In this paper, a flexible CPW fed ultrawide band (UWB) antenna with mu-negative (MNG) metamaterial is designed, fabricated, and tested for wearable applications. Initially, a UWB antenna of size 50 mm × 43 mm is fabricated on two different substrates, viz. flexible FR4 and semi-flexible Rogers RT/duroid 5880. A metamaterial structure fabricated on flexible FR4 shows a magnetic resonance from 7.2 GHz to 9.2 GHz with maximum stop band attenuation (−49 dB) and high MNG value (−2121.6) at 7.87 GHz. Then a (3 × 3) array of designed MNG metasurface is used as ground plane with flexible UWB antenna, which improves its overall gain and radiation pattern. The performance of the flexible antenna with/without metamaterial at various distances from flat and cylindrical three-layered human phantom of skin, fat, and muscle is studied. Further, the bending characteristics at different angles and performance over thin metallic sheet is also evaluated. Additionally, the peak specific absorption rate value averaged over 1 g of tissue at three chosen frequencies from UWB range (3, 5, 10 GHz) with/without metamaterial using 0.3 and 0.1 W of input power is also analyzed. The simulated and measured results are in good agreement which confirms that the designed antenna is a good candidate for wearable applications.

In this paper a wideband, flexible, and novel structured double negative (DNG) metamaterial is designed for S, C, X, and Ku microwave applications. The 12 mm × 12 mm sized metamaterial is fabricated on a flexible FR4 substrate with thickness 0.25 mm. The metamaterial shows a total wide DNG region of 8.2 GHz (3.8–4.3 GHz and 6.8–14.5 GHz). The transmission coefficient of the unit cell has a total band gap bandwidth of 8.3 GHz from frequency range 2 to 16 GHz. The designed metamaterial also exhibits an extra-large and continuous negative refractive index (NRI) bandwidth of 13 GHz (2–15 GHz). The stop band regions along with DNG and NRI regions individually cover S, C, X, and Ku microwave regions. The complete analysis is done using CST microwave studio. The simulated and measured transmission coefficient curves of the proposed metamaterial are in good agreement. The structure is simple, cost effective, flexible, light weight, and wideband covering S, C, X, and Ku microwave spectra.

Here a 3×3 array of dual band AMC metamaterial surface having size of 15 mm ×15 mm is proposed to increase gain value of a UWB antenna with dimension of 30 mm × 30 mm. Every notch created on AMC cell contributes in the generation of two resonance frequencies at 4.7 and 9.9 GHz. The structure of unit cell contains square shaped patch, a ring structure along with a central plus shape slit. AMC feature of having 0-degree reflection phase at two resonance frequencies (4.7 and 9.9 GHz) is also noticed here. Proposed AMC cell is utilized as reflector plain to increase gain and radiation features. Both designs (unit cell and wideband antenna) utilized FR-4 substrate having thickness 1.6 mm and dielectric constant of 4.4. Initially wideband antenna has 5.7 dB of gain and later it was increased to 8.3 dB by using AMC. The effect on metamaterial antenna gain with varying air gap (d) and array size is studied along with the impact on antenna parameters (gain, directivity and radiation pattern) due to grounded or ungrounded AMC structure is also studied to get optimum outcomes. Computer simulation technology (CST) software is used for simulation and simulation outcomes are confirmed with experimental outcomes and they show acceptable agreement.

In this article, broadband gain enhancement of an ultra-wide band (UWB) antenna is achieved by using 4 x 4 array of a wideband negative refractive index (NRI) metamaterial as a reflector layer. A novel shaped metamaterial sized 14.8 x 14.8 mm(2) with double negative (DNG) characteristics in three frequency regions has been fabricated on a flexible FR4 with 0.25 mm thickness. The proposed meta-material gives a continuous NRI bandwidth of 10 GHz (2-12 GHz). The effective parameters of the unit cell cover S, C, X, and Ku-band independently and show DNG region of 6.1 GHz at C (4-8 GHz) and X band (8.8-10.5 GHz, 11.2-11.6 GHz). The unit cell structure is also found to be feed insensitive. The unit cell has small volume of 54.76 mm(3) along with flexible nature which makes it suitable for wearable applications. For a 4 x 4 array the metamaterial still exhibits DNG characteristics. To understand the physical behavior of the unit cell, the circuit analysis along with the study of magnetic and electric field distribution at three resonance frequencies (2.2, 8.2 and 14.2 GHz) is done. Both simulation and measured results indicate that the gain and bandwidth of metamaterial antenna are enhanced by 2 dB and 0.8 GHz.