Correct option is D
Scattering parameters (S-parameters) are preferred over impedance parameters (Z-parameters) for describing waveguide junctions due to the following reasons:
1.
Direct Measurement of S-parameters:
· Scattering parameters are defined in terms of incident and reflected power waves, which can be
directly measured using network analyzers.
· On the other hand, impedance parameters require voltage and current measurements, which are difficult in waveguides since waveguides do not support simple voltage and current definitions like transmission lines.
2.
Waveguides Do Not Support Lumped Impedance Concepts:
· In a waveguide, the electric and magnetic fields are distributed in space, making impedance parameters difficult to define.
· S-parameters provide a more natural way to describe the behavior of electromagnetic waves in waveguides.
3.
Frequency Dependency:
· Both S-parameters and Z-parameters vary with frequency, so
option (a) is incorrect.
· However, impedance parameters vary over an unacceptably wide range, making them impractical for waveguide analysis.
4.
Scattering Matrix Properties:
· The scattering matrix is unitary
only in lossless networks (option b is only partially correct).
5.
Practical Usability in RF and Microwave Circuits:
· S-parameters are widely used in high-frequency applications, such as microwave and RF circuits, since they are convenient for characterizing multi-port networks.
