In this paper, we investigate the impacts of frequency increment errors on frequency diverse array (FDA) multiple-input and multiple-output (MIMO) radar in adaptive beamforming and target localization. Since a small frequency increment, as compared to the carrier frequency, is applied between the transmit elements, FDA MIMO radar offers a range-dependent transmit beampattern to suppress range-dependent interferences and thus yields better direction-of-arrival (DOA) estimation performance than conventional MIMO radar. But the frequency increment errors will degrade FDA MIMO performance such as adaptive beamforming and target localization precision. In adaptive transmit beamforming analysis, we analyze the FDA MIMO radar beampattern mainlobe offset in range dimension, angle dimension and signal to interference and noise ratio (SINR) performance under different frequency increment error cases. While for the target localization investigation, the performance analysis is based on an explicit expansion of the estimation error in the signal subspace and frequency increment error matrix. Simulation results show that the impacts of frequency increment errors are mainly on the range dimension, i.e., the range offset of mainlobe in beamforming and range estimation in target localization, especially for large frequency increment errors. 
Impact of frequency increment errors on frequency diverse array MIMO in adaptive beamforming and target localization