphire (ε<sub>r</sub>=9.394, tanδ=5.9*10<sup>-6</sup>). Also, we noticed that for high permittivity materials the requirement of loss tangent is reduced to obtain the same Q-factor for a lower permittivity material. Finally we report the experimental results on a sapphire with a one-layer-Bragg reflector. The Q-factor of 190,000 was obtained at a frequency of 8.8 GHz.
Microwave Conference, 2005 European; 11/2005
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ABSTRACT: The characterization of ferroelectric thin-film planar microwave devices using the method of Line (MoL) has been summarized in this paper. Because the permittivity-dc electric field dependence in ferroelectric materials is used to tune microwave devices, it is necessary to develop a suitable analysis method to accurately characterize ferroelectric materials. This paper presents first results of 2D analysis of tunable planar devices.
Microwave Conference, 2005 European; 11/2005
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ABSTRACT: Method of lines and finite element analysis investigations have been performed to optimize parameters in a TE/sub 011/ mode cavity resonator suitable for a spaceborne hydrogen maser. We report on designs that were explored to find a global maximum in the important design parameters for the microwave cavity used in a hydrogen maser. The criteria sought in this exercise were both the minimization of the total volume of the cavity and the maximization of the product of the z-component of the magnetic energy filling factor and the cavity TE/sub 011/ mode Q-factor (Q/spl middot//spl eta/). Different configurations were studied. They were a sapphire tube in a copper cylinder, a sapphire tube in a copper cylinder with Bragg reflectors, and spherical copper cavities both empty and sapphire-lined on the inside cavity surface. At 320 K, the simulations resulted in an optimum product Q/spl middot//spl eta/ = 4.9 /spl times/ 10/sup 4/, with an inner cavity radius of 80 mm and unity aspect ratio. This represents a 54% improvement over an earlier design. The expected increase in the product Q/spl middot//spl eta/ with the inclusion of Bragg reflectors to the sapphire tube was not achieved. Moreover, the z-component of the magnetic energy filling factor was greatly reduced due to an increase in the radial magnetic field. The sapphire-lined spherical cavity showed no better performance than an equivalent-sized empty copper spherical cavity. For the empty cavity the simulations resulted in the product Q/spl middot//spl eta/ = 4.4 /spl times/ 10/sup 4/. The empty spherical cavity resonator is not suitable for the spaceborne hydrogen maser as the total volume in this case is 33% larger than that of the optimized sapphire tube resonator.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 11/2005; · 1.69 Impact Factor
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ABSTRACT: A frequency stability analysis of a room temperature frequency-temperature compensated dual-mode resonator oscillator (patent pending) is presented. Using a single crystal cylindrical sapphire resonator, 40 mm in diameter and 20 mm high, two orthogonally polarized whispering gallery modes were simultaneously excited, with the difference frequency temperature dependence aned near 304 K. The standard Allan deviation of the 3.39 GHz beat between the two modes was measured to be approximately 8 × 10<sup>-12</sup> between 1 and 4s.
Frequency Control Symposium and Exposition, 2005. Proceedings of the 2005 IEEE International; 09/2005
