Franklin Manene

ABSTRACT A circular polarized (CP) infrared (IR) leaky wave surface design is presented. The metasurface consists of an array of rectangular patches connected by microstrip and operating over the long-wave infrared (LWIR) spectrum with directional wave emission and absorption. The surface is composed of periodically aligned arrays of sub-wavelength metal patches separated from a ground plane by a dielectric slab. The design combines the features of the conventional patch and leaky wave antenna leading to a metasurface that preferentially emits CP IR radiation by use of axial asymmetrical unit cells. This is a deviation from reported structures that mainly employ a phase shifter to combine linearly polarized waves in order to attain circular polarization. The performance of this leaky wave surface is verified through full-wave simulation using the ANSYS HFSS finite element analysis tool. The leaky wave phenomenon is demonstrated by the frequency and angular dependence of the absorption while circular polarization is characterized via stokes parameters. The main beam of this surface can be steered continuously by varying the frequency while maintaining circular polarization within the main beam direction. A CP leaky wave at 10.6 μm with a scanning angle of 30° is demonstrated. Metasurfaces exhibiting spectral and polarization selectivity in absorption/emission hold the potential for impact in IR applications including detection, imaging, thermal management, energy harvesting and tagging.

Surface plasmon polariton (SPP) waveguides harbor many potential applications at visible and near-infrared (NIR) wavelengths. However, dispersive properties of the metal in the waveguide yields weakly coupled and lossy plasmonic modes in the mid and long wave infrared range. This is one of the major reasons for the rise in popularity of surface phonon polariton (SPhP) waveguides in recent research and micro-fabrication pursuit. Silicon carbide (SiC) is a good candidate in SPhP waveguides since it has negative dielectric permittivity in the long-wave infrared (LWIR) spectral region, indicative that coupling to surface phonon polaritons is realizable. Introducing surface phonon polaritons for waveguiding provides good modal confinement and enhanced propagation length. A hybrid waveguide structure at long-wave infrared (LWIR) is demonstrated in which an eigenmode solver approach in Ansys HFSS was applied. The effect of a three layer configuration i.e., silicon wire on a benzocyclobutene (BCB) dielectric slab on SiC, and the effects of varying their dimensions on the modal field distribution and on the propagation length, is presented.

ABSTRACT A planar leaky-wave antenna at infrared is modeled and simulated. The antenna is based on a microstrip patch array design of a leaky-wave impedance surface and is made up of gold microstrip patches on a grounded zinc sulphide substrate. Simulated results are presented and the leaky-wave characteristics are observed.

This paper presents a digital electrical energy meter based on an Anisotropic Magneto-Resistive (AMR) current sensor and an Arduino micro microcontroller. This study aimed at designing and fabricating a digital electrical energy meter using the AMR sensor which overcomes some of the shortcomings of traditional current sensors used in most energy meters, display electrical energy, consumer‟s terminal voltage, supply current, power factor and „real-time‟ power consumption. The study was carried out in the Department of Electrical and Control Engineering, Egerton University between September 2018 and December 2020. The meter was designed using Proteus 8 Professional software and fabricated on a printed circuit board. Algorithms were developed in C-language and stored in the microcontroller to continuously sample voltage and current signals derived from a successive supply voltage divider and the AMR current sensor, respectively. The sampling frequency was 2 kHz and every 10,000 samples...

In this paper, a novel Doherty Power Amplifier DPA based on a 10 W gallium-nitride high-electron-mobility transistor (GaN-HEMT) technology is designed using Advanced Design System (ADS) software. In the design, two different single Power Amplifiers (PAs) are combined using a Wilkinson power divider which is also used to connect the power to the load. The designed DPA operates in the range of 2.0-3.0 GHz and aims to achieve high efficiency, wide bandwidth and high output power for 5G applications. Simulation results showed a 40% fractional bandwidth and more than 44 dBm of saturated output power. In addition, the Power-Added Efficiency (PAE) and Drain-efficiency (Deff) are about 77% and 84%, respectively. A comparison with the other previous works shows enhancement in the maximum large-signal gain (L_S_Gain) in the average of 2.5 dB and an average PAE of about 10%. This improvement can be attributed to the deployment of the power divider/combiner proposed in the design and also the o...

A compact dual wideband bandpass filter for automotive radar (AR) and 5G millimeter-wave (mmWave) applications with adjustable bandwidths is presented in this work. The filter is based on microstrip dual-mode edge-coupled stub-loaded resonators (SLR). The novelty of this configuration is that it allows independent control of the bandwidths which is not obvious for many reported SLR-based filters. To achieve an overall size of 1.23λ_g× 2.02λ_g, these resonators are coupled and bent int o U-shape, T-shape, and E-shape. The U-shaped resonator, based on a quarter-wavelength transmission line, is coupled to the T-shaped element which constitutes the main feed line to obtain the dual-band response. Having a symmetrical structure, the design i s studied using the even-odd mode analysis. The layout is made using the Ansys high-frequency structural simulator (HFSS) and fabricated on Rogers RO3010 with a thickness of 1.28 mm, a dielectric constant of 10.2, and a loss tangent of 0.0022. The me...

The 5G technology is expected to use tunable lasers for wavelength selection during optical signal transmission. To accommodate the growing data demand, there is a need to develop lasers with a larger tuning range. In most lasers, Indium gallium arsenide phosphide (InGaAsP), Aluminum Gallium Arsenide (AlGaAs), and Gallium Arsenide (GaAs) have been used for the gain medium due to their direct bandgap and strong optical transitions. However, they have limitations such as low SMSR, low output power due to their narrow bandgap, and a narrow tuning range below 20nm. In this paper, vanadium-doped silicon-carbide was used in the active section of the Distributed Bragg Reflector (DBR) laser to achieve a wide tuning range, high SMSR, low threshold current, and high output power at a low gain current. The fundamental advantages of vanadium-doped siliconcarbide, including fast optical transitions, make its operation in the O-band (1278-1388 nm) possible. The DBR laser architecture design was adopted and designed in Ansys Lumerical. This work established that the use of Vanadium doped silicon-carbide in the active region provides a tuning range of at least 22nm wavelength, a threshold current was found to be 22.5mA with an optical output power of 13mW at the gain current of 120mA, and side mode suppression ratio (SMSR) of at least 45dB. Keywords — Distributed Bragg Reflector laser, Vanadium-doped silicon carbide.

Accessing affordable and reliable energy services for cooking is important in most developing countries. Improving access to affordable energy reduces effects on human health and environmental influences caused by burning of various biomasses. This review examines the energy resources available in the world and their use in cooking. It also looks at challenges and the ways these energy resources are used as well as possible solutions to such challenges. The major challenges facing the use of available fuels are low efficiencies, high cost, un-sustainability and indoor house pollution that affect many people. The paper has identified that the use of combustion-less cooking, the use of solar for cooking, hydrogen and electrical systems that improve cooking activities and therefore overcome indoor and environmental pollution. Research findings indicate that the pressure-cooking concept improves energy efficiencies in boiling operations. Other energy efficiency improvement techniques in...

A planar leaky-wave antenna at infrared is modeled and simulated. The antenna is based on a microstrip patch array design of a leaky-wave impedance surface and is made up of gold microstrip patches on a grounded zinc sulphide substrate. Simulated results are presented and the leaky-wave characteristics are observed.

ABSTRACT A circular polarized (CP) infrared (IR) leaky wave surface design is presented. The metasurface consists of an array of rectangular patches connected by microstrip and operating over the long-wave infrared (LWIR) spectrum with directional wave emission and absorption. The surface is composed of periodically aligned arrays of sub-wavelength metal patches separated from a ground plane by a dielectric slab. The design combines the features of the conventional patch and leaky wave antenna leading to a metasurface that preferentially emits CP IR radiation by use of axial asymmetrical unit cells. This is a deviation from reported structures that mainly employ a phase shifter to combine linearly polarized waves in order to attain circular polarization. The performance of this leaky wave surface is verified through full-wave simulation using the ANSYS HFSS finite element analysis tool. The leaky wave phenomenon is demonstrated by the frequency and angular dependence of the absorption while circular polarization is characterized via stokes parameters. The main beam of this surface can be steered continuously by varying the frequency while maintaining circular polarization within the main beam direction. A CP leaky wave at 10.6 μm with a scanning angle of 30° is demonstrated. Metasurfaces exhibiting spectral and polarization selectivity in absorption/emission hold the potential for impact in IR applications including detection, imaging, thermal management, energy harvesting and tagging.

ABSTRACT Metal losses lead to unacceptably low propagation lengths in THz and LWIR waveguides. While SPP based waveguides provide relatively good confinement and attenuation in the near-IR and visible these are insufficiently bound to the surface in the THz and LWIR. We study using surface phonon polaritons for waveguiding at these frequencies. An eigenmode approach was applied to model a hybrid waveguide structure at λ=10.6 μm. The results show that phonon-coupled hybrid waveguide of silicon carbide BCB and gold exhibit enhanced propagation length and confinement at LWIR.