ADTRAN 6000 Series System Manual

Also see for TRACER 6000 SERIES: User manual

Contents

ADTRAN 6000 Series System Manual Manual pdf 18 page image

Section 2 Microwave Path Engineering Basics TRACER 6000 Series Integrated System Manual18 Copyright © 2005 ADTRAN, Inc. 612806420L1-1FFigure 1 illustrates a wireless link configuration containing all the parameters necessary for the powerbudget analysis.Figure 1. Example Microwave Path with ParametersThe following sections further discuss the power budget analysis and its components.Antenna GainActual transmit and receive antenna gain values depend strictly upon the physical characteristics of theantennas installed for each link. In other words, the size of the dish determines the antenna gain. Using aparabolic dish antenna results in the best performance. Antenna gains are specified in terms of decibels ofgain referenced to an isotropic source (dBi). An isotropic source is a hypothetical antenna having equalradiation in all directions. The equation for calculating gain over isotropic radiation iswherek dish efficiency factor (usually 0.55)λ carrier wavelength (c / f)D dish diameterThe dish efficiency factor (k) is used to estimate how efficiently the dish reflector passes energy to thefeedhorn. The “standard” factor is 0.55 (measured performance of prime-focus dishes with a pyrimidalwaveguide feedhorn with no aperture blockage). Other dishes and feedhorn designs may have better orworse efficiency. Table 1 on page 19 (standard) and Table 2 on page 19 (metric) provide gains using a 0.55dish efficiency factor. Table 3 on page 19 (standard) and Table 4 on page 19 (metric) provide gains using a0.40 dish efficiency factor. Dish manufacturers can provide gains for specific types of antennas.The carrier wavelength (λ) and dish diameter (D) can be metric or standard units ofmeasure. Use the same unit of measure for both variables. For example, a carrierwavelength of 0.124 meters requires a dish diameter in meters as well.G T G Rd, LPP T P RλLLG 10 log k π D⋅λ------------⎝ ⎠⎛ ⎞ 2⋅⎝ ⎠⎜ ⎟⎛ ⎞⋅= (dBi)