Antenna Systems & Technology - Winter 2011 - (Page 10)

FEATURE ARTICLE Troubleshooting in Mediumwave Multiplexing Antennas By Norbert Stangl, Head of Design & Engineering • Thomson Broadcast GmbH Even in the age In contrast to single frequency AM of satellite and the antennas, modern high performance digiinternet, there are tal multiplexing systems have much less some compelling tolerance against any faults in the radio reasons for using frequency (RF) equipment of the antenna. Mediumwave (MW) frequencies for Some examples of the type of faults broadcasting purposes. that arise in a multiplexing system will be Mediumwave broadcasting has a numshown in this article. These faults are usuber of distinct advantages, such as the ally not visible on the monitoring device possibility of broadcasting to distant tarof the antenna system, and consequently, get areas from inland TX-sites, the ability continuous inspection measures are the to reach a huge coverage area with one only means of ensuring smooth, longsingle site, the low cost, familiarity and term operation of the system. wide availability of MW receivers, and MW is independent from satellite and inSystem Layout ternet communication. A MW antenna system typically conNew digital standards are now opensists of the radiating elements, the matching up a lot of potential for classic AM ing network (and in case of directional technology. These include the trans- Figure 1. MW Diplexing Antenna Tuning System antennas, the power-splitting and phasing mission of FM-like audio quality, even network) and the RF feed line. In mulunder difficult reception conditions, the tiplexing systems, the network will be introduction of additional services by providing up to four dif- more sophisticated due to filter circuits, which have to be inteferent channels on the same frequency and, last but not least, a grated into the matching network accordingly. To illustrate the considerable reduction in the power needed to service a given principal design of such equipment, a network diagram of an coverage area. exemplary diplexing network is shown in Figure 2a. The filters, Economic optimization as well as reduced power levels in digi- necessary for the multiplexing operation, are highlighted in this tal MW broadcasting will have an impact on the layout of modern figure. A design example for this network is shown in Figure 2b. transmitting stations with the antenna system becoming a core As every MW station has its individual parameters, it has to component for achieving significant optimization. Multiplexing be emphasized that the antenna system, and in particular the antennas are becoming increasingly important, as one single ra- multiplexing and matching network, is always designed to the diation system can be used to broadcast several MW frequencies. specific requirements. Consequently, such a system is far away This solution the size and space required for the structure and from any standard design solution. Especially the application of avoids mutual interferences between different radiation systems. filters needs careful and detailed analysis of the network, in orHowever the technical performance has to be considered care- der to guarantee the performance regarding current and voltage fully and this is even more important for digital transmission. Figure 2a. MW Diplexing and Antenna Tuning Network Diagram (Multiplexing Filters highlighted) Figure 2b. MW Diplexing and Antenna Tuning Network Design (Multiplexing Filters highlighted) 10 ANTENNA SYSTEMS & TECHNOLOGY WINTER 2011 WWW.ANTENNASONLINE.COM http://WWW.ANTENNASONLINE.COM

Table of Contents for the Digital Edition of Antenna Systems & Technology - Winter 2011

Antenna Systems & Technology - Winter 2011
Editor’s Choice
Reducing Measurement Times and Improving Economic Competitiveness for Antenna and RCS Applications
Troubleshooting in Mediumwave Multiplexing Antennas
Design Considerations in the Selection of High Frequency Materials for PCB Base Station Antennas
Antennas
Distributed Antenna Systems
Wireless Communication
Industry News
Wireless Network Planning from the Desktop Using High Resolution 3D NEXTMap Digital Surface Elevation Data

Antenna Systems & Technology - Winter 2011