EMI Coupling Paths and Mitigation in a Board-to-Board Connector

Abstract

Cage connectors for optical subassembly I/O modules have been identified as one of the main coupling paths in an optical link at the front-end of switches and routers. In the study presented herein, the simulation model used to study electromagnetic interference coupling physics and mitigation of the optical cage connector was corroborated by comparing the measured and simulated results for the total radiated power (TRP). Currents on the adjacent ground references to the differential signal conductors caused half-wave resonant peaks in the TRP response in the frequency range of 4-18 GHz. At frequencies from 18 to 28 GHz, both full-wave simulation and analytical formulas indicate that the radiation results primarily from the currents on the signal traces. The radiation from the optical cage connector was suppressed with absorbing materials, and the coupling path was verified, together with the optical cage and module enclosure.Index Terms-Absorbing material, electromagnetic interference (EMI) coupling path, high frequency, mitigation, optical cage connector, radiation mechanism, total radiated power (TRP).

High-Frequency Electromagnetic Interference Diagnostics

“…The electrical-to-optical (and vice versa) interface assembly converts the electrical signal into an optical signal, which is subsequently transferred to other devices through an optical fiber cable. The cage connector, the optical transceiver module, and the optical cable ferrule were identified as the primary radiation contributors [3,4]. The aluminum ferrule surrounding the optical fiber cable forms a radiating antenna that is causing the most EMI problems in meeting regulatory requirements for optical transceiver modules.…”

“…The EMI coupling paths in the optical transceiver module can be concluded as follows. The cage connector [4], the connector between the transceiver circuit board and the flex cables, and the flex cables are the dominant radiation sources [1]. Table 2.…”

“…First, the interior EMI coupling paths and possible mitigation methods of optical modules are studied [1][2][3][4][5][6]. The internal mechanism can be analyzed to alleviate the radiation problem at the design stage or propose mitigation solutions.…”

Reduction of PCB PDN Impedance and Radiated Emissions Using a Hybrid Technique With Absorbing Materials and Decoupling Capacitors

“…We benchmark how effective absorbing material is by itself and then combine high frequency decoupling capacitor models. The characteristics of the de-cap model used in our study is derived from MURATA's Monolithic Ceramic Capacitor (MLCC) product catalog [39]. We present two different cavity models: (1), a simple power-ground PCB cavity plane model and (2), a relatively complex model that includes multiple P/G-vias connected to two pairs of power-ground planes.…”

“…Some of the areas include the defense industry, in traditional microwave component designs, and in conventional EMC/EMI test and control environments [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Recently, novel applications of microwave absorbing materials in computer system designs have been investigated [34][35][36][37][38][39][40].…”