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This paper presents a compact single-layer UWB antenna based on a coplanar waveguide structure. The antenna operates within bandwidth from 3 to 10.6 GHz (111.76%). The antenna incorporates two notch-filters, designed to mitigate possible interference with WiMAX and WLAN. This filtering function can be switched on or off, independently for each band, by using pin diodes. This feature allows fast adaptation, supporting spectrum sharing solutions with a compact and planar antenna. The simulated and measured results of the proposed antenna are in good agreement, with the maximum antenna gains dropping after activation of the filtering from 2.5 to −10 dBi in WiMAX 3.5 GHz band and from 3 to −8 dBi in WLAN 5 GHz band. K E Y W O R D S CPW-feed, notch band, PIN diode, reconfiguration, UWB monopole antenna

This paper introduces an original strategy to step up the capacity of ambient RF energy harvesters. The low rectification efficiency that comes from weak input power is enhanced through high gain antenna arrays that push the circuit to operate in a more efficient state. The prototype uses beam forming networks to build up a wide coverage since ambient energy can come from any direction, or the orientation of the rectenna may be unknown. By extending the operating range of rectifiers to higher input powers, the system operates as a very efficient narrow beam rectenna or as a synthetic high gain isotropic rectenna. The rectification efficiency pattern of one multi-beam rectenna, functioning in the 2.4 GHz band, is plotted and compared to a dipole rectenna's pattern. For a low incident power density of 4.10-5 mW.cm-2 , the rectification efficiency is largely improved in any direction : from 2.6% with a dipole rectenna up to 14%. Index Terms-Beam forming network (BSN), miniaturized Butler matrix, multiple beam antenna array, rectifier, high gain isotropic rectenna, efficiency pattern, RF energy harvesting.

This paper presents a miniaturized microstrip antenna on an air-filled paper substrate. The presence of air in the substrate accounts for low dielectric losses and a high dielectric thickness, resulting in a high radiation efficiency and a large bandwidth. In addition, the edge of the antenna is exploited to feed the antenna with a coplanar line that can be connected to a 50 coaxial probe. This original feeding technique permits the reduction of the frequency of resonance as the air gap increases. The antenna is further miniaturized with the insertion of a slot in the ground plane. As a result, a high degree of miniaturization can be obtained along with a high efficiency. The influence of the air gap and of the slot on the antenna's performances is investigated. Two prototypes with dimensions of 0.29 x 0.29 x 0.065 radiating at 2.45 GHz are fabricated with copper tape and silver ink and the antennas' performances are experimentally validated: a gain of 4.5 dBi and a front-to-back ratio of 9.5 dB are measured, corresponding to a radiation efficiency of 70%.

This paper presents a modular and reconfigurable rectenna unitcell (RU) made up of an antenna, a rectifier and radiofrequency (RF) power combiners intended to form a scalable and adaptative beam-forming network, for autonomous passive tracking or RFID monitoring applications. The reconfigurable rectenna unitcell allows a dual mode operation thanks to both RF and DC possible combinations of multiple rectenna unitcells. On the one hand, the passive beam-forming operation, coming from the RF combination of multiple rectenna unitcells provides oriented communication or localization capabilities. On the other hand, the series DC connection of RF isolated rectenna unitcells delivers DC power to the system with high output voltage under low RF power densities. Prototypes of 4-edges rectenna unitcells are designed in the 2.4 GHz band. The operation of one individual RU is demonstrated, and it is shown that multiple RUs are suitable for RF energy harvesting, multiple-tag communication and tag localization.