Pulsed ring-down antennas for implementation in a phased array
Belt, David W.
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In recent years, the development of directed energy systems has greatly increased, but a majority of the systems still lack the desired compactness for field application. The pulsed ring-down antenna has become of great interest due to its compact size and peak power on target potential. A pulsed ring-down antenna operates by charging the single element antenna with a high potential source and then closing a switch to develop transient wave reflections on the antenna. Typical CW case analysis does not apply in this case. Since these systems are fairly new in study, it is often difficult to predict the overall performance without experimental evaluation. For this reason, we have constructed a simulation model that allows us to predict the transient behavior of the structure. By utilizing the Comsol RF module transient analysis functions, we are able to characterize various parameters of different antennas, beginning with a dipole pulsed ring-down antenna operating around the 100 MHz range. After examining the simulated results against the experimental results for accuracy, we then moved to more complicated Mesoband antenna structures. The simulation model developed within the COMSOL RF module allows us to examine various influential factors such as material losses, transient switching effects, structure capacitance, switch capacitance, and initial charging losses. With this, we are able to examine methods to improve the results in the far field such as capacitive spark gap loading and other capacitive storage methods. Utilizing the pulsed ring-down antenna model, we are able to give a better characterization of mesoband pulsed ring-down structures for implementation into a specific or multi-purpose phased array system. Several of these structures were then constructed, tested, and characterized based upon far field performance. Once the optimal antenna was determined, a five element phased array was constructed. Initially, the phased array is designed to operate at two different phase angles via delay lines. Future systems may incorporate dynamic phase shifting by other means based upon these initial results. With the tools and initial measurements now available, the design of a pulsed ring-down phased array can easily be completed.