A space communication study Final report, 15 Sep. 1967 - 15 Sep. 1968

Transmitting and receiving analog and digital signals through noisy media - space communications stud

Transmissores-recetores de baixa complexidade para redes óticas

Traditional coherent (COH) transceivers allow encoding of information in both quadratures and the two orthogonal polarizations of the electric field. Nevertheless, such transceivers used today are based on the intradyne scheme, which requires two 90o optical hybrids and four pairs of balanced photodetectors for dual-polarization transmission systems, making its overall cost unattractive for short-reach applications. Therefore, SSB methods with DD reception, commonly referred to as self-coherent (SCOH) transceivers, can be employed as a cost-effective alternative to the traditional COH transceivers. Nevertheless, the performance of SSB systems is severely degraded. This work provides a novel SCOH transceiver architecture with improved performance for short-reach applications. In particular, the development of phase reconstruction digital signal processing (DSP) techniques, the development of other DSP subsystems that relax the hardware requirement, and their performance optimization are the main highlights of this research. The fundamental principle of the proposed transceiver is based on the reception of the signal that satisfies the minimum phase condition upon DD. To reconstruct the missing phase information imposed by DD, a novel DCValue method exploring the SSB and the DC-Value properties of the minimum phase signal is developed in this Ph.D. study. The DC-Value method facilitates the phase reconstruction process at the Nyquist sampling rate and requires a low intensity pilot signal. Also, the experimental validation of the DC-Value method was successfully carried out for short-reach optical networks. Additionally, an extensive study was performed on the DC-Value method to optimize the system performance. In the optimization process, it was found that the estimation of the CCF is an important parameter to exploit all advantages of the DC-Value method. A novel CCF estimation technique was proposed. Further, the performance of the DC-Value method is optimized employing the rate-adaptive probabilistic constellation shaping.Os sistemas de transcetores coerentes tradicionais permitem a codificação de informação em ambas quadraturas e em duas polarizações ortogonais do campo elétrico. Contudo, estes transcetores utilizados atualmente são baseados num esquema intradino, que requer dois híbridos óticos de 90o e quatro pares de foto detetores para sistemas de transmissão com polarização dupla, fazendo com que o custo destes sistemas seja pouco atrativo para aplicações de curto alcance. Por isso, métodos de banda lateral única com deteção direta, também referidos como transcetores coerentes simplificados, podem ser implementados como uma alternativa de baixo custo aos sistemas coerentes tradicionais. Contudo, o desempenho de sistemas de banda lateral única tradicionais é gravemente degradado pelo batimento sinal-sinal. Nesta tese foi desenvolvida uma nova arquitetura de transcetor coerente simplificada com um melhor desempenho para aplicações de curto alcance. Em particular, o desenvolvimento de técnicas de processamento digital de sinal para a reconstrução de fase, bem como de outros subsistemas de processamento digital de sinal que minimizem os requerimentos de hardware e a sua otimização de desempenho são o foco principal desta tese. O princípio fundamental do transcetor proposto é baseado na receção de um sinal que satisfaz a condição mínima de fase na deteção direta. Para reconstruir a informação de fase em falta causada pela deteção direta, um novo método de valor DC que explora sinais de banda lateral única e as propriedades DC da condição de fase mínima é desenvolvido nesta tese. O método de valor DC facilita a reconstrução da fase à frequência de amostragem de Nyquist e requer um sinal piloto de baixa intensidade. Além disso, a validação experimental do método de valor DC foi executada com sucesso em ligações óticas de curto alcance. Adicionalmente, foi realizado um estudo intensivo do método de valor DC para otimizar o desempenho do sistema. Neste processo de otimização, verificou-se que o fator de contribuição da portadora é um parâmetro importante para explorar todas as vantagens do método de valor DC. Neste contexto, é proposto um novo método para a sua estimativa. Por último, o desempenho do método de valor DC é otimizado recorrendo a mapeamento probabilístico de constelação com taxa adaptativa.Programa Doutoral em Engenharia Eletrotécnic

Secure Communications Systems Utilizing Pseudo-Noise Carriers and Sub-carriers

The current literature approaches the subject of communications from the optimum detector point of view, utilizing the principles set forth by Shannon, Davenport, Root, Bode, Peterson, Birdsall, Fox, Weiner, Siebert, Middleton, and many others to carry out detailed analysis of specific detectors, filters, and synchronization processes. This paper approaches communications from a systems point of view, dealing specifically with the family of pseudo-noise systems. The systems discussed are categorized into two groups, the pseudo-noise carrier and the pseudo-noise sub-carrier systems, with emphasis on multiplex techniques. All of the systems discussed are negative dB S/N systems with the exception of a wide-band TV video channel, and a detailed analysis of a representative pseudo-noise sequence of length 15 is given as a background in the auto-correlation functions, power spectral densities, and self-noise spectra which are the characterizing parameters of these waveforms.Lieutenant, United States NavyApproved for public release; distribution is unlimited

A Solid State VHF Single Sideband Transmitter

This research report investigates a unique method of generating single sideband power, which is particularly useful in transistorized transmitters operating at VHF frequencies. Radio frequency power id developed by class C amplifiers, rather than conventional class A or B amplifiers. Currently, VHF power transistors are not well adapted for use as linear amplifiers, and will function far better in the class C mode. A prototype VHF transmitter which develops single sideband power with nonlinear amplifiers was designed and constructed. The transmitter characteristics were measured and analyzed to establish the feasibility of the new design

Electron Nuclear Dynamics Simulations of Proton Cancer Therapy Reactions: Water Radiolysis and Proton-and Electron-Induced DNA Damage in Computational Prototypes

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Proton cancer therapy (PCT) utilizes high-energy proton projectiles to obliterate cancerous tumors with low damage to healthy tissues and without the side effects of X-ray therapy. The healing action of the protons results from their damage on cancerous cell DNA. Despite established clinical use, the chemical mechanisms of PCT reactions at the molecular level remain elusive. This situation prevents a rational design of PCT that can maximize its therapeutic power and minimize its side effects. The incomplete characterization of PCT reactions is partially due to the health risks associated with experimental/clinical techniques applied to human subjects. To overcome this situation, we are conducting time-dependent and non-adiabatic computer simulations of PCT reactions with the electron nuclear dynamics (END) method. Herein, we present a review of our previous and new END research on three fundamental types of PCT reactions: water radiolysis reactions, proton-induced DNA damage and electron-induced DNA damage. These studies are performed on the computational prototypes: proton + H2O clusters, proton + DNA/RNA bases and + cytosine nucleotide, and electron + cytosine nucleotide + H2O. These simulations provide chemical mechanisms and dynamical properties of the selected PCT reactions in comparison with available experimental and alternative computational results

Towards co-sintering of oxide-based inorganic solid-state batteries. Understanding and overcoming thetemperature barriers.

220 p.All inorganic solid-state batteries (SSBs) are considered the batteries of the future because of their superior energy density and safety. Their commercialization is in its infancy since further understanding of the materials and processing aspects is still required. Here we propose an oxide-based SSB model comprising NMC+LATP+carbon composite cathode, LATP solid electrolyte, and Li metal anode able to potentially convey an energy density of >300 Wh/kg and >700 Wh/l. A review of existing processing techniques of the selected materials indicates the necessity of very high densification temperatures to assure sufficient ionic conductivity and mechanical stability. The electrode and electrolyte need to be co-densified to avoid interfacial contact resistance, but the components of the composite cathode react at these elevated temperatures. In this work, the composite cathode thermal compatibility is first studied to determine the tolerance of the system under temperature, considering also the heating atmosphere and the decomposition reaction mechanism. In a second step, mitigation strategies to overcome the threshold limits identified have been examined, such as the selection of the carbon conducting additive and the impact of other additives. On the other hand, the realization that the threshold temperature is much lower than the conventional processing temperature requires the exploration of alternative low-temperature densification techniques. Hence a high-pressure low-temperature (HPLT) technique has been identified and initially investigated for oxide-based ceramic solid electrolyte densification. Our results show that this technique enables a significant reduction of the processing temperature and time compared to conventional sintering. Finally, preliminary investigations indicate that with further exploration of the HPLT technique, the realization of the proposed SSB model should be possible, resulting in significant gains of processing consumed energy.energiGUN

Actuation Techniques For Frequency Modulated MEMS Gyroscopes

This thesis focuses on the design and implementation of an analog actuation circuit for a novel frequency-modulated MEMS gyroscope. The gyroscope detects angular rotations as the difference between the natural frequencies of two closely spaced drive and sense modes rather than the magnitude of displacement in the sense direction. Furthermore, the actuation system features a resonant drive (RLC) circuit that amplifies the gyroscope actuation signal. The input to the circuit is an amplitude-modulated (AM) signal composed of a carrier signal modulated with a base signal that excites the gyroscope drive mode. The carrier frequency corresponds to the electrical resonance frequency of the drive circuit. This research develops techniques for the stabilization of the circuit output through close loop feedback. First, we attempt to increase the signal-to-noise ratio of the modulating signal by implementing feedback and feedforward control loops (AGC). The feedback controller closes the loop on the entire conditioning circuit for the modulating signal while the feedforward controller acts on the input signal to the conditioning circuit. The feedforward and the feedback controllers derive an error signal representing the signal noise by comparing the input and output signal, respectively, with a reference signal. However, we find that the breadboard circuit implementations of our control strategies performed similar to a baseline uncontrolled function generator due to the additional noise input from the breadboard and the additional components used to implement the controller, such as the amplifiers. Next, we develop a single-harmonic amplitude-stabilized actuation scheme for the gyroscope to minimize multi-frequency excitations and reduce amplitude fluctuations to improve the gyroscope precision. A low pass filter is applied to the AM signal to obtain a single sideband full carrier (SSB-FC) signal. Since the capacitance of RLC circuit changes due to the vibration of the gyroscope, this variation in capacitance causes a shift in the frequency response of the RLC circuit, resulting in variation in the circuit gain. Three feedback control topologies are implemented to stabilize the signal by first detecting the change in signal level, and then amplifying or attenuating the signal level in order to maintain a constant gyroscope actuation level. The control strategy with the best performance involves feeding back the RMS of the output signal to control the amplitude of the carrier signal and feeding back the average of the output signal’s envelope to control the bias level of the modulating signal. Using control this strategy, the peak magnitude at the carrier frequency dropped approximately 2% as the capacitance is varied from 15 pF to 16 pF, awhile the other two control strategies changed 9% and 6%