07-11-2012, 03:19 PM
MICROWAVE REPEATERS
MICROWAVE REPEATERS.doc (Size: 696 KB / Downloads: 115)
NOISE IN REPEATER
THERMAL NOISE
– GENERATED BY THE ELECTRONIC CIRCUIT
– INDEPENDENT OF LOADING
INTERMODULATION NOISE
– DUE TO NON-LINEARITY
– VALUE IS AFFECTED BY LOADING
RF HETERODYNE REPEATER
AMPLIFICATION AT THE CARRIER FREQUENCY
MOST EXPENSIVE TYPE OF REPEATER (SELDOM USED)
PROBLEMS WITH FILTER SELECTIVITY AT MICROWAVE FREQUENCY
DIFFICULTY IN CORRECTING DELAY DISTORTION
PROBLEM WITH ADEQUATE LIMITING AND AGC
CCIR HYPOTHETICAL REFERENCE CIRCUIT
A REFERENCE SYSTEM 2500 km (1550 mi) CIRCUIT DIVIDED INTO 9 EQUAL SECTIONS
EACH SECTION IS FURTHER DIVIDED INTO 6 HOPS INTERCONNECTED AT THE BASEBAND FREQUENCY
DESCRIPTION OF EACH SECTION IN THE HYPOTHETICAL MODEL
173 MILES WITH SIX 28.8 MILE-HOPS
ALLOWABLE NOISE PER SECTION IS 833 Pw
NOISE CONTRIBUTION: 6 FEEDER = 150 pW; GROUP DELAY = 100 pW; MOD/DEMOD = 37 pW
ALLOWABLE NOISE/REPEATER = 546/6 = 91 pW