Magic Tee (Hybrid Tee) Port Isolation Properties Consider the following statements about a magic tee: The two collinear arms are isolated from each other. One of the collinear arms is isolated from the E arm. One of the collinear arms is isolated from the H arm. The E and H arms are isolated from each other. Which set of statements is correct?

Introduction / Context:
The magic tee combines E-plane and H-plane tees to form a 4-port microwave junction used for splitting/combining with specific phase characteristics and port isolations. Knowing which ports are isolated is essential for correct network design.

Given Data / Assumptions:

• Ports: two collinear arms and two side arms (E arm and H arm).
• Ideal, lossless, perfectly matched device (Sii = 0).
• Standard port numbering where the side arms correspond to E and H excitations.

Concept / Approach:

In the ideal magic tee, the collinear arms do not couple directly to each other (S12 = 0), giving isolation between them. Further, the E and H arms are isolated (S_EH = 0), so a signal injected into one does not appear at the other. However, each collinear arm couples to both E and H arms with specific phase relations, so no single collinear arm is isolated from either side arm on its own.

Step-by-Step Solution:

Verification / Alternative check:

Standard references show equal-magnitude in-phase (H-arm) or out-of-phase (E-arm) splits to the collinear ports, with isolation between the collinear pair and between the E and H arms.

Why Other Options Are Wrong:

Options that include 2 or 3 assert an isolation that does not exist; energy from E or H arms does reach both collinear arms.

Common Pitfalls:

Confusing “isolation” with “no net output due to phasing”; even when outputs cancel at a combining node, the ports themselves are not isolated unless the S-parameter is zero.

Final Answer:

1 and 4 are correct