Dispersive Delay Line With Effective Transmission-Type Operation in Coupled-Line Technology

This letter reports on a new design method for dispersive delay lines in coupled-line technology. Based on the reflective chirped delay line concept, a continuous modulation of the even- and odd-mode characteristic impedances in symmetrical coupled-lines is shown to produce a new structure that presents a flat magnitude response and a linear group-delay variation along the operation frequency band. The use of coupled-lines avoids the need for a circulator giving rise to more practical devices, where the processed signal is redirected to the coupled port instead of being reflected back to the input port, thus providing a valuable effective transmission-type operation. The technique of designing a device is validated for ultra-wideband signal processing applications.