Browsing by Author "Ghannouchi, Fadhel M."
Now showing 1 - 19 of 19
Results Per Page
Sort Options
Item 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, EdwinTo 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.Item 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.Item 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, MohamadModern 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.Item 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, KartikeyaThe 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.Item Open Access Delta-Sigma Based Transmitters for GHz Wireless Radio Systems(2013-01-29) Ebrahimi, Mohammad Mojtaba; Ghannouchi, Fadhel M.; Helaoui, MohamedThis 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.Item Open Access Delta-Sigma Modulator for Wideband and Multi-Band Radio Systems(2014-01-30) Rahman, Sharif Abdur; Ghannouchi, Fadhel M.The proliferation of modern communication systems places stringent requirements on analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) to operate on wideband signals while being power and resource efficient. In this thesis, the utilization of delta-sigma modulators for wideband and multi-band applications in both the receiver and transmitter is addressed. The first model proposes a low-complexity frequency band decomposition-based parallel DSM ADC architecture which lowers the resource consumption considerably compared to the conventional QMF-FBD ADC and maintains an acceptable SNDR. An FPGA implementation and resource estimation of the proposed model was performed as a proof of concept. The second model presents a concurrent dual band DSM architecture for spectrum aggregation transmitter application and provides a comprehensive analysis of step-by-step design process. The quantization noise is shaped in this architecture enabling concurrent transmission of two signals with low in-band noise interference. Simulation was performed with two carrier frequency bands of LTE signals as proof of theory.Item 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, AbrahamThis 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.Item Open Access Efficiency and Bandwidth Extension of Digital Doherty Amplifiers Using Digital Signal Processing Techniques(2024-09-20) Khazani, Mohammad Hossein; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Nielsen, JohnIn this thesis, a comprehensive investigation into DDPAs was carried out. Initially, attention was directed towards phase adjustment and input power splitting, and they were explored for their impacts on efficiency and linearity. Through the utilization of complex gain splitting, which combines standalone power splitting and phase adjustment, efficiency enhancements of up to 9.7% were achieved for a 64-QAM modulated signal transmitted at the DDPA’s central frequency. However, this improvement came at the expense of the DDPA’s linearity performance. Subsequently, frequency-domain power splitting techniques were introduced. These algorithms aim to optimize splitting parameters to maximize efficiency and bandwidth but often encounter linearity issues observed in frequency-independent methods. To mitigate these issues, ACPR measurements were conducted using modulated signals, offering insight into the effects of splitting factors. An optimization algorithm was then presented, focusing on maximizing PAE and bandwidth (and gain flatness) improvement while maintaining linearity lower than that of the conventional Doherty mode by restricting ACPR growth. This algorithm shed light on the trade-off between PAE, bandwidth extension, and linearity. It was demonstrated that by adjusting the value of the desired flat gain, one or two goals of the optimization problem could be prioritized at the expense of others. Finally, RF measurements were undertaken to validate the effectiveness of the algorithm. PAE enhancements ranged from 4.16% to 6.1% at various carrier frequencies, while bandwidth extension varied between 85 and 105 MHz.Item Open Access Efficient Digital Predistortion for Next-Generation Wireless Systems Using Optimization and Signal Processing Techniques(2018-07-16) Abdelhafiz, Abubaker Hassan Babiker; Ghannouchi, Fadhel M.; Behjat, Laleh; Westwick, David T.; Helaoui, Mohamed; Sesay, Abu B.; Eriksson, ThomasAs consumers expect better and faster service and data-rates from wireless providers, the limits of existing wireless networks become more apparent. In response, the wireless communication industry steadily marches towards the next generation of network technology to meet this demand. The upcoming fifth generation (5G) of wireless networks promises connection speeds and data rates that are one hundred times faster than the existing networks, and vastly improved signal and connection quality. The path towards 5G however is not an easy one; as there are many significant challenges facing the design of radio frequency (RF) systems standing between the concepts of 5G, and its real-world implementation; such as the use of Massive Multiple-Input Multiple-Output systems, multi-band transmission and ultra-wideband signaling in the 5G standard. The move from the present fourth generation (4G) networks to 5G represents a fundamental paradigm shift in design methodology and theoretical concepts employed, which means that the current linearization and digital predistortion (DPD) techniques are not directly scalable to 5G. As such, a new generation of DPD methods suitable for the wireless networks of tomorrow and beyond is needed. The end goal of this thesis is to pave the road towards 5G by developing scalable and efficient DPD techniques applicable to 5G. This is achieved through approaching the three key aspects of 5G DPD and developing novel solutions for each: DPD model complexity reduction, MIMO DPD and multi-band DPD. Using mathematical knowledge, optimization techniques and signal processing methods, techniques for DPD complexity reduction, a scalable MIMO DPD that takes strong leakage between the different branches of MIMO transmitter into account, and a cost-effective technique for the mitigation of intermodulation distortion in multi-band systems are developed, and extensive measurements are performed to validate the theory for each of the various contributions. As a result, this work expands the horizon of knowledge in the three key areas of DPD research, and bringing the implementation of 5G RF one step closer to reality.Item Open Access Frequency Agile and Low Power Homodyne Radio Receivers(2018-05-29) Hasan, Abul; Helaoui, Mohamed; Belostotski, Leonid; Ghannouchi, Fadhel M.; Sesay, Abu-Bakarr; O'Keefe, Kyle Patrick Gordon; Wu, KeMore than 100 billion devices are expected to be connected wirelessly by 2020 as expected from the Internet of Things (IoT) and 5G deployments. Reconfigurability and sustainable power consumption are two of the major concerns to cope up with the expected changes. In the light of the above challenges, two low-power, frequency agile and broadband radio receiver architectures, namely, the six-port receiver (SPR) and the N-path passive mixer (P-M) receiver, have been explored in this thesis. First, a complexity reduced calibration approach for the SPR is developed that would reduce the power consumption of the SPR system. After analyzing the advantages and drawbacks of the SPR and the N-path P-M receiver architectures, a new quadrature phase shift frequency selective (QPS-FS) receiver architecture is proposed that attempts to retain the advantages of both the existing architectures while it tries to eliminate or minimize their drawbacks. The proposed QPS-FS receiver is a frequency selective architecture in which the desired band RF signal at the signal carrier frequency equal to the local oscillator clock frequency is frequency down-converted and quadrature (I/Q) demodulated while the in- and out-of-band blocker and interferer signals are reflected and collected that could be used for energy harvesting purposes. The thesis culminates in the proposal and implementation of a novel broadband, frequency reconfigurable, low power, blockers and system impairments tolerant energy harvesting radio receiver architecture that is frequency selective, concurrently utilizing the in-band RF signal for information decoding and the in- and out-of-band blocker and interferer signals for energy harvesting for increased battery-life or self-sustainable operation of the receiver system.Item Open Access GaN Monolithic Microwave Integrated Amplifiers for Space and Wireless Applications(2021-01-05) Abounemra, Ahmed Mohammed Elelimy Ramadan; Ghannouchi, Fadhel M.; Belostotski, Leonid; El-Sheimy, Naser; Helaoui, Mohamed; Bensmida, SouheilIn modern communication systems, such as the fourth-generation (4G) and fifth-generation (5G), the frequency spectrum needs to be fully utilized to support broadband applications and keep up with increasing user demand for high data rates. 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 the power dissipation of the PA would have a significant effect on the efficiency of the whole transceiver. Doherty power amplifiers (DPAs) based on gallium nitride (GaN) transistors are poised to play a leading role in wireless base stations and repeaters in achieving high power efficiency and in meeting the linearity requirements set by wireless network standards. Although DPAs are widely utilized in field-deployed 4G base stations, they still suffer from many limitations. These limitations are mainly related to hardware imperfections in the RF blocks of the Doherty PA, such as narrow bandwidth and the gain imbalance between the main and the peak branches. Also, the large size of the circuit, because of the use of λ/4 transformers in the output combining network, is considered a critical problem for broadband DPA design. To adequately overcome the limitations of the Doherty PA, a new design methodology for Doherty architecture based on three-port input and output networks topology is proposed in the first part of this thesis. The output three-port network performs the impedance matching from any load impedance to the optimum loads, for both main and peak transistors and combines the power delivered from the two devices at any power ratio. The input splitting network is proposed for matching the input impedances of the two transistors to the source impedance. The freedom in choosing the power division ratio of the input network, enables us to achieve a tradeoff between efficiency and linearity. An asymmetric two-stage broadband Doherty amplifier is implemented using a 0.25-um GaN HEMT MMIC process to validate the proposed topology. The second part of the thesis concerns the study and the design of a wide-band harmonic controlling network (HCN) based DPA, using a new output combining network to achieve higher power efficiency over the broadband operating frequency range. In this design, the frequency sensitivity of the impedance inverters was compensated to minimize the efficiency degradation across the designed bandwidth. In many microwave systems, like radar and satellite applications, unwanted high input power levels such as jamming and interfering signals, affect LNAs. One of the characteristics of LNAs, designed using GaN technology, is the ability to endure these power levels with no need for using a limiter in front of the LNA. The third part of this dissertation presents a survivability study of wideband GaN HEMT LNA. It was concluded that GaN LNA can sustain relatively very high input power overdrive before device performance degradation or failure.Item Open Access Implementation of Neural Network Adaptive Digital Pre-distortion for Wireless Transmitters(2015-11-19) Hasan, Md Mahmud; Ghannouchi, Fadhel M.An Artificial Neural Network, more precisely Real Valued Spatiotemporal Neural Network (RVSNN) based real time adaptive digital pre-distorter (DPD) is proposed and implemented on FPGA for the linearization of nonlinear dynamic wireless transmitter. Power amplifier is the core component of wireless transmitter, and is the source of all the nonlinearities and distortions. To alleviate these distortions, DPD, designed based on the inverse characteristics of power amplifier, is the key technology in 3G and beyond wireless communications. Though off-line DPD ameliorates system performance considerably, it is still dependent on changes in system temperature, voltage, load mismatch and average signal power. In this regard, real time DPD provides increased stability along with the standard linearity and inter-modulation distortion requirements. But the proposed online RVSNN model is very sensitive to hardware delay and hard to realize, thus offline RVSNN model is implemented on FPGA which provides identical performance to its MATLAB counterpart.Item Open Access Millimeter-Wave and Sub-Terahertz Parametric Harmonic Generation(2021-02-04) Zhang, Nan; Belostotski, Leonid; Haslett, James W.; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Barclay, Paul E.; Mirabbiasi, ShahriarThe theory of parametric harmonic generation is described in this thesis. It is shown that for Nth-order harmonic generation the time-varying parameter (P), such as elastance (S), capacitance (C), conductance (G), or resistance (R), exhibits N−1 periods of a sine wave under one sinusoidal pumping cycle, which is named sinusoidal representation of pumped parameters. The maximum conversion efficiency of reactive frequency multipliers is 1/N. The related P-V curves are described by the Chebyshev polynomials. Impulse representation of pumped parameters is also developed to represent a transient train of pulses to describe the resistive multipliers. Several circuits are designed to demonstrate the validity of the theory and explore the parametric circuits in millimeter-wave and sub-THz bands. A frequency tripler is designed in the 28-GHz 5G band, using the topology of symmetric antiparallel pair of series varactors to achieve about 24-dB conversion loss (CL), −8-dBm maximum output power (POUT), and 18% relative bandwidth (BW). Two reconfigurable frequency multipliers (RFMs) are designed based on antiparallel nMOS-varactor pairs (APNVP) and switched-capacitor varactor (SCV) pairs. The SCV can obtain the ratio of maximum-to-minimum capacitance as high as 20, almost 10 times better than that of MOS varactors. The SCV-based RFM demonstrates much better performance than the APNVP-based RFM. A resistive tripler based on an antiparallel diode-connected nMOS transistor pair is also designed and measured in the D-band, with wide 28% BW and −16 dBm POUT. The CL can be improved by increasing the non-linearity of the resistance by tuning the back-gate control voltage. A voltage-controlled inductor is proposed based on a transistor-controlled capacitor and demonstrated in a D-band injection-locked oscillator with a ≥16% tunable operating frequency range, dc power as low as 5.6 mW, and a compact 0.018-square-mm core size.Item Open Access Modelling and Design Methodology of High-Efficiency Harmonic Tuned Power Amplifiers for 5G Applications(2018-05-18) Sharma, Tushar; Ghannouchi, Fadhel M.; Helaoui, Mohamed; Kitchen, Jennifer; Alhajj, Reda; Fear, Elise C.; Vyas, Rushi J.Radio Frequency (RF) base station unit moves toward qualification of next generation gallium nitride devices to meet the expectation of fifth generation (5G) wireless communication transmitters. Critical to the enablement and the fulfilment of next-generation network energy efficiency, Power amplifiers (PAs) remain a centre of focus to RF power base station markets. With an immense increase in cellular traffic, the performance of PAs should be constantly improved in terms of power efficiency, linearity, and bandwidth. This thesis focuses on several aspects for enabling high efficiency and bandwidth for small cell PAs for 5G applications. A variety of PA design methodologies have been proposed and implemented to achieve state of the art performance. Innovative input and output controlled harmonic tuned PAs have been presented to enable application of advanced waveform engineering in RF base station products. Harmonic optimization techniques have been proposed for efficiency and bandwidth enhancement of the PA performance. For experimental validation, various prototypes for different peripheries, RF specifications, and targeted performance are fabricated using different technologies. The issues related to bandwidth extension, device reliability, and miniaturization of PA base unit are studied and mitigated. This thesis proposes a novel comprehensive analysis of harmonically tuned amplifiers with respect to input harmonic sensitivity, highlighting the significance of input and output controlled amplifiers and their impact on the linearity of gallium nitride (GaN) based high efficiency PAs. For the first time, this thesis presents class GF and GF-1 amplifiers which have demonstrated outstanding performance by simultaneously tackling both input and output harmonic. In particular, this work demonstrated methods for effective on wafer active load pull that minimizes the amount of time required on the measurement system, and how to directly achieve maximum efficiencies by a combination of fundamental, second, and third harmonic at load and source of the active device. The conventional problem of so-called 2nd harmonic efficiency “null”, has been addressed in this thesis. The study reveals new directions for harmonic load pull and design procedure for high-efficiency PAs, which enables PAs in context of wide bandwidth, high efficiency without compromising the quality of service.Item Open Access Non-linear Error Modeling for MEMS-based IMUs(2018-12-14) Radi, Ahmed; El-Sheimy, Naser; Sesay, Abu B.; Nassar, Sameh; Noureldin, Aboelmagd; Ghannouchi, Fadhel M.; Hamad, Ahmed M.The precise estimation of the position, velocity and orientation of a moving object with and without reception of satellite signals using low-cost sensors has always been a challenging task. Current navigation market is dominated by integrating satellite positioning, such as Global Navigation Satellite System (GNSS) with Inertial Navigation Systems (INSs) through Bayesian filters; e.g. Kalman Filter (KF). During satellite positioning signal outages, navigation information is provided using the inertial sensors, i.e. the gyroscopes and accelerometers of an Inertial Measurement Unit (IMU). Thus, the overall quality of integrated navigation systems is driven by inertial sensors errors. This thesis aims at improving inertial sensor stochastic error modeling to obtain better accuracy, especially in INS stand-alone mode. A common approach to model inertial sensor stochastic errors (sometimes known as stochastic noise) is a 1st order Gauss-Markov (GM) process where its parameters are estimated using the Autocorrelation sequence of the sensor static measurements output collected at room temperature. However, the stand-alone 1st order GM model has proven not to be the best model for several inertial sensors. Consequently. in this thesis different and better noise characterization approaches are proposed, developed and used for analyzing such inertial sensor stochastic noise. The stochastic characteristics of low-cost Micro-Electro Mechanical Systems (MEMS)-based inertial sensor errors and their changes according to temperature and platform dynamics variation using two different approaches, namely Allan Variance (AV) and Generalized Method of Wavelet Moments (GMWM), are investigated. Advantages and limitations of each method concerning the ability to 1) identify the latent random processes associated with the detected error model and 2) accurately estimate the parameters of each random process; are highlighted and used to provide justifications for the developments brought afterword. A new wavelet variance-based framework, as an extension to the standard GMWM, for multi-signal inertial sensor calibration is proposed and developed in this thesis, namely Multi-Signal GMWM (MS-GMWM) that allows to model complex composite stochastic processes. The proposed approach not only can improve the modeling of stochastic sensor errors by using multiple replicates from a calibration procedure but also allows to understand the properties of these stochastic errors to perform more efficient calibration and, consequently, improve the navigation performance. In addition, a Graphical User Interface (GUI) algorithm is developed to make the MS-GMWM available to the general user and to facilitate the calibration procedures of inertial sensor errors using several complex stochastic error models. The KF design accounting for inertial sensor complex stochastic error models is investigated including detailed mathematical explanation of both the prediction and update stages. A novel environmentally-dependent (i.e. taking into account dynamics and temperature changes) adaptive integrated navigation algorithm is developed in this thesis, which is adapted to switch between different stochastic error parameters values according to 1) the inertial sensor temperature and 2) the platform dynamics to limit the overall environmental-dependent effects. The performance of the constructed stochastic error models, when operated through the proposed adaptive integrated algorithm in the designed GUI platform filter presented with optional adaptivity features, is evaluated using field real INS/GNSS data with induced GNSS signal outages. Compared to the traditional 1st order GM model, results showed that considering more complex error models, based on dynamics and thermal data analysis, improves the positioning errors during GNSS signal outages by 32.36 - 51.19%, which shows the significant effect of the proposed algorithms in this thesis.Item Open Access A Novel, 2.4 and 5.8GHz Dual-band, 2-Stage RF-DC Charge-pump with Load-tuned Transmission Lines for DC Output Boost(2019-05-15) Li, Sichong; Vyas, Rushi J.; Ghannouchi, Fadhel M.; Nowicki, Edwin Peter; Belostotski, LeonidA dual-band, RF-DC charge pump without external matching network for wireless energy harvesting in 2.4 and 5.8 GHz bands is proposed. The first novelty here is in the use of optimal length transmission lines on the load side of the 4 half-wave rectifying stages that make up the 2-stage RFCP topology. Simulations and measurements show that doing so boosts the RFCP’s output voltage due to an induced standing wave at each diode’s input and gives the RFCP a 50Ω input impedance without needing an external matching network. The second novelty of this RFCP is the tuned secondary feed that connects the RFCP input to its 2nd stage to give dual-band performance. By tuning this feed such that the RFCP’s 2nd stage and 1st stage impedances in parallel have 0 reactance at 5.8 GHz, return loss resonance in the 5.8 GHz band is achieved in addition to the 2.4 GHz band.Item Open Access On the Spectral Efficiency and Energy Efficiency of the Cloud Radio Access Network Architecture(2017) Ghods, Fatemeh; Fapojuwo, Abraham O.; Ghannouchi, Fadhel M.; Behjat, Laleh; Dimitrov, Vassil; Pahlevani, Majid; Hafez, RoshdyProviding support for high consumer data traffic and maintaining high system efficiency are key requirements of the fifth generation (5G) wireless network design. The high costs associated with the widespread installation of the network base stations (BSs) and spectrum acquisition makes them impractical for accommodating the high traffic load. What is more, the continuous operation of the BSs also has a significant consequence in causing elevated levels of carbon dioxide (CO2) emissions. To meet the key requirements of high spectral efficiency (SE), maintain low levels of cost, and high energy efficiency (EE), cloud-radio access network (cloud-RAN) has been proposed as a promising architectural solution. Moreover, new waveforms (e.g., fillter bank multicarrier (FBMC)) have been suggested as alternatives to the traditional orthogonal frequency division multiplexing (OFDM) to satisfy the astounding growth in the traffic load. This thesis aims to enhance capacity and reduce the network power consumption. First, the effect of cooperative transmission in combination with the cloud-RAN architecture on network-level achievable data rate along with EE and SE is studied. Mathematical tools from stochastic geometry are utilized, to analytically characterize SE and EE. Moreover, the ability to increase the power savings is investigated by incorporating a tunable downlink distance-based fractional power control (D-FPC) mechanism into the cloud-RAN architecture. Using tools from stochastic geometry, the network-level coverage probability and EE are examined. Second, the throughput reliability/SE/EE of a cloud-RAN incorporating the D-FPC mechanism along with cooperative joint transmissions is analyzed by adopting a stochastic geometry-based approach. Lastly, taking into account feasibility of two-fold data rate improvement within FBMC waveform, this thesis studies and experimentally examines FBMC waveform to evaluate this new waveform and compares it with OFDM waveform. Moreover, the linearity requirements of power amplifier (PA) using memoryless and memory polynomial digital predistortion (DPD) techniques are also examined through a very nonlinear PA (Doherty) and a moderately linear PA (Class AB) to explore the behavior of OFDM and FBMC signals. Overall, this thesis provides critical insights to the cloud-RAN system designer for selecting appropriate architectural approach and waveform to achieve desired performance regarding energy, spectral, and PA efficiency.Item Open Access Radio over Fiber Transceiver's Architectures for Wireless and Satellite Communications(2021-02-22) Noweir, Mahmood; Ghannouchi, Fadhel M.; Oblak, Daniel; Fapojuwo, Abraham O.; Helaoui, MohamedThe development of the fifth-generation (5G), and beyond, of wireless communications motivates researchers to design innovative architectures in order to guarantee the delivery of data rate as high as 10 Gbps. The existing 4G wireless access architectures broadcast radio frequency (RF) signals below 6 GHz. This congestion in the available spectrum limits the data speed to a few hundred Mbps. Researchers investigated the option of using millimeter wave (mm-wave) between 30-300 GHz as wireless carriers to broadcast and transmit signals with data speed up to 10 Gbps and higher. The need for an efficient wire or wireless broadband link between base stations is vital to allow a variety of applications and services (like interactive HD TV, internet video, augmented reality, vehicle telematics, high-speed train, the wireless cloud office, etc.) to be delivered simultaneously and seamlessly. Using lasers in generating mm-wave carriers is still an active area of research since the 1990s, due to its overall design simplicity and efficiency. By modulating laser light, using a radio-frequency signal, it becomes possible to transmit the latter over standard optical fiber cables, for which the loss in the telecommunication band is as low as 0.2 dB/km. Radio-over- fiber (RoF) technology combines the advantages of radio and photonic devices. RoF technology, therefore, allows extending the distance between central stations and wireless end-users, thus maximizing the coverage of micro-cell and macro-cell based networks. In addition, photonics and RoF can be seen as enabling technologies to generate radio signals at mm-wave frequencies in a cost-effective manner. Hence, RoF technology will lead to reduced Capital Expenditure (CAPEX), and Operational Expenditure (OPEX), compared to traditional all-electronic networks. The electrical-optical-electrical conversion process in RoF links inevitably comes with impairments that degrade the signal quality. Simpler setups, using cheaper off-the-shelf components, can still lead to an acceptable performance by boosting the input RF signal power before optical modulation. Amplification of the RF signal carried by optical fiber is commonly adopted to minimize the impact of photo-detection noise on the dynamic range at the receiver. Unfortunately, this amplification causes the RoF system to behave non-linearly, leading to distortions during the electrical-optical-electrical conversion process that degrades the overall signal quality. To overcome this problem and linearize the RoF link, in this thesis, we propose a novel full-duplex RoF transceiver (TRx) architecture, augmented with an effective digital predistortion (DPD) technique to mitigate the non-linearities of the RoF TRx using a memory polynomial (MP) model. This thesis deals with the implementation of RoF TRx and provides solutions to some of the observed impairments in the electro-optical systems. In the first phase of the research project, the design of a single RoF fronthaul downlink transmitter is built and supported by experimental validation. The second phase of the project is conducted to enhance and upgrade the capability of RF signal generation and bandwidth of the RoF TRx. The third phase is focused on the establishment of a bidirectional link between central baseband unit (BBU) to remote radio head (RRH) and to integrate it with a free-space optics. The fourth phase is accomplished by building dynamic DPD models, which provide on-line feedback information from the RRHs through an established pre-calibrated observation path.Item Open Access Rational Function and Distributed Two Block Architecture based Models for the Mitigation of Various Imperfections in Direct Conversion Transmitters(2013-09-30) Aziz, Mohsin; Ghannouchi, Fadhel M.Nonlinearity in power amplifiers and in-phase and quadrature-phase (I/Q) imperfections in the transmitter are of enormous concern. Two models to alleviate these imperfections have been proposed. The first method employs a Rational Function based model for the joint mitigation of these impairments, while the second method is a Memory Polynomial based distributed two block model. The Rational Function model has an improvement of around 2 dB in NMSE and around 3 dB in ACEPR than the state of the art parallel Hammerstein based model. For the distributed two block model, we are able to reduce the complexity while maintaining reasonable performances. The number of coefficients and the number of floating point operations are reduced by around 17 percent, matrix conditioning is improved by 12-33 dB and the dispersion coefficient is reduced by 16-42 dB as compared to the previously proposed joint modulator and power amplifier nonlinearity compensation technique.