Insertion and attenuation loss measurements
When a device or network is inserted in Ihe transmission line, part Pr of the input signal power Pi is reflected from the input terminal and the remaining part Pi-Pr which actually enters the network is attenuated due to the non-zero loss of the network. The output signal power Po is therefore less than Pi. Therefore, insertion loss is defined by Ihe difference in the power arriving at the terminating load with and without the network in the circuit.
Where, by definition
For perfect matching , Pr =0 and the insertion loss and the attenuation loss become the same. The experimental setup for insertion and attenuation loss measurements are shown below in figure 1 . The relative power levels are measured by using detectors and a VSWR meter. DC1 and DC2 are two identical directional couplers .
Figure 1 : Insertion loss and attenuation loss measurement setup