RF Soliton Generation in NLTLs using Negative Input Pulse of Fast Rise Times Provided by the Discharge of a Storage Capacitor

摘要

High power soliton generation has been studied for applications in communications systems of small satellite (CubeSats), pulse radars, and military communications, etc. Nonlinear transmission line is a periodic network of capacitors C(V) and inductors L(I), where at least one of the components has a nonlinear behavior. In this paper, a nonlinear capacitive line (NLCL) is implemented and studied, in which the capacitance decreases with the applied voltage. The NLCL was built using commercial ceramic-capacitor based on barium titanate (BT) with 10 nF nominal capacitance and inductors of fixed values at 3.3 μH. A high voltage switch system was projected and built to feed the line to produce a negative input pulse of the order of 1.0 kV with a rise time of less than 100 ns. This is much faster than the pulse rise time reduction factor (AT) of a calculated value of 3.27 μs for the line, which results in soliton generation on the line output. The frequency of generated soliton oscillations reached 4.0 MHz with 300 V of voltage modulation depth (VMD). The obtained experimental results with the conventional system of pulse generation with positive polarity are also given for comparison with those from the negative pulse generation system. It is shown that both systems are able to generate RF oscillations if the pulse rise time satisfies the soliton generation condition, being less than the pulse rise time reduction factor. The performed tests made on single shot condition provided a FFT output spectrum with an output oscillation frequency measured in the range of 3-4 MHz for both systems.