Metasurfaces for Far-Field Radiation Pattern Correction of Antennas under Dielectric Seamed-Radomes

A high-index dielectric radome seam is camouflaged with respect to a low-index dielectric radome panel by tuning the seam with carefully engineered metasurfaces. A transmission-line approach is used to model the metasurface-tuned seam and analytically retrieve the corresponding surface impedance, from which the unit-cell design is then tailored. Full-wave simulations and microwave antenna measurements performed on a proof-of-concept prototype validate the undesired scattering suppression effect in the case of normally and obliquely incident transverse electric and transverse magnetic wave illuminations. Robustness of the proposed solution to fabrication tolerances is also reported. The study presents metasurface-tuning as an easily implementable, frequency adjustable, and polarization insensitive solution to reduce the scattering of dielectric mechanical seams and improve the overall transparency performance of radome structures.

Optimal Characterization of 28 GHz Bowtie Antenna for 5G Applications

Here, the selection of the design parameters of the bowtie patch antenna (BPA) for 5G applications is presented as a multidimensional, multi-purpose design optimization problem. The operating frequency of the proposed antenna is 28 GHz, which is the standard for millimeter waveband and 5G technologies. In order to overcome this difficult design optimization, a new, fast and powerful optimization algorithm was used by modified the non-dominant sorting genetic algorithm (NSGA)-III and optimal characterization of the microwave antenna design was obtained. It is assumed that the optimal characterization gives the best solution for the determined cost function, among the possible solutions within the specified range. The superiority of the proposed method has been proven by comparing it with similar types of algorithm. The antennas in the results found have good performance operating at 28 GHz, with a return loss of up to –49 dB, a gain of around 1.96 dB, good directivity, and the radiation pattern of the proposed antenna has a good match over the required frequency. Therefore, the proposed design can be used in 5G devices. As a whole, the proposed design optimization process is an efficient, fast and reliable solution for all antenna design problems.

Preclinical Studies in Small Animals for Advanced Drug Delivery Using Hyperthermia and Intravital Microscopy

This paper presents three devices suitable for the preclinical application of hyperthermia via the simultaneous high-resolution imaging of intratumoral events. (Pre)clinical studies have confirmed that the tumor micro-environment is sensitive to the application of local mild hyperthermia. Therefore, heating is a promising adjuvant to aid the efficacy of radiotherapy or chemotherapy. More so, the application of mild hyperthermia is a useful stimulus for triggered drug release from heat-sensitive nanocarriers. The response of thermosensitive nanoparticles to hyperthermia and ensuing intratumoral kinetics are considerably complex in both space and time. To obtain better insight into intratumoral processes, longitudinal imaging (preferable in high spatial and temporal resolution) is highly informative. Our devices are based on (i) an external electric heating adaptor for the dorsal skinfold model, (ii) targeted radiofrequency application, and (iii) a microwave antenna for heating of internal tumors. These models, while of some technical complexity, significantly add to the understanding of effects of mild hyperthermia warranting implementation in research on hyperthermia.

A Novel Approach of Design and Analysis of a Hexagonal Fractal Antenna Array (HFAA) for Next-Generation Wireless Communication

The study and exploration of massive multiple-input multiple-output (MMIMO) and millimeter-wave wireless access technology has been spurred by a shortage of bandwidth in the wireless communication sector. Massive MIMO, which combines antennas at the transmitter and receiver, is a key enabler technology for next-generation networks to enable exceptional spectrum and energy efficiency with simple processing techniques. For massive MIMOs, the lower band microwave or millimeter-wave band and the antenna are impeccably combined with RF transceivers. As a result, the 5G wireless communication antenna differs from traditional antennas in many ways. A new concept of the MIMO tri-band hexagonal antenna array is being introduced for next-generation cellular networks. With a total scaling dimension of 150 × 75 mm2, the structure consists of multiple hexagonal fractal antenna components at different corners of the patch. The radiating patch resonates at 2.55–2.75, 3.45–3.7, and 5.65–6.05 GHz (FR1 band) for better return loss (S11) of more than 15 dB in all three operating bands. The coplanar waveguide (CPW) feeding technique and defective ground structure in the ground plane have been employed for effective impedance matching. The deviation of the main lobe of the radiation pattern is achieved using a two-element microstrip Taylor antenna array with series feeding, which also boosts the antenna array’s bandwidth and minimizes sidelobe. The proposed antenna is designed, simulated, and tested in far-field radiating conditions and generates tri-band S-parameters with sufficient separation and high-quality double-polarized radiation. The fabrication and testing of MIMO antennas were completed, where the measurement results matched the simulation results. In addition, the 5G smartphone antenna system requires a new, lightweight phased microwave antenna (μ-wave) with wide bandwidth and a fire extender. Because of its decent performance and compact architectures, the proposed smartphone antenna array architecture is a better entrant for upcoming 5G cellular implementations.

A Rapid Beam Pointing Determination and Beam-Pointing Error Analysis Method for a Geostationary Orbiting Microwave Radiometer Antenna in Consideration of Antenna Thermal Distortions

When observing the Earth’s radiation signal with a geostationary orbiting (GEO) mechanically scanned microwave radiometer, it is necessary to correct the antenna beam pointing (ABP) in real time for the deviation caused by thermal distortions of antenna reflectors with the help of the on-board Image Navigation and Registration (INR) system during scanning of the Earth. The traditional ABP determination and beam-pointing error (BPE) analysis method is based on the electromechanical coupling principle, which usurps time and computing resources and thus cannot meet the requirement for frequent real-time on-board INR operations needed by the GEO microwave radiometer. For this reason, matrix optics (MO), which is widely used in characterizing the optical path of the visible/infrared sensor, is extended to this study so that it can be applied to model the equivalent optical path of the microwave antenna with a much more complicated configuration. Based on the extended MO method, the ideal ABP determination model and the model for determining the actual ABP affected by reflector thermal distortions are deduced for China’s future GEO radiometer, and an MO-based BPE computing method, which establishes a direct connection between the reflector thermal distortion errors (TDEs) and the thermally induced BPE, is defined. To verify the overall performance of the extended MO method for rapid ABP determination, the outputs from the ideal ABP determination model were compared to calculations from GRASP 10.3 software. The experimental results show that the MO-based ABP determination model can achieve the same results as GRASP software with a significant advantage in computational efficiency (e.g., at the lowest frequency band of 54 GHz, our MO-based model yielded a 4,730,000 times faster computation time than the GRASP software). After validating the correctness of the extended MO method, the impacts of the reflector TDEs on the BPE were quantified on a case-by-case basis with the help of the defined BPE computing method, and those TDEs that had a significant impact on the BPE were therefore identified. The methods and results presented in this study are expected to set the basis for the further development of on-board INR systems to be used in China’s future GEO microwave radiometer and benefit the ABP determination and BEP analysis of other antenna configurations to a certain extent.

Optimized Planar Microwave Antenna for Nitrogen Vacancy Center Based Sensing Applications

Individual nitrogen vacancy (NV) color centers in diamond are versatile, spin-based quantum sensors. Coherently controlling the spin of NV centers using microwaves in a typical frequency range between 2.5 and 3.5 GHz is necessary for sensing applications. In this work, we present a stripline-based, planar, Ω-shaped microwave antenna that enables one to reliably manipulate NV spins. We found an optimal antenna design using finite integral simulations. We fabricated our antennas on low-cost, transparent glass substrate. We created highly uniform microwave fields in areas of roughly 400 × 400 μm2 while realizing high Rabi frequencies of up to 10 MHz in an ensemble of NV centers.

Direct observation of multiband transport in magnonic Penrose quasicrystals via broadband and phase-resolved spectroscopy

Quasicrystals are aperiodically ordered structures with unconventional rotational symmetry. Their peculiar features have been explored in photonics to engineer bandgaps for light waves. Magnons (spin waves) are collective spin excitations in magnetically ordered materials enabling non–charge-based information transmission in nanoscale devices. Here, we report on a two-dimensional magnonic quasicrystal formed by aperiodically arranged nanotroughs in ferrimagnetic yttrium iron garnet. By phase-resolved spin wave imaging at gigahertz frequencies, multidirectional emission from a microwave antenna is evidenced, allowing for a quasicontinuous radial magnon distribution, not observed in reference measurements on a periodic magnonic crystal. We observe partial forbidden gaps, which are consistent with analytical calculations and indicate band formation as well as a modified magnon density of states due to backfolding at pseudo-Brillouin zone boundaries. The findings promise as-desired filters and magnonic waveguides reaching out in a multitude of directions of the aperiodic lattice.