The advance of wireless communications brings in various schemes of wireless digital communication technology. In the field of digital radio broadcasting, several specifications have been proposed, such as Eureka-147 and DRM (Digital Radio Mondiale). These systems require new spectrum assignment, which is a huge cost due to depletion of the available spectrum. Therefore, the IBOC (In-Band On-Channel) system has been developed to work in the same band with the conventional analog radio and broadcasting digital signal simultaneously. In this paper, the function and algorithm of the HD Radio FM digital radio broadcasting system are discussed. Content includes data format allocation, constellation mapping, and OFDM modulation of the transmitter; timing synchronization, OFDM demodulation, integer and fraction carrier frequency (ICFO & FCFO) estimation, and channel estimation of the receiver. When implementing the system on the FPGA based hardware platform, both the theoretical and the practical aspects have been considered to reach the available hardware resource.