Antenna Design for High Power Microwave Applications

Abstract

Directed Energy Devices are next generation electronic warfare equipment that are currently deployed in modern armies for the disruption of electronic systems. Unlike conventional jamming techniques that temporarily disrupt communication, the directed energy devices aim to permanently damage the electronics of hostile devices. Among the various types of these devices, High Power Microwaves (HPM) due to their high advantages in surgical effects on the target with lower collateral damage, can be an effective counter measure against autonomous unmanned aerial vehicles & drones. The aim of this thesis is to design a High-Power Microwave Antenna for a Directed Energy Device. Currently, the HPM antennas in use include Vlasov antennas, Parabolic Antennas, Radial Line Helical Array Antennas and Leaky Wave Antennas. The Vlasov Antennas do not exhibit high gain which is the primary requirement of a Directed Energy Device. Parabolic Antennas suffer from breakdown under high power whereas Helical Arrays have fabrication complexities. Leaky Wave Antennas require a large number of elements to achieve a high gain with the condition of keeping phase constant. Moreover, the typically used antenna types have low aperture efficiencies and complex structures. The Slotted Waveguide Antenna is an alternative to the conventional HPM antennas due to significant advantages such as design simplicity, ease of fabrication, high efficiency and excellent pattern shaping. Thus, in this study a Planar Array of Slotted Waveguide Antenna is designed exhibiting a gain of 25.5 dB at boresight with side lobe level of -13.7 dB. The planar array is excited by a feeder waveguide antenna through slot coupling mechanism. The S11 of designed planar array is better than -15 dB. Due to budget and dimension limitations, a linear array of Slotted Waveguide Antenna along with in-house Coaxial to Waveguide adapter achieving a gain of 18.6 dB is fabricated. The fabricated linear array of SWA has a peak gain of 21.1 dB, SLL of -13.7 dB and a 3 dB Beamwidth of approximately 4 degrees has been achieved. Chebyshev tapering is applied to achieve side lobe level better than -16 dB. A simulated Electric field intensity of 15000 V/m has been achieved for 0.5 Watts of input power. Under vacuum condition, the power handling of the proposed antenna is 10.7 MW which makes it suitable for HPM applications.