Compact, tunable large group delay line

In this letter, we present a compact, tunable delay line based on left-handed nonlinear transmission line (LH NLTL). The widely tunable range of the large group delay is achieved by controlling a reverse bias voltage of series varactors in the LH NLTL. The proposed tunable delay line can be made in a very compact form since its size is dominated by the cascaded varactors. Our experiment shows that the fabricated prototype exhibits tunable group delay between 1.2 ns and 2.2 ns at a frequency of 1.42 GHz with good return loss. The circuit size is merely 1.6 cm in length.