Electromagnetic (EM) radiation from a feed cable attached to a printed circuit board (PCB), which is commonly encountered electromagnetic interference (EMI) problem at high-speed electronic PCB designs, is investigated by experimental and finite-difference time-domain (FDTD) modeling. In this paper, we propose and demonstrate a guard-band structure as a method for suppressing the EM radiation from a PCB with a feed cable. A signal trace is located between two ground traces (guard-band: GB). Four different cross-sectional PCB structures, which are commonly used in microwave integrated circuits as typical structures, are used to compare the guard-band structure. Frequency response of common-mode (CM) current, electric field near a PCB, and far electric field (radiated emission) are investigated as characteristics of the EMI. Results show that the shield structure is effective in suppressing the CM current at lower frequency. However, structures in which a conductive plate exists near the signal trace yield resonances with high level peak on CM current, near and far-field. On the other hand, the guard-band structure is more effective than other structures in suppressing the EM radiation in the considered frequency range. Therefore the guard-band will be effective for high-density PCB packaging with high-speed traces.

Switching device used on digital and inverter circuits such as a stabilizer of fluorescent lamp is one of main sources of electromagnetic noise. To make such noise characteristics clear, using a simple printed line model with a TTL IC as a switching device, electric far field noise radiating from that model is measured in an anechoic chamber. It is shown typical results and that noise characteristics can be evaluated by comparing the spectrum and spectrum change of the harmonics of 3 MHz switching pulse using the same switching device. And the characteristics of the electric field noise with PCB thickness and strip line width changed are compared with the magnetic near-field noise measured by a small shielded loop antenna. The results indicate that the electric field noise strength, on the case where the width is 7 mm and the thickness is 0.51 mm, is larger than that on other cases in the range from 50 to 150 MHz. And it is confirmed that the magnetic near-field noise increases as the loop antenna approaches the IC and varies depending on the PCB thickness and the line width. However, the spectral profile of the electric field noise is different from the magnetic near-field noise.

To provide basic considerations for the realization of methods for predicting the electromagnetic (EM) radiation from a printed circuit board (PCB) with plural signal traces driven in the even-mode, the characteristics of the EM radiation resulting from two signal traces on a PCB are investigated experimentally and by numerical modeling. First, the frequency responses of common-mode (CM) current and far-electric field as electromagnetic interference (EMI) are discussed. As the two traces are moved closer to the PCB edge, CM current and far-electric field increase. The frequency responses in the two signal trace case can be identified using insights gained from the single trace case. Second, to understand the details of the increase in CM current, the distribution of the current density on the ground plane is calculated and discussed. Although crosstalk ensues, the rule for PCB design is to keep two high-speed traces on the interior of the PCB whenever possible, from the point of view of EM radiation. Finally, an empirical formula to quantify the relationship between the positions of two traces and CM current is provided and discussed by comparing four different models. Results calculated with the empirical formula and finite-difference time-domain (FDTD) modeling are in good agreement, which indicates the empirical formula may be useful for developing EMI design guidelines.

This study is to clear how the impedance and the current of a simple printed line model involve to the near field electromagnetic noise radiation, by computer simulation and experiment. Frequency characteristics of the impedance and the current of the printed line and the near field noise are considered, from low to high frequency components. The model size 225 60 0.51 mm3, length of the line is 185 5 mm2 and 1 kΩ termination resistance is connected as non-matching load. FDTD method is used to calculate the impedance, the current waveform and the near field noise. Measurements of the line impedance and the near field noise spectrum by clock pulse are compared with simulations. It is cleared that using FDTD method, the characteristic of impedance of the printed line model, the current waveform, and the near field noise can be calculated at the same simulator. As results, from calculation and measurement, the near field noise has a relationship with impedance of printed line model. Emission at frequency less than 200 MHz, which is near the wavelength of λ/4, is observed at significant intensity. So, it is suggested that near field noise emission should be discussed from low to high frequency and analysis of the characteristics of the printed line and magnetic near field noise using FDTD method and measurement is useful to basic examination of complex PCB models.

As a new material, silver (Ag) coated fabric has been developed, and its use for shielding electromagnetic radiation is expected. In this paper, seven kinds of Ag coated fabrics, woven, knitted and nonwoven by Ag coated fibers, are prepared, and placed over a PCB with a microstrip line, which is used as a noise source. By measuring the input impedance of the microstrip line, the distance between the PCB and the fabric is fixed to 8 mm to reduce the coupling paths. The shielding effect SE of those fabrics was compared by measuring the magnetic near-field with a small shielded-loop probe. In the results, the resonance frequency is dependent on the fabric's length, as well as the case of a copper sheet. Comparing the texture, the SE of woven and nonwoven fabrics is larger than the knitted fabric. Comparing with the copper sheet, the SE of the fabrics is smaller below 200 MHz, but elsewhere is almost the same.

In this study, the frequency and spatial properties of undesired electromagnetic radiation distribution around a simple printed circuit board (PCB) model, which only has the mismatching printed line (PL) and ground, are estimated. Finite difference time domain (FDTD) modeling is developed for the analysis space, which is 500 400 51 mm3 in size, around the PCB. As the driving clock pulse has a very wide frequency bandwidth, ranging from kHz to GHz, basic and precise investigation of the noise emission mechanism from the basic model is performed. The results of the magnetic field Hx on the PCB as determined by FDTD simulation, and those of the experiment, driven by a clock pulse, agree well. The results show that although this approach is basic and simple, it becomes clear that the frequency and spatial characteristics of the electric and magnetic field near the PCB are influenced by the wavelength of the frequency and appling the driving clock pulse, and the low-frequency component of the electromagnetic distribution around the PCB is larger than the high-frequency components. It is suggested that the low-frequency noise problem should be carefully considered.

The effects of Gaussian electromagnetic noise and non-Gaussian one on TV picture degradation are studied by using a composite noise generator which can control noise parameters. Three kinds of still pictures and four kinds of motion pictures are tested, and the picture degradation is subjectively evaluated with five-grade impairment scale. The tendency of the picture degradation against the every picture is almost the same. But MOS (Mean Opinion Score) between still picture and motion picture degradation is different in some measure when the power of burst noise is small.

EMI coupling paths in an electronic controller are investigated experimentally. Common-mode current measurements on the attached cable are used for diagnosing changes made to the EMI coupling path. Experiments that include shielding various portions of the PCB, and re-routing high-speed traces are conducted to characterize the coupling path. A means of identifying and characterizing EMI coupling paths in functioning hardware, and relating them to design features, is demonstrated.

Common-mode (CM) current on a feed cable attached to printed circuit board (PCB), which is one of main source of undesired electromagnetic radiation problem, is investigated by experimental and finite-difference time-domain (FDTD) modeling. In this paper, frequency responses of CM current on PCB and feed cable are modeled and analyzed as an electromagnetic interference (EMI) antenna, which depends on the configuration of PCB with a wire cable. Several different configurations are prepared to demonstrate the effect of PCB dimension on resonance frequencies of CM current. In the results, EMI antenna in the frequency band around the first resonance frequency was comprised of the ground plane and cable. In order to explain the frequency response of CM current, two EMI antenna models are proposed and demonstrated. EMI antenna is comprised of the ground plane and cable, and the other EMI antenna is comprised of the trace on the ground plane. It is suggested that the result is one of basic consideration for the ground plane with cable that have high EMI problem and resonance frequency of CM current.

We have recently developed a programmable composite noise generator (P-CNG) which can easily control noise parameters such as average power, time-based amplitude probability distribution (APD), crossing rate distribution, occurrence frequency distribution and burst duration. Two applications of the P-CNG are demonstrated to show its usefulness. For the first application, Middleton's Class A noise is simulated. A method of setting parameters for Class A noise is demonstrated. The APD of P-CNG output is in good agreement with that of true Class A noise. In the second application, the P-CNG is used for subjective evaluation test (opinion test) of TV picture degradation. Five simple composite noise models with two kinds of APD are used. Other parameters such as average power are kept constant. Experimental results show that the envelope and APD of composite noises do not greatly influence the subjective evaluation. Finally the capabilities of the P-CNG are shown.

An effect of complex permeability of noise suppression sheets (NSS) on circuit parameters was investigated by a magnetic circuit analysis using cross-sectional size and material parameters. The series resistance and inductance of the coplanar waveguide (CPW) with a NSS considering the effect of the complex permeability of the NSS were quantitatively estimated. The result indicated that the imaginary and real part of the effective permeability affected the resistance and inductance, respectively. Furthermore, this analysis was applied to an 8-µm-wide CPW with a 0.5-µm-thick Co85Zr3Nb12 film for quantitative estimation of the resistance, the inductance and the characteristic impedance. The estimated parameters were almost similar to the measured values. These results showed that the frequency characteristics of the circuit parameters could be controlled by changing size and material parameters.

The effect of a grounded conductive sheet placed over a PCB with a microstrip line on the electromagnetic noise shielding is discussed experimentally and with FDTD modeling. The grounding position of the sheet, which is connected with the ground plane of PCB, is changed. In results, the resonance frequency is shifted by the grounding position, and reducing the resonance of the input impedance should make a more effective shielding for EM noise radiation below 1 GHz.

The effect of a conductive sheet placed over a PCB with a microstrip line on electromagnetic noise shielding is investigated. As a typical conductive sheet, a copper sheet is used, and is not grounded. First, the input impedance of the microstrip line and the magnetic field when varying the distance between the PCB and the conductive sheet are measured, and the distance that does not affect the signal transmission is set at 8 mm. Second, the effect of the conductive sheet size on the magnetic field radiation is discussed by measurements and FDTD modeling, and the magnetic near-field distribution around the PCB is visualized by using the FDTD calculation. A conductive sheet whose width is larger than the PCB width should be effective for suppression of the magnetic near-field noise radiation just above a PCB.

It has been demonstrated that a common-mode (CM) current can dominate the EMI processes up to 1 GHz, despite the fact that a CM current is smaller than a differential-mode (DM) current. However, this description is insufficient to describe behavior above 1 GHz. In this paper, the correspondence of CM and DM components for total electromagnetic (EM) radiation from a printed circuit board (PCB) with surface microstrip line, which is commonly used in microwave integrated circuits, at gigahertz frequency is studied experimentally and with finite-difference time-domain (FDTD) modeling. In order to characterize the EM radiation, the frequency response of the CM current, the electric field near the PCB, and the electric far field are investigated. First, the frequency response of the CM current, near and far-fields for the PCB with an attached feed cable are compared up to 5 GHz. Although the CM current decreases above a few gigahertz, near and far electric fields increase as the frequency becomes higher. Second, in order to distinguish between CM and DM radiation at high frequency, the frequency response and the angle pattern of the far-field from a PCB without the feed cable are discussed. The results show that radiation up to 1 GHz is related to the CM component. However, depending on polarization and PCB geometry, radiation may be dominated by the DM rather than the CM component. The results indicate that the DM component may be more significant relative to the CM component, and the increase in EM radiation can not be predicted from only the frequency response of CM current. Therefore, identifying the dominant component is essential for suppressing the EM radiation. This study is a basic consideration to realize a technique which is effective on the suppression of the EM radiation from the PCB with an attached feed cable.