Propagation Characteristics of Distributed Transmission with Two Synchronized Transmitters

The distributed radio transmission scheme can improve signal coverage, as the single frequency network (SFN) for DTV broadcasting. However, the propagation characteristics of the distributed transmission in SFN have to be studied carefully for they are different from conventional single transmission cases. In this paper, the field measurement carried out in a rural SFN with two synchronized transmitters is reported. It is found that, on the one hand, the radio signal coverage of the distributed transmission scheme has been distinctly improved with the total transmitted power by multi-transmitters as same as compared single transmitter system; and, on the other hand, the power delay profile (PDP) has shown rather different features than the single transmission cases, in which there are long delay "echoes" and could not be modeled simply by exponential decays because of the existence of distributed transmitters. The parameter called "transmission gain" has been introduced in order to extend the concept of "path gain" to the distributed transmission cases and, the tapped delay line is used to model the average PDP in the distributed transmission cases