Infared Antennas, Phased Array
Phased-array antennas are commonplace in the radiofrequency portion of the electromagnetic spectrum. Exploitation of phasing effects between multiple antennas facilitates a wide range of applications, including synthetic-aperture radar, beam forming, and beam scanning. For the first time, the phased addition of multiple dipole antennas is demonstrated in the infrared, at a wavelength of 10.6 micrometers. Coplanar strip lines are used to interconnect the antennas, preserving the phase of the individual contributions. Several different proof-of-concept experiments are performed, using planar antennas fabricated with direct-write electron-beam lithography. Infrared-frequency currents from two dipole antennas are summed together at a common feedpoint and dissipated in a bolometric load. Angular pattern measurements show that the direction of maximum gain depends on the phase difference between the antennas. As more antennas are added together in phase, beam narrowing is observed in the angular response. Another experiment uses a two-dipole array to directly measure the magnitude of the mutual coherence function, at the plane of the antennas, of a spatially incoherent narrowband source. Measurements are also made of the broadside antenna response comparing air-side and substrate-side situations for a dipole antenna fabricated on a hemispherical immersion lens. In all cases, the measured behavior is confirmed by electromagnetic analysis.
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Doctor of Philosophy (Ph.D.)
College of Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Middlebrook, Christopher, "Infrared Antenna-coupled Phased-array" (2007). Electronic Theses and Dissertations. 3264.