Why short-circuited stubs are preferred to open-circuited stubs in RF/microwave matching? Choose the main reason an open-circuited stub is often avoided compared to a short-circuited stub of the same electrical length.

Introduction:
Single-stub tuning is a classic transmission-line method for impedance matching. Designers often prefer short-circuited stubs over open-circuited ones, particularly at high frequencies where unintended radiation and coupling become significant concerns.

Given Data / Assumptions:

• Lossless/low-loss line; identical Z0 for main line and stub unless otherwise designed.
• Same electrical length for fair comparison.
• Practical implementation with finite grounding and fringing fields.

Concept / Approach:

An open end supports strong fringing electric fields, which can radiate and pick up environmental coupling. A short-circuited end presents a well-defined boundary with minimal radiation and provides a robust RF ground at the end. Both open and short stubs can synthesize the same reactance values, but the shorted stub generally offers better repeatability and lower radiation loss.

Step-by-Step Solution:

Verification / Alternative check:

Near-field scans and EM simulation show higher external fields around open-ended stubs, confirming higher radiation susceptibility.

Why Other Options Are Wrong:

Option A: Fabrication difficulty is not the fundamental reason. Option B: Z0 choice is design-dependent, not an intrinsic limitation of open stubs. Option D: Both open and short stubs can realize a full reactance range. Option E: Irrelevant claim.

Common Pitfalls:

Assuming open stubs cannot realize inductive susceptance; they can, but with higher radiation risk at high frequencies.

Final Answer:

is liable to radiate.