Complete scattering parameter characterisation by FDTD method of Y-junction power dividers with small output angles

The finite difference time-domain method is applied to calculate the complete frequency dependent scattering matrix of microstrip Y-junctions with increasingly narrow angles between their output ports. The results of the junctions´ port isolations are presented. Numerical results obtained compare favourably with experiment and published results over a wide frequency range. These results show that the angle between the output ports significantly influences the matching, transmission and isolation characteristics of the junctions. It is shown how the stability criterion can be used to calculate a suitable size of the computational domain for accurate results. Transient spatial distribution of the electric fields of the Y-junction vividly reveals the complex mechanism of substrate surface-wave generation