Design and implementation of the baseband transceiver for the HD radio AM system

In recent years, the spectrum resource has become a more and more important consideration for the designs of wireless communication system. Therefore, Hybrid In-Band On-Channel (HIBOC) broadcasting system has been proposed as a composite solution to transmit digital and analog amplitude modulation (AM) signals in the conventional AM band. This system has been adopted by US as a digital radio broadcasting standard, and the specification is named as HD Radio AM. Although the modulation scheme in this standard is the Orthogonal Frequency Division Multiplexing (OFDM) which has been widely applied to various digital communication systems, the receiver architecture could not be the same as the conventional OFDM receiver design owing to the overlapping spectrum between the analog and digital signals. In this paper, a high-pass filter is employed to improve the performance of the symbol timing detection. In a fading channel, the channel response must be estimated before canceling the interference of the analog AM signals. Besides, 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. Simulation results show that the proposed scheme can keep good system performance.