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A diversity antenna combining four inverted-F antennas (IFAs) is evaluated for UHF RF identification (RFID) readers. Polarisation and pattern diversities are obtained for a sequentially rotated configuration of the IFAs. Mutual coupling between ports is minimised by etching quarter-wavelength slots into the ground plane. The resulting envelope correlation coefficient is less than 0.003 in the working band. A switching diversity scheme is then applied to evaluate the tags readability in a lab environment. It is shown that the antenna diversity enhances the reading range compared to a circularly or a linearly polarised antenna of the same size.

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International audienceWireless Underground Sensor Networks (WUSN) consists of buried sensors nodes which are expected to communicate through the soil. The significantly high attenuation caused by the soil properties is the main challenge for their feasibility. This challenge is accentuated with Impulse Radio Ultra-Wide Band (IR-UWB) WUSN because of the very low transmitted power. This paper first studies the impact of the soil on performances of a new small UWB buried antenna and then analyzes the effect of soil properties on the communication link from underground to aboveground. This study includes the effect of soil moisture, burial depth and frequency. Measurements are achieved in a sample of soil composed of standard pebbles used in railway (railroad ballast). The simulations and measurements results show that with short distances and low soil moisture underground to aboveground UWB communication is possibl

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A new procedure to measure the apparent reflection coefficient of differential patch antennas at 60 GHz is described. The measurement method makes use of two WR15/microstrip-line (MSL) transitions which are simple to realise. The experimental results are compared with simulated results. This comparison emphasises the limited effect of transition losses on measurement accuracy.