MINIATURISED LOW FREQUENCY ANTENNAS INTEGRATED WITH BAND GAP STRUCTURES

The growth in mobile wireless communication systems has been rapid in recent years particularly for mobile telephone and network systems from 900MHz to about 6GHz. This has directly led to advances in technology such as the development of small multi-band antennas, compact wideband components and the application of frequency selective surfaces (FSS) and related electromagnetic band gap (EBG) materials. At frequencies below this such as the military communication bands at 30MHz, foliage penetrating radar at 110-200MHz, broadcast bands at 100MHz and 200MHz, deep space missions and satellite emergency beacons 100-400 MHz and TETRA at 400MHz, relatively little has been achieved mainly due to the large physical size involved at these frequencies. At these low frequencies monopole like antennas tend to be used and these represent single fault failures that are particularly crucial in space and military applications. The purpose of this application is to design miniaturised low profile antennas and integrate them over high impedance EBG/FSS surfaces (HIS) for long wavelength applications providing a platform independent antenna installation. The antennas would not only be small but also able to be integrated onto many vehicular platforms independent of interactions with the vehicle surface. The main challenge is to develop antenna and HIS structures that are physically much smaller than the wavelength and yet effective in their application in small EBG array configurations. To this end both passive and active lumped circuit element components will be incorporated into novel antenna and HIS surfaces to reduce their size. The performance of small arrays of HIS elements will be studied to improve their performance particularly when integrated with miniaturised low frequency antennas.