EMR Detection and Mitigation on the LSV2

Our goal is to investigate, develop, and improve EMR detection and mitigation techniques in order to assist the advancement of US Navy stealth technology.

Problem Definition
Problem Statement The US Navy Acoustic Research Detachment in Bayview, ID on the southern shores of Lake Pend Oreille, is experiencing electromagnetic interference(EMI) issues with their acoustic data collection. They have asked us to locate the sources of electromagnetic radiation(EMR) and to figure out how to mitigate these sources to reduce interference.

Design Goals and Deliverables Establish primary sources of EMI Measure radiation and plot electromagnetic spectrum Analyze and determine best mitigation techniques Create and test mitigation scheme in lab

Specifications Measurements Frequency: 25 kHz Time: 3 minutes Measurement Distance: 1 inch Design Goal Attenuate by 20dB at 11.6kHz

Project Learning
Summary

We researched electromagnetic wave interactions with materials, use of spectrum analyzer and antennas (loop and stub) to measure emissions, and industry and military standards for electromagnetic compatibility in order to provide the Navy ARD with a successful EMI mitigation solution. Details of our research include learning about various techniques for mitigation of both radiated and conducted emissions and the complexities that accompany these solutions. For more information, please refer to our Final Report, linked at the bottom of our Wiki.

Characterization of the Problem

The plots below show a clear correlation between the measured electromagnetic radiation and the acoustic measurements taken by the ARD on the LSV-2.

Equipment Photos of the inverter and electromagnetic spectrum analyzer provided to us by the US Navy ARD:

Test Setup

The Electrical Engineering department's power laboratory is capable of supplying the 320VDC - 440VDC required to power the inverter. Two induction motor / DC generator combination machines are connected in series to supply a total of 365VDC. Resistor banks, each section capable of safely drawing 2kW of power, are connected in parallel to draw 27A, applying a load of 79% of the full-load capability of the inverter. The inverter is connected through a panel in a separate room at the back of the laboratory. This isolates it from the generation environment, which provides a less electrically noisy environment in which to measure EMR.

Design
Process Flowcharts

Selection of Materials

Determination of Expected Attenuation

We used an absorbtion nomogram to determine the expected attenuation for MuMETAL and Conetic cable shielding foil. The expected values determined from this can be see in the table below:

Attenuation Results
We successfully attenuated the J6/J7 cable by nearly 50dB in some areas. For more details, please refer to our Final Report.

Document Archive
Minutes