Mobile phones are tested to ensure compliance with the SAR limit for the countries into which the phones are sold. Although the SAR is determined at the highest certified power level in laboratory conditions, the actual SAR level of the phone while operating can be well below this value. This is because mobile phones use adaptive power control to reduce the transmitted power to the minimum possible whilst maintaining good call quality.
Once a call is established the mobile phone will power down to the minimum level required. Therefore, the closer you are to a base station and the better the reception, the lower the actual SAR level. Does SAR vary between mobile phones? The maximum SAR level for different mobile phone models can vary and this is primarily due to where the antenna in the phone is located. Variations in SAR do not mean that there are variations in safety.
While there may be differences in SAR levels among phone models, all mobile phones must meet RF exposure guidelines. SAR levels can also vary considerably when in use depending on how good the reception is. Once a call is established the mobile phone will power down to the minimum level required to reach the network and maintain a quality call.
Specialised laboratory test equipment is used for conducting SAR measurements. The phantom is filled with a liquid that represents the electrical properties of human tissue. Mobile phones generally get better reception when used away from the main part of the body. The minimum separation often represents the spacing created by a phone holder or clothing. If a minimum separation is specified, the SAR test against the body will be conducted at that distance.
This is because the antenna in the phone is designed to be far enough away from the head to meet SAR requirements and operate most efficiently. What if i use my mobile in my pocket forgetting the minimum separation listed in the user guide? Clothing and mobile phone covers often provide a separation, however it is important to always check the user guide for the minimum requirements.
For example, a cheek position, where a mobile phone is placed under the phantom in the way that the middle part of the acoustic output touches the center of ear and cheek at the same time. Or tilt position, where the angle is increased by 15 degrees from the cheek position. These positions are tested for left and right sides of the head. Also, other positions are for example front side, back side, top side and bottom side of the device towards the phantom.
Because we hold the phone in the pockets, SAR body test measurements are required. A big portion of the measurements provided by Verkotan are body measurements. Body testing is typically done with a 5mm distance between mobile phones and phantom. Also, some countries for example France requires limb measurements, the maximum SAR limit for limb is 4.
One interesting point is that if multiple radio signals are transmitted from one device at the same time, SAR measures of the signals are summed. This combined output still needs to meet the required SAR limit of 1. The mobile phone uses a certain frequency bands that contain many frequencies where the mobile phone can communicate. International standards require SAR testing for the high, center, and low frequencies for the bands that the mobile phone works for.
When SAR measurements are performed, the results are compared to the requirements. Finally, the test report is issued based on the measurements made. The information included in the test report differs depending on the geographical location of the place where the product is to be sold.
When the testing is done, Verkotan provides a test report. The test report includes:. The declaration of conformance is also provided in the test report. This means that the results pass requirements. The whole process in a nutshell:. Operators have started to deploy 5G networks and more devices, which support 5G, are entering the markets. FR2 operates at millimetre-wave frequencies, — MHz, providing even faster and larger capacity data transmissions than FR1.
Its downside is shorter wavelength, which causes larger over-the-air signal attenuation. NSA mode allows operators to deploy 5G networks earlier as in addition to 5G base stations it utilizes existing 4G core network and base stations. This is useful especially for portable devices when the user moves away from 5G coverage area, the connection is handed over for 4G or other available cellular network technology to maintain the connection.
Base station simulators are used to connect the device under test to the 5G test network. Devices can support 5G in addition to all previous generations of mobile networks, increasing the total amount of testing required. The required amount of SAR testing is higher especially for 5G NSA mode where both 4G and 5G carriers need to be measured separately and then the simultaneous transmission needs to be evaluated.
The output power of the 5G device needs to be measured to be able to scale the measured SAR results correspond to the maximum power. For 5G FR1 devices the conducted RF power measurements can be done the same way as for other wireless technologies operating below 6 GHz frequency, by adding a cable to the transmitting antenna connector. Note that the product may be transmitting even if you are not making a phone call. The MWF focuses on a range of issues concerning mobile and wireless devices including RF health and safety, certification testing standards and requirements, counterfeit issues and accessibility.
You can learn more about the science, standards and what health experts are saying about the state of scientific knowledge. What is the radiation level SAR value of your mobile phone? There are 5 categories: A: for a SAR value smaller than 0. Do you have a question? Ask one of our advisors.
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