Modeling and Analysis of a New Packaging Structure for Noise Isolation in Mixed- Signal Systems

The integration of heterogeneous components/sub-systems (e.g., RF, high-speed digital, MEMS…) on the same chip, package or board requires the use of efficient noise isolation/suppression structures or techniques to minimize electromagnetic interference (EMI). So far, electromagnetic band gap (EBG) structures have been considered to be the most effective means to suppress noise coupling and prevent EMI over a wide range of frequencies. However, EBGs reduce the integration density because they consist of many periodically arranged patches, vias, and at times, surface mount components (capacitors and/or inductors) which consume much of the board space. EBGs also cause return-path discontinuity (RPD) problems for signal lines routed above/below one of their patterned layers, thus resulting in signal integrity (SI) issues. Therefore, in this paper, we propose a new packaging structure for noise isolation – the interconnected patch ring (IPR) structure. It is just as effective as EBGs in noise suppression/isolation, but overcomes most of the limitations of EBGs and other conventional noise isolation structures. To illustrate some of its advantages, we modeled and simulated the IPR structure to suppress the propagation of noise from 700 MHz to 2.5 GHz – the frequency range used by many wireless communication standards (e.g., GSM 900/1800, Bluetooth, UMTS and 2.4 GHz WLAN). Test samples of the IPR were designed, fabricated and measured. The measurement results showed good isolation throughout the required frequency range (Proof of Concept). Furthermore, a very good correlation was obtained between measurement and simulation, thus experimentally validating the simulation results.