Hip-Worn Cellular Telephone on Moving Man

An evaluation of the changes caused by movement of the body in the radiation pattern of a simplified cellular telephone worn on the hip of a man is performed.

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An evaluation of the changes caused by movement of the body in the radiation pattern of a simplified cellular telephone worn on the hip of a man is performed. The telephone consists of a ground board with a helical antenna and is operated at 1.9GHz. The human model is based on the Visible Human Project male and is described by a 5mm cubical mesh with material parameters adjusted for 1.9GHz. The default position of the male is shown in Figure 1 where the arms are crossed in front of the body.

The simplified cellular phone is positioned on the right hip of the body to emulate a belt-mounted situation and the radiation characteristics of the phone are computed (shown in Figure 2 ). The phone is placed into a variable mesh region with a 1mm cubical cell size to give reasonable resolution on the phone (see Figure 3 ). The software product Varipose is then used to reposition the limbs of the body and simulations are performed to describe the impact on the radiation pattern caused by the moving limbs.

Walking Man

As a first example, the man is repositioned into two walking poses where the arms and legs are extended as if taking a step forward with the right and left legs. These poses are shown in Figure 4 and Figure 5 . The three-dimensional radiation patterns are shown in Figure 6 and Figure 7 . The default position of the body ( Figure 2 ) causes most of the radiation to be directed to the right rear quadrant. When the man is striding, the position of the arm causes a redistribution of the patterns which directs more energy forward. Radiation gain patterns for the individual field components in the XY plane are shown in Figure 8 and Figure 9 .

Moving Arm

For a second example, the position of the arm above the phone is swept through a set of positions to describe the pattern changes. The right arm is positioned with a slight bend in the elbow and with the shoulder varied from the rear to the front positions, as shown in the series of figures from Figure 10 to Figure 16 .

In the series of figures from Figure 17 to Figure 23 the impact of the arm position can be seen in the changes to the three dimensional radiation patterns. The two-dimensional patterns for the Phi and Theta directed gains are shown in Figure 24 and Figure 25.

Comparison of Impedance and Efficiency

For each of the cases considered previously, the impedance and system efficiency are detailed in the table below. As can be seen, slight changes to the impedance are noted for different arm positions while variations in the system efficiency vary nearly 3 to over 9 percent.

Case	Resistance	Reactance	System Efficiency
Default Position	14.9	-30.1	2.76
Walk Position 1	9.57	-43.3	5.55
Walk Position 2	9.54	-39.9	5.16
Arm Position 1	9.13	-41.6	6.43
Arm Position 2	9.36	-40.1	8.33
Arm Position 3	10.39	-41.7	7.03
Arm Position 4	11.85	-37.7	4.88
Arm Position 5	8.94	-41.6	9.38
Arm Position 6	9.41	-41.1	4.66
Arm Position 7	9.23	-41.2	6.38

Summary

This set of examples has shown how the Varipose and XFDTD software products can be used together to analyze the performance of devices, in this case a cellular phone, in the dynamic environment of the moving human body. While this example focused on the changes to the radiation patterns, an analysis of the changes in the SAR or temperature distribution could also have been performed.