Meaning
A broadband dipole sensor used to measure electromagnetic emissions operates over a frequency range typically spanning thirty to three hundred megahertz. The biconical antenna receives electromagnetic energy during electromagnetic compatibility tests. This equipment allows test laboratories to perform rapid frequency sweeps without pausing to swap antennas.
Structural Geometry
The physical design of this sensor consists of two cone-shaped structures mounted on a central feedpoint to simulate a thick dipole. Structural geometry determines the electrical characteristics of the antenna, providing a lower characteristic impedance than a thin wire dipole. The skeletal cones are often constructed from lightweight aluminum rods to reduce wind resistance and weight during mounting on automated masts.
This open framework maintains structural rigidity while ensuring consistent electrical contact across the frequency range.
Bandwidth Response
Impedance variation across the lower frequency bands necessitates the use of antenna factors to correct the raw voltage readings from the receiver. Bandwidth response curves show that the sensor has a high impedance at very low frequencies, which requires an internal balun to match the fifty-ohm input of the test receiver. Calibrating this mismatch creates a traceable correction table used during emissions testing.
Integration Constraint
Physical size limits the utility of these antennas in confined spaces like small shielded boxes or desktop enclosures. Integration constraint rules require a minimum distance from chamber walls to prevent capacitive coupling from altering the calibration factor.
