The merits of symmetrical and diagonally-symmetrical monopulse slot arrays

The designer of monopulse slot arrays has to make a selection between either a symmetrical configuration where the quadrants are mirror images of each other, or a diagonally-symmetrical configuration where quadrants are mirror images of their respective diagonal counterparts. The symmetry of the former guarantees good difference mode pattern performance over an appreciable frequency range, but non-uniform inter-element spacing in the E-plane may give rise to sum pattern distortion. On the other hand, small variations in the off-centre-frequency input impedance for the sub-arrays of diagonally-symmetrical arrays may affect their difference mode performance. This paper presents a study on the advantages acid disadvantages of using the two different configurations by theoretically assessing the performance of a number of representative examples