New Simple CAD Model For Series Stubs On Planar Printed Transmission Lines

A modification of a simple CAD model. that accounts for asymmetry and resonances, for short circuited series stubs in planar transmission lines is presented. The advantages of this model over others available are demonstrated using lowpass filters presented with measured and simulated parameters. This model predicts the presence and shape of spikes in the stopband not predicted by other simple CAD models. The model requires measurements of a sample stub and then can be used to predict the behaviour of similar stubs of varying lengths. A filter is demonstrated which has been designed using this model to remove the unwanted spikes from its stopband.