Meaning
Power density reduction occurs as an electromagnetic wave propagates through a medium or a component. Signal attenuation is measured in decibels and represents the ratio of the input power to the output power. It is caused by absorption or scattering.
Dielectric Absorption
Cables and connectors introduce a predictable amount of loss based on their length and the frequency of the signal. Loss occurs. In a printed circuit board, the signal attenuation increases with the trace length and the loss tangent of the substrate material.
Designers select high performance laminates.
Path Loss
Wireless communication is affected by the environment between the transmitter and the receiver. Foliage and structural walls contribute to signal attenuation, reducing the effective range of the network. This loss follows an inverse square law in free space, but it becomes more complex in indoor environments where multipath reflections occur.
The absorption by oxygen and water vapor also matters at millimeter wave frequencies. High frequency links suffer most.
Link Margin
Engineers must account for the total loss when calculating the link budget for a connection. If the signal attenuation is too high, the power reaching the receiver falls below the sensitivity threshold, leading to a loss of synchronization. This value determines the maximum distance between a sensor and its gateway.
