A compact low-profile all-textile multiband antenna operating in the 2.45/5.8 GHz ISM bands, mobile WiMAX IEEE 802.16 2005 (3.3–3.4 GHz), and 5G sub-6 NR frequency band n77 (3.85–4.0 GHz) is proposed for wireless body-area network (WBAN) applications. Good broadside radiations are achieved by properly activating the inherent TM ₁₁ , TM _21, and TM ₃₁ modes of a circular patch antenna. An elliptical slot and a C-shaped slot are employed to tune the three modes to the desired operating frequencies. A rectangular slot is used to reduce undesirable depression in the 5.8 GHz radiation pattern. The proposed antenna is fabricated from a conductive fabric layer integrated onto a single layer of denim, making it extremely low-profile and suitable for wearable applications. It has an overall size of 60 × 60 × 1.17 mm (0.64 λ_g × 0.64 λ_g × 0.0125 λ_g at 2.45 GHz). The measured maximum realized gains and bandwidth at the four frequencies are −0.81, −2.81, −1.16, 2.83 dBi, and 90, 190, 230, 570 MHz, respectively. Test results show that when the antenna is placed on and bent around a human arm model, the reflection coefficient has only slight influence. Since the antenna adopts full ground plane structure, the SAR values are far below the EU standard of 2 W/kg limit. With merit characteristics, the proposed design indicates a promising candidate for WBAN applications.

This letter presents a wideband transmitarray (TA) with reduced profile. A novel unit cell based on a wideband bandpass filter is developed and applied to the design of the TA. The TA consists of two identical tri-layer frequency selective surfaces (FSS), thus it has a lower profile compared to traditional designs which use at least four FSS layers separated by quarter-wavelength air gaps to obtain the 360-degree phase shift range. The FSS has a pair of square patches printed on the top and bottom layers, and a square slot loaded by four microstrips printed on the middle layer. The phase shift is achieved by simultaneously adjusting the size of the square patches. Within the frequency band of interest, the developed unit cell shows low insertion loss and sufficient phase shift range. An equivalent circuit model is developed to better understand the operating principles of the FSS. To validate the design concept, one prototype operating at 13.5GHz is designed, fabricated and measured. The measurement results show that the designed TA achieves 16% 1-dB gain bandwidth and 60% aperture efficiency. The developed unit cell has symmetric configurations so it can also be applied to the design of dual-polarized or circularly polarized TAs.

This work demonstrated a metamaterial array with polarization-insensitive and wide-angle operating in triple-band (GSM 1800, WiMAX, WLAN). The cell of the array consists of four same Split-Ring Resonators arranged in rotating central symmetry. The structure and size of the metamaterial cell were analyzed and optimized by using the microwave simulation software of CST. Meantime, we studied the absorption efficiency and harvesting efficiency under the normal and oblique incidences, energy distribution on the cell and the surface current paths. The simulation results show that the harvesting efficiency is 30%, 90%, and 74% at 1.75 GHz, 3.8 GHz, and 5.4 GHz, respectively, on the conditions of random polarization and the normal incidence. When the oblique incidence changes from 0° to 45°, this meta-harvester can also maintain effective harvesting efficiencies in triple-band. A 7 × 7 array has been fabricated and measured, and a good agreement with the simulated results was obtained.

This paper demonstrates a prototype of a self-sustained body area networks (BAN) sensor, which consists of the electrically small triple-band rectenna, the direct current (DC) energy management and storage module, the microcontroller, and the sensing and communication module. The proposed antenna is composed of corrugated metal-insulator-metal (MIM) plasmonic structures, which covers triple frequency bands, including GSM-900, UTMS-2100, and TD-LTE bands. Its electrical size is only $0.21\lambda \times 0.2\lambda$ at 900 MHz. The gains reach 1 dBi, 2.64 dBi, and -0.19 dBi at 0.9 GHz, 2.025 GHz, and 2.36 GHz, respectively. A triple-band rectifier for low power application is designed to convert the harvested radio frequency (RF) power into DC power. The maximum RF to DC conversion efficiency of the rectifier reaches 59% when the input power is -10 dBm. The proposed compact BAN sensor based on multiband wireless energy harvesting is suitable for human body self-monitoring and mobile healthcare.

This paper reports the design, fabrication, and measurement of a metasurface with wide-angle-reception and polarization-insensitive characteristics for harvesting electromagnetic energy. Unlike the metasurface unit cell with multiple vias reported in the literature, it realizes polarization-insensitive characteristics using a single via, which reduces the complexity of the structure significantly. The harvesting and absorption efficiencies at the normal and oblique incidences, energy distribution, and the surface current for different polarization angles are investigated. The simulation results show that the maximum harvesting efficiency is 88% at the center frequency of 5.8 GHz for the arbitrary polarization at the normal incidence of 0°. Within the oblique incidence range of 75°, the maximum efficiency remains higher than 77% for the random polarization. A 5 × 5 array has been fabricated and measured, and the good agreement with the simulated results is obtained.

In this work, we introduced the design, demonstration, and discussion of a wideband metamaterial array with polarization-independent and wide-angle for harvesting ambient electromagnetic (EM) energy and wireless power transfer. The array consists of unit cells with one square ring and four metal bars. In comparison to the published metamaterial arrays for harvesting EM energy or wireless transfer, this design had the wide operation bandwidth with the HPBW (Half Power Band Width) of 110% (6.2 GHz–21.4 GHz), which overcomes the narrow-band operation induced by the resonance characteristic of the metamaterial. On the normal incidence, the simulated maximum harvesting efficiency was 96% and the HPBW was 110% for the random polarization wave. As the incident angle increases to 45°, the maximum efficiency remained higher than 88% and the HPBW remained higher than 83% for the random polarization wave. Furthermore, the experimental verification of the designed metamaterial array was conducted, and the measured results were in reasonable agreement with the simulated ones.