Combined Left- and Right-Handed Tunable Transmission Lines With Tunable Passband and 0 $^{\circ}$ Phase Shift

We combine a right-handed (RH) and a left-handed (LH) nonlinear transmission line (NLTL) to realize a new frequency and phase-tunable bandpass filter (BPF). An RH NLTL is a voltage-controlled low-pass fiter and an LH NLTL is a voltage-controlled high-pass filter, so combining both allows for simultaneous and independent control over the low and high cutoff frequencies of the passband. Also, by using the positive phase propagation of a RH NLTL and the negative phase propagation of an LH NLTL, control over the phase propagation in the passband can be achieved. In the fabricated circuit, the controllable low cutoff frequency is from 480 to 721 MHz and the high cutoff frequency is from 625 to 1005 MHz. Also, we note that whatever the passband is, the phase propagation close to the center frequency is 0<formula formulatype="inline"><tex>$^{\circ}$</tex></formula>.