GENERAL DESIGN CRITERIA: ATTENUATION (INSERTION LOSS)
Since conductor loss increases by the square root of frequency, and dielectric loss increases linearly with frequency, dielectric losses become a larger proportion of total attenuation as frequency increases. Higher temperature increases attenuation by increasing the resistance of the conductors and the power factor of the dielectric. (Figure 2) gives a correction factor for attenuation versus ambient temperature.
Figure 2 – Attenuation Temperature
The total attenuation from all sources plus any reflection losses over a specific length is called the insertion loss, expressed in dB per foot or 100 feet. Insertion loss of a network can also be defined as the difference in power arriving at the load with and without the network in the circuit.V To select a cable for a particular application, determine an acceptable attenuation (after temperature correction) at the highest frequency in the system requirements. Then choose the smallest diameter cable meeting the corrected attenuation value from the cable specification.
Figure 3 – Attenuation vs. Frequency
Figure 4 – Attenuation vs. Flexure