EMC Question of the Week: June 3, 2019

Which of the following N-port network parameters is equal to the voltage reflection coefficient at one of the ports?

1. S₁₁
2. S₁₂
3. Z₁₁
4. Z₁₂

Answer

The correct answer is "a". S-parameters relate the voltage waves traveling in to each port to the voltage wave traveling away from each port. S_ij is determined by driving port j with an incident wave of voltage V_j⁺ and measuring the voltage wave amplitude V_i^- coming out of port i. S_ii is therefore the reflection coefficient looking into port i.

Z-parameters relate the voltage at a port to the current at the same or another port when the currents to all other ports are zero. Both Z-parameters and S-parameters are complex numbers that are functions of frequency.

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