Of the smartphones that we can find in stores, we know almost everything. We know your specifications, the quality of your screen, your performance, what experience your cameras offer us and many other interesting features that can help us find the mobile phone that best meets our needs. However, there is a fact that brands do not reveal and that, due to how difficult it is to obtain it, until now it has avoided us: the radiation that they emit, or, expressed in a more precise way, the EIRP.
Although later we will investigate the nuances of this parameter, which has them, for the moment it is good for us to know that the acronym PIRE describes the Equivalent Radiated Isotropic Power, a quantity used in radio communication systems that reflects the power emitted by the antenna of our smartphone. Most of today’s mobile phones use fractal-type antennas because they save space within the terminal and improve their ability to access mobile telephony networks. And these antennas emit electromagnetic radiation.
It is likely that in the not too distant future the transmission will be popularized by booster technology, which does not use a fractal antenna, but injects the radio waves into a thin metal sheet, called the ground plane, which is housed inside of the mobile PCB (the printed circuit board). This innovation will make smartphones simpler, thinner and even more compact. And it may require re-evaluating the way we measure and interpret the radiation emitted by the terminals, but, meanwhile, the EIRP offers a very accurate approximation to this parameter.
Before starting here you have our declaration of intentions
We can not go ahead without explaining to you in advance that our intention is not to inquire into whether the radiation emitted by mobile phones has any impact on our health or not. So far no rigorous scientific study has established a strong relationship between the radiation emitted by smartphones, which is non-ionizing, and cancer. The only biological effect demonstrated is that this form of radiation can cause the tissues to heat up more, but from there to say that it increases the probability of suffering from cancer mediates an abyss.
So far no scientific study has established a strong relationship between non-ionizing radiation emitted by smartphones and cancer
This year, two studies have been carried out by the US National Toxicology Program and the Italian Ramazzini Institute, both carried out on rats and mice. And both have concluded that, after exposing these animals to non-ionizing radiation, a certain type of specimen (male rats, but not female rats and mice) developed schwannomas, benign tumors containing Schwann cells.
Even so, it is not at all clear the role that non-ionizing radiation can play in human beings, if any. Scientists still do not understand well the biological mechanisms that may or may not trigger this form of radiation, but, in any case, we must not forget that in recent years there have been many serious studies that seek to shed light on this debate, and none of they have put clear evidence on the table for us to worry about.
In that case it is likely that you are wondering why we have decided to prepare this article, especially considering how complex it is to measure the radiation emitted by smartphones, as we will see below. The answer is simple: because it is a characteristic of our mobile phones that it is very difficult to find, and, the more information we have about the devices in which we invest our money, the better. At the end of the day is another fact that we can assess when choosing our next terminal. Or not. Information is power, and we firmly believe that our obligation is to deposit as much as possible in the hands of our readers.
Our partner: the specialized laboratory of ATL Europe
This research article would not have been possible without the collaboration of ATL Europa, a Spanish engineering company based in Leganés (Madrid) specialized in the design of radiofrequency and microwave equipment. It was founded in 1991 and has a powerful R & D department that has allowed it to develop professional communication solutions for almost three decades. They are experts in WiFi networks, 2G, 3G, 4G, 5G, TETRA, ZigBee, GALILEO, VHF and GNSS, among other areas.
90% of the solutions they design, according to Fernando Niubó, the CEO of ATL Europe, is not previously available in the market, reflecting the innovation capacity of this company. Among its designs are repeaters, inhibitors, antennas and combiners or mixers of radio frequency signals, in addition to other devices involved in wireless communications systems and RF equipment.
During one of my many visits to their facilities to prepare this article I was struck by one of the many projects they have developed, which can help you to guess the magnitude of the challenges facing the engineering department of this company: a rifle RF inhibitor of signal antidrones with a scope of up to 3 km designed so that it can be used by the Forces and Bodies of Security of the State and the army (this device is not sold to individuals).
In any case, the reason that strengthened the collaboration between Engadget and ATL Europe was that the latter company has the necessary resources and instruments to measure the radiation emitted by the smartphones that we had set out to study. The most important element of all we have used is its anechoic chamber, which is nothing more than a room with considerable dimensions (measures 6.10 m in length, 3.10 m in width and other 3.10 m in height ) designed to simulate the free space, so that the measurements that are carried out in its interior come only from the radiation emitted by the device that is being analyzed. Just what we needed to move this article forward.
So that it can carry out its function, this anechoic chamber has been built in a very rigorous way. And it is that all of it is covered by metal plates that transform it into an authentic Faraday cage, so that the electromagnetic fields present on the outside of the chamber do not exert any influence in its interior, thus guaranteeing the absence of disturbances in the measurements. In addition, the interior of the chamber is completely covered by carbon plates that manage to absorb a good part of the radiofrequency radiation that falls on its surface.
In the photographs of the anechoic chamber that illustrate this article (it is the same one that we have used in the tests) you can see that the carbon panels have a very peculiar shape. This design, together with the capacity of radiation absorption of the material, responds to the need to minimize as far as possible the reflections of electromagnetic waves inside the camera. A final interesting note to conclude this section of the article: the anechoic chamber of ATL Europe is capable of recreating the adequate space to measure radiant elements in the frequency range that extends between 10 MHz and 40 GHz.
This is the methodology that we have defined to carry out the measures
All the measurements that I will describe throughout this article have been carried out by the technicians of ATL Europe, who, in addition, have defined the ideal strategy by which we had to choose to obtain rigorous results and as accurate as possible. From there, the interpretation of these measures and the conclusions we will reach correspond to Xataka. The scheme that you have a few paragraphs below describes quite accurately the test environment we have used, and is based on the fact that the typical behavior of all multifrequency modules for mobile telephony is characterized by decreasing power when increasing the frequency.
Our objective, as we have seen in the first paragraphs of the article, is to evaluate the maximum power that each smartphone emits, so that the technicians have carried out the measurement in the 900 MHz band because it is in which the power is expected issued by each terminal is maximum. The mobile telephone operator in whose network we have carried out the measurements is Movistar, and the first challenge we had to face was to transfer the signal emitted by the base station to the interior of the anechoic chamber to provide coverage for smartphones (one station base is a fixed radio installation belonging to the operator and allowing the connection to the mobile telephony network of nearby terminals).
Capturing this signal is responsible for an antenna housed outside the anechoic chamber, but this signal does not travel as it is inside, but must be previously attenuated by a variable attenuator to ensure that each smartphone is really emitting the maximum power of which he is capable. The presence of the attenuator is necessary because the terminals are forced to emit a more powerful signal as they receive from the base station is weaker, and this device is crucial to ensure that each phone actually receives the base station from the base station. minimum signal needed to maintain the connection.
The output of the variable attenuator is connected to a directional coupler housed inside the anechoic chamber, which is a device in which a portion of the transmitted signal is coupled in order to perform the relevant calculations. The direct signal received by the directional coupler is redirected to the antenna housed inside the camera, which, in turn, sends it to the smartphone, which is placed at the other end of the anechoic chamber, 3 m away.
The antenna installed inside the camera is oriented by a laser to the center of the screen of each mobile phone because the location and shape of the fractal antenna of each terminal is different. In this way we make sure to deliver the signal to each smartphone in identical conditions. On the other hand, when it is the mobile that emits the signal is picked up by the antenna inside the camera and redirected to the directional coupler, which is responsible for separating the down and up links that we have spoken in the previous paragraph to deliver only the latter, which contains the signal emitted by the terminal, to the spectrum analyzer housed outside the anechoic chamber.
The role of the spectrum analyzer is very important because it is the device that will allow us to accurately measure the maximum power delivered by each of the smartphones, which is, in short, the parameter we want to evaluate. The simple scheme that you have below these lines clearly describes the test scenario that we used during the tests, and, as you can see, it reflects everything we have seen up to this moment.
The following photograph shows the inside of the anechoic chamber that we used in the tests of the terminals. You can see the shape of the carbon panels that cover the walls, the floor and the roof, and that are responsible for absorbing a good part of the non-ionizing radiofrequency radiation emitted by both the antenna housed inside the camera and by the smartphone itself to minimize reflections and simulate an open field.
In the following photograph you can see the appearance of the antenna housed inside the anechoic chamber, which, as we have seen, is responsible for collecting the signal placed at the output of the directional coupler to deliver it to the smartphone, and also receiving the signal from rise of the latter to route it to the spectrum analyzer. This antenna in particular is a GSM probe that works in the frequency range between 824 and 960 MHz.
In the picture that you have below these lines you can see the spectrum analyzer that receives the signal emitted by each smartphone (uplink) once it has been separated from the downlink by the directional coupler. The model used by ATL Europe technicians is an Anritsu MS2665C, a high precision spectrum analyzer that fits like a glove in the test scenario that we have defined to measure the maximum power emitted by each of the mobile phones.
Although we have reviewed in detail the context in which we have carried out the tests and the equipment we have used, if you are curious and want to know the test conditions in detail you just have to take a look at the table we published below these lines. Here you can find interesting information, such as, for example, the exact frequencies of mobile phones and base station channels, the characteristics of the signal received in the laboratory from the base station, the losses that occur when transmitting the signal from the antenna inside the camera to the smartphone and also the loss that takes place when transporting the signal to the spectrum analyzer.
It is not necessary at all to know how to interpret all the information included in this table to understand what we are going to see next, but if you are curious and want to know precisely the test scenario that we have defined, here are all the details:
OPERATOR SELECTED FOR THE Movistar GSM 900 TEST
FREQUENCY CONCESSION FOR MOVISTAR 900 MHz Uplink (mobile emission frequencies): STAR Freq. 890.1 MHz / STOP Freq. 904.9 MHz
Downlink (channels of the base station): STAR Freq. 935.1 MHz / STOP Freq. 949.9 MHz
SIGNAL RECEPTION IN THE PPEAK TEST LAB: 938 MHz
SIGNAL IN ANTENNA ENTRY (900 MHz) From Ppeak att 6 dB: -64
From Ppeak att 10 dB: -66.5
LOSS OF TRANSMISSION TOWARDS THE MOBILE (900 MHz) G antenna: 10 dB
Loss by propagation in 3 m to 942 MHz: -41.5 dB
Total loss: -31.5 dB
SIGNAL RECEIVED BY THE APPROXIMATE MOBILE (LOSS IN ANTENNA ENTRY + PROPAGATION) -98 dBm
LOSS BY TRANSMISSION TOWARDS THE SPECTRUM ANALYZER (900 MHz) Loss by propagation in 3 m to 897 MHz: -41.1 dB
Loss per coupling: -20 dB
Cable loss: -1 dB
Total loss: -62.1 dB
Total offset: 62.1
Measurement of the maximum power emitted by each smartphone
Finally we come to the culminating section of this article: the one that collects the results we have obtained during the tests of mobile phones in the anechoic chamber. Our initial purpose was to test a sample as representative as possible of the terminals that we can currently find in the market to check if there are significant differences in terms of the maximum power delivered by some brands or others.
For this reason, we have selected the following smartphones from the main manufacturers (we list them in alphabetical order): Apple iPhone XS Max, BQ Aquaris C, Huawei Mate 20 Pro, LG G7 ThinQ, Motorola Moto Z3, OnePlus 6T, OPPO R15 Pro, Samsung Galaxy Note 9, Sony Xperia XZ3, Xiaomi Mi 8 (European version) and Xiaomi Mi 8 (global version). The reason why we have included two terminals of Xiaomi is, simply, because we find it interesting to find out if there is any difference in the level of radiation emitted by two different versions of the same mobile phone, and the Mi 8 model of Xiaomi is easy to achieve both in European and global edition.
The twelfth smartphone we have used is a ZTE Kis II Max, a veteran cell phone that, unlike the models that I mentioned in the previous paragraph (all terminals are fully valid), reached the market about five years ago. We have included it as a control smartphone that has helped us to calibrate the measurement instruments involved in the tests within the anechoic chamber, but it is also interesting to see to what extent the maximum power delivered by an old smartphone differs when compared to the terminals that we can find now in stores.
As you will see below, we have broken down the measurements into two different tables because each of them reflects a different use scenario. In the first of them we made a call to each of the smartphones and we measured the maximum power radiated by all of them when they receive the call, but without going off-hook. The other table shows the results we have obtained in the second test scenario, in which we carried out the measurements once the call was established, but this time during the conversation.
To analyze in detail the behavior of each smartphone we have taken the measurements in two different usage scenarios: making the call, but without picking up, and once the call is established and during a conversation
It is important that we take into account that the results of the tests are subject to possible variations that may occur in the environment, and also that it is likely that other identical smartphones, and therefore, of the same brands and the same models, would throw slightly different results under the same test conditions. This is due to the fact that the maximum radiation level delivered by each terminal is conditioned by technical and environmental factors that can not be foreseen and are beyond our reach.
Even so, the testing methodology we have used is sufficiently rigorous and the instruments sufficiently precise so that, even accepting these possible variations, we can take the results we have obtained as reasonably accurate approximations. The only presumably anomalous result is that thrown by Sony’s Xperia XZ3. And it is presumably anomalous because the power radiated by this terminal is exaggeratedly reduced if we compare it with the other smartphones.
For this reason, laboratory technicians have come to the conclusion that, although the unit we used seemed to behave normally, its multifrequency module should not work properly based on the results we have obtained. The measurement that the Sony smartphone has thrown in the second test scenario (when picking up and speaking once the call is established), although it is clearly lower than that of the other terminals, is not as exaggeratedly reduced as in the first scenario ( with incoming call but without picking up), which suggests that this terminal really can be the one that emits least electromagnetic radiation of all. In any case, regardless of whether the multifrequency module of this terminal works correctly or not, this result is aligned with the measurement obtained in the study of radiation emission carried out by PhoneArena, in which this Sony smartphone has resulted be the one that emits least electromagnetic radiation.
The most important parameter of all those included in the tables is the Equivalent Radiated Isotropic Power (EIRP) because it reflects the amount of power emitted by an ideal antenna capable of distributing it with the same intensity in all directions to generate the power density that we can measure in the direction of maximum gain. This is the formal definition, and, as you can see, it is quite tricky, so we can stay with a much simpler idea: the EIRP, in practical terms, reflects the power of the signal that the smartphone emits, and, therefore, also its level of emission of electromagnetic radiation.
In the tables we have collected this parameter using two different units: decibels (dBm), which is the unit usually used, and watts, which is a unit with which users are much more familiar. This is the reason why we have also decided to include the radiated power measurement in watts. On the other hand, the last two fields of each table reflect the power density and the intensity of the electric field taken at a distance of 1.5 cm. This reference value roughly matches the distance at which we usually place the mobile phone in our head when we use it to hold a conversation.
The first table is the one that reflects the maximum radiated power measurements that we have taken when the terminals receive the call, but without picking up:
MEASURES TAKEN WITH UNCLOGGED INCOMING CALL ZTE KIS II MAX (SMARTPHONE CONTROL) APPLE IPHONE XS MAX BQ AQUARIS C HUAWEI MATE 20 PRO LG G7 THINQ MOTOROLA MOTOROLA Z3 ONEPLUS 6T OPPO R15 PRO SAMSUNG GALAXY NOTE 9 SONY XPERIA XZ3 XIAOMI MI 8 (VERSION EUROPEA) XIAOMI MI 8 (GLOBAL VERSION)
FREQUENCY (MHz) 895.10 903.70 895 895.10 895.10 895.10 895.10 895 903.60 891.14 895.10 891.10
DIRECT MEASUREMENT ANALYZER (dBm) -30.42 -35.91 -37.05 -35.17 -33.45 -30.98 -30.54 -40.05 -35.40 -47.68 -37.11 -34.43
PEPE ISSUED BY THE SMARTPHONE (dBm) 31.68 26.19 25.05 26.93 28.65 31.12 31.56 22.05 26.70 14.42 24.99 27.67
PEPE ISSUED BY SMARTPHONE (W) 1,47 0,42 0,32 0,49 0,73 1,29 1,43 0,16 0,47 0,03 0,32 0,58
POWER DENSITY AT 1.5 CM (dBm / cm2) 31.33 25.84 24.70 26.58 28.30 30.77 31.21 21.70 26.35 14.07 24.64 27.32
INTENSITY OF THE ELECTRIC FIELD AT 1.5 CM (V / m) 0.42 0.22 0.20 0.24 0.30 0.39 0.41 0.14 0.24 0.06 0.19 0.26
And the second table contains the measurements that we have obtained once the call is established and during a conversation:
MEASURES TAKEN WITH INCOMING CALL DISPLAYING AND TALKING ZTE KIS II MAX (SMARTPHONE CONTROL) APPLE IPHONE XS MAX BQ AQUARIS C HUAWEI MATE 20 PRO LG G7 THINQ MOTOROLA MOTOROLA Z3 ONEPLUS 6T OPPO R15 PRO SAMSUNG GALAXY NOTE 9 SONY XPERIA XZ3 XIAOMI MI 8 ( EUROPEAN VERSION) XIAOMI MI 8 (GLOBAL VERSION)
FREQUENCY (MHz) 895 893 895 895 895 830.96 895 895 895 890 895 895
DIRECT MEASUREMENT ANALYZER (dBm) -30.71 -35.88 -37.84 -35.43 -32.81 -31.14 -30.83 -30.85 -35.62 -41.27 -37.95 -34.73
PEPE ISSUED BY SMARTPHONE (dBm) 31.39 26.22 24.26 26.67 29.29 30.96 31.27 31.25 26.48 20.83 24.15 27.37
PEPE ISSUED BY SMARTPHONE (W) 1,38 0,42 0,27 0,46 0,85 1,25 1,34 1,33 0,44 0,12 0,26 0,55
POWER DENSITY AT 1.5 CM (dBm / cm2) 31.04 25.87 23.91 26.32 28.94 30.61 30.92 30.90 26.13 20.48 23.80 27.02
INTENSITY OF THE ELECTRIC FIELD AT 1.5 CM (V / m) 0.41 0.22 0.18 0.24 0.32 0.39 0.40 0.40 0.23 0.12 0.18 0.26