Electromagnetic interference shielding mechanisms of CNT/polymer composites

Reflection and absorption contributions to the electromagnetic interference shielding of single-walled carbon nanotube/polyurethane composites

Praise for Noise Reduction Techniques IN electronic systems "Henry Ott has literally 'written the book' on the subject of EMC. . . . He not only knows the subject, but has the rare ability to communicate that knowledge to others." EE Times Electromagnetic Compatibility Engineering is a completely revised, expanded, and updated version of Henry Ott's popular book Noise Reduction Techniques in Electronic Systems. It reflects the most recent developments in the field of electromagnetic compatibility (EMC) and noise reductionand their practical applications to the design of analog and digital circuits in computer, home entertainment, medical, telecom, industrial process control, and automotive equipment, as well as military and aerospace systems. While maintaining and updating the core informationsuch as cabling, grounding, filtering, shielding, digital circuit grounding and layout, and ESDthat made the previous book such a wide success, this new book includes additional coverage of: Equipment/systems grounding Switching power supplies and variable-speed motor drives Digital circuit power distribution and decoupling PCB layout and stack-up Mixed-signal PCB layout RF and transient immunity Power line disturbances Precompliance EMC measurements New appendices on dipole antennae, the theory of partial inductance, and the ten most common EMC problems The concepts presented are applicable to analog and digital circuits operating from below audio frequencies to those in the GHz range. Throughout the book, an emphasis is placed on cost-effective EMC designs, with the amount and complexity of mathematics kept to the strictest minimum. Complemented with over 250 problems with answers, Electromagnetic Compatibility Engineering equips readers with the knowledge needed to design electronic equipment that is compatible with the electromagnetic environment and compliant with national and international EMC regulations. It is an essential resource for practicing engineers who face EMC and regulatory compliance issues and an ideal textbook for EE courses at the advanced undergraduate and graduate levels.

Electromagnetic Compatibility Engineering

Flexible graphene/polymer composite films in sandwich structures for effective electromagnetic interference shielding

Besides the excellent high-temperature mechanical properties, Si3N4 and SiC based ceramics containing insulating or electrically conductive phase are attractive for their tunable dielectric propert...

Electromagnetic properties of Si–C–N based ceramics and composites

Plane-wave shielding theory is developed and discussed for a number of important cases such as single, double, and laminated shields. For application to design, the basic expressions are modified and plotted with universal parameters for convenient use in performance calculations of both solid and perforated sheets. Performances of solid copper and iron shields have been calculated and are presented in both tabular and graphical form. For these and other materials, measurement results of various experiments are tabulated for a number of different material forms and for various incident-wave impedances. Some consideration is given to shielding discontinuities and trends in modern shielding enclosures. >

Shielding theory and practice

Research was conducted to determine the low-frequency shielding effectiveness of magnetic materials. Both analytical and experimental approaches were used. This work is unique in that it provides a technique for experimental separation of the various terms in the shielding expression. Expressions of shielding effectiveness of flat sheets for very low frequencies are derived, and the results of experiments with the following are given: 1) sheet materials, including AMPB-65,1 HyMu 80, conetic AA, mumetal, copper-plated AMPB-65, and galvannealed steel; 2) AMPB-65 sheets perforated with various size holes and various numbers of 0.125-inch diameter holes; 3) an overlap junction of two AMPB-65 sheets with a) various numbers of fastening screws and b) various depths of overlap; 4) overlap junctions of copper-plated AMPB-65 sheets; 5) AMPB-65 sheets clamped in Lindsay structure; and 6) honeycomb-core stainless steel sandwiches.

ELF and VLF Shielding Effectiveness of High-Permeability Materials

A low-frequency resonance in the 5- to 200-kHz range has been discovered in typical shielding enclosures. It is due to unequal phase shifts in wave transmission to a receiving point via two or more parallel paths: one through the shielding material itself and others through leakage paths such as seams. Theoretical and experimental results are shown to be in close agreement and indicate a new approach to the design of shielding enclosures.

Low-Frequency Shielding Resonance

An RF shielding design procedure based on a nonuniform transmission-line analogy of shielding is presented. The theory treats the propagation of an EM wave through the walls of a shielding enclosure as a path through the material itself in parallel with one or more paths through defects, seams, or other discontinuities in the shielding structure. Data necessary for the design of a shield are presented in the form of material factors, seam factors, size factors, and others. Factor dependency on frequency is discussed. Two typical design examples are given.

RF Shielding Design

Amplitude-probability-distribution (APD) data are presented for ignition emanations from V-8 engines of used motor vehicles. Outputs from both single and multiple engines running at 1500 rpm were measured with an omnidirectional antenna over the frequency range from approximately 20 MHz to 1 GHz. In each case, the antenna was oriented similarly with respect to the vehicle(s)-vertical, height 3 m, distance 10 m. Results are presented on Weibull-distribution sheets and compare favorably with those of Hsu et al. [1] using a different technique. On each sheet, APD distributions are given for various received bandwidths between 1 and 300 kHz. For the larger bandwidths, curves are straight lines with large negative slopes. At narrower bandwidths and for multiple vehicles, slopes are less steep. Major conclusions from the APD results include the following. 1) Although overlapping of successive pulses at a detector becomes more prominent at narrower bandwidths, measurements are still valid and representative for a given bandwidth. 2) Measurements indicate good repeatability. 3) Curve shapes are essentially independent of tuned frequency, but do depend upon bandwidth and number of vehicles. 4) Amplitudes are functions of tuned frequency and number of vehicles.

Richard B. Schulz

Papers

Shielding theory and practice

ELF and VLF Shielding Effectiveness of High-Permeability Materials

Low-Frequency Shielding Resonance

RF Shielding Design

APD Measurements of V-8 Ignition Emanations