The Effects of Mounting a Metallic Cylinder behind a Ground-Plane-Version Electromagnetic Field Sensor

Abstract : A ground-plane-version electric and magnetic field sens ors are currently used to measure the electric and magnetic fields produced during a simulated high-altitude electromagnetic pulse (HEMP). Recently fabricated and mounted is a hollow metallic cylinder behind the sensor's ground plane to house a fiber-optic transmitter, amplifiers, and other equipment necessary for data collection. The presence of this metallic cylinder increases the amplitude of a signal measured with this new sensor structure geometry. The electric and magnetic field enhancements caused by the presence of this metallic cylinder were measured in both the frequency and time domains. The enhancement was also calculated numerically with the use of a three-dimensional finite-difference code. In the frequency domain, the enhancements for both the electric and magnetic fields were measured with the use of large transverse electromagnetic (TEM) cells. In the time domain, the enhancements were computed by comparing simulated HEMP fields measured with this sensor/cylinder to those measured with miniature electric and magnetic field sensors. The degree of enhancement of this sensor/cylinder will vary as a function of distance when the sensor/cylinder is placed next to a conducting object, such as a metallic shelter. These enhancements were also investigated with the use of miniature electric and magnetic field sensors.