Zubair Akhter

• Doctor of Engineering
• King Abdullah University of Science and Technology

The 2023 edition of the IEEE Microwaves, Antennas, and Propagation Conference (MAPCON 2023), the joint flagship conference of the IEEE Antennas and Propagation Society and IEEE Microwave Theory and Technology Society, was held at The Forum Celebration Center and Wyndham Hotel in Ahmedabad, India, 11–14 December 2023. Nearly 800 delegates were prese...

An antenna-on-chip (AoC) suffers from low radiation efficiency and gain because of the highly conductive silicon substrate used in standard complementary metal–oxide–semiconductor (CMOS) processes. Placing an artificial magnetic conductor (AMC) surface underneath the AoC not only isolates the antenna from the lossy substrate but also boosts its per...

This work presents a cross-polar dual-layer chipless radio-frequency identification (RFID) tag based on a ladder-shaped resonator design. An integrated ground plane enables direct attachment to human skin without performance deterioration. Simulations show that the ladder-shaped resonator provides several advantages over traditional L-shaped and st...

To fulfill the growing demand of next-generation wireless devices, additive manufacturing has emerged as the most economical, environmentally friendly, and high-throughput technique for mass manufacturing. At present, however, 3D-printed antenna substrates show 4%–8% variation in relative permittivity (εr) compared with typical tolerance values of...

Circular aperture probes have been successfully used for high-resolution near-field microwave imaging. It has been established that circular aperture probes could conceivably provide higher image fidelity compared to rectangular aperture probes used conventionally for near-field imaging. In this paper, it is proposed to further enhance the near-fie...

Optically transparent conductors have paved the way in various optoelectronic and radio frequency devices where high electrical conductivity and optical transparency with mechanical flexibility, as well as large area fabrication are deemed necessary. Printing techniques are viable for fabricating large-area devices with high mechanical flexibilitie...

System-on-chip (SoC) has become an attractive solution to achieve highly integrated wireless systems. However, the antenna-on-chip (AoC) suffers from poor radiation due to the lossy silicon substrate in standard complementary metal–oxide–semiconductor (CMOS) processes. Artificial magnetic conductors (AMCs) with the ground plane above the silicon ca...

With the advent of the Internet of things, 5G wireless communication, and smart city applications, demand for a new form of radio frequency (RF) electronics has risen, one that can be mounted or integrated on non‐conformal objects, is mass manufacturable at lower costs, and is optically transparent to maintain the aesthetics of the environment wher...

Radio-frequency identification (RFID) is becoming important with emerging applications for smart cities. RFID Tags are required to be small in size, low in cost and must exhibit as long read range as possible. There is a direct tradeoff between Tag antenna size and its read range. In this work, we study this tradeoff through the use of a relatively...

Real-time high-definition (HD) video transmission for long distances (≥1 km) between an unmanned aerial vehicle (UAV) and a ground station is a challenging problem. The existing real-time solutions are limited to relatively low-quality video streaming, whereas an HD video, which is stored in the local memory, is accessible only when the UAV returns...

Planar antenna reflectors are the modern design trend of both multibeam and frequency-scanning antenna arrays. The planar implementation of reflectors is typically performed using substrate-integrated waveguide (SIW) technology. A reflector’s profile can be different from the canonical one (parabolic, elliptic, hyperbolic, etc.) because of the effe...

The need for highly sensitive, environmentally stable, mechanically flexible, and low-cost temperature sensors for on-body measurements has been increasing with the wide adoption of personal Healthcare-Internet-of-Things (H-IoT) devices. Printed electronics (PE) is a good platform for such sensors because it enables the realization of flexible devi...

This paper presents a unique design of a cylindrical cavity to identify the dielectric materials with high resolution using the supervised machine learning algorithm. The mountable design of an aluminum-based cylindrical cavity records a quality factor of more than 9000 and provides an easy assembly of samples to be tested. The linear region of the...

Unmanned Aerial Vehicles (UAV), also known as autonomous drones, are being utilized for a variety of applications such as disaster management, search and rescue, surveillance, and remote monitoring. The wireless link to transfer the data from the drone to the ground station or another drone is critical for such applications. Antenna, being the most...

System-on-Chip has become an excellent solution for the high-level integration of systems. However, the primary barrier is the insufficient radiation from the on-chip antenna due to the lossy silicon substrate. In this paper, an ultra-thin artificial magnetic conductor (AMC) surface is proposed whose ground plane is on the top of the substrate to i...

An automated microwave technique for the monitoring of hidden objects for strategic applications has been presented. The proposed approach is quite novel as it implements and integrates the time-domain method in free-space with the indigenously developed automated scanning setup to obtain the dielectric profile of hidden objects in standard sand or...

The presence of undesirable solid contaminants can have adverse effects on the integrity of gas pipelines. One of the most common contaminants in such pipelines is black powder. Developing predictive maintenance protocols, including online quality monitoring, is imperative to ensure the on-spec supply of gas to customers and to avoid severe consequ...

In this paper, a novel microwave imaging methodology based on the simplified experimental setup for identifying hidden crevasse in a glacier or polar terrain is proposed. For scanning the glacier terrain, a new eight-slot Vivaldi antenna (ESVA) with high directivity (16 dBi) and wide bandwidth is proposed. The proposed antenna is designed for the w...

In this paper, the generalized substrate integrated waveguide (SIW) cavity technique is presented for the retrieval of broadband complex permittivity of medium loss dielectrics using a number of higher order modes of the proposed cavity. The proposed SIW cavity design improves the coupling by implementing a novel feeding topology to achieve a bette...

Wireless RF sensors are the building blocks of the next generation sensing techniques that are quite essential for the internet of things. In this paper, the RF system comprising of ultra-wideband transmitter-receiver antenna and highly sensitive planar sensor is proposed for wireless sensing of glucose and saline concentration, which are currently...

Abstract: In this paper, an attractive time-domain RF imaging technique is proposed for online monitoring of moving objects over conveyor belts. The proposed technique combines the strength of the time-domain approach and the Riccati equation-based ultrawideband reconstruction method in order to image the stratified lossy dielectric medium. The app...

In this paper, a highly efficient, low-cost scheme for two-dimensional microwave imaging is proposed. To this end, the AZIM (anisotropic zero index metamaterial) cells loaded Vivaldi antenna is designed and tested as effective EM radiation beam source required in the microwave imaging scheme. The designed antenna is first individually tested in the...

A novel time domain measurement technique is proposed to facilitate the simultaneous measurement of electrical properties (complex relative permittivity) and geometrical parameters (thickness) of the material under test (MUT). The overall process is noninvasive and noncontacting, which uses the measured scattering data of the MUT in the equivalent...

The hemisphere lens-loaded Vivaldi antenna for the microwave imaging applications is designed and tested in this paper. The proposed antenna is designed to work in the wide frequency band of 1–14 GHz, and is fabricated on the FR-4 substrate. The directivity of the proposed Vivaldi antenna is enhanced using a hemispherical shape dielectric lens, whi...

The conventional tapered slot Vivaldi antenna is well known for its ultra-wide band characteristics with low directivity. To improve the directivity of the conventional Vivaldi antenna, a four-slot Vivaldi antenna (FSVA) is proposed here to operate in the frequency range of 2–11 GHz. For feeding the FSVA, a binomial three-section V-shaped even mode...

In this letter, a tapered slot ultrawide band (UWB) Vivaldi antenna with enhanced gain having band notch characteristics in the WLAN/WiMAX band is presented. In this framework, a reference tapered slot Vivaldi antenna is first designed for UWB operation that is, 3.1–10.6 GHz using the standard procedure. The band-notch operation at 4.8 GHz is achie...

In this paper, a novel time domain RF imaging technique is presented for online monitoring of moving objects over conveyor belts. The proposed technique provides the knowledge of electrical properties i.e., relative permittivity and thickness of material under test (MUT), in addition to the structural properties i.e., size and shape of the interrog...

A terahertz reflectometry technique is proposed to assess the burn injuries of human skin. In order to differentiate burn injuries of various degrees, a simple stratified media models for the healthy and various degrees of burned skin are presented. The variation of water content is the key measure used in this study to differentiate the burned and...

A generalized ultra wideband approach for subsurface microwave imaging and nondestructive testing of the stratified media is presented. The proposed approach makes use of the scattering data measured in both frequency and time domains to reconstruct the inhomogeneous permittivity profile of the stratified media. This approach integrates the frequen...

A novel calibration independent technique that simultaneously determines the optical constants and material thickness with high accuracy, using the transmission and the reflection measurements, is proposed. A generalized closed form expression is derived to calculate the optical constants in terms of the measured transmitted and the reflected signa...

In this paper, a modified cylindrical Luneberg lens antenna is proposed for the microwave/millimeter wave imaging applications. The proposed Luneberg lens is designed using the Teflon substrate (ε r = 2.1) by making cylindrical voids of different radius along the circumference. The parameters of the designed antenna such as the directivity and the...

In this paper, a compact design of the ultra-wideband (UWB) highly directive double slot Vivaldi antenna (DSVA) is presented for microwave application in the frequency range of 2–10 GHz. In order to improve the directivity of the proposed DSVA, the zero index metamaterial (ZIM) unit cells are loaded on the E-plane of the antenna. It is found that t...

The experiment comprised of 10 treatments, such as T 0 : Control condition; T 1 : All chemical fertilizer as recommended dose; T 2 : Cowdung as recommended dose; T 3 : Compost as recommended dose; T 4 : ½ Cowdung + ½ Compost; T 5 : Cowdung + Compost; T 6 : Cowdung + ½ Chemical fertilizer; T 7 : Compost + ½ Chemical fertilizer; T 8 : Cowdung + Compo...

An experiment was conducted at the experimental field of Sher-e-Bangla Agricultural University, Dhaka during the period from October 2010 to March 2011 to study the feasibility of replacing chemical fertilizer by using organic fertilizer in wheat. The experiment comprised of 10 treatments, such as T 0 : Control condition; T 1 : All chemical fertili...

In this paper, a novel time domain practical scheme is proposed to reconstruct the dielectric image of the inhomogeneous multi-layered media. The overall process is noninvasive and noncontacting, which employs the measured scattering data of the test media in equivalent time domain. The measurement system consists of a modern vector network analyze...

A quasi-numerical optimization technique is presented to obtain the depth-dependent microwave dielectric image of the lossy inhomogeneous media. The proposed optimization scheme involves inverse solution of the corresponding microwave imaging problem in an efficient way. The initial condition for the optimization routine is obtained using an analyt...

In this paper, the design of a novel left-handed metamaterial (LHM) lens for the super resolution mm-wave imaging applications is presented. The designed LHM lens exhibits negative unity refractive index for two adjacent bands centered at 33.5 GHz and 35 GHz, respectively. It is observed that the proposed LHM lens bends the EM wave in a way, which...

In this paper, a compact design of conventional tapered slot antenna (TSA) loaded with the anisotropic zero-index metamaterial (ZIM) for the frequency range of 1 to 10 GHz is presented. The proposed TSA loaded with the ZIM exhibits an increase in the directivity up to 2.6 dB. The designed antenna is fabricated on the FR-4 substrate and tested. A go...

In this paper, the moisture content for cement based structures having different water to cement (w/c) ratio is carried out using the microwave free space technique. The measurement system consists of a vector network analyzer, a wide-band lens horn antenna and associated microwave components. The main focus here is to determine the loss factor or...

In this paper, the moisture content for cement based materials having different water to cement (w/c) ratios is measured using the microwave free space technique. The overall process is non-destructive and employs the time-domain measurement data. The measurement system consists of a vector network analyzer, a wide-band lens horn antenna, cement ba...

In this paper, the microwave based approach for the nondestructive testing of cement based materials and concrete structures is presented. The permittivity of a number of concrete samples having various material compositions has been determined using the proposed approach, which actually helps in distinguishing these samples. It is also observed th...

In this paper, a new technique is proposed for obtaining two-dimensional microwave image of the illuminated medium in order to detect concealed objects. The required image is obtained by scanning the medium under test (MUT) in the two-dimensional plane under the assumption that the MUT is illuminated with a plane wave and the scattering parameters...

The paper reports a dual-band transmitter that operates simultaneously at two wireless local area network (WLAN) frequencies of 2.4-GHz and 5.2-GHz. The transmitter's architecture employs a combination of direct-conversion and parallel schemes in order to achieve concurrent multi-band operation with reduced component count. This, in turn, leads to...

The paper reports design of a concurrent dual band transmitter for simultaneous operation at 2.4/5.2GHz. A combination of direct conversion and parallel architectures is utilized to satisfy the requirements of various signal modulation schemes that are employed in wireless local area network. The entire transmitter architecture is implemented using...

Objectives: To describe the presentation of spontaneously occurring functional ovarian cysts and compare the effectiveness of oral contraceptive pills with expectant management in the treatment of these cysts. Material and Methods: This study was carried out in the outpatient gynaecological clinic of Hayatabad Medical Complex and Khyber Teaching Ho...

Mol­ecules of the title compound, C16H20N2O2, reside across crystallographic centres of inversion with one half-mol­ecule in the asymmetric unit. The bond lengths and angles are normal and the crystal packing is stabilized by N—H⋯N and N—H⋯O hydrogen bonds.

In 6x6 diallel cross, heterosis was studied in 15 F₁. The variances due to heterosis were significant for all the characters. Overall heterosis partitioned into components and showed that average, variety and specific heterosis were significant for plant height, harvest index, days to 90% maturity and grain yield per plant. Spikes per pl...