Fig. 1. Cylindrical mechanical antenna structure based on electret material.

Fig. 2. Antenna model with multilayer electret film: (a) Single layer; (b) double layers.

Fig. 3. Calculation diagram of magnetic field of signal receiving point along X axis.

Fig. 4. Schematic diagram of magnetic field calculation when signal receiving point is distributed in X-Y plane.

Fig. 5. Calculation diagram of magnetic field generated by cylindrical antenna.

Fig. 6. Change of magnetic induction intensity B with distance D (single cylinder): (a) R = 0.55 m, H = 0.1 m; (b) R = 1 m, H = 1 m.

Fig. 7. Variation of error E with distance D: (a) Single cylinder; (b) double cylinder.

Fig. 8. Relationship of magnetic induction intensity and error to ratio at the same signal receiving point: (a) Single cylinder; (b) double cylinder.

Fig. 9. Relation between error and ratio at signal receiving points of different distance: (a) D = 5.5 m; (b) D = 10 m; (c) D = 50 m.