Ph.D. Telecommunications, Université du Québec (INRS), Canada
M.S. Ingénierie des Systèmes Informatiques Communicants, Télécom Bretagne, France
B.S. Electrical and Electronic Engineering, Lebanese University, Lebanon
Passive microwave devices, RF & millimeter-wave transceivers for wireless systems, Ultra-wide Band Communications, and Substrate Integrated Circuits.
- D. Li, N. Khaddaj Mallat, and K. Wu, December 2013, Quasi-TEM Rectangular Waveguides with Frequency Selective Surface Walls: Part I–Electrical Properties and Geometrical Characteristics, International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, John Wiley and Sons Ltd., Vol. 27, Issue 2, pp. 334–352.
- D. Li, N. Khaddaj Mallat, and K. Wu, December 2013, Quasi-TEM Rectangular Waveguides with Frequency Selective Surface Walls: Part II—Physical Mechanism, International Journal of Numerical Modelling: Electronic Networks, Devices and Fields, John Wiley and Sons Ltd., Vol. 27, Issue 2, pp.353–368.
- N. Khaddaj Mallat, E. Moldovan, S.O. Tatu, and K. Wu, December 2011, Ultra-High-Speed Six-port Frequency-Division-Multiplexing V-band Transceiver, Asia-Pacific Microwave Conference 2011 (APMC 2011), Melbourne, Australia, pp. 896 – 899.
- N. Khaddaj Mallat, E. Moldovan, S.O. Tatu, and K. Wu, September 2011, Multi-Gbit/s 60 GHz Transceiver Analysis Using FDM Architecture and Six-Port Circuit, Special Issue on Digitization of RF and Front-End: Circuits and Algorithms-ZTE Communications, Vol. 9 No.3, Issue 31.
- N. Khaddaj Mallat, E. Moldovan, S.O. Tatu, and K. Wu, April 2011, 60 GHz Ultra Wideband Multiport Transceivers for Next Generation Wireless Personal Area Networks, Chapter Book, Ultra Wideband Communications: Novel Trends/Book 3", ISBN 978-953-307-461-0.
- N. Khaddaj Mallat, E. Moldovan, K. Wu, and S.O. Tatu, 2009, Millimeter-Wave Ultra-Wideband Six-Port Receiver Using Cross-Polarized Antennas, EURASIP (Hindawi Publishing Corporation), Journal on Wireless Comm. and Networking, Vol. 2009, Article ID 508678, 7 pages.
- N. Khaddaj Mallat, E. Moldovan, K. Wu, and S.O. Tatu, April 20-22, 2009, High Data Rate Cross-Polarized Millimeter-Wave Transmission Link, 2009 Global Symposium on Millimeter Waves (GSMM2009), Katahira Sakura Hall, Tohoku University, Sendai, Japan.
- S.O. Tatu, N. Khaddaj Mallat and E. Moldovan, 2009, Ultra Wideband Frequency Division Multiplexing Millimeter-Wave Multi-Port Receiver Analysis, European Microwave Week 2009, pp. 108 – 111, NuovaFiera di Roma, Rome, Italy.
- N. Khaddaj Mallat, E. Moldovan, and S. O. Tatu, 2009, V-band Quadrature Phase Shift Keying Demodulator Using WR-12 Six-port, Progress In Electromagnetics Research Letters, Vol. 6, pp. 193-199.
Data and Computer Communications, Electromagnetic theory.
- IEEE: Institute of Electrical and Electronics Engineers – Senior Member
- OIQ: Ordre des Ingénieurs du Québec
- Order of Engineers and Architects of Tripoli-Lebanon
Aug 01, 2018
Jul 01, 2018
In this letter, a novel design of a three-port antenna exhibiting pattern and polarization diversity characteristics is proposed. The radiating element of the proposed antenna comprises a ring loaded with periodical interdigital capacitors. The selective excitation of the three ports of the antenna enables omnidirectional and dual-polarized broadside radiation patterns in an overlapping bandwidth of 73 MHz (2.574 -2.647 GHz). The mutual coupling between any set of the two ports in the three-port antenna system is less than -20 dB. Six elements of the three-port ring antenna are arranged along the edges of a hexagon to generate 12 distinct beams (six dual-polarized broadside beams and six omnidirectional beams). Low mutual coupling and uncorrelated radiation patterns between the adjacent ports make the proposed three-port ring antenna a good candidate for use as an antenna element in massive multiple-input-multiple-output antenna systems for 5G applications.
May 01, 2018
Nov 23, 2017
Sampling of two dimensional signals is a rarely discussed aspect of signal processing. The scientific community has become used to the idea of rectangular sampling to the point that other possibilities are generally not even considered. The popularity of rectangular approach arises mostly due to its ease in extending it to three dimensions and also from a data handling point of view. In this paper, other sampling possibilities will be explored. This paper compares the qualitative and computational advantages of other approaches towards sampling of two dimensional signals. It is shown that in several cases hexagonal sampling is much more efficient than rectangular approach.
Comparison of RLS and LMS algorithms for interference cancelation in a fixed point to point microwave link
Oct 01, 2017
An efficient channel estimation and interference cancelation method for a fixed point to point (p2p) microwave link is designed and investigated; it is based on Least Mean Square (LMS) and Recursive Least Square (RLS) algorithms. The LMS and RLS algorithms are compared. The objective is to minimize the computational complexity of channel estimation by using algorithms and to increase channel capacity by implementing 2×2 MIMO systems. Both the channel estimation algorithms and interference cancelation approaches are modeled on the same grounds. Cross-polar interference and fading effects on received signals are analyzed and countered. The performances are compared with one another through simulation results and with analytical results presented in different texts and publications. © 2017 Praise Worthy Prize S.r.l. - All rights reserved.
Aug 01, 2017
Aug 01, 2017
Aug 01, 2017
Aug 01, 2017
Nov 16, 2016
A new uni-planar compact electromagnetic bandgap (EBG) structure is presented. The proposed EBG unit-cell is designed based on the stepped-impedance resonator (SIR) technique. Results show that the proposed EBG structure provides a wide frequency bandgap around the 60 GHz band. Moreover, results show that the proposed EBG unit-cell has further miniaturization factors of 0.79 and 0.66 compared to conventional uni-planar EBG and uniplanar compact (UC-EBG) structures, respectively.
Nov 16, 2016
Design and analysis of millimeter-wave (MMW) mushroom-like, circular-patch electromagnetic band-gap (EBG) structure is presented. The in-phase reflection and band-gap characteristics of the proposed EBG structure are investigated. Results show that the proposed EBG structure has stable reflection properties when normally and obliquely illuminated by a plane wave with different polarizations around the 60 GHz band. In addition, the proposed EBG structure is found to have a band-gap around the same frequency bandwidth. With these properties, proposed EBG structure is suitable to be used as reflectors in antenna applications in orderto increase the gain and improve the radiation characteristics.
Nov 16, 2016
This paper addresses the millimeter-wave antenna design aspect of the future 5G wireless systems. The paper reviews the objectives and requirements of millimeter-wave antennas for 5G. Recent advances in mm-wave antenna are reported and design guidelines are discussed. In particular, four different designs are identified from the recent literature based on their attractive characteristics that support 5G requirements and applications. The first design employs a dual-band slotted patch antenna operating at 28 GHz and 38 GHz. The antenna has circular polarization and is excited by a single-feed microstrip line. The present design is desirable for high-gain antenna array implementation in the mm-wave band, in order to compensate for the mm-wave propagation loss. The second design that is presented employs a compact planar inverted-F antenna (PIFA) with single layer dielectric load of a superstrate to enhance the gain and achieve a wide impedance bandwidth resulting in high efficiency. The third design that operates in the mm-wave band is a T-Shaped patch antenna. The proposed antenna a wideband range from (26.5 GHz-40 GHz) of the Ka band. The PFT substrate was used as it offers some advantages; low cost, high flexibility, harmless to human body and resistive towards environmental effects. The last mm-wave antenna design presented employs two MEMO arrays each composed of 2×2 antenna elements. The two MIMO array configurations are spatially orthogonal to each other which results in polarization diversity.
Nov 16, 2016
This paper presents an insight on the recently developed antenna pattern measurement system at COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan. Microwave Components and Devices (MCAD) research group at CIIT has been involved in antenna focused research activities but unavailability of anechoic chamber to measure radiation patterns has remained a huge handicap. In this regard efforts have been made to indigenously develop a radiation pattern measurement system. The system can measure radiation patterns from 600 MHz up to 26 GHz. The reflections from surroundings are suppressed by filtering the delayed signals in time domain. The system is automated through a Labview program which also provides users with the control and flexibility on various parameters. The system can provide gain at four frequency points simultaneously along with phase information.
Nov 01, 2016
A cognitive detect and avoid radar system based on chaotic UWB-MIMO waveform design to enable autonomous UAV navigation is presented. A Dirichlet-process-mixture-model (DPMM)-based Bayesian clustering approach to discriminate extended targets and a change-point (CP) detection algorithm are applied for the autonomous tracking and identification of potential collision threats. A DPMM-based clustering mechanism does not rely upon any a priori target scene assumptions and facilitates online multivariate data clustering/classification for an arbitrary number of targets. Furthermore, this radar system utilizes a cognitive mechanism to select efficient chaotic waveforms to facilitate enhanced target detection and discrimination. We formulate the CP mechanism for the online tracking of target trajectories, which present a collision threat to the UAV navigation; thus, we supplement the conventional Kalman-filter-based tracking. Simulation results demonstrate a significant performance improvement for the DPMM-CP-assisted detection as compared with direct generalized likelihood-ratio-based detection. Specifically, we observe a 4-dB performance gain in target detection over conventional fixed UWB waveforms and superior collision avoidance capability offered by the joint DPMM-CP mechanism.
Development of Substrate Integrated Waveguide filters for low-cost high-density RF and microwave circuit integration: Pseudo-elliptic dual mode cavity band-pass filters
Oct 01, 2016
The properties of dual mode resonance in planar SIW-based rectangular cavities are investigated and discussed. A specific mode combination of dual mode cavity presents a unique frequency response feature. With the aid of an optimization process or software, it is convenient to cascade a number of cavities with coupling apertures to form a filter. A 3-cavity pseudo-elliptic SIW filter based on H203 & H104 hybrid resonance is designed and fabricated on a Rogers TMM3 substrate. Measured results show that the insertion loss at the central frequency around 24 GHz is 4.58 dB and the return loss is better than 20 dB in the whole pass-band of 760 MHz. The design method can widely be used for high-density microwave integrated circuits and the mass-fabrication of such filters is made easy even when keeping development and processing costs very low.
May 01, 2016
Development of Substrate-Integrated Waveguide Filters for Low-Cost High-Density RF and Microwave Circuit Integration: Direct-Coupled Cavity Bandpass Filters With Chebyshev Response
Published in: IEEE Access (Volume: 3, Pages: 1313 - 1325, 2015)
Jul 01, 2015
Direct-coupled cavity bandpass filters with Chebyshev response are studied and realized, using the technique of planar substrate-integrated waveguide (SIW) for the purpose of high-density integration and cost reduction. Using a general mode-matching technique, the scattering matrix of waveguide bifurcation-type discontinuity and asymmetric iris are established and analyzed. Such discontinuities are used as coupling components and building blocks in the design of filters that are realized on RT/duroid 6002 with the ordinary printed circuit board process in our work. Measurement for one of the three four-pole filters gives 3.4 dB insertion loss and 17 dB return loss over the whole passband at near 24 GHz (K-band) with 440-MHz bandwidth (1.8%). The design method can be widely adopted for the development of microwave-integrated circuits, and the mass-fabrication of such SIW filters can be made easy while maintaining a very low cost.
Feb 01, 2015
Nov 01, 2014
Quasi-TEM rectangular waveguides with frequency selective surface walls: Part I - Electrical properties and geometrical characteristics
Apr 01, 2014
Electrical properties and geometrical characteristics of frequencyâ€selectiveâ€surfaceâ€loaded quasiâ€transverse electromagnetic (TEM) rectangular waveguides are investigated in detail. The properties of electrical field distributions over the cross section of waveguides at various periodical phase shift points are studied. The phenomena, in connection with artificial magnetic conductor (AMC), cavity resonance, and surface resonance, are discussed. A definition of bandwidth for AMC is proposed on the basis of the variation of average zâ€polarized electric fields along zâ€axis between two side dielectric surfaces. Standard deviation technique is used to describe the uniformity of electrical fields and cavity efficiency is defined to represent the percentage of useful cavity with uniform electrical fields. The dispersion relationship, bandwidths of AMC and single mode, and cavity efficiency for various types of AMC surfaces are examined and compared. The geometrical characteristics of quasiâ€TEM waveguides are studied in both theory and experiment. Design rules for highâ€quality quasiâ€TEM waveguides are proposed.
Apr 01, 2014
The physical mechanism of quasiâ€TEM (transverse electromagnetic) waveguides with frequency selective surface (FSS) walls is established on the basis of an equivalent magnetic current technique in this paper. The equivalent magnetic current distributions in the slots of dielectric surfaces with dipoleâ€FSS walls and dielectric surface of bareâ€slab, as well as hexagonal crystal FSS walls, are presented and discussed. This study shows that the electromagnetic fields in waveguide are mainly radiated from the concurrent magnetic current bands in longitudinal slots. The relationship between the uniformity of electromagnetic fields and the phase variation of longitudinal magnetic currents is discussed. The electrical properties and mechanism of quasiâ€TEM rectangular waveguides with slotlines are also investigated to confirm the proposed mechanism. Three categories of periodic structure, which are potentially useful as artificial magnetic conductor, are investigated, and the required conditions to realize quasiâ€TEM mode in rectangular waveguide are proposed.