Metamaterial structures and their potential capabilities have generated significant interest in the antennas and propagation community for well over a decade. The uncertainties associated with their measurement, however, and the claims related to their resultant performance are often a topic of debate. This issue's “Measurements Corner” column looks at options and expectations related to metamaterial measurements and begins to answer questions related to uncertainty assessment and reduction.

Game-Based Learning (GBL) is increasingly widespread as a learning technique in the engineering studies. However, this innovative methodology may be difficult to incorporate in some subjects due to their complex contents. This paper aims at combining traditional learning methodologies with game mechanics by using an ad-hoc gaming web environment and mobile devices to analyse the academic performance and motivation in engineering studies. A comparative study was carried out with 96 first-year engineering students. In this experience, the students were randomly divided into two groups: Control Group (CG) and Experimental Group (EG). The first group made use of the traditional learning methodology used, whilst the second group combined the traditional methodology with GBL and Information and Communication Technologies (ICT). The obtained results show that EG students significantly improve their academic performance and motivation, expressing a succinctly greater interest in the studied subject. Therefore, the integration of GBL in the teaching methodology could have a very positive impact as well as it could greatly ease the teaching-learning process in engineering studies.

A novel metamaterial absorber design able to operate in the C frequency band is presented, along with an analysis and a method to improve both its bandwidth and its angular stability. Simulation results for a FR4-based design are shown for comparison with existing designs. In addition, a simplified equivalent circuit is provided for a better understanding of the great angular stability and wide bandwidth exhibited by the proposed structure. Moreover, simulations, manufacturing and measurements of a thinner and more flexible metamaterial absorber, keeping the angular stability of the former one, while providing a wide bandwidth, are presented.

An ultrathin, compact ecofriendly antenna suitable for IoT applications around 2.45 GHz is achieved as a result of exploring the use of Tencel fabric for the antenna’s design. The botanical ecofriendly Tencel is electromagnetically characterized, in terms of relative dielectric permittivity and loss tangent, in the target IoT frequency band. To explore the suitability of the Tencel, a comparison is conducted with conventionally used RO3003, with similar relative dielectric permittivity, regarding the antenna dimensions and performance. In addition, the antenna robustness under bent conditions is also analyzed by measurement. To assess the relevance of this contribution, the ultrathin ecofriendly Tencel-based antenna is compared with recently published antennas for IoT in the same band and also, with commercial half-wave dipole by performing a range test on a ZigBee-based IoT testbed.

This paper aims at contributing to the specialized literature on experimental characterization of metasurfaces reflectivity. Growing demand on angularly stable metasurfaces reinforces the relevance of the results under oblique incidence. Generally, reflection coefficient phase measurements are more challenging than the amplitude ones. Thus, an artificial magnetic conductor (AMC) is used to analyze the critical aspects for enlarging the angular margin that can be properly measured. The importance of the retrieving methodology along with the proposed data post-processing is highlighted among the involved issues, according to the obtained results. The suitability of monostatic vs bi-static measurement set-ups for comparison with plane-wave simulation is studied. The aforementioned AMC is experimentally characterized using both set-ups providing relevant conclusions. The trade-off between the manufactured prototype dimensions (to resemble the simulated infinite one) vs the required anechoic chamber size (to fulfil far-field (FF) conditions i.e. plane wave incidence for the considered frequencies) is tackled. Indeed, a thorough literature revision shows that most authors do not have this key aspect into account. The relevance of the resulting error from comparisons between near-field (NF) retrieved measurements vs plane-wave simulation results is unveiled. This is even more critical when the angular stability is analysed, since the scattering patterns of the AMC are not conformed at near-field distances, which makes the errors even greater. Consequently, noteworthy conclusions concerning the characterization of AMCs in particular and metasurfaces in general, regarding far-field or near-field measurements and angular stability analysis will be presented.

A novel microwave metamaterial absorber design is introduced along with its manufacturing and characterization. Significant results considering both bandwidth and angular stability are achieved. Parametric analysis and simplified equivalent circuit are provided to give an insight on the key elements influencing the absorber performance. In addition, the constitutive parameters of the effective medium model are obtained and related to the absorber resonant behavior. Moreover, a new thinner and more flexible absorber version, preserving broad bandwidth and angular insensitive performance, is simulated, and an 8 × 8 unit-cells prototype is manufactured and measured for a limited angular margin in an anechoic chamber.