scholarly journals An Excitation Circuit of the Cell in Optically Pumped Magnetometer

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Transmission Line ◽  
Simulation Experiment ◽  
Impedance Matching ◽  
Optically Pumped ◽  
Source Impedance ◽  
A Cell ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Highly Correlated ◽  
Excitation Circuit

Cell is the key component in an optically pumped magnetometer. It is necessary to light the cell before measurement and to maintain the illuminated state. The accuracy and stability of magnetic values from the instrument are closely related to the brightness and stability of the cell. The cell is also the largest power dissipation component in the sensor probe, so the overall energy consumption of the magnetometer is highly correlated with it. This paper studies the excitation circuit of cell in the magnetometer. Firstly, we demonstrate the resistivity characteristic of a cell using simulations. After that, based on the combination of signal source impedance and transmission line impedance, the matching network of excitation circuit is analyzed. We demonstrate that both T-network and Π-network can achieve the impedance matching of the transmitter circuit by a simulation experiment, under the condition of 50MHz signal, 10Ω source impedance, and 50Ω transmission line impedance. T-network shows the best performance in frequency selectivity and energy transfer. Finally, the simulation experiment also proves that a circuit composed of a self-coupled coil and an LC parallel resonant network can realize the impedance matching and the passband selection of the receiver circuit by optimizing values of the inductance and capacitance, and turns of the self-coupled coil simultaneously. The power consumption of the whole high-frequency excitation circuit of cell in the optically pumped magnetometer is only about 6W.

scholarly journals Bandwidth and gain enhancement of composite right left handed metamaterial transmission line planar antenna employing a non foster impedance matching circuit board

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Alibakhshikenari ◽  
Bal S. Virdee ◽  
Ayman A. Althuwayb ◽  
Leyre Azpilicueta ◽  
Naser Ojaroudi Parchin ◽  
...  
Keyword(s):  
Transmission Line ◽  
Impedance Matching ◽  
Circuit Board ◽  
Operating Frequency ◽  
Planar Antenna ◽  
Effective Technique ◽  
Input Capacitance ◽  
Gain Enhancement ◽  
Microstrip Patch ◽  
Left Handed

AbstractThe paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna’s stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ − 18 dB is greater than 1 GHz (1.4–2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band.

scholarly journals Empirical Expression for AC Magnetization Harmonics of Magnetic Nanoparticles under High-Frequency Excitation Field for Thermometry

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2506
Author(s):  
Zhongzhou Du ◽  
Dandan Wang ◽  
Yi Sun ◽  
Yuki Noguchi ◽  
Shi Bai ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
High Frequency ◽  
Planck Equation ◽  
Magnetization Dynamics ◽  
Excitation Field ◽  
Fokker Planck Equation ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Ac Magnetization ◽  
Fokker Planck

The Fokker–Planck equation accurately describes AC magnetization dynamics of magnetic nanoparticles (MNPs). However, the model for describing AC magnetization dynamics of MNPs based on Fokker-Planck equation is very complicated and the numerical calculation of Fokker-Planck function is time consuming. In the stable stage of AC magnetization response, there are differences in the harmonic phase and amplitude between the stable magnetization response of MNPs described by Langevin and Fokker–Planck equation. Therefore, we proposed an empirical model for AC magnetization harmonics to compensate the attenuation of harmonics amplitude induced by a high frequency excitation field. Simulation and experimental results show that the proposed model accurately describes the AC M–H curve. Moreover, we propose a harmonic amplitude–temperature model of a magnetic nanoparticle thermometer (MNPT) in a high-frequency excitation field. The simulation results show that the temperature error is less than 0.008 K in the temperature range 310–320 K. The proposed empirical model is expected to help improve MNPT performance.

Implementations of ACJ Technique in Different Four-Port Filter Networks

2021 ◽  
pp. 281-299
Author(s):  
Eugene A. Ogbodo
Keyword(s):  
Transmission Line ◽  
Impedance Matching ◽  
Main Challenge ◽  
The Common ◽  
Coupled Resonator

This chapter proposes the use of asynchronously coupled-resonator junctions (ACJ) in the design of a multi-input multi-output (MIMO) filtering network and a masthead combiner (MHC). By employing the resonator junctions, miniaturised circuits are achieved without using any transmission-line-based impedance matching circuits. The main challenge in the designs is the control and implementation of the external couplings at the common ports of this all-resonator-based MIMO filtering network and MHC. Both devices are four ports-based with the MIMO filtering network operating at 1.8, 2.1, and 2.6 GHz, while the MHC operates at the two channels of 1.8 and 2.1 GHz. The demonstrated designs achieved fractional bandwidths of 1.764 GHz to 1.836 GHz, 2.058 GHz to 2.142 GHz, and 2.548 GHz to 2.652 GHz, respectively. Good agreements have been achieved between the measurements of the prototype devices and the simulations.

Effect of rail pad stiffness on the wheel/rail force intensity in a railway slab track with short-wave irregularity

2019 ◽  
Vol 233 (10) ◽  
pp. 1038-1049 ◽  
Author(s):  
Amin Khajehdezfuly
Keyword(s):  
High Frequency ◽  
Critical Speed ◽  
Concrete Slab ◽  
Low Frequency ◽  
Short Wave ◽  
Vehicle Speed ◽  
Frequency Range ◽  
Slab Track ◽  
High Frequency Excitation ◽  
Frequency Excitation

In this paper, a two-dimensional numerical model is developed to investigate the effect of rail pad stiffness on the wheel/rail force in a slab track with harmonic irregularity. The model consists of a vehicle, nonlinear Hertz spring, rail, rail pad, concrete slab, resilient layer, concrete base, and subgrade. The rail is simulated using the Timoshenko beam element for considering the effects of high-frequency excitation produced by short-wave irregularity. The results obtained from the model are compared with those available in the literature and from the field to prove the validity of the model. Through a parametric study, the effect of variations in rail pad stiffness, vehicle speed, and harmonic irregularity on the wheel/rail force is investigated. For the slab track without any irregularity, the wheel/rail force is at maximum when the vehicle speed reaches the critical speed. As the rail pad stiffness increases, the critical speed increases. When the amplitude of irregularity is high, wheel jumping phenomenon may occur. In this situation, as the vehicle speed and rail pad stiffness are increased, the dynamic wheel/rail force is increased. In the low-frequency range, the wheel/rail force increases as the rail pad stiffness increases. In the high-frequency range, the wheel/rail force increases as the rail pad stiffness is decreased.

Inductance effect of passive electromagnetic dampers on building-damper system subjected to near-fault earthquakes

2019 ◽  
Vol 23 (2) ◽  
pp. 320-333
Author(s):  
Wei Guo ◽  
Xiaoli Wu ◽  
Xinna Wei ◽  
Yao Cui ◽  
Dan Bu
Keyword(s):  
High Frequency ◽  
Large Error ◽  
Client Server ◽  
Near Fault ◽  
Electromagnetic Model ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Near Fault Earthquakes ◽  
Story Building ◽  
Electromagnetic Damper

The passive electromagnetic damper was commonly simplified into the linear viscous model in numerical analysis, while this simplification may produce large error when the damper inductance is obvious. In this article, an optimal passive electromagnetic damper with good performance and economy characteristic is proposed by parameter optimization, where the damping density is set as the optimization objective. The hysteresis behavior of the passive electromagnetic damper is verified, and by neglecting the inductance effect, the passive electromagnetic damper can be simplified into the linear viscous model in some cases, but actually the inductance effect is obvious under the high-frequency excitation. Subsequently, the effect of inductance on seismic performance of building damper system under the near-fault earthquake is investigated by comparing the simplified linear viscous model and the accurate passive electromagnetic model. The passive electromagnetic damper was supplemented in a 9-story building, and the analysis of the accurate passive electromagnetic model was carried out by the co-simulation of MATLAB and OpenSees based on the client–server technology. It concludes that the inductance effect is obvious and causes large error when the building damper system is subjected to the near-fault earthquake, and the energy dissipation performance described by the linear viscous model is overestimated.

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