Gain enhancement of a microstrip array inserted inside a pyramidal horn

Enhancement the gain of a planar microstrip array by inserting the antenna into a short horn is discussed. It is shown that an asymmetric horn surface should be used in case of unbalanced-fed elements and a symmetric horn surface is suitable for balanced-fed elements. In both cases the gain is increased and the sidelobe level is decreased. An array of 2 × 2 elements is discussed, showing gain enhancement of 2-3 dB and sidelobe reduction of 5-8 dB.