Transmission line model for analysis of microstrip travelling wave antennas with right angled bends

A simple but accurate transmission line model for the analysis of microstrip travelling wave antennas based on microstrip lines and right angle bends is described. Radiated far fields from the antenna are calculated using magnetic current on the antenna sidewalls and electric current on the strip surface. Local reflections from the right angle discontinuity are considered in internal field calculations. An equivalent decay constant to accommodate the radiated power from the antenna is introduced which is iteratively computed to improve impedance and radiation characteristics calculated by the model. Total power lost in the line due to this equivalent decay constant is equal to the total power radiated from the antenna. A rampart line antenna having three unit cells is fabricated in the C band and the results from the model are compared with those from full wave MoM simulations and practical measurement with good agreement. This simple yet accurate model would be valuable in computer aided design for optimal microstrip line based antennas with minimal computational resources.