Directivity-controllable antenna system

A directivity control antenna system comprising:

• an antenna unit having first through fourth dipole antennas in which two-terminal variable reactance circuits are respectively connected to a pair of antenna elements and an impedance adjusting capacitor is connected between feed terminals of said pair of antenna elements;
• a first signal combiner connected to said first and second dipole antennas of said first through fourth dipole antennas, which are disposed opposite to each other, by feed lines of equal length with respect to said first and second dipole antennas for combining signals from said first and second dipole antennas;
• a second signal combiner connected to said third and fourth dipole antenna of said first through fourth dipole antennas, which are disposed opposite to each other are perpendicular to said first and second dipole antennas, by feed lines of equal length with respect to said third and fourth dipole antennas for combining signals from said third and fourth dipole antennas;
• tuning control means for supplying a plurality of DC voltages which are different from each other;
• changeover control means coupled to said tuning control means for selectively supplying said plurality of DC voltages from a first through a fourth output terminal thereof to said first through fourth dipole antennas for control of the reactances of said two terminal variable reactance circuits of said first through fourth dipole antennas so as to control the directivity of said antenna system, said changeover control means being also coupled to said first and second signal combiners for selectively passing output signals from said first and second signal combiners to a fifth and a sixth output terminal thereof;
• and a third signal combiner coupled at two input terminals thereof to said fifth and sixth output terminals of said changeover control means for outputting, to a receiver, output signals of said first or second signal combiner or combined output signals of said first and second signal combiners, wherein connection of said first and second signal combiners to said third signal combiner via said changeover control means made is by feed lines of equal length with respect to said first and second signal combiners.