Sinusoidal Steady-state Analysis of Transmission Lines Flashcards
steady state
transients have settled
Most RF signals are
Narrowband, their bandwidth is only 1-2% of their center frequency
Fourier analysis allows us to
extend to narrowband to wideband or baseband signals
Propagation constant
γ = α +jβ (1/m)
Attenuation constant
α (Np/m), the sine wave decays with α, measure of the attenuation of the amplitude of the fields in electromagnetic wave propagation
Phase constant
β (rad/m), 2pi/λ, As the wave moves forward, its phase may undergo variations, and this factor that indicates this variation
Attenuation increases with
frequency
Line attenuation
10log[Pin/Pout], 8.686αL (dB). Often quoted in dB/m
Lossless medium attenuation and phase
α = 0 and β = ω√L’C’
Standing wave cause
Counter propagating sine waves with different amplitudes and phases due to the reflection at the load will lead to standing waves on the line
Standing wave maximum
2βz + ∠ΓL = (2n)π
Standing wave minimum
2βz + ∠ΓL = (2n+1)π
VSWR
Voltage standing wave ratio, a real number that tells us how close we are to a match
Return Loss
-20log|ΓL| (dB)
Power delivered to the load
A fraction of the available power will be delivered to the load, the rest will be reflected and turned to heat in the transmission line, unless there is a perfect match
