Patent ID: 6356233
Filing Date: 2002-03-12
Classification: H01Q

Abstract:
A method for calibrating the active elements of an array antenna, said array antenna being for transducing electromagnetic signal between unguided radiation and a guided transmission path, and including:a beamformer including at least one guided-wave common port and at least N output ports associated with said common port; a beamformer control computer coupled to said beamformer, for transducing signals therewith, and for forming beams based upon at least one of beamformer (a) amplitude and (b) phase transfer functions; a plurality of N radiating elements arranged in an array, each of which radiating elements is capable of transducing electromagnetic signals with its own elemental port; a plurality of 2P calibration ports, where P is less than N; P directional couplers, each of said couplers including first, second, third, and fourth ports, for coupling signal from said first port to said second and third ports and not to said fourth port, and from said second port to said first and fourth ports, but not to said third port, each of said P directional couplers having its first port coupled to one, and only one, of said calibration ports, its second port coupled to another one, and only that one, of said calibration ports, its third port connected to a kernel one, and only said kernel one, of said N radiating elements, and its fourth port coupled to one, and only one, of said N output ports of said beamformer, whereby Nâˆ’P=R non-kernel ones of said radiating elements lack a guided path to a directional coupler, and R ports of said beamformer are not connected to one of said directional couplers; a guided-wave connection between each of said R ports of said beamformer which are not connected to one of said directional couplers and a corresponding one of said R non-kernel radiating elements; and at least one of (a) an active amplifier and (b) a controllable phase shifter associated with at least some of the paths defined between said guided-wave common port and said at least N output ports associated with said common port of said beamformer; said method comprising the steps of: applying a directional coupler calibration signal to a first one of said calibration ports, for thereby transmitting signal to a first port of a first one of said directional couplers; in response to said step of applying of a directional coupler calibration signal, receiving returned directional coupler calibration signal at a calibration port coupled to the second port of said first one of said directional couplers; comparing the amplitude and the phase of said returned directional coupler calibration signal with the corresponding amplitude and phase of said calibration signal to establish a calibration transfer value for said guided-wave connection between said first one of said directional couplers and its associated calibration ports; one of (a) applying beamformer calibration signal to said common port of said beamformer and extracting corresponding beamformer calibration signal from that calibration port coupled to said second port of said first one of said directional couplers and (b) applying beamformer calibration signal to that one of said calibration ports coupled to said second port of said first one of said directional couplers, and extracting corresponding beamformer calibration signal from said beamformer common port, to thereby determine at least one of said amplitude and phase transfer between said common port of said beamformer and said fourth port of said first one of said directional couplers; from said calibration transfer value and from at least one of said one of said amplitude and phase transfer between said common port of said beamformer and said fourth port of said first one of said directional couplers, determining at least one of the amplitude and phase characteristics of that signal path extending from said common port of said beamformer to said fourth port of said first one of said directional couplers; and adjusting said beamsteering control computer by updating the parameters by which said control takes place by updating the value of said one of said amplitude and phase characteristic of that signal path extending from said common port of said beamformer to said fourth port of said first one of said directional couplers.