TECHNICAL FIELD

The disclosure relates generally to the field of communications, and more particularly to a phased array antenna.

BACKGROUND

A phased array, or electronically scanned array, is a controlled array of antennas that creates a beam of radio waves which can be electronically steered to point in different directions without moving the antennas. In an array antenna, the radio frequency current from the transmitter is fed to the individual antennas with the correct phase relationship so that the radio waves from the separate antennas add together to increase the radiation in a desired direction while cancelling to suppress radiation in undesired directions. Directional regions of high gain, referred to as “beams,” are formed by shifting the phase of the signal emitted from each radiating element to provide constructive and destructive interference to steer the beams in a desired direction. The relative amplitudes of the signals radiated by the individual antennas determine the effective radiation pattern of the array. A phased array may be used to point a fixed radiation pattern, or to scan rapidly in azimuth or elevation.

SUMMARY

In accordance with one example, a phased array antenna is provided that includes an array of antenna elements having a beam with a boresight direction. A plurality of phase shifters are responsive to commands to adjust phases of a plurality of radio frequency (RF) signals communicated with the array of antenna elements. A controller provides the commands to the plurality of phase shifters. The provided commands are used by the plurality of phase shifters to direct the beam within a range of scan angles relative to the boresight direction. A plurality of amplifiers amplify the plurality of signals. Each of the plurality of amplifiers is coupled to an antenna port of the array of antenna elements and has a performance characteristic that depends on antenna port impedance at the antenna port. The antenna impedance varies with a scan angle of the beam within the range of scan angles, and the amplifiers are configured such that a maximum of the performance characteristic is achieved at a value of the antenna port impedance that corresponds to a particular scan angle within the range of scan angles that differs from the boresight direction.

In accordance with another example, a method is provided for implementing a phased array antenna having a boresight direction. A scan angle within a defined range of scan angles is selected for the phased array antenna such that the selected scan angle is different from a scan angle associated with the boresight direction. An antenna port impedance associated with each of a plurality of antenna elements comprising the phased array antenna varies with the scan angle of the phased array antenna. A plurality of amplifiers are each coupled to an antenna port of one of the plurality of antenna elements. Each of the plurality of amplifiers is configured such that a maximum value for a performance characteristic of the plurality of amplifiers is achieved when an impedance at the antenna port corresponds to the selected scan angle.

In accordance with yet another example, a phased array antenna includes an array of antenna elements having a beam with a boresight direction. A first set of phase shifters is responsive to commands to adjust phases of radio frequency (RF) signals received at the array of antenna elements. A second set of phase shifters is responsive to commands to adjust phases of transmit signals for transmission by the array of antenna elements. A controller provides the commands to the first set of phase shifters and the second set of phase shifters. The provided commands are used to direct the beam within a range of scan angles relative to the boresight direction. A first set of amplifiers amplifies the signals received at the array of antenna elements. Each of the first set of amplifiers is coupled to an antenna port of the array of antenna elements and has a first performance characteristic that depends on antenna port impedance at the antenna port. The antenna impedance varies with a scan angle of the beam within the range of scan angles, with a maximum of the first performance characteristic achieved at a first value of the antenna port impedance that corresponds to a first scan angle that differs from the boresight direction. A second set of amplifiers amplifies the transmit signals to be transmitted by the array of antenna elements. Each of the second set of amplifiers is coupled to an antenna port of the array of antenna elements and has a second performance characteristic that depends on antenna port impedance at the antenna port with a maximum of the second performance characteristic achieved at a second value of the antenna port impedance that corresponds to a second scan angle that differs from each of the boresight direction and the first scan angle.

