Novel microwave integrated lowpass filters

The procedure is described for synthesising Cauer Cheby̅shev lowpass filters of the third order as rectangular microwave integrated structures. The synthesis procedure is based on a two-mode approximation and leads to structures with very small dimensions compared with the usual realisations of such type of filters. The experimental behaviour is shown to be quite satisfactory, particularly in the passband, where the filters show a better performance than the corresponding lowpass prototypes.