Electromagnetic compatibility (EMC) is influenced by the environment, location, and behavior of medical devices and other non-medical devices.
Electromagnetic compatibility (EMC) of medical devices is influenced by the operational environment, the spatial location (e.g proximity to other electrical/electronic devices), and the design robustness. Several publications [1], [2], and [3] provide measurements of electromagnetic (EM) fields obtained in hospital environment, demonstrating the environmental effect on the medical devices , indicating a need for a the risk-based EM approach as compared to the current rule-based method. In the case of hospital rooms acting as semi-reverberant environment [4] and [5], multipath coupling of EM disturbances to medical devices should also be considered.
The latest EMC Guide [6] and the 4th edition of IEC 60601-1-2 [7] suggest a risk-based approach rather than the traditional rule-based approach. The well-known approach of EM risk management consists of four steps :
- EM risk analysis;
- EM risk evaluation;
- EM risk control;
- EM risk verification and validation.
The knowledge of victim’s operational EM environment is one of the requirements for performing risk management . Measurements done to identify the reflecting and absorbing elements present in a known environment is shown for example, in the Fig.1.
Fig. 1. Long exposure photo of the electromagnetic field in an anechoic chamber.
Fig. 2. Long exposure photo of the electromagnetic field inside a building or hospital.
The color map shown in Fig.2 indicates the received power. We can see that in free space there is an exponential decrease in the EM field intensity as the receiver is moved away from the source. We noticed major changes in the long exposure shot of the received signal strength indicator (RSSI) device inside a lab, containing furniture and metal objects. Due to reflections many waves reverberating within this room causes the creation of hotter and colder spots [8].This measurement shows that the EM distribution in the hospital is different from free space due to the reflections. The modification of the field in a reverberant environment might cause an unforeseen increase of the effective field strength with respect to the free space laboratory conditions, coupled onto the victim devices.
Their behavior is also extremely critical when it comes to environmental factors. The majority of wireless communication equipment do not transmit signals simultaneously. The field distribution is affected by the location of antennas and undesired sources, especially in a semi-reverberant environment, by stimulating its various modes. The distance between the transmitter and the victim influences the field intensity along the line of sight.
So, before adopting the risk-based EM approach, we must first comprehend human behavior, source mobility, victim location, and possible number of EMI sources, among other things.
References
[1] characterization of electromagnetic propagation of a hospital from 55-1950MHz,” 2010 Asia-Pacific Symp. Electromagn. Compat. APEMC 2010, pp. 826–829, 2010,[2] C. Kurnaz and T. Aygun, “Characterization of Indoor and Outdoor Electric Field Strength Levels at Hospitals,” 2018 26th Telecommun. Forum, TELFOR 2018 – Proc., pp. 1–4, 2018,
[3] H. Alnamir, “Study of Low Frequency Electromagnetic Interference Problems in Hospital Environment,” 2019 11th Int. Symp. Adv. Top. Electr. Eng. ATEE 2019, pp. 1–5, 2019,
[4] R. Vogt-Ardatjew, U. Lundgren, S. F. Romero, and F. Leferink, “OnSite Radiated Emissions Measurements in Semireverberant Environments,” IEEE Trans. Electromagn. Compat., vol. 59, no. 3, pp. 770–778, 2017,
[5] R. Vogt-ardatjew, Electromagnetic fields in reverberant environments. 2017.
[6] “March 2018 Guide for the EMCD ( Directive 2014 / 30 / EU ),” no. March, pp. 1–67, 2018.
[7] C. Standard, “NEN-EN-IEC 60601-1-2,” 201
[8] M. Das, R. Vogt-Ardatjew, B. van den Berg and F. Leferink, “Risk-based EMC Approach in Hospital Environment,” 2020 IEEE International Symposium on Electromagnetic Compatibility & Signal/Power Integrity (EMCSI), 2020, pp. 676-680,
About the Author: Mumpy Das
Mumpy Das did her Master’s in the year 2019 from Korea Advanced Institute of science and technology in Division of Future Vehicle(EE). Her research journey so far has served as a tremendous boost in realizing her intense passion for EMI and EMC.
