International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / For simpler implementations of ultra high bit rate systems, combined analog/digital techniques, described here in, provide implementations with the smallest number of component count utilizing minimal “real-estate” and smallest DC power. While digital implementations with tradition Read Only Memory (ROM) and Digital to Analog Converters (DAC’s) have been proven in several commercial, NASA -CCSDS recommended, and U.S. DoD-IRIG standardized Feher’s QPSK (FQPSK) [2,3] products, such implementations can be further simplified, and in particular for ultra high bit rate product applications. Several waveform generating techniques such as linear approximation, analog approximation and mixed analog and linear approximations are investigated using preliminary simulation results.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / In 1992, international space agencies became concerned that increasing frequency band congestion, together with attempts by the mobile telephone industry to obtain additional bandwidth, would result in substantially more interference incidents. The CCSDS undertook a technical study to identify and recommend more bandwidth efficient modulation schemes, which would permit more users to co-exist in a frequency band while reducing interference incidents. This paper describes the contribution of the Jet Propulsion Laboratory (JPL) to that effort.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Commercial FQPSK-B receivers traditionally use symbol-by-symbol detection and have a 2 dB Eb=No loss relative to ideal QPSK at a bit error rate (BER) of 10^(-5). An enhanced FQPSK-B receiver using a Viterbi algorithm (VA) to perform trellis decoding is simulated and shown to have a 1.2 dB Eb=No improvement over symbol-by-symbol detection for 10^(-5)5 BER at the cost of increased complexity. A simplified Viterbi receiver with a reduced trellis and significantly less complexity is introduced with only a slight BER degradation compared to the full Viterbi receiver. In addition, a theoretical bit error probability expression for the symbol-by-symbol FQPSK-B receiver is derived and compared with simulation results.

Li, Pulan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (p. 60-66). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of wavelength division multiplexed passive optical network (WDM-PON) and colorless optical network unit (ONU) --- p.1 / Chapter 1.2 --- Implementation of colorless ONU --- p.4 / Chapter 1.3 --- Rayleigh backscattering in WDM-PON --- p.6 / Chapter 1.4 --- Motivation of this thesis --- p.9 / Chapter 1.5 --- Outline of this thesis --- p.11 / Chapter Chapter 2 --- Previous works of remodulation for WDM-PON --- p.12 / Chapter 2.1 --- Introduction --- p.12 / Chapter 2.2 --- Devices utilized by colorless ONU in remodulation schemes --- p.13 / Chapter 2.2.1 --- Injection-locked Fabry-Perot laser diode at ONU --- p.13 / Chapter 2.2.2 --- Reflective semiconductor optical amplifier --- p.15 / Chapter 2.2.3 --- Reflective electro-absorption modulator and semiconductor optical amplifier (REAM-SOA) --- p.17 / Chapter 2.3 --- Modulation methods in remodulation schemes --- p.18 / Chapter 2.4 --- Summary --- p.23 / Chapter Chapter 3 --- A remodulation scheme based on time-interleaved DPSK modulation format --- p.25 / Chapter 3.1 --- Introduction --- p.25 / Chapter 3.2 --- Operation principle: time-interleaving technology for phase-modulated signal --- p.27 / Chapter 3.3 --- System architecture --- p.28 / Chapter 3.4 --- Experimental results and discussion --- p.31 / Chapter 3.5 --- Effect of timing misalignment on proposed remodulation scheme --- p.33 / Chapter 3.6 --- Summary --- p.35 / Chapter Chapter 4 --- Enhanced Tolerance to Rayleigh Backscattering in Remodulation Scheme Using Time-Interleaved DPSK Format --- p.37 / Chapter 4.1 --- Introduction --- p.37 / Chapter 4.2 --- Studies on Rayleigh backscattering suppression in optical domain --- p.39 / Chapter 4.2.1 --- RB suppression in carrier-distributed schemes --- p.39 / Chapter 4.2.2 --- RB suppression in remodulation schemes --- p.40 / Chapter 4.2 --- Experimental setup and results --- p.42 / Chapter 4.3 --- Discussion on RB suppression effect of the proposed scheme --- p.46 / Chapter 4.3.1 --- Theoretical study and simulation results --- p.46 / Chapter 4.3.2 --- Experimental demonstration of spectral relationship between signals and RB crosstalk --- p.49 / Chapter 4.4 --- Summary --- p.53 / Chapter Chapter 5 --- Conclusion and Future Works --- p.55 / Chapter 5.1 --- Conclusion of this thesis --- p.55 / Chapter 5.2 --- Future works --- p.57 / List of Publications --- p.59 / Bibliography --- p.60

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2017. / This dissertation presents the development of a quadrature phase shift keying (QPSK) demodulator for nanosatellites that complies with both the limited resources associated with nanosatellites as well as the flexibility and configurability required for a software defined radio (SDR) platform. This research project is a component of a bigger project, which is to develop a high-speed receiver for nanosatellites, and aims to provide a practical solution to the need for communication technologies that support emerging nanosatellite applications, such as Earth observation and communications. The development of the QPSK demodulator follows an all-digital implementation approach. The main reason for selecting this approach is to have a system that is flexible and reconfigurable to comply with the SDR requirements. Another reason for selecting this approach is to comply with the low noise system, low power consumption as well as the small size and weight requirements associated with nanosatellites. The QPSK demodulator is implemented on an IGLOO2 Field Programmable Gate Array (FPGA), due to its robustness to radiation and high-speed capability. Initially, the techniques used to design each subsystem of the QPSK demodulator are selected. Then, algorithms to digitally implement the designed subsystems are produced. Thereafter, the code for the digital QPSK demodulator is written and verified in Matlab first. The simulation of the Matlab-based QPSK demodulator performs satisfactorily. Subsequently, the code to implement the QPSK demodulator on an FPGA (IGLOO2) has been written in Libero, using VHSIC Hardware Description Language (VHDL). The resulting FPGA-based QPSK demodulator has been emulated in Libero (an integration and development environment (IDE) for Microsemi FPGAs) using a test-bench as well as other analysis tools. The test-bench results are visualized using Modelsim. The results show that the demodulator can support data rates up to 13.25 Mbps if 16 samples-per-symbols are used, and up to 26.5 Mbps if 8 samples-per-symbols are used. It also has a very good bit-error-rate performance, which is simulated to be within a factor of 5 of the theoretical limit of QPSK modulation. Finally, the demodulator consumes less than 15 mW at the maximum operating speed. and has been coded to mitigate the effects of space radiation and noise contriution by the demodulator itself.

The circadian system controls 24-hour cycles of behavior and physiology, such as rest-activity and feeding rhythms. The human circadian system synchronizes with, or entrains to, the light/dark cycle (sunrise/sunset) to promote activity and food consumption during the day and rest at night. However, strict work schedules and nighttime light exposure impair proper entrainment of the circadian system, resulting in chronic circadian misalignment. Numerous studies have shown that chronic circadian misalignment results in poor health. Therefore, therapeutic interventions that could shift circadian rhythms and alleviate circadian misalignment could broadly impact public health. Although light is the most salient time cue for the circadian system, several laboratory studies have shown that exercise can also entrain the internal circadian rhythm. However, these studies were performed in controlled laboratory conditions with physically-active participants. The purpose of this study was to determine whether timed exercise can phase advance (shift earlier) the internal circadian rhythm in sedentary subjects in free-living conditions. Fifty-two young, sedentary adults (16 male, 24.3±0.76 yrs) participated in the study. As a marker of the phase of the internal circadian rhythm, we measured salivary melatonin levels (dim light melatonin onset: DLMO) before and after 5 days of timed exercise. Participants were randomized to perform either morning (10h after DLMO) or evening (20h after DLMO) supervised exercise training for 5 consecutive days. We found that morning exercisers had a significantly greater phase advance than evening exercisers. Importantly, the morning exercisers had a 0.6h phase advance, which could theoretically better align their internal circadian rhythms with the light-dark cycle and with early-morning social obligations. In addition, we also found that baseline DLMO, a proxy for chronotype, influenced the effect of timed exercise. We found that for later chronotypes, both morning and evening exercise advanced the internal circadian rhythm. In contrast, earlier chronotypes had phase advances when they exercised in the morning, but phase delays when they exercised in the evening. Thus, late chronotypes, who experience the most severe circadian misalignment, may benefit from exercise in the morning or evening, but evening exercise may exacerbate circadian misalignment in early chronotypes. Together these results suggest that personalized exercise timing prescriptions based on chronotype could alleviate circadian misalignment in young adults.

Macroalgae are an important part of the coral reef ecosystem that has largely been overlooked. However, in the past few decades their abundances have increased and this has been attributed to combinations of coral mortality opening up space in the reef, decreased grazing and increased nutrient load in reefs. This dissertation illustrates a novel means of investigating the effect of various growth and disturbance factors on the dynamics of macroalgae at three different levels (individual, population and 3-species community). Macroalgae are modular and clonal organisms that have differing morphologies depending on the environment to which they are exposed. These traits were exploited in order to understand the factors that were acting on the dominant and common macroalgae in the Florida Reef Tract: Halimeda tuna, Halimeda opuntia and Dictyota sp. The agent-based model SPREAD (SPatially-explicit REef Algae Dynamics) was developed to incorporate the key morphogenetic characteristics of clonality and morphological plasticity. It revolves around the iteration of macroalgal module production in response to light, temperature, nutrients, and space availability, while fragmentation is the source for mortality or new individuals. These processes build the individual algae then the population. The model was parameterized through laboratory experiments, existing literature and databases and results were compared to independently collected field data from four study sites in the Florida Keys. SPREAD was run using a large range of light, temperature, nutrient and disturbance (fragmentation without survival) levels and yielded six morphological types for Halimeda tuna, and two each for Halimeda opuntia and Dictyota sp. The model morphological types that matched those measured in two inshore patch reefs (Cheeca Patch and Coral Gardens) and two offshore spur and groove reefs (Little Grecian and French Reef), were formed in conditions that were similar to the environmental (light, nutrient and disturbance) conditions in the field sites. There were also differences between species in the important factors that influenced their morphologies, wherein H. opuntia and Dictyota were more affected by disturbance than growth factors, while H. tuna morphology was affected by both. Allowing for fragmentation with survival in the model resulted in significantly higher population abundances (percent cover and density). The highest abundances were achieved under high fragment survival probabilities and a high disturbance level (but not large fragment sizes). Incorporating fragmentation with survival and simulating the variations in light, nutrients and disturbance between the inshore patch reefs and offshore spur and groove reefs in SPREAD led to comparable abundances of Halimeda in the virtual reef sites. Adding competition for space and light and epiphytism by Dictyota on the two Halimeda species suggests that it can regulate the populations of the three macroalgae. However, comparing model abundances to the field, competition may not be a strong regulating force for H. tuna in all the sites and H. opuntia in the patch reefs. H. opuntia in the offshore reefs is possibly competitively regulated. Although SPREAD was not able to capture the patterns in the population abundance of Dictyota, this points to the potential importance of other morphometrics not captured by the model, a variation in growth curves between reef habitats, or the differential contribution of sexual reproduction.

In the current transmission system, the information bandwidth of the optical fiber communication system is limited by optical amplifier bandwidth, and more efficient use of bandwidth is a very important issue. Amplitude and phase shift keying (APSK) is an advanced modulation scheme to improve the spectral efficiency and can effectively increase the transmission capacity. Certainly, APSK format has a good potential for development. This master thesis is focusing on that to study the transmission performance of the APSK format using digital coherent receiver. As the extinction ratio (ER) of the amplitude shift keying (ASK) signal affects the performances of the ASK signal and phase shift keying (PSK) signal simultaneously, the effect of the ER on the APSK transmission performance was studied. The APSK format has the trade-off between the performances of both the ASK signal and the PSK signal through the ER of the ASK signal. To overcome this issue, a method named zero-nulling method had been proposed, and this method solved the trade-off issue properly. At first, the amendment is to modify the digital coherent receiver program, confirmed that the digital coherent receiver program can correctly resolve APSK signal. Second, in this master thesis, I set up a 500km long optical fiber to measure the transmission performance under APSK format, and try to use recirculating loop system to further increase the transmission distance to several thousand kilometers. Finally, by further modify the receiver program to achieve APSK modulation of the zero-nulling method, and can prove its feasibility.

To fulfill the requirements of the operation in a wide power range, a parallel configuration with modular power factor correctors (PFCs) is proposed. Each PFC module is composed of a bridge-rectifier, a fly-back converter and associated passive filters. The fly-back converter is independently operated at a fixed frequency with a discontinuous inductor current. This allows the modules to achieve a high power factor and to regulate the output power with simple control. With the same duty-ratio and frequency, the total current will be distributed equally to each operating module without complex current sharing control. The operating modules are equally phase-shifted to take the advantages of the continuous current mode when operated at a higher power. Experiments were conducted to achieve a power rating of 1 kVA by operating 10 PFC modules in parallel. The duty-ratio of the operating modules is controlled by a micro-controller to regulate the output power in accordance with the load requirement. A complex programmable logic device (CPLD) is used for phase-shifting. All modules are operated in turn to share the operating cycles in a more equal manner. Experimental results demonstrate the parallel configuration can achieve the expected performances.

Cluster mass fraction is an elusive quantity to measure, calculate or estimate accurately for pulsed supersonic gas jets typical of intense laser experiments. The optimization of this parameter is critical for transient phase-matched harmonic generation in an ionized cluster jet at high laser intensity. We present an in-depth study of a rapid, noninvasive, single-shot optical method of determining cluster mass fraction f_c(r,t) at specified positions r within, and at time t after opening the valve of, a high-pressure pulsed supersonic gas jet. A ∼ 2 mJ fs pump pulse ionizes the monomers, causing an immediate drop in the jet’s refractive index n_jet proportional to monomer density, while simultaneously initiating hydrodynamic expansion of the clusters. The latter leads to a second drop in n_jet that is proportional to cluster density and is delayed by ∼ 1 ps. A temporally stretched probe pulse measures the 2-step index evolution in a single shot by frequency domain holography, enabling recovery of f_c. We present the theory behind recovery of f_c in detail. We also present extensive measurements of spatio-temporal profiles f_c(r, t) of cluster mass fraction in a high-pressure supersonic argon jet for various values of backing pressure P, and reservoir temperature T. / text