Polarization Diversity - Variable Polarization Technology and the Mobile Broadcasting Environment
by Jay Martin, Director, Broadcast Sales & Business Development
Today, broadcasters are operating in one of the most competitive markets in the history of broadcasting. The means of distribution of content to the market seem endless with the traditional means of information dissemination appear somewhat obsolete. Broadcasters are in the midst, or have just finished making a significant investment in their future with the build-out of digital facilities in the form of DTV, ISDB-T, DVB-T and now Mobile DTV is here. As a result, broadcasters should view this time as one of great opportunity and pursue this market aggressively for the mobile environment can be uniquely serviced by the broadcaster and is an environment that is not addressed effectively by cable, satellite or cellular networks.
The North American model for broadcasting has traditionally been one in which the individual stations own their own tower, their own transmitter and their own antenna array. The European model for broadcasting has been such that most broadcasters in a given market utilize a common broadband array and the LATAM model has been a mix of both single frequency and broadband arrays.
The modification to the ATSC standard (8-VSB) to AVSB or ATSC-MH, the current DVB-T standard and the ISDB-T standard all support delivery to mobile devices. Not only is the mobile market a market that is relatively untapped but it is a market that is exploding in size and is a market that could be uniquely served by the broadcaster delivering local, high quality content with no bandwidth constraints. What will it take and how does the broadcaster rationalize the investment in new passive RF technology? What additional requirements are there when considering delivery to a mobile receiver that were not a factor in the system design when considering delivery to a fixed receiver? Now that the modulation schemes all support delivery to a mobile platform, the passive RF systems needs to be upgraded to support this with the most notable change being the need for polarization diversity. This paper will focus the unique RF characteristics of the mobile environment and what is needed to support effective and robust transmission to this. In particular, polarization diversity will be explored and options on how to obtain polarization diversity from a transmission system standard will be discussed. The focus will be on broadband master arrays that are both financially rational and future-proof.
