Hybrid Tee (Magic-T) with Matched Ports In the ideal hybrid tee shown (all ports matched): if 100 mW is fed into port 1 (an input arm), how much power is reflected back into port 1?

Introduction / Context:
The hybrid tee (magic-T) is a 4-port waveguide component combining an E-plane tee and an H-plane tee. It splits and combines power with specific phase relations and, when properly matched, provides isolation between certain ports.

Given Data / Assumptions:

• All four ports are perfectly matched (no reflections at terminations).
• Port 1 is used as the input (either E-arm or H-arm, depending on the convention of the figure).
• Ideal, lossless device.

Concept / Approach:

In an ideal matched hybrid tee, S11 = 0 at each port, meaning there is no reflection back into the excited port. Power applied to an E- or H-arm splits equally between the two collinear arms (with 180° relative phase for the E-arm and 0° for the H-arm) and does not appear at the isolated complementary arm. Therefore, the power reflected back into the source at the driven port is zero.

Step-by-Step Solution:

Verification / Alternative check:

Laboratory measurements of a well-matched hybrid tee show deep return loss at each port (e.g., > 20–25 dB), approximating S11 ≈ 0, so reflected power is negligible.

Why Other Options Are Wrong:

Any nonzero reflected power implies mismatch or internal loss, contradicting the ideal matched assumption.

Common Pitfalls:

Confusing isolation between E and H arms with return loss; isolation relates to cross-coupling, while return loss concerns reflections at the excited port.

Final Answer:

0