Product Info

Report No: CCISE191202301-V01
Shenzhen Zhongjian Nanfang Testing Co., Ltd. Project No.: CCISE1912023
No. B-C, 1/F., Building 2, Laodong No.2 Industrial Park, Xixiang Road,
Bao’an District, Shenzhen, Guangdong, China
Telephone: [phone] Fax: [phone], E-mail: [e-mail] Page 9 of 171
6 Introduction
6.1 Introduction
SAR is related to the rate at which energy is absorbed per unit mass in an object exposed to a radio field. The
SAR distribution in a biological body is complicated and is usually carried out by experimental techniques or
numerical modeling. The standard recommends limits for two tiers of groups, occupational/controlled and
general population/uncontrolled, based on a person’s awareness and ability to exercise control over his or her
exposure. In general, occupational/controlled exposure limits are higher than the limits for general
population/uncontrolled.
6.2 SAR Definition
The SAR definition is the time derivative (rate) of the incremental energy (dW) absorbed by (dissipated in) an
incremental mass (dm) contained in a volume element (dv) of a given density (ρ). The equation description is as
below:
SAR
dt
d






dm
dU









dv
dU
dt
d

SAR is expressed in units of Watts per kilogram (W/kg)
SAR measurement can be either related to the temperature elevation in tissue by
SAR
C






t
T


Where: C is the specific heat capacity,
T 
is the temperature rise and
t 
is the exposure duration, or related to
the electrical field in the tissue by
SAR


2
E
Where: σ is the conductivity of the tissue, ρ is the mass density of the tissue and E is the RMS electrical field
strength. However for evaluating SAR of low power transmitter, electrical field measurement is typically applied.