Electronic steering of antenna nulls for interference reduction

The paper reports on theory, tests and design of a low-cost broadband radio-frequency device that combines signals from two antennas to selectively null interfering signals. The theory and analysis of limitations pertain to both manual and adaptive null control devices. Tests illustrate cases in which nulling works well and those where propagation features limit null effectiveness. An important result of the tests is recognition that much work remains to be done to determine optimum antenna pairs for particular types of interference. An analysis section provides equations of general use for designing alternative implementations.