In this paper, 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 because its size is dominated by the cascaded varactors. Our experiment shows that the fabricated prototype exhibits tunable group delay between 1.2 and 2.2 ns at a frequency of 1.42 GHz and good return loss. The circuit size is merely 1.6 cm in length.

A very compact and frequency tunable Wilkinson power divider is suggested and demonstrated for the first time. By replacing k/ 4 section lines in a conventional Wilkinson power divider with varactor tunable, lumped-element synthetic transmission lines, dramatical size reduction and frequency tunability has been achieved. The prototype circuit fabricated shows excellent performance. For tunable frequencies from 0.71 to 0.99 GHz, the insertion loss is less than 3.52 dB, whereas the return loss and isolation are greater than 20 dB. Yet, the size of this voltage controllable Wilkinson power divider is only 4 mm by 8 mm, which occupies less than 3% area of original Wilkinson power divider structure.