Specific absorption rate - AbsoluteAstronomy.com

Specific absorption rate (SAR) is a measure of the rate at which energy

Energy

In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

is absorbed

Absorption (electromagnetic radiation)

In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed to other forms of energy for example, to heat. The absorption of light during wave propagation is...

by the body when exposed to a radio frequency

Radio frequency

Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

(RF) electromagnetic field

Electromagnetic field

An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...

; although, it can also refer to absorption of other forms of energy by tissue, including ultrasound . It is defined as the power

Power (physics)

In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

absorbed per mass

Mass

Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

of tissue and has units of watt

Watt

The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

s per kilogram

Kilogram

The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

(W/kg). SAR is usually averaged either over the whole body, or over a small sample volume (typically 1 g or 10 g of tissue). The value cited is then the maximum level measured in the body part studied over the stated volume or mass.

Calculation

SAR can be calculated from the electric field

Electric field

In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

within the tissue as:

where

is the sample electrical conductivity

is the RMS

Root mean square

In mathematics, the root mean square , also known as the quadratic mean, is a statistical measure of the magnitude of a varying quantity. It is especially useful when variates are positive and negative, e.g., sinusoids...

electric field

is the sample density

Density

The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

SAR measures exposure to fields between 100 kHz and 10 GHz. It is commonly used to measure power absorbed from mobile phones and during MRI scans. The value will depend heavily on the geometry of the part of the body that is exposed to the RF energy, and on the exact location and geometry of the RF source. Thus tests must be made with each specific source, such as a mobile phone model, and at the intended position of use. For example, when measuring the SAR due to a mobile phone the phone is placed at the head in a talk position. The SAR value is then measured at the location that has the highest absorption rate in the entire head, which in the case of a mobile phone is often as close to the phone's antenna as possible. Various governments have defined safety limits for exposure to RF energy produced by mobile devices that mainly exposes the head or a limb for the RF energy:

United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

: the FCC
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...

requires that phones sold have a SAR level at or below 1.6 watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

s per kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

(W/kg) taken over a volume containing a mass of 1 gram of tissue.
European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

: CENELEC specify SAR limits within the EU, following IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...

standards. For mobile phones, and other such hand-held devices, the SAR limit is 2 W/kg averaged over 10 g of tissue (IEC 62209-1). For Magnetic Resonance Imaging the limits (described in IEC 60601-2-33) are slightly more complicated:

Averaging time	6 minutes
	Whole body SAR	Partial body SAR	Head SAR	Local SAR
Body Region	whole body	exposed body part	head	head	trunk	extremities
Operating Mode ↓	(W/kg)	(W/kg)	(W/kg)	(W/kg)	(W/kg)	(W/kg)
Normal	2	2 - 10 (b)	3.2	10 (c)	10	20
1st Level Controlled	4	4 - 10 (b)	3.2	10 (c)	10	20
2nd Level Controlled	>4	>(4 - 10) (b)	>3.2	>10 (c)	>10	>20
Short term SAR	The SAR limit over any 10 s period shall not exceed three times the stated values

Notes:

(a) Local SAR is determined over a mass of 10 g.

(b) The limit scales dynamically with the ratio "exposed patient mass / patient mass":

NORMAL OPERATING MODE: Partial body SAR = 10 W/kg – (8 W/kg * exposed patient mass / patient mass)

FIRST LEVEL CONTROLLED OPERATING MODE: Partial body SAR = 10 W/kg – (6 W/kg * exposed patient mass / patient mass)

(c) In cases where the orbit is in the field of a small local RF transmit coil, care should be taken to ensure that the temperature rise is limited to 1 °C.

For whole body exposure there is a limit of 0.08 W/kg averaged over the whole body.

Mobile-phones SAR list

Brand	Model	Operating system	SAR (W/kg)
LG	Optimus 2X LG Optimus 2X The LG Optimus 2X is a smartphone designed and manufactured by LG Electronics. The Optimus 2X is the world's first smartphone with a dual-core processor and third phone in the LG Optimus-Android series. LG debuted the Optimus 2X on December 16, 2010 and the device first became available to...	Android	0.545
Samsung	Nexus S Nexus S The Nexus S is a smartphone co-developed by Google and Samsung and manufactured by Samsung Electronics. It was the first smartphone to use the Android 2.3 "Gingerbread" operating system, and the first Android device to support Near Field Communication in both hardware and software...	Android	0.58
HTC	Nexus One Nexus One The Nexus One was Google's flagship smartphone manufactured by Taiwan's HTC Corporation. It became available on January 5, 2010 and uses the Android open source mobile operating system...	Android	0.37
HTC	Wildfire HTC Wildfire The HTC Wildfire is a smartphone developed by the HTC Corporation, that was announced on 17 May 2010 and released in Europe in June of the same year. It is powered by a 528 MHz Qualcomm processor and runs the Android operating system, version 2.2. It includes an TFT LCD capacitive touchscreen...	Android	0.754
BlackBerry	Torch BlackBerry Torch 9800 The BlackBerry Torch 9800 is a 2010 model in the BlackBerry line of smartphones. It combines a physical QWERTY keyboard with a sliding multi-touch screen display and runs on BlackBerry OS 6...	BlackBerry OS 6.0	0.91
BlackBerry	Curve 8320	BlackBerry OS 6.0	0.64
BlackBerry	Curve 8310	BlackBerry OS 6.0	0.72
BlackBerry	Curve 8520	BlackBerry OS 6.0	0.57
BlackBerry	Curve 8900	BlackBerry OS 6.0	0.63
BlackBerry	Curve 9300	BlackBerry OS 6.0	1.07
BlackBerry	Curve 9330	BlackBerry OS 6.0	0.96
HTC	Surround HTC 7 Surround The HTC 7 Surround is a smartphone created by HTC running on the Windows Phone operating system. The HTC Surround launched on November 8, 2010 on AT&T.- Release :The Surround was released on November 8, 2010...	Windows Phone 7	0.439
Motorola	Flipside	Android	0.5
Samsung	Blue Earth		0.196
Samsung	Acclaim		0.29
Huawei	Ideos X5	Android	0.34
LG	Quantum LG Quantum The LG Quantum or Optimus 7Q is a slider smartphone which runs Microsoft's Windows Phone operating system. The LG Quantum was launched November 8, 2010 on AT&T.- Display :...	Windows Phone 7	0.35
Samsung	Haven		0.41
Samsung	Evergreen		0.41
Samsung	Captivate	Android	0.42
Samsung	Smiley		0.43
Doro	PhoneEasy 410		0.445
Motorola	Devour Motorola Devour The Motorola Devour is an Internet and multimedia enabled smartphone designed by Motorola, which runs Google's Android operating system. In the United States, the handset is distributed exclusively by Verizon Wireless. The Devour has a Hearing Aid Compatibility rating of M4/T4...	Android 1.6	0.45
Motorola	i890		0.45
Kyocera	Neo E1100		0.479
Samsung	Contour		0.49
HTC	Imagio		0.498
Samsung	Flight SGH-A797		0.505
Samsung	SGH-T249		0.51
Samsung	Rugby II SGH-A847(AT&T)		0.52
Nokia	E5	Symbian	0.88
HTC	EVO		1.03
Apple	iPhone 4 IPhone 4 The iPhone 4 is a touchscreen slate smartphone developed by Apple Inc. It is the fourth generation iPhone, and successor to the iPhone 3GS. It is particularly marketed for video calling , consumption of media such as books and periodicals, movies, music, and games, and for general web and e-mail...		1.17
Motorola	Bravo		1.59
Motorola	Droid 2 Global	Android	1.58
Sony Ericsson	Satio (Idou)		1.56
Sony Ericsson	Xperia X10 Mini Pro	Android 2.1	1.55
Sony Ericsson	Xperia Active	Android 2.3.4	0.86 http://dl-www.sonyericsson.com/cws/download/1/103/283/6/1316759943/ST170_SAR_ROW_i_version.pdf
Sony Ericsson	Spiro		1.03
Sony Ericsson	Naite		1.22
Kyocera Jax	S1300		1.55
Motorola	i335		1.53
Motorola	Defy Motorola DEFY The Motorola Defy is an Android-based smartphone from Motorola. The Defy is marketed as water-resistant, dust-resistant, impact- and scratch-resistant by merit of its port covers and Gorilla Glass screen...	Android	1.52
Motorola	Grasp		1.52
ZTE	Salute		1.52
ZTE	Bade aka sanfransisco		1.35
LG	Rumor 2		1.51
Motorola	Droid Motorola Droid The Motorola Droid is an Internet and multimedia enabled smartphone designed by Motorola, which runs Google's Android operating system. The Droid had been publicized under the codenames Sholes and Tao and the model number A855...	Android	1.49
Sanyo	Vero		1.49
Motorola	Droid 2 Motorola Droid 2 The Motorola Droid 2 is the fifth phone in Verizon's Droid line. In the U.S., it is available exclusively on Verizon Wireless, and was released August 12, 2010 . It runs the Android operating system by Google, and can run Flash Player 10.1...	Android	1.49
HTC	Desire HTC Desire The HTC Desire is a smartphone developed by the HTC Corporation, announced on 16 February 2010 and released in Europe and Australia in the second quarter of the same year. The HTC Desire runs the Android operating system, version 2.2 "Froyo"...	Android	1.48
LG	Chocolate Touch		1.47
Kyocera	Wild Card M1000		1.46
Kyocera	X-tc		1.45
Motorola	i576		1.45
Motorola	Stature i9		1.44
Motorola	Droid X Motorola Droid X The Motorola Droid X is a smartphone manufactured by Motorola Mobility, Inc. that runs the Android 2.3 software; the version of the hardware released in Mexico is called the Motorola Motoroi X. The Droid X has been distributed since July, 2010 by Verizon Wireless in the United States and Iusacell...	Android	1.43
Samsung	Galaxy S2	Android 2.3	0.338
Nokia	3310		0.99
HTC	Titan HTC Titan The HTC Titan is an EVDO Rev. A Windows Mobile 6.1 Pocket PC phone manufactured by High Tech Computer Corporation of Taiwan. It is the successor to the HTC Apache upon which it improves by adding more ROM, GPS, EVDO Rev. A, additional hard keys, a scroll-wheel, spring-loaded keyboard, and a higher...	Windows Phone 7.5	0.3
HTC	HD7 HTC HD7 The HTC HD7 , is a smartphone running the Windows Phone OS operating system. The phone was designed and manufactured by HTC...	Windows Phone 7	1.15

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Calculation

Mobile-phones SAR list

See also

External links