A Method for Improving the Matched Termination of Microstrip Line in FDTD Calculation
When characteristics of microstrip line components are calculated by the FDTD method, a non-reflecting termination of the microstrip line is desired. In this paper, a novel method for making a termination producing a small reflection is proposed. The matched termination is composed of lumped-circuit elements. The frequency range of the analysis is up to 10 GHz. The reflection level of a resistance termination previously proposed increases in the high frequency region. The impedance calculated from the reflection coefficient in the termination shows that the cause of the increase is floating capacitance at the end of the microstrip line. And the other cause is the frequency dispersive characteristic impedance of microstrip line. In order to reduce the effect of the capacitive reactance and the difference between the terminal impedance and the characteristic impedance, a termination using resistance and inductance determined by FDTD and simple circuit calculations is introduced. The reflection coefficient at the proposed termination is 13.5 dB lower than that of the previous resistance termination at 10 GHz.