Question

[Communications Link Problem ]During design of your satellite you discover a readily available antenna that weighs the same as in the original design but has a diameter twice as large. Assuming this size increase is NOT a problem how much can you reduce the transmitter output power from the original design of 50 watts assuming the same data rate, bit error rate, and link margin?

Signal-to-noise power ratio (noise power-N-k7,B where receive system noise temperature): CPG 1 (dimensionless) where PGequivalent isotropic radiated power (EIRP) (4mRA)" = free space loss, carrier wavelength (L.) In terms of above defined quantities EIRP ( GA) 1 (dimensionless) EIRPGA1 (dimensionless) ? ? N NoB Form independent of bandwidth c EIRP G1 (hertz or s) No L, T,)k

Answer 1

Transmitted power P proportional to 1/Diameter^2 P proportional to 1/D^2 D = Diameter of antenna P_1 = 50w, P_2 = ? D_1 = D D_2 = 2D P_1/P_2 = (D_2/D_1)^2 implies 50/P_2 = (2D/D)^2 P-2 = 50/4 = 12.5w reduce to 12.5w trans- mitted power.