LINE-OF-SIGHT PATH CHARCTERISTICS

Free Space Path Loss orSpreading Loss:

• Assumes Ideal Path Conditions• No Actual Loss or Dissipation, just due to Spreading of the Signal Power as it Propagates away from Tx Antenna

LINE-OF-SIGHT PATH CHARCTERISTICS

Path Clearance and Antenna Heights:

• With a Proper Path Clearance, Path Loss under Normal Atmospheric Conditions would be just Lp

• Phase Reversal is Possible at Point C when Grazing Angle of the Secondary Wave is Small

• Signals Received thru Paths AB and ACB will Tend to Cancel Each Other when Paths AB and ACB differ by whole number of Half Wavelengths

• Proper Clearance >= 0.6 H1 at least(Preferably > H1)

LINE-OF-SIGHT PATH CHARCTERISTICS

Channel Fading:(below 10 GHz)• With Shorter Inter-Tower Distance, RSL remains Constant within +1 dB over long Periods of Time(Provided TX Level is kept Constant)

• For Extended Distances, RSL Normally Vary around a Nominal Median Range for Most of the Time, but, may Suddenly Drop by 10, 20, 30, 40 or even Higher value from the Median for a very Short time Intervals

• Deeper the Fade, Lesser Chances of its Occurrence and Shorter its Duration

LINE-OF-SIGHT PATH CHARCTERISTICS

MICROWAVE RADIO SYSTEM GAINDifference between the Nominal Tx Output Power and Rx Min Power to Ensure Necessary PerformancePt – Cmin= Gs >= Algebraic Sum of all Gains and Losses on the Path

MICROWAVE RADIO SYSTEM GAINSystem Gain Parameters

MICROWAVE RADIO SYSTEM GAINSignal Levels Relative to System Gains and Losses

Pt – Cmin= Gs >= Algebraic Sum of all Gains and Losses on the Path

MICROWAVE RADIO SYSTEM GAINFade Margin or Link Margin can be considered as a “fudge factor” in Gs equation to cope with non-ideal and hard to predict nature of Radio Wave Propagation

• Multi-path Loss•Terrain Sensitivity

For a Specified Annual System Reliability for an unprotected and non-diversity system, Fade Margin Fm is defined as (Solving Barnett-Vignant Reliability Equations):

MICROWAVE RADIO SYSTEM GAINFade Margin or Link Margin can be considered as a “fudge factor” in Gs equation to cope with non-ideal and hard to predict nature of Radio Wave Propagation

Example 13.2: (Use Equation 13.8, 13. 13, 13.14, and Table 13.3)

MICROWAVE RADIO SYSTEM GAINReceiver Threshold or Receiver Sensitivity is the required Minimum Wideband Carrier Power (Cmin) at the input of Rx that provides a usable baseband output

• Noise Power at the Input of Receiver

MICROWAVE RADIO SYSTEM GAIN

• C/N vs S/N : C/N is a pre-detection (before the FM Dem.) S/N ratio measured at RF or IF level inside a Rx whereas S?N is the Signal-to-Noise after the FM Demodulator.

• Noise Factor and Noise Figure: Figures of merit used to measure the deterioration of S/N as a signal passes thru a system

MICROWAVE RADIO SYSTEM GAIN

Example 13.4

MICROWAVE RADIO SYSTEM GAIN

Example 13.5