11.1 Introduction11.2 Electric‐Field Strength: EIT (On Resonant and Stark Shift)11.3 Uncertainties11.4 Detection of AM and FM Modulated Signals11.5 Phase Detection and Phase Modulated Signal Detection11.6 RF Power Measurements11.7 Voltage Measurements11.8 Other Applications: RF Camera, Angle‐of‐Arrival, Waveform Analyzer, Plasma Measurements, and Thermometry11.9 Conclusion and DiscussionReferences