Broadband Loaded Cylindrical Monopole Antenna

International audienceAhstract-A broadband printed monopole antenna based on the variation of the conductivity along its length is proposed .. The result indicates that a non-monotonous repartition provides interesting performances in terms of impedance bandwidth but also concerning antenna gain. The achievement of the method is demonstrated through its application, using the carbon fibers to perform this conductivity variation. Monopole antenna presents a large impedance bandwidth of 123% with an interesting gain. Measurement and simulation present a good agreement. I. I N T R O D U C T I O N With the rapid development of communication standards, wide band antennas are needed. Several authors have suggested widening monopole antenna bandwidth by resistive loading continually [1,2]. This kind of resistive distribution leads to a very wide bandwidth but damages significantly antenna gain and its efficiency becomes very low. Antenna characteristics could be improved by modifying the resistive profile. In this paper, we propose to use a variable conductivity along the antenna length applying an optimized profile which gives a broadband impedance bandwidth, a stable radiation pattern, a stable gain level over a large bandwidth especially in the horizontal plane and a higher radiation efficiency. The values of conductivity used is achieved by using various materials such as copper and specially carbon fibers fo r which we can easily tune its conductivity by modifying the concentration of carbon nanofibers [3]. The main aim is to find a compromise between a large impedance bandwidth at -5 dB of reflection coefficient and a good efficiency. So, a new broadband monopole antenna is presented working in the VHF-UHF band. Simulation results and measurements are presented in order to illustrate the characteristics of the proposed antenna

Compact Antenna Array of Superdirective Elements

International audience—In this letter, we investigate using a two-element parasitic (loaded) superdirective antenna as a unit-element to achieve a compact 3D array. Four elements of a planar parasitic superdirective antenna are integrated in a compact 2 × 2 array for UHF band. The array final dimensions are 200 × 200 × 70mm 3 (0.58λ × 0.58λ × 0.2λ), and it presents a maximum simulated total directivity of 11.4dBi. The antenna dimensions are significantly smaller than classical commercial arrays achieving the same directivity. The measured results are in a good agreement with the simulated ones

Small 3D Array Design Using Superdirective Antennas

International audienceIn this paper, we present a compact broadside superdirective antenna array based on a planar parasitic su-perdirective unit-element. The array is designed for 905M Hz frequency band, its dimensions are 200 × 54 × 24mm 3 (0.6λ × 0.16λ × 0.07λ), and it presents a directivity of 9.2dBi and radiation efficiency of 8.3%. Integrating the initial parasitic array in a PCB of 110 × 70mm 2 , the array total dimensions are 200 × 110 × 70mm 3 (0.58λ × 0.32λ × 0.2λ), and it presents a directivity of 9.8dBi and radiation efficiency of 64%

Antenne Triplaque Omnidirectionnelle

Le développement de la technologie Ultra Large Bande (ULB) doit s'accompagner de la mise au point de nouvelles antennes capables de fonctionner classiquement sur la plage de fréquence 3.1 – 10.6 GHz tout en présentant un comportement temporel adéquat à la transmission de pulses courts. Une structure proposée ici est l'antenne large fente triplaque possédant une alimentation en forme de fourche, étudiée avec et sans plan de masse. Cette dernière offre une adaptation de 123 % avec une bonne stabilité de rayonnement (bi-directionnalité dans le plan E et omni-directionnalité dans le plan H). L'utilisation de diagrammes de rayonnement 2D en amplitude et en phase en fonction de la fréquence ainsi que l'analyse du pulse émis par cette structure permettent de mettre en évidence ses caractéristiques de rayonnement temporel. L'antenne triplaque est capable de transmettre une impulsion brève sans apporter de distorsion

Accuracy of Singularity Expansion Method in Time and Frequency Domains to Characterize Antennas in Presence of Noise

International audienceIn this paper, the accuracy of the singularity expansion method (SEM) used for antenna characterization is investigated. A well-known limitation of the SEM is that pole extraction is very sensitive to noise. A comparison between two main methods of pole extraction is presented. The matrix pencil (MP) method and the Cauchy's method are used to extract poles from the radiated fields of a dipole antenna and two bowtie antennas. Results are presented for simulated fields, and the robustness to a white Gaussian noise is also analyzed. We show that the MP method allows working with lower SNR than Cauchy's method and is more accurate for field reconstruction

Window increasing technique to discriminate mathematical and physical resonant poles extracted from antenna response

International audienceThis letter presents a new approach called window increasing technique (WIT) to discriminate mathematical and physical poles extracted from a noisy antenna response. The principle of the WIT is to apply a pole extraction method on several windows of the response and then to observe the stability of the extracted poles. In order to compare the WIT to the classical window moving technique (WMT), we apply these two techniques on the electric far field backscattered by a dipole antenna. We show that, in presence of noise, the WIT allows finding more physical poles with a good accuracy than the WMT

Asymmetrical stripline based method for retrieving the electromagnetic properties of metamaterials

International audienceAn experimental characterization technique for determining the electromagnetic properties of metamaterials in the microwave frequency band is presented. The method consists in measuring the S-parameters of an asymmetrical stripline partially filled with the sample to be characterized. For retrieving the characteristic parameters, two different approaches based on quasi-static approximations are compared. This measurement cell allows an "in situ" characterization because it reproduces the electromagnetic environment frequently found in planar technologies for microwave applications of metamaterials. The whole sample is uniformly excited in magnitude and direction by the interacting electromagnetic field which guarantees representativeness of extracted permittivity and permeability and avoids possible inconsistencies due to anisotropy and heterogeneity of metamaterials

Miniaturized and Reconfigurable Notch Antennas Using a BST Thin Film Varactor

International audienceFerroelectric (FE) thin film varactor technology can be used for antenna miniaturization and reconfiguration. We present more particularly a quarter wavelength notch antenna with a Barium Strontium Titanate (Ba(1-x)SrxTiO3, BST) thin film in MIM geometry. Integration of the BST varactor yields a size reduction of approximately 56% with respect to the initial antenna size (0.064 0 without BST layer) and the miniaturized antenna is tunable from 0.94 GHz to 1.07 GHz

Miniaturized and Reconfigurable Notch Antennas Using a BST Thin Film Varactor

International audienceFerroelectric (FE) thin film varactor technology can be used for antenna miniaturization and reconfiguration. We present more particularly a quarter wavelength notch antenna with a Barium Strontium Titanate (Ba(1-x)SrxTiO3, BST) thin film in MIM geometry. Integration of the BST varactor yields a size reduction of approximately 56% with respect to the initial antenna size (0.064 0 without BST layer) and the miniaturized antenna is tunable from 0.94 GHz to 1.07 GHz

Ferroelectric tunability: from characterization to telecomunication application

4International audienceAdvanced dielectric spectroscopy enables studying of the ferroelectric complex permittivity. Interpretation with the hyperbolic law provides a better fundamental understanding of the material's tunability: bulk contribution, domain wall vibration and displacements may be discerned. Applications, like mobile telecommunication terminals may profit for the design of miniaturized and tunable antennas. As an example, conception and realization of a notch slot antenna with an integrated ferroelectric thin film varactor is presented