Transient response of a square microstrip patch antenna using natural modes

The transient response of a square microstrip patch antenna is investigated using time-domain transmission line equations with the natural modes of the microstrip patch antenna. The computation time is very short once the antenna natural modes are obtained. The required natural modes of the microstrip patch antenna are obtained to good approximation using the finite difference time domain (FDTD) method together with Prony´s method. In order to generate a certain mode, a plane wave is used to excite the microstrip patch antenna with both a frequency near to the natural microstrip patch antenna mode (resonance) frequency and with a spatial distribution approximating the microstrip patch antenna mode current. The transient response of a microstrip patch antenna is studied for a normally incident short damped sinusoidal plane wave, representing a high power microwave pulse, with different frequencies of the incident wave. Comparison is made with a FDTD solution with reasonable agreement.