A Novel Group Delay Controller Based on Reflective Tunable Filter

This letter introduces a group delay controller (GDC) based on reflective tunable filter with tunable frequency and tunable group delay. The wideband nonlinear conversion of the reflective low-pass delay network to the reflective bandpass delay network was studied, and the deterioration of tunable group delay response was analyzed. Asymmetric tuned reflective topology with self-coupling coefficients was used to compensate for the flatness of the in-band group delay. As a demonstration, a reflective tunable group delay circuit was designed based on tunable quarter-wavelength microstrip resonator and feeding network with tunable external quality factor (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q_{e}$</tex-math> </inline-formula>). The measurements show that the GDC can be tuned from 8 to 20 ns, with a tunable center frequency from 0.8 to 1 GHz.