Analysis, design and implementation of front-end reconfigurable antenna systems (FERAS)

The increase in demand on reconfigurable systems and especially for wireless communications applications has stressed the need for smart and agile RF devices that sense and respond to the RF changes in the environment. Many different applications require frequency agility with software control ability such as in a cognitive radio environment where antenna systems have to be designed to fulfill the extendable and reconfigurable multi-service and multi-band requirements. Such applications increase spectrum efficiency as well as the power utilization in modern wireless systems. The emphasis of this dissertation revolves around the following question: Is it possible to come up with new techniques to achieve reconfigurable antenna systems with better performance?\u27 Two main branches constitute the outline of this work. The first one is based on the design of reconfigurable antennas by incorporating photoconductive switching elements in order to change the antenna electrical properties. The second branch relies on the change in the physical structure of the antenna via a rotational motion. In this work a new photoconductive switch is designed with a new light delivery technique. This switch is incorporated into new optically pumped reconfigurable antenna systems (OPRAS). The implementation of these antenna systems in applications such as cognitive radio is demonstrated and discussed. A new radio frequency (RF) technique for measuring the semiconductor carrier lifetime using optically reconfigurable transmission lines is proposed. A switching time investigation for the OPRAS is also accomplished to better cater for the cognitive radio requirements. Moreover, different reconfiguration mechanisms are addressed such as physical alteration of antenna parts via a rotational motion. This technique is supported by software to achieve a complete controlled rotatable reconfigurable cognitive radio antenna system. The inter-correlation between neural networks and cellular automata is also addressed for the design of reconfigurable and multi-band antenna systems for various applications.\u2

Analysis of Galileo E5 and E5ab code tracking

The world of global navigation satellite systems has been enhanced with several new or improved signals in space aiming to optimize accuracy, reliability, navigation solution, and interoperability between different constellations. However, such developments bring various challenges to the receivers' designers. For example, acquisition and tracking stages turn into more complex processes while handling the increasing bandwidth requires additional processing power. In this context, we study the code tracking of Galileo E5ab in a full band or of only one of its components, i.e., either E5a or E5b. More specifically, an architecture for tracking the E5 pilot channel as an AltBOC(15,10) or BPSK(10) modulation is introduced, and the performance of well-known discriminator types is analyzed using analytical derivations and simulations of linearity and stability regions, thermal noise tracking errors, multipath error envelopes and tracking thresholds. Different parameters, such as the front-end filter bandwidth, the early/late chip spacing, un-normalized and normalized discriminators, are taken into consideration. The results obtained are used to illustrate the main advantages and drawbacks of tracking the E5 signal as well as to help defining the main tracking loop parameters for an enhanced performanc

Analysis of Galileo E5 and E5ab code tracking

The world of global navigation satellite systems has been enhanced with several new or improved signals in space aiming to optimize accuracy, reliability, navigation solution, and interoperability between different constellations. However, such developments bring various challenges to the receivers’ designers. For example, acquisition and tracking stages turn into more complex processes while handling the increasing bandwidth requires additional processing power. In this context, we study the code tracking of Galileo E5ab in a full band or of only one of its components, i.e., either E5a or E5b. More specifically, an architecture for tracking the E5 pilot channel as an AltBOC(15,10) or BPSK(10) modulation is introduced, and the performance of well-known discriminator types is analyzed using analytical derivations and simulations of linearity and stability regions, thermal noise tracking errors, multipath error envelopes and tracking thresholds. Different parameters, such as the front-end filter bandwidth, the early/late chip spacing, un-normalized and normalized discriminators, are taken into consideration. The results obtained are used to illustrate the main advantages and drawbacks of tracking the E5 signal as well as to help defining the main tracking loop parameters for an enhanced performance

Acquisition Performance of Galileo E5a Signal

The introduction of new modulations on the global navigation satellite systems brings potential improvements for ground positioning. Clever receiver designs taking advantage of the characteristics of the new signals will be able to achieve better accuracy, higher sensitivity, improved multipath mitigation and tracking robustness. In this context, this paper focuses on the Galileo E5a signal and study different acquisition architectures that can be applied on this signal. Their performances are discussed in terms of detection sensitivity and by a theoretical characterization of the false alarm and detection probabilities. The theoretical results are validated by measurements using a Spirent constellation simulator, a Fraunhofer triple band frontend and a non real time software receiver

Implementation and Performance of a GPS/INS Tightly Coupled Assisted PLL Architecture Using MEMS Inertial Sensors

The use of global navigation satellite system receivers for navigation still presents many challenges in urban canyon and indoor environments, where satellite availability is typically reduced and received signals are attenuated. To improve the navigation performance in such environments, several enhancement methods can be implemented. For instance, external aid provided through coupling with other sensors has proven to contribute substantially to enhancing navigation performance and robustness. Within this context, coupling a very simple GPS receiver with an Inertial Navigation System (INS) based on low-cost micro-electro-mechanical systems (MEMS) inertial sensors is considered in this paper. In particular, we propose a GPS/INS Tightly Coupled Assisted PLL (TCAPLL) architecture, and present most of the associated challenges that need to be addressed when dealing with very-low-performance MEMS inertial sensors. In addition, we propose a data monitoring system in charge of checking the quality of the measurement flow in the architecture. The implementation of the TCAPLL is discussed in detail, and its performance under different scenarios is assessed. Finally, the architecture is evaluated through a test campaign using a vehicle that is driven in urban environments, with the purpose of highlighting the pros and cons of combining MEMS inertial sensors with GPS over GPS alone

Universal-SBAS: A worldwide multimodal standard

This paper describes a generalisation of the aeronautical GNSS Space Based Augmentation System (SBAS) air interface, in a true worldwide multimodal standard named Universal S-BAS. Examples of usages of this multifrequency future standard are presented in the area of science and precise positioning, timing, security, robust positioning, maritime and reflectometry applications

Advanced Algorithmic and Architecture Designs for Future Satellite Navigation Receivers

The use of global navigation satellite system (GNSS) receivers for navigation still presents many challenges, in particular in urban canyon and indoor environments where satellite availability is reduced and received signals are usually much atten- uated. In addition, the reception of additional signal replicas due to reflections on the surrounding environment, i.e. multipath, introduces biases in the pseudorange measurements, which in turn lead to extra positioning errors. The navigation per- formance of a GNSS receiver depends greatly on the behavior of the phase lock loop (PLL) and the delay lock loop (DLL). To maintain the robustness of these loops in such conditions, several enhancement methods can be implemented to improve upon standard stand-alone mass market receivers. For instance, well-known techniques include the use of multi-constellations to improve the availability of visible satellites, take advantage of the potential multipath mitigation of the new GNSS signals, and an increase of the integration time combined with a decrease of the PLL and DLL filters bandwidths to improve sensitivity. Moreover, external aiding in the form of time, Doppler, position, or almanac that can be provided through coupling with other sensors can also contribute substantially in improving navigation performance in challenging environments. The aim of this dissertation is to address the challenges of satellite based naviga- tion in demanding environments in order to improve the navigation performance of the future GNSS receivers. Within this context, two research directions are adopted in this thesis. The first is to explore the performance and advantages of the upcoming Galileo signals and in particular the E5 Alternate Binary Offset Carrier AltBOC(15,10), and the second is to investigate the potential of low-cost micro-electro-mechanical systems (MEMS) based inertial sensors to complement GNSS receivers. In the first research direction, we present investigations of the processing of Galileo E5ab in a full band or of only one of its components, i.e. either E5a or E5b. More specifically, a new acquisition algorithm is proposed for wiping off the secondary code and thereby increase the coherent integration time while requiring a reasonable implementation complexity as compared to other architectures. Moreover, an archi- tecture for tracking the E5 pilot channel as an AltBOC(15,10) or BPSK(10) modulation is introduced, and the performance of well-known discriminator types is analyzed using analytical derivations and simulations of linearity and stability regions, thermal noise tracking errors, multipath error envelopes and tracking thresholds. Different parameters, such as the front-end filter bandwidth, the early/late chip spacing, un- normalized and normalized discriminators, are taken into consideration. The results we obtain are used to illustrate the main advantages and drawbacks of using the E5 signal in demanding environments as well as to help defining the main tracking loop parameters for an enhanced performance. In the second research direction, we consider the coupling of a global positioning system (GPS) receiver with an inertial navigation system (INS) based on MEMS sen- sors. In the past, one of the main constraints holding back the proliferation of such hybrid systems was the price of the inertial sensors, but with the widespread dissemi- nation of MEMS-based sensors this is no longer the case. Therefore, a GPS/INS Tightly Coupled Assisted PLL (TCAPLL) architecture is proposed in this dissertation, and most of the associated challenges that need to be addressed when dealing with very- low-performance MEMS inertial sensors are presented. The architecture includes a data monitoring system responsible for checking the quality of the measurement flow to maintain robust tracking and accurate navigation. The implementation of the TCAPLL is discussed in detail, and its performance under different scenarios is assessed. Finally the proposed architecture is evaluated through a test campaign using a vehicle that is driven in urban environments, with the purpose of highlighting the pros and cons of combining MEMS inertial sensors with GPS over GPS alone

Current Distribution in High RF Power Transistors

To obtain the power levels required from high RF power transistors, the size of the chip has often to be made so large that inductance of electrical connections inside the package cannot be neglected. This may have the effect that various parts of the transistor chip are not connected exactly parallel, i.e. drain and gate voltages and currents densities will not be the same on different parts of the chip. This may result in degraded output power and efficiency. The same effect may occur when more than one chip are connected in parallel in a transistor package to obtain even higher output power.Often the connections to the transistor package are approximated as a number of electrical point connections (normally three: gate, drain, source); meaning that each of them can be described by a single electrical potential and current. In reality, they may be large enough that voltage and current distributions have to be considered. These distributions will be affected by different mountings of the transistor and other connected components.In this work, the LDMOS power transistor MRF6S21140HR3 was modeled using the segmentation method in high frequency signal simulation HFSS which is a 3D Full-Wave Electromagnetic Field Simulation, and utilized the advanced design system ADS to find a parameterized lumped model. Both the electromagnetic and lumped models showed consistent results. Non-ideal parallel connection of sub-transistors on chip is very important, but further studies are needed for definite conclusion. It was verified through modeling that non ideal parallel connection of different chips in the package does have an effect; the effect however is quiet small which proves that the signal is slightly non-uniformly distributed between the three chips in the package. External connection to PCB (drain connection is considered in this work) can effectively be taken as a point connection to some approximation. The electrical behavior of the modeled transistor was studied through the design of a class B power amplifier in order to estimate the importance of performance degradation due to non-ideal parallel connections and how these non ideal connections degrade efficiency and output power. The modeled transistor can deliver a maximum output power of 147 watts and efficiency of 65%. We have also studied the current distribution between the three chips in a three stage class B power amplifier. Again, the difference in the current distribution between the three chips turned out to be quiet small. All these results are presented through this work. The final conclusion regarding the current distribution between multichips cannot be made just based on these simulation results. The next step should be aimed at considering other effects, the thermal effect for example, in order to know exactly whether it is uniformly or not uniformly distributed