Microwaves Part 2

Free-space loss

The loss between two antennas unaffected by the earth

Fading

refers to the variation in the signal strength at the receiver input

Fading

cased by changing atmospheric and propagation conditions and the shape of the path geometry itself

refers to the constant variation in the received signal level due to the small signal level due to the small variations in the point index

Diffraction Fading

Beam Fading

Multipath Fading

Blackout Fading

Rain Fading

types of fading

Atmospheric Absorption

the main causes of absorption loss are water vapor and oxygen

Radio Attenuation

the main contributor in frequency range used by commerical radio links

Diffraction Fading

the redistribution of energy within a wavefront when a wave encounters obstructions

Path Profile

a graphical representation of the path over which the microwave signal would travel between the two ends of a MW link

Grazing Line of Sight

Conditions when the light of sight between two antennas just clears a dominant obstacle

Dominant Obstacle

is the point in path profile with the least clearance from the direct ray of the MW link

Fresnel Zones

defined as an ellipsoid surrounding the MW LOS where the interference is always constructive

Fresnel Zones

the amount of clearance is generally described in terms of _______

Multipath Fading

occurs when the radio signals travel in more than one path and arrive at the receiver at different times

Space diversity

is used to counter multipath fading

Rayleigh Fading

multipath fading is sometimes called

Flat Fading, Frequency Selective Fading

multipath effects can result to ______ in narrowband systems and ________ in wideband systems

Flat Fading

a non frequency dependent form of fading

shorten distance between sites, path diversity

solutions for diffraction fading

Frequency Selective Fading

also known as dipersive fading

intersymbol interference

frequency selective fading can also be caused by

Slow Fading

variation in signal amplitude that changes slowly with time

Fast Fading

refers to the variation in the signal amplitude that changes raidly with time

Link Budget Analysis

performed to determine the performance of a link

Power Budget

adding the various gains and loser over the path from the transmitter output module to the receiver demodulator input is called the __________

Link Budget

used to calculate fade margin which is used to estimate the performance of the radio link

Transmit Power

usually a few to several watts, expressed in dBm

Branching Loss

refers to the loss in the multiplexer circuit

Branching Unit

is a generic term used to describe the circuitry that interfaces the antenna to the receiver

Feedline Loss

is the attenuation or reduction in RF power that occurs as a signal travels through a cable between the transmitter or receiver and the antenna

Effective Radiated Power (ERP)

refers to the amount of power emitted by the antenna in the direction of the maximum antenna gain

Received Signal Level

the amount of power that enters the front end of the receiver

Receiver Threshold

the minimum wideband carrier power at the receiver input that will provide a usable baseband output

receiver sensitivity

receiver threshold is also called this

Noise Power, Noise Factor, Noise Figure

figures of merit used to indicate how much the signal to noise ratio deteriorates as signal passes through a circuit

Fade Margin

considers the non idea and less predicable characteristics of radio wave propagation

Barnett-Vignant Reliability Equation

considers the non ideal and less predicable characteristics of radio wave propagation such as multipath loss and terrain sensitivity

System Gain and Minimum Transmit Power

the difference between the nominal output power of a transmitter and the receiver threshold