An amplifier with a power gain of 3dB is to be characterized. The test apparatus provides a SNR of 20dB at the input and measures a SNR of 15dB at the output. Find the amplifier's NF.
Specifications for (2), (3), (4) and (5).
A system is comprised of three amplifiers. The following specifications are given:
The SNR at the input to stage 1 is 30dB.
AP1 = 9.0dB, NF1 = 1.8dB
AP2 = 24.0dB, NF2 = 4.0dB
AP3 = 12.0dB, NF3 = 8.0dB
2. Find the system power gain in dB and the system noise ratio using the Friis formula. Hint: to use the Friis formula, all quantities must be expressed as ratios (not in dB).
3. Use the system NR from (2) to find the system noise figure (NF).
4. Use the system NR from (2) to find the final SNR after stage 3 as a ratio and in dB.
5. Suppose the amplifiers are cascaded in reverse order, namely, 3, 2, then 1.
(a) Does the overall system power gain change?
(b) Is this a good idea from a system NR perspective? Why, or why not?