Transfer function measurements and low power microwave susceptibility tests of a complex communication network

We report on microwave vulnerability tests of a configurable network communication system. The purpose of the measurements at Fraunhofer INT was twofold. First, transfer functions were determined in order to characterize the coupling of microwave fields into the equipment under test (EUT) including the investigation of shielding effectiveness of different boxes containing the network equipment. Second, susceptibility tests were performed at our facility for lower field levels. The INT test facility consists of a waveguide built as an open pyramidal asymmetric three-plate TEM transmission line which is located within a shielded hall. Inside the waveguide homogeneous microwave fields can be realized in a maximum test volume of approximately 2 x 2 x 3 m3. Transfer function measurements can be carried out by continuous wave (CW) illumination of the EUT using digital tunable sweep generators together with power amplifiers for frequencies between 1 and 8000 MHz and vector network analyzers as receivers. Susceptibility tests can be done with a pulse modulated generator in the frequency range from 150 to 3425 MHz for different pulse widths and repetition rates. The investigations focused on the vulnerability of the network components (commercial HUBs, switches, and routers) including media converters and uninterruptible power supply (UPS) units but not connected PCs and other peripherals as monitors or keyboards. To this end, several subsystems were set up and network traffic was generated involving the relevant network components. In order to detect malfunctions due to microwave illumination the traffic was monitored with network diagnostics software. In addition, the functioning of the components of interest was observed directly by watching the system LEDs with cameras. The setup also included different cabling ranging from fiber optic via SFTP (shielded) to UTP (unshielded) connections. Particularly the influence of the unshielded cables was tested in two different configurations