A small antenna with ultra-wideband characteristics

This paper proposes an approach of designing a small printed antenna that supports low power density, with the IEEE 802.15 standard suitable for high speed communication. The antenna´s radiation pattern is controlled by using reflector. Purpose of the work is to suppress radiated power from being absorbed into the body. S11 below -10dB in the frequency band is one of the most important targets for this proposal. The antenna was fabricated by using FR4 substrate in 21 × 25.5 mm with thickness of 1.6mm. The size of the proposed reflector was 60 × 40 mm with height of 10 mm. Size does not change even with an antenna. Two of the proposed antennas are disposed on two sides of the reflector, respectively, and a switch is used to control power supply to make the antenna which in free space be always powered. S11 in this state change to about -8.5 dB or less. Mutual coupling is less than -17.5dB. Front-to-back (FB) ratio is confirmed by evaluation when the reflector was used.