Neha Kumar (Director, WILCOM Technologies Pvt. Ltd.) Prof. Girish Kumar (I.I.T Bombay) ISMOT- 2009
Radiation measurements near the cell towers EMF exposure Safety norms Review Biological effects (far below current standards) Radiation Shield (reduce Radiation levels)
Radiation emitted from Cell Phones, Cell phone towers, Wi-Fi, TV and FM towers, microwave ovens, etc are called Electromagnetic radiations and are known to cause significant biological effects on the human body and health of animals.
Cell Tower Statistics in India
4.25 lakhs 3.75 lakhs
Antennas on Cell tower transmit in the frequency range of: • 869 - 890 MHz (CDMA) • 935 - 960 MHz (GSM900) • 1805 – 1880 MHz (GSM1800) • 2110 – 2170 MHz (3G)*
Microwave radiation effects are classified as: •Thermal •Non-thermal The current exposure safety standards are mainly based on the thermal effects, which are inadequate.
EXPERIMENT: Radiation level measurements near
several Cell Tower sites
A broadband monopole antenna of gain = 2 dB was used to measure radiated power by various cell phone towers (CDMA, GSM900 and GSM1800)
Measured Power -20 to -30 dBm (in dBm) For each frequency bands
-30 to -50 dBm
Power Received Pr by an antenna at a distance R is given by:
Pt × Gt × Area λ Pr = = Pt × Gt × Gr × 2 4πR 4πR
For a transmitter power of Pt = 20 W, transmitting antenna gain of Gt = 10 dB, receiving monopole antenna of gain Gr = 2 dB, the received power at R = 50 m is: At 887 MHz, Pr = -10.2 dBm At 945 MHz, Pr = -10.8 dBm At 1872 MHz,Pr = -16.7 dBm
• Measured power is less than theoretically calculated power as the concrete wall provides some attenuation and also these buildings were not directly in the direction of maximum radiation of transmitting antenna. • A mobile phone requires