Economic Galileo E5 Receiver

The Galileo system introduces an extremely wideband civil E5 signal for high precision navigation. The structure of the receiver for the E5 signal is complicated due to the signal complexity and the large bandwidth. It is possible to process the whole E5 signal or process separately E5a and E5b parts combining obtained results afterwards (we call here such method as piece-wise processing). The second procedure has three times worse standard deviation of the pseudorange then first one. The main goal of the paper is to present a design of an E5 receiver which we will call the economic E5 receiver (ecoE5). It is built from jointly controlled correlators for the processing of the E5a and E5b signals which are parts of the E5 signal. Control of these partial E5a and E5b correlators is realized by only one delay and one phase lock loops. The performance, i.e. the pseudorange noise and multipath errors, of the receiver equipped with the ecoE5, is only slightly worse (the standard deviation of the pseudorange noise is 10 - 20% larger) than the performance of the optimal E5 receiver and it is much better than the performance of the receiver combining the piecewise (E5a and E5b) measurements. The ecoE5 receiver hardware demands are about one quarter of the hardware demands of the classical E5 receiver

Universality and Realistic Extensions to the Semi-Analytic Simulation Principle in GNSS Signal Processing

Semi-analytic simulation principle in GNSS signal processing bypasses the bit-true operations at high sampling frequency. Instead, signals at the output branches of the integrate&dump blocks are successfully modeled, thus making extensive Monte Carlo simulations feasible. Methods for simulations of code and carrier tracking loops with BPSK, BOC signals have been introduced in the literature. Matlab toolboxes were designed and published. In this paper, we further extend the applicability of the approach. Firstly, we describe any GNSS signal as a special instance of linear multi-dimensional modulation. Thereby, we state universal framework for classification of differently modulated signals. Using such description, we derive the semi-analytic models generally. Secondly, we extend the model for realistic scenarios including delay in the feed back, slowly fading multipath effects, finite bandwidth, phase noise, and a combination of these. Finally, a discussion on connection of this semi-analytic model and position-velocity-time estimator is delivered, as well as comparison of theoretical and simulated characteristics, produced by a prototype simulator developed at CTU in Prague

Electrodiffusion Method of Near-Wall Flow Diagnostics in Microfluidic Systems

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The electrodiffusion technique has been mostly used for the near-wall flow diagnostics on large scales. A novel technique for fabrication of plastic microfluidic systems with integrated metal microelectrodes (called technique of sacrificed substrate) enables us to produce microfluidic devices with precisely shaped sensors for wall shear stress measurements. Several micrometer thick gold sensors built-in a plastic substrate exhibit good mechanical resistance and smoothness. Proper functioning of prepared chips with microsensors has been first tested in various calibration experiments (polarization curve, sensor response to polarization set-up, steady flow calibration, temperature dependence of diffusivity). Our first results obtained for separating/reattaching flow behind a backward-facing step and for gas-liquid Taylor flow in microchannels then demonstrate its applicability for the detection of near-wall flow reversal, the delimitation of flow-recirculation zones, and the determination of wall shear stress response to moving bubbles. Other applications of these sensors in microfluidics (e.g. characterization of liquid films, capillary waves, bubbles or drops) can be also envisaged

Microalgal photosynthesis under flashing light

Microalgae are promising organisms for a biobased economy as a sustainable source of food, feed and fuel. High-density microalgae production could become cost effective in closed photobioreactors (PBR). Therefore, design and optimization of closed PBRs is a topic of ongoing research in both academic and industrial environment. Mixing in dense algae cultures causes light/dark (L/D) cycles of different magnitudes exposing algae to flashing light. It is often said that due to a flashing light effect, productivity of a PBR can be increased. In this thesis the flashing light effect is systematically investigated and the result is a mechanistic model that can predict microalgae growth under different flashing light regimes. The review of existing literature about L/D cycle experiments in Chapter 2 provides the theoretical background of the flashing light effect (L/D cycles) and discusses possibilities to improve PBR productivity by its application. It is concluded that PBR performance can be optimized by maximizing photosynthetic rate and biomass yield on light energy based on increased or controlled mixing and, thus, L/D cycling. It is unlikely to achieve maximal enhancement based on L/D cycles because of the fast mixing required: specific growth rate measurements in well-controlled, lab-scale PBRs suggest a minimal flash frequency of 14 Hz - 24 Hz combined with short flash times ( The application of flashing light alone in an artificially illuminated PBR has a limited effect on PBR performance, consequently, continuous (sun) light should be preferred. Further optimization strategies can be developed based on mechanistic models that describe the influence of L/D cycles on algae productivity as will be shown later in this thesis (Chapter 5). In Chapter 3, photosynthetic efficiency and growth of the green microalga Chlamydomonas reinhardtii were measured using LED light to simulate light/dark cycles ranging from 5 to 100 Hz at a light/dark ratio of 0.1 and a flash photon flux density (PFD) of 1000 µmol m-2 s-1. Light flashing at 100 Hz yielded the same photosynthetic efficiency and specific growth rate as cultivation under continuous illumination with the same time-averaged PFD, which is called full light integration. The efficiency and growth rate decreased with decreasing flash frequency. At all frequencies, the rate of linear electron transport during the flash was higher than during maximal growth under continuous light, suggesting storage of reducing equivalents during the flash, which are available during the dark period. In this way the dark reaction of photosynthesis can continue during the dark time of an L/D cycle. This is a possible explanation for the mechanism behind the flashing light effect. Another parameter that describes an L/D cycle besides frequency, is the duty cycle, it determines the time fraction algae spend in the light. In Chapter 4 the influence of different duty cycles on oxygen yield on absorbed light energy and photosynthetic oxygen evolution was investigated. Net oxygen evolution of Chlamydomonas reinhardtii was measured for four duty cycles (0.05, 0.1, 0.2 and 0.5) in a biological oxygen monitor. Over-saturating light flashes were applied in a square-wave fashion with four flash frequencies (5, 10, 50, 100 Hz). Algae were pre-cultivated in a turbidostat and acclimated to a low photon flux density (PFD). A photosynthesis-irradiance curve was measured under continuous illumination and used to calculate the net oxygen yield, which was maximal between a PFD of 100 and 200 µmol m-2 s-1. Net oxygen yield under flashing light was proven to be duty cycle dependent: the highest yield was observed at a duty cycle of 0.1 (i.e. a time-averaged PFD of 115 µmol m-2 s-1). At lower duty cycles maintenance respiration reduced net oxygen yield. At higher duty cycles photon absorption rate exceeded the maximal photon utilization rate and, as a result, surplus light energy was dissipated as heat, which lead to a reduction in net oxygen yield. This behavior was identical with the observation under continuous light. Understanding photosynthetic growth in dynamic light regimes is crucial to develop models that can predict PBR productivities under continuous and flashing light. Therefore, the objective of Chapter 5 was to develop and validate a mechanistic model that describes photosynthetic net oxygen evolution under flashing light based on biomass specific light absorption rate and light dissipation rate of excess absorbed light. The model describes photosynthetic oxygen evolution based on the availability of reducing equivalents (electrons), which result from the light reactions. Electrons are accumulated during the flash and serve as a pool for carbon dioxide fixation during the dark, which leads to partial or full light integration. Both, electron consumption rate and energy dissipation rate are based on a Monod-type kinetic. The underlying assumption of an electron pool seems correct and its filling and emptying is depending on the flash time. In general, with increase in flash time the energy dissipation rate increased as well. And, simulations showed that if the dark time between flashes is not sufficiently long then the pool will not be completely empty and is responsible for a high energy dissipation rate. The measured oxygen production rates were described well, but the description of the energy dissipation rate will need further investigation. Not only L/D cycles but also fluctuating light that algae experience while moving through the light gradient will influence PBR productivity. In Chapter 6 the combined effect of L/D cycles and fluctuating light on biomass yield on light energy was studied. For this purpose we used controlled, short light path, laboratory, turbidostat-operated PBRs equipped with a LED light source for square-wave L/D cycles with frequencies from 1 Hz to 100 Hz. Biomass density was adjusted that the PFD leaving the PBR was equal to the compensation point of photosynthesis (10 µmol m-2 s-1). Algae were acclimated to a sub-saturating incident PFD of 220 μmol m-2 s-1 for continuous light. Using a duty cycle of 0.5, we observed that L/D cycles of 1 Hz and 10 Hz resulted on average in a 10 % lower biomass yield, but L/D cycles of 100 Hz resulted on average in a 35 % higher biomass yield than the yield obtained in continuous light. The results show that the interaction of L/D cycle frequency, culture density and incident PFD lead to certain PBR productivity. Hence, appropriate L/D cycle frequency setting by mixing and dark zone setting by biomass concentration can optimize PBR productivity. And, reduce the effect that a dark zone exposure impinges on biomass yield in microalgae cultivation. The last chapter is a general discussion (Chapter 7) that places the results of the thesis into context for PBR operation. It is discussed that L/D cycle frequencies of 1-10 Hz, which can be achieved in practice, have a minor impact on biomass yield and volumetric productivity. But, the PBR can be operated with a dark zone and a major gain in biomass concentration can be achieved. However, the size of the dark zone is limited by the incident PFD. The incident PFD times the relative size of the photic zone should be in the same range where the optimal yield under continuous light can be found based on a P-I curve measurement. The photic zone is then defined as the volume with a PFD above the compensation point divided by the total volume. With simulations based on the dynamic model we could show that light integration can be explained by an electron storage pool that fills during the flash and is used during the dark. Furthermore, the dynamic model could be used to predict PBR productivities based on real fluctuating light regimes observed in photobioreactors. </p

Precise Characterization and Multiobjective Optimization of Low Noise Amplifiers

Although practically all function blocks of the satellite navigation receivers are realized using the CMOS digital integrated circuits, it is appropriate to create a separate low noise antenna preamplifier based on a low noise pHEMT. Such an RF front end can be strongly optimized to attain a suitable tradeoff between the noise figure and transducer power gain. Further, as all the four principal navigation systems (GPS, GLONASS, Galileo, and COMPASS) work in similar frequency bands (roughly from 1.1 to 1.7 GHz), it is reasonable to create the low noise preamplifier for all of them. In the paper, a sophisticated method of the amplifier design is suggested based on multiobjective optimization. A substantial improvement of a standard optimization method is also outlined to satisfy a uniform coverage of Pareto front. Moreover, for enhancing efficiency of many times repeated solutions of large linear systems during the optimization, a new modification of the Markowitz criterion is suggested compatible with fast modes of the LU factorization. Extraordinary attention was also given to the accuracy of modeling. First, an extraction of pHEMT model parameters was performed including its noise part, and several models were compared. The extraction was carried out by an original identification procedure based on a combination of metaheuristic and direct methods. Second, the equations of the passive elements (including transmission lines and T-splitters) were carefully defined using frequency dispersion of their parameters as Q, ESR, etc. Third, an optimal selection of the operating point and essential passive elements was performed using the improved optimization method. Finally, the s-parameters and noise figure of the amplifier were measured, and stability and third-order intermodulation products were also checked

The DVB-T-Based Positioning System and Single Frequency Network Offset Estimation

As position information becomes more and more important in many fields of technology it is advantageous to recognize it in scenarios where satellite-based systems fail. Such a case is the scenario inside buildings where attenuation of a signal is too high making it impossible to receive despite the availability of terrestrial services. A positioning system based on terrestrial broadcasting is presented in this paper. The aim is to create an automatic receiver enabling a multi--sensor positioning system to be built and resulting in increased availability and reliability of position information. This paper introduces a method that demonstrates how to design a signal detector capable of operating in a multipath scenario. Finally, the most restrictive problem of the positioning system is the unknown time offset setting of individual emitters that render this system useless. A solution to this problem is proposed and tested in a real scenario. The innovative methods and algorithms presented in this paper show, for the first time, how to automatically evaluate position using digital video broadcasting. The result of an experiment with a real digital video broadcasting network is presented

Adjusted Light and Dark Cycles Can Optimize Photosynthetic Efficiency in Algae Growing in Photobioreactors

Biofuels from algae are highly interesting as renewable energy sources to replace, at least partially, fossil fuels, but great research efforts are still needed to optimize growth parameters to develop competitive large-scale cultivation systems. One factor with a seminal influence on productivity is light availability. Light energy fully supports algal growth, but it leads to oxidative stress if illumination is in excess. In this work, the influence of light intensity on the growth and lipid productivity of Nannochloropsis salina was investigated in a flat-bed photobioreactor designed to minimize cells self-shading. The influence of various light intensities was studied with both continuous illumination and alternation of light and dark cycles at various frequencies, which mimic illumination variations in a photobioreactor due to mixing. Results show that Nannochloropsis can efficiently exploit even very intense light, provided that dark cycles occur to allow for re-oxidation of the electron transporters of the photosynthetic apparatus. If alternation of light and dark is not optimal, algae undergo radiation damage and photosynthetic productivity is greatly reduced. Our results demonstrate that, in a photobioreactor for the cultivation of algae, optimizing mixing is essential in order to ensure that the algae exploit light energy efficiently