Overview

The insertion loss (IL) is defined as the reciprocal of the ratio of the power delivered to the load with and without insertion of a device between source and load, and is usually expressed in decibels [1]:

(E.1)

The measured values of the insertion loss depend on the actual values of the generator reflection coefficient ? _G and load reflection coefficient ? _L. This shall be exemplified by comparing the two circuits shown in Figures E.1 and E.2.

Figure E.1: Two-port device inserted between load and generator (network I).

Figure E.2: Source and load connected via an ideal transmission line (direct connection, reference network II).

Figure E.1 shows a two-port device, interconnected between a generator with generator wave b _G and generator reflection coefficient ? _G, and load with the load reflection coefficient ? _L (network I). The device is characterized by the scattering matrix S. ? ₁ is the two-port input reflection coefficient, and ? ₂ the load reflection coefficient. denotes the power which enters port 1, and is absorbed by the load.

Figure E.2(a) illustrates the connection of generator and load via an ideal transmission line with zero input and output eigenreflection and perfect transmission coefficients ( S ₁₂ = S ₂₁ = 1). The network corresponds to a direct connection, as illustrated by Figure E.2(b). Following the definition (E.1), we can write

(E.2)

of network I is calculated as

(E.3)

Regarding the reference network...