ALLPCB
Many standards require calibration of the test field strength level before testing. Calibration is often performed with CW, that is, an unmodulated continuous wave signal. In that case, a common generic field probe available on the market can be used for calibration and will provide accurate field strength measurements.
When modulation-aware probes are needed
However, in the following cases, the measurement capability for modulated signals must be considered:
- Calibration is required using the same specifically modulated signal as used during the test;
- Calibration for feedback measurements must use the same specifically modulated signal as used during the test.
In these situations, check whether the field probe can accurately measure the field strength of modulated signals by consulting its datasheet for relevant specifications. Using AR field probes as an example, the key specifications are highlighted in yellow: in addition to the probe's frequency range and dynamic range, also consider rise time, sampling rate, and minimum detectable pulse width, as shown in below.
If a field probe lacks these specifications, or if its sampling rate is very low, evaluate whether it is suitable for measuring the field strength of modulated signals.
Electromagnetic compatibility testing is an experimental discipline that must be realizable in practice. Therefore, when standards are developed, their implementability should be taken into account.
