Hybrid coding techniques have been proposed recently to improve the coding capacity of chipless RF identification (RFID) tag. This paper examines the possibility to code information thanks to the magnitude level of the radar cross section (RCS) in addition to the more classical technique of frequency position (FP). Single-layer tags based on C-folded dipoles are designed to have different magnitude levels. A magnitude span of up to 15.2 dB is obtained for coupled resonators. A magnitude resolution of 3.5 dB is evaluated for practical applications based on the measurement of the realized tags in different configurations. The problem of tags applied to an unknown object is considered and a compensation technique is proposed for an object similar to a thin dielectric plate.

Bessel beams are proposed as a practical way to generate well collimated and confined beams at mm-waves or THz for quasi-optical applications. To achieve that, we propose the use of two-dimensional antenna arrays as realizable launchers. Truncated Bessel beams with a main lobe width of few wavelengths (λ) can propagate over several hundreds of λ if the antenna aperture is electrically large. Because such a large aperture would require a large number of antenna elements, sub-sampling distributions are proposed in this work. It is found that arrays with spacings of approximately 4λ generate high quality beams with very low amplitude oscillations over distances of about 300λ in vacuum. The optimal excitation function for such arrays greatly departs from the Bessel one. It is synthesized with an analytical method based on a least mean square error minimization. The synthesis method is scalar, but the pseudo-Bessel beams obtained are vectorial and linearly polarized. Theoretical predictions are confirmed by full-wave simulations using Ansoft Designer.

An RFID-compatible focused circular phase-array antenna working at 5.8 GHz is proposed, which is theoretically analyzed and experimentally demonstrated. It consists of 24 half-wavelength dipole antennas placed on three circles. Using only two phase-shifters, a tunable focal spot in the range of 0.4-1 m (10λ) is obtained. The antenna system is analyzed using the Huygens-Fresnel theory, which is compared to the experimental results. At a focal distance of 0.9 m, the measured beam width and focal depth are given by 0.75λ and 5λ, respectively, which are in agreement with the calculated results.

An approach for coding information based on the magnitude level of the radar cross section (RCS) of depolarizing chipless tags is proposed for the first time. It is used in combination with the classical frequency coding to increase the coding capacity. The control of the magnitude is based on the polarization mismatch between the tag and the reader antenna and it is fully compatible with a recent technique allowing reliable detection in real environments. The theoretical approach is validated by measurements.

A nonuniform (NU) tapered composite right/left-handed (CRLH) leaky-wave antenna (LWA) with minimized sidelobe level (SLL) is proposed. The design of this antenna is performed using an automated cosimulation approach based on a genetic algorithm optimization. Fair agreement is found between the full-wave and the experimental results. The experimental results show an 8-dB SLL reduction compared to a uniform CRLH LWA with the same gain in a 12-unit-cell structure.

We report in this paper the design and the realization of a compact wearable monopole antenna directly placed over an Artificial Magnetic Conductor (AMC), which is located directly on the body. The major contribution is that there is no space between the monopole and the AMC, or between the AMC and the body. Simulation results and measurements are in good agreement and show that the antenna's performances are as good as the best ones reported so far in the literature, while having a smaller volume. The antenna operates at 1.92 GHz with a bandwidth of 8%. The reflection coefficient of the antenna is −35dB. The measurement of the antenna gain provides a value of 4.3 dBi with a half-power beamwidth of 70° and a front-to-back radiation ratio of 15.8 dB. Measurement and simulation results also show that the AMC isolates well the monopole from the body: the localized Specific Absorption Rate (SAR) value calculated with 1 g of tissue is 0.34 W/kg with an injected power of 1 W. The antenna with the AMC is well adapted for wearable applications.