Adaptive antenna arrays for HF radio beamforming communications

摘要

HF aerials for ship-shore communications consist of spaced dipole arrays, 22. By appropriate adaptive phasing very high gain HF aerials are formed. On transmission a feedback signal is required from the receiver 24, otherwise similar algorithms are used to control the beamforming. A random phase algorithm (Fig 7) has been devised for the phases applied to the array aerials, operating in four tranches of 100 iteration steps with progressively reduced maximum phase variation. The initial step has a phase variation in the range +/-180 DEG . The algorithm has the advantage that there is a high probability that a relatively high gain beam will be immediately formed in the required direction and thus the system can quickly settle towards a direction where the signal is weak. When in the transmit mode the receiver returns a signal to the transmitter giving the step number of the random phases which gives the maximum received signal. A decision tree algorithm may be used in one direction of communication, (Fig 4). IMAGE