Wideband Multi-Port Reflectometer as an Alternative in Reflection Coefficient Measurement

 This paper presents the characterization and operation of an alternative device, which is known as multi-port reflectometer to measure the reflection coefficient of any device under test (DUT). Its configuration is formed by two power dividers (D) and four couplers (Q). The characterization is evaluated through the centres of power circles that also known as q-points. Its operation in the reflection coefficient measurement is tested by using three DUTs. The reflectometer’s good performance and wideband operation are proven between the frequency band of 1 and 6 GHz via the practical hardware measurement in the laboratory

26 GHz phase shifters for multi-beam nolen matrix towards fifth generation (5G) technology

This paper presents the designs of phase shifters for multi-beam Nolen matrix towards the fifth generation (5G) technology at 26 GHz. The low-cost, lightweight and compact size 0° and 45° loaded stubs and chamfered 90°, 135° and 180° Schiffman phase shifters are proposed at 26 GHz. An edge at a corner of the 50 Ω microstrip line Schiffman phase shifter is chamfered to reduce the excess capacitance and unwanted reflection. However, the Schiffman phase shifter topology is not relevant to be applied for the phase shifter less than 45° as it needs very small arc bending at 26 GHz. The stubs are loaded to the phase shifter in order to obtain electrical lengths, which are less than 45°. The proposed phase shifters provide return loss better than 10 dB, insertion loss of -0.97 dB and phase difference imbalance of ± 4.04° between 25.75GHz and 26.25 GHz. The Rogers RT/duroid 5880 substrate with dielectric constant of 2.2 and substrate thickness of 0.254 mm is implemented in the designs

Antenna array design with rectangular ring slot for 5G technology

A patch antenna with rectangular-shaped ring slot that fed by a coaxial probe is proposed in this article as the single element for planar patch array antenna design to meet the requirement of multiple input multiple output (MIMO) in fifth generation (5G) technology. Initially, the single antenna element is designed at three different center frequencies of 0.85, 1.9 and 2.6 GHz to cover the mobile operating frequency of 0.8, 0.85, 0.9, 1.8, 2.1 and 2.6 GHz, which considering the proposed 5G spectrum below than 6 GHz. The rectangular-shaped ring slot is introduced to the patch antenna with the partial ground plane to widen the bandwidth performance. The designed single element is then arranged to design planar arrays of 2 x 2. Each of elements in the planar array is fed by a coaxial probe. The designs are utilizing a high-performance substrate, Rogers 6010LM

Specific Absorption Rate Assessment of Multiple Microstrip Patch Antenna Array

Interaction between electromagnetic field (EMF) radiated from multiple antennas and human body is crucial to be explored as multiple antennas are the essential implemented devices to achieve the requirements of the future evolved fifth generation (5G) technology. Thus, this article presents a significant study of the radiated EMF effect from a single, and multiple antennas towards human through the assessment of specific absorption rate (SAR). The single antenna, 1 x 2, 1 x 3 and 1 x 4 arrays of microstrip patch antennas are designed to cover mobile operating frequencies of 0.8, 0.85, 0.9, 1.8, 2.1 and 2.6 GHz. Two types of human head phantoms are implemented in this study, which are specific anthropomorphic mannequin (SAM) and Voxel head model that placed close to single antenna or antenna array to investigate the penetration of EMF towards the human tissue. The single antenna or antenna array is placed with fixed distance of 10 mm from the phantom, which excited by maximum allowable power of 19 dBm in CST Microwave Studio 2016. The effect of the radiated EMF that quantified by SAR parameter, which depicts satisfying results against the established standard limits at averaged 1g and 10g mass of tissues for all designated frequencies that utilized for single and multiple antennas

Radiation pattern performance of unequally linear arrays with parasitic element

For next generation of 5G mobile base station antennas, multibeam, multifrequency and low sidelobe characteristics requested. Simplify the feeding network will contribute a low feeder loss and frequency dependent. From the previous research by the author, low sidelobe level reported by density tapered array configuration from -13 dB to -16 dB and the result maintained for wideband operation frequency at 28 GHz, 42 GHz, and 56 GHz. However, the grating lobe has occurred due to element spacing larger than a wavelength of higher frequency (56 GHz). In this paper, an investigation was made of the performance of radiation pattern for unequally microstrip linear array antenna in frequency 42 GHz and 56 GHz by loading parasitic elements. The effect of parasitic element to the impedance, gain, and sidelobe level of unequally microstrip linear spaced tapered array also examined. The design has been simulated using Ansoft High Frequency Structural Simulator (HFSS) ver 16.0

The investigation on size reduction feasibility of planar witricity device for biomedical implantable application

This article presents the investigation on size reduction feasibility of planar Witricity device for biomedical implantable application. Biomedical implantable application demands for very small size device. Thus, the planar type of Witricity device is designed and investigated with the aim of size reduction. There are two designs presented in this article. Design A has larger size with an area dimension of 120 × 120 mm2 and capable for energy transferable distance of 50 mm. Meanwhile, another Witricity device, namely Design B has smaller size of 80 × 80 mm2 area is specified for approximately 40 mm transfer distance. The feasibility investigation on size reduction is observed from three main parameters; current distribution, coupling efficiency and return loss. The size reduction of 55% by Design B may lead to the reduction of 20% transfer distance but still with acceptable of 58% coupling efficiency at 40 mm that beneficial for biomedical applications

The good, the bad, and the ugly: divorced mothers’ experiences with coparenting

This study produces a grounded theory of how 20 predominantly White, well-educated women experienced sharing physical custody of their children with their former partners after divorce or separation. Three patterns of coparenting were identified in the data: continuously contentious, always amicable, and bad to better. Five negative factors and three positive factors that influenced mothers’ coparenting relationships were identified. The type of relationship women had with their ex-partners was related to how they shared custody of their children (e.g., how they exchanged their children). The findings of this study suggest that shared physical custody relationships are dynamic and can vary greatly

Analysis on the effect of dielectric material and copper thickness of substrate towards the performance of ultra wideband ground slotted T-shaped power divider

Nowadays, the fifth generation (5G) wireless system is extensively studied to fulfill the continuously increasing demand for high data rate and mobility in wireless communication applications. Thus, to cope with this demand, various researches are required for front-end microwave components, which includes power divider. Therefore, in this article, the design and analysis of ultra wideband T-shaped power divider is presented. Two substrates are chosen in the design, which are Rogers RO4003C and TMM4 with copper thickness of 17 µm and 35 µm to analyze their effect towards ultra wideband performance of the designed power divider. The design and analysis are performed by using CST Microwave Studio. The optimal performance of the designed power divider is subjected to dielectric material and the copper thickness of the substrate. Where, the best design is obtained using TMM4 substrate that made of ceramic thermoset polymer with 35 µm copper thickness

Characterization of human head phantom based on its dielectric properties for wideband microwave imaging application

Characterization of phantom material based on its electrical properties across 1 to 6 GHz is investigated and presented in purpose for modelling of a human head phantom. This article presents five phantom samples mimicking main head tissues, which are the tissue of grey matter, white matter, cerebral spinal fluid (CSF), blood and skin. The preparation of phantom samples is performed by using common and cheap materials, which are jelly powder, gelatine, water and sugar. The characteristics of materials used are discussed on the composition ratios and electrical properties. The electrical properties of materials are measured using a special dielectric coaxial probe connected to a vector network analyser (VNA). The obtained data is analysed in terms of relative permittivity, and conductivity, for the observation and further discussion on the characterizations. This phantom of the human head tissues later can be applied in the microwave imaging system for a further study on the health monitoring of the human body

Design of ultra wideband phase shifter with improved scattering parameter performances

Aiming to achieve Ultra Wideband (UWB) performance, this paper presents an improvement of the square-shaped phase shifter design, which covers from 2.8 GHz to 10.6 GHz by implementing step impedances in order to improve the impedance matching of the phase shifter, whilst leads to better scattering parameter results. The phase shifter design is formed by using multilayer technique where 3 layers of conductors are interleaved with 2 layers of substrates between each of the conductor's layer. This technique ensures the phase shifter design to be small in size. Computer Simulation Technology (CST) Microwave Studio is used in developing the design and optimization stage. Meanwhile the measurement is done by using Vector Network Analyzer (VNA). The square-shaped phase shifter with step impedances enhances the bandwidth up to 34% as compared to the conventional square-shaped phase shifter. Additionally, analysis on air gap and alignment is also presented in order to show how both conditions affect the performance of the proposed phase shifter design