Research Problem

     In Kenya, Communications Authority (CAK) regulates the telecommunocations sector through Licensing of businesses in the communications sector. Licensing includes frequency spectrum management (FSM), equipment type approval (TA) and continuous monitoring of Quality of Service (QoS) and competition. However, it is beyond the scope of the CA to monitor RF radiation levels in the community, especially those from numerous hand-held devices.
     It is therefore imperative to perform measurement of radiation activity to ascertain if the levels are within ’healthy’ bands as approved by World Health Organization (WHO) and International Telecommunications Union (ITU) e.g. at maximum, SAR := 2[W/kg]. This project will involve measurements of electric field intensity, E(V /m) from several center frequencies used in the communications industry.
     Furthermore, the effect of power levels on certain human body parts will be studied. In this regard, exposure to hand-held devices will be evaluated through the evaluation of proximity of use to the body. These effects are best studied through evaluation of specific absorption rate, SAR.
     Firstly, a well-known theoretical model of SAR will be used to introduce the topic to trainees. The depth to which radio waves penetrate exposed tissues depends on the frequency of the source, and the electrical properties of the tissue. The depth of penetration (skin depth, δ) is given as:

     ...[1.0]

where
     ƒ:  frequency of the source [Hz]
     μ:  magnetic permeability of tissue [H/m]
     σ:  conductivity of the medium [S/m]

Factors to Consider

• 1. Density of RF antennas: Urban, Rural, Metropolis, Educational centres
• 2. Frequency of use: 2G, 3G, 4G, 5G + , Wi-Fi, IoT at different 3GPP power classes [1-5]

SAR is defined from electric field intensity, E as:

     ...[1.1]

where
     W:  absorbed energy [J]
     m:  tissue mass [Kg]
     ρ:  tissue density [Kg/m^3]
     V:  potential difference [V]
     R:  resistance[Ω]
     σ:  Conductivity [S/m]
     A:  surface area [m^2]
     E:  electric field intensity [V/m]

The tissue power density is written as:

     ...[1.2]

and the intrinsic tissue impedance η is given as:

     ...[1.3]

where
     P_t:  transmitted power
     G_t:  gain at the transmitter

d is the distance from the antenna to the tissue including depth of penetration: i.e.

  d = (d_a + δ)      with d_a as distance in air     ...[1.4]

It is evident from [1.1] and [1.2] that if the tissue properties (μ_r, ε_r, σ, ρ) are known, the SAR can be computed for any center frequency.