Broadband True-Time-Delay Microwave Lenses Based on Miniaturized Element Frequency Selective Surfaces
Meng Li, Mudar A. Al-Joumayly, Nader Behdad
IEEE Transactions on Antennas and Propagation
Volume: 61, Issue: 3, March 2013
1166 - 1179
Frequency selective surfaces (FSSs), lenses, periodic structures, phased arrays
We present a new technique for designing low-profile, ultrawideband, true-time-delay (TTD) equivalent microwave lenses. Such a lens is composed of numerous spatial time-delay units (TDUs) distributed over a planar surface. Each spatial TDU is the unit cell of an appropriately designed miniaturized-element frequency selective surface and provides a frequency-independent time delay within the frequency band of interest. Two TTD lens prototypes with focal length to aperture dimension ratios of 1 and 1.6 are designed, fabricated, and experimentally characterized at X-band. The 3-dB gain bandwidths of these lenses are respectively 7.5–11.6 and 7.8–11.5 GHz. Each fabricated lens has an overall thickness of 4.76 mm, which corresponds to, where is the free-space wavelength at the center frequency of operation. Each lens uses spatial TDUs with physical dimensions of 6 6 mm , or . Both lenses have a system
fidelity factor close to 1, when excited with a broadband pulse.
Furthermore, due to their true-time-delay equivalent behavior, the
fabricated lenses do not suffer from chromatic aberration within their operational bands. When used in a beam-scanning antenna system, each lens demonstrates an excellent scanning performance in a field of view of.
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