Ali Khoshniat

Date of Award


Document Type



Santa Clara : Santa Clara University, 2020.

Degree Name

Doctor of Philosophy (PhD)


Electrical Engineering

First Advisor

Ramesh Abhari


Unintentional radiated emission spikes are one of the causes of failure in electromagnetic compliance tests of high-speed systems. In this thesis, a new absorber solution for mitigating such emissions is proposed using the concept of metamaterial structures. The absorber is placed inside the high-speed system shield box to match the low (almost zero) impedance of the metal walls to the wave impedance of unwanted radiations. As a result, waves reflected from the shield box are attenuated which eventually reduces the emissions leaked outside of the box. The effectiveness of the proposed solution is demonstrated through simulations and experimental evaluations of emissions from a 2D patch antenna array board representing a PCIe Gen 3 interface. The metamaterial absorber is implemented with PCB fabrication technology using resistive thin film layers. Two in-house radiation measurement setups are designed for this research to show the correlation between full-wave simulation results and the measurement of the fabricated prototype. The designed absorber reduces the emissions by more than 5 dB in the worst-case scenario of radiation source excitation. This provides a low-cost remedy for a marginally failing system to pass the EMC test without any change to the system board.

For design and evaluation of the proposed metamaterial absorber solution, a clear methodology is presented in this thesis. The effects of the location of radiation sources, inter-component coupling, and shield box height on the design and performance of the proposed solution are investigated. In theoretical analysis, in addition to classical microwave cavity theory a new approach is employed by modeling the metamaterial absorber with a bulk material layer with complex permittivity and permeability. The bulk material design approach expedites theoretical evaluations and opens the door for further design explorations.