Meaning
Instruments designed to detect and measure local electric fields are necessary for mapping radiation patterns and localized emissions on circuit boards. Technicians use e field probes to locate the specific components or traces that are generating high levels of high frequency radiation. These probes typically consist of small antennas, such as a monopole or dipole, coupled to a high impedance detector or receiver.
Sensor Architecture
Miniature dipole configurations provide the best spatial resolution and field symmetry. These e field probes are often shielded to minimize the influence of magnetic fields during scanning. Design teams select the probe size based on the frequency band of interest and the spatial resolution required.
Smaller probes offer better resolution but are less sensitive to weak signals.
Field Measurement
High frequency electric field measurements must be made without disturbing the original field distribution. Plastic housings and resistive lines are used to prevent the probe from acting as an antenna itself.
Calibration Routine
Annual calibration in a known uniform field ensures the accuracy of the probe’s output. The calibration lab provides a set of correction factors that are loaded into the test software. These factors account for the non-linear response of the internal detector across different frequencies and power levels.
Maintaining this calibration is necessary to ensure the repeatability of near field scans.
