Receiver Configuration Research Articles

A Novel Receiver Design and Maximum-Likelihood Detection for Distributed MIMO Systems in Presence of Distributed Frequency Offsets and Timing Offsets

In distributed multi-input multi-output (MIMO) systems, antennas may not be able to utilize common oscillators at the transmitter side or the receiver side. Consequently, there are multiple carrier frequency offsets (CFOs) and multiple timing offsets (TOs) due to distributed antennas that may significantly degrade the system performance if not properly addressed. In this paper, we analyze the effect of multiple CFOs and multiple TOs on receiver signal energy at the front end of each receive antenna pulse matched filter output in a distributed MIMO system. We then propose a novel receiver design for distributed MIMO systems that can accommodate multiple CFOs and multiple TOs. The proposed receiver structure utilizes a bank of pulse matched filters at each receive antenna where each filter accommodates one CFO specifically. Each filter output is then sampled at the symbol rate, with sampling timing selected according to the corresponding TO, followed by an information symbol detector. For the proposed receiver configuration, we derive the maximum-likelihood (ML) symbol detector for both space-time block coded and uncoded distributed MIMO systems. In addition, we design sub-optimal detectors and show that under certain conditions, the sub-optimal detectors perform close to the ML-optimal detector with significantly lower complexities. Extensive simulation studies illustrate our theoretical development for distributed MIMO systems with various transceiver configurations and channel conditions. The simulation results indicate that the proposed receiver structure together with the ML detection offers significant performance gains compared to the current state of the art.

Digital compensation of the sideband-rejection ratio in a fully analog 2SB sub-millimeter receiver

Context. In observational radio astronomy, sideband-separating receivers are preferred, particularly under high atmospheric noise, which is usually the case in the sub-millimeter range. However, obtaining a good rejection ratio between the two sidebands is difficult since, unavoidably, imbalances in the different analog components appear. Aims. We describe a method to correct these imbalances without making any change in the analog part of the sideband-separating receiver, specifically, keeping the intermediate-frequency (IF) hybrid in place. This opens the possibility of implementing the method in any existing receiver. Methods. (i) We have built hardware to demonstrate the validity of the method and tested it on a fully analog receiver operating between 600 and 720 GHz. (ii) We have tested the stability of calibration and performance versus time and after full resets of the receiver. (iii) We have performed an error analysis to compare the digital compensation in two configurations of analog receivers, with and without intermediate-frequency hybrid. Results. (i) An average compensated sideband-rejection ratio of 46 dB is obtained. (ii) Degradation of the compensated sideband rejection ratio on time and after several resets of the receiver is minimal. (iii) A receiver with an IF hybrid is more robust to systematic errors. Moreover, we have shown that the intrinsic random errors in calibration have the same impact for configuration without IF hybrid and for a configuration with IF hybrid with analog rejection ratio better than 10 dB. Conclusions. We demonstrate that compensated rejection ratios above 40 dB are obtained even in the presence of high analog rejection. Further, we demonstrate that the method is robust allowing its use under normal operational conditions at any telescope. We also demonstrate that a full analog receiver is more robust against systematic errors. Finally, the error bars associated with the compensated rejection ratio are almost independent of whether IF hybrid is present or not.

The Galperin source: A novel efficient multicomponent seismic source

Multicomponent acquisition enables a more complete observation of the seismic wavefield compared with single-component measurements and has therefore experienced increased interest in the past few decades. Whereas the use of multicomponent receivers is well-established, efficient and effective multicomponent sources are still difficult to realize. One of the main drawbacks of common multicomponent sources is that the source coupling differs for different components. Differences in the source coupling can lead to amplitude variations introducing uncertainties when jointly analyzing data from two or three components (e.g., for multicomponent polarization analysis). To overcome this problem, we have designed a new multicomponent vector source, referred to as the Galperin source. The design is inspired by the Galperin receiver configuration, and it consists of three orthogonal source vectors ([Formula: see text], [Formula: see text], and [Formula: see text]), which all have the same inclination relative to the horizontal. Using the Galperin configuration, three orthogonal source components can be acquired without moving the source and changing the source coupling, which also increases acquisition efficiency. We built a prototype of the Galperin source and compared it with other multicomponent sources used for near-surface investigations. Comparisons in the time and frequency domains indicate a good agreement between data acquired using the Galperin source and other, more conventional, sources. However, because the three source acquisition vectors [Formula: see text], [Formula: see text], and [Formula: see text] and the resulting processing coordinates [Formula: see text], [Formula: see text], and [Formula: see text] are linked by a rotational matrix, errors on one component can project into others. Therefore, precise leveling of the Galperin source and identical source strength for all three source components is essential to minimize errors.

Analysis of frontal eddies effect and horizontal refraction in Gulf of Mexico with Hybrid Coordinate Ocean Model (HYCOM)

The cold and warm water carried by the eddies can significantly change the structure of the sound speed field, which is the key factor affecting long range deep-water sound propagation. Investigations of individual eddies have typically employed extensive deep bathy thermography readings. However, these procedures typically require a high density of readings throughout the oceanic region containing the eddy, requiring fairly extensive ship time and equipment. Further, results from these procedures are restricted to regions within the eddy where data were acquired. Fortunately, with the development of ocean models, it is convenient to obtain high-resolution ocean state estimates in global ocean as well as in regional ocean areas. In this presentation, we use the Hybrid Coordinate Ocean Model (HYCOM) extensively for high-resolution simulations to quantify the effects of vertical and horizontal refraction caused by a realistic ocean environment and actual bathymetry in Gulf of Mexico. For fixed source and receiver configurations, the impact of frequency, source depth in received pressure field and influence of frontal eddies on the travel time (and arrival angle) are examined. Moreover, the scenario and computational approach for a simulated long-range transmitted signal through a dynamic ocean with eddies is presented. Depth-averaged transmission loss, which computed by averaging the acoustic pressure-squared in the water over depth, is used to facilitate the observation of 3D horizontal refraction through frontal eddies.

Information content of ship noise on a drifting volumetric array for passive environmental sensing

This study investigates the information content of ship noise received on a drifting volumetric array of hydrophones in shallow water marine environments for the purposes of conducting acoustic thermometry or other environmental inversions. Passive inversions for physical oceanographic parameters are conducted using travel time differences, determined by cross-correlating ship noise received on hydrophones suspended beneath drifting buoys. Ships are tracked using the Automatic Identification System (AIS). Information content gained from the inversion is assessed using traditional a-posteriori error analysis. Numerical simulations using a standard normal mode propagation model are used to test limitations of the proposed approach with respect to frequency band, drifting receiver configuration, precision and accuracy of the inversion results, along with sensitivity to environmental and position mismatch. Performance predictions using this model are compared with results from a field experiment using at-sea data collected off the coast of New London, CT in Long Island Sound. Information gathered using passive acoustic inversion methods on drifting arrays can be used to constrain general circulation models (GCMs), in coastal environments, where ship noise is ubiquitous, environmental data are sparse, and the oceanography is dynamic and important for understanding large-scale ocean processes.

End-to-End Deep Learning of Optical Fiber Communications

In this paper, we implement an optical fiber communication system as an end-to-end deep neural network, including the complete chain of transmitter, channel model, and receiver. This approach enables the optimization of the transceiver in a single end-to-end process. We illustrate the benefits of this method by applying it to intensity modulation/direct detection (IM/DD) systems and show that we can achieve bit error rates below the 6.7\% hard-decision forward error correction (HD-FEC) threshold. We model all componentry of the transmitter and receiver, as well as the fiber channel, and apply deep learning to find transmitter and receiver configurations minimizing the symbol error rate. We propose and verify in simulations a training method that yields robust and flexible transceivers that allow---without reconfiguration---reliable transmission over a large range of link dispersions. The results from end-to-end deep learning are successfully verified for the first time in an experiment. In particular, we achieve information rates of 42\,Gb/s below the HD-FEC threshold at distances beyond 40\,km. We find that our results outperform conventional IM/DD solutions based on 2 and 4 level pulse amplitude modulation (PAM2/PAM4) with feedforward equalization (FFE) at the receiver. Our study is the first step towards end-to-end deep learning-based optimization of optical fiber communication systems.

CMOS Amplifier Receiver with AGC Bandwidth Circuit

This research work focuses on the concept of wireless optical communication system. A „CMOS Amplifier Receiver with Gain and Bandwidth Adjustment Capabilities‟ has been designed to detect the gain and bandwidth of the transmitted signal. Configurations of receivers had been designed using LMH6624 as the front-end transimpedance amplifier and the LMH6504 amplifier as the Automatic Gain Control (AGC) circuit. Furthermore, this research work also use LMH6732 amplifier at the output in order to have the capability of controlling the bandwidth. The output frequency response achieved by transimpedance amplifier using LMH6624 is 180.44 MHz and 144.61 MHz cut-off frequency after the AGC circuit while the controllable bandwidth amplifier by using LMH6732 produced is 75.32 MHz.

Programmable SDN-Enabled S-BVT Based on Hybrid Electro-Optical MCM

A programmable software-defined networking- enabled (SDN-enabled) sliceable bit rate variable transceiver based on hybrid electro-optical multicarrier modulation as a key enabler for superchannel generation in future 5G metro networks is proposed. Multiple discrete multitone signals can be multiplexed/demultiplexed with optical orthogonal transform processors such as spectral selective switches (SSSs). By implementing optical spectrally efficient transforms at the SSSs, we are able to generate a high-capacity superchannel to support the transmission targets envisioned in 5G networks. Specifically, the optimal transform can be programmed by the control plane through the corresponding SDN agents by suitably configuring the phase and attenuation of the SSS ports. Furthermore, with the adoption of multicarrier modulation formats, increased system/network flexibility is achieved. In this work, two different transceiver configurations have been proposed and assessed. They are based on intensity modulation with direct detection and amplitude modulation with coherent reception. A flexible receiver configuration selection is envisioned according to the target network requirements/condition.

Optical analysis of a novel collector design for a solar concentrated thermoelectric generator

This paper proposes a novel design for a solar concentrated collector for thermoelectric power generator (SCTEG), with optimum power output per unit length of collector. This collector consists of a parabolic trough concentrator (PTC) and a receiver mounted with two thermoelectric generators (TEGs) along the aperture of the concentrator. In addition to assessment of the conventional design parameters, this study investigates the effects of two new geometrical parameters on the optical performance of SCTEGs. These parameters are the vertex angle between the inner surfaces of the TEGs, and the focus offset, which is the displacement of the vertices of the TEGs above or below the focal point of the concentrator. A geometric model, which develops the basis of a ray-tracing technique for performing the optical analysis, is also described. Simulations performed for a set of design parameters showed that both parameters affected not only the optical efficiency but also the local flux distribution (LFD) on the surface of the TEGs. Iso-optical efficiency contours and numbers of LFDs were plotted, taking different values of these parameters to determine optical efficiencies. A flat-plate receiver configuration showed 85.2% optical efficiency but with a single high peak in LFD at the centre, which was undesirable. A slight alteration in vertex angle and focus offset resulted in same optical efficiency but improved LFD. The highest optical efficiency determined was 93.61% for the wide-receiver configuration. A thermodynamic analysis of the SCTEG design is also presented. This research work will assist in the development of more efficient SCTEGs.

Predictive performance modeling framework for a novel enclosed particle receiver configuration and application for thermochemical energy storage

Concentrating solar power (CSP) plants can provide dispatchable power with a thermal energy storage capability for increased renewable-energy grid penetration. Particle-based CSP systems permit higher temperatures, and thus, potentially higher solar-to-electric efficiency than state-of-the-art molten-salt heat-transfer systems. This paper describes a detailed numerical analysis framework for estimating the performance of a novel, geometrically complex, enclosed particle receiver design. The receiver configuration uses arrays of small tubular absorbers to collect and subsequently transfer solar energy to a flowing particulate medium. The enclosed nature of the receiver design renders it amenable to either an inert heat-transfer medium, or a reactive heat-transfer medium that requires a controllable ambient environment. The numerical analysis framework described in this study is demonstrated for the case of thermal reduction of CaCr0.1Mn0.9O3-δ for thermochemical energy storage. The modeling strategy consists of Monte Carlo ray tracing for absorbed solar-energy distributions from a surround heliostat field, computational fluid dynamics modeling of small-scale local tubular arrays, surrogate response surfaces that approximately capture simulated tubular array performance, a quasi-two-dimensional reduced-order description of counter-flow reactive solids and purge gas, and a radiative exchange model applied to embedded-cavity structures at the size scale of the full receiver. In this work we apply the numerical analysis strategy to a single receiver configuration, but the framework can be generically applicable to alternative enclosed designs. We assess sensitivity of receiver performance to surface optical properties, heat-transfer coefficients, solids outlet temperature, and purge-gas feed rates, and discuss the significance of model assumptions and results for future receiver development.

Levelized cost of electricity evaluation of liquid sodium receiver designs through a thermal performance, mechanical reliability, and pressure drop analysis

The receiver in a concentrated solar power (CSP) tower system accounts for a considerable proportion of plant capital costs, and its role in converting radiant solar energy into thermal energy affects the cost of generated electricity. It is imperative to utilize a receiver design that has a high thermal efficiency, excellent mechanical integrity, minimal pressure drop, and low cost in order to maximize the potential of the CSP system. In the present work, thermal, mechanical, and hydraulic models are presented for a liquid tubular billboard receiver in a representative CSP plant. A liquid sodium heat transfer fluid as well as a number of receiver configurations of heat transfer area, tube diameter, and tube material have been analysed. The thermal analysis determines tube surface temperatures for an incident heat flux, thereby allowing for the calculation of thermal losses and efficiency. The mechanical analysis is carried out to establish creep deformation and fatigue damage that the receiver may undergo through a life service. The hydraulic analysis is concerned with calculating the required pumping power for each configuration. Results show that thermal efficiency increases for a decreasing heat transfer area, however reducing receiver area comes at the penalty of increasing tube surface temperatures and thermal stresses. The selection of tube diameter is critical, with small diameters yielding the greatest thermal efficiency and mechanical life, however the increased pressure drop reduces the overall plant efficiency due to a necessary increase in pumping power. The optimum receiver configuration is established by finding an appropriate trade-off between thermal performance, service life, pressure drop, and material costs, by using the levelized cost of electricity (LCOE) as the objective function. The analysis highlights necessary trade-offs required to optimise the design of a solar receiver.

Evaluation of acoustic telemetry grids for determining aquatic animal movement and survival

AbstractAcoustic telemetry studies have frequently prioritized linear configurations of hydrophone receivers, such as perpendicular from shorelines or across rivers, to detect the presence of tagged aquatic animals. This approach introduces unknown bias when receivers are stationed for convenience at geographic bottlenecks (e.g. at the mouth of an embayment or between islands) as opposed to deployments following a statistical sampling design.We evaluated two‐dimensional acoustic receiver arrays (grids: receivers spread uniformly across space) as an alternative approach to provide estimates of survival, movement and habitat use. Performance of variably spaced receiver grids (5–25 km spacing) was evaluated by simulating (1) animal tracks as correlated random walks (speed: 0.1–0.9 m/s; turning angleSD: 5–30°); (2) variable tag transmission intervals along each track (nominal delay: 15–300 s); and (3) probability of detection of each transmission based on logistic detection range curves (mid‐point: 200–1,500 m). From simulations, we quantified (i) time between successive detections on any receiver (detection time), (ii) time between successive detections on different receivers (transit time), and (iii) distance between successive detections on different receivers (transit distance).In the most restrictive detection range scenario (200 m), the 95th percentile of transit time was 3.2 days at 5 km, 5.7 days at 7 km and 15.2 days at 25 km grid spacing; for the 1,500 m detection range scenario, it was 0.1 days at 5 km, 0.5 days at 7 km and 10.8 days at 25 km. These values represented upper bounds on the expected maximum time that an animal could go undetected. Comparison of the simulations with pilot studies on three fishes (walleyeSander vitreus, common carpCyprinus carpioand channel catfishIctalurus punctatus) from two independent large lake ecosystems (lakes Erie and Winnipeg) revealed shorter detection and transit times than what simulations predicted.By spreading effort uniformly across space, grids can improve understanding of fish migration over the commonly employed receiver line approach, but at increased time cost for maintaining grids.

Comparative thermodynamic analysis of densely-packed concentrated photovoltaic thermal (CPVT) solar collectors in thermally in-series and in-parallel receiver configurations

Abstract In this study, two densely-packed concentrated photovoltaic thermal (CPVT) solar collector configurations are optically and thermodynamically designed and analyzed and then exergoeconomically and environmentally assessed and compared. The designs are composed of parabolic dish concentrators, multi-junction photovoltaic (MJPV) cells, segmented thermoelectric generator (sTEG) couples with interconnectors, and finned minichannel heat extractors (mHXs). In configuration I, the receiver assembly components are connected thermally in-series whereas in configuration II they are connected thermally in-parallel. Geometric relations are employed to size the concentrator with design evaluations taking place with the aid of ray trace simulations. To better homogenize the reflected flux, the receiver is slightly shifted from the effective focal plane of the concentrator. Optical analysis reveals that the dish reflector is very sensitive to incidence angle deviations. It is found that the thermally in-series configuration offers an average annual exergy efficiency of 29.1% compared to 19.3% for the thermally in-parallel configuration. Both configurations offer comparable average annual energy efficiencies with a slight environmental and exergoeconomic advantage towards the thermally in-parallel configuration. The thermally in-series configuration is shown to provide a higher economic and thermodynamic value when electrical output is given preference over thermal output. The thermally in-parallel configuration, on the other hand, is favored in applications where thermal energy streams at multiple outlet temperatures are simultaneously desired, including a high-temperature thermal output. From an environmental viewpoint, both configurations are found capable of displacing a considerable amount of primary energy and CO2-equivalent emissions. While from an exergoeconomic viewpoint, for a system lifetime of 25 years, it is shown that the investment cost needs to be brought to approximately 21,000 AED for the proposed CPVT units to yield a positive lifecycle net present value (LCNPV). The annual escalation rate of electricity is observed to have a significant effect on the LCNPV of the collectors. Both environmental and exergoeconomic performance indices are shown to be sensitive to the thermal energy application meant for the CPVT collectors. Exergy analysis reveals that a drop in electrical exergy is offset by a rise in thermal exergy when higher system operation temperatures are used. The performance of both designs is simulated and compared on a monthly basis using weather data of Abu Dhabi, UAE.

Analysis of the performance of linear Fresnel collectors: Encapsulated vs. evacuated tubes

In order to reduce the cost of the produced electricity, the Linear Fresnel Collector (LFC) system is a promising Concentrated Solar Power (CSP) technology. In this paper a detailed study is conducted aimed at the assessment of the heat losses from the receiver of a real 1 MWe pilot plant based on the Fresnel collector and cooled with a thermal oil. The receiver unit, which consists of an absorber tube and a compound parabolic concentrator (CPC), is investigated numerically in order to determine the receiver performance in different wind directions. Two receiver configurations are analyzed: a simply encapsulated one and an evacuated one. In the latter case, high vacuum conditions are reached in the gap between the absorber tube and the glass cover, whereas in the former case, air at ambient pressure fills the gap. The spatial distribution of the heat flux absorbed by the absorber tube and by the glass cover is determined by means of an optical analysis, conducted with the Monte Carlo based open-source ray-tracing tool Tonatiuh, and it is the driver of the ensuing thermal fluid dynamic analysis. A reference operation condition is studied in detail by means of a 1D model that solves the energy balance for the coolant along the entire length of the receiver. The characterization of the 1D model requires an accurate, multi-dimensional computational fluid dynamic (CFD) analysis, based on the commercial STAR-CCM+ code, which aims at determining the useful heat transferred to the coolant and the convective and radiative heat losses as a function of the oil temperature. A 2D CFD model is used to simulate the thermal behavior of the receiver at different locations along its axis in case of no wind or wind blowing across the collector axis. A 3D CFD model is adopted to study the impact of the wind blowing along the collector axis. The external air is considered in the computational domain in both CFD models, to be able to accurately assess the convective share of the heat losses. At the end, the oil temperature profile along the receiver tube, as well as the heat losses and the thermal efficiency trends, are presented and discussed. The 2D model is also exploited to perform an annual analysis, varying the solar flux and the sun position, but considering just a single wind direction. The results of our analysis indicate that the benefit of using an evacuated tube depends on the heat absorbed on the linear receiver, which depends in turn on the solar flux and on the sun position. The annual-based performance improvement obtained using an evacuated tube is not dramatic, due to the relatively low temperatures of the receiver. Moreover, this analysis also concludes that the receiver performance is only slightly affected by the wind direction and intensity up to ∼ 4 m/s, due to the presence of the CPC that protects the receiver from the external air stream.

DEVELOPMENT OF OPTICAL WIRELESS RECEIVER AMPLIFIER USING HYBRID ENHANCEMENT

In the new communication era, signal will be transmit to the receiver via wireless. However, the signal might be loss during the transmission. Therefore, the signal received at the receiver is totally not originally from the transmitter. In some cases the signal must be amplified. This project will focuses on the concept of wireless optical in receiver communication system. The objectives of this project is to design a receiver amplifier using hybrid bandwidth enhancement in the approximately of Giga hertz range. The receiver amplifier is designed using Micro-Cap. The configuration of this design receiver is by using combination of bootstrapping and cascade technique. Bootstrapping technique offers the reduction on the photo detector capacitances which is the main limiting factor for the bandwidth of optical wireless front-end receiver. While, the cascade technique is used to arrange the electrical components such as transistor. Using the designed receiver Bootstrap Amplifier with Double Peaking Coil has been designed and fabricated. The cut-off frequency for this circuit is 400MHz.

A Hybrid Electric and Thermal Solar Receiver

Summary Solar energy offers a promising renewable energy source; however, it is expensive to store electricity from photovoltaics (PV), the most widely deployed solar electricity technology. Solar thermal energy technologies can be paired with inexpensive thermal storage, but are more expensive overall. We have developed a solar receiver that combines PV and solar thermal systems to efficiently convert solar radiation to electricity (to be used immediately) and thermal energy (to be stored and converted to electricity on demand). This paper describes the Hybrid Electric And Thermal Solar (HEATS) receiver and models its performance. An idealized model predicts high solar-to-electricity efficiency (35.2%) with high dispatchability (44.2% of electricity from thermal energy) at an operating temperature of 775 K. Modeling using measured performance values for HEATS subcomponents predicts 26.8% efficiency and 81% dispatchability with silicon PV and 28.5% efficiency and 76% dispatchability with gallium arsenide PV, both operating at 700 K.

Polarization independent polymer waveguide tunable receivers incorporating a micro-optic circulator

In order to simplify the receiver configuration in a wavelength division multiplexed optical fiber network, compact wavelength tunable filters have long been expected to be used as channel selectors. Bragg reflector inherently has the most suitable reflection spectrum for filtering a single wavelength from the densely multiplexed wavelength signal. Polymer has high thermo-optic coefficient and good thermal insulation property compared to the other optical waveguide materials such as silicon and silica materials. This can be used to broadly tune the reflection spectrum of Bragg reflector using a simple micro-heater. In this work, a micro-optic circulator component and a polymeric Bragg reflector device are assembled to produce a small form factor tunable receiver. Compared to the integrated-optical versions, the micro-optics are based on well-developed manufacturing processes and can achieve competitive production yields. The device exhibits high reflectivity with a flat top passband, and a polarization dependence of 0.06 nm achieved by virtue of the low birefringence of LFR polymer, which make a significant contribution to the implementation of polarization independent tunable receiver. The wavelength tuning range of 40 nm is demonstrated by using a bottom located heater with a groove for heat isolation.

Scaling effects of a novel solar receiver for a micro gas-turbine based solar dish system

Laboratory-scale component testing in dedicated high-flux solar simulators is a crucial step in the development and scale-up of concentrating solar power plants. Due to different radiative boundary conditions available in high-flux solar simulators and full-scale power plants the temperature and stress profiles inside the investigated receivers differ between these two testing platforms. The main objective of this work is to present a systematic scaling methodology for solar receivers to guarantee that experiments performed in the controlled environment of high-flux solar simulators yield representative results when compared to full-scale tests. In this work the effects of scaling a solar air receiver from the integration into the OMSoP full-scale micro gas-turbine based solar dish system to the KTH high-flux solar simulator are investigated. Therefore, Monte Carlo ray-tracing routines of the solar dish concentrator and the solar simulator are developed and validated against experimental characterization results. The thermo-mechanical analysis of the solar receiver is based around a coupled CFD/FEM-analysis linked with stochastic heat source calculations in combination with ray-tracing routines. A genetic multi-objective optimization is performed to identify suitable receiver configurations for testing in the solar simulator which yield representative results compared to full-scale tests. The scaling quality is evaluated using a set of performance and scaling indicators. Based on the results a suitable receiver configuration is selected for further investigation and experimental evaluation in the KTH high-flux solar simulator.

Interpretation of deep directional resistivity measurements acquired in high-angle and horizontal wells using 3-D inversion

The interpretation of resistivity measurements acquired in high-angle and horizontal wells is a critical technical problem in formation evaluation. We develop an efficient parallel 3-D inversion method to estimate the spatial distribution of electrical resistivity in the neighbourhood of a well from deep directional electromagnetic induction measurements. The methodology places no restriction on the spatial distribution of the electrical resistivity around arbitrary well trajectories. The fast forward modelling of triaxial induction measurements performed with multiple transmitter–receiver configurations employs a parallel direct solver. The inversion uses a pre-conditioned gradient-based method whose accuracy is improved using the Wolfe conditions to estimate optimal step lengths at each iteration. The large transmitter–receiver offsets, used in the latest generation of commercial directional resistivity tools, improve the depth of investigation to over 30 m from the wellbore. Several challenging synthetic examples confirm the feasibility of the full 3-D inversion-based interpretations for these distances, hence enabling the integration of resistivity measurements with seismic amplitude data to improve the forecast of the petrophysical and fluid properties. Employing parallel direct solvers for the triaxial induction problems allows for large reductions in computational effort, thereby opening the possibility to invert multiposition 3-D data in practical CPU times.

Digital Signal Processing for Short-Reach Optical Communications: A Review of Current Technologies and Future Trends

Driven primarily by cloud service and data-center applications, short-reach optical communication has become a key market segment and growing research area in recent years. Short-reach systems are characterized by direct detection-based receiver configurations and other low-cost and small form factor components that induce transmission impairments unforeseen in their coherent counterparts. Innovative signaling and digital signal processing (DSP) play a pivotal role in enabling these components to realize their ultimate potentials and meet data rate requirements in cost-effective manners. This paper presents an overview of recent DSP developments for short-reach communications systems and discusses future trends.