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To evaluate the performance of a printed log-periodic dipole antenna (PLPDA) in outdoor environments, we present unmanned aerial vehicle (UAV)-based antenna measurements conducted in the far-field region. Non-tethered UAV flight operations were achieved by configuring commercially available UAVs separately as a transmitter (TX) and as a receiver (RX). UAVs configured in non-tethered mode provide flexibility in terms of altitude maintained by the UAV from the ground level. The TX section of the UAV consists of a portable signal generator and a PLPDA configured to transmit signals with an output power of +15 dBm at 0.8 and 3.5 GHz. Similarly, the RX section of the UAV is equipped with a real-time spectrum analyzer and an identical PLPDA. Using these two UAVs in TX and RX modes, the radiation pattern of the PLPDA was obtained in the azimuth plane. Since two identical PLPDAs were used, the realized gain of the PLPDA is evaluated using the two-antenna gain method. The test scenario involved the TX UAV hovering at the center while the RX UAV followed a circular trajectory around it. A comparison between the UAV measurements, anechoic chamber measurements, and simulated data demonstrates good agreement, validating the reliability of the measurements.

For ultra-high field and frequency (UHF) magnetic resonance imaging (MRI), the associated short wavelengths in biological tissues leads to penetration and homogeneity issues at 10.5 tesla (T) and require antenna transmit arrays for efficiently generated 447 MHz B1+ fields (defined as the transmit radiofrequency (RF) magnetic field generated by RF coils). Previously, we evaluated a 16-channel combined loop + dipole antenna (LD) 10.5 T head array. While the LD array configuration did not achieve the desired B1+ efficiency, it showed an improvement of the specific absorption rate (SAR) efficiency compared to the separate 8-channel loop and separate 8-channel dipole antenna arrays at 10.5 T. Here we compare a 16-channel dipole antenna array with a 16-channel LD array of the same dimensions to evaluate B1+ efficiency, 10 g SAR, and SAR efficiency. The 16-channel dipole antenna array achieved a 24% increase in B1+ efficiency in the electromagnetic simulation and MR experiment compared to the LD array, as measured in the central region of a phantom. Based on the simulation results with a human model, we estimate that a 16-channel dipole antenna array for human brain imaging can increase B1+ efficiency by 15% with similar SAR efficiency compared to a 16-channel LD head array.

This study presents an inkjet printed textile antenna realised using a novel fabrication methodology. Conventionally, it is very difficult to inkjet print onto textiles because of surface roughness. This study demonstrates how this can be overcome by developing an interface coated layer which bonds to a standard polyester cotton fabric, creating a smooth surface. A planar dipole antenna has been fabricated, simulated and measured. This study includes DC resistance, RF reflection coefficient results and antenna radiation patterns. Efficiencies of greater than 60% have been achieved with only one layer of conducting ink. The study demonstrates that the interface layer saves considerable time and cost in terms of the number of inkjet layers needed whilst also improving the printing resolution.

Near‐field mutual coupling among closely spaced antennas limits the deployment of wireless MIMO interconnects in chip‐to‐chip communication. This paper presents a circuit‐theoretic modeling and simulation study of near‐field MIMO (NFMIMO) systems using 1 × 1 and 2 × 2 dipole arrays. Simulations were performed using Altair Feko V2021.1 over the 24–36 GHz frequency range. Self and mutual impedances were computed, and S‐parameter expressions were derived from the electric and magnetic field components. The effect of varying interelement spacing on return loss and coupling efficiency was analyzed. Optimal spacings of D = 0.2 λ and D = 0.4 λ at 26.89 GHz and 30.45 GHz, respectively, resulted in improved impedance matching and enhanced power transfer. A shift in S 11 resonance with element spacing was observed, highlighting the critical role of antenna placement in NFMIMO performance.

In this work, a wideband magneto-electric dipole antenna with circular polarization is introduced, which covers the 2G, 3G, LTE, and 5G frequency bands. In the proposed antenna, a planar dipole antenna with triangular corners, which plays the role of an electric dipole with circular polarization radiation, is mounted on a vertically-oriented cavity, which acts like a magnetic dipole. A Y-shaped probe is used to excite the antenna, which improves the axial ratio (AR) diagram due to its unique geometry. A sample of the proposed antenna is fabricated, and its measurement results are presented. The measurement results show an impedance bandwidth of 81.46% from 2.35 to 5.58 GHz, which covers the entire bandwidth required for 5G applications. Also, the measured 3-dB AR bandwidth extends from 2.26 to 5.58 GHz (84.61%). The measurement results show a relatively stable gain over the whole band, with a maximum gain of 9.91 dB at 4.8 GHz. One of the most significant advantages of the magneto-electric dipole antenna is its high front-to-back ratio (F/B). This advantage is also achieved in the proposed antenna, resulting in a maximum measured F/B of 29.3 dB. The simulated and measured results show a good agreement.

A wideband microstrip series-fed magnetic dipole array antenna is proposed. The five-element dipole array antenna is designed to achieve both wide bandwidth and high gain because of its microstrip series feeding structure. The low-profile low-cost array is suitable for applications such as wideband high-gain wireless communications. Measured and simulated results are in good agreement. The measured impedance bandwidth of the array is enhanced up to 28.6% (5.0–6.7 GHz). The radiation patterns show its advantages of high gain (about 10 dBi), endfire radiation and vertical polarisation.

A design framework for developing full-textile reconfigurable dipole antennas is proposed for wearable applications. To this end, a precise embroidery process using conductive threads is applied to properly manage the antenna structure. Further, mechanical reconfiguration to enhance antenna operation by using solely clothing components is outlined. As a proof-of-concept, we present a full-textile embroidered dipole antenna with mechanical frequency reconfiguration. Specifically, reconfiguration is achieved by folding the dipole arms through a triangular formation. Conductive Velcro strips are employed to guide the necessary dipole arrangement. As shown, the proposed design methodology enables frequency tunability that ranges from 780 to 1330 MHz for UHF and L bands, with satisfactory radiation performance. The measured and simulated results are in good agreement, in terms of achieving similar frequency reconfiguration concept, as predicted by the electromagnetic simulation models.

This paper presents a modularized reconfigurable functional electromagnetic surface (MRFES) for broadband absorption and polarization conversion by using tightly coupled dipole antennas (TCDA) and back-loaded radio frequency (RF) circuits (BLRFC). A dual-polarized antenna array with tight coupling and wide angular scanning characteristics is designed. By loading different RF circuits on the back side of the antenna array’s ground plane, switchable broadband absorption and polarization conversion functions are achieved. The design adopts modularization to facilitate the replacement of back-loaded RF circuits for diverse electromagnetic (EM) control functions. The final design of the tightly coupled antenna array has a thickness of 13.437 mm and a size of 119.5 mm × 119.5 mm. It works in a bandwidth range of 4.14–13 GHz. Upon loading the absorption circuit board, a broadband absorbing electromagnetic (EM) surface is formed, achieving dual-polarization absorption within a bandwidth of 4.14–12.4 GHz. With the polarization conversion circuit board attached, polarization conversion effects are realized within a bandwidth of 4.4–12.9 GHz. Both simulations and experiments verify that the designed EM surface possesses modular reconfigurable functions for broadband absorption/polarization conversion. The proposed design scheme holds promising prospects for applications in active stealth, adaptive camouflage, intelligent communication and other fields.

A small size wideband (2–6 GHz) circularly-polarised log-periodic Koch fractal antenna (LPKFA) is proposed. The circular polarisation is produced by using a pair of unequal length crossed-dipoles, and the wideband property is achieved based on the concept of the log-periodic dipole antenna without a matching network. In addition, Koch-shaped dipoles are used as the radiation elements in the design.

A printed circularly polarised antenna array is presented that utilizes the inherent good bandwidth and stable gain of magneto‐electric dipoles in combination with the wideband benefits of a sequential rotation feed technique. The proposed antenna has a simple geometry using two substrates and does not require any additional cavity or parasitic elements. The designed and simulated antenna has an impedance bandwidth of more than 75%, a 3 dB axial ratio bandwidth of 67% and a peak gain of 12.4 dBic, with less than 3 dB gain variation across the entire axial ratio bandwidth. The antenna provides a good combination of simple and compact geometry, wide bandwidth, good gain and stable radiation patterns when compared to previously published research. Simulated as well as measured results are presented for a protype antenna array. A printed circularly polarised antenna array is presented that utilizes the inherent good bandwidth and stable gain of magneto‐electric dipoles in combination with the wideband benefits of a sequential rotation feed technique. The proposed antenna has a simple geometry using two substrates and does not require any additional cavity or parasitic elements. The antenna provides a good combination of simple and compact geometry, wide bandwidth, good gain and stable radiation patterns when compared to previously published research. Simulated as well as measured results are presented for a prototype antenna array.