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.

For emission from a printed circuit board (PCB) by the common-mode current, the suppression method based on the image theory by placing a conducting plate under the PCB is presented. In order to evaluate the suppression effect by this method the radiation power from the PCB is calculated by using FDTD method. The numerical results show that placing the conducting plate suppresses the emission by the common-mode current. Especially, using the conducting plate bent the sides, it is possible to suppress the emission by the small conducting plate. Further, the experimental results of a radiation power and a maximum electric field intensity show the validity of the numerical results.

The power line communication (PLC) system should be investigated with respect to the influence on electromagnetic environments. Longitudinal conversion loss (LCL) and input impedance are important parameters for evaluating the influence because they are closely related to the radiated, conducted, and inducted emission. An indoor AC mains system consisting of electrical equipment and an AC mains line was modeled by four-port networks, and the LCL and the input impedance were calculated. The parameters of the four-port networks were determined from theory and measurement. The analytical model was examined using a simple network and the results show that the calculated values agreed with the measured ones. The LCL and the input impedance were investigated at the AC mains port in some existing buildings, and the measured results almost agreed with the calculated results derived from the indoor AC mains system model.

Unwanted electromagnetic emission occurs due to the common-mode current on the cables entering a PC's metal enclosure and can be treated as wire antennas passing through the apertures of the enclosure. To reduce the emission, a stack of metal rings is suggested to be placed around the cable and external to the aperture, adopting the concept of a Coaxial Band-Stop Filter, for the first time. The influence of this novel structure on the common-mode current is examined in the FDTD-method frame work.

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.

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.

In a direct conversion receiver for mobile communication, it is important to reduce power dissipation. Because a low pass filter in a direct conversion receiver must suppress adjacent channel signals, a high order and high power dissipation is often required in the low pass filter. We propose a new phase compensation technique suitable for a low power transconductor used in a GmC filter as a low pass filter. The new phase compensation technique reduces 10% of power dissipation.

A new design concept for a common-mode signal suppression circuit for a balanced-type filter has been investigated. The degradation mechanism of the balance characteristics was studied. The degradation is caused by the common-mode signals combined with the differential-mode signals in the balanced terminals. The concept employed is the reduction of the common-mode signal using a common-mode signal suppression circuit, connected to the balanced terminals. A serial resonance circuit is formed, in which the common-mode signals are shorted to ground. The circuit was applied to the balanced-type Surface Acoustic Wave (SAW) filter. The improvement in balance characteristics, without increasing in the insertion loss, was confirmed by experiments for Global System Mobile (GSM) applications.

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.

Fundamental EMI source that generates common-mode radiation from printed circuit boards (PCBs) is investigated here. It is done by modelling the ground lines of PCBs as imperfect ground. The radiation emission in the far zones from PCBs is obtained by regarding interconnects on PCBs as transmission lines and the far field emission is evaluated based on the current distribution of the lines. The finite size ground trace is defined as an imperfect ground, that can be viewed as an inductive reactance which, in turn, causes the ground return path to radiate as a wire antenna. For the accurate analysis of imperfect ground effect, we divide the equivalent circuit into N sections. In addition, based on transverse electromagnetic (TEM) assumption, we estimate the electromagnetic interference (EMI) of three typical PCB geometries, namely, coplanar strips, parallel-plate strips and microstrips. The quantitative value of induced current distribution along the ground return path depends on the physical size, geometry and length of ground traces. Measured data are presented to confirm the result of numerical analysis. A knowledge of EMI source mechanisms and their relationship to layout geometries is necessary to determine the essential features that must be taken into account to estimate emissions and provide direction for reducing EMI due to interconnects on PCBs.

Common-mode (CM) radiation from a cable attached to a conducting enclosure has a typical dipole-type antenna structure, in which an equivalent noise voltage source located at the connector excites the attached cable against the enclosure to produce radiated emissions. Based on this mechanism, a simple method for predicting the CM radiation from the cable/enclosure structure was proposed. The method combines an equivalent dipole approximation with sinusoidal current distribution and CM current measurement at a specified location on the cable. Its validity was examined in comparison with the far-field measurement and finite-difference time-domain (FDTD) modeling. The predicted resonance frequencies and CM radiation levels were validated with engineering accuracy, i.e., within 30 MHz and 6 dB, respectively, from the measured and FDTD-modeled results in the frequencies above 150 MHz.

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.

A fully balanced (FB) transconductor using two multi-input single-ended (SE) CMOS transconductors is proposed, where the transconductors use MOS transitors operating in a triode region for achieving a wide linear input-range. SE circuits are easier to design than differential circuits and inherently reject common-mode (CM) signals. The multi-input structure is used to make a CM feedback loop and to determine an output CM voltage. A high-output-resistance current mirror is used in converting a differential signal to a single-ended signal in order to achieve a high common-mode rejection ratio (CMRR) and a high output-resistance of the transconductor. The FB transconductor achieves a 2-Vpp linear input range at a 2.5-V power supply and consumes 1.74 mA. The output resistance of the FB transconductor is 2 MΩ. It operates at 2 V with a linear input-range of 1.2 Vpp and at 1.6 V with a linear input-range of 0.9 Vpp. A 2.5-V 2.5-MHz FB Gm-C filter using the FB transconductors achieved a CMRR of 45 dB and a passband IIP3 of 32 dBm.

The radiation emission in far zones from printed circuit boards (PCBs) is obtained by treating lines on PCBs as transmission lines and calculating the far-field emission due to current distribution on lines. In this paper, we present a more precise circuit model, based on TEM assumption, to decompose the total current into differential-mode current and common-mode current. This circuit model is based on transmission line model, but it considers the effect of ground trace. The finite size ground trace can be viewed as an inductive reactance. A knowledge of the net inductance of the ground trace can aid in the analysis and investigation of PCBs emission. We show the derived equations of the modified transmission lines for the geometrics of practical interest. As time-varying current passes through such ground trace, a voltage drop due to the inductance of the trace will act as a source of the common-mode current. Furthermore, charge stored in capacitance between signal and ground traces will cause the current pulses returning to their source. The magnitudes of currents are slightly unequal in the signal and ground traces, which can cause common-mode current to flow. An unbalanced circuit on a PCB constructed with signal and ground trace pairs will radiate as an asymmetric folded-dipole. By antenna theory, the contribution of differential-mode and common-mode currents to radiated emission of PCBs can be calculated. In addition, comparisons between experimental results and calculation results are also given.

A simple method for diagnosing noise immunity of printed circuit boards (PCBs) by the bulk current injection (BCI) test was proposed, which can contribute to the PCB trace designs for common-mode noise. A grading index, which is defined as the ratio of the stray capacitances with and without critical IC of malfunction, was introduced to distinguish the PCB susceptible to the common-mode noise. This proposed method was validated experimentally using four PCBs with the same circuit but different trace design. It was observed that the noise immunity of PCBs had a good correlation with the values of these grading indices.

An optical magnetic field measuring system using diluted magnetic semiconductors (DMS) probes is presented. The attractive features of DMS for building current/ magnetic field sensors are outlined. The system configuration includes a common-mode noise rejection scheme (CMR) to eliminate optic intensity noise induced in the fibre links by environmental vibrations. The CMR scheme relies on a pulse delay method based on the creation of two relatively delayed replicas of the photodetector output signal and their subsequent subtraction (division). Theoretical and experimental analyses of the system operation are developed and noise rejection methods using subtraction and division are presented and compared. Although CMR by division seems to be more appealing from the theoretical viewpoint (due to the rejection of intensity noise caused both by environmental vibrations and laser source output power fluctuations), in practical terms the subtraction is more reliable and easier to implement. The noise rejection figure measured experimentally is about 17 dBV for CMR both by subtraction and by division. A system calibration curve is presented. The minimum magnetic flux density detected with the system is 0.06 mT rms.

Low-voltage technique for IC is getting one of the most important matters. It is quite difficult to realize a filter which can operate at 1 V or less because the base-emitter voltage of transistors can hardly be reduced. A design of a low-voltage continuous-time filter is presented in this paper. The basic building block of the filter is a pseudo-differential transconductor which has no tail current source. Therefore, the operating voltage is lower than that of an emitter-coupled pair. However, the common-mode (CM) gain of the transconductor is quite high and the CMRR is low. In order to reduce the CM gain, a CM feedback circuit is employed. The transconductance characteristic is expressed as the function of hyperbolic cosine. The designed filter is a fifth-order gyrator-C filter. The transconductor and the filter which has a fifth-order Butterworth lowpass characteristic are demonstrated by PSpice simulation. Transconductance characteristic, CMRR and stability of the transconductor are confirmed through the simulation. In the analysis of the filter, frequency response and offset voltage are examined. It is shown that the filter which has corner frequency of the order of megahertz can operate at a 1 V supply voltage.

A technique for realization of low-voltage OTAs is presented in this letter. A very low-voltage differential-output OTA is realized by employing a new common-mode amplifier in the common-mode feedback circuit. The results of PSpice simulations are shown. The proposed OTA can operate at a 0. 9 V supply voltage.

In this paper, two types of improved CMRR CMOS OAs, N type and P type, without common-mode feedback and the cascode current mirrors, are proposed. The CMRR of proposed OAs are enhanced by compensating variations in tail bias current, caused by a common mode input signal, at the differential input stage, by means of feedforward controlled current source. Simulation results show that the CMRR of the proposed OAs are 20dB higher than that of conventional OAs.

It has become very important to study the lightning surges that were induced in subscriber telecommunication equipment because of the increase of susceptible circuits to the over voltage. The test generator is desire to be developed evaluating the resistibility of equipments against lightning surges. This paper proposes a new lightning-test method for subscriber telecommunication equipment. The waveform of the test generator simulates that of the induced lightning surge voltage caused by a nearby return stroke. The output impedance of the surge generator is determined to match the common-mode impedance of telecommunication lines. The damaged condition of circuit parts and the trouble occurrence rate estimated by using this method agree well with actual observations.