Publications

Found 28 results

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2013
2012
Nyaory GM, K’Onditi DBO, Ouma HA, Musyoki S. "Distribution of Electromagnetic Field Radiation from a Rectangular Cavity-Backed Slot Antenna, ADI-FDTD Perspective.". In: KSEEE-JSAEM 2012 International Engineering Conference.; 2012.
Nyaory GM, K’Onditi DBO, Ouma HA, Musyoki S. "Analysis of Electromagnetic Field Radiation from a Rectangular Cavity-Backed Slot Antenna Using ADI-FDTD Method." Journal Of Information Engineering and Applications . 2012;2(No. 8):1-8. Abstract

In this paper, a rectangular Cavity Backed Slot Antenna (CBSA) Model excited by a probe is investigated.
The analysis is carried out using the Alternating Direction Implicit - Finite Difference Time Domain (ADIFDTD)
Method which is applied to investigate its characteristics in terms of radiation patterns and power.
This is because the method is capable of providing a more accurate definition of the electromagnetic fields
within the rectangular apertures, while eliminating the Courant-Friedrich-Levy (CFL) stability condition
which is present in the regular Finite Difference Time Domain (FDTD) method. A cavity-backed slot
antenna structure with dimensions of 14cm×22cm×30cm is analyzed with the slot and aperture
measurements done at 3GHz. Results showing current distribution on the material surrounding the
apertures are presented and a discussion on the physical aspects of the aperture radiation phenomenon is
also presented.

**This research was sponsored by The German Academic Exchange Service (DAAD)**

Rop KV, KONDITI DBO, H.A. O, Musyoki S. "Parameter Optimization in Design of a Rectangular Microstrip Patch Antenna Using Adaptive Neuro-Fuzzy Inference System Technique." International Journal of Technical and Physical Problems of Engineering (IJTPE). 2012;4(12):16-23. Abstract

Modern wireless systems are placing greater
emphasis on antenna designs for future development in
communication technology because the antenna is a key
element in the overall communication system. A
Microstrip Antenna is well suited for wireless
communication due to its light weight, low volume and
low profile planar configuration which can be easily
conformed to the host surface. In this paper, an
optimization method based on adaptive neuro-fuzzy
inference system (ANFIS) for determining the parameters
used in the design of a rectangular microstrip patch
antenna is presented. The ANFIS has the advantages of
expert knowledge of fuzzy inference system (FIS) and the
learning capability of artificial neural network (ANN). By
calculating and optimizing the patch dimensions and the
feed point of a rectangular microstrip antenna, this paper
shows that ANFIS produces good results that are in
agreement with Ansoft HFSS 13.0 simulation results.

2011
Nyaory GM, Konditi DBO, Ouma HA, Musyoki S. "Designing Cavity–Backed Slot Antenna Array: A Numerical Implementation Using ADI-FDTD Method.". In: 6th JKUAT Scientific and Technological Conference. AICAD, Juja, Nairobi ; 2011. Abstract

ABSTRACT Slotted antenna arrays used with waveguides also known as Cavity-backed slot antenna arrays (CBSAA) are a popular set of antenna in navigation, radar and other microwave-frequency systems. For such antenna analysis and design in the sub-wavelength domain, there are currently three well established methods: The method of moments (MoM), the finite-element method (FEM) and the finite difference time-domain method (FDTD).
In this paper, a new finite-difference time-domain (FDTD) algorithm is proposed in order to eliminate the Courant–Friedrich–Levy (CFL) condition restraint. We therefore present the conventional alternating direction implicit - finite difference time-domain method (ADI-FDTD) method.
The proposed ADI-FDTD method is applied by solving Maxwell’s equations in time domain. We model and simulate waveguide structures with a case study of T10 mode on rectangular CBSAA consisting of 8 slot elements backed by a single cavity and simple feed network. The characteristics covering the microwave frequencies are analyzed, for instance; input impedance, return loss, bandwidth, VSWR, and far field radiation patterns. Moreover, several numerical results are presented, along with measured data, which demonstrate the validity, efficiency, and capability of the technique. Index Terms - Cavity-Backed Slot Antenna Arrays (CBSAA), Finite Difference Time-Domain (FDTD), Courant–Friedrich–Levy (CFL), and Alternating Direction Implicit (ADI)

2010
K. MJ, O. KDB, A. OH. "A Hybrid MOM/FDTD Formulation for EMC/EMI Problems Of Metallic Enclosures with Apertures.". In: KSEEE-JSAEM 2010 International Conference. MMUCK, Nairobi: International Journal of Technical and Physical Problems of Engineering (IJTPE); 2010. Abstract

A HYBRID MOM/FDTD FORMULATION FOR EMC/EMI PROBLEMS OF METALLIC ENCLOSURES WITH APERTURES

Josiah K. Makiche1 Dominic B. O. Konditi2, Heywood A. Ouma3
jkmakiche@yahoo.co.uk konditi_dom@yahoo.co.uk houma@ieee.org

1Department of Telecommunication and Information Engineering, Jomo Kenyatta University of Agriculture and Technology. 2Faculty of Engineering, Multimedia University College of Kenya. 3Department of Electrical and Information Engineering, University of Nairobi

Abstract—In this work a hybrid Method-of-Moments/Finite-Difference-Time-Domain (MoM/FDTD) formulation for the analysis of a metallic enclosure with an aperture is developed. The equivalence principle is used to divide the problem into two regions, region 1 and region 2, each of which is treated separately. The induced aperture magnetic currents are obtained via a moments method solution of the mixed potential integral equation using the generalized network formulation and triangular patch modeling. The computed magnetic current is directly incorporated into FDTD formulations as a source to determine the fields in the interior of the enclosure (region 2). The formulations are implemented in a computer code and used to analyze a typical problem of a rectangular enclosure with an aperture. The results are validated using data available in literature.
Keywords: Shielding effectiveness, metallic enclosures, method of moments, finite difference time domain, EMI/EMC.

KONDITI DBO, MAKICHE JK, ABSALOMS HO, ADIKA CO, KOECH EK, Dharmathikary VM. "Practical and Theoretical Evaluation of EMC/EMI: Problems of Metallic Enclosures with Apertures." International Journal of Technical and Physical Problems of Engineering (IJTPE). 2010;1(4):1-8. Abstract

PRACTICAL AND THEORETICAL EVALUATION OF EMC/EMI
Problems of Metallic Enclosures with Apertures

D.B.O. Konditi1 J.K. Makiche2 H.O. Absaloms3 C.O. Adika2 E.K. Koech2
V. M. Dharmadhikary3

1 Faculty of Engineering, Multimedia University College of Kenya, Nairobi, Kenya, onyango_d@yahoo.co.uk, dkonditi@mmu.ac.ke
2 Department of Telecommunication and Information Engineering, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya, jkmakiche@yahoo.co.uk, otychriss@yahoo.com, ekipyegon@yahoo.com
3 Department of Electrical and Information Engineering, University of Nairobi, Nairobi, Kenya, houma@ieee.org, dharmavasudha@gmail.com

Abstract- In this paper, experimental and theoretical evaluation of coupling of electromagnetic radiation is reported. Validation of the results is obtained by comparing the experimental data with theoretical data both generated using CONCEPT Simulator and data from our hybrid MoM/FDTD formulation for the analysis of metallic enclosure with apertures. Both the CONCEPT Simulator and the hybrid MoM/FDTD formulation utilize the method of moments, however, the hybridization of the latter makes it more adaptive to the solutions of apertures of arbitrary shape within enclosures with inhomogeneous dielectrics. The problems analyzed are rectangular slot, cross-shaped aperture and diamond-shaped aperture. The experimental results and MoM/FDTD results also agree fairly well with those available in the literature.

Keywords: Shielding effectiveness, metallic enclosures, method of moments, finite difference time domain, EMI/EMC.

2009
ABSALOMS HO. Status of iLabs in sub-Sahara Africa (iLabs-Africa). New York: Carnegie Corporation of New York; 2009.
2008
2006
O. OM, O KDB, A. OH. Microwave Response to Moisture Content. JKUAT, Nairobi ; 2006.
2004
H. A, T. T. Meta-GA Multi-Window Human Eye Detection. Orlando, Florida, USA; 2004.
2002
1999
H. A, T. T. "GA Relaxation Labeling." Trans. IEEJ. 1999;119-C(12):1489-1499.
H. A, Y. I, T. T. A Heuristic Approach to Solution of Industrial Optimisation Problems. Cape Technikon, Cape Town, South Africa; 1999.
1998
Absaloms HO. Genetic Algorithm Application to Image Processing Optimization Problems. Atsugi, Japan: Kanagawa Institute of Technology; 1998.
H A, T. T. "A Genetic Algorithm Solution to Relaxation Labeling of Line Images." Trans. IEEJ. 1998;118-C(11):1670-1671.
H. A, T. T. Optimization by Genetic Algorithm. Nairobi, Kenya; 1998.
1997
H. A, T. T. Applying Genetic Algorithm to Labeling. Nairobi, Kenya; 1997.
H. A, T. T. "A Novel Approach to Triangulating Contours for Surface Approximation." Trans. IEEJ. 1997;117-C(6):667-675.
H A, T. T. "Wire-Frame Approximation of Surface from Contour Data by GA." Trans. IEEJ. 1997;117-C(2):207-208.
1996
H. A, T. T. "A Study of Human Eyes’ Detection by Window-Pair Chasing." Trans. IEEJ. 1996;116-C(9):1015-1028.
H. A, T. T. Surface Reconstruction by Triangulation Using GA. Kyongju, Korea; 1996.
1995
H. A, T. T. A Detection Of Human Eyes by Window-Pair Chasing. Nairobi, Kenya; 1995.
1994
Absaloms HO, others. PCB CAD Training Manual.; 1994.
1993
Seneveratne A, Absaloms H, Ginige T, Fry M. Effect of Timer Management on Protocol Execution Performance. Wollongong, Australia; 1993.
1992
O. AH. Timer Server Implementation in Computer Communication Protocols. Sydney, Australia: University of Technology, Sydney (UTS) ; 1992.
1988
Absaloms HO. The Yagi-Uda Array. Nairobi, Kenya: University of Nairobi; 1988.

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