sh Telecom Technical Journal, 3, (2). cess Services. (prI-ETS 300 131). Swain, R. S. (1990) Digital Cordless Telecommunications - CT2, ETSI (1992a) DECT Services and Facilities Requirements Specifi- British Telecommunications Engineering, 9, (2), pp. 98-102. cation ETSI Technical Report. Swain, R. S. (1984) Cordless Telecommunications in the UK. In ETSI (1992b) Digital European Cordless Telecommunications Proceedings of the National Communications Forum XXXIII, Common Interface. (prETS 300 175-1 to 9). Chicago, USA, Sept. This page intentionally left blank Line of sight radio systems Jim Giacobazzi TeleSciences Transmission Systems Contents Microwave system path design considerations 50/3 Short haul and millimetre path design 50/7 50.3 Digital and analogue microwave systems 50/10 50.4 System specification and equipment design 50/14 This page intentionally left blank Microwave system path design considerations 50/3 50.1 Microwave system path design signal tends to travel slightly slower than the upper part of the considerations wavefront. This results in a slight downward curvature of the signal (Figure 50.2). For this case a K factor of 4/3 is used, meaning that if the microwave path is drawn as a straight line, the earth will A thorough understanding of the principles of microwave path appear flatter than normal, or will have a radius greater than normal. design is essential in the planning and engineering activities for A path design using 4/3 as the K factor would result in less lower microwave system. The operator of a microwave system should also height on each end of the path. However, a conservative design understand these principles if he is to evaluate the work of an approach will use a normal K factor of 1.0. engineering organisation designing his system. 50.1.1 Path clearance K=4/3 Microwave energy tends to travel in a straight line between micro- wave stations - hopefully, most of the time. Unfortunately, the system designer is faced with the unavoidable fact that we live on a round earth. Thus, the c