Abstract: Apparatus for electronically steering a null in a total radiation-reception pattern provided by a set of angularly disposed (preferably substantially-orthogonally-positioned RF) antennae, uses: first and second N-bit binary attenuator subsystems for modifying the amplitude of a signal provided by an associated one of the pair of antennae, responsive to an associated one of first and second control data signals; a set of look-up tables, receiving null-angle input data, provide the first and second signals as the sine and cosine, respectively, of the input null-angle; and the output of the first and second attenuator means are then combined to provide an output signal in which contributions arriving at the set of antennae substantially at the null angle are substantially reduced. The signal combiner may include at least one polarity reversal circuit, possibly including a transformer and/or switch means, to accommodate nulling to all four quadrants of a full circular response pattern.

Abstract: A frequency shift keying system for transmitting a signal which is a function of supplied data, includes first and second frequency generators producing first and second frequencies which differ in value by an amount which is a function of the maximum baud rate of the data. A counter is responsive alternately to one and the other of the two frequencies supplied thereto as a function of the data values for alternately counting up and down between values which differ by some given amount. The counter output in analog form is the transmitted signal. This system is particularly adapted to minimum frequency shift keying.