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DEVELOPMENT OF AN ULTRA-WIDEBAND LOW-PROFILE WIDE SCAN ANGLE PHASED ARRAY ANTENNA
Vo, Henry Hoang

2015, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
Coupling in phased arrays is a major issue. Mutual coupling causes both gain and bandwidth reduction. Such coupling arises from the presence of adjacent elements that produce scattering and losses during low-angle beam steering. The scattering effect is comprised of (1) structural scattering and (2) antenna-mode coupling and associated losses. Losses occur when the coupled energy received by adjacent elements is dissipated at the back-end loads, resulting in lower gain at wide scan angles. In addition, the interference from periodic nature of large arrays or feed networks may produce undesired scattering modes and traveling waves that limit the upper bound of the operational frequency and maximum scan angle in ultra-wideband (UWB) arrays. As a result, current ultra wideband (UWB) array designs typically have limited scanning to no more than 45° from normal.

In this dissertation, we examine the low angle scanning issues. These issues are verified via full-wave simulation. Our studies show that mutual coupling in the H-plane is stronger than in the E-plane, likely due to the dipole element pattern shape.

Another focus of this dissertation is the development of an UWB dual-polarization and low angle beam steering array based on the concept of tightly coupled dipole arrays. For this array, we suppress/minimize mutual coupling by redesigning the antenna element, feed geometry, and array structure. Some key design parameters include (1) the simple feed of tightly-coupled dipoles, (2) array height above ground plane, (3) dielectric superstrate, and (4) parasitic coupling ring. The common mode issue is avoided by retaining the ground plane height to less than λmid/4 and the array unit cell size to 0.45λhigh. The final design is also fabricatable on a low-cost PCB. The PCB uses (1) 0.35 mils thick copper corresponding to a standard ¼ oz. copper lamination, (2) 2 mils coupling slot width and plated-thru vias manufacturable using standard PCB process, and (3) standard Roger RT/Ruroid 5880LZ substrate with dielectric constant of 1.96 and Roger RT/Duroid 5880 superstrate with dielectric constant of 2.2.

An 18x18 prototype array is fabricated and measured to verify the final design. The total array height of the fabricated prototype is 0.122λ at the lowest operating frequency. It is also demonstrated that the fabricated array is capable of scanning down to more than 60° in the E- and H-planes with impedance bandwidth of 2.62:1 subject to VSWR = 2. Good agreement was also observed between simulations and measurements.

Chi-Chih Chen (Advisor)
John Volakis (Committee Member)
Joel Johnson (Committee Member)
96 p.

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Vo, H. (2015). DEVELOPMENT OF AN ULTRA-WIDEBAND LOW-PROFILE WIDE SCAN ANGLE PHASED ARRAY ANTENNA. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Vo, Henry. "DEVELOPMENT OF AN ULTRA-WIDEBAND LOW-PROFILE WIDE SCAN ANGLE PHASED ARRAY ANTENNA." Electronic Thesis or Dissertation. Ohio State University, 2015. OhioLINK Electronic Theses and Dissertations Center. 25 Nov 2017.

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Vo, Henry "DEVELOPMENT OF AN ULTRA-WIDEBAND LOW-PROFILE WIDE SCAN ANGLE PHASED ARRAY ANTENNA." Electronic Thesis or Dissertation. Ohio State University, 2015. https://etd.ohiolink.edu/

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