What is EMF?

The dynamic energy formed by electromagnetic fields is known as EMF radiation. This general description includes a broad spectrum of wavelengths and frequencies, with the RF signals that underpin cellular networks found between 600 MHz and 39 GHz, well below the frequency of visible or ultraviolet (UV) light. 5G mmWave signals utilizing frequencies up to 100 GHz are expanding the upper limits of this range.

Depending on the frequency, EMF radiation can be either non-ionizing or ionizing, with ionizing EMF capable of alter cellular structures, including DNA. While the non-ionizing radiation from power lines, cell phones, and microwave ovens is considered safe at low exposure levels, high-energy ionizing radiation from sources including X-rays and gamma rays presents a greater risk to the ecosystem and human health.

EMF Measurement

The magnitude of EMF radiation can be measured using an EMF tester equipped with a probe or isotropic antenna that detects the field intensity within a given area. EMF measurements of electrical energy, typically in volts per meter (V/m), magnetic field strength in milligauss (mG) and spectrum analysis (frequency) readings combine to paint a complete picture of EMF behavior. Radiation exposure levels can also be determined by measuring the power density in watts per square meter (W/m²). Testing processes for wireless networks often includes a pre-programmed comparison of EMF levels to standardized permissible limits.

The primary objective of electromagnetic testing is to safeguard public health and prevent any harm to humans or the environment. The best way to accomplish this is by setting limits for exposure levels, then performing monitoring to ensure this is being achieved. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has established limits for acceptable EMF emission levels that serve as a basis for field testing. 

These standards for EMF harmful levels are relevant to wireless communication in general, and 5G in particular, with base stations emitting radiofrequency electromagnetic fields (RF EMF) ranging from several hundred MHz to several GHz. Despite the higher frequencies and cell densities, there is no evidence linking 5G to health risks. However, assuaging public and private concerns is one of the fundamental reasons for ongoing electromagnetic field testing.

EMF Test Methodologies

The radios deployed in cell sites must comply with standards defined by regulators and government agencies including ICNIRP, IEEE, ARPANA and the Federal Communication Commission (FCC). There are several standard EMF test methodologies in use, along with options that allow data to be interpolated or augmented to paint a more complete picture. 

• Broadband: As the name implies, EMF detection methods and test devices in the broadband category perform EMF measurements across a wide range of frequencies. These devices are used to assess overall EMF exposure but are not sensitive enough to determine the potential sources and types of EMF. This shortcoming makes broadband methods less suitable for 5G network testing.  
• Frequency selective and code selective: Spectrum-based (frequency selective) methods measure power in the band where the signal of interest is transmitting. This method is commonly used to evaluate all types of radio technologies. Beam-based (code selective) EMF testers utilize demodulation to isolate the contribution of each carrier, cell, and beam. This method is especially useful for measuring the maximum EMF levels produced through 5G beamforming. 
• Extrapolation: When direct EMF inspection and testing is not feasible, or beam power levels are not consistent, extrapolation methods can be used to predict the maximum exposure levels expected from an EMF source. Extrapolation is also used to assess the power of a fully occupied 5G channel based on the emissions of pilot signals. To perform these tests correctly, traffic beams must be aimed directly at the electromagnetic field detector.  

Ionizing radiation is defined as any EMF emission exceeding 300 GHz, making it capable of removing electrons from atoms to create ions. This process can disrupt molecular bonds in biological tissues with potentially serious health consequences when too much radiation absorbed. 5G base stations, cell towers, and other wireless communication infrastructure does not produce ionizing radiation

• Examples of ionizing radiation: Along with X-rays and Gamma rays, ionizing radiation comes from sources including nuclear reactions, high-energy solar flares, and particle accelerators. Safe applications of ionizing radiation include essential diagnostic medical procedures like CT scans and PET scans.

• Measuring ionizing radiation: Ionizing radiation is measured using specialized devices like Geiger counters capable of counting ion pairs within the detector and interpreting that data to determine the amount of radiation. Instruments like scintillation detectors can measure both the energy and intensity of the radiation.

• Ionizing vs non-ionizing radiation: Non-ionizing radiation creates a much lower energy output, but it is still capable of producing heating effects. Non-ionizing RF fields can penetrate the human body, but the depth of penetration becomes lower as the frequency gets higher.  

Antennas play a key role in measuring and testing for electromagnetic radiation in 5G networks and other wireless systems. By directly interacting with EMF waves, devices with integrated antennas can assess how the waves are propagating through the environment and affecting communication systems and users.

Isotropic antennas: 
An isotropic antenna is a theoretical antenna that receives energy in all directions with the same sensitivity. In practical application, this hypothetical concept is turned into reality by combining three antennas (one each for the X, Y, and Z axis’) within a single form factor. The global field strength is calculated by taking the quadratic sum of all three antennas. 

Directional antennas: 
These antennas can only send or receive EMF energy in one direction. This limits the collection of EMF waves to a much narrower pattern, but directional antennas do offer higher gain, meaning they can receive signals from further distances. This makes directional antennas useful for testing for electromagnetic radiation from a fixed source, such as a cell tower.  

Radiation patterns of isotropic antennas: 
Both isotropic and directional antennas are characterized by their radiation patterns, either through the E-Plane (vertical), H-Plane (horizontal), or 3-axis dimensions. The radiation patterns are equivalent in the transmitting and receiving dimensions which makes it easier to interpret received signals during EMF testing. 

Testing for electromagnetic radiation in wireless networks has always been challenging, with vast geographic areas to assess and external satellites, radar, and microwave systems making it difficult to pinpoint the true source of EMF. 5G brings additional challenges, with higher frequencies, beamforming, and cell densification bringing more attention to 5G EMF testing from government agencies:

• 5G Time Division Duplex (TDD): In 5G NR TDD, beams are delivered in different time slots and power levels. This makes it necessary to measure the profile of each beam throughout the entire channel bandwidth and interpret the results to obtain the total emissions. This complexity requires more advanced test solutions than were required for previous wireless generations.
• Tighter requirements: Despite generating non-harmful levels of non-ionizing EMF, the advent of 5G has increased fears over health impacts. Several markets have tightened requirements and made it difficult to provide 5G-only service. Electromagnetic radiation measurement and reporting against national and local standards is mandatory for mobile operators in several countries.
• User traffic dependency: Unlike previous generations of wireless technology where signals were radially transmitted with a consistent EMF signature, 5G RAN selectively transmits to users, leading to continuous fluctuation in EMF levels. To factor in this variation while fairly assessing the dangers of electromagnetic radiation in each area, new 5G EMF testing methods have been developed and validated. 

The VIAVI OneAdvisor 800 platform provides the flexibility needed to address 5G testing challenges in the wireless, transport, and fiber categories. The OneAdvisor 800 EMF analyzer is a cost-effective solution for 5G electromagnetic radiation measurement for frequencies up to 44 GHz. The solution offers customizable EMF limits based on relevant standards that can be saved for continued use.

• Radiation and emissions measurement: In the EMF spectrum mode, the OneAdvisor 800 EMF tester measures the aggregate energy of all radio signals in the selected band. The frequency-selective EMF Scanner mode is used to measure emissions from individual channels and identify those contributing to higher EMF. System test time is configurable from 1 to 60 minutes.
• RAN measurement capabilities: The solution also includes a code selective electromagnetic testing mode capable of advanced 5G RAN beam analysis. The EMF power of 5G control beams over multiple PCIs is used to find the maximum power of the entire 5G channel width. This method also allows for simultaneous EMF measurements of traffic (user) beams to assess all impact of EMF emissions on users more accurately.
• RF field strength measurement: OneAdvisor 800 EMF Analyzer detects the field strength of radio signals over the air using the built-in isotropic antenna. Electric field strength is measured in Volts/meter while magnetic field strength is measured is Amps/meter.

VIAVI has leveraged decades of wireless network testing expertise to develop the ideal EMF field test solution for radio access networks. VIAVI OneAdvisor 800 EMF supports measurement references based on ICNIRP, ARPANSA, BGV, FCC, IEEE, Italy CM, and Safety Code 6 limits.