International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes a kind of Microwave Digital Frequency Synthesizer used for S-band telemetry receivers. As well known many modern electronic systems employ a Frequency Synthesizer whose spectral purity is critical. The characteristics of a PLL (Phase-Locked Loop) Frequency Synthesizer, such as frequency resolution, phase noise, spurious suppression and switch time, should be compromised in our design. A heterodyne Frequency Synthesis is often considered as a good approach to solve the problem. But it is complicated in structure and circuit. A variable-reference-driven PLL Frequency Synthesizer was introduced which can give an improved trade-off among frequency resolution, phase noise, spurious suppression. In this paper the phase noise and spurious suppression characteristic of variable-reference-driven PLL Frequency Synthesizer is analyzed theoretically and compared with that of the heterodyne Frequency Synthesizer. For engineering application, a practical Microwave Digital Frequency Synthesizer used for telemetry receiver has been designed, which is characterized by simply structure, low phase noise and low spurious output. The output spectrum of experimental measurements is given.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Space agencies are under pressure to utilize better bandwidth-efficient communication methods due to the actual allocated frequency bands becoming more congested. Budget reductions is another problem that the space agencies must deal with. This budget constraint results in simpler spacecraft carrying less communication capabilities and also the reduction in staff to capture data in the earth stations. It is then imperative that the most bandwidth efficient communication methods be utilized. This paper gives the results of a computer simulation study on 8 Level Phase Shift Keying (8PSK) modulation with respect to bandwidth, power efficiency, spurious emissions, interference susceptibility and the non-constant envelope effect through a non-linear channel. The simulations were performed on a Signal Processing Worksystem (SPW: software installed on a SUN SPARC 10 Unix Station and Hewlett Packard Model 715/100 Unix Station). This work was conducted at New Mexico State University (NMSU) in the Center for Space Telemetry and Telecommunications Systems in the Klipsch School of Electrical and Computer Engineering.

Master of Science / Department of Electrical Engineering / William Kuhn / Q-enhanced Filters have been researched extensively, but have not been often implemented into receiver architectures due to inherent challenges in the design and stability of these filters. However, recent works have successfully addressed Q-enhanced filter designs which are viable for receiver implementation with tuning algorithms to achieve temperature stability. This work continues these efforts with the redesign of a Two-Pole Q-Enhanced Band-Pass filter tested at narrower fractional bandwidths than previous work of less than one percent and considers potential significant improvements in receiver performance using this filer. The Q-enhanced filter redesign ports the existing filter to a new integrated circuit technology which performs better at higher frequencies. The redesign in particular addresses problems in the previous design. The frequency divider design is modified, resistance tuning is added, and additional modifications to the overall filter functionality are implemented. General problems in obtaining an ideal passband shape by eliminating unwanted coupling are addressed. The supporting software for the tuning algorithm is modified to use analog controls and shown to achieve further narrowed bandwidths of 5 MHz and 2.5 MHz at center frequencies of 500 MHz, which are demonstrated to be temperature stable. Future software modifications are described to prepare the existing code base for the new filter design. Potential applications for a Q-enhanced filter include improving the performance of receiver designs. One of the most important performance parameters of a receiver is its spurious response rejection. To explore this behavior, an automated test system is developed to characterize receivers, and four receivers are tested. The test results are presented in a novel graphical display, which is used to evaluate receiver performance and compare receivers. These results motivated the development of a potential modified superheterodyne receiver architecture using the Q-enhanced filter as an image filter and an IF filter. The viability of this receiver design is tested and shown to provide significant improvements to receiver’s spurious rejection response.

This thesis presents the theory and design of fixed and Radio Frequency (RF) Microelectromechanical Systems (MEMS) -based tunable microwave filters for RF and microwave applications. The methodology for the design of coupled resonator filters is explained in detail and is used to design an end-coupled microstrip filter at 1.5 GHz with inductive loading using a stepped microstrip discontinuity to lower the resonance frequency of the half-wavelength microstrip resonator. The fabricated endcoupled filter shows center frequencies of 1.36 GHz and 1.03 GHz in the unloaded and loaded state respectively, with insertion losses between 1.2-1.5 dB and return loss better than 10 dB in both states. The filter response shows spurious passbands at approximately twice the filter center frequencies. To overcome this problem and improve the upper rejection skirt of the filter, microstrip resonators with tapped input/output coupling and mixed inter-resonator coupling are used to suppress the spurious passband by introducing a transmission zero at spurious resonance frequency. Measurement results for the fabricated tapped-resonator filters show an improvement of the upper rejection skirt due to spurious suppression to a level of -40 dB, with insertion loss of 1.2-1.5 dB for the same center frequencies. The concepts developed from fabrication and measurement of fixed-tuned microstrip filters are used to design an inductively-loaded RF MEMS tunable filter with adjustable spurious suppression implemented using packaged metal-contact switches. The two-pole 5% filter has a tuning range of 17% from 1.06 GHz to 1.23 GHz with an insertion loss of 1.56-2.28 dB and return loss better than 13 dB over the tuning range. The inductive loading mechanism is used to tune the open-ended quarter wavelength stub such that a tunable transmission zero supresses the spurious resonance as the filter center frequency is tuned. The spurious passband response in both states is suppressed below -20 dB. The unloaded quality factor (Q) of the filter varies from 127 to 75 as the filter is tuned. The equivalent circuit model for the series metalcontact packaged RF MEMS switch used in the tunable filter is derived from full-wave electromagnetic simulations and used to predict the effect of MEMS switch parasitics on the overall performance of the tunable filter.

[pt] Três métodos de eliminação de modos espúrios em soluções de guias de ondas dielétricos, inomogêneos e anisotrópicos, usando formulações variacionais e o Método de Elementos Finitos são analisados. O método das penalidades com a técnica de integração reduzida seletiva é aplicado pela primeira em problemas de Eletromagnetismo. Através da análise de vários exemplos, seus resultados são comparados aos obtidos com o método das componentes transversais devido a Hayata e Koshiba e com o uso de elementos de aresta. A qualidade das aproximações e o desempenho computacional comprovam a eficiência da integração reduzida, que eliminou os principais incovenientes do método das penalidades, mantendo seus atrativos e a simplicidade da implementação. O uso de elementos de aresta também se mostrou uma abordagem atraente embora seus mecanismos de funcionamento ainda não estejam completamente entendidos e apesar da maior complexidade na implementação. / [en] Three methods for elimination of spurious modes from variationally formulated Finite Element solutions of inhomogeneous/anisotropic dieletric waveguides are compared. The Reduced Integration Penalty Method is applied for the first time. To EM wave problems. From the analyses of various examples, the results of this method are compared to those obtained with the Hayeta and Koshiba transversal component method and with the use of edge elements. The quality of the approximations and the computacional performance testify the efficacy of the reduced integration that eliminates the main drawbacks fo the Penalty method while preserving its advantages and simplicity of implementation. The use of edge elements was proven to be a very attractive approach, although its mechanisms are still to be fully understood and its implementation may not always be straightforward in a standard Finite

The convenience of IEEE 802.11-based wireless access networks has led to widespread deployment. However, these applications are predicated on the assumption of availability and confidentiality. Error-prone wireless networks afford an attacker considerable flexibility to exploit the vulnerabilities of 802.11-based mechanism. Two of most famous misbehaviors are selfish and malicious attacks. In this thesis we investigate two attacks: Spurious CTS attack (SCTS) and Jamming ACK attack (JACK). In the SCTS, malicious nodes may send periodic Spurious CTS packets to force other nodes to update their NAV values and prevent them from using the channel. In the JACK, an attacker ruins legitimate ACK packets for the intention of disrupting the traffic flow and draining the battery energy of victim nodes quickly. Correspondingly, we propose solutions: termed Carrier Sensing based Discarding (CSD), and Extended Network Allocation Vector (ENAV) scheme. We further demonstrate the performance of our proposed schemes through analysis and NS2 simulations.

<p>The goal of this final year project is to investigate various techniques to up-convert a baseband signal into radio frequency signals, and to investigate the practical problems encountered in an offset phase locked loop design by implementation. </p><p>Phase locked loops are commonly used in radio transmitters and receivers to generate accurate RF signals from a low-frequency reference. This thesis will highlight some of the problems and strengths of various up-conversion schemes, and suggest an offset-PLL architecture free from many of those problems. </p><p>An offset-PLL is often used in mobile communication systems where the required levels of out of band transmission are tough and the use of superheterodyne up-conversion cannot be used due to spectrum or bandwidth requirements. </p><p>However a drawback of an offset-PLL is the high locking time; this can render the offset-PLL useless in TDMA communication systems. This problem among others has been studied theoretically as well as practically on an actual implementation of an offset-PLL for mobile communications. The offset-PLL was designed and manufactured as part of this project.</p>

In the recent years, Independent Component Analysis (ICA) has become a fundamental tool in adaptive signal and data processing, especially in the field of Blind Source Separation (BSS). Even though there exist some methods for which an algebraic solution to the ICA problem may be found, other iterative methods are very popular. Among them is the class of information-theoretic approaches, laying on entropies. The associated objective functions are maximized based on optimization schemes, and on gradient-ascent techniques in particular. Two major issues in this field are the following: 1) Does the global maximum point of these entropic objectives correspond to a satisfactory solution of BSS ? and 2) as gradient techniques are used, optimization algorithms look in fact for local maximum points, so what about the meaning of these local optima from the BSS problem point of view? Even though there are some partial answers to these questions in the literature, most of them are based on simulation and conjectures; formal developments are often lacking. This thesis aims at filling this lack and providing intuitive justifications, too. We focus the analysis on Rényi's entropy-based contrast functions. Our results show that, generally speaking, Rényi's entropy is not a suitable contrast function for BSS, even though we recover the well-known results saying that Shannon's entropy-based objectives are contrast functions. We also show that the range-based contrast functions can be built under some conditions on the sources. The BSS problem is stated in the first chapter, and viewed under the information (theory) angle. The two next chapters address specifically the above questions. Finally, the last chapter deals with range-based ICA, the only ``entropy-based contrast' which, based on the enclosed results, is also a <i>discriminant</i> contrast function, in the sense that it is theoretically free of spurious local optima. Geometrical interpretations and surprising examples are given. The interest of this approach is confirmed by testing the algorithm on the MLSP 2006 data analysis competition benchmark; the proposed method outperforms the previously obtained results on large-scale and noisy mixture samples obtained through ill-conditioned mixing matrices.

The aim of this research is to check whether the Taylor rule in its simple linear form can be viewed as an appropriate description of the monetary policy pursued by Norway’s central bank – Norges Bank, and whether this rule can be used for forecasting purposes. Not only does this research focus on the original Taylor rule, but it also deals with its extended version designed for small open economies such as Norway. A conclusion about whether regressions can produce reliable coefficient estimates is drawn on the basis of time series’ properties tests and cointegration tests. The performance of the simple-form Taylor equation is compared to its alternative forms through forecasting exercises. The study has shown that the extended version of the Taylor rule with interest rate smoothing and augmented with the real exchange rate, the policy rate of the EU and oil prices can be viewed as a close approximation of Norges Bank’s monetary policy and can be used for forecasting purposes.

The goal of this final year project is to investigate various techniques to up-convert a baseband signal into radio frequency signals, and to investigate the practical problems encountered in an offset phase locked loop design by implementation. Phase locked loops are commonly used in radio transmitters and receivers to generate accurate RF signals from a low-frequency reference. This thesis will highlight some of the problems and strengths of various up-conversion schemes, and suggest an offset-PLL architecture free from many of those problems. An offset-PLL is often used in mobile communication systems where the required levels of out of band transmission are tough and the use of superheterodyne up-conversion cannot be used due to spectrum or bandwidth requirements. However a drawback of an offset-PLL is the high locking time; this can render the offset-PLL useless in TDMA communication systems. This problem among others has been studied theoretically as well as practically on an actual implementation of an offset-PLL for mobile communications. The offset-PLL was designed and manufactured as part of this project.