PRISM :: Browsing by Author "Ghannouchi, Fadhel"

Browsing by Author "Ghannouchi, Fadhel"

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Open Access
A LINC Transceiver for Enhanced Power Transmission in Wireless Systems
(2008-01-27) Abd Elaal, Mohamed; Ghannouchi, Fadhel
A 2×1 LINC transceiver based on linear amplification using nonlinear components (LINC) architecture for wireless systems applications is proposed. The layout of the new architecture is presented and the simulation results show that the overall power efficiency of this architecture is superior by more than 300% when compared with that of a regular LINC amplifier. Also the adjacent channel power ratio (ACPR) is lowered to −64.2 dBc, compared to −26.1 dBc for regular LINC, which improves the system immunity against complex gain imbalances between LINC branches.
Open Access
A Hybrid RSS/TOA Method for 3D Positioning in an Indoor Environment
(2012-03-01) Tiwari, Smita; Wang, Donglin; Fattouche, Michel; Ghannouchi, Fadhel
This paper investigates 3D positioning in an indoor line of sight (LOS) and nonline of sight (NLOS) combined environment. It is a known fact that time-of-arrival-(TOA-) based positioning outperforms other techniques in LOS environments; however, multipath in an indoor environment, especially NLOS multipath, significantly decreases the accuracy of TOA positioning. On the other hand, received-signal-strength-(RSS-) based positioning is not affected so much by NLOS multipath as long as the propagation attenuation can be correctly estimated and the multipath effects have been compensated for. Based on this fact, a hybrid weighted least square (HWLS) RSS/TOA method is proposed for target positioning in an indoor LOS/NLOS environment. The identification of LOS/NLOS path is implemented by using Nakagami distribution. An experiment is conducted in the iRadio lab, in the ICT building at the University of Calgary, in order to (i) demonstrate the availability of Nakagami distribution for the identification of LOS and NLOS path, (ii) estimate the pass loss exponent for RSS technique, and (iii) verify our proposed scheme.
Open Access
A multi-port measurement system for large-signal characterization of microwave devices
(2011) El-Deeb, Walid Saber Abdel Aleam Ibrahim; Ghannouchi, Fadhel
Open Access
Advanced Digital Signal Processing Techniques for Linearization of Multi-band Transmitters
(2014-04-28) Younes, Mayada Fawzy; Ghannouchi, Fadhel
Due to the increasing demands for large capacity and high performance wireless transmitters, multi-band/multi-standard transmitter architectures play an important role in modern communication. Thus, advances in the design techniques of radio frequency (RF) power amplifiers (PAs) have promoted it to use single multi-band PA and RF components in order to concurrently process multiple input signals located in different frequency bands. In this dissertation, different RF imperfections are investigated and compensated for in multi-band wireless communications systems. Thus, a comprehensive analysis and different digital signal processing (DSP) solutions are proposed for distortion mitigation of different RF impairments in dual-band and tri-band transmitters. A novel Feedforward Hammerstein model/DPD is proposed for the accurate characterization of the dynamic, nonlinear behavior of RF PAs. Indeed, the performance of different DPD linearizers is affected by the imperfections of the up-converters in the transmission path and down-converters in the feedback path. Therefore, a complexity-reduced compound DPD is proposed for the compensation of the impairments stemming from the quadrature modulators and PA nonlinearity in single-band transmitters. This study is extended for multi-band transmitters and the nonlinear distortion in case of dual-band transmitters is analyzed. Indeed, the problem of modulator imperfections is more highlighted in multi-band transmitters. Therefore, a dual-input truncated Volterra DPD is proposed for the joint mitigation of dual-band PA distortion in the presence of modulator imperfections. A theoretical analysis of the nonlinear distortion in the concurrent tri-band PA has been given, and a three-dimensional (3-D) DPD is presented for the linearization of tri-band PA. The analysis is further extended in order to include the effects of the phase distortion in tri-band transmitters. Indeed, the transmitter wideband phase variation effects will affect the transmission quality and needs to be compensated for. Therefore, a novel 3-D phase-aligned DPD is proposed that takes into account both the compound amplitude and phase variation effects in a concurrent tri-band transmitter. Finally, in order to reduce the computational complexity of multi-band DPDs, a novel multi-branch DPD is proposed for the linearization of dual-band transmitters. The proposed model is based on a distributed polynomial basis function with a radial pruning approach.
Open Access
Advanced Doherty Power Amplifier Architectures for Broadband and Multistandard Wireless Transceivers
(2013-01-25) Darraji, Ramzi; Ghannouchi, Fadhel
Power amplifiers (PAs) have always been a pivotal front-end building block in wireless communication transmitters. As signal modulation schemes become more spectrally efficient and cellular traffic increasingly intense, the radio frequency (RF) performance of PAs should be constantly improved. This can be achieved by improving the analog circuit design of the PA and by including additional software and system features to balance energy consumption and performance. This thesis focuses on several aspects related to power efficiency enhancement and bandwidth extension of wireless Doherty PAs using baseband digital signal processing (DSP) techniques. A variety of digital signal conditioning algorithms are proposed to enable optimal Doherty PA operation at and beyond its nominal frequency bandwidth. An innovative dual-input Doherty PA architecture is also presented in this work to enable the implementation of these advanced DSP techniques. Analog circuit design and optimization approaches are investigated and proposed for the enhancement of Doherty PA performance. Experimental implementation is carried out to validate the proposed techniques. Critical issues related to complex gain imbalance as well as energy waste within the RF building blocks of the Doherty PA are studied and mitigated. Two advanced methodologies, namely digital adaptive phase alignment and digital adaptive input power distribution, are developed to effectively address the above-mentioned problems. The frequency response of Doherty PAs is analyzed; and, a novel digital domain based precompensation mechanism is derived to mitigate the bandwidth limitations of Doherty PAs, resulting in substantial bandwidth extension. An original architecture of a digitally equalized Doherty PA based RF front-end is proposed to allow the use of Doherty PAs in the context of wide bandwidth and multistandard radios.
Open Access
Advanced signal processing techniques for impairments compensation and linearization of siso and mimo transmitters
(2010) Bassam, Seyed Aidin; Ghannouchi, Fadhel
Modern wireless communication systems achieve higher data rates and better link reliability by using complex modulation and transmission techniques which add more constraints on the acceptable amount of distortions and nonlinearities in radio communication systems. RF transmitters are composed of linear and nonlinear circuits, which make them composite and dynamic nonlihear systems. As a result, the quality and performance of a wireless communication system depends significantly on the performance of the RF transmitter. This dissertation proposes novel advanced signal processing techniques for the estimation and compensation of distortions and nonlinearities in modern single-input, single-output (SISO) and MIMO transmitters. First, the focus was on the linearization and distortion compensation of a single-branch direct up-converter transmitter. Two sources of distortion - the modulator's inphase/ quadrature (1/Q) imbalance and the power amplifier - were investigated; and, two linearization approaches have been developed, in order to compensate for both sources of distortion and nonlinearity. The work was then extended to the linearization of multi-branch transmitters. It was demonstrated that nonlinear crosstalk could degrade the overall performance of a transmitter. A new matrix memory polynomial technique was introduced to develop an accurate forward model and to employ in the development of a new crossover digital predistortion linearization algorithm in MIMO Transmitters. The last topic of the dissertation concentrates on the linearization and distortion compensation of dual-band and multi-carrier transmitters. With conventional digital predistortion linearization techniques, the linearization of dual-band and multi-carrier transmitters must meet the sampling rate requirement of analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), which should be at least equal to the Nyquist sampling rate of the signal multiplied by the order of the nonlinearity. In a multicarrier and dual-band system with a broad frequency offset between the two carrier frequencies, this sampling rate requirement would be a big challenge. A novel multi-cell processing architecture is proposed that was developed to selectively compensate for the nonlinearities and distortions of the transmitter in different frequency bands, which significantly reduces the required sampling rate. Based on this new architecture, two linearization architectures were developed to compensate for the inter-band and intraband distortions of dual-band and multi-carrier transmitters.
Open Access
Advanced signal processing techniques for rf impairments and nonlinear distortion compensation in wireless transceivers from software defined radio perspective
(2011) Bhattacharjee, Shubhrajit; Leung, Henry; Ghannouchi, Fadhel
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
Artificial neural networks for modeling and digital predistortion for software defined transmitters
(2012) Rawat, Meenakshi; Ghannouchi, Fadhel
The overall objective of this thesis is to develop and analyze efficient and robust artificial neural network methodologies and distiibuted structures for complete transmitter modeling and its practical use as digital compensation solution for nonlinearity and hardware impainnents in wireless transmitters for software defined radio Applications. A suitable feedforward topology namely real valued focused time delay neural network is proposed and various nonlinear optimization algorithms are implemented to achieve best perfonnance in the presence of different power amplifiers and signals. While conventional digital predistortion (DPD) techniques focus mostly on power amplifiers and are dependent on signal statistics, the proposed linearization is more robust to signal statistics and generic in the sense that it adapts to any change in the input data even in the presence of modulator gain/ phase imbalances and DC offsets. Although highly robust, back propagation based feedforward neural network solutions have shortcomings such as high number of parameters to be stored leading to higher digital processing cost. Therefore, as an alternative cost cutting solution, this thesis ventures to modify conventional memory polynomial by applying layered structure similar to neural networks. With experimental results of different PAs, it is established that proposed three-layered-biased-memory-polynomial model enjoys better numerical stability and lower dispersion of coefficients which eventually helps in decreasing processing load on DSP and therefore can replace conventional memory polynomials providing similar performance. Above stated DPD techniques works in batch mode and when PA characteristics cannot be assumed constant over long time and constant adaptation of coefficients is needed, they may still lead to higher processing time therefore thesis further analyzes spatially distributed or lattice neural networks for adaptive digital compensation. It is reported that with its spatially distributed structure total processing cost is even lower than previously reported conventional adaptive nonlinear filters with reasonable performance especially in case of highly nonlinear PAs.
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
Behavioural modeling and digital predistortion of rf power amplifiers and wireless transmitters
(2010) Younes, Mayada; Ghannouchi, Fadhel
Open Access
Broadband and Energy-Efficient Power Amplifier Architectures
(2015-02-02) Akbarpour, Mohammadhassan; Ghannouchi, Fadhel
In this dissertation, power amplifier circuits and architectures are proposed that provide high efficiency for spectral-efficient high peak-to-average power ratio signals that are being used in modern communications systems. Using the proposed amplifier architectures and circuits high efficiency can be achieved in large frequency bandwidth. The TLLM (Transformer-Less Load-Modulated) amplifier proposed in this dissertation is an amplifier that has similar efficiency performance to the Doherty amplifier, while it does not utilize any power combiner at the output. In the proposed TLLM amplifier, the two amplifier branches are connected directly together and provide high efficiency for high PAPR (Peak-to-Average Power Ratio) signals. A complete analysis is given for designing the two amplifier branches in the TLLM amplifier and a complete and comprehensive design procedure is provided for designing broadband TLLM amplifiers. Three different amplifier prototypes are also implemented using the TLLM architecture showing its performance and capability. The second architecture proposed in this dissertation is a Doherty amplifier that utilizes three-port input and output networks. The analysis and flexible design procedure for designing a Doherty amplifier with three-port input/output networks is provided. The proposed analysis and design procedure can be used to design a Doherty amplifier with any output power ratio from the branches, and power division between the branch inputs. The proposed amplifier eliminates the need for any impedance inverter and offset lines at the input or output of the amplifier. In the next part, a new biasing technique is proposed for transistors. It is shown that using this new biasing, transistors exhibit completely different behaviors from the conventionally biased transistors that can be used for different purposes. Two of the applications are studied in this dissertation. First, a multi-branch amplifier is presented which can provide Doherty-like efficiency in a very large bandwidth. The second application is a linearizing driver amplifier. It is shown that using the proposed biasing scheme, a controlled amount of gain expansion can be achieved. The gain expansion can be used to compensate for the gain compression of the conventional power amplifiers to improve the amplifier's linearity without the need for additional linearizing circuitry or digital pre-distortion.
Open Access
Broadband RF Power Amplifier Design Methodology Using Sequential Harmonic Characterization
(2015-09-09) Taghavi, Hosein; Ghannouchi, Fadhel
Radio Frequency Power Amplifier (RFPA) amplifies the communication signals to the required power level for transmission. It is the most power consuming stage in a transceiver chain; consequently, any improvement in terms of dissipated power and efficiency of the power amplifier affects the overall power budget of the transmitter. Also, efficient performance of the RF power amplifier over extended ranges of frequency is one of the most challenging areas in implementing multi-band transmitter systems. In this thesis, a design methodology for multi-octave RF power amplifiers is presented based on the proposed sequential harmonic characterization. Compared to the conventional method, a more optimal performance is achieved using the proposed technique. To validate the proposed method, a broadband multi-octave power amplifier prototype was designed and fabricated using a Cree GaN HEMT device that exhibits drain efficiency of 53% - 64% across 0.7 – 4.0 GHz corresponding to the fractional bandwidth of 140%.
Open Access
Continuous-Mode Power Amplifiers for Broadband Power-Efficient Wireless Applications
(2015-02-02) Rezaei Nazifi, Saeed; Ghannouchi, Fadhel
Radio Frequency power amplifiers (PAs) are key elements in transmitters of wireless radios. Their main task is to amplify the signal and generate the required output power that allows transmission and radiation of the signal over the appropriate range. PA requirements mainly consist of the absolute achievable output power in conjunction with the highest possible efficiency and signal quality performances. Large bandwidths are also important requirements for PAs in contemporary and future communication systems. In this dissertation, a continuous-mode PA concept for achieving the best possible power and efficiency across wide bandwidths is investigated and a thorough study is carried out to assess the impact of practical device voltage limitations on the PA performance. A comprehensive analysis of the extended continuous class-B (class-J) mode is carried out and led to the development of a graphical tool, called "linearity contour", whose role is in identifying the PA load impedance design spaces. Taking advantage of the class-J PA and considering the impact of the output matching network's inductor loss, a methodology is proposed for the design of an integrated GaN class-J PA. To improve further the PA bandwidth, an on-wafer loadpull setup is arranged to measure the required load impedances. Measurement results of the PA show a 25\% bandwidth improvement in comparison with the conventional design approach. In addition, a design methodology to present the required class-J impedances is proposed and verified by designing a class-J PA with a die transistor. The study of the continuous-mode PAs is extended to the class-C mode by proposing a low- and a high-power continuous class-C mode and demonstrating experimentally their RF performances for a set of load impedances across certain design spaces. Examples of GaN MMIC PAs working in continuous class-C modes are provided to validate the proposed concept. Finally, to improve the linearity of PAs that present dual inflection points in their AM/AM characteristics, such as GaAs and GaN based amplifiers, an analog predistortion linearizer is proposed. By adjusting three Schottky and PIN diodes bias voltages in the implemented predistorter, the reverse AM/AM characteristic of a PA is synthesized and used to linearize the PA.
Open Access
Design and Implementation of an RTK-based Vector Phase Locked loop in a GNSS Software Receiver
(2017) Shafaati, Ahmad; Lachapelle, Gerard Jules; Lin, Tao; Moureldin, Aboelmagd MA; O'Keefe, Kyle Patrick Gordon; Ghannouchi, Fadhel; Aloi, Dan
GNSS carrier phase tracking is very demanding and challenging. The focus of this thesis is to develop and test an innovative tracking loop with potentially better performance than existing loops in harsh environments. The proposed Double-Difference VPLL (Vector-based Phase Locked Loop) is assisted with base station observations to estimate carrier phase and carrier Doppler measurements at the rover station using information from a stationary base station. The double differencing operation eliminates or substantially reduces spatially and temporally correlated errors between base and rover receivers, leading to increased robustness. A backup layer operating in parallel that provides reference satellite measurements and enhances receiver sensitivity in also introduced. It is shown that the two tracking loop parts have complementary performance in the sense that the backup layer has a lower tracking jitter at high C/N0 values whereas the VPLL has superior functionality at low C/N0 values. Comprehensive mathematical derivations and analyses are described to quantify operations and advantages. The theoretical models are supported by a number of simulation scenarios. The proposed method is also assessed with GPS L1C/A IF samples obtained through hardware-in-the-loop simulations. The proposed method is compared with two other tracking methods, namely the scalar-based and VFLL assisted PLL loops in terms of tracking sensitivity and the probability of an integer ambiguity fixed solution for carrier phase positioning. It is shown through extensive simulations and real data that this algorithm results in better carrier phase availability in degraded environments.
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
Efficiency Improvement of Multi-band Wireless Transceivers using Advanced Digital Signal Processing Algorithms
(2016) Kwan, Andrew; Ghannouchi, Fadhel; Helaoui, Mohamed; Sesay, Abu; Murari, Kartikeya; Zhu, Anding
Innovations in wireless communications has led to an exponential increase in the amount of users and data traffic. While highly spectral efficient modulation schemes and multi-band/wideband signal transmission enables high data traffic throughput, multiple challenges exist in the design and implementation of these transceivers, especially since these transceivers draw a high amount of power. Designers of wireless transceivers require more effort to increase their overall efficiency compared to the technology that exists for narrowband wireless transceivers. This dissertation introduces several techniques for optimizing wireless transceivers using advanced architectures and digital signal processing algorithms. The research focus is specifically for multi-band and wideband signal transmission, where design complexity increases over traditional transceiver architectures. A subsampling receiver architecture is used as an alternative for wireless receivers. This type of receiver enables direct sampling and digitization of RF signals without a downconversion stage, which reduces the complexity and increases the flexibility of the receiver. The subsampling architecture is utilized in a variety of applications, including as a feedback loop replacement in a dual-band digital predistortion (DPD) architecture. The results show that using subsampling can concurrently capture both signal bands at the same time while providing comparable linearization performance with conventional DPD architectures. DPD is a suitable technology for linearity enhancement and efficiency improvement of wireless transmitters. However, extension to wideband and multi-band topologies requires high digital sampling rates. A technique is introduced to reduce the sampling rate requirements in the feedback loop of the transmitter in a wideband and multi-band scenarios, where a reduction of up to twice the sampling rates can be achieved while able to produce accurate linearization performance. Envelope tracking increases the efficiency of the transmitter power amplifier (PA) at large output back-off power, performed by adjusting the voltage supplied to the PA based on the input signal characteristics. Using the digital signal processing techniques outlined in the thesis, the results obtained show that ET and DPD together can provide up to 9% efficiency improvement over just DPD alone, and are suitable for future generations of wireless transmitters.
Embargo
Fully Integrated GaN Front-End RF Modules for Advanced Spaceborne Synthetic Aperture Radars
(2023-09-15) Shekari Beyragh, Dawood; Ghannouchi, Fadhel; Pahlevani, Majid; Ghannouchi, Fadhel; Pahlevani, Majid; Belostotski, Leonid; Helaoui, Mohamed; Murari, Kartikeya; Okoniewski, Michal; Mirzavand, Rashid
RF front-end modules (FEMs) are vital in wireless communication and radar systems. FEMs comprise three fundamental components: a power amplifier (PA), a low noise amplifier (LNA), and a T/R switch. PAs use the highest power in wireless communication and radar systems and, jointly with the T/R switches, are responsible for most dissipations and heat generation. So, developing higher efficiency architectures for the PAs and T/R switches is crucial for reducing power consumption, extending the battery lifetime of the mobile systems, reducing the operating temperature, and improving reliability. Besides, new wireless communication applications, like 5G NR, and spaceborne synthetic aperture radars (SAR), demand FEMs with higher output power and operating frequency. Realizing these new applications using mature semiconductor technologies like Si and GaAs technologies is becoming more and more challenging while using GaN technology shows a prominent figure of merits. This thesis proposes two novel high-power GaN-based T/R switch architectures for spaceborne synthetic aperture radar applications. Then it describes the design process for three switches operating in C and X bands based on the proposed architectures using United Monolithic Semiconductors (UMS) GH25-10 0.25 μm GaN HEMT process. The designed switches’ simulation and measurement results are presented, showing a good agreement and verifying the desired performance of the proposed architectures. The second part of the thesis describes the development of a fully integrated C-band FEM using one of the designed switches, a PA, and an LNA developed in iRadio Lab. Due to the contractual requirements, asking for on-wafer testing of each FEM building block as a standalone component, these blocks were implemented with 50 Ω ports to be interconnected later when evaluating the full FEM performance. The on-wafer experimental results of the FEM individual building blocks show good agreement with the simulation results. As the last part, a breadboard was designed to assess the performance of the FEM in realistic operating conditions, and an on-wafer, low-loss, 50 Ω high-power interconnection method was developed to interconnect the T/R switch to the HPA and LNA. The breadboard measurement results agree with the interconnected FEM simulation results and show the outstanding performance of the FEM under large-signal conditions.