This paper describes a synthesis method dedicated to the design of frequency-independent phase shifters (PS). This innovative PS structure consists in a transmission line cascaded with a negative group delay (NGD) active circuit so that the absolute constant group delays generated by both of them are identical, but of opposite signs. So, in principle, it exhibits a constant overall phase and a group delay close to zero. Broadband linear positive phase slopes are obtained through use of an NGD

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... tive circuit whose characteristics are recalled prior to the extraction of the PS synthesis relations. The design and simulations of a PS of compact size are reported. The experimental results confirm the expected frequency-independent transmission-phase value of 145°10° with an insertion gain of 22 dB over a 160% relative frequency band. At last, future prospects allowed by the specific properties of this PS are presented.