Gsn Raju Electromagnetic Field Theory 35.pdf
The mathematical model describing the electromagnetic phenomena in this study requires the use of the complete set of Maxwell equations; because at frequencies above about 400 MHz, the steady or quasi steady approximations fail. We have used the COMSOL RF Module Version 5.2. For high frequency models, voltage is not a well-defined variable and it is necessary to use scattering parameters (S), defined in terms of electric fields. Scattering parameters (or S-parameters) are complex, frequency dependent variables describing the transmission and reflection of electromagnetic waves at different ports of a device. S-parameters originate from transmission-line theory and are defined in terms of transmitted and reflected voltage waves.
Gsn Raju Electromagnetic Field Theory 35.pdf
The derivation that follows is typical to analysis of electromagnetic fields using scattering parameters [45]. The equivalent simple diagram of the radar head model is shown 1C. The diagram shows a voltage source feeding into the radar with a source impedance of Z0. If we define and as the square root of the forward and reflected incident electromagnetic waves, we can define the scattering function S11 as, [45], and the input impedance can be express as:(1)