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  • Khanzadi, M Reza, 1983-, et al. (författare)
  • Calculation of the Performance of Communication Systems from Measured Oscillator Phase Noise
  • 2014
  • Ingår i: IEEE Transactions on Circuits and Systems I: Regular Papers. - 1549-8328. ; 61:5, s. 1553-1565
  • 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.
  • Khanzadi, M Reza, 1983- (författare)
  • Modeling and Estimation of Phase Noise in Oscillators with Colored Noise Sources
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt)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.
  • Nopchinda, Dhecha, 1991- (författare)
  • mm-Wave Data Transmission and Measurement Techniques: A Holistic Approach
  • 2019
  • Ingår i: Lösningar för trådlös kommunikation med hög datatakt. - Gothenburg : Chalmers tekniska högskola. - 978-91-7905-201-0
  • Doktorsavhandling (övrigt vetenskapligt)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.
  • Jang, Jeong Keun, et al. (författare)
  • Area-efficient scheduling scheme based FFT processor for various OFDM systems
  • 2018
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • <p>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.</p>
  • Gustavsson, Ulf, 1975- (författare)
  • From Noise-Shaped Coding to Energy Efficiency - One bit at the time
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt)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.
  • Seyedhosseinzadeh, Neda, et al. (författare)
  • A 100–140 GHz SiGe-BiCMOS sub-harmonic down-converter mixer
  • 2017
  • Ingår i: 2017 12th European Microwave Integrated Circuits Conference (EuMIC). - 978-2-87487-048-4
  • Konferensbidrag (refereegranskat)abstract
    • This paper demonstrates a wideband, subharmonic down converting mixer using a commercial 130-nm SiGe-BiCMOS technology. The mixer adopts a frequency doubling LO-stage, a differential switched-transconductance RF-stage, on-chip LO and RF baluns, and two emitter-follower buffer-stages. The measured results exhibit a maximum conversion gain up to 2.6 dB over the frequency range of 100 to 140 GHz with a LO power of 5 dBm. The mixer achieves an input referred 1-dB compression point of −7.2 dBm, with a DC power of 46.3 mW, including 26.7 mW for buffer-stages. It demonstrates also up to 12 GHz 3-dB IF bandwidth, which to the authors' best knowledge, is the highest obtained among active sub-harmonic mixers operating above 100 GHz. The chip occupies 0.4 mm2, including pads.
  • Sezgin, Ibrahim Can, 1992-, et al. (författare)
  • A Low-Complexity Distributed-MIMO Testbed Based on High-Speed Sigma-Delta-Over-Fiber
  • 2019
  • Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 67:7, s. 2861-2872
  • Tidskriftsartikel (refereegranskat)abstract
    • Distributed multiple-input-multiple-output (D-MIMO) is a very promising technique to improve capacity and quality of service for emerging 5G systems. In this paper, we propose a flexible and low-cost testbed for D-MIMO systems, where a sigma-delta over fiber (SDoF) solution is proposed to address the fundamental challenge of phase-coherent transmission between multiple distributed access points (APs) from a central unit (CU). Employing low-cost standardized optical data interconnects, SDoF, brings a very flexible and software controlled transmission of RF signals over optical fiber. An SDoF-based D-MIMO testbed with a CU feeding 12 distributed APs has been realized and experimentally evaluated. Initial experiments of D-MIMO and conventional colocated MIMO systems at 2.365 GHz have been performed to demonstrate the flexibility and potential of the proposed testbed as a new powerful tool in the design and analysis of emerging communication system concepts.
  • Bengtsson, Lars, 1963- (författare)
  • Mikrodatorteknik
  • 1995
  • Bok (övrigt vetenskapligt)abstract
    • Första delen behandlar Microchips "Base-line"-kretsar och andra delen behandlar "Midrange"-kretsarna. De flesta funktioner belyses med konstruktionsexempel. Exempel och övningar är mycket hårdvarunära och boken behandlar konstruktion av mikrodatorer från grunden. Boken är avsedd för kurser i mikrodatorteknik på högskolan eller annan högre teknisk utbildning, men kan även användas som självstudiematerial eftersom de flesta exempel ges med detaljerade och verifierade lösningar av såväl hård- som mjukvaran. Tidigare erfarenhet av assemblerprogrammering är inte nödvändig men grundläggande kunskaper i digitalteknik förutsätts. Boken kan med fördel också läsas av rutinerade assemblerprogrammerare som vill veta hur prestanda hos de nya RISC-baserade PIC-controllerna står sig i konkurrensen med de mer etablerade enchipscontrollerna, t ex HC11 och 8751, som bygger på traditionell CISC-arkitektur.
  • Bencivenni, Carlo, 1986- (författare)
  • Aperiodic Array Synthesis for Telecommunications
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Arrays of antennas offer important advantages over single-element antennas and are thus a key part of most advanced communication systems. The majority of current arrays are based on a classical regular layout, which offer simple design criteria despite some limitations. Aperiodic arrays can reduce the number of elements and improve the performance, however their design is far more challenging. This thesis focuses on the synthesis of aperiodic arrays, advancing the state-of-the-art of phased arrays and pioneering the application to Multiple-Input Multiple-Output (MIMO) systems.In satellite communications (SATCOM), aperiodic sparse arrays have the potential for drastically reducing the costs of massive antennas. Most available synthesis methods are however either intractable, suboptimal or limited for such demanding scenarios. We propose a deterministic and efficient approach based on Compressive Sensing, capable of accounting for electromagnetic phenomena and complex specifications. Some of the key contributions include the extension to the design of multi-beam, modular, multi-element, reconfigurable and isophoric architectures.The same approach is successfully applied to the design of compact arrays for Point-to-Point (PtP) backhauling. The aperiodicity is used here instead to reduce the side lobes and meet the target radiation envelope with high aperture efficiency. A dense, column arranged, slotted waveguide isophoric array has been successfully designed, manufactured and measured.Line-of-Sight (LoS) MIMO can multiply the data rates of classical Single-Input Single-Output (SISO) backhauling systems, however it suffers from limited installation flexibility. We demonstrate how aperiodic arrays and their switched extensions can instead overcome this shortcoming. Since a small number of antennas are typically used, an exhaustive search is adopted for the synthesis.Massive Multi-User (MU) MIMO is envisioned as a key technology for future 5G systems. Despite the prevailing understanding, we show how the MIMO performance is affected by the array layout. To exploit this, we propose a new hybrid statistical-density tapered synthesis approach. Results show a significant improvement in minimum power budget, capacity and amplifier efficiency, especially for massive and/or crowded systems
  • Chani Cahuana, Jessica, 1988-, et al. (författare)
  • Digital Predistortion Parameter Identification for RF Power Amplifiers Using Real-Valued Output Data
  • 2017
  • Ingår i: IEEE Transactions on Circuits and Systems II: Express Briefs. - 1549-7747 .- 1558-3791. ; 64:10, s. 1227-1231
  • Tidskriftsartikel (refereegranskat)abstract
    • This brief presents a novel digital predistortion (DPD) parameter identification technique that requires only the acquisition of either the in-phase (I) or the quadrature (Q) component of the power amplifier (PA) output signal. To this end, an approach that allows us to estimate the parameters of a model using only one of the IQ components of the model output is presented. Based on experimental results, it is shown that the proposed real-valued measurements based technique can offer similar linearization capabilities as its complex-valued counterparts. The experimental results also indicate that the proposed technique can be used in combination with other techniques that focus on reducing the speed of analog-to-digital converters (ADCs)
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