Shielding Enclosure Research Articles

A Source Reconstruction Method for Unknown EMI Sources Inside a Shielding Enclosure Based on Magnitude-Only Near-Field Scanning

A Source Reconstruction Method for Unknown EMI Sources Inside a Shielding Enclosure Based on Magnitude-Only Near-Field Scanning

Development of the EM Field in a Shielding Enclosure with Aperture after Interference Caused by a Subnanosecond High-Power Parallelly Polarized EM Plane Wave Pulse

Due to the increase in the threat of attacks with high-power electromagnetic (EM) pulses, there is great interest in metallic enclosures with high shielding effectiveness (SE). Necessary technological apertures in these enclosures reduce their effectiveness. Understanding the penetration and internal propagation of the high-power EM pulses into an apertured enclosure is fundamental to assessing the EM SE of the enclosure. In the present paper, results of the numerical simulations of development of the EM field in a shielding enclosure with aperture after the interference of a subnanosecond high-power EM plane wave pulse of the parallel polarization (having the duration of 0.3558 ns and the amplitudes of the electric and magnetic fields of 106 V/m and 2.6 × 103 A/m, respectively) are presented. The results obtained include 3D and 2D images , vector maps of the EM field developed inside the enclosure, and time-varying distributions of the electric charges formed on the inner walls of the enclosure. They revealed the mechanism of formation of the EM field inside the enclosure caused by the subnanosecond high-power parallelly polarized EM pulse. The EM field formed in the enclosure with aperture has the form of the electric and magnetic field interference structures. They are a superposition of the incident EM pulse field, which entered the enclosure through the aperture in the way described by the geometrical (ray) optics, the electric field generated by the electric charges formed on the aperture edges and inner sides of the walls of the enclosure, and the magnetic field generated by the surface current formed on the aperture edges and on the inner walls of the enclosure. The amplitudes of the electric and magnetic fields of the strongest EM interference structures decrease non-monotonically to about 0.7 × 105 V/m and 200 A/m at t = 5 ns. We found that the points in the enclosure are subjected to the disturbance of a long series of subnanosecond EM pulses, which we have called internal EM pulses. The amplitudes of these internal pulses are lower than those of the incident EM pulse. Nevertheless, they can pose a severe EM hazard inside the enclosure due to their large number (about 900 internal pulses in 30 ns). This means a fundamental change in the character of the EM disturbance caused by the subnanosecond pulse when the enclosure with aperture is used as a shield.

Temporal and Spatial Development of the EM Field in a Shielding Enclosure with Aperture after Transient Interference Caused by a Subnanosecond High-Energy EM Plane Wave Pulse

A proper assessment of the shielding effectiveness of an enclosure with aperture under subnanosecond transient interference requires a better understanding of the coupling and development mechanisms of the EM field induced inside the enclosure. In this paper, the results of a numerical study of the temporal and spatial development of the electromagnetic (EM) field in a shielding enclosure with aperture after transient interference caused by a subnanosecond high-energy EM plane wave pulse are presented. The interference pulse had Gaussian distribution of the electric and magnetic fields with amplitudes of 106 V/m and 2.68·103 A/m, respectively. The maximum pulse power density was 2.68 GW/m2. The novelty of this study was 2D and 3D images, which visualized the temporal and spatial build-up of electric and magnetic fields in the shielding enclosure within 90 ns after the transient interference. This is 58 times longer than the time needed by any EM wave to travel the distance between the front and rear walls of the enclosure. The presented images, showing the EM field morphology over a relatively long period of time, were crucial for understanding the EM field build-up process inside the shielding enclosure with aperture. They revealed the existence of two unknown phases of the EM field build-up in the enclosure with aperture. We call these two phases the wave phase and the interference phase. In the wave phase, the EM field is generated in the form of so-called primary and secondary wave pulses, traveling towards the enclosure rear wall. In the interference phase, the EM field has the form of temporally and spatially varying pulse-like interference (size-limited) patterns of the associated electric and magnetic fields. The EM field induced in the enclosure is long-lasting compared to the interference pulse duration. The amplitudes of the electric and magnetic fields decreased about threefold in 5 ns and 30-fold in 90 ns, thus exhibiting a severe EM hazard for much longer than the external interference duration. For a long period of time, the highest EM field amplitudes would change their locations in the enclosure, which makes it difficult to assess the shielding effectiveness on the basis of classical definitions. The existence of the long-lasting temporally and spatially varying EM field induced in the enclosure with aperture by the subnanosecond transient interference, visualized in detail in this paper, confirms that a new definition and measurement methods of shielding effectiveness under transient conditions are needed. The obtained results provide a source of data that can be useful when working on the introduction of time-domain parameters to evaluate the transient shielding effectiveness in the case of the ultrashort EM interference.

Substrate Integrated Suspended Slot Line and Its Application to Differential Coupler

This article proposes a novel substrate integrated suspended slot line (SISSL) platform, which embeds the slot line inside a metallic shielding enclosure to minimize the radiation loss and solve packaging problems. The propagation characteristics of SISSL including characteristic impedance and guided wavelength are investigated. By using the transition from SISSL to shielded microstrip, a type of differential branch-line-type coupler is proposed, and good common-mode suppression is achieved over a wide frequency band. In the meantime, the SISSL coupler features filtering response in the differential mode when the impedance values of the slot line are selected properly. The proposed SISSL circuit is implemented by using printed circuit board (PCB) process, and it is self-packaged. Two design cases are fabricated and measured to demonstrate the feasibility.

Dielectric antenna effects in integrating line piezoelectric sensors for optoacoustic imaging

This work studies the adverse effects, as regards noise, of immersing in water an integrating line piezoelectric detector devoted to optoacoustic imaging. We found that the sensor, in conjunction with the acoustic coupling medium (water), behaves as a resonant dielectric antenna. This phenomenon limits the performance of the system because it efficiently captures unwanted electromagnetic signals. The requirement of good acoustic coupling between the water and the sensor precluded the use of a standard metallic shielding enclosure. Therefore, we resorted to a silver-paint-based electrical shield deposited on the detector. This easy-to-implement and low-cost solution significantly increases the signal to noise ratio and does not degrade the acoustic performance. The noise reduction allows the use of a better transimpedance amplifier with higher gain and bandwidth; thus achieving a very sensitive, low-noise detection system.

Investigation of Parameters Affecting the Level of Perforated Conductive Enclosure Protection Against HEMP Radiation Using FDDM

One of the best methods to protect electronic circuits against high-altitude electromagnetic pulse (HEMP) is using a metallic shield enclosure, which usually has apertures and slots for venting and passing power and data cables. In this article, we investigate the effect of the rise time of HEMP-like pulses on time-domain shielding effectiveness (TD-SE). The rise time of the electromagnetic pulse is one of the essential characteristics that depend on the mechanism of pulse production in pulse generators. Since the dimensions and location of aperture, the wall thickness of enclosure, and the enclosure dimension are important factors in coupling the electromagnetic pulse with circuits inside the enclosure shield, the effect of these factors on TD-SE will be checked. Finite difference delay modeling (FDDM) is used as a new method in the computation of transient field in perforated metallic enclosure and SE. Results of FDDM is verified by comparing with finite integration technique (FIT) method results (CST-Microwave Studio).

3 Magnetocardiography Using a Novel Analysis System (Cardioflux) in the Evaluation of Emergency Department Observation Unit Chest Pain Patients

Magnetocardiography (MCG), a non-invasive diagnostic modality that measures the magnetic field arising from the electrical activity of the heart cycle, has been found to be superior to ECG in detection of myocardial ischemia in patients with acute chest pain. The objective of this pilot study is to evaluate MCG using Cardioflux (MCG-CF), a novel MCG analysis system, in the workup of ED observation unit (EDOU) chest pain patients by comparing MCG-CF with stress testing (ST) and/or coronary angiography (CA) to identify myocardial ischemia. This is a prospective pilot study of ED chest pain patients of low-intermediate risk placed in an EDOU between August 2017 and February 2018 evaluated with a resting 90-second MCG-CF in addition to ST and/or CA. The MCG hardware unit is comprised of patient table, sensor plate positioned over the chest, and magnetic shield enclosure. Exclusion criteria include metal in chest area, inability to fit into the unit or complete the scan. A negative MCG-CF is defined as findings correlating to < 50% stenosis and a positive MCG-CF as 50% - 69% and ≥ 70% stenosis. CA is the gold standard if both ST and CA are performed. Assessment of further diagnostic testing with ST or CA and major adverse cardiac events (MACE) at 30 days after discharge performed via phone as well as hospital electronic medical records. Of 125 consented patients, 101 underwent MCG-CF and 24 were excluded. Mean age was 56 years, 53.6% were male and 56.5% African American. Of 78 patients with negative MCG-CF, 72 have corresponding negative ST (66) or CA (6), and 6 had positive ST (1) or CA (5). Of 23 patients with a positive MCG-CF, 3 had a corresponding positive CA, and 20 had a negative ST (16) or CA (4). Only 9 patients in the entire cohort were positive for ischemia: ST (1), CA (8). Using ST or CA as the gold standard, the sensitivity with 95% CI for MCG-CF is 33.3% [7.5%, 70.7%], specificity 79.4% [68.4%, 86.2%], PPV 13% [5.2%, 29.0%] and NPV 92.3% [88.2%, 95.1%] for ≥50% stenosis and 28.6% [3.7%, 71.0%], 87.1% [78.6%, 93.2%], 14.3% [4.4%, 37.6%] and 94.2% [91.0%, 96.3%] respectively for ≥70% stenosis. Additionally, 30-day follow-up was completed via review of electronic medical records (covers 3 local hospitals), no patients had ST, CA or MACE post discharge. Phone follow-up was attempted for adverse events however only 25.7% were successfully contacted. This pilot study of a novel diagnostic test shows a resting 90-second MCG-CF has excellent specificity and NPV especially in patients with critical stenosis. No patients had further cardiac testing or MACE 30-days post discharge. A larger study to better assess accuracy in ruling out significant stenosis/ischemia is needed. Also, given the low prevalence of disease in this study cohort, a larger study that also includes high-risk chest pain patients is needed to better assess the accuracy of MCG-CF in detecting cardiac ischemia and could assess whether MCG-CF is superior to ST and would therefore be a faster non-invasive diagnostic modality in the evaluation of ED patients with chest pain.

Toward noninvasive monitoring of ongoing electrical activity of human uterus and fetal heart and brain

ObjectiveTo evaluate whether a full-coverage fetal-maternal scanner can noninvasively monitor ongoing electrophysiological activity of maternal and fetal organs. MethodsA simulation study was carried out for a scanner with an array of magnetic field sensors placed all around the torso from the chest to the hip within a horizontal magnetic shielding enclosure. The magnetic fields from internal organs and an external noise source were computed for a pregnant woman with a 35-week old fetus. Signal processing methods were used to reject the external and internal interferences, to visualize uterine activity, and to detect activity of fetal heart and brain. ResultsExternal interference was reduced by a factor of 1000, sufficient for detecting signals from internal organs when combined with passive and active shielding. The scanner rejects internal interferences better than partial-coverage arrays. It can be used to estimate currents around the uterus. It clearly detects spontaneous activity from the fetal heart and brain without averaging and weaker evoked brain activity at all fetal head positions after averaging. ConclusionThe simulated device will be able to monitor the ongoing activity of the fetal and maternal organs. SignificanceThis type of scanner may become a novel tool in fetal medicine.

A Hybrid Method for Calculating the Coupling to PCB Inside a Nested Shielding Enclosure Based on Electromagnetic Topology

Conventional analytical and numerical approaches are inefficient for the analysis of electromagnetic (EM) coupling effect on a printed circuit board (PCB) in complicated electric systems. This paper develops a hybrid method based on the combination of electromagnetic topology and analytical method or full-wave simulation. A coupling mechanism of PCB in a nested shielding enclosure is established, and the EM interactions from exterior fields to interior PCB are determined by the way of conductive and radiation coupling interference. The total load disturbance voltage of PCB trace is obtained by solving the BLT equation of the two interference paths. In this paper, the full-wave simulation method is adopted to calculate the electric field and numerical integration method is applied to solve the BLT equation. The results of the proposed method are in good agreement with the result of a commercial full-wave tool, which confirms its validity. Compared to numerical simulation, the proposed method simplifies the modeling process significantly and possesses better efficiency.

Transparent electromagnetic shielding enclosure with CVD graphene

Cavity resonant modes of shielding enclosure for housing electronic circuits may cause electromagnetic interference (EMI). Here, we present an effective approach by using graphene to suppress unwanted resonant modes while maintaining good transparency to visible light. The structure consists of graphene sheet on quartz substrate attached to the shielding enclosure made from indium tin oxide. We experimentally demonstrate that the proposed approach can lead to good absorption of microwave waves at a wide frequency range from 5 to 12 GHz and high attenuation of cavity modes up to 20–30 dB. Its effectiveness of EMI shielding averaged 20 dB is proven to be comparable with conventional metallic enclosures.

Characteristics of Electromagnetic Coupling with A Wire through Shielding Enclosure

The paper presents a numerical method based on Finite Difference Time Domain (FDTD) in both frequency and time domain for modeling the coupling of an incident electromagnetic pulse(EMP) with a conducting wire through a metallic shielding enclosure with a small aperture. Simulation and analysis are done by radius, length, and number of the wires, the incidence angle of EMP and the polaration angle of electric field in consideration. The simulation result shows that interference of the electromagnetic coupling into the shielding enclosure can be affected in different degrees by above factors. At low frequency, the larger the leakage length, the radius or the number of the wire penetrated into the cavity, the more interference is coupled into the shielding cavity from electromagnetic field. Also, the smaller the incident direction angle of propagation of the electromagnetic pulse or the polarization direction angle of the incident electric field, the more easily the electromagnetic interference is coupled into the cavity. DOI : http://dx.doi.org/10.11591/telkomnika.v12i2.3984

Shield can mounting clip design for robust and enhanced shielding effectiveness in mobile devices

A small metallic shield enclosure, commonly called a shield can, is an indispensable component of modern mobile devices in reducing electromagnetic interference. A sophisticated clip design utilising an embossing technique and a furrow structure for mounting shield cans on printed circuit boards in mobile devices is proposed in order to enhance the robustness and effectiveness of the shield cans. The proposed design is validated by radiated spurious emission measurement and three-dimensional field simulation.

Field Distributions Around a Rectangular Crack in a Metallic Half-Space Excited by Long Current-Carrying Wires With Arbitrary Frequency

In this paper, we propose a semianalytical solution for evaluation of field distributions around a short rectangular crack in a metallic half-space excited by long current-carrying wires with arbitrary frequency. The governing Helmholtz equation is solved in three dimensions by separation of variables. The solution is obtained by developing 2-D Fourier series model and using exponential functions in the third dimension. To expand all possible field components in the metal, we first hypothesize a shielded dielectric rod waveguide where the shield enclosure lies at infinity, the surrounding dielectric (i.e., the metal) is a lossy material, and the rod dielectric is the crack opening. We then introduce hybrid modes each of which consists of two components, representing the TMy and TEy modes. The mode-matching technique is finally used to numerically solve the resultant boundary value problem. The unknown eigenvalues and field coefficients are found by searching for small singular values, using the singular value decomposition (SVD) in the resultant homogeneous linear system. The validity of our modeling technique is confirmed by comparison of our results with those obtained by measurement and finite integration code.

Harmonization of a Bandpass Shielding Enclosure and Its Internal Antenna

This paper investigates the way to harmonize a bandpass shielding enclosure (BPSE) and its internal antenna for achieving better performance. The harmonization greatly depends on the relative position of the antenna with respective to the adjacent periodic elements and the sideboards of the BPSE. For this harmonization, an internal high-permittivity dielectric resonator antenna is suggested due to its compact size and the minimum distance allowed between the antenna and the metallic sideboards of the BPSE. In addition, an appropriate zone for locating the antenna is suggested in terms of the relative position between the antenna and its adjacent BPSE elements. According to these suggestions, the antenna can be placed deep within a BPSE corner, a position which is often required in practice.

Using WCS‐FDTD method to simulate various cylindrical metallic enclosures

AbstractThe weakly conditionally stable (WCS) finite‐difference time‐domain (WCS‐FDTD) method in the cylindrical coordinate system is employed to compute the electromagnetic coupling and shielding of various cylindrical enclosures. In the WCS‐FDTD method, a larger time‐step size than that allowed by the Courant–Friedrich–Levy stability condition limitation can be set because the algorithm of this method is WCS. Consequently, an increase in computational efforts caused by fine cells due to thin sots can be prevented. The results from the WCS‐FDTD method agree well with the results from the conventional FDTD method, and the required CPU time for the WCS‐FDTD method is much shorter than that for the FDTD method. Careful investigation of different aspects of the shielding properties of the cylindrical enclosures is performed, and the shielding performance of the cylindrical enclosure and rectangular enclosure is compared. The result obtained in this paper can be used to design a practical cylindrical shielding enclosure. Copyright © 2010 John Wiley &amp; Sons, Ltd.

A Bandpass Shielding Enclosure for Modern Handheld Communication Devices

This letter proposes a new bandpass shielding enclosure (BPSE) for modem handheld communication devices. This enclosure is characterized by high transmittance at the specified wireless signal band and high shielding effectiveness (SE) outside this band. In addition, it has little influence on the impedance-matching bandwidth and antenna patterns of an internal antenna embedded inside the device. A prototype was created, simulated and measured. The simulated and measured results demonstrate the promising performance of this newly proposed shielding enclosure.

Resonance suppression of a spherical electromagnetic shielding enclosure by using conductive dielectrics

The resonance suppression for the electromagnetic shielding enclosure is theoretically investigated. A simple model of a double-layered spherical shell with a plane-wave illumination is assumed. When a spherical shell made of conductive dielectrics is covered with a thin metal layer, the conductivity of the dielectrics has an optimum value which minimizes the Q-factor at the fundamental resonant frequency. The optimum conductivity is shown to be a function of the resonant frequency and the thickness of the dielectric layer. The improvement of the shielding effectiveness by introducing the optimum conductivity is shown.

Measurement of Short- and Middle-Latency Auditory Evoked Fields in a Superconducting Shielded Environment

A superconducting magnetic shielding enclosure made of a bithmus-strontium-based high-critical-temperature superconducting material was formed to have better magnetic noise rejection at low frequencies than conventional magnetic shielding. To evaluate its efficiency, short- and middle-latency auditory evoked fields (SLAEFs and MLAEFs), which have weak amplitudes compared with other longlatency auditory evoked fields such as N1m, were measured. Measurements were made for three subjects with normal hearing in response to auditory clicks in the left ear. Multiple recordings were made at different locations over both lateral sides of the head, using a 7-ch SQUID with magnetometer coils. SLAEF and MLAEF components were observed at latencies of 6(M6), 10, 15, 20, and 30 ms in all subjects. Calculation of an equivalent current dipole source suggested that the source of M6 is located deep in the brain. The results are discussed alone with previous measurements of SLAEFs in terms of the response from the brainstem.

電磁シールド面に設けた開口のシールド性能に関する研究(その1) : 単一方形開口のシールド性能に関する実験

電磁シールド面に設けた開口のシールド性能に関する研究(その1) : 単一方形開口のシールド性能に関する実験

Monitor for integrity of seams in a shield enclosure

A novel concept for measuring the performance of shield enclosures is considered. It allows for the presence of aperture-like faults at unknown positions over the shield enclosure. The aperture penetration is measured in a manner appropriate to bounding the response of internal equipment. The technique leads to the location of the fault as well. >