Design method of a focusing dielectric lens antenna and temperature increment measurement at the focusing spot.

In radio wave hyperthermia therapy, array antenna configuration was mainly studied to generate a small spot at the diseased part. Array antennas have the flexibility in controlling radiation performance, such as spot positions, by using their numerous radiating elements. However, the flexibility is achieved at the expense of antenna structure complexity. On the other hand, a lens antenna can concentrate radio waves into a small spot by forming a lens shape. The simplicity of a lens antenna structure lends itself to easy handling in a practical application. Moreover, the frequency independence of the lens antenna allows for a more flexible selection of hyperthermia therapy frequencies. Therefore, the lens antenna is selected as a focusing antenna in this paper. The lens shaping method and the temperature increment measurement are the main contents of this paper. The designed lens has a diameter of 30 cm, a focusing distance of 30 cm, and a working frequency of 2.45 GHz. A thin lens design method is applied to reduce lens weight. Firstly, the focusing ability of the designed lens is ensured by comparing the spot size results of electromagnetic (EM) simulation with its theoretical value. A spot size of 1.77 cm is obtained in both cases. Next, the temperature increment is examined by EM simulations. The temperature at the 2 cm tumor was increased to 41 °C from the human body temperature of 37 °C by an input power of 10 Watts (W). For the temperature increment measurement, a tumor within human body phantom is utilized and the available input power is reduced to 4 W. The tumor temperature increased from 21.5 °C of room temperature to 24.4 °C, which was captured by a thermal imaging camera. As a result, the functionality of the lens antenna for hyperthermia therapy is verified.

Insertion Loss and Phase Compensation Using a Circular Slot Via-Hole in a Compact 5G Millimeter Wave (mmWave) Butler Matrix at 28 GHz.

Fifth generation (5G) technology aims to provide high peak data rates, increased bandwidth, and supports a 1 millisecond roundtrip latency at millimeter wave (mmWave). However, higher frequency bands in mmWave comes with challenges including poor propagation characteristics and lossy structure. The beamforming Butler matrix (BM) is an alternative design intended to overcome these limitations by controlling the phase and amplitude of the signal, which reduces the path loss and penetration losses. At the mmWave, the wavelength becomes smaller, and the BM planar structure is intricate and faces issues of insertion losses and size due to the complexity. To address these issues, a dual-layer substrate is connected through the via, and the hybrids are arranged side by side. The dual-layer structure circumvents the crossover elements, while the strip line, hybrids, and via-hole are carefully designed on each BM element. The internal design of BM features a compact size and low-profile structure, with dimensions of 23.26 mm × 28.92 mm (2.17 λ0 × 2.69 λ0), which is ideally suited for the 5G mmWave communication system. The designed BM measured results show return losses, Sii and Sjj, of less than -10 dB, transmission amplitude of -8 ± 2 dB, and an acceptable range of output phase at 28 GHz.

A comparison of cost-effectiveness between offering antidepressant-CBT combinations first or second, for moderate to severe depression in Japan.

BACKGROUND: It is not clear which method is more cost-effective: To initially provide all depressed patients with combination therapy (COMB; i.e. cognitive behavioural therapy plus pharmacotherapy), followed by antidepressant treatment (AD) for those still in depression; or, to first provide AD for all patients, followed by COMB for non-remission patients. The aim is to investigate whether a COMB-first strategy would be more cost-effective than an AD-first strategy, in treating depression. METHODS: A Markov model was developed to perform the analysis. The primary outcome was the incremental cost-effectiveness ratio (ICER) per quality-adjusted life year (QALY) at 104 weeks. Probabilistic sensitivity analysis and scenario analysis were performed, to investigate the uncertainty associated with the clinical parameters and the impact of CBT's cost on the results, respectively. RESULTS: The ICER per QALY at 104 week, was JPY 591,822 (USD 5,725) for moderate depression and JPY 499,487 (USD 4,832) for severe one. The scenario analysis revealed the ICER became JPY 1,147,518 (USD 11,101) for moderate and JPY 968,484 (USD 9,369) for severe when the CBT cost was set as JPY 14,400 (USD 139)(i.e. GBP 96: the unit cost of CBT in UK), which is well below the threshold recommended by NICE (i.e. GBP 20,000-30,000). LIMITATIONS: This is a model-based analysis which was conducted from the health insurance perspective. Then, the analysis from the societal perspective would generate different results. CONCLUSIONS: The results suggest that a COMB-first strategy would be more cost effective than an AD-first strategy.

Multi Beam Dielectric Lens Antenna for 5G Base Station.

In the 5G mobile system, new features such as millimetre wave operation, small cell size and multi beam are requested at base stations. At millimetre wave, the base station antennas become very small in size, which is about 30 cm; thus, dielectric lens antennas that have excellent multi beam radiation pattern performance are suitable candidates. For base station application, the lens antennas with small thickness and small curvature are requested for light weight and ease of installation. In this paper, a new lens shaping method for thin and small lens curvature is proposed. In order to develop the thin lens antenna, comparisons of antenna structures with conventional aperture distribution lens and Abbe's sine lens are made. Moreover, multi beam radiation pattern of three types of lenses are compared. As a result, the thin and small curvature of the proposed lens and an excellent multi beam radiation pattern are ensured.

Multibeam Characteristics of a Negative Refractive Index Shaped Lens.

Narrow beam width, higher gain and multibeam characteristics are demanded in 5G technology. Array antennas that are utilized in the existing mobile base stations have many drawbacks when operating at upper 5G frequency bands. For example, due to the high frequency operation, the antenna elements become smaller and thus, in order to provide higher gain, more antenna elements and arrays are required, which will cause the feeding network design to be more complex. The lens antenna is one of the potential candidates to replace the current structure in mobile base station. Therefore, a negative refractive index shaped lens is proposed to provide high gain and narrow beamwidth using energy conservation and Abbe's sine principle. The aim of this study is to investigate the multibeam characteristics of a negative refractive index shaped lens in mobile base station applications. In this paper, the feed positions for the multibeam are selected on the circle from the center of the lens and the accuracy of the feed position is validated through Electromagnetic (EM) simulation. Based on the analysis performed in this study, a negative refractive index shaped lens with a smaller radius and slender lens than the conventional lens is designed, with the additional capability of performing wide-angle beam scanning.

Increase of Input Resistance of a Normal-Mode Helical Antenna (NMHA) in Human Body Application.

In recent years, the development of healthcare monitoring devices requires high performance and compact in-body sensor antennas. A normal-mode helical antenna (NMHA) is one of the most suitable candidates that meets the criteria, especially with the ability to achieve high efficiency when the antenna structure is in self-resonant mode. It was reported that when the antenna was placed in a human body, the antenna efficiency was decreased due to the increase of its input resistance (Rin). However, the reason for Rin increase was not clarified. In this paper, the increase of Rin is ensured through experiments and the physical reasons are validated through electromagnetic simulations. In the simulation, the Rin is calculated by placing the NMHA inside a human's stomach, skin and fat. The dependency of Rin to conductivity (σ) is significant. Through current distribution calculation, it is verified that the reason of the increase in Rin is due to the decrease of antenna current. The effects of Rin to bandwidth (BW) and electrical field are also numerically clarified. Furthermore, by using the fabricated human body phantom, the measured Rin and bandwidth are also obtained. From the good agreement between the measured and simulated results, the condition of Rin increment is clarified.

A low-loss and compact single-layer butler matrix for a 5G base station antenna.

Researchers are increasingly showing interest in the application of a Butler matrix for fifth-generation (5G) base station antennas. However, the design of the Butler matrix is challenging at millimeter wave because of the very small wavelength. The literature has reported issues of high insertion losses and incorrect output phases at the output ports of the Butler matrix, which affects the radiation characteristics. To overcome these issues, the circuit elements of the Butler matrix such as the crossover, the quadrature hybrid and the phase shifter must be designed using highly accurate dimensions. This paper presents a low-loss and compact single-layer 8 × 8 Butler matrix operating at 28 GHz. The optimum design of each circuit element is also demonstrated in detail. The designed Butler matrix was fabricated to validate the simulated results. The measured results showed return losses of less than -10 dB at 28 GHz. The proposed Butler matrix achieved a low insertion loss and a low phase error of ± 2 dB and ± 10°, respectively. In sum, this work obtained a good agreement between the simulated and measured results.

Analysis of Graphene Antenna Properties for 5G Applications.

The incoming 5G technology requires antennas with a greater capacity, wider wireless spectrum utilisation, high gain, and steer-ability. This is due to the cramped spectrum utilisation in the previous generation. As a matter of fact, conventional antennas are unable to serve the new frequency due to the limitations in fabrication and installation mainly for smaller sizes. The use of graphene material promises antennas with smaller sizes and thinner dimensions, yet capable of emitting higher frequencies. Hence, graphene antennas were studied at a frequency of 15 GHz in both single and array elements. The high-frequency antenna contributed to a large bandwidth and was excited by coplanar waveguide for easy fabrication on one surface via screen printing. The defected ground structure was applied in an array element to improve the radiation and increase the gain. The results showed that the printed, single element graphene antenna produced an impedance bandwidth, gain, and efficiency of 48.64%, 2.87 dBi, and 67.44%, respectively. Meanwhile, the array element produced slightly better efficiency (72.98%), approximately the same impedance bandwidth as the single element (48.98%), but higher gain (8.41 dBi). Moreover, it provided a beam width of 21.2° with scanning beam capability from 0° up to 39.05°. Thus, it was proved that graphene materials can be applied in 5G.

Analysis on the Effects of the Human Body on the Performance of Electro-Textile Antennas for Wearable Monitoring and Tracking Application.

Previous works have shown that wearable antennas can operate ideally in free space; however, degradation in performance, specifically in terms of frequency shifts and efficiency was observed when an antenna structure was in close proximity to the human body. These issues have been highlighted many times yet, systematic and numerical analysis on how the dielectric characteristics may affect the technical behavior of the antenna has not been discussed in detail. In this paper, a wearable antenna, developed from a new electro-textile material has been designed, and the step-by-step manufacturing process is presented. Through analysis of the frequency detuning effect, the on-body behavior of the antenna is evaluated by focusing on quantifying the changes of its input impedance and near-field distribution caused by the presence of lossy dielectric material. When the antenna is attached to the top of the body fat phantom, there is an increase of 17% in impedance, followed by 19% for the muscle phantom and 20% for the blood phantom. These phenomena correlate with the electric field intensities (V/m) observed closely at the antenna through various layers of mediums (z-axis) and along antenna edges (y-axis), which have shown significant increments of 29.7% in fat, 35.3% in muscle and 36.1% in blood as compared to free space. This scenario has consequently shown that a significant amount of energy is absorbed in the phantoms instead of radiated to the air which has caused a substantial drop in efficiency and gain. Performance verification is also demonstrated by using a fabricated human muscle phantom, with a dielectric constant of 48, loss tangent of 0.29 and conductivity of 1.22 S/m.