Q2; The natural unit of SAR is W/kg however the solver will evaluate the SAR over much smaller volumes/masses than a kg. That depends on the segmentation of your problem in CST. Typically you might find that the SAR value is calculated for a cubic volume with less than a 10mm side length and a mass of less than 1gramme. A power of 10mW deposited into a 1 gramme sample is an SAR of 10W/kg. You should check your model carefully. Don't just accept the answers. Tools like CST are very sophisticated and you must know what you are doing and understand all the default settings.

The SAR is often averaged over 6 minutes, so an average power is taken - but check the safety standards of your own country, or the country of the target market.

A small antenna close to the  body can easily put a lot of power into a small volume of flesh, as the previous answer says, unless there is a conducting shield underneath.  The shield needs to be big enough that the currents at the edge are small, otherwise the edge of the shield will radiate into the body, and also affect the impedance of the antenna.

If you have done practical work with microwaves you will know that fingers can make very good loads!  The top half of a fingertip is about 1 gram and so 10 mw into a fingertip is about 10 W/kg.  Because it can be averaged over 6 minutes in the UK it is ok to use fingers to poke into microwave parts as temporary loads during testing with standard test equipment power of 100 mW or less.

Dear Naveed,  Though not always true, they are simple to manufacture, easy to analyze, their performance is well predicted. However, there exists many more advantageous types depending on the application under consideration. Best regards

Microwave patch antennas are also used on the body, and have the advantage that they are low-profile.  The spacing between the antenna and the ground has to be well controlled, which requires good design if it is to be light and flexible to wear.

Monopole antenna is easier to excite certain EM waves without radiation?? If it is true, then i doubt it has anything to do with the ground.

Well, it really depends on what wearables you are talking about.

We don't need a ground to transfer EM waves. That is a fact.

A monopole antenna needs a ground to operate over, otherwise it is not a monopole, but a dipole or some other pole.  The ground does not need to be very big but does need to be big enough so that the monopole can 'see' a satisfactory reflection of itself, which in practice usually means that the currents at the edge of the ground need to be small.

first of all thanks to sir Marvin,i understand ur explanation

thank u sir malcolm but i need some explanation of time with SAR with some methamatical relation,thank u so much

thanks to sir Hussain and Louis for reply

For how much time we can place an antenna near human body,relation with respect to time

ok my sar=1.2W/kg for 10 gram tissues

so for how much time i can place an antenna near the body???

needs ur reply

EC Council Recommendation of 12th July 1999 on the limitation to exposure of the general public to electromagnetic fields (0Hz to 300 GHz) 1999-519-EC states that from 10 MHz to 10 GHz the SAR averaged over the whole body shall be no more than 0.08 W/kg (80 mW/g).  This is to be the average value over 6 minutes.  To get the average value you integrate the SAR for 360 seconds and then divide by 360.

The SAR limit for parts of the head and trunk is 2 W/kg, averaged over 10 g of contiguous tissue, and for parts of limbs it is 4 W/kg, also averaged over 10 g of contiguous tissue.  These are both averaged over 6 minutes.

SAR is the major criteria.

thank u so much for sharing ur information

monopole antenna is chosen because this type of antenna is polarized normally to the body surface and therefore it preserves a strong ray diffracted around it.

thanks

Monopole antenna naturally having null steering in the pattern of radiation, while bending or disturbing the monople antenna, its null defects and main beam is same. thats why most of the peoples prefers these type of antenna