Single-photons sources are crucial devices in the development of practical quantum communication and quantum computation. However, such sources are still a technological challenge. One option is to use weak coherent states to mimic single-photon pulses or to produce a pair of photons with parametric down conversion and to detect one of them to herald the presence of the other. In this direction, the present work shows how to produce better approximations of single-photon pulses by using a nonlinear phase modulator in a Mach-Zehnder interferometer. The proposed scheme is explained and applications are discussed.
This paper presents a case study that illustrates the effect of positioning an isotropic broadband electric field probe in the vicinity of a metallic structure. The probe positioned on the vehicle's top is used on drive test for the evaluation of the radio frequency electromagnetic field in mobile mode. The drive test mode allows to increase the measurement capacity in a vast territorial extension, which has been adopted by the National Telecommunications Agency in Brazil. The simulation results demonstrate that there is an overestimation of the measured levels when close to the vehicle's metallic structure. This indicates that the mobile measurement method is conservative in the assessment of human exposure to radio frequency electromagnetic fields.
Quantum key distribution (QKD) allows secure communication between spatially distant users. It has been successfully implemented in fiber-based and free space optical networks. However, QKD has not been implemented in other important regions of the electromagnetic spectrum: millimeter- wave and THz regions. One of the reasons for this is that single- photon detectors in these regions are not easily available. In the present work, a proposal of a simple and cheap single-photon detector working in the mmWave and THz region, using glow discharge detector, is presented and its parameters are discussed.
Modern antennas have complex structures, and the design of these devices is a challenging task. The antenna optimization process uses electromagnetic simulations as an objective function, which have a high computational cost. Surrogate models are methods that can be used to increase computational efficiency by training machine learning techniques. This work investigates eight machine learning techniques to find which one is more suitable to be used as a surrogate model in the design of antennas. We propose a methodology for comparing and analyzing the techniques using the RMSE as the metric. For the case study, we present the design of a Quasi-Yagi antenna for operating at three resonance frequencies. The results demonstrate that the Gaussian Process model obtained the best performance, achieving an RMSE value of 1.251 in the case study.
Double-layer broadband absorber for Ku band of CaCu3Ti4O12 (CCTO), Carbonyl iron (CI) and MnZn Ferrite composites was studied. Based on combination of different composites and thicknesses, among the various combinations investigated the best result was observed for the structure formed by the junction of CI composite with 2 mm and MnZn ferrite composite with 3 mm. Reflection loss measurements showed that this double-layer absorbed more than 90% of EM wave within the 12,4 to 16,06 GHz frequency range.
Silicon nanophotonics is contributing to develop devices with small dimensions and low energy consumption. In space systems, whether in large or small satellites, such as CubeSat the demand for photonic devices has been growing, especially in the communication subsystem. For CubeSat the need to develop optical communication devices with reduced dimensions, low energy consumption and a precision aiming system, with no movable parts, is a challenge. In order to meet these requirements, this article presents a theoretical study on the use of a silicon nanophotonic device, in the form of Archimedean spiral waveguide, for phase modulation in Optical Phased Array antennas.
This paper analyzes the impact of the set of objective functions for the solution of the amplifier Adaptive Control of Operating Point (ACOP) problem using a Multi-objective optimization approach. We assessed four different configurations, one with three objectives and three with two objective functions. We observed that the configuration with three objective functions achieved a better diversity and generated a more diverse set of solutions for the decision-maker with no significant increase in computational time.
Frequency Domain Reflectometry (FDR) is a nondestructive and non-intrusive technology and is widely used to maintain coaxial cables and antennas. In this work, FDR was expanded to maintain anchor rods. Such rods are buried in soil to provide fixed support for multiple buildings (such as power transmission towers). Transmission line theory is used to detect and locate wear in metal structures. A high-frequency connector called MDSC (Microwave Device for Support and Connection) was previously designed to allow electromagnetic waves to propagate on two rods, one of which is the rod under test. Tests were performed by applying FDR to two rods manufactured with different fault locations. The results show the efficiency of using this technology to perform preventive maintenance and effectively locate failures on the rods. In addition, the measurement results have been reproduced in a simulation software. Both measured and simulated results are compared with each other and the difference between them is up to 11.24% of Voltage Standing Wave Ratio (VSWR).
The determination of the optical setup for the devices to maximize transmission quality is a challenging task. In this paper, we propose to jointly optimize the operating points of the optical amplifiers in the communication link and a linear pre-emphasis in the transmitters’ launch power. We deploy a multi-objective algorithm to maximize the performance of an optical link impaired by the amplified spontaneous emission noise (ASE) and gain distortions generated by a chain of erbium-doped fiber amplifiers (EDFA), aiming to maximize the minimum OSNR in all transmitted channels and minimize the overall cascade tilt. We analyzed two scenarios with different characteristics, and the simulation results indicate that the proposed optimization scheme achieves better performance outcomes (considering OSNR and tilt).
Integrated technological environments can be develop using information captured by wireless sensor networks. This class of networks operates for long periods of time, therefore low energy consumption devices are required. This paper measures the level of energy consumption during the communication period between two IoT-devices in sub-1GHz frequency operation without a specific native communication protocol. The analysis was made based on electric current measurements, obtained using different parameters to observe different possible cases. The device life expectancy was studied in commercial battery models. A life expectancy of device is 4.5 years in average considering several types of setups with periodical consumption.
Performance comparisons between visible light communication (VLC) systems based on orthogonal chirp division multiplexing (OCDM) and orthogonal frequency division multiplexing (OFDM) are presented in this paper. Unlike most of the related publications, in this work we compared OCDM and OFDM based VLC systems with the same equalization process, i.e., employing one tap equalizer in both systems. Sim...
Optimizing return loss for vias and high-density BGA (Ball Grid Array) areas is becoming important as signaling speed increases. Designing high speed PCB (Printed Circuit Board) without field solver simulations can cause severe SI (signal integrity) problems. In this paper, design and simulation methodologies are adopted to optimize 25 Gbps (Gigabit per second) high-speed serial links on a multilayer PCB. To improve signal integrity, return loss is lowered using two primary strategies. Initially, a differential via anti-pad impedance is optimized in a high-speed connector through a 3-D field solver approach. Then, advanced PCB layout techniques for BGA signals breakout (fan out) are employed from the ball to the outside of BGA area, and effectively demonstrated using field solver results. Therefore, an overall return loss improvement of approximately 8 dB is achieved between 5 to 7 GHz, enabling the design to pass 25GBASE-KR normative mask with a good margin.
This work shows an application of a hybrid Autoregressive Moving Average model proposed on a previous work. The scenario presented in this study is located in a city called Salinópolis in the coast of the Brazilian state of Pará. We worked in a different frequency range than that of the previous work. Now we are applying this model to the Brazilian cellular phone frequency. We worked at the range of 869 MHz to 880 MHz, which is the frequency range of one of the cell phone operators that attends the city of Salinópolis. We can see through the results of this study that the model performed its fittings feasibly in the new scenario and shows good signs of its application to a greater variety of scenarios.
This article describes a propagation measurement system based on a low-cost software-defined radio unit, used here within the UHF range. It is light-weight and battery-powered, controlled by a Raspberry PI that runs a Python code that collects the down-converted samples from the SDR. In outdoor measurements a GPS module tracks the position where the samples are collected, enabling the synchronous geolocation. The system is calibrated and tested for the indoor case against a spectrum analyzer. Results are shown for both real indoor and outdoor cases.
This paper presents the design, prototyping, characterization and implementation of a dual-polarized Vivaldi antenna for a multi-technology testbed. The antenna is designed for covering a wide variety of applications including Internet of things (IoT), wideband code-division multiple-access (WCDMA), high-speed packet access (HSPA), long-term evolution (LTE), 5G New Radio (NR) and Wi-Fi from 2 to 7.5 GHz. The Dual polarization feature is ensured by properly displacing the antenna elements for ensuring the same antenna structure for both polarizations, without electromagnetic performance degradation. The antenna provides 126% bandwidth from 1.7 to 7.5 GHz and gain of approximately 7.5 dBi at 3.5 GHz. A 100-MHz bandwidth 5G NR system in the 3.5 GHz band implementation demonstrates the applicability of the proposed antenna in a real scenario, as a function of signal-to-noise ratio (SNR), constellation and root mean square error vector magnitude (EVMRMS%).
The proof of concept or PoC, which is presented in this article, is a simple and easy way to measure the extinction ratio of optical pulses using a heterodyne balanced detector and an intensity modulator. Up to 73 dB of extinction ratio measurement is demonstrated, with SNR of 10 dB. This method is recommended to be used in phase-OTDRs pulse characterization.
We presented a double-stage time domain digital pre-distortion method to mitigated the degradation imposed by narrow band filtering from analog front-end for high symbol rate coherent optical communication systems. The proposed technique is based on complex finite impulse response (FIR) filters estimated from the two stage dynamic equalizer on the reception digital signal processing stack. We conducted a series of system simulations to optimize pre-distortion setup and to evaluate its performance in increasing maximum achievable symbol rates for 16QAM and 64QAM. The results indicated gains up to 3 GBd and, consequently, 32 Gb/s and 48 Gb/s, compared with the case without digital pre-distortion, for 16QAM and 64QAM, respectively.
Some important metrics to measure the transmission quality of the signal in optical links are OSNR Ripple and Tilt. They have a relevant impact on the transmission quality of an optical signal in links with a cascade of amplifiers. This paper compares the OSNR Ripple and Tilt between the MOO and PSO adaptive control of operating point (ACOP) approaches in links with a cascade of amplifiers. The results show that both techniques have a similar performance for up to 7 amplifiers with mean values below 0.5 dB and 0.85 dB for OSNR Ripple and Tilt, respectively. In scenarios with eight amplifiers, the PSO performed worse, with mean OSNR Ripple and Tilt values exceeding 2 dB in the same scenarios.
This work presents a computationally efficient approach for the numerical analysis of the integro-differential formulation that models electromagnetic radiation by thin microstrip structures, including the contribution of lumped elements. This proposal is based on the thin-wire approximation to reduce a surface current distribution to a filamentary electric current thus, reducing a tridimensional problem to a unidimensional formulation. In addition, the effects of the dielectric are taken into account by considering the effective electric permittivity and the multipole Debye model that does this correction over the analyzed frequency band. Finally, the results obtained with this proposed technique are compared with measurements and simulation in commercial software, and an error lower than 1.5% was verified for all the analyzed cases with a processing time approximately eight times lower when compared with a full-wave simulation.
This article presents an approach to the application of a salinity sensor based on etched fiber Bragg grating inscribed in single mode fiber. A potential application for this sensor is the salinity monitoring in brine tanks in dairy where this physicochemical parameter is one of the most relevant in quality control in cheese production. Two EFBGs with the same characteristics were used, both sensitive to the variation of the refractive index for the different levels of salinity concentration and temperature measured. Tests were carried out with typical temperatures and concentrations found in brine tanks. A linear regression was used to evaluate the relationship between Baumé degrees and salt concentration, and between the Bragg wavelenght shift and salt concentration, with a non-linear relationship between the parameters being observed.
