Analyzing and mitigating the near-field radiations from PCB of GPS-based vehicle tracking system

Abstract

The EMI/electromagnetic compatibility (EMC) analysis is becoming very important in today's world of dense EMI environment. As we go toward accuracy and stability of any electronic product in dense EMI field, it is necessary to test it at printed circuit board (PCB) level. This paper describes the measurement technique of scanning of PCB using EMC Precision Scan Tool. The result of near-field measurement indicates the intensity of radiation of each component on PCB. This study is proposed to estimate the radiation field at component level. The near-field based techniques have been widely used in EMC studies because of the high accuracy and reliability. With appropriate model extraction and simulation tools, near-field scanning can be used to predict electromagnetic emissions. With proper shielding, the near-field radiations can be reduced. The near-field radiations can be used to predict far-field radiations from the system, before practically testing in EMI/EMC Laboratory or getting installed at end-user applications. Two models for global positioning system (GPS)-based vehicle tracking system used in research work have been proposed in this article. One is GPRS based and the other is SMS based, intended to be used in stringent environment and ground-based army vehicle. The near-field radiations have been taken at PCB level in dB µV for a range of 100 kHz-2.5 GHz frequency band. Maximum radiations of around 90-130 dB µV were found. The paper proposes Mu-metal and HE-30 shielding materials for mitigating low-and high-frequency radiations. The GPS VTS GPRS based board and GPS VTS SMS Tx board with HE-30 enclosures had been tested in national EMI Test Laboratory, Automotive Research Association of India (ARAI), for the frequency bands 100 KHz-2.5 GHz. The results had been compared with MIL-461E EMI/EMC standard, and had been found to be satisfactory. The low-frequency radiation level was found to be just within the acceptable limits as per the standard.