A broad-band transmission line model for a rectangular microstrip antenna

A method is developed using the transmission line model to predict the input characteristics of rectangular microstrip antennas over a wide band of frequencies. A series combination of transmission lines is used to represent each transverse magnetic (TM) model. Following a brief summary of the basic transmission line model, the idea of an equivalent length, width, and feed offset are introduced to model each mode. The results predicted by the model compared well with experimental results that assumed varying feed positions. The concept of equivalent length, width, and feed offset was validated by experimental results but shows that the equivalent offset term needs some improvement. The number of modes incorporated in the model depends on the frequency range over which the antenna must be modeled. Using three transmission lines gives good results up to the frequency at which the TM₀₂ mode is excited