Plain-language answer: Transformer coupling transfers RF energy between windings through magnetic or transmission-line interaction while providing a designed impedance, balance, or isolation function.
Why the real component differs from the ideal
Coupling that is too weak wastes bandwidth and energy; too strong can alter resonance, impedance, and tuning. Parasitics matter at RF.
What to verify
Use the documented winding, core, spacing, phasing, load, and frequency; test loss, balance, temperature, and common-mode behavior.
The common mistake
Judging transformer quality from turns ratio alone.
Component boundary
Use frequency-specific ratings and the exact topology, material, geometry, load, power, duty cycle, and cooling. Begin at low power and stop for heating, odor, arcing, distortion, or unstable measurements.
