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A novel dual‐band circularly polarised (CP) antenna is presented in this study. The proposed antenna is composed of a U‐slot patch and four sequentially rotated shorted monopoles. Different from conventional omnidirectional CP antennas with shorted monopolar patches, a novel capacitively coupled technique is proposed to achieve good impedance matching, which makes it possible to generate unidirectional CP patterns simultaneously. This antenna can generate omnidirectional CP radiation patterns in the global positioning system L1 band (1575 ± 5 MHz) for navigation application and unidirectional CP radiation patterns in the 2.4‐GHz industrial, scientific, and medical band (2.40–2.48 GHz) for municipal wireless networks. The dual‐band performance can be tuned separately. Experimental results confirm the good performances of a compact antenna with the size of 0.26 λ0 × 0.26 λ0 × 0.026 λ0. The obtained 10‐dB impedance bandwidths can cover the two required bands. The 3‐dB axial ratio (AR) bandwidths cover the lower band and the upper band from 2.425 to 2.46 GHz. In addition, a wide 3‐dB AR beamwidth of 200° is obtained at 2.45 GHz. The simple structure and good performances make this antenna a good candidate for handheld devices and vehicular applications.

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Near field communication (NFC), a wireless technology operating at 13.56 MHz, provides an efficient approach for short distance transmission. The mutual inductance is an important parameter which affects impedance matching and transmission efficiency for NFC applications. In this paper, we proposed a simple and effective method based on transmission matrix to calculate the mutual inductance. Thus, the relation between transmission coefficient and distance is established. Validity of this method is demonstrated by comparing simulation results from HFSS and ADS.

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This study presents a shared structure for both near‐ and far‐field operations using magnetic resonance coupling and electromagnetic radiation. The proposed structure is composed of a rectangular loop and two monopoles. A duplexer is designed to route the near‐ and far‐field signals. For far‐field operation, both dual‐band resonance and dual‐sense circular polarisation required by the compass navigation satellite system (CNSS) are achieved. For near‐field operation, a wireless communication link operating at 13.56 MHz is established. The effect of matching distance on the transmission performances is studied and the optimal matching network is obtained. The proposed design is fabricated and verified experimentally. In the far‐field regime, it can achieve 10 dB impedance bandwidths of 17.2 and 15.8% and 3 dB axial ratio bandwidths of 4.6 and 12.8% and the two CNSS bands are fully covered. In the near‐field regime, an average transmission coefficient of 0.59 is achieved within the operation range of 5–30 mm by the proposed design. The obtained good performance reveals that the proposed shared structure is suitable to be applied in handheld devices for near‐field communication and CNSS applications.

Wound healing is a complex process composed of different stages, which involves extensive communication between the different cellular factors of the extracellular matrix (ECM). The radio frequency electromagnetic field (RF-EMF) has been used to accelerate the wound-healing process and it has been found to enhance cell alignment and mobility. The conventional methods for cell mobility analysis in an electromagnetic field generated by a radiation source are not advisable due to the low-precision, nonuniform distribution of the field, low efficiency of the analysis in batch and the lack of system integration for autonomous on-body operation. Here, a novel and versatile electromagnetic exposure system integrated with a microfluidic chip was fabricated to explore the EMF-induced response. A gradient electromagnetic field in a two-dimensional plane has been successfully established in the microchambers placed along the field line. In this work, by deploying our radiation experiments in vitro, we validated the on-chip monitoring of cell response to exposure. This electromagnetic field was simulated and human amniotic epithelial cells (HAECs) were cultured in different microchambers for continuous exposure to the electromagnetic field excited by a monopole RF antenna (1.8 GHz). New protrusions were generated and an obvious increase in filopodia with the increased field intensity was investigated. Meanwhile, the variation in intracellular Ca2+ concentration under the electromagnetic field was examined. The inhibitory effect of the Ca2+ circulation was further inspected to reveal the potential downstream signaling pathway in the RF-EMF-related bioassay, suggesting that cytoskeletal dynamics of cells under exposure are highly associated with the EGF receptor (EGFR)-cytoskeleton downstream signaling pathway. Finally, the field-induced cell elongation and alignment parallel to the field direction were observed. Additionally, the subsequent recovery (field withdrawal) and re-establishment (field re-exposure) were explored. These results indicated that this reliable and versatile exposure system for bioassay could achieve precise and high-throughput detection of the RF-EMF-induced cytoskeletal reorganization in vitro and evaluate the possible health risk from RF-EMF exposure.