Annamaria Sârbu, Simona Miclăuş, Paul Bechet and Iulian Bouleanu
In this article we propose the use of the persistence spectrum to accurately assess the user’s exposure to electromagnetic field emitted by new generation of communication terminals. Persistent display view available within a Real Time Spectrum Analyzer (RTSA) enables a graphical observation of the main statistical parameters of a signal. A simple case study of exposure assessment was conducted by measuring the electric field strength in the close proximity of a mobile phone operated in a LTE-Advanced mobile communication network. The proposed measurement procedure is presented and then applied to a limited number of operating situations (VoIP, Video streaming, File upload, File download). We made use of the persistence spectrum capabilities to directly access the signal strength statistics in time. By this procedure we demonstrate a supplementary facility that enables direct visual tracing of exposure dynamics during real time usage of a specific mobile application.
This paper proposes a new Matlab-developed algorithm for automatic recognition of digital modulations using the constellation of states. Using this technique the automatic distinction between four digital modulation schemes (8-QAM, 16-QAM, 32-QAM and 64-QAM) was made. It has been seen that the efficiency of the algorithm is influenced by the type of modulation, the value of the signal-to-noise ratio and the number of samples. In the case of an AWGN noise channel the simulation results indicated that the value of SNR (signal-to-noise ratio) has a small influence on the recognition rate for lower-order QAM (8-QAM and 16-QAM). The length of the signal may change essentially the recognition rate of this algorithm especially for modulations with a high number of bits per symbol. Consequently, for the 64-QAM modulation in a case of 25dB signal-to-noise ratio the recognition rate is doubled if the sample rate is incresed from 5400 to 80640.
In order to provide assessment of mobile phone user exposure to electromagnetic fields emitted in the close vicinity of a mobile device we have measured real life UMTS and LTE signals at mobile data turn on. The paper presents some preliminary results of mobile phone user exposure assessment at mobile data turn by making use of a non-standardized procedure that enables the calculus of the radiated signal energy and duty cycle. Our results sustain that higher user exposure is expected within the first minute after mobile data is switched on as higher duty cycles and more than a third of the total radiated energy is found in this time period, as compared to the total signal monitoring time. Authors expect increased exposure if other application services are launched within this time frame. Moreover, special attention should be paid to user exposure assessment in the case of active call services with mobile data turned on. Because SAR is currently the sole standardized metrics in dosimetry, the authors propose the use of the measured signal radiated energy as well as the calculated duty cycle as complementary indicators of user exposure to electromagnetic fields in order to provide a more comprehensive view on mobile phone radiation exposure.
A portable radiocommunication device usually face-held during its use was chosen for characterizing its electromagnetic near-field distribution in air. Set to emit on a frequency of 440 MHz for digital voice communication with a maximum input power of 5 W, its antenna parameters were analyzed and the maps of field strengths were depicted up to distances of 20 cm from the device by using of a dual-sensor exposimeter. Since the occupational exposure safety limit for incident field levels was exceeded closer than 12 cm from the transceiver (for the magnetic field component), it became interesting to quantify the power loss in an alleged case of a brain containing also magnetite particles. Up to the present, only the electric field component was of interest when investigating biological effects of such exposures. With the new evidence from 2016, that human brain contains four orders of magnitude more magnetite nanocrystals than it was known before, a question rises in connection to the magnetic response of tissues impinged by fields with significant magnitudes and covering the hundreds of MHz frequency range. Starting from this question, we set-up a simulation in which a tissue with ferromagnetic content was mimicked for initial dosimetric computations
Simona Miclăuş, Paul Bechet, Annamaria Paljanos, Angel Marian Aron, George Mihai, Ion Pătru and Octavian Baltag
An analysis of the shielding effectiveness by the method of dual transversal electromagnetic cell is proposed for a set of conductive materials of the type wire-inserted textiles. Based on the experimental results, some of the materials are further on used to test their capability to effectively reduce the specific absorption rate of energy deposition in the head due to mobile phone, when they are covering the surface of the handset. It is demonstrated that both reducing and increasing the radiation that penetrates the head may appear, and this depends on both the material structure, its position and orientation relative to the device and to the frequency band the phone is emitting.
Simona Miclăuș, Ionel Dumbravă, Viorica Voicu and Paul Bechet
Portable transceivers emitting in the UHF radiofrequency band are sources of human electromagnetic exposure, when located in front of the face. Three output power levels were tested while the exposed target was a phantom filled with dielectric liquid simulating average human head behavior at the used frequency of 446 MHz. A flat phantom and a head phantom were scanned by an automatic E-field probe robot, based on the standardized procedure, in order to report specific absorption rates of energy deposition in the head. A discussion on the obtained results is provided, together with a comparison with other similar results in the literature. Consequences upon the safe use of such devices by public or by occupational personnel in the proximity of the brain and eyes are underlined.
Simona Miclaus, Paul Bechet, Mircea Stanic and Cora Iftode
Radiocommunications in the HF band depend on the ionospheric parameters of radiowaves reflexion, though the quality of a radio link depends on: the time of day; season; solar cycle; geographical position. Taking into account the ionosphere characteristics over Romania, a forecasting is made over four cities in our country in order to provide the values of the critical frequency foF2 of the F2 ionospheric layer over a 24 hours cycle. A comparative analysis of this parameter is applied by using the International Reference Ionosphere model and interpolated experimental data collected from the European Ionosonde Service. Results show that the f0F2 values are slightly underestimated in all four locations in the model versus measurements, sustaining the necessity of own measurements in order to prepare quality data links in Romania if HF band is to be used for emergency data communications.
Simona Miclăuş, Lucian Barbu-Tudoran, Paul Bechet and Octavian Baltag
By applying a non-standardized methodology and by using electric- and magnetic-field probes of small dimensions (< 1cm), we experimentally characterized the electromagnetic shielding properties of a fabric containing ferromagnetic microwires weaved on a single direction. Electronic microscopy and X-ray spectroscopy revealed the structure, dimensions and chemical elements content of the amorphous magnetic material. Electric shielding factor proved to be very low in the investigated frequency range, but magnetic shielding factor was high, especially when the weaving direction of the magnetic wires corresponded to the polarization direction of the emitting antenna, and showed some resonances. The magnetic shielding efficiency, if checked against an increasing incident magnetic flux density, proved not to change up to 200 nT. The investigated fabric have been previously proved to be very efficient in shielding the field emitted by a mobile phone in its near field, but present results show that near and far field shielding properties are different.
Simona Miclăuş, George Mihai, Angel Marian Aron, Cristian Mitrescu, Paul Bechet and Octavian Baltag
A dual band mobile phone model was used to check the shielding properties of an amorphous ferromagnetic textile against the radiation emitted by the handset. Two frequencies belonging to the 2nd and 3rd generation of mobile emission technologies were used, 897 MHz and 1950 MHz. The specific absorption rate (SAR) of energy deposition in a human head phantom was measured in standardized conditions. The textile contained micrometric-diameter wires of a ferromagnetic mixture embedded in a thin glass coat and weaved in a specific way. A set of fabric orientations and configurations (layering) were provided in the experiment in order to achieve a better shielding to the phone’s radiation. Compared with the non-shielded handset, SAR deposited in the head while using the fabric-covered phone could be decreased up to 30 % of its initial value – in case of 2G technology and up to 24 % – in case of 3G technology. This type of material shows one of the highest shielding efficiencies of the electric-field component in near-field exposure conditions reported until now. A cubic curve of SAR decrease in depth of the head was revealed in both uncovered and covered handset, the effect of shielding being larger at the higher frequency.