| 1. |
- Khanzadi, M Reza, 1983, et al.
(författare)
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Calculation of the Performance of Communication Systems from Measured Oscillator Phase Noise
- 2014
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Ingår i: IEEE Transactions on Circuits and Systems I: Regular Papers. - 1549-8328 .- 1558-0806. ; 61:5, s. 1553-1565
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Tidskriftsartikel (refereegranskat)abstract
- Oscillator phase noise (PN) is one of the major problems that affect the performance of communication systems. In this paper, a direct connection between oscillator measurements, in terms of measured single-side band PN spectrum, and the optimal communication system performance, in terms of the resulting error vector magnitude (EVM) due to PN, is mathematically derived and analyzed. First, a statistical model of the PN, considering the effect of white and colored noise sources, is derived. Then, we utilize this model to derive the modified Bayesian Cramer-Rao bound on PN estimation, and use it to find an EVM bound for the system performance. Based on our analysis, it is found that the influence from different noise regions strongly depends on the communication bandwidth, i.e., the symbol rate. For high symbol rate communication systems, cumulative PN that appears near carrier is of relatively low importance compared to the white PN far from carrier. Our results also show that 1/f^3 noise is more predictable compared to 1/f^2 noise and in a fair comparison it affects the performance less.
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| 2. |
- Khanzadi, M Reza, 1983
(författare)
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Modeling and Estimation of Phase Noise in Oscillators with Colored Noise Sources
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The continuous increase in demand for higher data rates due to applications with massive number of users motivates the design of faster and more spectrum efficient communication systems. In theory, the current communication systems must be able to operate close to Shannon capacity bounds. However, the real systems perform below capacity limits, mainly due to channel estimation error and hardware impairments that have been neglected by idealistic or simplistic assumptions on the imperfections. Oscillator phase noise is one of the hardware impairments that is becoming a limiting factor in high data rate digital communication systems. Phase noise severely limits the performance of systems that employ dense constellations. Moreover, the level of phase noise (at a given off-set frequency) increases with carrier frequency which means that the problem of phase noise may be even more severe in systems with high carrier frequency.The focus of this thesis is on finding accurate statistical models of phase noise, as well as the design of efficient algorithms to mitigate the effect of this phenomenon on the performance of modern communication systems. First we derive the statistics of phase noise with white and colored noise sources in free-running and phase-locked-loop-stabilized oscillators. We investigate the relation between real oscillator phase noise measurements and the performance of communication systems by means of the proposed model. Our findings can be used by hardware and frequency generator designers to better understand the effect of phase noise with different sources on the system performance and optimize their design criteria respectively. Then, we study the design of algorithms for estimation of phase noise with colored noise sources. A soft-input maximum a posteriori phase noise estimator and a modified soft-input extended Kalman smoother are proposed. The performance of the proposed algorithms is compared against that of those studied in the literature, in terms of mean square error of phase noise estimation, and symbol error rate of the considered communication system. The comparisons show that considerable performance gains can be achieved by designing estimators that employ correct knowledge of the phase noise statistics. The performance improvement is more significant in low-SNR or low-pilot density scenarios.
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| 3. |
- Nopchinda, Dhecha, 1991
(författare)
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mm-Wave Data Transmission and Measurement Techniques: A Holistic Approach
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ever-increasing demand on data services places unprecedented technical requirements on networks capacity. With wireless systems having significant roles in broadband delivery, innovative approaches to their development are imperative. By leveraging new spectral resources available at millimeter-wave (mm-wave) frequencies, future systems can utilize new signal structures and new system architectures in order to achieve long-term sustainable solutions. This thesis proposes the holistic development of efficient and cost-effective techniques and systems which make high-speed data transmission at mm-wave feasible. In this paradigm, system designs, signal processing, and measurement techniques work toward a single goal; to achieve satisfactory system level key performance indicators (KPIs). Two intimately-related objectives are simultaneously addressed: the realization of efficient mm-wave data transmission and the development of measurement techniques to enable and assist the design and evaluation of mm-wave circuits. The standard approach to increase spectral efficiency is to increase the modulation order at the cost of higher transmission power. To improve upon this, a signal structure called spectrally efficient frequency division multiplexing (SEFDM) is utilized. SEFDM adds an additional dimension of continuously tunable spectral efficiency enhancement. Two new variants of SEFDM are implemented and experimentally demonstrated, where both variants are shown to outperform standard signals. A low-cost low-complexity mm-wave transmitter architecture is proposed and experimentally demonstrated. A simple phase retarder predistorter and a frequency multiplier are utilized to successfully generate spectrally efficient mm-wave signals while simultaneously mitigating various issues found in conventional mm-wave systems. A measurement technique to characterize circuits and components under antenna array mutual coupling effects is proposed and demonstrated. With minimal setup requirement, the technique effectively and conveniently maps prescribed transmission scenarios to the measurement environment and offers evaluations of the components in terms of relevant KPIs in addition to conventional metrics. Finally, a technique to estimate transmission and reflection coefficients is proposed and demonstrated. In one variant, the technique enables the coefficients to be estimated using wideband modulated signals, suitable for implementation in measurements performed under real usage scenarios. In another variant, the technique enhances the precision of noisy S-parameter measurements, suitable for characterizations of wideband mm-wave components.
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| 4. |
- Pérez-Penichet, Carlos, et al.
(författare)
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Poster abstract : Augmenting WSNs with interoperable 802.15.4 sensor tags
- 2017
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Ingår i: SenSys 2017 - Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems. - New York, NY, USA : Association for Computing Machinery, Inc. - 9781450354592
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Konferensbidrag (refereegranskat)abstract
- The sensing capabilities of most sensor networks are fixed at the time of deployment. Adding new sensing capabilities to such networks is a costly and cumbersome process. We present Passive Sensor Tags, battery-free sensing devices that could be used to extend the sensing capabilities of an existing network. Sensor tags feature our new 802.15.4 receiver design which is suitable for micro-power operation, making battery-free tags possible. Because our tags can both transmit and receive 802.15.4 frames there is no need for any modification to the deployed hardware. We present preliminary measurements of transmission and reception range.
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| 5. |
- Jang, Jeong Keun, et al.
(författare)
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Area-efficient scheduling scheme based FFT processor for various OFDM systems
- 2018
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Ingår i: 2018 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS 2018). - : IEEE. - 9781538682401 ; , s. 338-341
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents an area-efficient fast Fouriertransform (FFT) processor for orthogonal frequency-division multiplexing systems based on multi-path delay commutator architecture. This paper proposes a data scheduling scheme to reduce the number of complex constant multipliers. The proposed mixed-radix multi-path delay commutator FFT processor can support 128-, 256-, and 512-point FFT sizes. The proposed processor was synthesized using the Samsung 65-nm CMOS standard cell library. The proposed processor with eight parallel data paths can achieve a high throughput rate of up to 2.64 GSample/s at 330 MHz.
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| 6. |
- Abbaspour Asadollah, Sara, et al.
(författare)
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Evaluation of surface EMG-based recognition algorithms for decoding hand movements
- 2019
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Ingår i: Medical and Biological Engineering and Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 58:1, s. 83-100
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Tidskriftsartikel (refereegranskat)abstract
- Myoelectric pattern recognition (MPR) to decode limb movements is an important advancement regarding the control of powered prostheses. However, this technology is not yet in wide clinical use. Improvements in MPR could potentially increase the functionality of powered prostheses. To this purpose, offline accuracy and processing time were measured over 44 features using six classifiers with the aim of determining new configurations of features and classifiers to improve the accuracy and response time of prosthetics control. An efficient feature set (FS: waveform length, correlation coefficient, Hjorth Parameters) was found to improve the motion recognition accuracy. Using the proposed FS significantly increased the performance of linear discriminant analysis, K-nearest neighbor, maximum likelihood estimation (MLE), and support vector machine by 5.5%, 5.7%, 6.3%, and 6.2%, respectively, when compared with the Hudgins’ set. Using the FS with MLE provided the largest improvement in offline accuracy over the Hudgins feature set, with minimal effect on the processing time. Among the 44 features tested, logarithmic root mean square and normalized logarithmic energy yielded the highest recognition rates (above 95%). We anticipate that this work will contribute to the development of more accurate surface EMG-based motor decoding systems for the control prosthetic hands. [Figure not available: see fulltext.].
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| 7. |
- Gustavsson, Ulf, 1975
(författare)
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From Noise-Shaped Coding to Energy Efficiency - One bit at the time
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three parameters that drive the research and development of future RF transmitter technologies for high speed wireless communication today are energy efficiency, flexibility and reduction of the physical footprint. This thesis treats the use of single-bit quantization in conjunction with a method called Noise-Shaped Coding (NSC), as an enabler for these parameters, foremost in terms of energy efficiency.The first part of the thesis provides a short introduction to the common Radio Frequency Power Amplifier (RFPA) power efficiency enhancement techniques. The pulsed RF transmitter is introduced in which the RFPA is used as a switch, modulated by a single-bit quantized signal which allows it to operate solely at its two most efficient states.The second part of the thesis provides an introduction to the concept of NSC and the underlying idea of how high signal quality can be achieved with one bit quantization of the signal amplitude. A particular method of implementing NSC, namely the ΣΔ-modulator, is introduced and some common methods for design and analysis are discussed. An optimization-based approach to ΣΔ-modulator design is proposed and benchmarked against conventional methods in terms of its ability to shape the power spectral density of the quantization noise according to a given reconstruction filter response, minimizing the reconstructed error metric.The third and final part of the thesis focuses specifically on the application of ΣΔ-modulation in a pulsed RF transmitter context. The concepts of band-pass and baseband ΣΔ-modulation are introduced. A few important challenges related to the use of ΣΔ-modulation in a pulsed RF-transmitter context are identified. A ΣΔ-modulator topology which handles a complex input signal is investigated in great detail and advantages compared to conventional methods for using ΣΔ-modulation are unveiled by means of theoretical analysis and simulations. A method for suppressing the quantization noise within a frequency band surrounding the modulated RF carrier, enabling the use of more wideband reconstruction filter and moderate pulse-rates, is also presented. A detailed theoretical analysis reveals how optimized Noise-Shaped Coding, as provided by the optimization method introduced in the second part, can be deployed in order to improve the system performance. Finally, the method is validated by experimental measurements on two different high efficiency RFPAs at 1 and 3.5 GHz respectively, showing promising results.
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| 8. |
- Kersten, Anton, 1991, et al.
(författare)
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Battery Loss and Stress Mitigation in a Cascaded H-Bridge Multilevel Inverter for Vehicle Traction Applications by Filter Capacitors
- 2019
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Ingår i: IEEE Transactions on Transportation Electrification. - 2332-7782. ; 5:3, s. 659-671
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, two types of filter capacitors of varying capacity, were connected to the battery packs of a cascaded H-Bridge single-star multilevel vehicle traction inverter, and their influence on the battery losses has been analyzed. The battery and capacitor simulation models used are experimentally verified in a down-scaled system. Different capacitor configurations were simulated for four drive cycle scenarios to determine the potentials for the mitigation of current pulse stresses and battery loss reduction with respect to the added weight. By adding capacitors corresponding to a weight of 4% of the initial battery storage, the peak current is reduced by 5%-20%, depending on the operating point from DC to a few kHz, and the battery losses are reduced by 10%. In comparison, it is demonstrated that adding supercapacitors is more beneficial for lower output frequencies, while adding electrolytic capacitors is better for higher output frequencies. Furthermore, the low-order voltage harmonics of the DC-rails between the converter and battery were reduced by 10%-30% for frequencies above 9 kHz, which decreases the potential of electromagnetic disturbances. In addition, during cold battery temperatures, when it is very important to avoid heavy cyclings, the loss reduction using the capacitors was 2.5 times larger than for nominal temperature.
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| 9. |
- Kersten, Anton, 1991, et al.
(författare)
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Fault Detection and Localization for Limp Home Functionality of Three-Level NPC Inverters with Connected Neutral Point for Electric Vehicles
- 2019
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Ingår i: IEEE Transactions on Transportation Electrification. - 2332-7782. ; 5:2, s. 416-432
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the detection of single battery or inverter switch faults during operation of a common and an active three-level neutral-point-clamped (NPC) inverter with a connected neutral point. Here, the main focus lies on the detection and localization of open-circuit faults of the inverter's switches. Therefore, a fault detection algorithm, using a current estimator, and two fault localization algorithms, a pulse pattern injection principle and an online adaption of the space vector modulation (SVM), are investigated and verified through simulations and experiments. Also, investigated is how the powertrain can be operated under a fault condition, so that the vehicle can drive with a limited maximum power using an adapted SVM, referred to as "limp home" mode, to the next service station. It is shown, that an active NPC inverter can cope with any single short or open-circuit fault of the inverter's switches without bringing the vehicle to standstill, whereas a generic NPC inverter loses controllability if an open-circuit fault at an inner switch occurs. Furthermore, both inverter types are able to be operated just with half of the dc-link voltage in case of a failure in one part of the battery.
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| 10. |
- Kuder, Manuel, et al.
(författare)
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Exponential Modular Multilevel Converter for Low Voltage Applications
- 2019
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Ingår i: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe. ; , s. 1-11
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Konferensbidrag (refereegranskat)abstract
- This paper presents the structure and control of a single phase Exponential Modular Multilevel Converter (EMMC), which works as a bidirectional AC/DC converter. In addition to the main H-bridge converter, it uses series connected H-bridges with DC link capacitors. The nominal voltage rating of the capacitors is increased with each module by factor of two. In this manner, the number of output voltage levels exponentially increases with the number of series connected H-bridges. By using low-voltage MOSFETs it is possible to achieve a very high efficiency, especially at partial loading. The high number of voltage levels reduces the output voltage THD, while using a low switching frequency. Thus, the required grid filter size can be substantially reduced. Furthermore, the additional capacitor modules increase the nominal output voltage at the AC side, so that the flow of the active and reactive power can be dynamically adjusted. Therefore, the EMMC could be used, for instance, as a vehicle charger directly connected to the grid.
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