New Correction Factor for High-precision Open-site Attenuation Calculation (4)

Abstract

The papers that we have given so far for precise measure­ ments and theoretical analysis values of site attenuation for open sites have all been for horizontal polarization. Good agreement within about 1 dB has been obtained between actual measurements and calculated values. The individual terms influencing the attenuation were cumulatively added to the formula to account for all factors involved, and we think that we have achieved sufficient accuracy for practical purposes. This time we have extended the calculation to make it suitable for vertical polarization. The agreement of the measured and calculated height pattern of the attenuation value at the receiving point was studied in the same manner as for horizontal polarization and excellent agreement was obtained. Introduction A report has previously been made on the precise measure­ ments of site attenuation of horizontally polarized waves and on the theoretical analysis of the results. This time, analysis was made on the site attenuation of vertically polarized waves using the same analysis method. Good agreement was obtained between the calculated and actually measured values. Especially the height pattern of the attenuation value at the receiving point, on which we have concentrated for some time, showed good agreement between the calculated and measured values in the same manner as for the horizontally polarized waves. Our previous report took the frequency at which the retlection coefficient (T) of the antenna measured from the cable end becomes minimum as the resonant frequency of the tuned dipole antenna. However measurements of the site attenua­ tion at this freqiency showed us that this frequency is not appropriate for use as the tuned frequency. * I At present the resonant frequency of the antenna is found by a cut and try method. These measurements were conduct­ ed provisionally with a half wavelength dipole antenna, so there was no need to measure the resonant frequency. 1. Calculation Procedure Calculation was made on using terms for all e ffects between the transmitting and receiving antennas, as shown in Fig. 1. As shown in the Appendix, the current distribution of tuned dipole antenna was assumed to be a sinusoidal distribution.*2 1.1 Site attenuation of horizontally polarized waves The interrelations of antennas was considered as shown in Fig. 2. *1 : We had assumed that this method was not truly appro­ priate from the results of our calculations on antennas, but we dared to try to determine antenna resonance frequency using this method of measurement because no other appropriate method was found. We realized that this frequency is inappropriate, though, because of inconsistency between the measured and calculated values of height pattern. Our analysis of the tuned dipole antenna will be reported at another opportunity. CH2294-7/86/000-0354 $01 .0 0 (6 )l 986 IEEE 354 *2 : Further detailed analysis on antenna current distri­ bution. Mr. T. Kawana et al. reported 2) an analysis using the moment method. It shows that if the current distribution on the antenna is saaumed to have sinusoidal distribution the maximum amplitude difference is only about 20%, and that the difference was less than 5% for the current integrated over the entire antenna length (equivalent to antenna's effective length). This 5% difference falls within the range of uncertainty in our site attenuation measurement. 3)S IT E R T T E N U R T IO N C d B 3 SESSION 5A Fig. 1 Scematic diagram of radiated and re-radiated waves included in our calculations.