Switched Oscillators and Their Integration Into Helical Antennas

Abstract

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.

Feed Signal Influence and Potential Performances of a Compact Radiation Source Based on a Helical Antenna

“…In [18] Giri et al describe the problem of designing switched oscillators and their integrations into a helical antenna. This paper is following this track.…”

“…Many papers [16]- [18] describe the principle and realization of a low impedance line damped oscillator to feed a high impedance antenna. In most cases, the quarter wave line is composed of a radial section followed by a coaxial section.…”

“…The oil switch and the radial line of the previous version of the source are replaced by a multichannel annular gas switch [16] [17] associated to a coaxial quarter wave oscillator [18]- [20]. A resonant transformer is used to feed 500 kV high voltage pulse to the coaxial damped oscillator.…”

“…Principle and/or realization of switched oscillators are described in many papers [18]- [20] where the line has a radial section and a coaxial section due to the use of only one switch. Our oscillator is only composed of a coaxial section switched by the multichannel annular gas switch.…”

Eletromagnetic Simulation of Initially Charged Structures With a Discharge Source

“…Institute for Plasma Research, India also employed the Pspice program to simulate a GW pulsed power source for intense electron beam generation [4]. Giri et al used the Pspice program to simulate switched oscillators to develop a HPEM radiator with a helical antenna [5]. Electric circuit simulators such as the Pspice program are helpful for investigating the principle of the overall systems but there is a limit on predicting accurately electromagnetic performances of the ICSWDS.…”