Satyajeet Shinde

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.

Investigation of interference in a mobile phone from a DC-to-DC converter

Turning on the LCD screen of a mobile phone causes desensitization of its receiver in the GSM lower frequency band (900 MHz). In this paper, the measurement techniques used for the investigation of intra-system interference in a mobile phone caused due to the DC-DC converters present on-chip the LCD driver IC are presented. An equivalent noise source model is created by modelling the flexible printed circuit board traces and obtaining a Thevenin equivalent noise by changing the load conditions.

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.

Electro-Mechanical Structures for Channel Emulation

Channel emulators are used to evaluate communication system performance either in absence of the real channel or to test the systems response for varying channel characteristics. For high speed differential digital channels bandwidths in excess of 20 GHz are common making it difficult to recreate the channel performance by electronic means such as FIR filters. An alternative solution is using a low loss short transmission line and having its properties modified by mechanical means. Passive structures are robust, have a frequency range only limited by the low loss trace, do not add noise, cannot be damaged by ESD and are very economical. This paper describes two electro-mechanical structures for introducing loss and nulling into the frequency response of a channel. The first part describes the design of a mechanically tuned quarter-wavelength stub filter that can be used to emulate the resonances of a channel. In the second part, an electromechanical structure, consisting of Bragg grating and lossy materials, is constructed to emulate the loss behaviour and the resonances of a channel.

Investigating intra-system radio-frequency interference from high-speed traces to a GPS patch antenna

High-speed traces routed in close proximity to a GPS patch antenna in a compact consumer electronic device could cause desensitization of the GPS receiver. Noise coupling mechanisms between the traces and the antenna are studied, together with the field patterns of the patch antenna. The insights gained in the understanding of the underlying coupling physics are further used to develop general trace routing rules for minimizing radio frequency interference in the GPS band.

Modeling EMI Due to Display Signals in a TV

Modeling the electromagnetic emissions from a complex product such as a TV presents many challenges due to the complexity of electromagnetic interaction between multiple noise sources and interconnected resonant structures. A set of advanced methods such as the design and use of substitution boards for electromagnetic interference analysis, a practical simulation model for verifying the accuracy of the passive structures of the TV, an empirical scaling factor for incorporating the main processing board using the Huygens Equivalence theorem and modeling the radiation due to the flex cable based on active probe measurements is presented. The combined model comprised of the relevant noise sources and structures allowed the prediction of the most critical radiated emissions and the total radiated power caused due to the display signals.

Radiated EMI Estimation From DC–DC Converters With Attached Cables Based on Terminal Equivalent Circuit Modeling

An equivalent two terminal model based on the Thevenin equivalents describes the common mode (CM) currents on the input and output side of two widely used types of dc-to-dc power converters—buck and boost. Thus, it describes a nonlinear circuit by a linear equivalent circuit. The maximized spectrum of the CM currents is extracted for converters with stochastic signals using a novel characterization procedure. The extracted Thevenin model is used in co-simulation combined with a full-wave electromagnetic solver to predict the radiated emissions from the system consisting of the shielded dc–dc converters with attached cables and a DC brushless motor as load. The results using the terminal model agree well with the measurements providing that the actual CM loads are within the range of CM loads used while obtaining the Thevenin equivalent circuit.

A study on correlation between near-field EMI scan and ESD susceptibility of ICs

Correlation between near-field EMI scan and ESD susceptibility scan of a cellphone CPU IC is investigated. It is shown that the ESD susceptibility of the CPU IC depends on the activity of the IC. Based on the obtained correlation between these two scans, it is sufficient to perform the ESD susceptibility scan only by running the application which highly loads the CPU. This reduces the ESD susceptibility measurement time as well as the probability of physical damage to the IC.

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 amplifiers 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.

An ESD demonstrator system for evaluating the ESD risks of wearable devices

An ESD demonstrator system was designed to demonstrate the levels of transient fields that a wearable device can be subjected to. The system can detect pulses as short as 1–2 ns and was used to evaluate the fields associated with a brush-by discharge from a waist mounted device. The presence of a higher field level at the same voltage for a body worn device discharge indicates a higher risk for body worn devices compared to the HMM discharge specified by the IEC-61000-4-2 standard.