Beam sharpening of a range-angle-dependent pattern using non-uniform symmetric but integer frequency offset

A uniform inter-element frequency offset for a frequency diverse array (FDA) radar generates a range-angle dependent beam pattern that causes broadening of half power beam width (HPBW). Certainly, this broadening of the main beam is undesirable due to the fact that it decreases the maximum reachable range and at the same time it allows interferes to affect the target- returns. Therefore, it not only results in weakening the signal to interference noise ratio (SINR), but also does not facilitate to distinguish between targets that are very close in range. In this letter, a uniformly-spaced FDA with non-uniform integer frequency offsets has been proposed. The proposed design avoids the broadening of main beam and hence provides a better range resolution as compared to the previous designs. Likewise, symmetrical frequency offset selection scheme achieve better null depths than that of non-symmetric. The usefulness of the proposed method is validated in simulations.