Switched Oscillators and Their Integration Into Helical Antennas

In this paper, the problem of designing switched oscillators at four different frequencies (200, 300, 400, and 500 MHz) has been addressed. These oscillators are quarter-wavelength long coaxial transmission lines with a nitrogen spark gap switch at one end. Two of these switched oscillators at 200 and 500 MHz with a charge voltage of 30 kV have also been fabricated. These two oscillators are modeled using PSpice and their output into a 100 Ω load is estimated and tested by fabricating a 100 Ω transmission line. Use is made of a modified commercial helical antenna with a bandwidth of 400-600 MHz and a switched oscillator has been integrated into this helical antenna. Measurements have been made of the S
₁₁
, the voltage into the antenna, and also the transient fields at two distances. Indeed, starting from electrical power from a 12 V battery, electrical field strengths in excess of 10 kV/m with damped sinusoidal waveforms at 500 MHz (for example) have been demonstrated.