A dual spiral antenna for Ultra-wideband capsule endoscope system

In this paper, a dual spiral antenna for ultra-wideband capsule endoscope system is proposed. Since a capsule endoscope system which transmits real-time image data in the body should have ultra-wideband characteristic, an ultra-wideband antenna is suitable for this system. When an antenna is used as capsule endoscope system, a small sized antenna is required because capsule is small enough to be swallowed. For these two conditions, the proposed antenna has dual resonance structure which is composed of two different spiral elements and single feed wire connects these two elements. The bandwidth of the proposed antenna is 411~600 MHz (189 MHz) for VSWR<2 which means the fractional bandwidth of 37.8% and it has isotropic radiation pattern. The height of the proposed antenna is 7 mm and diameter is 10 mm. Because of ultra-wideband characteristic and small size, the proposed dual spiral antenna is suitable for ultra-wideband capsule endoscope system.