PRISM :: Browsing by Author "Helaoui, Mohamed"

Browsing by Author "Helaoui, Mohamed"

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Open Access
Advanced Delta-Sigma Transmitter Architectures for High Performance Wireless Applications
(2017) Jouzdani, Maryam; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Belostotski, Leonid; Fear, Elise; Baudoin, Geneviève; Nowicki, Edwin
To satisfy the wireless market’s growing demand for higher data rates services and to maximize the bandwidth spectral efficiency, modern modulation schemes have been developed. Transmitting spectrally efficient non-constant envelope signals modulated by modern schemes necessitates designing highly linear and efficient transmitter systems for reaching the signal-to-noise ratio (SNDR) requirements and longer battery life. Delta-sigma modulator (DSM) based transmitters have the potential of good linearity performance and re-configurability for multi-standard applications. They also enable the use of high efficiency switching power amplifiers (PAs). This thesis was dedicated to enhancing the performance of DSM based transmitters. The first part of the thesis will focus on the design and evaluation of a novel high-pass (HP) DSM- based digital-IF transmitter architecture to address the in-band quantization noise problem and low coding efficiency in Cartesian HP and band-pass (BP) counterparts. As the most power consuming part of the transmitters, the design of highly efficient RF PAs has been the subject of several studies with different techniques being proposed to overcome this challenge. Dynamic control of the load impedance of the amplifier is a promising technique used in pulsed load modulation (PLM) PAs. Digital load modulation is realized in PLM PAs with the aid of the envelope delta-sigma modulator (EDSM) to enhance the efficiency in larger power back-off region while preserving the quality of the signal. The design and fabrication of a PLM PA with gate bias modulation for high power applications is the subject of the second part of this thesis. Employing the designed PLM PA, a digital DSM-based transmitter topology was realised for base-band applications. The transmitter was successfully tested with standard signals showing promising results. In the next step, it is shown that to further increase the efficiency of the PLM PA-based transmitters, it is possible to reduce the delta-sigma quantization noise and thus, the quality of the encoded signal by replacing the EDSM by a complex delta sigma modulator (CDSM). Based on this method, a novel transmitter architecture is proposed which benefits from CDSMs and PLM PAs for reaching the SNDR requirements and high efficiency performance at the same time.
Open Access
Advanced Doherty Transmitter Architectures for Wireless Communication Systems
(2021-02-02) Zhao, Yulong; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Belostotski, Leonid; Okoniewski, Michal M.
Power amplifier (PA) is a critical and energy-consuming building block in wireless communication transmitters. Base stations need to be efficient to minimize the electricity consumption. The wasted energy in wireless transmitters is converted to heat, which degrades the reliability of the system. Over the years, many efficiency enhanced PA architectures have been developed. Due to its good performance and simple structure, the Doherty PA (DPA) has been widely used in base station applications. However, conventional DPA focuses on the design of the amplifier module itself and the needed quarter wavelength transmission line limits the bandwidth of the DPA. In this thesis, first, the high efficiency Doherty transmitter based on the array antenna is proposed and its dynamic load modulation scheme is investigated. The design equations are derived based on the impedance matrix of the generalized load modulation network. The antenna array is then proposed and optimized to achieve the required impedance matrix. The measured results show good performances, which successfully verify the proposed theory and design equations. Second, the dual-branch dynamic reverse load modulation (RMDB) PA is analyzed. Different from the conventional DPA, the carrier PA is a current biased transistor and the peaking amplifier is a voltage biased transistor in the RMDB PA. The working principle of the dynamic load modulation is thoroughly analyzed. To verify the design theory, a Monolithic Microwave Integrated Circuit (MMIC) PA is designed and fabricated using the United Monolithic Semiconductors GH25 process. It is also the first reported MMIC that covers both 4th generation and 5th generation wireless communication frequency bands. Third, to further increase the efficiency of the RMDB PA, the harmonic control technique is implemented in a second MMIC PA design. The constraints of implementing harmonic control in RMDB MMIC PA are thoroughly discussed. By introducing extra offset lines in the carrier and peaking amplifier branches, the second harmonic control was successfully realized. Finally, optimal fundamental load modulation design space for Class-X harmonically tuned power amplifiers (PAs) was studied. Optimal fundamental load trajectories with different sets of second and third harmonic impedances are calculated and verified with harmonic load-pull measurement.
Open Access
Advanced transmitter architectures using switching mode power amplifiers
(2009) Helaoui, Mohamed; Ghannouchi, Fadhel
Open Access
Analysis and Design of a mm-Wave Wideband LTCC Patch Antenna for 5G Applications
(2022-12-23) Sadeghi, Maryam; Ghannouchi, Fadhel; Sharawi, Mohammad; Helaoui, Mohamed; Okoniewski, Michal
Fifth-generation mobile network (5G) has been planned to meet society's strong data advancement and accessibility. Since the current Long-Term Evolution (LTE) spectrum, i.e., 4G, is crowded and fragmented under 6 GHz, millimeter-wave frequency bands have attracted more interest in deploying 5G networks. The vast amount of unused spectrum in the mm-wave region can support higher data rates required in future mobile broadband access networks. For such significant data rates, wideband systems are required. An appropriate choice is an aperture-coupled patch antenna offering large bandwidth, good cross-polarization, and higher efficiency than conventional microstrip antennas. In mm-wave bands, the losses caused by materials, fabrication tolerances, measurement methodologies, and interconnections between feed lines and the antenna impact the overall performance of the antenna. Accordingly, the interest in fabricating mm-wave antennas using Low-Temperature Co-fired Ceramic (LTCC) is increasing. The LTCC fabrication process, in addition to lower substrate loss and higher fabrication tolerance, enjoys flexibility in realizing an arbitrary number of layers and ease of integration with other circuit components. In this work, a new aperture-coupled patch antenna with wide bandwidth at Ka-band and stable radiation patterns at 28 GHz for 5G applications has been designed, implemented, and tested with Dupont 9K7 LTCC technology. A parasitic patch, embedded air cavity, and large-size aperture improved the bandwidth. Moreover, the embedded air cavity enhanced the gain and reduced losses caused by the surface wave in the mm-wave band. A stripline feed was designed and used, allowing the antenna to be more easily integrated with a beamformer IC in the active array configuration. The impedance bandwidth achieved by the designed antenna is 32%, with a maximum gain of 9 dB at 28 GHz. A broadband Sub-Miniature-Push on Micro (SMPM) coaxial to stripline transition is also developed to feed the proposed antenna. A back-to-back configuration of the transition was fabricated and measured to validate the design. Experimental results showed a good agreement with the simulation results, with a return loss of better than 10 dB and an insertion loss of around 1 dB between 9 to 31 GHz.
Open Access
Analytical Modeling and Design of High-Efficiency Input-Output Harmonic Tuned Microwave Power Amplifiers
(2020-08-13) Dhar, Sagar Kumar; Ghannouchi, Fadhel; Zhu, Anding; Helaoui, Mohamed; Okoniewski, Michal; Vyas, Rushi
High efficiency power amplifier (PA) is an integral part of an efficient radio frequency (RF) transmitting system design. To enable modern and future wireless communication systems, the quest for efficient, wideband, and linear PA design techniques is ongoing. To cope with the stringent and contrasting requirements of modern wireless communication systems, it is important to consider the practical impairments like device nonlinearity, mismatch, mutual coupling, and channel temperature for high efficiency PA modeling, design, and reliable performance.In this thesis, power amplifier design methodologies have been comprehensively investigated by exploring and exploiting the input and output nonlinearities of the device. In particular, the impact of input nonlinearity on the PA performance is addressed comprehensively, and the efficiency minima phenomenon due to the input and output nonlinearity is demystified. As such, PA design methodologies for high efficiency broadband applications are proposed and verified with low/high power, and/or micro-wave/mm-wave applications. In addition to high efficiency PA design, linearity and output power performance are also investigated. A new input second harmonic design space is proposed in this thesis identifying trade-offs between PA efficiency and linearity performance. This approach led to a new PA topology designated as Class iF-1.In addition, the behavior of a PA and its linearizability by digital pre-distortion (DPD) technique under output mismatch and/or mutual coupling in a modern 5G wireless communication system is studied in this thesis. It has been observed that the PA linearizability is severely impacted by the PA-Antenna interface due to mismatch and mutual coupling. In this context, a new reflection aware unified PA behavioral modeling, and linearization approach is proposed under mismatch and mutual coupling. The proposed modeling technique and linearization approach is verified with a Class AB and a Doherty PA under wide range of output mismatch and/or mutual coupling conditions. Such robust linearization performance under diverse output mismatch and mutual coupling conditions is highly desirable for modern and future communication systems, which are subject to undergoing rapid fluctuations in antenna matching and cross-coupling conditions.
Open Access
Behavioral Modeling of Mixerless Three-Way Amplitude Modulator-Based Transmitter
(2017) Chatrath, Jatin; Helaoui, Mohamed; Ghannouchi, Fadhel; Vyas, Rushi
With an enormous rise in the application of smartphones, the need for highly efficient radio architectures has increased significantly. Modern communication systems will be adopting a 5th Generation (5G) standard for meeting the demands of the users efficiently. Analog mixers are a vital component of any transmitter and perform the necessary task of up-converting a signal. However, there are certain limitations associated with mixers including energy inefficiency. To eliminate these effects, three-way mixerless transmitter (TWMT) architecture has been proposed in the literature. Existing behavioral model for such an architecture make use of the digital splitters and combiners. In this thesis, we propose a Triadic Complex Memory Polynomial based model for the forward and inverse modeling of TWMT using analog combiners and splitters leading to a realistic scenario. Extensive simulations and measurements have been used to validate their performance. The model meet the desired design criteria concerning NMSE and ACLR.
Open Access
Blind Compensation of Impairments in Wireless Transceivers
(2018-07-24) Aziz, Mohsin; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Fapojuwo, Abraham Olatunji; Potter, Michael E.; Sawan, Mohamad
Modern wireless communication systems suffer from hardware imperfections that degrade the quality of transmission signals and make the detection of signal quite difficult at the receiver. This thesis focuses on the gain and phase imbalances caused by the modulators and demodulators and nonlinearity stemming from the transmitter power amplifier. Broadly, the contribution of this thesis is two folds: Blind solutions to mitigate the above mentioned hardware impairments of the wireless link through the proposal of a methodology based on the derivation of closed form expressions for the probability density functions (PDFs) of the signals in the presence of these impairments. In this regards, firstly, a PDF in the presence of modulator’s and demodulator’s in-phase and quadrature phase imbalances has been derived and validated. A maximum likelihood estimation of the imbalance parameters has been proposed to mitigate these imperfections. The proposed methodology has been evaluated using extensive simulations and measurements. To evaluate the static performance of the proposed methodology, 10 KHz modulated signal has been used. Measurement results show that an image rejection of greater than 30 dB can be achieved. For a larger bandwidth signal of 1 MHz, around 19 dB improvement in NMSE can be achieved using the proposed methodology, as compared to the uncompensated case. Secondly, a closed form PDF in the presence of gain and phase imbalances and the transmitter’s power amplifier nonlinearity has been derived and validated. A cumulative distribution function-based methodology has been adopted to mitigate the effects of power amplifier’s amplitude distortions. For the modulator’s impairments, a maximum likelihood estimation of the imbalance parameters has been used to estimate and compensate for the modulator’s imperfections. Using measurements, for a 3 MHz LTE signal, a normalized mean squared error and an error vector magnitude of -35 dB and 1.5% can be achieved, respectively.
Open Access
Chaos Modulation and Equalization for Robust Wireless Communications
(2022-01-28) Li, Boyuan; Leung, Henry; Messier, Geoffrey; Helaoui, Mohamed; Fapojuwo, Abraham; Kaddoum, Georges
This thesis focuses on using chaos modulation and equalization to enhance the robustness of wireless communication. Our contributions are three-fold: For the Industrial Internet of Things (IIoT), a quadratic ergodic chaotic parameter modulation (QECPM) is proposed. We use software-defined radios (SDRs) to show that QECPM is robust against timing synchronization errors, which have a major effect on performance. The bit-error-rate (BER) performance of QECPM in Nakagami-m fading channels is derived and verified by simulations. In a multipath-rich channel, QECPM demonstrates superior performance to conventional modulations. Furthermore, we show that retransmissions causes misaligned packets; however, when using the proposed receiver, the error bits are sparse enough to utilize the non-retransmission mode to maintain stable link rates. In a denoise-and-forward (DNNF) two-way relay system, the signals are asynchronous. For most denoising and decoding methods, precise estimation of the delay is required by the relay and end users, which is not always available. Using the ergodic property of chaotic signals, we propose to address the asynchronous problem using ergodic chaotic parameter modulation (ECPM) and guarding intervals (GIs). The theoretical BER performance is analyzed and verified by simulations. A relay selection method is also proposed for two-way relay systems with multiple relays to achieve improved performance compared to using all relays. Chaos modulation signals can be blindly equalized using phase space volume (PSV). A maximum likelihood-PSV (ML-PSV) estimation and the Cramer Rao Lower Bound (CRLB) are derived. The ML-PSV algorithm is applied to blind system identification of autoregressive (AR) and moving average (MA) models as well as equalization. A method for ECPM to identify the constructive/destructive channel is developed. The destructive channel effect can be mitigated using the proposed equalization. Our approach is validated using SDRs. Our results show that ECPM with ML-PSV equalization is more robust than comparing methods.
Open Access
CMOS Parametric Receiver Design for Short-Range and High Data-Rate Wireless Communication
(2021-02-03) Zhao, Zhixing; Magierowski, Sebastian; Belostotski, Leonid; Okoniewski, Michal; Helaoui, Mohamed; Barzanjeh, Shabir; Saavedra, Carlos
With the advent of 5G era, millimeter-wave technologies are drawing increased attention for fast-data-rate communication. Massive RF nodes deployments in 5G require inexpensive RF solutions. Recent RF developments associated with CMOS technologies promise to fulfill such requirements. However, millimeter-wave circuitry on CMOS is still expensive because achieving sufficient power gain requires advanced and costly CMOS nodes. In addition, the conventional way of seeking performance improvements, i.e. reliance on Moore’s law, is approaching its physical limits. In this thesis, parametric circuitry, as an alternative to RF performance enhancement at less-advanced nodes, is investigated. The parametric circuitry exploits varying capacitance to channel RF signal power from one frequency to another. During this frequency translation, an oscillator signal (known as Pump) power is added to the RF signal of interest so that the power gain is realized. The method is unlike a conventional transistor-based amplifier, which is essentially a DC-to-AC power converter. In addition to frequencies, the power gain of the parametric circuit can be tuned by the Pump signal as well. In this thesis, firstly the key technology, i.e. a variable capacitor, on CMOS technology is introduced and discussed. Then, the linearity of a CMOS 1-to-36 GHz parametric upconverter is analyzed. The agreement of the measurement and simulation results with the outcome of the analytic analysis demonstrates that the proposed harmonic analysis method can be relied on for the first-order analysis and quick grasp of design insights. Later, a sub-6GHz parametric downconverter is presented with a power gain of 24 dB. This circuit design shows a promising means to deploy parametric circuits at low-frequency bands.
Open Access
A Completely Integrated Warm-IF Receiver and a 10GS/s Analog-Delay Pipeline ADC for Radio-Telescope Applications
(2019-05-22) Zailer, Eugene; Belostotski, Leonid; Plume, René; Helaoui, Mohamed; Vyas, Rushi J.; Brown, Jo C.; Saavedra, Carlos E.
The Cerro Chajnantor Atacama Telescope (CCAT) Heterodyne Array Instrument (CHAI) radio-telescope is a large international effort involving University of Calgary, Kölner Observatorium für Sub-Millimeter Astronomie (KOSMA), University of Bonn, McGill University, and many others. The goal of the CHAI project is to upgrade the existing telescope capabilities to receive high-resolution images specifically in the 460 GHz and 830 GHz bands. The intended receiver system will have 128 (up to 256) antenna elements each requiring 128 independent receivers to be used. The Square Kilometer Array (SKA) is another major global effort to create the most sensitive radio telescope ever attempted. This radio telescope involves more than a hundred universities as well as industry. The SKA will potentially require millions of antenna elements, each requiring a cost-effective receiver to be implemented. This thesis presents a study of using a cost-effective CMOS technology to implement a complete receiver integrated on a single chip for CHAI and SKA telescopes. A receiver including a low-noise amplifier (LNA), a voltage-controlled oscillator (VCO), a mixer, and a variable-gain amplifier (VGA), based on CHAI design requirements, was implemented in 0.13 μm complementary metal-oxide semiconductor (CMOS) technology. An analog-to-digital converter (ADC) was implemented, based on the design requirements of the SKA, in 65 nm CMOS technology. A novel method for LNA wide-band noise optimization is developed and implemented in 0.13 μm CMOS technology. The design of the LNA is verified experimentally and meets the design requirements set by the CCAT project specifications. The LNA achieves a noise figure (NF) of <2.4 dB over the intended band of 4 GHz to 8 GHz with a gain of 18 dB. A novel method for VCO phase-noise (PN) optimization that simultaneously reduces VCO die-area and increases the available tuning range, was developed. The VCO is implemented in 0.13 μm CMOS technology and the novel optimization method is verified experimentally. The measured PN at 8 GHz is -134.3 dBc/Hz at a 1 MHz offset with a figure-of-merit (FOM) of 204 dBc/Hz. The ADC is developed using a novel topology that improves the speed performance of sub-ranging ADCs by removing the bottleneck and allowing both ADCs to run at full speed.
Open Access
Computational Drug Repositioning Based on Integrated Similarity Measures and Deep Learning
(2020-09-11) Jarada, Tamer N R; Rokne, Jon G.; Alhajj, Reda S.; Özyer, Tansel; Helaoui, Mohamed; Sadaoui, Samira
Drug repositioning is an emerging approach in pharmaceutical research for identifying novel therapeutic potentials for approved drugs and discover therapies for untreated diseases. Due to its time and cost efficiency, drug repositioning plays an instrumental role in optimizing the drug development process compared to the traditional \textit{de novo} drug discovery process. Advances in the genomics, together with the enormous growth of large-scale publicly available data and the availability of high-performance computing capabilities, have further motivated the development of computational drug repositioning approaches. Numerous attempts have been carried out, with different degrees of efficiency and success, to computationally study the potential of identifying alternative drug indications, which slow, stop, or reverse the courses of incurable diseases. More recently, the rise of machine learning techniques, together with the availability of powerful computers, has made the area of computational drug repositioning an area of intense activities. In this thesis, the integration of various biological and biomedical data from different sources to improve the quality of biomedical knowledge in the computational drug repositioning field is addressed. The main contribution of this thesis is four-fold. First, it provides a comprehensive review of drug repositioning strategies, resources, and computational approaches. Second, it develops an approach for identifying disease-specific gene associations, which can be further used as a resource for computational drug repositioning methods. Third, it proposes a robust framework that utilizes known drug-disease interactions and drug-related similarity information to predict new drug-disease interactions. Fourth, it introduces a novel integrative framework for predicting drug-disease interactions using known drug-disease interactions, drug-related similarity information, and disease-related similarity information. The two proposed frameworks leverage advanced similarity calculation, selection, and integration to understand the functional and behavioural correlation between drugs and diseases. Furthermore, they employ the most advanced machine learning tools in predicting hidden or indirect drug-disease interactions for potential drug repositioning applications.
Open Access
Concurrent Dual Band Six Port Receiver
(2014-01-31) Olopade, Abdullah Oluwatosin; Helaoui, Mohamed
Receiver front-ends have always been a critical component in wireless communication system design. Its performance and characteristics determines the quality and fidelity of the communication systems. Proliferation of communication protocols and standards however, require that the front-ends should become more flexible, multi-standard and reconfigurable. In addition, to enable higher communication throughput, there have been proponents of concurrent dual-band receiver front-ends to receive signals in more than one band simultaneously. Typical architecture for this concurrent multiband operation uses the front-end stack-up technique, which builds parallel receiver paths with each path dedicated to one frequency band. This increases complexity, power requirement, size and cost. The Six-Port receiver (SPR) is a low power and low complexity alternative to conventional homodyne receiver, which is multi-standard, flexible and easily reconfigurable. This thesis proposes the use of the SPR for a concurrent dual-band operation without any component duplication in the frequency down-conversion path.
Open Access
Data Structures, Algorithms and Applications for Big Data Analytics: Single, Multiple and All Repeated Patterns Detection in Discrete Sequences
(2017) Xylogiannopoulos, Konstantinos; Alhajj, Reda; Rokne, Jon; Pardalos, Panayote; Kawash, Jalal; Helaoui, Mohamed
My research work of the current thesis focuses on the detection of single, multiple and all repeated patterns in sequences. Many algorithms exist for single pattern detection that take an input argument (i.e., pattern to be detected) and produce as outcome the position(s) where the pattern exists. However, to the best of my knowledge, there is nothing in literature related to all repeated patterns detection, i.e., the detection of every pattern that occurs at least twice in one or more sequences. This is a very important problem in science because the outcome can be used for various practical applications, e.g., forecasting purposes in weather analysis or finance by detecting patterns having periodicity. The main problem of detecting all repeated patterns is that all data structures used in computer science are incapable of scaling well for such purposes due to their space and time complexity. In order to analyze sequences of Megabytes the space capacity required to construct the data structure and execute the algorithm can be of Terabyte magnitude. In order to overcome such problems, my research has focused on simultaneous optimization of space and time complexity by introducing a new data structure (LERP-RSA) while the mathematical foundation that guarantees its correctness and validity has also been built and proved. A unique, innovative algorithm (ARPaD), which takes advantage of the exceptional characteristics of the introduced data structure and allows big data mining with space and time optimization, has also been created. Additionally, algorithms for single (SPaD) and multiple (MPaD) pattern detection have been created, based on the LERP-RSA, which outperform any other known algorithm for pattern detection in terms of efficiency and usage of minimal resources. The combination of the innovative data structure and algorithm permits the analysis of any sequence of enormous size, greater than a trillion characters, in realistic time using conventional hardware. Moreover, several methodologies and applications have been developed to provide solutions for many important problems in diverse scientific and commercial fields such as Finance, Event and Time Series, Bioinformatics, Marketing, Business, Clickstream Analysis, Data stream Analysis, Image Analysis, Network Security and Mathematics.
Open Access
Delta-Sigma Based Signal Processing Techniques for Broadband Radio Applications
(2019-01-22) Ben Arfi, Anis; Ghannouchi, Fadhel M.; Sesay, Abu B.; Helaoui, Mohamed; Park, Chanwang; Murari, Kartikeya
The growing network coverage and the sharp increase in the number of devices in the wireless network have generated a great demand for browsing and accessing data, high-definition video, and streaming services without experiencing delays or interruptions. This is made possible by the high-speed connection and minimal latency achieved by efficient and reliable wireless network infrastructures. These networks are continuously evolving to serve huge numbers of users and satisfy the growing demand for data, while providing a good signal quality and maintaining a low power consumption. New techniques and designs of wireless devices are currently being developed to respond to the emerging applications requiring low power consumption, higher bandwidth, and minimum latency. This work focuses on enhancing the wireless transmitter performance by using the Delta-Sigma Modulation (DSM) technique. In fact, DSM-based transmitters have shown a relatively strong performance in terms of linearity and power efficiency. However, limitations on speed could degrade the overall performance and bandwidth. Research efforts have been focusing on DSMs as a promising solution to further enhance the overall efficiency of wireless devices. By proposing robust hardware implementation methods and preserving the linearity of the transmitter, the DSM topologies can match other existing transmitter topologies in terms of power efficiency while offering more flexibility when aiming at the design of Software Defined Radio (SDR) based transmitters. First, a general study on DSM basics and different DSM topologies is conducted. The study covers different types of DSMs classified by their transfer function, order and type: low-pass, high-pass, and band-pass. Different DSM-based transmitter topologies are presented, namely, the Cartesian, Polar, Envelope and the Complex Delta-Sigma Modulator (CxDSM) topologies. Also, the concept of using a multi-level DSM quantization has been investigated. Second, the impact of the undesired delays occurring during the hardware implementation is investigated. A post-compensation block is needed to cancel the effect of these delays and recover the correct DSM transfer function. Additionally, an implementation of an all-digital DSM-based transmitter for Software Defined Radio (SDR) applications was developed. The SDR transmitter is reconfigurable and has a lower latency compared to previous architectures. Furthermore, to improve the performance of DSMs and find a substitute for the COordinate Rotation DIgital Computer (CORDIC) based multi-level CxDSM, a multi-level complex quantizer implementation method on Digital Signal Processors (DSP) is proposed. The latter uses a look-up table (LUT) to generate quantized output samples. This method was proven to be robust and achieved a minimum latency. Third, an implementation of a multi-level DSM-based wireless transmitter is developed to preserve the power efficiency of the Switch Mode Power Amplifiers (SMPAs). For this purpose, a dual-branch three-level DSM was implemented and validated on a digital signal processing platform. Finally, a digital Intermediate-Frequency (IF) High-Pass DSM (HPDSM)-based transmitter is implemented and validated. By integrating a complex quantizer in the HPDSM-based topology, the performance is significantly improved. This topology maintains a low oversampling ratio, saves the processing resources while enhancing the quality of the output signal.
Open Access
Delta-Sigma Based Transmitters for GHz Wireless Radio Systems
(2013-01-29) Ebrahimi, Mohammad Mojtaba; Ghannouchi, Fadhel M.; Helaoui, Mohamed
This dissertation was dedicated to improve the performance of the delta-sigma based transmitters in terms of efficiency and bandwidth without compromising signal quality. Delta-sigma based transmitter, consisted of two main blocks; delta-sigma modulator (DSM) and switching-mode power amplifier (SMPA), is one of the new promising techniques for wireless transmitters. To enhance the transmitter efficiency, the efficiency of the SMPA and the efficiency of the DSM were both addressed in this thesis. At first, by using class F and F-1 SMPAs was improved by proposing an analytical approach to decrease the output harmonic matching network loss. It was proven that, decreasing the width of the stubs minimizes the matching loss. The idea was tested by designing an inverse class F SMPA at 2.45 GHz, using a 10-Watt GaN transistor. It was also possible to increase the efficiency of the delta-sigma based transmitters by reducing the DSM’s quantization noise and improving its coding efficiency. Two signal processing techniques to reduce the quantization noise were proposed. In the first technique, conventional I/Q Cartesian DSMs were replaced by a complex DSM with a complex polar quantizer, resulting in a lower quantization noise and consequently higher efficiency. In the second technique, a part of out-of-band quantization noise was removed, resulting in a quasi-pulsed signal with lower noise and consequently better efficiency. These two techniques are also combined to further improve the efficiency. In the next step, the bandwidth enhancement in delta-sigma based transmitter was addressed. In the first technique, similarly to the noise reduction technique, in-band noise filtering is applied to reduce the in-band quantization noise and accordingly decrease the oversampling ratio required to achieve the desired signal quality. Another technique to reduce the DSM clock speed and increase the bandwidth is parallel processing. By employing a parallel processing technique based on time interleaving, the signal bandwidth of the DSM was increased without increasing the clock speed. Based on the proposed parallel DSMs, and the SMPA, an all-digital transmitter topology for SDR application was introduced and a three-step procedure for designing the transmitter’s parameters was proposed.
Open Access
Design of Multi-band/Wide-band High Efficiency Power Amplifiers
(2018-04-18) Li, Xiang; Helaoui, Mohamed; Belostotski, Leonid; Kim, Bumman; Ghannouchi, F. M.; Fear, Elise C.; Alhajj, Reda S.
As an important component of the RF front-end in the transmitter, the power amplifier (PA) is used to convert the DC supply power into RF power. As the PA consumes most of the power in the transmitter, minimizing power dissipation of the PA would have a significant effect on the efficiency of the whole system. During recent decades, several works have been done to enhance the PA efficiency. However, there must be a trade-off between efficiency, linearity, gain, output power and bandwidth, which are five crucial attributes of the PA. With the development of the wireless communication system, multiple standards at different frequency bands are highly demanded to be integrated into one system while the increasing data rate requires a wide frequency spectrum and therefore broadband components. The multi-band/wide-band signals also lead to high peak-to-average power ratio. Thus, PAs are required to operate at multi-band/wide-band with high efficiency within a wide output power back-off (OPBO) range. For this reason, this thesis focuses on the PA theory and design method for multi-band, wide-band and wide-OPBO purpose. For the first time, a quad-band impedance inverter with arbitrary frequency ratio is proposed. Based on this impedance inverter, a concurrent quad-band Doherty has been designed at 0.75GHz, 1.75GHz, 2.65GHz and 3.55GHz with efficiency up to 50% at 6dB OPBO. For the first time, this thesis present a new theory for harmonically tuned PAs with maximally flat waveform, named class X PAs. The theory was developed for arbitrary harmonic tuning with arbitrary number of harmonics. The analytic close-form formulas for the voltage and current waveforms are provided. Design space for the Class-X PA with only first three harmonics is derived. To validate the theory, a wide-band PA has been designed with output power above 38dBm, efficiency higher than 70% over an octave bandwidth. The harmonic tuning method is also applied to the outphasing system in order to improve the efficiency. A harmonically tuned class-F outphasing system at 27.1MHz is designed with three third harmonic tuning cases to validate the theory. A harmonically tuned class-F-1 outphasing system at 2.14GHz is designed with efficiency of 68% at 6dB OPBO
Open Access
Design of Phase Shifters for Phased Array Antenna Applications
(2024-10-24) Jebeli Haji Abadi, Ali; Ghannouchi, Fadhel M.; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Belostotski, Leo; Fapojuwo, Abraham
This thesis presents a method for reducing the complexity of the I-Q phase shifter. This new method is based on the I-Q phase shifter architecture, where the input signal is divided into two orthogonal paths. By adjusting the amplitude of these two signals and then combining them, a signal with a phase difference relative to the input signal is obtained. The variable attenuators used in this method must be adjusted based on the required phase shift, and these attenuators are controlled by the system's control unit through multiple control lines. By reducing the number of control lines in this phase shifter, we effectively decrease the complexity and load on the control section. In this work, we first introduce a Voltage Variable Gamma Phase Shifter. This phase shifter requires only one control line and provides continuous phase variation. In this approach, the input divider is replaced with a circulator, and the two attenuators are replaced with a single variable resistor. The variable resistor is a PIN diode, controlled by a single control line. This phase shifter was fabricated and tested at 3.45 GHz with a bandwidth of 300 MHz. It provided approximately 95 degrees of phase change, with insertion loss less than 14 dB. The limitation of this method is the circulator, which prevents its use in Microwave Monolithic Integrated Circuits (MMIC). To address this issue, we have developed the next version of this phase shifter. The second step in this thesis involves modifying the Voltage Variable Gamma Phase Shifter to make it suitable for MMIC applications. To achieve this, we replace the input circulator with a coupler. This method has its own pros and cons. Although this version can be used in MMIC applications, we do not have control over both paths, which means we will lose the ability to vary the phase. In this configuration, since we have control over only 50 percent of the input signal, we will lose at least 50 percent of the phase variation. This phase shifter has been fabricated and tested at 3 GHz with a bandwidth of 400 MHz. The final step is the MMIC version of this phase shifter. Using a GaN substrate and 250 µm technology, we designed the MMIC phase shifter using the process design kit (PDK) from United Monolithic Semiconductor (UMS).This phase shifter provides a phase variation of 40 degrees and a bandwidth of 400 MHz at 3.5 GHz, with an insertion loss of less than 8 dB. The dimension of the final version of this phase shifter is 2 by 1.6 mm.
Open Access
Detecting and Fixing Emergent Behaviors in Distributed Software Systems Using a Message Content Independent Method
(2016) Hendijani Fard, Fatemeh; Far, Behrouz; Krishnamurthy, Diwakar; Moussavi, Mahmood; Helaoui, Mohamed; Bonakdarpour, Borzoo
Distributed software Systems (DSS) and Multiagent Systems (MAS) as a sub-class of DSS can provide efficient and cost effective solutions for a wide range of applications. The distributed functionality and/or control in these systems and the local view of the scenarios of the systems can lead to unexpected behavior during execution time, known as Emergent Behaviors (EB) and Implied Scenarios (IS), which was not evident in the requirements and design phase. The new scenarios that are implied to the system can degrade the quality of service and/or cause irreparable damage. Detecting and fixing EB/IS in the early phases, may save costs of software projects by a factor of 20 to 100. In this thesis, we are investigating a new methodology for modeling and analyzing the behavior of software components/agents in order to certify their behavior in advance. Our research questions are: Q1: Is there any methodology that can detect common EB/IS in DSS/MAS without modeling the internal information/knowledge used in software components/agents? Q2: Is there a general approach that can detect EB/IS without human interference and is fully automated? First, we devised a catalogue of the common EB/IS that can arise in DSS/MAS. One of the main advantages of this catalogue is categorizing the EB/IS based on the reasons of occurrence, which helps in devising specific algorithms to detect each type of EB/IS, and can lead to devising solution repositories. The other contribution of our work is devising new modeling based on state machines and social network analysis. This modeling is a general method and can be implemented fully automated. Also, we devised algorithms for detecting the agents that will not show EB/IS in the system as a pre-processing phase. For classes of EB/IS in the catalogue, the detection methodology is devised and recommendations on how to fix the problem are provided. The results of our work shows that all of the EB/IS in various case studies specified in the literature can be detected with our method. Moreover, a new EB/IS is introduced which only can be detected with our modeling.
Open Access
Digital Pre-Distortion for Radio Transmitters with Multiple Sources of Impairment
(2022-08) Motaqi, Ahmadreza; Helaoui, Mohamed; Ghannouchi, Fadhel; Mohammadi, Abbas; Fapojuwo, Abraham; Sesay, Abu B.; Abou Zeid, Hatem
Among the most important factors in wireless base-stations design are link speed and power efficiency. For a faster wireless connection, the MIMO beamforming technology, higher-order QAM signals, and wider bandwidth signals are used. To increase the power efficiency in transmitters, the PAs are pushed to operate in nonlinear regions where they present their highest power efficiency. These techniques increase in-band and out-of-band distortions of the MIMO wireless transmitters, resulting in signal quality degradation. To mitigate the introduced distortions to the transmitted signal, Digital Pre-Distortion (DPD) is used. However, the conventional DPD techniques cannot meet the strict timing requirements of 5G and 6G wireless connections. The transmitter nonlinearities are a function of various parameters such as input signal average power and ambient temperature and steering angle in the case of beamforming. This thesis studies the effect of ambient temperature and signal’s average power on high-power PAs and proposes a novel DPD technique to mitigate the effect of those parameters on the PA behaviour. In another research, the effect of beamforming on the transmitter performance in terms of signal quality and out-of-band distortions are studied. A novel angle inclusive DPD for beamforming application is introduced to remove beamforming-related distortions and enhance the signal quality. This technique provides an uninterrupted linearization at any beam direction. The developed algorithms are verified using a realistic MIMO beamforming setup designed in the laboratory. The measurement results have shown that by using the proposed technique, the signal quality is substantially improved when compared to state-of-the-art techniques.
Open Access
Direct Power Transfer Concept in Power Electronics Converters
(2022-01-28) Zareie Khabjani, Milad; Pahlevani, Majid; Nowicki, Edwin Peter; Helaoui, Mohamed; Zareipour, Hamidreza; Wood, David Howe; Belostotski, Leonid; Eberle, Wilson Allan Thomas
In this thesis, a family of power electronics converters is presented with a direct path for transferring the power from the input to the output. In this family, a technique for transferring the power is used which is called direct power transfer (DPT). In this technique, a portion of the power is transferred to the output directly, hence reducing the amount of power that needs to be processed by the semiconductors, and other passive components of the converter. Thus, the conduction losses are reduced, and the overall efficiency is improved. A coupled inductor is used on the input of the proposed converters that creates the direct power path, resulting in a reduction of the power passage in the active and passive components. Additionally, the coupled inductor current has a quasi-rectangular waveform, resulting in reduced peak and, root-mean-square values. Therefore, higher efficiency is gained and the voltage and current rating of the semiconductors are reduced. The DPT technique is applied in DC/DC and AC/DC converters. For DC/DC, the proposed DPT converter is isolated and can provide high performance for a wide range of operating conditions. The semiconductors on the primary side of the transformer operate with zero voltage switching (ZVS), and the semiconductors on the secondary side of the transformer operate with zero current switching (ZCS). Thus, both the switching and conduction losses are reduced. For AC/DC, an isolated bridgeless single-stage DPT converter with a high power factor is proposed. This converter has DPT capability and soft-switching performance over a wide range of operating conditions. In the proposed circuit topology, a bridgeless boost power factor corrector (PFC) is integrated with an isolated current-driven half-bridge DC/DC converter to achieve a bridgeless single-stage PFC structure. Additionally, a direct path is provided using a coupled inductor to directly transfer power from the input source to the output. The bridgeless structure and DPT capability result in reduced conduction losses, while the soft-switching operation almost eliminates the switching losses. Therefore, the proposed converter benefits from low losses and high efficiency. Mathematical analysis, extensive simulation, and experimental results are provided to verify the feasibility of the proposed circuits and demonstrate their superior performance.