Transmission line is a complex parameter and is a function of frequency of operation, relative permittivity of the material, characteristic impedance, length and width of the line, and parameters like R, L, G, C, etc. Procedure to calculate the transmission line for a microstrip antenna is as follows:
1. Calculate the effective dielectric constant.
2. Calculate the characteristics impedance for w/d less than '1' or w/d greater than '1'. The Characteristics impedance should be near to 50 Ohms.
3. Simulate the antenna and look for its Smith chart and S11.
4. If the resonant frequency is at the centre of the Smith chart, then the design is fine. If not, then adjust the positions of the antenna with respect to the transmission line or change the structure of the planar transmission line.
5. Further, a stub can be designed to mitigate the reactive components.