Fig. 4.

Comparison of the simulated SAR distributions for three 8-channel bow tie dipole antenna configurations and a total input power of 400 W (50 W per antenna). (a-b) Bow tie building block at 300 MHz with dimensions (150 × 70 × 40) mm³, (c-d) bow tie building block at 500 MHz with dimensions (150 × 70 × 40) mm³ and (e-f) a smaller sized (70 × 40 × 20) mm³ bow tie building block at 500 MHz. The local SAR hotspot size in the center of the phantom was significantly reduced at 500 MHz. A reduction in the length of the dielectric at 500 MHz (e-f) yielded smaller hotspot dimensions along the main axis of the bow tie antenna. (g) Comparison of the normalized point SAR derived from electromagnetic field simulations along a line from the surface to the center of a cylindrical phantom for three 8-channel arrangements of the building blocks. For all configurations the antenna building blocks are driven in phase (Ch1-8 = 0°) to generate a hotspot in the center of the phantom