Abstract
In this communication, a low-profile ultrawide band (UWB) antenna is designed, fabricated, and measured for TV white space devices (TVWSDs). Starting from a simple annular ring, the proposed design procedure is guided by the characteristic mode analysis. First, a closed-form estimation to the resonant frequencies of the first two characteristic modes for the annular ring structure is provided. Then, the annular ring is modified to introduce more characteristic modes resonating within the interested spectrum. To excite these modes and to achieve a wideband antenna covering the whole ultrahigh frequency (UHF) TV spectrum, the feeding structure is also carefully designed and refined. Finally, a prototype is fabricated and measured to verify its UWB performance, and radiation patterns at different frequencies are presented to prove the switching of dominating resonating modes. The analyses and performance evaluation show that the proposed antenna is a strong contender to be used for TVWSDs. Furthermore, thanks to the simplicity of tuning and controlling modal resonant frequencies, this procedure can be flexibly applied to various antenna designs.
Highlights
T V white space (TVWS) refers to the set of vacant frequency bands not occupied by the licensed broadcasting services and are available for unlicensed use
This communication presents a design procedure of a ultra-wide band (UWB) antenna operating over the entire ultra-high frequency (UHF) TV spectrum for TVWS devices (TVWSDs)
Starting from a simple annular ring structure, the characteristic mode analysis (CMA) is used as a powerful tool to provide insights into generating and exciting multiple modes to achieve wideband performance
Summary
T V white space (TVWS) refers to the set of vacant frequency bands not occupied by the licensed broadcasting services and are available for unlicensed use. Following our preliminary work in [15], we consider creating multiple resonating modes using CMA to enhance the bandwidth. In this communication the CMA is firstly performed on an annular ring to find a closed-form estimation calculating resonant frequencies of its two dominant modes, and slots are cut to decrease the resonate frequencies. After having sufficient characteristic modes, the feeding structure is designed to excite them efficiently In this way, by exciting multiple characteristic modes, the proposed structure is optimized to cover the whole UHF TV spectrum. A prototype is fabricated and measured to verify simulation analyses and the measurement results show that the proposed antenna achieves 71% fractional bandwidth
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