A Microcontroller Unit-Based Electromagnetic Bandgap Control Scheme: Application for Enhancing Isolation in an Antenna Array and the EMI Scanner System Speed Thereof

摘要

This article presents an adaptive electromagnetic bandgap (EBG) scheme based on a microcontroller unit (MCU) for reducing the mutual coupling in an antenna array designed for electromagnetic interference (EMI) scanner system enhancement (e.g., scanning speed, lower weight and size, and maintenance). For the first time, the EBG is configured via an MCU to enable the finest control of the equivalent lumped elements of the EBG, realizing optimal isolation between/among the antennas at very close distances (1.2 mm = 0.05 lambda at 10 GHz), which typically translates into longer distances between/among the antennas and/or more EBG elements (examples are referenced for comparison). The desired optimal isolation performance is realized by the EBG scheme combined with varactor diodes under the control of the MCU (later the microcontrolled EBG or MC-EBG) referencing a database compiled from the simulation results. In a simulation, the optimal isolation was found to be -58 dB ( S21) between two small-loop antennas (later the 2-SLA prototype) on a high-permittivity substrate ( epsilon r = 12.8, 4-mm thick). For the 4-SLA prototype devised here under identical substrate conditions, the optimal isolation points were found to be -30 dB ( S21/ S31) and -38 dB (S41). During the measurements, when compared under a EBG-standalone tuned isolation at 10 GHz, the measured isolation of the ultimately selected 4-SLA prototype was found to be better by more than 29 dB (-7 to -36 dB) between the closest SLAs ( S21/ S31) and by more than 35 dB (-18 to -53 dB) between the farthest SLAs (S41) at the same frequency. The accordant S-parametric results from both the simulation and the measurement are supported by the simulated H-field distribution (dBmA/m). The H-field from one SLA to the others was found to be reduced by more than 30 dB with the MC-EBG activated (MCU ON), and this is compared with the value of 13 dB from the tuned EBG-standalone case (MCU OFF). The final 4-SLA prototype was deployed in an actual 1 mm over-the-air (OTA) near-field EMI test at 10 GHz. The final field application results prove an enhancement in the EMI scanning speed (few hours versus few minutes) with a very low error rate ( clear EMI detection), with the ultimate goal of the MC-EBG thus successfully accomplished.