Reasonable Power Levels Research Articles

Thermo-Mechanical Analysis of MYRRHA Fuel Pins Irradiated in the TRIGA Annular Core Pulse Reactor of ICN Pitesti

MYRRHA represents an innovative and unique facility designed to demonstrate the feasibility of the ADS concept at reasonable power levels and to pave the way towards the next generation of nuclear reactors. At the same time, this versatile infrastructure aims to support the ALFRED reactor. In the framework of investigating MYRRHA fuel pin thermo-mechanical behavior during transient conditions, the TRANSURANUS fuel performance code along with ANSYS, were used for thermo-mechanical simulations on three experimental fuel pins containing UO2 pellets and 15-15Ti clad, surrounded by stagnant LBE coolant, irradiated in the ACPR-TRIGA reactor at ICN Pitesti. The results concern both fuel and cladding performance and are compared with the available experimental data.

A Broadband Multistage Self-Interference Canceller for Full-Duplex MIMO Radios

Full-duplex (FD) antenna arrays are desirable for expanding the channel capacity of wireless systems up to 2, which is particularly important in the crowded sub-6-GHz spectral bands. Conventional FD solutions based on circulators do not scale to antenna arrays due to the presence of significant mutual coupling between antenna elements. This article describes a two-stage self-interference cancellation (SIC) method that is suitable for FD arrays. The first-stage SIC uses a replica-antenna (RA)-based network that is passive and linear and can thus be placed before the low-noise amplifier (LNA) without significantly degrading receiver noise figure (NF) and linearity. The RA-based SIC also simplifies the hardware requirements for the second-stage SIC, which uses an analog tapped delay line (ATDL) network. The proposed two-stage SIC was realized using off-the-shelf components and tested in the 1–3-GHz range using strongly coupled pairs of ultrawideband antennas. Network analyzer measurements show 20–30 dB of SIC using the RA network over the entire frequency range and >20 dB of SIC using a single-stage ATDL SIC over instantaneous bandwidths of 0.53–0.65 GHz. The combined transmit (Tx)–receive isolation is 66.5, 73.5, and 85.8 dB around the center frequencies of 1, 2, and 3 GHz, respectively. The amount of isolation is shown to be sufficient for realizing practical FD wireless links at 2 GHz with reasonable Tx power levels (0 dBm).

A novel tunable gain CMOS buffer amplifier for large resistive loads

An all-OTA analog buffer amplifier configuration capable of driving large resistive loads is presented. The proposed configuration features high input swing, gain tunability, wide-bandwidth, and low design complexity. The concept is validated with simulation results in Cadence Virtuoso using SCL 0.18-μm technology parameters. Using a ±0.9 V power supply, the buffer with a gain of 1, can drive a 1 Vp−p sinusoid into a 50 Ω load with a THD of better than 0.015%, with a 3-dB bandwidth of 1.55 GHz and consumes 9 mW. The proposed configuration is demonstrated with gain values varying from 0.25 V/V to 5 V/V and with different load values 16 Ω to 5.6 kΩ. The voltage gain is tunable over more than a decade with reasonable power levels. With low-gain OTA, the proposed buffer configuration works well without any complex frequency compensation circuit that makes the all-OTA analog buffer amplifier configuration simple compared to the existing buffer amplifiers.

A Case for Digital Beamforming at mmWave

Due to the heavy reliance of millimeter-wave (mmWave) wireless systems on directional links, beamforming (BF) with high-dimensional arrays is essential for cellular systems in these frequencies. Thus, performing the array processing in a power-efficient manner is a fundamental challenge. Analog and hybrid BF require few analog-to-digital and digital-to-analog converters (ADCs and DACs), but can only communicate in a small number of directions at a time, limiting directional search, spatial multiplexing, and control signaling. Digital BF enables flexible spatial processing but must be operated at a low quantization resolution to stay within reasonable power levels. This decrease in quantizer resolution distorts the received as well as the transmitted signal. To assess the effect of coarse quantization at the receiver, this paper presents a system level analytic framework based on a simple additive quantization noise model (AQNM). The analysis verified through extensive simulations reveals that at moderate resolutions (3-4 bits per ADC), there is negligible loss in downlink cellular capacity from quantization. In essence, the low resolution ADCs limit the high SNR, where cellular systems typically do not operate. For the transmitter, it is shown that DACs with 4 or more bits of resolution can support high order modulations, and do not violate the adjacent carrier leakage limit set by 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> Generation Partnership Project (3GPP) New Radio (NR) standards for cellular operations. In fact, our findings suggest that low resolution digital BF architectures can be a power-efficient alternative to analog or hybrid BF for both transmitters and receivers at millimeter-wave.

Polarization noise places severe constraints on coherence of all-normal dispersion femtosecond supercontinuum generation

Supercontinuum (SC) generated with all-normal dispersion (ANDi) fibers has been of special interest in recent years due to its potentially superior coherence properties when compared to anomalous dispersion-pumped SC. However, care must be taken in the design of such sources since too long pump pulses and fiber length has been demonstrated to degrade the coherence. To assess the noise performance of ANDi fiber SC generation numerically, a scalar single-polarization model has so far been used, thereby excluding important sources of noise, such as polarization modulational instability (PMI). In this work we numerically study the influence of pump power, pulse length and fiber length on coherence and relative intensity noise (RIN), taking into account both polarization components in a standard ANDi fiber for SC generation pumped at 1064 nm. We demonstrate that the PMI introduces a power dependence not found in a scalar model, which means that even with short ~120 fs pump pulses the coherence of ANDi SC can be degraded at reasonable power levels above ~40 kW. We further demonstrate how the PMI significantly decreases the pump pulse length and fiber length at which the coherence of the ANDi SC is degraded. The numerical predictions are confirmed by RIN measurements of fs-pumped ANDi fiber SC.

Low‐complexity amplify‐and‐forward relaying protocol for non‐coherent chaos‐based communication system

This study proposes a low-complexity amplify-and-forward (AF) relaying scheme for a differential chaos shift keying (DCSK) system. In this scenario, like the conventional AF-DCSK scheme, a source node communicates with a destination node via one relay node, in a way that the source transmits the reference and the data carrier signal to the destination and the selected relay. This approach being sub-optimal, presents a new relaying algorithm for the AF-DCSK scheme to minimise the processing load, the cooperative time and the energy for relaying symbols. Furthermore, it is analytically proven that the new AF scheme benefits from less relaying complexity, and while preserving reasonable power levels, it does not degrade the error performance of the system. Finally, the scheme is evaluated by comparing the transmitted energy, the cooperative time and the error performance gain to the corresponding values in the conventional AF-DCSK scheme.

Quantum-correlated photon pair generation in chalcogenide As_2S_3 waveguides

We theoretically investigate the generation of quantum-correlated photon pairs through spontaneous four-wave mixing in chalcogenide As(2)S(3) waveguides. For reasonable pump power levels, we show that such photonic-chip-based photon-pair sources can exhibit high brightness (approximately 1 x 10(9) pairs/s) and high correlation (approximately 100) if the waveguide length is chosen properly or the waveguide dispersion is engineered. Such a high correlation is possible in the presence of Raman scattering because the Raman profile exhibits a low gain window at a Stokes shift of 7.4 THz, though it is constrained due to multi-pair generation. As the proposed scheme is based on photonic chip technologies, it has the potential to become an integrated platform for the implementation of on-chip quantum technologies.

Two-Terminal Active Devices for Terahertz Sources

The terahertz frequency range of the electromagnetic spectrum holds great promise for many applications including sensing, imaging, and communications. However, the availability of solid-state sources with reasonable power levels is well recognized as one of the major obstacles for systems applications in this frequency range. Here, the state of the art of active two-terminal devices is reviewed and high-lighted with some exemplary experimental results. The potential, capabilities, and limitations of two-terminal devices regarding power generation at terahertz frequencies are discussed. Furthermore, a new device is described that has the potential of circumventing some of the limitations of existing devices.

Progress toward 100 GHz Logic in InP HBT IC Technology

Future wideband communications, mm-wave digital synthesis, and digital beam-steering will benefit from digital operation at clock frequencies between 50 and 100 GHz at reasonable power levels. HRL has developed InP-based HBT technology that is capable of supporting these needs. We have demonstrated InP HBTs with cutoff frequencies, ft, over 200 GHz and with f max over 300 GHz as well as fully static dividers operating at 72.8 GHz.

Femtosecond pulse propagation in optical fibers: higher order effects

Higher-order effects in femtosecond-pulse propagation in optical fibers are examined. In particular, the specific contributions to nonlinear chirping in the fiber by the higher-order cubic dispersion term and by the shock term are investigated. The effects on the output spectrum of fiber input pulses having an initial chirp and an initial asymmetric pulse shape are also investigated. By comparison to a global description, it is shown that, for optical pulses having reasonable power levels, dispersion effects can be accurately approximated by a Taylor series expansion in the nonlinear Schrodinger equation even for pulses containing two optical cycles. >

The electrically small magnetically loaded multiturn loop antenna

An analytical model of a class of electrically small multiturn loop antennas has been formulated and compared with experimental measurements over a frequency range of 3 to 86 MHz. Both air core and magnetically loaded eases were examined. Transmitted signal enhancement as high as 10 dB was predicted and observed by magnetic loading. Several interesting properties of the transmitting antenna were investigated experimentally and by analysis based upon the model. It is concluded that transmitted signals can be enhanced in the 2-30 MHz range, at reasonable power levels, as much as 10 dB with state-of-art ferrite materials. Secondly, the analytical model described in this paper should prove an effective design aid for a volumetrically constrained antenna of the class.

Operation of Magnetic Film Parametrons in the 100- to 500-Mc Regions

An analysis of the behavior of thin magnetic films of Permalloy when used as time variable inductors has been made in terms of a modified Landau-Lifshitz equation. These results show that parametrons using time variable magnetic film inductors can be made to operate at reasonable power levels with large grains per cycle at oscillating frequencies in the 100- to 500-Mc region. A way of fabricating magnetic film parametrons with strip line techniques is shown. Calculations indicate that units with dissipations in the 10 mw range are feasible with existing techniques for operation in the 100- to 500-Mc region. Ways of advantageously using capacitive coupling between parametron units is indicated in which the two new subharmonic states of a magnetic film parametron created by a bias reversel are used.