Reflection Coefficient

Vector Relationship

Magnitudes of the reflected signal are expressed as a value between zero and one, or in decibels as return loss. Because the reflection coefficient is a vector, it contains phase information that describes the displacement of the wave. Smith charts are used to visualize these relationships across a frequency range.

Mismatch Consequence

High levels of reflected energy lead to the formation of standing waves on the transmission line. When the reflection coefficient is high, the power delivered to the antenna is reduced and the transmitter may overheat due to the energy returning to the output stage. Protective circuitry often throttles output power if the mismatch exceeds a safety threshold to prevent permanent hardware damage.

Measurement Setup

Vector network analyzers are the primary tools used to determine the impedance characteristics of a device under test. Calibrating the system ensures that the measured reflection coefficient only accounts for the component and not the connecting cables. Accurate data is needed for the qualification of high speed digital boards.