Muhammad Akmal Chaudhary received the master’s and Ph.D. degrees in electrical and electronic engineering from Cardiff University, Cardiff, U.K., in 2007 and 2011 respectively, and the M.B.A. degree in leadership and corporate governance from the Edinburgh Business School, Heriot-Watt University, Edinburgh, U.K., in 2022. Before joining Ajman University, United Arab Emirates, in 2012, he held a postdoctoral research position with the Centre for High Frequency Engineering, Cardiff University, U.K., where he carried out commercial work for Freescale Semiconductor, Mesuro, TriQuint Semiconductor, National Physical Laboratory (NPL), and GaN Systems. His research interests in nonlinear device characterization, spectrum-efficient power amplifiers, modulated measurement techniques, and microwave electronics have resulted in over 100 academic articles. Dr. Chaudhary is a Chartered Engineer of the Engineering Council, U.K., and a Fellow of the Higher Education Academy, U.K.
In this paper, new LC lumped components and composite lines are used to create a filtering branch line coupler (FBLC) with a small size and wide suppression band. New composite lines are proposed using applied LC lumped components, which are used as the coupler main branches. The proposed FBLC suppresses second to sixth harmonics with high attention level and provides a wide stopband from 1.6 GHz to 5 GHz with more than 20 dB of attention. The presented coupler is analyzed, designed, simulated, and implemented. The measured results show that the proposed FBLC correctly operates at 800 MHz with less than 0.25 dB of insertion loss. In addition, more than 29 dB of return loss and isolation is measured at operating frequency, which shows the correct performance of the proposed design. The size of the proposed FBLC is equal to 23.7 mm × 25.5 mm (0.086λ × 0.093λ), which shows an 87% size reduction. The proposed FBLC with the designed frequency can be used in the communication systems for narrow-band Internet of things (NB-IoT) and traffic control radar applications.
Physically unclonable functions (PUFs) are recently utilized as a promising security solution for authentication and identification of internet of things (IoT) devices. In this article, we present an efficient implementation of XOR Arbiter PUF (XOR APUF) on field-programmable gate arrays (FPGAs). In our work, we incorporated concept of discrete programmable delays logic (PDL) configurations, the obfuscated challenges and temporal majority voting (TMV) before the XOR operation concurrently to enhance uniqueness and security. The derived design has been verified on 25 Xilinx Artix-7 FPGAs and the results are promising with uniqueness of 48.69%, uniformity 50.73% and reliability 99.41%, which significantly improves over previous work into XOR APUF designs. In addition, we also investigate modeling attack resistance of the proposed design against various modelling attacks and the security analysis show that the proposed PUF has lower prediction rate (
This paper presents an implementation of a compact high-gain millimeter-wave dual-band antenna. It is worthwhile noting that the meandering approach was employed to reduce the antenna area by 40%. The designed antenna has a great potential to support the wireless body area networks that are useful in monitoring human health conditions. Particularly, the dual-band property of the antenna aids in catering to the fullduplex data exchange. The geometry of the proposed elliptic patch was analyzed to determine the highest gain which, subsequently, resulted in the achieved gain of 10.2 dBi. Finally, the design validation was obtained through the experimental measurements.
This paper presents a new approach to simplify the design of class-E power amplifier (PA) using hybrid artificial neural-optimization network modeling. The class-E PA is designed for wireless power transfer (WPT) applications to be used in biomedical or internet of things (IoT) devices. Artificial neural network (ANN) models are combined with optimization algorithms to support the design of the class-E PA. In several amplifier circuits, the closed form equations cannot be extracted. Hence, the complicated numerical calculations are needed to find the circuit elements values and then to design the amplifier. Therefore, for the first time, ANN modeling is proposed in this paper to predict the values of the circuit elements without using the complex equations. In comparison with the other similar models, high accuracy has been obtained for the proposed model with mean absolute errors (MAEs) of 0.0110 and 0.0099, for train and test results. Moreover, root mean square errors (RMSEs) of 0.0163 and 0.0124 have been achieved for train and test results for the proposed model. Moreover, the best and the worst-case related errors of 0.001 and 0.168 have been obtained, respectively, for the both design examples at different frequencies, which shows high accuracy of the proposed ANN design method. Finally, a design of class-E PA is presented using the circuit elements values that, first, extracted by the analyses, and second, predicted by ANN. The calculated drain efficiencies for the designed class-E amplifiers have been obtained equal to 95.5% and 91.2% by using analyses data and predicted data by proposed ANN, respectively. The comparison between the real and predicted values shows a good agreement.
A hybrid methodology for developing the wireless power transfer (WPT) system is proposed in this paper. The transmitting (Tx) resonator of the designed WPT with dimensions 40-by-40 sq. mm uses the advantage of the planar coil-based approach. On the other hand, the receiving resonator (Rx) is miniaturized through the defected ground structure-based technique that resulted in the two times size reduction (20-by-20 sq. mm). Furthermore, the optimization of Tx and Rx is performed for the development of the hybrid WPT system. Finally, realized WPT, operating at 300 MHz, demonstrated a power transfer efficiency of 66%.
This article reports the impact of the slow wave effect (SWE) on the design, analysis, and performance of defected ground structure (DGS)-based resonators and the associated wireless power transfer (WPT) systems. As a case study, a systematic analysis of closed-loop polygonal DGS-based resonators is developed which enables a unique methodology to trade off the defect shape and, in turn, SWE and the magnetic field to improve the resonator’s effectiveness. It is conceptualized and then experimentally demonstrated that the performance of DGS-based resonators is shape-independent for closed-loop defects. Subsequently, these resonators were aptly utilized to develop a WPT system prototype. An excellent agreement between the theoretical and measurement results demonstrates the effectiveness of the presented DGS-type WPT concept in this article.
This paper reports the conceptualization, and analysis of a geometrical approach to determine the shift in the in-phase reflection of three conformal meta-surfaces (MS). For the proposed approach, a planar array consisting of MS unit cells (MS-UCs) of a given dimension is drawn on a circle of desired radius (r). The path traveled by the reflected and incident EM wave in terms of an electrical length results in the shift of reflection angle. For the validation purpose, the conformed arrays are simulated under x- and y-polarized EM waves. The sum of the incident and reflected phases resulting in total shift is determined theoretically and compared with the simulated shifts of the three arrays. Furthermore, one of the conformed arrays is experimentally evaluated under the TEM incidence and compared with the theoretical and simulated result. The excellent agreement between the theoretical and measured results demonstrates the effectiveness of the proposed work.
This paper presents a design of a quasi-reflectionless differential phase shifter, which can provide arbitrarily prescribed group delay (GD) and flat phase difference. The proposed quasi-reflectionless differential phase shifter consists of quarter-wavelength coupled lines and series resistor-connected open-circuited half-wavelength stubs in the main and references branches. Closed-form design equations are derived to achieve arbitrary prescribed flat phase difference and GD. For flat phase difference within passband, the GD of the main and reference branches must be the same. In addition, the GD and phase difference flatness in passband are controlled by a series-connected resistor. For experimental validation, a microstrip line 90° quasi-reflectionless differential phase shifter with GD of 1.90 ns at a center frequency of 3.50 GHz is designed and fabricated. The measurement results are well agreed with simulation and theoretical predicted results.
This paper explores the use of Decision Tree algorithm in the development of small signal model of GaN HEMT. In this stage, each measured s-parameters are modelled separately exploiting the bias, frequency and geometry dependence of the device as input predictors. This necessitates the tuning of parameters using Bayesian optimization and Random search algorithms. The outcome in terms of MSE and MAE demonstrates that the Random search algorithm gives a superior agreement with the measured values for the entire frequency range. Subsequently, the developed model is incorporated in the commercial CAD environment and a class-F power amplifier is designed to highlight the seamless integration ability and effectiveness of the developed model.
This paper thoroughly analyzes six different architectures of Artificial Neural Network (ANN) used in the development of small-signal model of Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs). At the outset, multilayer perceptron, cascade-forward, nonlinear autoregressive with exogenous inputs (NARX) in series-parallel and parallel configurations, distributed layer network, and layer recurrent architectures are used to develop GaN HEMT models for simulating the behavior of the device. Subsequently, comparison of the proposed architecture is carried out in terms of ease of implementation, simulation time, computational efficiency, fitting curves, mean squared error, mean absolute error, and coefficient of determination at distinct bias conditions. It is identified that the NARX series-parallel architecture based model is the most effective small-signal model among all the other ANN based models. It is computationally efficient, simple to implement, and possess the best generalization capability. It is also observed that the multilayer perceptron and cascade-forward exhibit analogous performance but the latter has a little edge. The NARX-parallel and feedback delay exhibit similar performance whereas the layer recurrent architecture is found to be the least suitable for the modelling of GaN HEMTs.
This paper presents the development of a highly efficient defected ground structure-based near-field wireless power transfer (WPT) system. The required resonators possess a 30-by-30 sq. mm area and have meander line slots etched on the ground side. The length of the meander line was aptly varied to generate a greater magnetic field around transmitting and receiving resonators. Subsequently, this aided in enhancing the overall WPT performance. Particularly, the realized WPT system, working at 25 mm, demonstrated the power transfer efficiency equal to 81% at 300 MHz.