Measuring Polymer Radome Transmission Loss at Millimeter Wave Frequencies
Polymer radome transmission loss at mmWave frequencies depends on dielectric loss tangent and wall thickness precision to maintain regulatory EIRP compliance.
Transmission Loss
Meaning
Electromagnetic energy decreases in strength as it propagates through a cable or the atmosphere. This reduction in signal power called transmission loss is measured in decibels and accounts for both the absorption of energy into materials and the scattering of the wave. It determines the maximum distance a wireless link can operate before the data becomes unreadable.
Conductor Resistance
Current flowing through copper traces encounters a physical opposition that generates heat. This component of transmission loss is dominant at lower frequencies and depends on the cross sectional area of the conductor. As the frequency increases, the skin effect forces the current to the surface of the metal and further increases the effective resistance.
High quality gold or silver plating is often used to minimize this effect in sensitive radio equipment.
Dielectric Absorption
Insulation materials around a wire or the substrate of a circuit board absorb a portion of the electric field. This part of the transmission loss is heavily dependent on the chemistry of the plastic and the frequency of the signal. Molecules in the dielectric vibrate in response to the changing field and convert that motion into thermal energy.
Choosing a material with a low loss tangent is necessary for maintaining signal integrity in high speed digital designs.
Network Planning
Engineers calculate the total budget of a wireless system by subtracting the expected transmission loss from the transmitter power. This calculation ensures that the receiver will have enough signal to maintain a stable connection. Factors like rain, foliage, and the distance between nodes must all be included in the final estimate.