EMI measurement and modeling techniques for complex electronic circuits and modules

This dissertation consists of four papers. In the first paper, a combined model for predicting the most critical radiated emissions and total radiated power due to the display signals in a TV by incorporating the main processing board using the Huygens Equivalence theorem and the radiation due to the flex cable based on active probe measurements was developed. In the second paper, a frequency-tunable resonant magnetic field probe was designed in the frequency range 900-2260 MHz for near-field scanning applications for the radio frequency interference studies by using a varactor diode providing the required capacitance and the parasitic inductance of a magnetic field loop (i.e., a parallel LC circuit). Measurement results showed good agreement with the simulated results. In the third paper, a wideband microwave method was developed as a means for rapid detection of slight dissimilarities (including counterfeit) and aging effects in integrated circuits (ICs) based on measuring the complex reflection coefficient of an IC when illuminated with an open-ended rectangular waveguide probe, at K-band (18-26.5 GHz) and Ka-band (26.5-40 GHz) microwave frequencies. In the fourth paper, a method to predict radiated emissions from DC-DC converters with cables attached on the input side to a LISN and on the output side to a DC brushless motor as load based on linear terminal equivalent circuit modeling was demonstrated. The linear terminal equivalent model was extracted using measured input and output side common mode currents for various characterization impedances connected at the input and output terminals of the converter --Abstract, page iv

EMI investigation and modeling of a flat panel display

It is often important to carry out EMI analysis in the design phase of an electronic product to predict the radiated emissions. An EMI analysis is important to predict if the product complies with the FCC regulations as well as to gain an understanding of the noise coupling and radiation mechanisms. EMI analysis and prediction of radiated emissions in electronic products that have an electrically large chassis, pose a challenge due to the presence of multiple resonant structures and noise-coupling mechanisms. The study focusses on the investigation of the main noise coupling mechanisms, the approach and methods used for the modeling of a flat panel display. Full-wave simulation models are a powerful tool for the prediction of radiated emissions and the visualization of coupling paths within the product. The first part deals with the measurement of radiated emissions from the display under standard test conditions and the identification of the main noise sources using near-field scanning. The contribution of the chassis components - frame, back cover and the back panel, to the radiated emission is analyzed using shielding measurements. Noise coupling from the main board, flex cables, display driver boards and the display is analyzed from measurements. The second part deals with the full-wave modeling of the components - main board, flex cables, chassis and the display driver boards. The modeling approach is demonstrated by highlighting some of the challenges in modeling larger structures having many details. The simulation model contains the main components of the TV that contribute to far-field radiation. The full-wave modeling is done using the CST Microwave Studio. Two sets of simulation models are described - the common mode models and the complete models. The use of the common mode models for the identification of the resonant structures is demonstrated. The far-field radiated emissions along with the coupling mechanism within the flat panel display can be predicted using the simulation model. --Abstract, pag

Microwave Reflectometry for Physical Inspections

Utilizing microwave reflections to compare a reference device with counterfeit and/or aging devices under test. The reflection from the device under test varies based on certain properties, which results in each device having a unique and intrinsic electromagnetic signature. Comparisons of the electromagnetic signature of the device under test to the electromagnetic signature of a reference device enable evaluating the acceptability of the device under test

Real Time Bridge Scour Monitoring with Magneto-Inductive Field Coupling

Scour was responsible for most of the U.S. bridges that collapsed during the past 40 years. The maximum scour depth is the most critical parameter in bridge design and maintenance. Due to scouring and refilling of river-bed deposits, existing technologies face a challenge in measuring the maximum scour depth during a strong flood. In this study, a new methodology is proposed for real time scour monitoring of bridges. Smart Rocks with embedded electronics are deployed around the foundation of a bridge as field agents. With wireless communications, these sensors can send their position change information to a nearby mobile station. This paper is focused on the design, characterization, and performance validation of active sensors. The active sensors use 3-axis accelerometers/magnetometers with a magneto-inductive communication system. In addition, each sensor includes an ID, a timer, and a battery level indicator. A Smart Rock system enables the monitoring of the most critical scour condition and time by logging and analyzing sliding, rolling, tilting, and heading of the spatially distributed sensors

Nanosecond Peak Detect And Hold Circuit With Adjustable Dynamic Range

This article presents a novel peak detect and hold (PDH) circuit for the measurement of the peak voltage of electromagnetic-field probes. These probes are used to capture the fields generated by electrostatic discharge (ESD) events in nongrounded portable devices. Therefore, a circuit combining small size, low power consumption, and nanosecond operation is needed. A topology using a discrete bipolar transistor structure with operational transconductance amplifier (OTA) and common-base storage capacitor charge control optimally meets the requirements. The circuit performance is demonstrated for different bias point settings. The error between the captured value and the actual pulse peak value is shown as a function of rise time, pulse length, amplitude, and bias settings. A comparison with the literature shows unmatched performance with respect to speed and power consumption. Using the bias settings, the PDH circuit can be adjusted to the sensor\u27s frequency response to minimize power consumption in a multichannel system containing sensors of different bandwidths

Structural optimization of thin walled tubular structure for crashworthiness

Crashworthiness design is gaining more importance in the automotive industry due to high competition and tight safety norms. Further there is a need for light weight structures in the automotive design. Structural optimization in last two decades have been widely explored to improve existing designs or conceive new designs with better crashworthiness and reduced mass. Although many gradient based and heuristic methods for topology and topometry based crashworthiness design are available these days, most of them result in stiff structures that are suitable only for a set of vehicle components in which maximizing the energy absorption or minimizing the intrusion is the main concern. However, there are some other components in a vehicle structure that should have characteristics of both stiffness and flexibility. Moreover, the load paths within the structure and potential buckle modes also play an important role in efficient functioning of such components. For example, the front bumper, side frame rails, steering column, and occupant protection devices like the knee bolster should all exhibit controlled deformation and collapse behavior. This investigation introduces a methodology to design dynamically crushed thin-walled tubular structures for crashworthiness applications. Due to their low cost, high energy absorption efficiency, and capacity to withstand long strokes, thin-walled tubular structures are extensively used in the automotive industry. Tubular structures subjected to impact loading may undergo three modes of deformation: progressive crushing/buckling, dynamic plastic buckling, and global bending or Euler-type buckling. Of these, progressive buckling is the most desirable mode of collapse because it leads to a desirable deformation characteristic, low peak reaction force, and higher energy absorption efficiency. Progressive buckling is generally observed under pure axial loading; however, during an actual crash event, tubular structures are often subjected to oblique impact loads in which Euler-type buckling is the dominating mode of deformation. This undesired behavior severely reduces the energy absorption capability of the tubular structure. The design methodology presented in this paper relies on the ability of a compliant mechanism to transfer displacement and/or force from an input to desired output port locations. The suitable output port locations are utilized to enforce desired buckle zones, mitigating the natural Euler-type buckling effect. The problem addressed in this investigation is to find the thickness distribution of a thin-walled structure and the output port locations that maximizes the energy absorption while maintaining the peak reaction force at a prescribed limit. The underlying design for thickness distribution follows a uniform mutual potential energy density under a dynamic impact event. Nonlinear explicit finite element code LS-DYNA is used to simulate tubular structures under crash loading. Biologically inspired hybrid cellular automaton (HCA) method is used to drive the design process. Results are demonstrated on long straight and S-rail tubes subject to oblique loading, achieving progressive crushing in most cases

Optimizing Measurement SNR for Weak Near-Field Scanning Applications

Conventional near-field scanning techniques often employ a general setup such as: broadband near-field probe output connected to a chain of amplifiers through a coaxial cable to a spectrum analyzer. In this paper, we investigated how the signal to noise ratio is influenced by the coaxial connection between the probe output and the first amplifier, types of probes, cooling the probes with liquid nitrogen and the amplifier\u27s noise figure. Eliminating cabling between probe and first amplifier, and using a low noise amplifiers helped increase signal-to-noise ratio by ~10dB. Further, liquid nitrogen is used to cool down a tunable resonant probe. This increases quality factor of the resonance and improves sensitivity. Thus, SNR is further improved by 10-12dB compared to a similar broadband setup

Wideband Microwave Reflectometry for Rapid Detection of Dissimilar and Aged ICs

A wideband microwave method is described as a means for rapid detection of slight dissimilarities and aging effects in integrated circuits (ICs). The method is based on measuring the complex reflection coefficient of an IC when illuminated with an open-ended rectangular waveguide probe, at K-band (18-26.5 GHz) and Ka-band (26.5-40 GHz) microwave frequencies. The spatially integrated reflected electromagnetic signature of a given IC is a function of its internal material properties, geometry and metallic deposition of circuit element, and wire bonds. Consequently, dissimilar (including counterfeit) and aged ICs exhibit markedly different reflection properties than their reference and new (nonaged) counterparts. In addition to measuring spatially integrated complex reflection coefficient (over the waveguide aperture), it is also integrated over the operating frequency band (spectrally integrated), resulting in significant increase in the robustness of the approach. Root-mean-squared-error, defined as the average Euclidean distance between two reflection coefficient vectors, is used to associate a quantitative metric to the complex reflection coefficient difference between two dissimilar ICs. Measurement results on several sets of ICs having the same package (DIP-14) and different functionalities, similar functionalities with slight differences in specifications, and aged ICs are presented. The results clearly indicate the capability of this method to differentiate among ICs having slight differences in packaging material properties and/or electronic circuitry

Common Mode Current Prediction from a Power Converter with Attached Cables Based on a Terminal Equivalent Circuit Model

An equivalent two terminal model based on Thevenin equivalents describes the common mode currents on the input and output side of a buck converter. A linear equivalent terminal model of the buck converter is created based on measured common mode currents for various common mode loads up to 300 MHz. The results using the terminal model agree well with the measurements for common mode load values that are within the range used for creating the terminal model, however, for loads far away from the characterization load range larger differences occur, as the power converter is a non linear circuit which is modelled by a linear equivalent circuit

A Frequency Tunable High Sensitivity H-Field Probe using Varactor Diodes and Parasitic Inductance

A frequency-tunable resonant magnetic field probe is designed for near-field scanning applications for the radio frequency interference studies. Tunable resonance is achieved by using a varactor diode providing the required capacitance and the parasitic inductance of a magnetic loop (i.e., a parallel LC circuit). An equivalent circuit model for the probe is described, analyzed, and used for designing the probe for achieving maximum sensitivity. The resonance frequency of the designed probe is tunable in the frequency range of 900-2260 MHz that covers multiple radio bands, such as the GSM900, UMTS, and GPS bands. The sensitivity of the probe at the resonance frequency is about 7-9 dB higher than that of an equivalently sized broadband magnetic field probe throughout the tunable frequency range. The measured frequency response and sensitivity over a microstrip trace using the fabricated probe shows good agreement with the simulated results of the equivalent circuit model and the full-wave simulation model