Scan gain enhancement in phased arrays by element pattern synthesis

The usefulness of element pattern synthesis is examined for microstrip patch arrays, by using a composite patch, radiating the TM ₁₁ and TM₂₁ mode patterns. The combined pattern is an asymmetric one, with a peak near midway between the broadside and endfire directions. Its location in the azimuthal plane is scanned readily by a single phase shifter. The element pattern has also a null in the direction opposite to the peak that reduces the grating lobe beam for large scans. The performance of phased arrays using such an element is studied and compared with standard patch arrays. The results confirm the expectations in gain enhancement and improved array pattern shape. To examine the performance experimentally, a 7-element array with triangular lattice was fabricated and tested. For large beam scans the array gain is found to be equivalent to the gain of a 19-element array using the TM₁₁ mode patches. Both arrays have similar surface area, bu the composite 7-element array has a considerably simpler beam forming network, due to its smaller size