The Index Modulation (IM) approach adds an extra signal modulation dimension by utilizing sub-carrier index domain, that is in addition to the traditional IQ domain. Frequency diverse array (FDA) technology is rapidly developing as a new technique for Radar systems. In this letter, a novel transmitter architecture for FDA, combining index modulation concept with FDA, namely IM-FDA, is presented. Compared with conventional frequency diverse arrays (CFDAs), the proposed architecture offers thumbtack-like beampatterns which can decouple the range and angle dependence, an issue existing in CFDA. An additional benefit is that apart from sensing target location, information can be conveyed to the targets through the selected frequency offset indices in the proposed scheme. The transmitter architecture is elaborated along with its design details and the efficacy of the proposed architecture is validated via numerical results for the transmit beampattern by comparison with CFDA and random frequency diverse array (RFDA).