This page has only limited features, please log in for full access.

Unclaimed
Muhammad Akmal Chaudhary
Department of Electrical and Computer Engineering, College of Engineering and Information Technology, Ajman University, Ajman 346, United Arab Emirates

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Journal article
Published: 26 March 2021 in Electronics
Reads 0
Downloads 0

Several wireless devices and applications can be connected through wireless communication technologies to exchange data in future intelligent health systems (e.g., the Internet of Medical Things (IoMT)). Smart healthcare requires ample bandwidth, reliable and effective communications networks, energy-efficient operations, and quality of service support (QoS). Healthcare service providers host multi-servers to ensure seamless services are provided to the end-users. By supporting a multi-server environment, healthcare medical sensors produce many data transmitted via servers, which is impossible in a single-server architecture. To ensure data security, secure online communication must be considered since the transmitted data are sensitive. Hence, the adversary may try to interrupt the transmission and drop or modify the message. Many researchers have proposed an authentication scheme to secure the data, but the schemes are vulnerable to specific attacks (modification attacks, replay attacks, server spoofing attacks, Man-in-the middle (MiTM) attacks, etc.). However, the absence of an authentication scheme that supports a multi-server security in such a comprehensive development in a distributed server is still an issue. In this paper, a secure authentication scheme using wireless medical sensor networks for a multi-server environment is proposed (Cross-SN). The scheme is implemented with a smart card, password, and user identity. Elliptic curve cryptography is utilized in the scheme, and Burrows–Abadi–Needham (BAN) logic is utilized to secure mutual authentication and to analyse the proposed scheme’s security. It offers adequate protection against replies, impersonation, and privileged insider attacks and secure communication in multi-server parties that communicate with each other.

ACS Style

Haqi Khalid; Shaiful Hashim; Sharifah Syed Ahmad; Fazirulhisyam Hashim; Muhammad Chaudhary. Cross-SN: A Lightweight Authentication Scheme for a Multi-Server Platform Using IoT-Based Wireless Medical Sensor Network. Electronics 2021, 10, 790 .

AMA Style

Haqi Khalid, Shaiful Hashim, Sharifah Syed Ahmad, Fazirulhisyam Hashim, Muhammad Chaudhary. Cross-SN: A Lightweight Authentication Scheme for a Multi-Server Platform Using IoT-Based Wireless Medical Sensor Network. Electronics. 2021; 10 (7):790.

Chicago/Turabian Style

Haqi Khalid; Shaiful Hashim; Sharifah Syed Ahmad; Fazirulhisyam Hashim; Muhammad Chaudhary. 2021. "Cross-SN: A Lightweight Authentication Scheme for a Multi-Server Platform Using IoT-Based Wireless Medical Sensor Network." Electronics 10, no. 7: 790.

Research article
Published: 21 March 2021 in International Journal of RF and Microwave Computer-Aided Engineering
Reads 0
Downloads 0

The potential advantages of simultaneous wireless information and power transfer (SWIPT) applications have necessitated innovations in the associated circuits and systems. This article, therefore, explores the concept of cascaded resonators, for the first time, in the design of a compact‐size defected ground structure (DGS)‐based tri‐band wireless power transfer (WPT) system to advance the SWIPT technology. The design is augmented with a systematic design procedure that is preceded by the development of a new double‐elliptic DGS‐based tri‐band resonator. Initially, the analysis of the proposed resonator is performed to identify the impact of defect size on the bandwidth. Subsequently, the resonators are cascaded to achieve a tri‐band functionality and then utilized in the design of WPT. The designed WPT operates at 0.3, 0.5, and 0.9 GHz, and takes a compact size of 39 × 13 mm2. The measurement of the realized WPT with the transmitter and receiver, separated by the distance of 10 mm, provides an efficiency of around 60% at all three bands with the figure of merit values of about 0.5. Furthermore, the proposed design achieves a bandwidth of more than 3 MHz bandwidth at the frequencies corresponding to communication standards.

ACS Style

Kassen Dautov; Mohammad Hashmi; Galymzhan Nauryzbayev; N. Nasimuddin; Muhammad A. Chaudhary. Compact multi‐frequency system design for SWIPT applications. International Journal of RF and Microwave Computer-Aided Engineering 2021, 31, e22632 .

AMA Style

Kassen Dautov, Mohammad Hashmi, Galymzhan Nauryzbayev, N. Nasimuddin, Muhammad A. Chaudhary. Compact multi‐frequency system design for SWIPT applications. International Journal of RF and Microwave Computer-Aided Engineering. 2021; 31 (6):e22632.

Chicago/Turabian Style

Kassen Dautov; Mohammad Hashmi; Galymzhan Nauryzbayev; N. Nasimuddin; Muhammad A. Chaudhary. 2021. "Compact multi‐frequency system design for SWIPT applications." International Journal of RF and Microwave Computer-Aided Engineering 31, no. 6: e22632.

Journal article
Published: 18 February 2021 in Sensors
Reads 0
Downloads 0

The development of the industrial Internet of Things (IIoT) promotes the integration of the cross-platform systems in fog computing, which enable users to obtain access to multiple application located in different geographical locations. Fog users at the network’s edge communicate with many fog servers in different fogs and newly joined servers that they had never contacted before. This communication complexity brings enormous security challenges and potential vulnerability to malicious threats. The attacker may replace the edge device with a fake one and authenticate it as a legitimate device. Therefore, to prevent unauthorized users from accessing fog servers, we propose a new secure and lightweight multi-factor authentication scheme for cross-platform IoT systems (SELAMAT). The proposed scheme extends the Kerberos workflow and utilizes the AES-ECC algorithm for efficient encryption keys management and secure communication between the edge nodes and fog node servers to establish secure mutual authentication. The scheme was tested for its security analysis using the formal security verification under the widely accepted AVISPA tool. We proved our scheme using Burrows Abdi Needham’s logic (BAN logic) to prove secure mutual authentication. The results show that the SELAMAT scheme provides better security, functionality, communication, and computation cost than the existing schemes.

ACS Style

Haqi Khalid; Shaiful Hashim; Sharifah Syed Ahmad; Fazirulhisyam Hashim; Muhammad Chaudhary. SELAMAT: A New Secure and Lightweight Multi-Factor Authentication Scheme for Cross-Platform Industrial IoT Systems. Sensors 2021, 21, 1428 .

AMA Style

Haqi Khalid, Shaiful Hashim, Sharifah Syed Ahmad, Fazirulhisyam Hashim, Muhammad Chaudhary. SELAMAT: A New Secure and Lightweight Multi-Factor Authentication Scheme for Cross-Platform Industrial IoT Systems. Sensors. 2021; 21 (4):1428.

Chicago/Turabian Style

Haqi Khalid; Shaiful Hashim; Sharifah Syed Ahmad; Fazirulhisyam Hashim; Muhammad Chaudhary. 2021. "SELAMAT: A New Secure and Lightweight Multi-Factor Authentication Scheme for Cross-Platform Industrial IoT Systems." Sensors 21, no. 4: 1428.

Journal article
Published: 08 July 2020 in IEEE Access
Reads 0
Downloads 0

A dual-band impedance transformer for achieving very high impedance transformation (k) and frequency ratio (r) is presented in this paper. The design is accompanied by a thorough analysis and systematic design procedure for facilitating the rapid development of the prototypes. A number of case studies show the excellent design flexibility of the proposed design in regards to achieving ultra-high $k$ and $r$ . Two prototypes, with very high design specifications, working at concurrent $r=5$ , $k=8.04$ and $r=15$ , $k=20$ are fabricated to validate the proposed architecture and the design procedure. Subsequently, the application of the proposed impedance transformer is demonstrated in the design of a dual-band balun architecture with inherent impedance transformation capability. To evaluate the performance and the presented concept, an impedance transforming balun prototype is fabricated and the excellent agreement between the simulation and experimental results is a testament to the effectiveness of the proposed design.

ACS Style

Rahul Gupta; Mohammad S. Hashmi; Muhammad Akmal Chaudhary. Flexible Design Scheme for a Simple Dual-Band Ultra-High Impedance Transformer and Its Application in a Balun. IEEE Access 2020, 8, 125745 -125754.

AMA Style

Rahul Gupta, Mohammad S. Hashmi, Muhammad Akmal Chaudhary. Flexible Design Scheme for a Simple Dual-Band Ultra-High Impedance Transformer and Its Application in a Balun. IEEE Access. 2020; 8 ():125745-125754.

Chicago/Turabian Style

Rahul Gupta; Mohammad S. Hashmi; Muhammad Akmal Chaudhary. 2020. "Flexible Design Scheme for a Simple Dual-Band Ultra-High Impedance Transformer and Its Application in a Balun." IEEE Access 8, no. : 125745-125754.

Journal article
Published: 18 February 2020 in IEEE Access
Reads 0
Downloads 0

This paper reports a model to determine effective permittivity (εeff) and resonant frequency (fr) of microstrip patch antenna (MPA) covered with multiple dielectric layers. This model is augmented with a newly developed empirical expression to determine the εeff of multi-layered superstrates over a substrate. The development of empirical formulation makes use of conformal mapping approach (CMA) and series–parallel combination of dielectric boundaries between the ground plane and patch of the MPA. In this work, the MPA is designed on substrate having dielectric constant of ε1 whereas the superstrate layers have dielectric constants of ε2, ε3 … εn. It is shown that the proposed technique is able to predict the fr of MPA with error of 1.8%, 3.5%, and 1.4% when it is covered with a single dielectric layer with superstrate height of 4.5mm for respective conditions of ε1 = ε2, ε1 > ε2 and ε1 < ε2 (ε1 = 3.66, ε2 = 2.2/4.7). Furthermore, the developed technique is analyzed for distinct combination of substrate and two superstrate layers for the cases ε1 = ε2 > ε3, ε1 = ε2 < ε3, ε1 < ε2 > ε3, ε1 > ε2 < ε3, and ε1 > ε2 > ε3. Subsequently, the viability of the proposed technique is demonstrated in practical scenarios for body centric communications by considering single (e.g., jeans cotton, pure cotton, rayon, polyester, felt fabric, terry wool, and leather) and multiple (e.g., wool over jeans cotton and polyester, felt fabric over pure cotton and rayon) layers of textiles over MPA. The measurement results on various dielectric superstrates and textiles show excellent agreement with the corresponding theoretical results and thereby validate the reported theory. Finally, a comparison with the seminal works clearly shows the promise of the reported technique in this paper.

ACS Style

Dinesh Rano; Muhammad A. Chaudhary; Mohammad S. Hashmi. A New Model to Determine Effective Permittivity and Resonant Frequency of Patch Antenna Covered With Multiple Dielectric Layers. IEEE Access 2020, 8, 34418 -34430.

AMA Style

Dinesh Rano, Muhammad A. Chaudhary, Mohammad S. Hashmi. A New Model to Determine Effective Permittivity and Resonant Frequency of Patch Antenna Covered With Multiple Dielectric Layers. IEEE Access. 2020; 8 (99):34418-34430.

Chicago/Turabian Style

Dinesh Rano; Muhammad A. Chaudhary; Mohammad S. Hashmi. 2020. "A New Model to Determine Effective Permittivity and Resonant Frequency of Patch Antenna Covered With Multiple Dielectric Layers." IEEE Access 8, no. 99: 34418-34430.

Journal article
Published: 26 September 2019 in Energies
Reads 0
Downloads 0

This paper deals with sea salt transportation and deposition mechanisms and discusses the serious issue of degradation of outdoor insulators resulting from various environmental stresses and severe saline contaminant accumulation near the shoreline. The deterioration rate of outdoor insulators near the shoreline depends on the concentration of saline in the atmosphere, the influence of wind speed on the production of saline water droplets, moisture diffusion and saline penetration on the insulator surface. This paper consists of three parts: first a model of saline transportation and deposition, as well as saline penetration and moisture diffusion on outdoor insulators, is presented; second, dry-band initiation and formation modelling and characterization under various types of contamination distribution are proposed; finally, modelling of dry-band arcing validated by experimental investigation was carried out. The tests were performed on a rectangular surface of silicone rubber specimens (12 cm × 4 cm × 8 cm). The visualization of the dry-band formation and arcing was performed by an infrared camera. The experimental results show that the surface strength and arc length mainly depend upon the leakage distance and contamination distribution. Therefore, the model can be used to investigate insulator flashover near coastal areas and for mitigating saline flashover incidents.

ACS Style

Muhammad Majid Hussain; Muhammad Akmal Chaudhary; Abdul Razaq. Mechanism of Saline Deposition and Surface Flashover on High-Voltage Insulators near Shoreline: Mathematical Models and Experimental Validations. Energies 2019, 12, 3685 .

AMA Style

Muhammad Majid Hussain, Muhammad Akmal Chaudhary, Abdul Razaq. Mechanism of Saline Deposition and Surface Flashover on High-Voltage Insulators near Shoreline: Mathematical Models and Experimental Validations. Energies. 2019; 12 (19):3685.

Chicago/Turabian Style

Muhammad Majid Hussain; Muhammad Akmal Chaudhary; Abdul Razaq. 2019. "Mechanism of Saline Deposition and Surface Flashover on High-Voltage Insulators near Shoreline: Mathematical Models and Experimental Validations." Energies 12, no. 19: 3685.

Conference paper
Published: 01 August 2019 in 2019 IEEE 3rd International Conference on Circuits, Systems and Devices (ICCSD)
Reads 0
Downloads 0

This paper examines the application of a broadband modulated measurement system, and specifically how such a system can be used in combination with active IF load-pull in order to characterize a device whilst operating in an Auxiliary Envelope Tracking (AET). The AET modifies dynamically the instantaneous DC applied to the device through the optimization of baseband impedance. The experimental measurements are carried out on a GaN HEMTs device to investigate the idea of improving the linearity of the device using the very mechanism that is employed to improve efficiency of the device. The investigations have shown a significant improvement in linearity of the device.

ACS Style

Muhammad Akmal Chaudhary; Zubaida Yusoff; Jonathan Lees; Johannes Benedikt; Paul Tasker. Auxiliary Envelope Tracking Focused Investigations of a 10W GaN HEMTs Device. 2019 IEEE 3rd International Conference on Circuits, Systems and Devices (ICCSD) 2019, 92 -96.

AMA Style

Muhammad Akmal Chaudhary, Zubaida Yusoff, Jonathan Lees, Johannes Benedikt, Paul Tasker. Auxiliary Envelope Tracking Focused Investigations of a 10W GaN HEMTs Device. 2019 IEEE 3rd International Conference on Circuits, Systems and Devices (ICCSD). 2019; ():92-96.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Zubaida Yusoff; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2019. "Auxiliary Envelope Tracking Focused Investigations of a 10W GaN HEMTs Device." 2019 IEEE 3rd International Conference on Circuits, Systems and Devices (ICCSD) , no. : 92-96.

Conference paper
Published: 01 April 2019 in 2019 6th International Conference on Electrical and Electronics Engineering (ICEEE)
Reads 0
Downloads 0
ACS Style

Muhammad Akmal Chaudhary. Sensitivity of Microwave Power Transistors to Low Frequency Impedance Variations. 2019 6th International Conference on Electrical and Electronics Engineering (ICEEE) 2019, 1 .

AMA Style

Muhammad Akmal Chaudhary. Sensitivity of Microwave Power Transistors to Low Frequency Impedance Variations. 2019 6th International Conference on Electrical and Electronics Engineering (ICEEE). 2019; ():1.

Chicago/Turabian Style

Muhammad Akmal Chaudhary. 2019. "Sensitivity of Microwave Power Transistors to Low Frequency Impedance Variations." 2019 6th International Conference on Electrical and Electronics Engineering (ICEEE) , no. : 1.

Conference paper
Published: 01 May 2018 in 2018 5th International Conference on Electrical and Electronic Engineering (ICEEE)
Reads 0
Downloads 0

This paper introduces a novel method that allows the presentation of specific, broadband impedances to a DUT by loadpull. To investigate this method, a derivative of class J power amplifier termed BJ is emulated, which effectively lies between class J and class B along the reactive routes on the Smith chart. The mode helps explore baseband linearization approach and its suitability when using continuous mode architectures. Adopting out-of-band impedance optimization technique allows to present impedances and move progressively from a completely real set of loads to completely imaginary set of loads in a deterministic and systematic way. This further extends a view to look at how well the emulated mode linearizes at a set of BJ contour points along the way. The method uses multiple modulated signal sources, phase synchronized at both radio frequency (RF) and intermediate frequency (IF) to provide a complete multi-harmonic broadband loadpull capability controlled by a single local oscillator and allows complete impedance control at the DUT current generator plane.

ACS Style

Muhammad Akmal Chaudhary; Zulfiqar Ali Memon; Zubaida Yusoff; Jonathan Lees; Johannes Benedikt; Paul Tasker. Optimization of out-of-band impedance environment for linearity improvements of microwave power transistors. 2018 5th International Conference on Electrical and Electronic Engineering (ICEEE) 2018, 219 -223.

AMA Style

Muhammad Akmal Chaudhary, Zulfiqar Ali Memon, Zubaida Yusoff, Jonathan Lees, Johannes Benedikt, Paul Tasker. Optimization of out-of-band impedance environment for linearity improvements of microwave power transistors. 2018 5th International Conference on Electrical and Electronic Engineering (ICEEE). 2018; ():219-223.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Zulfiqar Ali Memon; Zubaida Yusoff; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2018. "Optimization of out-of-band impedance environment for linearity improvements of microwave power transistors." 2018 5th International Conference on Electrical and Electronic Engineering (ICEEE) , no. : 219-223.

Conference paper
Published: 01 March 2018 in 2018 4th International Conference on Devices, Circuits and Systems (ICDCS)
Reads 0
Downloads 0

This paper presents a novel RF load pull test setup that allows for the presentation of user specified impedances at both the RF (Radio frequency) and IF (intermediate frequency) domain, to enable the investigation of linear high efficiency power amplifier design using measurement data. The RF load pull impedances at the fundamental, and second harmonic were set to produce a derivative of a class J amplifier to emulate a high efficiency mode of operation. The IF impedance up to the fifth IF product was then varied to quantify its effect on linearity. To enable this investigation a multi-sine stimuli was synthesized using multiple signal sources all phase locked to reference local oscillator. It was found that a greater than 10dB improvement in linearity was achieved by actively injecting a signal at IF that can be applied in an envelope tracking system.

ACS Style

Muhammad Akmal Chaudhary. Synthesis of Broadband IF and RF Impedances under Multi-sine Stimuli. 2018 4th International Conference on Devices, Circuits and Systems (ICDCS) 2018, 91 -94.

AMA Style

Muhammad Akmal Chaudhary. Synthesis of Broadband IF and RF Impedances under Multi-sine Stimuli. 2018 4th International Conference on Devices, Circuits and Systems (ICDCS). 2018; ():91-94.

Chicago/Turabian Style

Muhammad Akmal Chaudhary. 2018. "Synthesis of Broadband IF and RF Impedances under Multi-sine Stimuli." 2018 4th International Conference on Devices, Circuits and Systems (ICDCS) , no. : 91-94.

Conference paper
Published: 01 November 2017 in 2017 International Multi-topic Conference (INMIC)
Reads 0
Downloads 0

This paper presents a refined multitone measurement system for the robust characterization of nonlinear microwave devices when subjected to broadband multi-tone stimuli. This refined system has the ability to present specific, constant impedances, not only to the baseband (IF) components, but also to signals located around fundamental (RF) and significant harmonic frequencies. Achieving such comprehensive impedance control across wide modulation bandwidths is important and allows the `emulation' of new and specific modes of power amplifier operation, and the subsequent waveform characterization of microwave devices operating in such environments. The modified system is demonstrated through a number of applications: firstly the experimental investigation and baseband optimization of a 10W GaN HEMT under nine-tone excitation, and secondly, the emulation of a multitone Class-J impedance environment with optimized baseband impedance environment that interestingly highlights the presence of separate optimum baseband impedance conditions necessary for the reduction of individual Intermodulation (IM) products.

ACS Style

Muhammad Akmal Chaudhary; Zulfiqar Ali Memon; Jonathan Lees; Johannes Benedikt; Paul Tasker. Multitone measurement system for linearity investigations of microwave devices. 2017 International Multi-topic Conference (INMIC) 2017, 1 -4.

AMA Style

Muhammad Akmal Chaudhary, Zulfiqar Ali Memon, Jonathan Lees, Johannes Benedikt, Paul Tasker. Multitone measurement system for linearity investigations of microwave devices. 2017 International Multi-topic Conference (INMIC). 2017; ():1-4.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Zulfiqar Ali Memon; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2017. "Multitone measurement system for linearity investigations of microwave devices." 2017 International Multi-topic Conference (INMIC) , no. : 1-4.

Conference paper
Published: 01 November 2016 in 2016 16th Mediterranean Microwave Symposium (MMS)
Reads 0
Downloads 0

This paper presents the robust characterization of nonlinear microwave devices driven by broadband modulated multi-sine stimuli by using a refined multi-tone waveform measurement system. The substantial contribution comes from the capability of the measurement system to measure and average the time domain waveforms of adjacently modulated signals on a similar time scale for different modulation frequencies. The enhanced system demonstrates the ability of presenting the constant baseband (IF) loads across wide modulation bandwidth which is extremely imperative for the precise evaluation of inherent nonlinearity of microwave devices. The measurement system is later applied for the experimental investigations of baseband impedance variation effects on 10W GaN HEMT through the optimization scheme based on the simultaneously engineering of significant baseband components(IF1 and IF2) and higher baseband components(IF3 and IF4).

ACS Style

Muhammad Akmal Chaudhary; Zulifqar Ali Memon; Zubaida Yusoff; Jonathon Lees; Johannes Benedikt; Paul Tasker. Characterization of baseband electrical memory in microwave devices using multi-tone measurement system. 2016 16th Mediterranean Microwave Symposium (MMS) 2016, 1 -4.

AMA Style

Muhammad Akmal Chaudhary, Zulifqar Ali Memon, Zubaida Yusoff, Jonathon Lees, Johannes Benedikt, Paul Tasker. Characterization of baseband electrical memory in microwave devices using multi-tone measurement system. 2016 16th Mediterranean Microwave Symposium (MMS). 2016; ():1-4.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Zulifqar Ali Memon; Zubaida Yusoff; Jonathon Lees; Johannes Benedikt; Paul Tasker. 2016. "Characterization of baseband electrical memory in microwave devices using multi-tone measurement system." 2016 16th Mediterranean Microwave Symposium (MMS) , no. : 1-4.

Articles
Published: 07 March 2016 in Journal of Electromagnetic Waves and Applications
Reads 0
Downloads 0

In this paper, the design of an RF broadband transformer for wideband code division multiple access (WCDMA) tracking generators to be used in envelope tracking RF power amplifiers systems is presented. A ferrite toroidal core with a trifilar wound RF broadband transformer has been chosen to satisfy the (WCDMA) bandwidth requirement and also the power amplifier performance criteria that include the efficiency, electrical isolation, size and power consumption. The design components investigated comprises ferrite materials, number of turns on core windings and size.

ACS Style

Zubaida Yusoff; Jonathan Lees; Muhammad Akmal Chaudhary; Steve C. Cripps. Ferrite toroidal core with a trifilar wound RF broadband transformer design for tracking generators in wideband code division multiple access envelope tracking RFPA systems. Journal of Electromagnetic Waves and Applications 2016, 30, 599 -611.

AMA Style

Zubaida Yusoff, Jonathan Lees, Muhammad Akmal Chaudhary, Steve C. Cripps. Ferrite toroidal core with a trifilar wound RF broadband transformer design for tracking generators in wideband code division multiple access envelope tracking RFPA systems. Journal of Electromagnetic Waves and Applications. 2016; 30 (5):599-611.

Chicago/Turabian Style

Zubaida Yusoff; Jonathan Lees; Muhammad Akmal Chaudhary; Steve C. Cripps. 2016. "Ferrite toroidal core with a trifilar wound RF broadband transformer design for tracking generators in wideband code division multiple access envelope tracking RFPA systems." Journal of Electromagnetic Waves and Applications 30, no. 5: 599-611.

Conference paper
Published: 01 December 2015 in 2015 IEEE International Conference on Electronics, Circuits, and Systems (ICECS)
Reads 0
Downloads 0

This paper presents an enhanced time-domain modulated waveform measurement and engineering system. The measurement system is based around a standard sampling oscilloscope and consists of a test set which integrates both RF and IF measurement and engineering, merging the capabilities of DC, CW, and multi-tone measurement system. The aim of the system is to extend the design role of waveform measurement and engineering into the multi-tone domain allowing optimization of power amplifiers under more realistic operating conditions akin to those found in modern day wireless systems. A GaN transistor has been measured, and results are presented that highlight the capabilities and applications of the system.

ACS Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. Modulated waveform measurement and engineering system. 2015 IEEE International Conference on Electronics, Circuits, and Systems (ICECS) 2015, 252 -255.

AMA Style

Muhammad Akmal Chaudhary, Jonathan Lees, Johannes Benedikt, Paul Tasker. Modulated waveform measurement and engineering system. 2015 IEEE International Conference on Electronics, Circuits, and Systems (ICECS). 2015; ():252-255.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2015. "Modulated waveform measurement and engineering system." 2015 IEEE International Conference on Electronics, Circuits, and Systems (ICECS) , no. : 252-255.

Journal article
Published: 14 October 2014 in Journal of Circuits, Systems and Computers
Reads 0
Downloads 0

This paper presents a fully automated time domain, waveform measurement system, capable of measuring multi-tone waveforms up to a frequency of 14 GHz. Multi-tone waveform measurement capabilities will prove useful in enhancing the understanding of the response of devices under realistic operating conditions, and allow for detailed investigation into device problems leading to memory effects. The system, which is based around a standard sampling oscilloscope, is capable of measuring all four traveling waves simultaneously. It is a cost effective solution, capable of capturing high quality measurement data, it consists of two test sets one to measure RF components of the signal and one to measure IF components, which are then recombined before being measured by the sampling oscilloscope. Vector error correction is applied to the measured data to fully calibrate the system to the device plane, ensuring any dispersion in the connecting hardware is removed. A multi-tone waveform sampling method is employed, ensuring the waveforms are captured in the most efficient manner. Device results are presented showing the multi-tone voltage and current waveforms at the device plane. Some useful applications of the system are demonstrated and explained.

ACS Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. MULTI-TONE WAVEFORM MEASUREMENT SYSTEM ENABLING CHARACTERIZATION OF MICROWAVE DEVICES. Journal of Circuits, Systems and Computers 2014, 23, 1450141 .

AMA Style

Muhammad Akmal Chaudhary, Jonathan Lees, Johannes Benedikt, Paul Tasker. MULTI-TONE WAVEFORM MEASUREMENT SYSTEM ENABLING CHARACTERIZATION OF MICROWAVE DEVICES. Journal of Circuits, Systems and Computers. 2014; 23 (10):1450141.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2014. "MULTI-TONE WAVEFORM MEASUREMENT SYSTEM ENABLING CHARACTERIZATION OF MICROWAVE DEVICES." Journal of Circuits, Systems and Computers 23, no. 10: 1450141.

Conference paper
Published: 01 December 2013 in INMIC
Reads 0
Downloads 0

The inter-modulation distortion products vary in amplitude and asymmetry due to the effects of baseband and 2 nd harmonic impedance. This paper presents an investigation into the relationship between the IMD asymmetries caused by baseband impedance variations and looping or hysteresis that can sometimes appear in the dynamic transfer characteristics of microwave power devices when subjected to modulated excitation. Here, the investigations are carried out on 2W GaN HFET bare die device characterized at 2.1GHz, and using IF active load-pull to quantify the role of baseband impedances on observed hysteresis in the dynamic transfer characteristics. Analysis is performed in envelope domain in order to more effectively reveal the DDT's sensitivity to electrical baseband memory effects.

ACS Style

Muhammad Akmal Chaudhary; Zulifqar Ali Memon; Jonathon Lees; Johannes Benedikt; Paul Tasker. Investigation of baseband electrical memory effects on the dynamic characteristics of power transistors. INMIC 2013, 106 -109.

AMA Style

Muhammad Akmal Chaudhary, Zulifqar Ali Memon, Jonathon Lees, Johannes Benedikt, Paul Tasker. Investigation of baseband electrical memory effects on the dynamic characteristics of power transistors. INMIC. 2013; ():106-109.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Zulifqar Ali Memon; Jonathon Lees; Johannes Benedikt; Paul Tasker. 2013. "Investigation of baseband electrical memory effects on the dynamic characteristics of power transistors." INMIC , no. : 106-109.

Journal article
Published: 19 August 2013 in Journal of Circuits, Systems and Computers
Reads 0
Downloads 0

This paper reports a refined multi-tone waveform measurement system for the robust characterization and optimization of nonlinear microwave devices when driven by broadband multi-tone stimuli. This enhanced system has the ability to present specific, constant broadband impedances, not only at baseband (IF) frequencies, but also at RF frequencies, particularly, around the carrier and significant harmonics. This functionality is key in studying the effects of out-of-band impedance termination on both short and long-term electrical memory effects. Achieving such comprehensive impedance control across wide modulation bandwidths is also critical in allowing the "emulation" of emerging power amplifier modes and architectures, and the subsequent waveform characterization of devices operating in these complex and often dynamic impedance environments. Initially, the baseband load-pull capabilities of the enhanced measurement system are experimentally demonstrated through the measurement of adjacent channel power (ACP) behavior of a class AB biased 10 W GaN HEMT, in response to a varying baseband load. Complete baseband and RF impedance control is then demonstrated through the emulation and analysis of a modulated Class-J impedance environment, which interestingly highlights the presence of separate optimum baseband impedance conditions necessary for the suppression of individual IM products.

ACS Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. MULTI-TONE MEASUREMENT SYSTEM WITH THE STATE-OF-THE-ART ACTIVE IF AND RF LOAD-PULL CAPABILITY. Journal of Circuits, Systems and Computers 2013, 22, 1 .

AMA Style

Muhammad Akmal Chaudhary, Jonathan Lees, Johannes Benedikt, Paul Tasker. MULTI-TONE MEASUREMENT SYSTEM WITH THE STATE-OF-THE-ART ACTIVE IF AND RF LOAD-PULL CAPABILITY. Journal of Circuits, Systems and Computers. 2013; 22 (7):1.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2013. "MULTI-TONE MEASUREMENT SYSTEM WITH THE STATE-OF-THE-ART ACTIVE IF AND RF LOAD-PULL CAPABILITY." Journal of Circuits, Systems and Computers 22, no. 7: 1.

Article
Published: 01 July 2013 in IET Microwaves, Antennas & Propagation
Reads 0
Downloads 0

A simple analogue technique called auxiliary envelope tracking, or AET, is presented, which is shown to be capable of improving the efficiency of a radio frequency power amplifier (RFPA). This AET signal is an amplified envelope signal that supplies the drain port of the RFPA. The concept of AET is explained and a theoretical background for the technique is presented. The main feature of this technique lies in the separation of the DC and AC components of the tracking signal. This allows for a very simple and low-cost tracking generator design that consists of a simple source follower amplifier and an RF broadband transformer. A practical system has been implemented and the measured results are obtained for WCDMA signals. A measurement on the realised system shows a 50% improvement in the drain efficiency at average output power of 33 dBm of a 25 W GaN. This substantial improvement is achieved at a competitive WCDMA signal with peak-to-average envelope power ratio of 9.17 dB.

ACS Style

Zubaida Yusoff; Jonathan Lees; Muhammad Akmal Chaudhary; Vincenzo Carrubba; Heungjae Choi; Paul Tasker; Steve C. Cripps. Simple and low‐cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications. IET Microwaves, Antennas & Propagation 2013, 7, 802 -808.

AMA Style

Zubaida Yusoff, Jonathan Lees, Muhammad Akmal Chaudhary, Vincenzo Carrubba, Heungjae Choi, Paul Tasker, Steve C. Cripps. Simple and low‐cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications. IET Microwaves, Antennas & Propagation. 2013; 7 (10):802-808.

Chicago/Turabian Style

Zubaida Yusoff; Jonathan Lees; Muhammad Akmal Chaudhary; Vincenzo Carrubba; Heungjae Choi; Paul Tasker; Steve C. Cripps. 2013. "Simple and low‐cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications." IET Microwaves, Antennas & Propagation 7, no. 10: 802-808.

Conference paper
Published: 01 April 2013 in 2013 IEEE International Wireless Symposium (IWS)
Reads 0
Downloads 0

This paper presents an enhanced active baseband load-pull capability that allows constant, frequency independent baseband load environments to be presented across wide modulation bandwidths. This capability is critical in allowing the effects of baseband impedance variation has on the performance of nonlinear microwave devices, when are driven by broadband multi-tone stimuli, to be fully investigated. The experimental investigations were carried out using a 10W GaN HEMT device, under 9-carrier complex multi-tone excitation.

ACS Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. Reduction of baseband electrical memory effects using broadband active baseband load-pull. 2013 IEEE International Wireless Symposium (IWS) 2013, 1 -4.

AMA Style

Muhammad Akmal Chaudhary, Jonathan Lees, Johannes Benedikt, Paul Tasker. Reduction of baseband electrical memory effects using broadband active baseband load-pull. 2013 IEEE International Wireless Symposium (IWS). 2013; ():1-4.

Chicago/Turabian Style

Muhammad Akmal Chaudhary; Jonathan Lees; Johannes Benedikt; Paul Tasker. 2013. "Reduction of baseband electrical memory effects using broadband active baseband load-pull." 2013 IEEE International Wireless Symposium (IWS) , no. : 1-4.