射频微波技术知识测试2
Answer to Quiz #1
|1. What is the impedance of free space? |
|b) 120 π (376.991) ohms |
|Impedance is defined as the square root of the ratio of the |
|permeability (mu, μ) to the permittivity (epsilon, ε) - in this case|
|of free space. |
|ε0 = 1/(36 π) * 10-9 F/m |
|μ0 = 4 π * 10-7 H/m |
|z0 = sqrt [μ0 / ε0] = sqrt [4 π * 10-7 * 36 π * 109] = sqrt [144 * |
|102 * π2] = 120 π = 376.991 (377) Ω. |
|2. What happens to the noise figure of a receiver when a 10 dB |
|attenuator is added at the input? |
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