Hybrid Nonlinear Transmission Lines Used for RF Soliton Generation

Nonlinear transmission lines (NLTLs) have been studied for high-power RF generation with good prospects of applications in pulse radars for remote sensing (SARs) and disruption of communications in the battlefield, for instance. In this paper, two 30-section hybrid NLTLs built using nonlinear inductors and capacitors (2.2- and 10-nF barium titanate ceramic capacitors with 10- $\mu \text{H}$ ferrite bead inductors) will be described. For the test, the line is fed by a negative input pump pulse generated by a 1 kV discharge of a 0.75- $\mu \text{F}$ storage capacitor via a fast 50-ns switching system composed by an insulated gate bipolar transistor switch and its gate circuit driver. In the hybrid line tests, using 2.2-nF ceramic capacitors the maximum soliton generation packet obtained on the middle section had a frequency of the order of 33 MHz with voltage modulation depth (VMD) of around 700 V. For every single shot, approximately 10 RF cycles with small damping were noted. With the hybrid line using 10-nF ceramic capacitors the soliton generation obtained on the middle section reached a frequency of the order 10 MHz, and VMD of around 200 V. The main conclusion from this experiment is that hybrid lumped NLTLs may be used to achieve RF in megahertz range with higher VMD compared their counterparts (i.e., capacitive or inductive lines) because of their stronger nonlinearity with the use of both nonlinear elements.