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In case the two measurement ports use the same reference impedance, the insertion loss is defined as: [1] [2]= | |. Here is one of the scattering parameters.Insertion loss is the extra loss produced by the introduction of the DUT between the 2 reference planes of the measurement.
Typical transformer insertion loss measurements are taken at 1,000 Hz to optimize the transformer's specifications. [4] Using this method, typical insertion losses are about 1 dB, a 20% power loss. Most of the power in voice-application audio systems is below 400 Hz, meaning that insertion loss at lower frequencies would be greater.
The procedure consists of the following steps: determine the poles of the prescribed insertion-loss function, from that find the complex transmission function, from that find the complex reflection coefficients at the terminating resistors, find the driving point impedance from the short-circuit and open-circuit impedances, [note 13]
The extra loss may be due to intrinsic loss in the DUT and/or mismatch. In case of extra loss the insertion loss is defined to be positive. The negative of insertion loss expressed in decibels is defined as insertion gain and is equal to the scalar logarithmic gain (see: definition above).
C 1 shunt = G 1, L 2 series = G 2, ... or L 1 shunt = G 1, C 1 series = G 2, ... Note that when G 1 is a shunt capacitor or series inductor, G 0 corresponds to the input resistance or conductance, respectively. The same relationship holds for G n+1 and G n. The resulting circuit is a normalized low-pass filter.
The equations above find the impedance and loss for an attenuator with given resistor values. The usual requirement in a design is the other way around – the resistor values for a given impedance and loss are needed. These can be found by transposing and substituting the last two equations above; If = =
The input impedance of an infinite line is equal to the characteristic impedance since the transmitted wave is never reflected back from the end. Equivalently: The characteristic impedance of a line is that impedance which, when terminating an arbitrary length of line at its output, produces an input impedance of equal value. This is so because ...
The pad is designed for a particular load impedance, Z Load, and a particular source impedance, Z s. The impedance seen looking into the input port will be Z S if the output port is terminated by Z Load. The impedance seen looking into the output port will be Z Load if the input port is terminated by Z S.