| 1. |
- Moghaddam, Mohammad Hossein, 1987, et al.
(författare)
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An additive noise modeling technique for accurate statistical study of residual RF hardware impairments
- 2019
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Ingår i: 2019 IEEE International Conference on Communications Workshops, ICC Workshops 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Hardware impairments are the inevitable limiting factors in radio frequency communication systems, and in particular in mm-wave, the impairments can severely affect system performance. In this paper, we propose an additive noise modeling technique for modeling and analyzing the residual hardware impairments, more accurately than previously done in the literature. We analyze the effects of joint residual phase noise and IQI in both transmitter and receiver by using additive noise modeling as a representation method and indicate how other impairments can be described in the same framework. We derive the signal to distortion plus noise ratio (SDNR) for both the joint and the individual effects of impairments and validate the formulations with simulations which also acknowledge the usefulness of the additive noise modeling as a mean for accurate hardware impairments study.
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| 2. |
- Moghaddam, Mohammad Hossein, 1987, et al.
(författare)
-
Statistical analysis of antenna array systems with perturbations in phase, gain and element positions
- 2019
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Ingår i: GlobalSIP 2019 - 7th IEEE Global Conference on Signal and Information Processing, Proceedings.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we statistically analyze the effect of hardware impairments on power pattern of antenna array systems. We consider a linear array and formulate the stochastic beam pattern as a function of variations in phase, gain and element positions. By deriving a closed-form expression for the variance of the power pattern, we express how the performance of antenna array can be degraded in each angle, allowing for investigation of the role of each parameter in the final power pattern variations. The proposed closed-form expression serves as a tractable tool for analyzing the effect of perturbations in different settings.
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| 3. |
- Moghaddam, Mohammad Hossein, 1987
(författare)
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Statistical Analysis of Hardware Impairments in Communication Systems
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis delves into the study of hardware impairments, the inevitable limiting factors in radio frequency (RF) communication systems, and their substantial influence on system performance. It addresses the incongruity between the often stringent requirements imposed by standards and the innate imperfections of analog circuits present in real-world RF electronics. Key hardware impairments, namely In-phase and Quadrature-phase Imbalance (IQI), phase noise, power amplifier (PA) nonlinearities, and antenna array perturbations, are studied, offering comprehensive overviews of their individual characteristics and their interactions with each other. The thesis also focuses on the effects of PA nonlinearity on widely used signal transmission optimizations, namely pulse shaping and matched filtering techniques. The nonlinear behavior of the PA, which can lead to signal distortions and inter-symbol interference, is shown to impact these techniques, posing considerable challenges to reliable communication. Moreover, a noticeable gap exists in the academic literature concerning an accurate analysis of the effect of PA nonlinearity on pulse shaping and matched filters. Such a gap underscores the need for a rigorous investigation into how these transmission optimizations are influenced by the PA's nonlinearity. As the first contribution of this thesis to the literature, in Paper A, a detailed study is conducted to comprehensively address these effects, bridging the existing knowledge gap and providing new insights into the interplay between PA nonlinearity, pulse shaping, and matched filter. As a complementary study to Paper A, Paper B delves deeper into the intricacies of PA nonlinearity, examining the impact of various waveforms and modulation orders. Within this exploration, a waveform factor is formulated, elucidating the interplay between waveform statistics, amplifier-specific parameters, and signal power in determining the total distortion power. Furthermore, a theoretical closed form for the nonlinear distortion, both in-band and out-of-band, is derived. This derivation reveals a notable finding: the distortion approximately distributes evenly between the in-band and out-of-band portions of the spectrum, offering a nuanced understanding of how PA nonlinearity manifests across adjacent frequencies. Moreover, in paper C, the effects of IQI and phase noise, in conjunction with PA nonlinearity, are analyzed, which can lead to a scrambled effect that further degrades the received signal quality. An additive noise modeling technique is introduced as a novel approach to effectively represent these combined effects. This technique facilitates accurate tracking of system performance under varying hardware impairment conditions, serving as a valuable tool to understand the collective impact on the system and develop mitigation strategies. The thesis further contributes to the field by providing statistical models for beam pattern variations due to antenna array perturbations in Paper D. The perturbations are random variations in phase, gain, and antenna element positions. These models enable an accurate projection of system performance under various conditions, helping to bridge the gap between theoretical design and practical implementation in RF communication systems. This comprehensive investigation of hardware impairments in communication systems paves the way for more resilient design strategies, enhancing the robustness and reliability of future RF communication systems.
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| 4. |
- Moghaddam, Mohammad Hossein, 1987, et al.
(författare)
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Statistical Modeling and Analysis of Power Amplifier Nonlinearities in Communication Systems
- 2022
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 70:2, s. 822-835
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Tidskriftsartikel (refereegranskat)abstract
- Hardware impairments in general and amplifier nonlinearity in particular severely limit the performance of communication links. This paper analytically provides statistical results on how a nonlinear amplifier affects the quality of signals in communication systems. In particular, we propose a statistical model that describes the nonlinear distortion as a function of the input signal’s average and instantaneous power and captures the pulse-shaping and matched filters’ effects. We show through simulations and complementary measurements that the proposed model can provide an authentic connection between the communication system parameters, power amplifier nonlinearity characteristics, and the communication system performance. It serves not only as a reliable model for nonlinear distortion analysis but also as a design tool that allows optimization of signal and filter characteristics with respect to nonlinear distortion.
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| 5. |
- Moghaddam, Mohammad Hossein, 1987, et al.
(författare)
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Statistical Study of Hardware Impairments Effect on mmWave 77 GHz FMCW Automotive Radar
- 2020
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Ingår i: IEEE National Radar Conference - Proceedings. - 1097-5659. - 9781728189420 ; 2020-September, s. 1-6
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Konferensbidrag (refereegranskat)abstract
- In this paper, we analyze the effects of hardware impairments on 77GHz FMCW automotive radar performance. Joint in-phase/quadrature imbalance (IQI) and phase noise effects on frequency-modulated continuous-wave (FMCW) radar transceiver front-end is modeled through statistical analysis of distortion and noise. We derive the signal to distortion plus noise ratio, constant false alarm rate, and range-Doppler sensitivity analysis for both the joint and the individual effects of impairments and validate the formulations with simulations. The represented modeling and analysis can be used in millimeter wave (mmWave) FMCW automotive radar signal processing algorithms for optimum transceiver design.
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