Patent ID: 6377212
Filing Date: 2002-04-23
Classification: G01S

Abstract:
Radar apparatus comprising:a slotted planar waveguide array or phased array antenna having a plurality of antenna elements from which a plurality of output signals can be derived which have different gain characteristics; means for deriving a first output channel, having a relatively high gain characteristic with a main lobe, from a first set of the plurality of antenna elements; means for deriving a second output channel having a gain characteristic different from the gain characteristic of the first output channel, the second output channel being derived from a second set of the plurality of antenna elements, at least some of the second set of antenna elements being common to the first set; means for deriving a third output channel having a gain characteristic different from the gain characteristics of both the first and second output channels, the third output channel being derived from a third set of the plurality of antenna elements, at least some of the third set of antenna elements being common to the first set, the second set or both sets; a guard antenna having a wide beam of relatively uniform gain which covers far out and intercardinal regions; means for deriving a guard antenna output channel which has a gain characteristic different from the gain characteristics of the first, second and third output channels; a receiver associated with each output channel, for providing respective first, second, third and guard antenna output signals; and discriminator means connected to each receiver for receiving each output signal and for forming a ring difference signal from the second and third output signals, and for combining the ring difference signal with the guard antenna output signal to form a side lobe suppression signal having a gain characteristic derived from the gain characteristics of the second, third and guard antenna output channels, the discriminator determining whether the direction from which a signal is received by the antenna is in the main lobe of the first channel by comparing the first output signal with the side lobe suppression signal.