A compact ultra-wideband spiral helix antenna for in-body communications

An ultra-wideband and compact spiral helix antenna is designed for transmitting or receiving signals to or from human body. The antenna in free space covers the frequency band of 3-10 GHz with input impedance of 200 ohms. The designed antenna is embedded in a high dielectric material of distillated water to provide wave impedance matching to human body tissues. The frequency band is adjusted to 300-1000MHz. The embedded antenna is optimized with 30 ohms input impedance in the proximity of 4-5 cm to the chest of a human body model. Electromagnetic computation is conducted by including frequency dependent dispersive materials of human tissues. Due to the directive radiation pattern of the antenna, the wave penetration inside human body is improved. The embedded antenna provided almost circular polar pattern for whole operating bandwidth. The average energy of the penetrated wave in different depths inside the chest are presented.