It has been shown over several decades of radar research that the exploitation of diversity in a number of domains such as space, frequency, time, polarization, and, recently, waveform can provide increased agility, flexibility, reliability, and capabilities to the radar system. However this is often achieved either through efforts in system design, increased hardware complexity, or by employing additional resources. In the frequency diverse array (FDA) the subsequent antenna elements are fed with stepped discrete frequencies. So a range-angle dependent radiation pattern is made possible. It is possible to apply different frequencies with different patterns to the elements of FDA to achieve different radiation pattern. In this paper, a frequency diverse array with non-uniform inter-element frequency OFFSET called quadratic-FDA has been proposed, that its variation is a function of physical distance of elements from the first element. To produce the coefficient of the frequency OFFSET two Frequency OFFSET generators has been proposed. In The first proposed method uses linear distance as a input of function and the second one uses multiples of the roots of the Chebyshev polynomial. The proposed strategy provides a non-periodic beampattern, with a maximum that can be steered in space by selecting appropriate excitation weights of the antennas. This single-maximum beampattern, in contrast to multiple-maxima beampattern of the other forms of FDA, can help to further reject range-dependent interferences, causing improved SINR and increased detectability.