Combined Antenna Systems for Assault Amphibian Use

Monopole and dipole antennas have been determined to radiate most efficiently when the size of the antenna is proportional to the frequency being transmitted or received, i.e. one-quarter, one-half or one wavelength. As the operating frequency is varied from that ideal frequency nulls begin to develop which threaten the integrity of the communication link. Experience has shown that small excursions (+ 50% of the resonent frequency) can be achieved without degrading performance by use of matching devices. But, larger bandwidths such as 30 to 90 MHz are normally accommodated by active high impedence tuning devices and couplers. Experience has also shown that antennas which are located in close proximity to each other tend to limit each others performance unless electrical isolation on the order of 30 dB is achieved. Finally, antenna array performance is best achieved by reducing the potential for intra antenna reaction and complicity. This investigation will evaluate new low impedance passive broadbanding techniques which minimize array complexity, maximize intra antenna isolation to produce a low profile high performance vertical antenna array which supports two transceivers and operates in the 30 to 90 bandwidth.