| 1. |
- Fritzin, Jonas, et al.
(författare)
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Phase Predistortion of a Class-D Outphasing RF Amplifier in 90 nm CMOS
- 2011
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Ingår i: IEEE Transactions on Circuits and Systems - II - Express Briefs. - 1549-7747 .- 1558-3791. ; 58:10, s. 642-646
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Tidskriftsartikel (refereegranskat)abstract
- This brief presents a behavioral model structure and a model-based phase-only predistortion method that are suitable for outphasing RF amplifiers. The predistortion method is based on a model of the amplifier with a constant gain factor and phase rotation for each outphasing signal, and a predistorter with phase rotation only. The method has been used for enhanced data rates for GSM evolution (EDGE) and wideband code-division multiple-access (WCDMA) signals applied to a Class-D outphasing RF amplifier with an on-chip transformer used for power combining in 90-nm CMOS. The measured peak power at 2 GHz was +10.3 dBm with a drain efficiency and power-added efficiency of 39% and 33%, respectively. For an EDGE 8 phase-shift-keying (8-PSK) signal with a phase error of 3 degrees between the two input outphasing signals, the measured power at 400 kHz offset was -65.9 dB with predistortion, compared with -53.5 dB without predistortion. For a WCDMA signal with the same phase error between the input signals, the measured adjacent channel leakage ratio at 5-MHz offset was -50.2 dBc with predistortion, compared with -38.0 dBc without predistortion.
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| 2. |
- Björsell, Niclas, 1964-, et al.
(författare)
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Multi-tone design for out-of-band characterization of nonlinear RF modules using harmonic sampling
- 2010
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Ingår i: 2010 IEEE International Instrumentation and Measurement Technology Conference, I2MTC 2010. - Piscataway, NJ : IEEE Service Center. - 9781424428335 - 9781424428328 ; , s. 620-623
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Konferensbidrag (refereegranskat)abstract
- In this paper we evaluate the generation of a multi-tone set for characterizing the behavior of nonlinear radio frequency (RF) modules in its out-of-band when harmonic sampling is used as digitizer. The purpose is to provide the reader with a tool to select proper frequencies and record length for a given application and test-bed. The method is based on simulations and the use of Sidon sequences. The proposed method is applicable to sparse discrete frequency multi-tones.
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| 3. |
- Nader, Charles, 1982-, et al.
(författare)
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OFDM PAPR Reduction by Convex Optimization : A Power Amplifier Point-of-View
- 2010
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Ingår i: 2010 IEEE International Microwave Workshop Series on "RF Front-ends for Software Defined and Cognitive Radio Solutions". - : IEEE. - 9781424457519
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Konferensbidrag (refereegranskat)abstract
- In this paper we evaluate the application of convex optimization for PAPR reduction on OFDM 802.11a signal type. A radio frequency power amplifier is measured and characterized while excited by both original and optimized OFDM signals. A state-of-art test setup was used for the purpose. Improvements in power added efficiency, in-band errors, out-of-band spectral emissions are investigated for their relevance and a study of the power distribution in the excitation signal is evaluated.
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| 4. |
- Fors, K.M., et al.
(författare)
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Improved impulsiveness correction factor for controlling electromagnetic interference in dynamic spectrum access applications
- 2010
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Ingår i: IET Communications. - : IET Journals. - 1751-8628. ; 4:4, s. 437-442
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Tidskriftsartikel (refereegranskat)abstract
- Initiatives to open certain frequency bands for dynamic spectrum access (DSA) are ongoing. Examples are the wireless access policy for electronic communications services and white spaces coalition. A key issue in DSA is how to measure occupancy and interference in an open frequency band to decide whether or not it can be used for a certain service. Such measurement must be easy to perform and provide a result that can be used as decision metric. An earlier proposal, based on a so-called impulsiveness correction factor, with this purpose has been shown to work properly if the interference is dominated by a single pulsed signal. In this study, the former approach is extended to the case in which the interference signal consists of a multiple of interference signals. This extension is shown as a closed expression involving only parameters that can be determined from an interference measurement.
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| 5. |
- Landin, Per N., et al.
(författare)
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Power Amplifier Behavioral Modeling Performance Comparison of the LSNA and the Modulation-Domain System
- 2008
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Ingår i: 72ND ARFTG MICROWAVE MEASUREMENT SYMPOSIUM - TIME DOMAIN AND FREQUENCY DOMAIN MEASUREMENT. - New York : IEEE. - 9781424422999 ; , s. 73-78, s. 73-78
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Konferensbidrag (refereegranskat)abstract
- The performance of power amplifier behavioral models depends strongly on the performance of the system used to measure the amplifiers. In this study two different systems with nonlinear measurement capability are used to model a commercially available PA. One system is a large-signal network analyzer (LSNA) and the second system is a modulation-domain system (MDS) consisting of a vector signal generator and a vector signal analyzer. The PA was tested with multitone and WCDMA signals and behavioral models were extracted from the measured data. The evaluation criteria normalized mean square error and weighted error spectral power ratio or adjacent channel error power ratio were then computed to compare the performance of the models from the two systems. Cross-validation between the systems, using data from one system to obtain the model and validating its performance with data from the other system, shows that the model performance is mainly affected by the used validation data. Validating the performance of models from the LSNA with data from the MDS indicates that the identified models have almost the same performance as the MDS-identified models, i.e. it does not matter which system is used to identify the models. Cross-validation using a WCDMA-signal and multitone signal from the different systems shows that the normalized mean square error is mainly affected by modeling imperfections introduced by using another signal type. WESPR and ACEPR show a certain difference in performance with somewhat lower values for the MDS. The behavior of the two systems can be explained by different noise levels.
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| 6. |
- Medvedev, Alexander, et al.
(författare)
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Nonlinear dynamics and entrainment in a continuously forced pulse-modulated model of testosterone regulation
- 2018
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Ingår i: Nonlinear dynamics. - : Springer Netherlands. - 0924-090X .- 1573-269X. ; 94:2, s. 1165-1181
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Tidskriftsartikel (refereegranskat)abstract
- Dynamical behaviors arising in a previously developed pulse-modulated mathematical model of non-basal testosterone regulation in the human male due to continuous exogenous signals are studied. In the context of endocrine regulation, exogenous signals represent, e.g., the influx of a hormone replacement therapy drug, the influence of the circadian rhythm, and interactions with other endocrine loops. This extends the scope of the autonomous pulse-modulated models of endocrine regulation to a broader class of problems, such as therapy optimization, but also puts it in the context of biological rhythms studied in chronobiology. The model dynamics are hybrid since the hormone metabolism is suitably captured by a continuous description and the control feedback is implemented in a discrete (i.e., event-based) manner by the hypothalamus of the brain. It is demonstrated that the endocrine loop with an exogenous signal entering the continuous part can be equivalently described by proper modifications in the pulse modulation functions of the autonomous model. The cases of a constant and a harmonic exogenous signal are treated in detail and illustrated by the results of bifurcation analysis. According to the model, adding a constant exogenous signal only reduces the mean value of testosterone, which result pertains to the effects of hormone replacement therapies under intact endocrine feedback regulation. Further, for the case of a single-tone harmonic positive exogenous signal, bistability and quasiperiodicity arise in the system. The convergence to either of the stationary solutions in a bistable regime is shown to be controlled by the phase of the exogenous signal thus relating this transition to the phenomenon of jet lag.
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| 7. |
- Chistiakova, Tatiana, et al.
(författare)
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Nonlinear system identification of the dissolved oxygen to effluent ammonia dynamics in an activated sludge process
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier B.V.. - 2405-8963. ; 50:1, s. 3917-3922
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Tidskriftsartikel (refereegranskat)abstract
- Aeration of biological reactors in wastewater treatment plants is important to obtain a high removal of soluble organic matter as well as for nitrification but requires a significant use of energy. It is hence of importance to control the aeration rate, for example, by ammonium feedback control. The goal of this paper is to model the dynamics from the set point of an existing dissolved oxygen controller to effluent ammonia using two types of system identification methods for a Hammerstein model, including a newly developed recursive variant. The models are estimated and evaluated using noise corrupted data from a complex mechanistic model (Activated Sludge Model no.1). The performance of the estimated nonlinear models are compared with an estimated linear model and it is shown that the nonlinear models give a significantly better fit to the data. The resulting models may be used for adaptive control (using the recursive Hammerstein variant), gain-scheduling control, L2 stability analysis, and model based fault detection.
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| 8. |
- Hosseinzadeh Dadash, Amirhossein, 1986-, et al.
(författare)
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Adaptive Finite Horizon Degradation-Aware Regulator
- 2023
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Ingår i: Recent Developments in Model-Based and Data-Driven Methods for Advanced Control and Diagnosis. - : Springer. - 9783031275401 - 9783031275395 ; , s. 123-132
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Bokkapitel (refereegranskat)abstract
- Predicting the failure and estimating the machine’s state of health is information that supports the production planning and maintenance management systems to increase productivity and reduce maintenance and downtime costs. However, controlling the degradation in the machines will improve the system’s reliability and resilience and make high-level decisions more accurate and reliable. To control the degradation in the machines, time should be included in the cost function as a variable, which alters the markovian properties of the system dynamic. In this article, we include the degradation cost in the quadratic cost function of the infinite horizon controller and calculate the optimal feedback according to the dynamics of the degradation using dynamic programming. It will be shown that the infinite horizon control will convert to the finite horizon, and the controller will be able to control the degradation according to the desired degradation at the desired time. In the end, with the help of simulation, we show that the degradation controller can control the degradation in the MIMO systems.
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| 9. |
- Hosseinzadeh Dadash, Amirhossein, 1986-, et al.
(författare)
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Degradation Simulator for Infinite Horizon Controlled Linear Time-Invariant Systems
- 2023
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Ingår i: 16th European Workshop on Advanced Control and Diagnosis (ACD 2022), Nancy, France, November 16-18, 2022. - : Springer. ; , s. 155-164
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Konferensbidrag (refereegranskat)abstract
- Diagnosis, fault prediction, and Remaining Useful Life (RUL) estimation are among the predictive maintenance research subjects used for maintenance cost reduction. Using the available data with different machine learning methods, especially deep learning methods, the accuracy of estimation and prediction of faults and RUL have increased dramatically. However, due to the statistical nature of the machine learning methods and the limitations of available datasets, physically interpreting this information might be impossible. On the other hand, controlling the degradation and faults in the machines as the optimum predictive maintenance solution needs the physical interpretation of the method's outcome. In order to test the new process-based methods for degradation and fault control, datasets with more information are required (compared to available datasets). In this article, we introduce an open-source degradation simulator for linear systems. This simulator can simulate the degradation in closed-loop machines whose dynamics are known. It is also possible to simulate different degradation models for different system parts simultaneously by adding different processes and output noise to the system. This simulator can generate enough data to test new machine learning-based predictive maintenance methods.
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| 10. |
- Isaksson, Magnus, et al.
(författare)
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A synthetic vector network analyzing measurement system
- 2011
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - : Institution of Electrical Engineers (IEE). - 0018-9456 .- 1557-9662. ; 60:6, s. 2154-2161
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a synthetic vector network analyzing measurement system is presented. The system is based on a hardware set-up, including a signal generator and a vector signal analyzer, with the vector network analyzing functionality implemented in the software. The measurements of the proposed system demonstrated comparable performance in terms of accuracy and speed compared with a modern traditional vector network analyzer, but it is more flexible due to its inherent software implementation. The proposed system’s ability to measure nonlinear phenomena is addressed and discussed, and some preliminary results are given.
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