Antenna Systems for Wideband Direction Finding and Spectrum Sensing

Antenna systems for direction finding (DF) and spectrum sensing remain vital to modern engineering; civilian and defense sensing requires wideband systems meeting rigorous requirements across the spectrum. Wideband DF systems can be examined as wide absolute bandwidth or wide relative bandwidth. The challenges at mm-wave frequencies are the large impact of small features and controlling pattern shape over wide absolute (>30GHz) bandwidths. At microwave frequencies the challenge is establishing ripple-free beam shape over wide relative (>3:1) bandwidth. Typical DF at high frequencies uses poorly controlled pattern shape, while at low frequencies allow low efficiencies and strong pattern ripple, reducing accuracy and range. More rigorous goals require analytical evaluation of DF antennas, and pattern and mode control. A theory is developed analyzing DF with ideal cosine, sinc, or gaussian radiation patterns. This theory models many realistic antenna beams, and shows a fundamental link between beam shape and pointing angle, and three DF system parameters: field of view (FOV), minimum FOV gain, and minimum DF function slope. Utilizing this framework, realistic system goals are established, antennas can be evaluated analytically, guiding design for DF. This analysis is validated by design of three antennas. A curved aperture horn is designed for wide absolute bandwidth W-band Sensing, and substantial pattern control over frequency, enabling frequency insensitive DF. Multiple manufactured configurations show agreement with simulation. A dual polarized TEM horn is developed for wide relative bandwidth L to C-band operation, integrated with loop and bowtie antennas to achieve miniaturization through spherical modes engineering. High efficiency, dual polarization, and DF operation are obtained. Measurements show agreement of pattern shape and validate design, but are impacted by modeled and actual absorber loss. A dual polarized LPDA antenna is designed from L to C-band for consistent gain and match. Development includes integrated tapered line matching network. Performance impacts of geometric parameters are discussed. Finally, 3D Printing is investigated for self-supporting, low-loss coaxial lines. A High Q resonator is designed to investigate surface roughness. Wideband filters and diplexers are demonstrated, incorporating novel coaxial junction geometry to compensate for parasitic loading. Manufactured devices achieve significant miniaturization and agreement with simulation

Miniaturization of an UWB Dual-Polarized Antenna

International audienceFor some UWB applications (short range radars,medical imaging), it has been shown that the use of an antennathat supports a dual-polarization can enhance their accuracy.However, the size of classic UWB dual-polarized antennas makestheir integration into small devices difficult. As size becamecrucial, miniaturization techniques have been previously investigatedin an UWB context. In this paper, we aim to provide anelectrically-small UWB antenna with a dual-polarized radiationpattern. A planar miniaturization technique has been investigatedon a dual-polarized sinuous antenna. A size reduction of 32%has been achieved without compromising on either bandwidth orradiation performances