Specific Anthropomorphic Mannequin Model Research Articles

Specific absorption rate assessment of fifth generation mobile phones with specific anthropomorphic mannequin model and high‐resolution anatomical head model

With the spread and application of the fifth generation (5G) of mobile communication technology, the number of 5G mobile phone users increase rapidly. The traditional safety standard of electromagnetic radiation of mobile phones was set two decades ago, in which a homogeneous specific anthropomorphic mannequin (SAM) head model with standardized size and shape is utilized for specific absorption rate (SAR) evaluation. The SAM model has been proved conservative for SAR evaluation of 2G, 3G and 4G mobile phone antennas. However, it needs to be validated whether it is still suitable for SAR evaluation of 5G mobile phone antennas. A high-resolution anatomical head model with tissues including muscle, skull, cerebrospinal fluid and brain is developed in this paper. The SAR values of three different generation mobile phone antennas are simulated by utilizing both the SAM model and the high-resolution anatomical head model to assess their applicability. Numerical simulations show that the anatomical model may produce a higher SAR value than the SAM model for a 5G mobile phone antenna. So new head model may need to be developed for the SAR evaluation of 5G mobile phone antennas.

A Technique for the Early Detection of Brain Cancer Using Circularly Polarized Reconfigurable Antenna Array

In this paper, a technique for the early detection of brain cancer was proposed. The technique depends upon the use of an antenna and a model for the human head. The reflection coefficient (S11) was found for two cases: with and without tumor in the head model. The large increase of S11 due to the presence of the tumor provides a good indication for tumor detection. It also gives an idea about the size of the tumor. The antenna used was a reconfigurable four-element linear array of squared microstrip patches. Two arrays were designed one circularly polarized, the other linearly polarized. The antenna operates at Industrial Scientific and Medical (ISM) frequency 2.4 GHz. It was designed on FR-4 (lossy) substrate of relative permittivity 4.3 and thickness of 1.6 mm. To feed the array, a corporate feeding network was designed. The reconfigurability of the array was achieved using three single pole double throw (SPDT) switches. Two models of the human head were used; a specific anthropomorphic mannequin (SAM) model, and a 3-D head model consisting of four different head layers: skin, fat, skull and brain. The simulation calculates the reflection coefficient (S11) with and without tumor for circularly polarized (CP) and linearly polarized (LP) linear array. Calculations were taken for four sizes of the array. The best results were obtained with the four-element circularly polarized array. An increase in S11 of 1188% was obtained. Tumors as small as 5 millimeters (four-layer model) and 2.5 mm (SAM model) can be detected. Specific absorption rate (SAR) was calculated and found to be within the safe limit. A circularly polarized four-element linear antenna array was fabricated. The measured S11 and radiation pattern are in excellent agreement with simulated ones.

Exposure Limits: The underestimation of absorbed cell phone radiation, especially in children

The existing cell phone certification process uses a plastic model of the head called the Specific Anthropomorphic Mannequin (SAM), representing the top 10% of U.S. military recruits in 1989 and greatly underestimating the Specific Absorption Rate (SAR) for typical mobile phone users, especially children. A superior computer simulation certification process has been approved by the Federal Communications Commission (FCC) but is not employed to certify cell phones. In the United States, the FCC determines maximum allowed exposures. Many countries, especially European Union members, use the “guidelines” of International Commission on Non-Ionizing Radiation Protection (ICNIRP), a non governmental agency. Radiofrequency (RF) exposure to a head smaller than SAM will absorb a relatively higher SAR. Also, SAM uses a fluid having the average electrical properties of the head that cannot indicate differential absorption of specific brain tissue, nor absorption in children or smaller adults. The SAR for a 10-year old is up to 153% higher than the SAR for the SAM model. When electrical properties are considered, a child's head's absorption can be over two times greater, and absorption of the skull's bone marrow can be ten times greater than adults. Therefore, a new certification process is needed that incorporates different modes of use, head sizes, and tissue properties. Anatomically based models should be employed in revising safety standards for these ubiquitous modern devices and standards should be set by accountable, independent groups.

Analysis of Power Absorbed by Children's Head as a Result of New Usages of Mobile Phone

This paper deals with the influence of new uses of mobile phones (such as short message service, multimedia messaging service, video, etc.) on the SAR induced in different heads models. In particular, the exposure of children will be analyzed. For this reason, three heterogeneous models have been used in this study, two children head models (9 and 15 years old) and one adult head model (“visible human”). The specific anthropomorphic mannequin (SAM) homogeneous head model has been also used to compare all the results and to confirm that the SAM model always overestimates adult and child head exposure. Two handset models have been used: the first model is a triband mobile phone having a patch antenna and the second model is a generic model (known as IEEE mobile phone) having a monopole antenna inside a metal box covered by plastic. A comparison on SAR between adult and child head is given using the finite-difference time-domain method. The results of new positions are compared with respect to the results obtained with the voice position. These studies have been performed at 900, 1800, and 2100 MHz for the triband mobile phone and at 835, 1900, and 2100 MHz for the IEEE mobile phone. The comparison of the maximum SAR over 10 g between the different heads models (9 and 15 year olds and adult) shows that results were nearly similar. It was also pointed out that the value of the maximum local peak SAR in the SAM was always higher than in the adult and children models.

Study on SARs in Head Models With Different Shapes by Age Using SAM Model for Mobile Phone Exposure at 835 MHz

Four head models with the outer shapes of different ages were established using the specific anthropomorphic mannequin (SAM) model of IEEE Standard 1528. The criteria of head height, face length, head length, and head breadth by age were applied to build the models. We assumed that the shells of all the head models have the same dielectric properties with the head-equivalent tissue in order to simulate a real pressed ear. The cheek and tilt positions of three bar-type phone models were used, and the positioning processes against each head model were described in detail. Antenna input impedances of the phones under the test positions and specific absorption rate (SAR) distributions in the head models were computed using the finite-difference time-domain (FDTD) technique. Spatial peak SARs averaging over 1 and 10 g were compared for fixed input and radiated powers of all the phones. The effect of the dielectric properties in a younger head model on SAR result was analyzed. First, input resistance of the phone antennas in the cheek position gradually increased when head size grew with age, but those for the tilt position showed a slight decrease. Second, for a fixed input power, the head models by age changed peak 1- and 10-g SARs by approximately 15%. The electromagnetic absorption depths in the head models in the same test position were about the same, but the head-averaged SAR was higher in the younger model because of the smaller head volume. Third, for a fixed radiated power, the peak SARs got relatively lower in the smaller head model and higher in the larger head model, compared with those for the fixed input power since the smaller head model needs lower input power. Fourth, it was shown that simultaneous change in the conductivity and permittivity of head tissue within 20%-30% did not have a significant influence on energy absorption.

Specific Absorption Rate Values of Handsets in Cheek Position at 835 MHz as a Function of Scaled Specific Anthropomorphic Mannequin Models

A specific anthropomorphic mannequin (SAM) model was used to investigate the relation between local specific absorption rate (SAR) and head size. The model was scaled to 80 to 100% sized models at intervals of 5%. We assumed that the shell of the SAM model has the same properties as the head-equivalent tissue. Five handsets with a monopole antenna operating at 835 MHz were placed in the approximate cheek position against the scaled SAM models. The handsets had different antenna lengths, antenna positions, body sizes, and external materials. SAR distributions in the scaled SAM models were computed using the finite-difference time-domain method. We found that a larger head causes a distinct increase in the spatial peak 1-voxel SAR, while head size did not significantly change the peak 1-g averaged-SAR and 10-g averaged-SAR values for the same power level delivered to the antenna.