Antenna characterization and determination of path loss exponents for 677MHz channel using fixed and portable digital terrestrial television

Abstract

This paper presents propagation measurements results using Integrated Services Digital Broadcast-Terrestrial (ISDB-T) to investigate the characteristics of 6MHz wideband Digital Terrestrial Television channel at 677MHz for fixed and portable reception. Empirical measurements were done at predetermined measurement points consisting of 21 radials for a total of 92 locations extending to 20 kilometers around the National Broadcasting Network (NBN) digital transmitter. Characterizations were conducted using antenna heights of 9m (fixed reception), 3m (fixed reception), and 1.5m (portable reception). Modulation Error Rate (MER), power received, field strength and delay profiles were captured to help characterize the channel in an urban area in and around Metro Manila at day time for temperatures ranging from 26 °C to 32 °C. Measured field strength was compared to NTC F(50; 90) curves. Polynomial fit using least square errors was used to plot the field strength coverage of NBN. For large-scale fading, it is observed that signal power conforms to Log Normal distribution. The study helped identify problem sites within the coverage. These are locations within the coverage area or at the outskirts of the coverage area where DTV signal is not received at all. A more accurate description of the DTT channel will lead to a better design of the parts of the Digital Television system from the network to transmitting system and receiving equipment. Path loss exponents computed for the three antenna heights can be helpful in developing empirical prediction models.