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Nonlinear Analysis and Digital Pre-Distortion of the SC-FDMA Signals in LTE Uplink SystemZhu, Changwen 01 January 2015 (has links)
Single-carrier frequency division multiple access (SC-FDMA) has become a popular alternative to orthogonal frequency division multiple access (OFDM) in multi-user communication on LTE uplink systems. This is primarily due to the low peak-to-average power ratio (PAPR) of SC-FDMA compared to that of OFDM. Long-term evolution (LTE) uses SC-FDMA on the uplink to exploit this PAPR advantage to reduce transmit power amplifier (PA) back-off in mobile user terminals. However, the latest generation of communication systems requires high power efficiency and a large quantity of capacity in transmitting mobile data, bringing out some other critical problems: 1) the nonlinearity of Radio Frequency (RF) power amplifiers inevitably affects the power efficiency. Working beyond the saturation point is the main reason for power amplifiers having nonlinear properties; 2) In order to obtain adequate capacity, wide bandwidth is applied to the latest communication systems. Since in previous systems the pre-distorter would focus on memory-less distortion with relatively narrow bandwidth, this change makes memory distortion become a serious issue, degrading the transmission quality in the wireless communication systems.
The intent of this thesis is to present nonlinear analysis of the SC-FDMA Spectrum with the RF power amplifier. Relevant mathematical models were considered and applied to the RF power amplifier in terms of intermodulation products and the third-order intercept point. The equivalent mathematical model is applied for the first time to SC-FDMA signals and with the previous formulation of the PA model, the derivation of the expressions for spectrum regrowth of amplified SC-FDMA signals was first established and finally simulated with Matlab software. The digital pre-distortion (DPD) technology was also applied to SC-FDMA signals for the first time in this thesis. An inverse intermodulation and Autoregressive Moving-Average (IM-ARMA) model was introduced to linearize the PA distortion with memory in the LTE uplink system. The DPD was finally implemented by Matlab R2010b.
Conclusions are drawn that amplified power emission levels can be expressed by the form of third-order intercept point (IP_3). The expressions for spectrum regrowth of amplified SC-FDMA signals have been verified for the first time with the comparison of simulation, measurement and calculation results. The effects of third order intermodulation have a greater impact than higher order components with respect to out-of-band emission power levels. Furthermore, the DPD algorithm reduced the spectrum regrowth of SC-FDMA signals by 12 dB. The proposed pre-distorter can effectively solve the distortion problem caused by the memory effect in RF power amplifier.
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Local Oscillator (LO)-Based Analog Signal Processing in Integrated Circuits and Systems: from RF to OpticsBinaie, Ali January 2022 (has links)
Wireless systems, ranging from radio to optical frequencies, typically comprise two domains: the signal path and the local oscillator (LO) path. While signal processing is conventionally performed in the signal path, more recently, techniques that exploit LO-based signal processing are becoming increasingly popular. LO-based analog signal processing can be utilized for solving fundamental problems and for improving the performance of systems in a wide variety of applications that span radio to optical frequencies. In this dissertation, I explore LO-based signal processing to enable new functionalities and enhance performance in electrical, optical, and electro-optical circuits and systems. In the electro-optical domain, I use LO-based signal processing to improve the performance of a long-range Frequency-Modulated Continuous-Wave (FMCW) Light Detection and Ranging (LiDAR) system.
As laser nonlinearity degrades the performance of ranging and imaging systems, it is essential to address this problem. In this dissertation, to linearize a laser, an integrated continuous-time Electro-Optical Phase-Locked Loop (EOPLL) is presented with a loop bandwidth equal to its reference frequency. Despite the high bandwidth, the proposed system is spurless, which is enabled by using Single-Sideband (SSB) and Harmonic-Reject mixing (HRM) techniques. These techniques are explored in Phase-Locked Loop (PLL) design for the first time. These features result in less area consumption and loss associated with the optical part of the system and increase the precision and accuracy of our long-range FMCW LIDAR significantly.
In the electrical domain, I use LO engineering to address some of the challenges that exist in three different electrical systems including mm-wave Multi-Input Multi-Output (MIMO) systems, ultra-low power RF systems, and wideband mm-wave systems. In the first project, to alleviate the challenge of supporting a high data rate Input/Output (I/O) interface in a large-scale tiled mm-wave MIMO array, a single-wire interface (SWI) is used in this dissertation, and a 60GHz 4-element scalable MIMO transmitter (TX) prototype is designed. In our work, we use frequency-domain multiplexing (FDM) to simultaneously support the signals of four MIMO channels. Then, in our proposed FDM, HRM is utilized to generate the different frequencies at which the various IF signals are multiplexed. This enables us to multiplex and de-multiplex the four modulated signals simultaneously to/from the single-wire using multiple phases of only one LO. The technique proposed in this research significantly reduces the number of lines needed for LO and signal routing in a massive MIMO system.
The second electrical project in this dissertation targets ultra-low power receivers at RF frequency. Wake-up receivers (WURX) are integral to reducing the power consumed by the main or primary RX in ultra-low power systems. Thus, the ability to share one antenna for both RXs is essential and results in a compact hybrid system. Furthermore, linearity and sensitivity are two fundamental criteria in these RXs. In order to improve the linearity of these systems, mixer-first RX architecture can be used for both RXs. However, mixer-first architecture has some drawbacks, like low gain and high noise figure (NF), which degrade the sensitivity of the system. Here, in our research, we implement a hybrid primary RX and WURX in which, first, a Quadrature Hybrid Coupler (QHC) is used to share one antenna between the two RXs and to achieve wideband input matching. Secondly, to address the problem of sensitivity in the mixer-first structure, we exploit a LO-assisted noise-canceling technique combined with a bottom-plate capacitor mixer-first receiver. This structure exploits implicit capacitive stacking which enables us to achieve passive LO-defined voltage gain, high linearity, and a low NF.
In the last electrical project in this dissertation, I present a novel frequency-interleaved (FI) channel aggregation architecture for wideband mm-wave systems that relaxes the requirements of their Analog-to-Digital/Digital-to-Analog Converters (ADC/DAC) and consequently reduces the total cost and power consumption. In our proposed architecture, the input bandwidth is channelized into four sub-channels, which are individually up/downconverted from/to baseband, where they can be digitized with multiple lower rate subconverters. We use the idea of HRM in the channelizer to simultaneously down(up)convert four sub-channels with only one LO. Four chips, including two mm-wave RX and TX chips and two baseband RX and TX chips, are designed and tested to show the functionality of the entire system as a transceiver.
Finally, I conclude this dissertation with an optical project which is a Silicon Photonic (SiP) simultaneous Mode and Wavelength Division (De)Multiplexer (MWD(De)MUX) for optical frequencies at C-band. I use an advanced 3D simulation tool, RSOFT software, to design and test this novel compact SiP structure. Our circuit uses a cascade of Mode Division Multiplexer (MDM) and Wavelength Division Multiplexer (WDM) stages for (de)multiplexing. A novel phase shifter introduced and used in this work is designed using two close waveguides on a CMOS compatible SiP platform, which results in reduced loss and size compared to conventional techniques.
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A Multi-Channel, Impedance-Matching, Wireless, Passive Recorder for Medical ApplicationsChen, Wei-Chuan 30 August 2019 (has links)
No description available.
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Device Simulation and Analytical Modeling of Weak Harmonic Distortion in Bulk Silicon Radio Frequency MOSFET SwitchesNiemeier, Dennis 13 April 2021 (has links)
Diese Dissertation behandelt schwache Nichtlinearitäten in Radiofrequenzschaltern, die auf Grundlage von CMOS-Transistoren realisiert werden. Der besondere Schwerpunkt liegt auf der analytischen Modellierung sowie der Simulation der Nichtlinearität mithilfe einer TCAD (Technology Computer-Aided Design) Software.
Die Nichtlinearität kann nach den verschiedenen Quellen klassifiziert werden: der Transistornichtlinearität und der Substratnichtlinearität. Für beide Bereiche werden umfassende Simulationen und analytische Modellierungen sowie Messungen präsentiert und interpretiert. / This dissertation treats weak nonlinearities in radio frequency switches that are realised based on CMOS transistor technology. A special focus lies on the analytical modeling and TCAD simulation of the nonlinearity.
The nonlinearity is sorted into substrate and transistor nonlinearity. For both nonlinear regions profound simulations, analytical modeling and measurements are presented and interpreted.
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Real-Time Beamformer Development and Analysis of Weak Signal Detection with Interference Mitigation for Phased-Array Feed Radio AstronomyBrady, James Michael 01 January 2016 (has links) (PDF)
In recent years, the Brigham Young University (BYU) Radio Astronomy Systems group has developed phased-array feeds and the data acquisition processing systems necessary to perform radio astronomy observations. This thesis describes the development and testing of a real-time digital beamforming system that reduces both the time required to process phased-array feed data and the disk space used to record this data compared to post-processing beamforming systems. A real-data experiment is also discussed in this thesis, which focuses on some of the data post-processing required for one of BYU's data acquisition systems.Radio-frequency interference mitigation techniques for phased-array feed radio astronomy have been studied for several years, but the effect that these techniques have on weak-signal detection is not well understood. This thesis provides analysis of a simulated weak-source observation for the Green Bank 20-meter telescope and BYU 19 element phasedarray feed with radio-frequency interference present. Interference mitigation techniques are shown to reduce the detectability of weak sources compared with the no interference case, but it is also shown that a weak source can be detected that would otherwise be masked by interference.
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Array Analysis of Radio Frequency Interference Cancelation Requirements for a Land Mine Detection SystemPratt, Devin Baker 16 November 2005 (has links) (PDF)
Land mines are a major humanitarian problem with millions of active mines in place around the world. Since these mines can have little metal in them, novel detection techniques are needed. Nuclear Quadrupole Resonance (NQR) is one such technique. Unfortunately, NQR is highly succeptible to radio frequency interference (RFI). A significant contribution of this thesis is the development of a custom, experimental data acquisition system designed and built specifically for capturing RFI at frequencies significant to NQR land mine detection systems. Another major contribution is the development of data analysis techniques for determining the number of reference antennas required to effectively cancel out RFI at frequencies and in environments typical of an NQR land mine detection system.
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Radio Frequency Energy Harvesting In Embankment DamsJärvström, William, Lundberg, Axel January 2022 (has links)
Energy harvesting can be used to consume the potential power of the surrounding environment. This harvesting can be done in different ways, some common energy harvesting modalities are vibrations, heat differences, solar power, and RF energy. In this Master Thesis, these different methods for harvesting energy are studied and the one that is the most suitable for an environment inside an embankment dam is further explored. If some energy harvesting modalities can operate well in that environment then it might be possible to monitor the embankment dam from the inside. The hope is to create an energy harvesting platform equipped with some suitable sensors which can be placed inside an embankment dam and collect data for a longer duration of time. Considering how an embankment dam is structured, it was concluded that the best possible energy harvesting method is wireless ultra-high frequency radio signals. An RF energy harvesting platform was created and tested, both in a laboratory and buried underground, mimicking the environment inside an embankment dam. These tests were measured and the results showed some promise that it is possible to use this energy harvesting method to power a sensor platform underground.
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Mobile Phone Radiation Deflects Brain Energy Homeostasis and Prompts Human Food IngestionWardzinski, Ewelina K., Jauch-Chara, Kamila, Haars, Sarah, Melchert, Uwe H., Scholand-Engler, Harald G., Oltmanns, Kerstin M. 02 June 2023 (has links)
Obesity and mobile phone usage have simultaneously spread worldwide. Radio frequency-modulated electromagnetic fields (RF-EMFs) emitted by mobile phones are largely absorbed by the head of the user, influence cerebral glucose metabolism, and modulate neuronal excitability. Body weight adjustment, in turn, is one of the main brain functions as food intake behavior and appetite perception underlie hypothalamic regulation. Against this background, we questioned if mobile phone radiation and food intake may be related. In a single-blind, sham-controlled, randomized crossover comparison, 15 normal-weight young men (23.47 ± 0.68 years) were exposed to 25 min of RF-EMFs emitted by two different mobile phone types vs. sham radiation under fasting conditions. Spontaneous food intake was assessed by an ad libitum standard buffet test and cerebral energy homeostasis was monitored by 31phosphorus-magnetic resonance spectroscopy measurements. Exposure to both mobile phones strikingly increased overall caloric intake by 22–27% compared with the sham condition. Differential analyses of macronutrient ingestion revealed that higher calorie consumption was mainly due to enhanced carbohydrate intake. Measurements of the cerebral energy content, i.e., adenosine triphosphate and phosphocreatine ratios to inorganic phosphate, displayed an increase upon mobile phone radiation. Our results identify RF-EMFs as a potential contributing factor to overeating, which underlies the obesity epidemic. Beyond that, the observed RF-EMFs-induced alterations of the brain energy homeostasis may put our data into a broader context because a balanced brain energy homeostasis is of fundamental importance for all brain functions. Potential disturbances by electromagnetic fields may therefore exert some generalized neurobiological effects, which are not yet foreseeable.
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Energy efficient radio frequency system design for mobile WiMax applications. Modelling, optimisation and measurement of radio frequency power amplifier covering WiMax bandwidth based on the combination of class AB, class B, and C operations.Hussaini, Abubakar S. January 2012 (has links)
In today's digital world, information and communication technology accounts for 3%
and 2% of the global power consumption and CO2 emissions respectively. This
alarming figure is on an upward trend, as future telecommunications systems and
handsets will become even more power hungry since new services with higher
bandwidth requirements emerge as part of the so called ¿future internet¿ paradigm. In
addition, the mobile handset industry is tightly coupled to the consumer need for more
sophisticated handsets with greater battery lifetime. If we cannot make any significant
step to reducing the energy gap between the power hungry requirements of future
handsets, and what battery technology can deliver, then market penetration for 4G
handsets can be at risk. Therefore, energy conservation must be a design objective at the
forefront of any system design from the network layer, to the physical and the
microelectronic counterparts. In fact, the energy distribution of a handset device is
dominated by the energy consumption of the RF hardware, and in particular the power
amplifier design. Power amplifier design is a traditional topic that addresses the design
challenge of how to obtain a trade-off between linearity and efficiency in order to avoid
the introduction of signal distortion, whilst making best use of the available power
resources for amplification. However, the present work goes beyond this by
investigating a new line of amplifiers that address the green initiatives, namely green
power amplifiers. This research work explores how to use the Doherty technique to
promote efficiency enhancement and thus energy saving. Five different topologies of
RF power amplifiers have been designed with custom-made signal splitters. The design
core of the Doherty technique is based on the combination of a class B, class AB and a
class C power amplifier working in synergy; which includes 90-degree 2-way power
splitter at the input, quarter wavelength transformer at the output, and a new output
power combiner. The frequency range for the amplifiers was designed to operate in the
3.4 - 3.6 GHz frequency band of Europe mobile WiMAX. The experimental results
show that 30dBm output power can be achieved with 67% power added efficiency
(PAE) for the user terminal, and 45dBm with 66% power added efficiency (PAE) for
base stations which marks a 14% and 11% respective improvement over current stateof-
the-art, while meeting the power output requirements for mobile WiMAX
applications.
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Investigation and Design of New, Efficient and Compact Load Modulation Amplifiers for 5G Base Stations. Design, Simulation, Implementation and Measurements of Radio Frequency Power Amplifiers Using Active Load Modulation Technique for More Compact and Efficient 5G Base Stations AmplifiersAbdulkhaleq, Ahmed M. January 2020 (has links)
High efficiency is an essential requirement for any system, where the energy
can be saved with full retention of system performance. The power amplifier in
modern mobile communications system consumes most of the supplied power
through the dissipated power and the required cooling systems. However, as
new services were added as features for the developed mobile generations, the
required data rate has increased to fulfil the new requirements. In this case, the
data should be sent with the allocated bandwidth, so complex modulation
schemes are used to utilise the available bandwidth efficiently. Nevertheless,
the modulated signal will have a Peak to Average Power Ratio (PAPR) which
increases as the modulation complexity is increasing. In this case, the power
amplifier should be backed off and designed to provide good linearity and
efficiency over high PAPR.
Among the efficiency enhancement techniques, the Doherty technique (Load
modulation technique) is the simplest one, where no additional circuity nor
signal processing is required. In this work, the theory of load modulation
amplifiers is investigated through two asymmetrical Doherty Power Amplifiers
(DPA) targeting 3.3-3.5 GHz were designed and fabricated using two transistors
(25 W and 45 W). In addition, more compact load modulation amplifiers
targeting sub 6-GHz bandwidth of 5G specifically 3.4-3.8 GHz is discussed
including the theory of implementing these amplifiers, where different amplifier
capabilities are explored. Each amplifier design was discussed in detail, in
which the input and output matching networks were designed and tested in
addition to the design of the stability circuit to make sure that the amplifier is
stable and working according to the specified requirements. The fabricated
circuits were evaluated practically using the available instrument test, whereas
Microwave Office software was used for the simulation purpose, each amplifier
was designed separately, where all the designed amplifiers were able to provide
the targeted efficiency at different back-off power points. Besides, some
additional factors that affect the designed load modulation amplifiers such as
the effect of the harmonics at the back-off and mismatching the amplifier is
discussed. / European Union’s Horizon 2020 research and innovation programme (SECRET)
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