Theoretical and experimental study of microwave transmission lines with a phase/frequency relationship following a given variation law

Folded transmission lines were studied with a view to improve the bandwidth of phase shifters of group delay equalizers. The technology used is microwave microelectronics on ceramic substrates and ferrites. The experimental results are compared to an approximate theory and shown to be in fair agreement at least for alumina substrates. The phase shift between variously coupled meanders led to the implementation of phase laws corresponding to a range of practical problems. Phase excursions of plus or minus 5 deg around 180 deg were obtained over one octave in the 2 to 4 GHz range. The implementation on ferrites is shown to require further theoretical work due to the effect of the permeability tensor.