Shielding Box Research Articles

3D Printing of Periodic Porous Metamaterials for Tunable Electromagnetic Shielding Across Broad Frequencies

HighlightsThe stable periodic porous shielding materials were prepared by combining the strategies of 3D printing and metamaterial design.The relationship between porous material structure and electromagnetic interference shielding efficiency (EMI SE) effectiveness was deeply explored, revealing the important structural parameters for realizing tunable EMI SE property.The optimized design of the periodic porous shielding box achieves effective EMI shielding in a wide wavelength range (over 2.4 GHz).

Dual-Functional Cross-Meandering Resonator for Power Frequency Electromagnetic Shielding and Wireless Sensing Communication.

The research on MEMS wireless sensing technology adapted to strong power frequency electromagnetic field environments is of great significance to our energy security, economic society, and even national security. Here, we propose a subwavelength cross-meandering resonator (0.49λ0 × 0.49λ0) to simultaneously achieve power frequency electromagnetic field shielding and wireless communication signal transmission. The element size of the resonator is only λ0/11, which is much smaller than that of previous works. In the resonator, a resonance mode with the significant near-field enhancement effect (about 180 times that at f = 1 GHz) is supported. Based on the self-made shielding box experimental setup, the measured shielding effectiveness of the resonator sample can reach more than 33 dB. Moreover, by integrating the cross-meandering resonator with the MEMS sensor, a wireless communication signal can be successfully transmitted. A dual-function cross-meandering resonator integrated with sensors may find potential applications in many military and civilian industries associated with strong power frequency electromagnetic fields.

Design and experiment of high-performance small magnetic shielding box

Investigating the state of cells in zero magnetic or near-zero magnetic environments is an important scientific issue. However, standard cell culture incubators can only provide general conditions such as constant temperature, constant humidity, sterility, and carbon dioxide, and cannot provide zero magnetic or near-zero magnetic environments for cell culture. To address this issue, an optimization method was proposed in this paper based on the combination of the particle swarm optimization algorithm (PSO) and the finite element method (FEM), achieving the optimization design of a magnetic shielding box (MSB) with a small volume, high shielding factor, and low residual field. Firstly, the high-permeability layer and high-conductivity layer were optimized respectively using the PSO and FEM. Then, the effectiveness of this method was analyzed through experiments. The experimental results show that the shielding factors in three directions at the center point of the optimized MSB are 786.8 (east-west), 2182.7 (north-south), and 1389.4 (vertical) respectively at 0.01 Hz. Meanwhile, the maximum residual field in the cubic region with a side length of 10 cm inside the MSB is 11.9 nT. Finally, the MSB designed by this method was placed in a standard cell culture incubator to cultivate cells in a zero-magnetic or near-zero magnetic environment. Then the Cell Counting Kit-8 (CCK8) experiments to evaluate the cytotoxicity of chemotherapy drugs on tumor cells in a weak magnetic environment (WMF). The results show that the lethality of paclitaxel (PTX) to Epidermal carcinoma cell (A431) increases by 25.96 times and the lethality of gemcitabine (GE) to Lung carcinoma cell (NCI-H460) increases by 24.23 times in a WMF. At the same time, the maximum proliferation inhibition rate of 5-fluorouracil (5-FU) on NCI-H460 cells in a WMF environment increased by 15.69%. That is, WMF could significantly improve the therapeutic effect of chemotherapy drugs on tumor cells.

Development of Compact and Robust Physical System for Strontium Optical Lattice Clock

Compact and robust optical clocks are significant in scientific research and engineering. Here, we present a physical system for a strontium atomic optical clock with dimensions of 465 mm × 588 mm × 415 mm and a weight of 66.6 kg. To date, this is one of the most compact physical systems ever reported. The application of the magnetic shielding box in this physical system allowed the effect of external magnetic field fluctuation on cold atoms to be negligible. The physical system passed rigorous environmental tests and remained operational. A wavelength meter integrated in this physical system could monitor the wavelengths of the incident laser, and it could automatically calibrate the wavelengths of all lasers using a microcomputer. This compact and robust physical system could be a hardware basis for demonstrating a portable optical clock or even a space optical clock.

Large-volume CdZnTe bar detectors characterized by laser-induced transient currents

In this work, we studied the free-carrier transport properties and space-charge formation/polarization in a CdZnTe bar-shaped radiation detector using the Laser-Induced Transient Current technique. We found out that a steady-state space charge ranging from 8 × 108 to 2.1 × 109 cm−3 is formed throughout the detector at about 0.5 s following biasing. The measured current waveforms were modeled by Monte Carlo simulations after taking into account the electric and weighting fields inside the detector and shielding box. Modeling of the unpolarized waveforms revealed an exceptionally high electron mobility-lifetime product μeτe≥0.095cm2V−1. The observed formation of positive space charge in the biased detector and linear scaling of the current waveform shapes on applied bias revealed that the detector polarization is attributed to carrier injection at the anode. Measurements in pulsed and DC bias in modified electrode geometry proved the surface-charge formation.

Compact wideband filtering Balun Based on SISL Technology

AbstractA new compact wideband filtering balun based on substrate-integrated suspended line technology is presented in this brief. The proposed device is composed of a λg/4 suspended stripline open-circuited stub, a λg/2 suspended stripline resonator, and a λg/2 suspended slotline resonator. These striplines and slotline are encapsulated in an electromagnetic (EM) shielding box consisting of air cavity, surrounding substrate layers, and metal layers to achieve EM shielding performance. By properly exciting the suspended stripline and slotline resonators, three transmission poles are generated to achieve high frequency selectively. The intrinsic 180∘ phase difference between the two output ports can be obtained by using the electric field distribution caused by the perpendicular coupling between the suspension stripline and the slotline resonator. The wideband passband is achieved with magnitude balance and out-of-phase properties. To validate our proposal, a wideband filtering balun operating at 2.56 GHz with fractional bandwidth of 65.6% is designed and fabricated.

Lightweight Omnidirectional Radiation Protection for a Photon-Counting Imaging System in Space Applications

Concerns about the impact of space radiation on spacecraft and their internal instruments have prompted the need for effective protection. However, excessive protection can increase the costs and difficulty of space launches, making it crucial to achieve better shielding protection of lighter weights. In real space orbits, we observed the interference of charged particles on photon-counting imaging detectors and plan to address this issue by adding a shielding ring to the side wall of the detector input terminal. Additionally, a local protection structure was proposed for electronics, where the outer edge was increased to enable particles to reach the same thickness as the shielding box within the PCB range. This approach resulted in an omnidirectional spatial shielding thickness that was nearly identical at any point on the PCB surface. Furthermore, we used the Monte Carlo method to calculate the energy loss of electrons and protons in materials such as aluminum (Al), tantalum (Ta), and high-density polyethylene (HDPE). Through this analysis, we determined the optimal mass ratio of Al, Ta, and HDPE to achieve the lowest ionization doses at an object’s location in the particle environment of the FY-3 satellite orbit. This protection strategy provides a useful design concept for photoelectric detection instruments with high sensitivity.

Compact front module with integrated miniaturised antenna in package for parabolic reflector antenna in satellite ground terminals

A compact front module with integrated miniaturised antenna in package for parabolic reflector antenna is presented for GEO-KOMPSAT-2A (GK-2A) satellite ground terminal application at 1692 MHz. The active feeder antenna module consists of four parts: a pair of miniaturised slot antennas, a pair of differential feeding lines, a metal shielding box, and front circuits, including a low noise amplifier (LNA) and a surface acoustic wave bandpass filter (SAW BPF). To reduce the lateral size of the feeder antennas and obtain required radiation patterns, meandered radiation slots are suggested and fed by a pair of differential coplanar waveguide (CPW) lines. The antenna substrate serves as the module cover and the electromagnetic shielding with a lateral size of 48 × 48 mm2 (0.27 × 0.27 λ 2 ${\lambda }^{2}$ ). Additionally, the feeder antenna module is proven to work with the specified parabolic reflector, both in theory and simulation. The front module with the packaged antenna is fabricated, and the measured output gain exceeds 20 dBi within a desired narrow band. Moreover, the module also achieves excellent performance in the GK-2A satellite signal-receiving experiment when used to feed the parabolic reflector antenna. The entire front module exhibits good package integration and application performance.

Approximate Simulation of Low Frequency Magnetic Shielding of a Rectangular Shielding Box with All Walls Perforated Periodical Holes

Approximate Simulation of Low Frequency Magnetic Shielding of a Rectangular Shielding Box with All Walls Perforated Periodical Holes

Simulation analysis of electromagnetic pulse susceptibility and hardening design for system-in-package SZ0501

The electromagnetic pulse (EMP) susceptibility of System-in-Package (SiP) SZ0501 was investigated by field-circuit combination simulation method in this paper. The electromagnetic pulse coupling model of the SiP is established by an electromagnetic field simulation software (CST). Considering different incident and electric field direction, the type and distribution of pins, the coupled voltages via pins of the SiP under EMP were obtained to analyze the electromagnetic susceptibility of the SiP. Simulation results indicate five major factors affecting the electromagnetic susceptibility of the SiP: the effective electric field integration on the pins, the distribution of pins, the terminal cases of pins, the shunt effect of the output ports of the power plane, and the kind of ground planes. And compared with side incidence, SiP is more sensitive to EMP from above. Finally, some factors affecting the shielding effect are considered, a shielding box is designed and then verified to reduce the electromagnetic susceptibility.

Optimization of the Ring Imaging Cherenkov Photodetector Shielding Box for Compressed Baryonic Matter Experiment

Optimization of the Ring Imaging Cherenkov Photodetector Shielding Box for Compressed Baryonic Matter Experiment

Source Reconstruction of Electronic Circuits in Shielding Enclosures Based on Numerical Green’s Function and Application in Electromagnetic Interference Estimation

In this work, to characterize the radiated emission from electronic circuits in shielding enclosure, an improved electric dipole-based source reconstruction method (SRM) is developed. Moreover, by resorting to this reconstructed equivalent source, the estimation of electromagnetic interference (EMI) between different circuit modules in the enclosure can be conveniently and accurately evaluated. Different from the free-space SRM, the equivalent dipoles of the proposed SRM are directly placed over the shielding box enclosed circuit board, and the numerical Green’s function (NGF) is developed to bridge the connection between the equivalent dipoles and the planar scanned magnetic near-field. With the NGF strategy, the effects of surrounding environments (including the presence of substrate, ground plane, and shielding enclosure) are inclusively considered, which makes the proposed SRM valid for any complex EM environments in theory. Since the proposed SRM also has the capability of reproducing the radiated emission inside the shielding enclosure, it is critically helpful to evaluate the EMI between different circuit modules inside the shielding enclosure. To reach this aim, the Rayleigh-Carson Reciprocity theorem is referred, in which the original EM coupling problem is decomposed into the “forward problem” and “reverse problem.” A Huygens box enclosing the victim circuit module is built and the EM fields on the box are obtained using the reconstructed dipoles in both problems. Then the EMI can be calculated accordingly. Therefore, the novelty and merits of the proposed approach are threefold: 1) the physically-based equivalent dipole model considers the interactions between the radiation sources and the surrounding objects, leading to the accurate prediction of radiated emissions both outside and inside the enclosure; 2) due to the utilization of the NGF, there is no approximation involved in the solution of the dipole’s radiation, thus improving the calculation precision; and 3) the near-field coupling between multiple electronic circuit modules inside the shielding enclosure can be identified precisely, which is useful for diagnostics of radiation sources. The effectiveness of this algorithm is verified by representative numerical examples.

Axial scalable add-on PET/MRI prototype based on four-layer DOI detectors integrated with a RF coil

We developed an add-on PET which was a PET insert based on 4-layered depth-of-interaction (DOI) detectors integrated with a birdcage RF-coil. The PET detectors were placed close to subjects to achieve high sensitivity. The DOI capability suppress degradation of spatial resolution at the edge of the field of view (FOV). Previously, we developed an first prototype which had a short axial FOV. In order to extend the axial FOV, we developed new scalable add-on PET prototype. The constructed RF-coil of the new prototype was combined with 24 DOI-PET detector units Each detector unit with two PET detectors was shielded with a carbon fiber shielding box. Each PET detector consisted of a 14 × 14 × 4-layer array of lutetium fine silicate crystals (1.9 mm × 1.9 mm × 4.0 mm), an 8 × 8 multi-pixel photon counter (MPPC, S12641PA-050) array and a readout circuit board with an ASIC. The RF coil was tuned for a 3T clinical MRI (MAGNETOM Verio, Siemens). We evaluated performance the scalable add-on PET prototype in simultaneous PET/MRI measurements. We obtained spatial resolutions of 2.0 mm at the center of the FOV and better than 3.3 mm in the whole FOV. The energy resolution of 12.4 % was obtained at 511 keV. In addition, we observed no degradation of PET performance caused by the MRI measurement. The signal-to-noise ratio (SNR) of the MRI image was 186.2 in simultaneous measurements with the PET. The maximum ΔB0 and maximum difference of the secondary magnetic field due to the eddy current effect were smaller than 0.2 ppm and ±1.0μT, respectively. It meant that the influence of the PET detectors on the static magnetic field and secondary magnetic field did not cause problems.

磁気シールド材料の内部磁界を考慮したボックスシールドの性能推定法とその精度検証

磁気シールド材料の内部磁界を考慮したボックスシールドの性能推定法とその精度検証

Numerical Green’s Function-Based Method for Modeling Radiated Emission From PCBs in Shielding Enclosures

Due to stringent electromagnetic compatibility (EMC) regulations, all electronic devices need to go through rigorous radiated emission tests before launching to market. Thus, efficient, accurate, and cheap characterization approaches are quite of interest. Instead of utilizing the time-consuming and expensive direct far-field measurement, in this work, a novel methodology on the basis of numerical Green’s function (NGF) is proposed to acquire the parasitic EM emissions from PCBs placed in a shielding enclosure with ventilation slots. Referring to Schelkunoff’s equivalence principle, the whole modeling procedure can be decomposed into two steps in order to obtain the emissions in the entire space. For the first step, the tangential electric fields over the surface of ventilation slots are sampled first; then, the NGF over a spherical surface tightly enclosing the perfectly electric conductor (PEC) filled shielding box is numerically evaluated; finally, the tangential component of the magnetic field over the spherical surface enclosing the shielding box is calculated in terms of the NGF and the sampled near electric field. As for the second step, by filling the sphere with a perfectly magnetic conductor (PMC) first, the pertinent Green’s function is further expanded by the spherical modal functions; later, the radiated emission outside this sphere can be analytically evaluated in terms of the previously obtained tangential magnetic field and the modal function expanded Green’s function. Therefore, the novelty of the proposed method has two folds: 1) only the tangential electric field over the ventilation slots is required, thus saving a lot of time in near-field measurement and 2) the NGF is independent of the PCBs in the shielding enclosure and, thus, only needs to be calculated once even though the PCBs inside the shielding enclosure is changed. To validate and verify the effectiveness of this proposed modality, several representative examples are presented.

Metamaterial Absorbers for Lining System Shield Box and Packaging: Cavity Analysis and Equivalent Material Design

Metamaterial absorbers have been introduced as custom-designed solutions for mitigating radiated emissions from a system shield box. In this article, the analysis of these system enclosures is generalized by using a cavity analysis approach. Inspecting surface current, frequency, and quality factor of the resonant cavity modes of a shield box with metamaterial lining provides insight into evaluating and quantifying the efficacy of an absorber solution. The increased radiated emission from an enclosed system is traced back to the potential excitation of resonant cavity modes. The cavity modes can be excited when common mode signals are present at proper locations. In a generic high-speed differential signaling system, common mode signals are shown to be created as a result of differential line phase mismatches and demonstrated to yield strong spectral components at twice the harmonics of Nyquist frequency. A second design approach is introduced herein that involves finding the equivalent complex permittivity and permeability, i.e., an equivalent bulk material characteristic for the metamaterial absorber. This approach expedites the design of metamaterial absorbers and evaluation of their effectiveness for emission reduction from few hours to few minutes.

Magnetic triggering — time-resolved characterisation of silicon strip modules in the presence of switching DC-DC converters

Modules for the ATLAS Inner Tracker (ITk) strip tracker include a DC-DC converter circuit glued directly to the silicon sensor which converts the 11 V supplied to the module to the 1.5 V required for the operation of the readout chips. The DC-DC converter unit, consisting of a copper solenoid and custom ASIC, is located directly above the silicon strip sensor and therefore needs to be shielded to protect the sensor from EMI noise created during the operation of the circuit. Despite dedicated shielding, consisting of an aluminium shield box with continuous solder seams encompassing the surface components and a copper layer in the PCB beneath it, module channels connected to sensor strips located beneath the converter circuit were found to show a noise increase. While the DC-DC converter unit causing the underlying EMI noise operates at a frequency of 2 MHz, module characterisation measurements for ITk strip tracker modules are typically performed asynchronously to the DC-DC switching and are therefore averaged over the full range of time bins with respect to the converter frequency. In order to investigate the time dependence of the noise injection relative to the DC-DC switching frequency, a dedicated setup to understand the time-resolved performance change in modules was developed. By using a magnetic field probe to measure the field leaking through the shield box and triggering on its rising edge, data taking could be synchronised with the DC-DC switching. This paper illustrates the concept and setup of such time-resolved performance measurements using magnetic triggering and presents results for the observed effects on signal and noise for ATLAS ITk strip modules from both laboratory and beam tests.

Coupling Characteristics of Electromagnetic Disturbance of On-Site Electronic Device Power Port in Substations and Its Suppression

The switching operations of circuit breakers and disconnectors in substations can generate very fast transients, including transient earth voltage rise and intense electromagnetic radiation, causing severe disturbance of on-site electronic devices in substations and seriously affecting the development of smart power equipment. The power supply of an on-site electronic device provides a path along which the disturbance couples with the device. In this article, we investigated the coupling mechanism and measures to suppress this disturbance. We found that, for most on-site electronic devices, their power supply includes a power line that connects the exterior and interior of the shielding box, greatly reducing the shielding effectiveness and inducing disturbance from the outside to the inside. This article proposes a shielding–crossing isolation transformer as the power supply of which the primary winding is outside and the secondary winding is inside of the shielding box, without a power line across the shielding box. This arrangement proved to deliver the high performance in terms of eliminating disturbance from the power supply. This article provides an understanding of the mechanism according to which the electromagnetic disturbance couples through the power supply. A method to determine the electromagnetic compatibility of on-site electronic devices in a substation is also proposed.

Study on shielded Rogowski coil with return line for measurement of nanosecond-range current pulse

In this paper, a shielded Rogowski coil aslo with a return line for measurement of the nanosecond-range current pulse is studied. It is found that the connection mode of the end lead has effect on the output pulse waveform of the coil. When the free end of the coil is connected to the ground earth, the output waveform is distorted unless the sampling resistor matches the parasitic transmission line (PTL) formed by the return line and the shielding box. Besides, a prepulse caused by capacitive voltage dividing occurs on the output waveform. However, problems above solved by connecting the free end of the return line to the ground earth. A coil of this kind is developed. It has a turn number over 3000, with a return line of 4-mm diameter. Calibration result of the coil shows that this coil has a flattop jitter of 3% for measurement of the rectangular pulse with a rise time less than 6 ns when its end lead is properly connected. The developed coil is utilized for measurement of the discharge current pulse of a high-voltage pulse generator. Experimental result shows that the coil has good response for the heavy-current pulse with a rise time as fast as 4 ns.

Electromagnetic Shielding Box Design of Radial X-Ray Camera Electronics

In order to ensure the electronics of radial X-ray camera (RXC) system can work normally under the complicated electromagnetic environment of Tokamak system, simulation and analysis of the static magnetic distribution is done in this paper. The electromagnetic shielding box is designed and shielding effort was validated through simulation with software Maxwell. The shielding box designed can reduce the static magnetic flux density from 230 mT to less than 5 mT, meeting the requirements of anti-electromagnetic interference ability of electronics.