ITU-T Workshop Human Exposure to Electromagnetic Fields (EMFs) An Innovative EMF Safety Concept for Workers Near of Mobile Base Station Antennas Klemens Martin, T-Mobile Deutschland GmbH
The EU Workers Directive (2004/40/EC) Directive 2004/40/EC refers to the minimum health and safety requirements with regard to the exposure of workers to physical agents (EMF). Action Values Exposure Limits f (MHz) 110-400 400-2000 2000 300 GHz E (V(m) 61 3f^0.5 0.008f^0. 0.01f^0.5 5 137 H (A/m) 0.16 0.36 B (µt) 0.2 0.45 S (W/m 2 ) 10 f/40 50 f (MHz) 10 MHz 10 GHz 10 GHz 300 GHz SAR whole body (W/kg) SAR Head and trunc (W/kg) SAR limbs (W/kg) S (W/m 2 ) 0.4-10 - 20 - - 50 Mobile phone frequencies: Limit values are in accordance with the ICNIRPguidelines.
The EU Workers Directive (2004/40/EC) action values exposure limits advantages relative simple estimation complex estimation costs disadvantages overestimation of exposure real estimation of exposure
The EU Workers Directive (2004/40/EC) Typical GSM-Site with 4 channels, 10 Watt, 3 sectors. The use of action values (E-/H-values) for workers will result in a characteristic safety distance between 1-4 meters. Problems: 1. Complex estimation due to the fact that the distance is usually in the near field region of the antenna (2 8 m) and thereby different measurements of E- and H-field or complex calculation with specific antenna parameters are needed. 2. The distances calculated on the basis of the action values are often too large for operational purposes. -> in practice base stations has to be switched of! 3. Overestimation of distances by the use of action values.
The EU Workers Directive (2004/40/EC) Solution: Use of the exposure limits (SAR-values). Advantages: smaller distances for workers (10 cm 1,5 m). Disadvantages: Complex estimation (numerical simulation, no measurement on the sites possible). Depending on antenna types. German Approach: German network operators choosed the use of the exposure limits due to the relative simple practicability and the small safety distances.
SAR Estimation on BTS Antennas Results of Projects (1) 1. study: Numerical estimation and measurement of whole- and partial-body SAR values in front of the BTS-antenna [Cooper et al., 2002] 2. study: Measurement of whole- and partial-body SAR values in front of a BTSantenna [Bahr et al., 1999]
SAR Estimation on BTS Antennas Results of Projects (2) 3. study: Numerical Estimation of SAR-Values in Human Model Caused by Base Station Antennas Goal: SAR-based safety distances for workers, one solution for all Networkoperators (partial reached) Vodafone T-Mobile O2 UMTS and GSM900/GSM 1800 Antennas Whole Body und Partial Body-Values [Bitz et al. 2005]
SAR Estimation on BTS Antennas Results of Projects (3) E-field SAR Calculated SAR distribution in the human body [Bitz et al. 2005]
SAR Estimation on BTS Antennas Results of Projects (4) [Bitz et al. 2005]
Safety Distances of BTS-Antennas Summary of Observed Studies Input power (Watt) Distance Geneva, (meters) 20 November 2007
SAR Estimation on BTS Antennas Ongoing FGF Study Numerical Body Dosimetry in Complex Field Distributions (IT IS Foundation, Prof. Kuster) Different BTS-antennas 300 MHz 3 GHz Different human models Dependencies of generic antenna parameters Start: October 2006, End: July 2007, Publication: Nov 2007
SAR Estimation on BTS Antennas Further Studies 1. Van Wyk, M.J., Bingle, M., Meyer, F.J.: Antenna modelling considerations for accurate SAR calculations in human phantoms in close proximity to GSM cellular base station antennas. Bioelectromagnetics, Vol. 26, No. 6, pp. 502 509, 2005. 2. Nordström, E.: Calculation of specific absorption rate (SAR) for typical WCDMA base station antennas at 2140 MHz. Master of Science thesis at Department of Physics and Measurement Technology, Biology and Chemistry, Linköping Institute of Technology, Sweden, 2004. 3. Catarinucci, L., Palazzari, P., Tarricone, L.: Human exposure to the near field of radiobase antennas a full-wave solution using parallel FDTD. IEEE Trans. MTT, Vol. 51, No. 3, 2003. 4. Menzel, K.: Exposition im Nahfeld von Mobilfunkbasisstationen: Einfache Überprüfung von Basisgrenzwerten bei Stationsantennen, In: Strahlenschutzpraxis, ISSN 0947-434X, TÜV-Verlag, 7. Jahrgang, Heft. 2, S. 12-16, 2001 5. Bahr, A., D. Gerhardt, K. Menzel: Arbeitsschutz im Nahbereich sendender Mobilfunkantennen. In: Nichtionisierende Strahlung: mit ihr leben in Arbeit und Umwelt, 31. Jahrestagung des Fachverbandes für Strahlenschutz e.v., Köln, 27.09.-01.10.1999, ITU-T Workshop TÜV-Verlag, Human Köln, exposure ISSN to electromagnetic 1013-4506, fields ISBN (EMFs) 3-8249-0559-0, 1999, S. 893-906.
German Approach Innovative EMF Safety Concept (1) Agreement of the German network operators SAR-based method is an approved method Result: Distance table r =f(power) at the antenna feeding point Building of 2 antenna classes (>= 60, < 60 horizontal opening angle): Distance 50 cm 100 cm 150 cm 200 cm H-Angle >= 60 70 W 120 W 180 W 250 W H-Angle < 60 40 W 60 W 80 W 100 W In practice, an additional safety factor of 2 is required. The specific details of the implementation is in the responsibility of the network operator.
German Approach Innovative EMF Safety Concept (2) Details: (top-view) Draufsicht (side-view) Seitenansicht (top-view) Draufsicht (side-view) Seitenansicht R/2 R/2 R R/2 R R R Träger R/2 (mast) Hauptstrahlrichtung (mast) Träger R/2 Träger (mast) R/2 (main radiation direction)
German Approach Innovative EMF Safety Concept (3) Labeling of each antenna with regard to the individual safety distances by a defined label. (safety distances) (front) (above, below) (right, left) (behind)
ITU-T Workshop Human Exposure to Electromagnetic Fields (EMFs) Thank you for your attention! For futher information please contact me: Klemens Martin T-Mobile Deutschland GmbH Klemens.martin@t-mobile.de