Knowledge Base

What is SAR Value?

SAR (Specific Absorption Rate) is a value that measures how much energy the human body absorbs from a radio frequency (RF) electromagnetic field. It is often used to express the absorption of energy emitted by wireless communication devices such as mobile phones by the body. The SAR value is measured in Watts/Kilogram (W/kg). This value is determined in the scenario where the device is operating at its highest power and held closest to the body. The SAR value is an important indicator of the device's safety and is limited by legal regulations.

Why is SAR Value Important?

SAR value is important due to its potential effects on human health. Radio frequency energy emitted from devices such as mobile phones is absorbed by body tissues. Prolonged use of devices with high SAR values can theoretically lead to tissue heating and potential health problems. These problems may include headaches, fatigue, memory problems, and, in the long term, an increased risk of cancer. However, scientific evidence on this subject is still debated, and a definitive causal relationship has not yet been proven. Nevertheless, as a precautionary principle, it is preferable to have low SAR values.

Important Note: The SAR value is only a measure of the energy emitted by the device and does not solely determine the health risk. Factors such as exposure time, usage habits, and individual sensitivity are also important.

How is SAR Value Measured?

SAR value is measured in a laboratory environment using standard test methods. These tests involve placing the device in a model of the human head or body and operating the device at its highest power. Measurements are taken using special sensors to determine the electromagnetic field strength and tissue temperature at specific points. The SAR value is calculated by mathematically processing the data obtained from these measurements.

Step-by-Step SAR Measurement Process:

1. Model Preparation: Models (phantoms) representing the human head and body are prepared, filled with a special liquid. This liquid mimics the electrical properties of human tissue.
2. Device Placement: The device to be tested is placed in a specific region of the model (e.g., near the ear or body).
3. Device Operation: The device is operated at its highest transmission power and in a mode representing the worst-case scenario (e.g., continuous data transmission).
4. Measurement Taking: Special sensors (e.g., electric field probes) are used to measure the electromagnetic field strength and tissue temperature. These sensors take measurements at different points inside the model.
5. Data Processing: The measured data is mathematically processed to calculate the SAR value. These calculations are proportional to the square of the electromagnetic field strength.
6. Reporting: The obtained SAR value is stated in the test report. This report also includes information such as test conditions, the model used, and the device's specifications.

What are the SAR Value Limits in Turkey and Worldwide?

Legal limits for SAR values may vary in different countries. However, the generally accepted limits are as follows:

• European Union (EU): 2 W/kg for head and body (averaged over 10 grams of tissue)
• United States (USA): 1.6 W/kg for head and body (averaged over 1 gram of tissue)

EU standards also apply in Turkey. That is, the SAR value of a mobile phone must not exceed 2 W/kg for the head and body. These limits are set to protect human health, and device manufacturers must comply with these limits.

How Can I Find Out My Phone's SAR Value?

There are several ways to find out your phone's SAR value:

• Phone's User Manual: Most phone manufacturers state the SAR value in the device's user manual.
• Manufacturer's Website: You can search for the SAR value on the manufacturer's website using the phone's model number.
• Phone Settings: On some phones, the SAR value information can be found directly in the device's settings menu. (Usually located in the "About" or "Legal Information" section.)
• *#07# Code: On some phones (especially Android devices), you can display the SAR value by dialing *#07#. However, this code may not work on every device.

Example: To find the SAR value of a Samsung Galaxy S23, you can visit Samsung's website or refer to the phone's user manual.

What Factors Affect the SAR Value?

There are many factors that affect the SAR value:

• Device Design: Antenna location, device shape, and materials used can affect the SAR value.
• Operating Frequency: The frequency band used by the device can affect tissue absorption.
• Transmission Power: As the transmission power of the device increases, the SAR value also increases.
• Proximity to the Body: How close the device is held to the body significantly affects the SAR value. The closer the device is to the body, the higher the SAR value.
• Network Conditions: In poor network conditions, the device may have to operate at a higher power, which can increase the SAR value.

Real-Life Example: In a case study, it was observed that the SAR value increased and the device heated up more when a user constantly used their phone in an area with low signal strength. When the user used the phone in an area with better signal, the SAR value decreased and the device's heating reduced.

What Can Be Done to Reduce the SAR Value?

While it is not possible to completely eliminate the SAR value, some measures can be taken to reduce exposure:

• Keep the Phone Away from the Body: Avoid carrying the phone in your pocket or in direct contact with your body. You can carry the phone in your bag or backpack.
• Use a Headset or Speakerphone: Use a headset or speakerphone during phone calls to keep the phone away from your head.
• Prefer SMS Messages: Shorten the exposure time by preferring SMS messages instead of long phone calls.
• Talk in Areas with Good Signal Strength: Avoid using the phone in areas with poor signal strength. Good signal strength allows the device to operate at a lower power.
• Reduce Data Usage: Activities such as continuous data downloading or video watching can cause the device to operate at a higher power. Prefer to do these types of activities over Wi-Fi.
• Keep the Phone Away While Sleeping: Avoid keeping the phone in the bedroom and keep the device turned off or in airplane mode while sleeping.
• Prefer Phones with Low SAR Values: When buying a new phone, prefer models with low SAR values.

Important Note: Measures taken to reduce the SAR value can help reduce exposure, but do not completely eliminate the energy emitted by the device.

What You Need to Know About the SAR Values of 5G Phones

5G technology uses higher frequencies and more complex antenna systems. This has led to some concerns about the SAR values of 5G phones. However, in general, the SAR values of 5G phones remain within legal limits. The effects of 5G technology on SAR values are as follows:

• Higher Frequencies: Since 5G operates at higher frequencies, tissue absorption may be more superficial. This may cause the SAR value to be higher in certain areas.
• MIMO and Beamforming: 5G uses technologies such as MIMO (Multiple Input Multiple Output) and beamforming. These technologies provide more efficient communication by focusing the signal in a specific direction. However, this may affect the distribution of the SAR value.
• Different SAR Test Methods: More advanced test methods are used to measure the SAR values of 5G devices. These methods aim to obtain more accurate results by taking into account the complexity of 5G technology.

Code Example (Hypothetical): Suppose that in a scenario where a 5G device uses beamforming technology to direct the signal, the SAR value is concentrated in a specific area. The following code example can be used to simulate this situation (Python):

import numpy as np
import matplotlib.pyplot as plt

# Parameters
number_of_antennas = 8
wavelength = 0.03 # meters
distance = 1 # meter
angles = np.linspace(-np.pi/2, np.pi/2, 100) # Angles between -90 and 90 degrees

# Beamforming vector (simple example)
beamforming_vector = np.exp(1j * 2 * np.pi / wavelength * np.arange(number_of_antennas) * 0.01)

# Calculating field strength
field_strength = np.abs(np.sum(np.exp(1j * 2 * np.pi / wavelength * distance * np.sin(angles)[:, np.newaxis] * np.arange(number_of_antennas)), axis=1) * beamforming_vector[0])**2

# Creating a heat map representing the SAR value (simplified)
sar_value = field_strength / np.max(field_strength) # Normalized field strength

# Drawing the graph
plt.polar(angles, sar_value, label='SAR Value (Normalized)')
plt.title('SAR Distribution with Beamforming (Simulation)')
plt.legend()
plt.show()

This code is a simple simulation showing how the SAR value is distributed when a 5G device focuses the signal in a specific direction using beamforming technology. Real SAR measurements require much more complex and detailed tests.

What is the Scientific Evidence Regarding SAR Values and Long-Term Health Effects?

The relationship between SAR values and long-term health effects is a subject of ongoing scientific research. Currently, there is no definitive evidence that cell phone use causes cancer, brain tumors, or other health problems. However, some epidemiological studies suggest that long-term and heavy cell phone use may be associated with certain health risks. The results of research on this topic can be conflicting, and more research is needed.

Important Note: The World Health Organization (WHO) and the International Agency for Research on Cancer (IARC) have classified cell phone use as "possibly carcinogenic to humans." This classification means that there is no definitive evidence, but the risk cannot be completely ruled out.

Case Study: The INTERPHONE study is a large international study that examined the relationship between cell phone use and brain tumors. This study showed that long-term and heavy cell phone use (10 years or more) may increase the risk of certain types of brain tumors. However, these results are not definitive, and more research is needed.