For more than 25 years, the circularly polarized single-fed microstrip patch was considered to be extremely narrow-band. The reported performances are almost exclusively related to single patches printed on a dielectric substrate, which partially explains the frequency characteristics. The antenna proposed is a variation of the "almost square" patch and exhibits measured axial radio of less than 2.5 dB over a 13% bandwidth. The antenna was designed for wireless applications.

Planar inverted-F antennas (PIFAs) made of woven conductive textiles and of patterns embroidered with conductive threads are investigated. The influence of conductive thread density on antenna properties is considered in both cases. The effect of lockstitch on antenna resonant frequency is quantified. A metallic button is proposed as the transition between textile antennas and classical circuits. A full-textile prototype of a PIFA is designed and shown to operate properly in the ISM 2.4 band.

Moisture causes detuning and increased losses in textile antennas, and it affects resonant and wideband textile antennas differently. In this work, we studied the effect of moisture on a resonant textile planar inverted-F antenna (PIFA) and a wideband textile monopole antenna. Both antennas were manufactured by embroidering conductive yarn in denim textile. The input reflection coefficient, antenna gain, and gain patterns were measured on both antennas for different moisture contents. The results show that wideband antennas are less affected by moisture in comparison with resonant antennas. For communications applications, large moisture content in the textile antenna should be avoided; therefore a flexible, textile-based waterproofing antenna cover was proposed, manufactured, and tested. On the other hand, the effect of antenna detuning by moisture can be used for moisture-sensing application. This concept was demonstrated on the resonant textile PIFA in transmission and reflection setups, showing that the reflection setup gives better results.

One of the major challenges in the development of wearable antennas is to design an antenna that can at the same time satisfy technical requirements, be aesthetically acceptable, and be suitable for wearable applications. In this paper, a novel wearable antenna is proposed—textile realization of a slotted waveguide antenna. The antenna is realized using conductive fabric to manufacture the walls of a rectangular waveguide in which the slots were cut out. All connections and cuts are sewn with conductive thread taking over advantages of the traditional process of manufacturing textile objects. The developed slotted waveguide array prototype, containing three slots and designed for operation in the 5.8-GHz ISM band, is experimentally characterized and compared to an equivalent metallic antenna. The achieved operating bandwidth is larger than 300 MHz in both cases. The measured gain of a textile slotted waveguide array is around 9 dBi with a radiation efficiency larger than 50% in the whole operating bandwidth, i.e., the textile array showed a 2 dB lower gain in comparison to the metallic counterpart. The gain is stable in the whole bandwidth and the radiation patterns do not differ. The results demonstrated that such textile antennas are suitable for body-centric communication and sensor systems and can be integrated into clothing, e.g., into a smart safety vest or into a uniform. Further analysis of various realizations of slotted waveguide antennas is presented showing that different versions of the proposed antenna can be used in all three off-body, on-body, and in-body communication scenarios.

Recent numerical study predicted phenomenon of a gain increase of a shortened horn antenna with the help of embedded double-thin-wire ENZ metamaterial slab. Here, we perform an experimental investigation of shortened horn antenna (length of which spans 52% of the length of optimal horn) with much simpler single-wire ENZ slab operated in 10 GHz band. Measurements revealed gain increase of more than 2 dB (comparing to the gain of a bare shortened horn) in 12% fractional bandwidth, with return loss better than -13 dB.