Meaning
Deviations from Ohm’s law occur at a conductor interface when the resistance value changes according to the magnitude of the passing current. This contact resistance non linearity arises primarily from semiconducting films or microscopic constriction points that limit current flow. Typical occurrences involve thin oxide layers that require a specific voltage to break through (fritting).
Such behavior introduces harmonic distortion into signals (particularly in radio frequency connectors) where the output signal is no longer a linear replica of the input.
Voltage Dependence
A nonlinear interface responds to voltage fluctuations by altering its conductive path area. When the potential across a junction increases, the electrical field may cause local breakdown of insulating films.
Localized Heating
Heat generated by high current densities at microscopic contact spots changes the resistivity of the base metal. This contact resistance non linearity worsens as localized melting or softening occurs, which expands the physical contact area and temporarily reduces resistance. The resulting loop creates a variable load that shifts with the signal envelope.
Calculations for power dissipation must account for these fluctuating resistive values to prevent thermal runaway in high power RF modules. Designers avoid these effects by specifying higher normal forces to ensure metallic contact through surface contaminants.
Measurement Criterion
Measurement of the condition involves recording the power of third order products relative to the fundamental frequency. This contact resistance non linearity creates specific frequencies that do not exist in the original input. A perfectly linear contact produces no additional harmonics.
Distorted junctions generate predictable harmonics that interfere with receiver sensitivity.
