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A susceptibility was identified experimentally when an external feature was added near an irregular aperture that spanned two faces of the shielding enclosure of an equipment under test. The susceptibility was due to a resonant response that occurred at a lower frequency than that expected by the resonances of the aperture, enclosure cavity, or external feature considered in isolation. Numerical modeling showed that currents induced on the exterior of the enclosure when the external feature is in place couple to the currents surrounding the aperture, leading to a longer resonant length than provided by the aperture alone. The resonant response giving the susceptibility was observed with various changes in aperture and external feature dimensions, provided that the aperture spanned two faces and the external feature was aligned with the enclosure edge that the aperture spanned. The low-frequency susceptibility can be mitigated by electrically connecting the external feature to the enclosure edge to interrupt the external current path. The higher-frequency resonant coupling due to the irregular aperture alone was not affected by the suppression of the external current.

In the space community, there is increasing interest in adaption and augmentation of launch fairing thermal-acoustic blankets, to also control electromagnetic environment threats. This paper reports on the development of simulation methods to both optimize blanket materials for RF absorption and to provide quantitative guidance on their minimal spatial deployment inside the fairing. A stochastic power-balance model with multiple connected sub-cavities is used to map the reverberant electric field in the fairing when RF absorbing blankets are applied only locally – ie only partial coverage of the fairing wall. The sub-cavity Q factors resulting from different RF absorption blanket materials is calculated from published reflection loss data and a field incidence correction factor. Comparison with model-scale test data verified that the model correctly predicts the attenuation of different absorber materials, the spatial distribution of the field and the improvement in shielding effectiveness.

The electric field levels established at various points within a modeled rocket fairing under different excitations are measured. Both interior sources placed within different fairing sub cavities and exterior excitation was used. The effect of the addition of different absorbers on the electric field level in different sub cavities was investigated as well. The shielding effectiveness of the fairing within the different fairing sub cavities was considered. The relation between the total surface of absorber and the electric field level studied. In addition, the electric field level excited inside the fairing under external illumination was numerically simulated. The laboratory measurements were verified through comparison with the simulation results.

A launch vehicle payload fairing scale model has been designed, fabricated, and tested to investigate the reverberant electromagnetic fields within launch vehicle fairings. The fairing scale model uses a mechanical stirrer to attain statistically uniform fields within the fairing cavity. A removable payload model and payload adapter model are included in the fairing to study the interactions of fields with these structures. The layering of the fairing walls, use of shielding gaskets, and field probes to measure the cavity fields are described. The quality factor is measured when the fairing cavity is empty and when the surrogate payload and payload adapter models are added. The quality factor of the empty fairing measured from about 32 dB at 1 GHz to 41 dB at 6 GHz. The Q values dropped approximately 2 dB across the band when the payload and payload adapter models were placed in the fairing cavity. Measurements of Q at different probe positions within the fairing yielded similar results.

A study of the effect of the field-sampling probe configuration used in nested-cavity measurements has been performed. The outer cavity was an overmoded reverberation chamber and the inner cavity was a small conducting enclosure that included a coupling aperture. Mechanical stirring within both the external and internal cavities was combined with frequency stirring to yield the mean received signal. Monopole, meanderline, and log-periodic probes were evaluated. The three-dimensional meanderline probes overall showed the best performance, better sampling the low-frequency signals where the inner cavity is undermoded. Despite the advantages, the mean signals levels still show a dependence on the specific configuration of the meanderline used, particularly at low frequency, and care must be used in interpreting the measured levels.

The effects of cable routing within a shielding box has been evaluated using a numerical electromagnetic package. Different cable paths with both constant and varying lengths have proposed. The cable-feed port reflection coefficient and radiated electric field were considered for different test cases. The influence of slot apertures in the enclosure itself, gaps between external structures and the enclosure body, and cable route on radiated electric field and excited slot resonances are examined. The coupling between enclosure and cable resonances and their effects radiation emission are presented. The effect of the wire path on the slot resonances is also shown. The simulations for representative cases were empirically verified through comparison with laboratory measurement.

The external noise immunity of a real structure’s scale model has been studied. Using the scale model improves the accuracy and reduces the convergence time of numerical simulation. Different coupling paths into the structure were investigated using the Computer Simulation Technology (CST) electromagnetic simulation software. The effects of slot, aperture-slot, and gap-slot coupling apertures on the shielding performance of the scale model are the same as for the real tunnel box. The simulation results were experimentally verified through three different measurement setups.

In this paper, the immunity of a tunnel box shielding structure against external electromagnetic noise has been studied. The electromagnetic susceptibility of the structure has been characterized by determining different coupling paths into the system. Computer Simulation Technology (CST) electromagnetic simulation software was used for all simulation. The effects of slot, aperture-slot and gap-slot on shielding performance have been studied. The simulation results were verified through measurement.

A dual band FSS based on array of double square ring shaped resonators has been proposed. The proposed structure represents a wide-angle perfect rejection of incidence wave and polarization independency. The rejection occurs at two different resonant frequencies as high as 98% and 99%, at 2.45(GHz), 5 (GHz) respectively. The proposed Frequency Selective Surface has designated for blocking the WI-FI signals and screen room applications. Simulation results show polarization independency for both rejection bands.

This paper propose a new method for improving shielding effectiveness (SE) of a rectangular enclosure with multiple circular apertures. In this method in order to compensate the effects of the apertures on (SE) parameter, we use two metallic walls each containing apertures instead of the one wall. By using two walls for shielding an enclosure, the shielding effectiveness of the enclosure will improve. The numerical simulation uses a symmetric condensed node of TLM – TD (Transmission line Modeling Method – Time Domain) and subsequent Fourier Transform and the result was verified by HFSS and CST software. We obtain the shielding effectiveness response to an electric field impulsive excitation. It is shown that field polarization and enclosure direction has a noticeable effect on SE that should be considered in SE calculations. The effect of different parameters and improving the shielding effectiveness of a metallic enclosure with extra wall is studied. An optimization of the influence of the place of apertures in the walls and the diameter of circles on two walls is presented.

The transmission line matrix time domain (TLM-TD) method is used to simulate the electromagnetic pulse (EMP) cou-pled inside a shielding box with an aperture. Simulations for different electromagnetic pulses regarding to different rise time and fall time have been performed. The results for shielding effectiveness of these different excitations have been presented. A simple method that uses an extra metal for reducing the interference has also been proposed and tested.

This paper presents a high Polarization and wide angle independent metamaterial absorber (MA) based on triple hexagonal shaped resonators. This metamaterial unit cell absorber possesses a nearly wide angle perfect absorption of incidence wave and polarization independence. The absorption is occurred in three different frequencies. The absorptivity is as high as 98%, 93% and 94%, at 3.5(GHz), 4.7(GHz) and 6.6(GHz), respectively. The simulation of the simulation agrees well with the experiments, regarding to return loss and absorption. The important features of this method are simple fabrication of metamaterial absorber and maximum absorption in three frequencies. The proposed metamaterial absorber has wide applications such as thermal detector, stealth technology and imaging. Moreover, a very good agreement between simulation and measurement results has been observed.

n this paper an 8-bit shift register is designed by using D-Flip flop that the existing connections are performed through the second layer and by the second type of metal and its area and power has been calculated and also the simulation results have been shown. The obtained results indicate that the performance of this shift register compared with the other shift registers which are built in the other way is more desirable and better. The closed circuit layout related to these shift registers is shown as well.

A new metamaterial absorber has been proposed in this paper. The absorber which is designed based on this metamaterial unit cell possesses a nearly wide angle perfect absorption of incidence wave and polarization independence. The absorption is occurred at 10(GHz)and the absorptivity is as high as 94%.