Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 106

Figure (3.11) shows the N‐port network. The power entering the i^th port is given in terms of the forward voltage wave or the forward power variable a_i and the power leaving the i^th port is given in terms of the reflected (backward) voltage wave or the reflected (backward) power variable b_i. A part of the microwave power is reflected at the i^th port itself and remaining power entering the network comes out of all other ports as () or as (). The outcoming power from any port is a linear combination of the transmitted power from all other ports. Using either the voltage variables or the power variables, the incident power and reflected power at various ports are correlated as follows:

(3.1.40)

The incident power at the port is treated as the excitation, and reflected/transmitted power at the port is considered as the response. The network is characterized by the S‐parameters.

Therefore, the matrix elements S_ij relating the excitation ( or a_i) to the response ( or b_i) are described as follows:

Figure 3.11 N‐port network showing power variables (a_i, b_i) in terms of voltage variables .

The S_ij is defined with the help of the matched termination. The matched termination also helps to measure the matrix elements S_ij.