Abstract An AWTSS is shown to be made up of an improved synthetic aperture radar (SAR) for generating radar maps with various degrees or resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter. The SAR consists, in effect, of four frequency-agile radars sharing quadrants of a single array antenna mounted within a radome on a "four axis" gimbal with a sidelobe cancelling subarray mounted at the phase center of each quadrant. Motion sensors are also mounted on the single array antenna to provide signals for compensating for vibration and stored compensating signals are used to compensate for radome-induced errors. In addition, a single processor is shown which is selectively operable to generate radar maps of any one of a number of desired degrees of resolution, such processor being adapted to operate in the presence of clutter or jamming signals.
In a monopulse radar system utilizing a four quadrant phased array antenna and a multi-channel radio frequency receiver having a separate channel fed by signals from each antenna quadrant and an auxiliary channel, a sidelobe canceller for nulling jamming signals received in the sidelobes of the four quadrant phased array antenna, such sidelobe canceller comprising: (a) a sidelobe canceling antenna array disposed at the center of each of the antenna quadrants; (b) means for forming monopulse sum and monopulse difference signals from signals received by the sidelobe canceling antenna array in each quadrant; (c) switching means for selecting, for further processing, either the monopulse sum or monopulse difference signals out of the monopulse sum and monopulse difference forming means; (d) means, following said switching means, for coupling the selected monopulse sum or monopulse difference signals to the auxiliary channel; and (e) means, following said coupling means, for modifying the selected monopulse sum or monopulse difference signals and applying such modified sum or difference signal to each channel in the radio frequency receiver.
Claim 2
Dependent Claim
172 words
In a monopulse radar system utilizing a four quadrant phased array antenna and a multi-channel radio frequency receiver having a separate channel fed by signals from each antenna quadrant and an auxiliary channel, a sidelobe canceller for nulling jamming signals received in the sidelobes of the four quadrant phased array antenna, such sidelobe canceller comprising: (a) a sidelobe canceling antenna array disposed at the center of each of the antenna quadrants; (b) means for forming monopulse sum and monopulse difference signals from signals received by the sidelobe canceling antenna array in each quadrant; (c) switching means for selecting, for further processing, either the monopulse sum or monopulse difference signals out of the monopulse sum and monopulse difference forming means; (d) means, following said switching means, for coupling the selected monopulse sum or monopulse difference signals to the auxiliary channel; and (e) means, following said coupling means, for modifying the selected monopulse sum or monopulse difference signals and applying such modified sum or difference signal to each channel in the radio frequency receiver.