Directional switched beam antenna
OwnerLotfollah Shafaiinventor
Life of this patent
Estimating the term…
Abstract
A switched beam antenna comprising several spiral arms with a common axis of rotation and respective inner ends angularly spaced around a common circle generates high gain directional beams at an angle away from the antenna axis. Beam scanning is accomplished by rotating the feed to the arms by means of a commutator circuit. Intermediate beams may be generated by feeding two adjacent antenna terminals simultaneously but with an appropriate phase shift. A comparator may be provided to compare signals from several arms and select the arm yielding maximum signal strength.
Claims23
An antenna comprising a plurality of spiral conductive arms having a common axis of rotation and their respective inner ends spaced angularly about such axis, and means for communicating radio frequency signal via one end of at least one, but not all, of said arms, respective outer ends of the spiral arms defining a periphery of the antenna, each arm having a plurality of turns, each turn intersecting a corresponding one of a plurality of concentric radiation mode circles, the respective circumferences of the radiation mode circles being integer multiples of a predetermined operating wavelength for the antenna, said intersecting takes place in a corresponding one of a plurality of active regions wherein radiation of the corresponding mode occurs when the antenna is communicating radio frequency signals at said predetermined operating wavelength, the winding rate of each antenna arm being such that each turn subsequent to the first turn has an electrical length substantially equal to the electrical length of a preceding turn plus an integer multiple of said wavelength.
An antenna as claimed in claim i, wherein the end of said at least one of said arms opposite to said one end, and the corresponding ends of remaining arms, are open-circuit.
An antenna as claimed in claim wherein ends of remaining arms corresponding to said one end are open-circuit.
Dependencies are inferred from the claim text.